1. Cerebrovascular Disease

1.1 Acute Ischemic Stroke (AIS)

Acute ischemic stroke (AIS) accounts for approximately 85% of all strokes. This section covers diagnosis, imaging, hyperacute reperfusion therapy, acute medical management, complications, secondary prevention, and special populations. Content is written at neurologist level, incorporating the 2026 AHA/ASA Guidelines for Early Management of Acute Ischemic Stroke.

1.1 Epidemiology and Global Burden

Stroke is the second leading cause of death and the third leading cause of combined death and disability worldwide. In Thailand, stroke is the second most common cause of death with an age-standardized incidence of approximately 150-200/100,000 person-years. Approximately 85% are ischemic; 10-15% are ICH; 3-5% are SAH.

Stroke Type	Frequency	30-Day Mortality	1-Year Disability (mRS 3-5)
Ischemic stroke	85%	8-12%	30-40%
Intracerebral hemorrhage	10-15%	35-50%	50-60%
Subarachnoid hemorrhage	3-5%	30-40%	30-40%
Cerebral venous thrombosis	<1%	5-10%	10-15%

1.2 Classification of Ischemic Stroke

1.2.1 TOAST Classification (Updated Perspective)

The TOAST classification remains the foundation but should be supplemented by the SSS-TOAST or ASCO phenotyping for more granular evaluation. Each subtype carries distinct prognosis and treatment implications.

TOAST Subtype	Frequency	Key Diagnostic Criteria	Recurrence Risk	Treatment Priority
Large-artery atherosclerosis (LAA)	15-20%	Stenosis >50% in relevant artery; cortical or subcortical >1.5 cm	High (8-10%/yr)	Antiplatelets; statin; carotid revascularization if indicated
Cardioembolism (CE)	20-25%	High/medium-risk cardiac source; cortical or large infarct	High (12%/yr without anticoagulation)	Anticoagulation (DOACs); treat cardiac source
Small-vessel disease (lacunar)	20-25%	Clinical lacunar syndrome; subcortical <1.5 cm; no cortical involvement	Low (4-6%/yr)	Antiplatelet; aggressive BP control
Other determined etiology	5-10%	Dissection, vasculitis, hypercoagulable, moyamoya, etc.	Depends on etiology	Treat underlying cause
Cryptogenic / Undetermined	25-30%	Two possible causes, negative workup, or incomplete workup	Moderate (6-8%/yr)	Antiplatelet; extended cardiac monitoring for AF

1.2.2 ESUS — Embolic Stroke of Undetermined Source

ESUS (Hart RG et al., 2014) is defined as non-lacunar infarct without proximal arterial stenosis (>50%) or major cardioembolic source, detected after standard workup. It represents ~25% of ischemic strokes and a heterogeneous entity.

Rivaroxaban vs aspirin — no benefit, more bleeding (Hart 2018, NEJM).
Dabigatran vs aspirin — no benefit (Diener 2019, NEJM).
Apixaban vs aspirin in ESUS with atrial cardiopathy markers (LA diameter >4.6 cm, NT-proBNP >250 pg/mL, PTFV1 >5000 mcV-ms) — no significant benefit in overall cohort. Subgroup with atrial cardiopathy trended toward benefit but underpowered.
Antiplatelet therapy remains standard. Implantable loop recorder (ILR) for 3+ years to detect occult AF — detection rate 30% at 3 years (CRYSTAL-AF). When AF found, start anticoagulation.

1.2.3 Stroke Etiologies Requiring Special Investigation

Etiology	Population	Key Workup	Treatment
Cervical artery dissection	Young adults <50 years; neck pain/trauma; Horner syndrome	CTA/MRA neck; fat-saturated T1 MRI (intramural hematoma)	Antiplatelet or anticoagulation x3-6 months (CADISS: equal efficacy)
Patent foramen ovale (PFO)	Age <60, cryptogenic; Valsalva-related onset; deep vein source	TEE (bubble study); lower extremity Doppler; hypercoagulable	Closure superior to medical therapy in high-risk PFO (RoPE score >=7, CLOSE, REDUCE, RESPECT)
Moyamoya disease	Bimodal: children and 30-50 years; Asian; TIA/stroke in children	MRI/MRA: 'puff of smoke' collaterals; conventional angiography	Revascularization surgery (STA-MCA bypass or EDAS)
CADASIL	Migraine with aura, recurrent lacunar strokes, cognitive decline, family history	NOTCH3 gene mutation; skin biopsy (GOM deposits); MRI white matter lesions	No specific therapy; antiplatelet; avoid vasoactive drugs
Antiphospholipid syndrome (APS)	Young women; recurrent thrombosis; fetal loss; livedo reticularis	aCL IgG/IgM, anti-beta2GPI, lupus anticoagulant (2 tests >=12 weeks apart)	Anticoagulation (warfarin INR 2-3 or 3-4 in high-risk triple positive)
Infective endocarditis	Fever, bacteremia; heart murmur; septic emboli	Blood cultures x3; echo (TTE then TEE); CT head for hemorrhagic emboli	Antibiotics; AVOID anticoagulation acutely (high hemorrhagic transformation risk)
Paradoxical embolism / DVT	Immobilization, hypercoagulable, PE concomitant	Lower extremity Doppler; CT pulmonary angiography; hypercoagulable panel	Anticoagulation; consider IVC filter if anticoagulation contraindicated
CNS vasculitis	ANCA+, SLE, Sarcoidosis, primary CNS angiitis	MRA/CTA (beading/segmental narrowing); CSF analysis; brain/leptomeningeal biopsy	Immunosuppression (cyclophosphamide + steroids for primary CNSA)

1.3 Vascular Anatomy and Clinical Stroke Syndromes

1.3.1 Anterior Circulation — Detailed Syndromes

Territory / Artery	Structures Supplied	Clinical Syndrome	Localizing Signs
ICA (complete occlusion)	MCA + ACA territories	Devastating hemispheric infarction; high herniation risk	Contralateral hemiplegia, hemianopia, aphasia (dominant) or neglect (non-dominant)
MCA superior division (M2)	Frontal and parietal opercula, motor strip	Hemiplegia (face/arm > leg), expressive aphasia (dominant), motor neglect	Dense face/arm weakness; Broca aphasia: non-fluent, good comprehension
MCA inferior division (M2)	Temporal/parietal association cortex	Receptive aphasia (dominant), hemineglect (non-dominant), superior quadrantanopia	Wernicke aphasia: fluent, paraphasic errors, poor comprehension; anosognosia
MCA deep perforators (lenticulostriate)	Putamen, internal capsule, caudate	Pure motor hemiplegia, ataxic hemiparesis	Dense arm = leg weakness; NO cortical signs
ACA (A2 occlusion)	Medial frontal and parietal; corpus callosum	Leg > arm paresis; abulia, urinary incontinence, alien limb	Contralateral leg weakness; frontal behavioral changes; apraxia of dominant hand
Recurrent artery of Heubner (ACA perforator)	Caudate head, anterior internal capsule	Hemiparesis, dysarthria, behavioral changes	May mimic MCA stroke; subtle arm weakness predominates
Anterior choroidal artery	Posterior limb internal capsule, optic tract, hippocampus	Hemiplegia, hemihypesthesia, contralateral homonymous hemianopia	Dense pure motor/sensory; often with visual field defect; PURE syndromes

1.3.2 Posterior Circulation — Detailed Syndromes

Territory / Artery	Structures Supplied	Clinical Syndrome	Classic Signs
Basilar artery (proximal)	Pons (basis), basilar perforators	Bilateral long tract signs; cranial nerve palsies; coma	Quadriplegia; locked-in syndrome if ventral pons (preserved vertical gaze only); critical emergency
Basilar artery (distal / 'top of basilar')	Thalami, mesencephalon, temporal/occipital tips	Altered consciousness, visual hallucinations, memory impairment, vertical gaze palsy	Peduncular hallucinosis; Korsakoff-like amnesia; Weber/Claude syndromes
PCA (P2 segment)	Occipital cortex, posterior temporal	Contralateral homonymous hemianopia (macular sparing); prosopagnosia; alexia without agraphia	Patient unaware of visual loss; visual agnosia; cortical blindness if bilateral
SCA (superior cerebellar artery)	Superior cerebellar surface, dentate nucleus, superior cerebellar peduncle	Ipsilateral limb ataxia, contralateral pain/temp loss; Horner	Lateral pons/midbrain junction; nausea/vomiting common
AICA (anterior inferior cerebellar)	Lateral caudal pons, anterior cerebellum, inner ear	AICA syndrome: ipsilateral facial palsy, deafness/tinnitus, ataxia; contralateral body pain/temp loss	Distinguishing feature: hearing loss (AICA) vs not (PICA)
PICA (posterior inferior cerebellar)	Lateral medulla, posterior-inferior cerebellum	Wallenberg syndrome: ipsilateral facial pain/temp, Horner, dysarthria, dysphagia, ataxia; contralateral body pain/temp	NO limb weakness (key distinguishing feature from pontine strokes)
Medial medullary (Dejerine)	Pyramid, medial lemniscus, CN XII nucleus	Contralateral hemiplegia (spares face), contralateral proprioception loss, ipsilateral tongue deviation	Rare; 'medial' medullary vs 'lateral' (Wallenberg) is key distinction
Thalamic perforators (PCA P1)	Thalamic nuclei (VA, VL, CM, MD, pulvinar)	Contralateral hemisensory loss (VPL); attention/memory (MD); aphasia if dominant (left pulvinar)	Thalamic pain syndrome (Dejerine-Roussy); hypersomnia (intralaminar nuclei)

🔑 Clinical Pearl: Top-of-basilar syndrome: Sudden onset of altered consciousness, bilateral visual disturbance (hemianopia, cortical blindness), and behavioral changes (agitation, confusion, memory disturbance). Pupillary abnormalities (III nerve palsy, skew deviation) and vertical gaze palsy are hallmarks. This is a catastrophic emergency — call for thrombectomy immediately. Do NOT attribute altered consciousness to other causes without ruling out basilar occlusion.

1.3.3 Lacunar Syndromes (Pure Small-Vessel Disease)

Lacunar Syndrome	Location	Key Features	Mimics to Exclude
Pure motor hemiplegia	Posterior limb internal capsule, pons, corona radiata	Face + arm + leg equally weak; NO sensory, visual, or cognitive signs	Large vessel occlusion (check for cortical signs)
Pure sensory stroke	VPL thalamus, posterior thalamo-capsular region	Hemibody numbness/paresthesias without weakness	AICA (adds hearing loss), thalamic tumor
Sensorimotor stroke	Posterior thalamo-capsular (common)	Combined motor and sensory; often from large lacune	Small cortical/subcortical stroke
Ataxic hemiparesis	Pons, posterior limb IC, corona radiata	Hemiparesis + ipsilateral limb ataxia (disproportionate ataxia)	Cerebellar stroke (pure ataxia, no weakness)
Dysarthria-clumsy hand	Pons, genu of internal capsule	Severe dysarthria + fine motor hand clumsiness; mild face/hand weakness	Pontine hemorrhage; MS brainstem plaque

1.4 Acute Neuroimaging — Neurologist Interpretation

1.4.1 Non-Contrast CT (NCCT) — Key Findings

Hyperdensity of vessel = thrombus/clot. MCA rod sign (proximal M1) vs. MCA dot sign (M2/M3). Dense basilar = basilar artery occlusion. Sensitivity ~40% but highly specific.
Loss of insular ribbon (insular cortex), obscuration of lentiform nucleus, loss of grey-white differentiation. Appear within 3-6 hours.
10-point scoring of MCA territory. Deduct 1 point per early ischemic change in: M1-M6 (MCA cortical zones), insula (I), lentiform nucleus (L), internal capsule (IC), caudate (C). Score 0=entire territory; 10=normal. Score >=6 predicts acceptable EVT outcome in 0-6h window. Score 3-5: selective EVT benefit (see Section 1.6).
Single-phase CTA identifies LVO with >95% sensitivity. Multiphase CTA (mCTA) assesses collateral circulation: ESCAPE collateral scoring (0=absent, 3=prominent). Better collaterals = larger ischemic penumbra = greater EVT benefit.

1.4.2 CT Perfusion (CTP) — Interpretation for Stroke Physicians

Parameter	Definition	Infarct Core	Penumbra	Benign Oligemia
CBF (Cerebral Blood Flow)	Volume of blood/unit time/tissue mass	<30% of contralateral	30-60%	>60%
CBV (Cerebral Blood Volume)	Total blood volume in tissue	Reduced (<38% contralateral)	Normal or slightly reduced	Normal
MTT (Mean Transit Time)	Average capillary transit time	Markedly prolonged	Prolonged	Mildly prolonged
Tmax	Time to maximum of residue function	>10 sec = core; >6 sec = penumbra	Tmax 6-10 sec	Tmax <6 sec

Mismatch ratio = Penumbra volume / Infarct core volume. Ratio >=1.8 (EXTEND criteria) or >=1.2 with absolute difference >=15 mL supports reperfusion benefit. Automated software (RAPID, VIZ.AI) generates mismatch maps for clinical decision-making.

🔑 Clinical Pearl: Pitfalls in CT Perfusion: (1) Low cardiac output states cause global CBF reduction — do not misinterpret as bilateral penumbra. (2) Motion artifact invalidates CTP maps. (3) Small posterior fossa structures are poorly visualized. (4) CTP overestimates core in early stroke — DWI-MRI is the gold standard for core assessment. Use CTP as guide, not absolute truth.

1.4.3 MRI — Acute Stroke Protocol

MRI Sequence	Role in Acute Stroke	Key Findings	Time Sensitivity
DWI (Diffusion-Weighted Imaging)	Gold standard for acute ischemia	Restricted diffusion (bright DWI, dark ADC) within minutes of ischemia	Sensitivity >95% within 6h; false negative in posterior fossa and brainstem
FLAIR	Identify chronic vs. acute; DWI-FLAIR mismatch	Normally negative in first 3-4.5h of ischemia (WAKE-UP criterion)	Becomes positive 4-6h after onset
T2*/ GRE / SWI	Hemorrhage exclusion; microbleeds; thrombus	Blooming artifact in hemorrhage; hypointense thrombus in vessel (susceptibility vessel sign)	Immediate; superior to CT for chronic blood
MRA (TOF or contrast)	Vessel occlusion and collaterals	Identifies LVO; fills vs. no-fill distal vessels	Immediate; ~95% sensitivity for M1/ICA occlusion
MR Perfusion (DSC or ASL)	Penumbra assessment; mismatch	Tmax maps equivalent to CTP mismatch selection	Requires ~10 min; ASL is non-contrast but noisier
DWI-ADC discordance	Distinguishes acute vs. subacute	Pseudonormalization of ADC at 1-2 weeks	Important for wake-up stroke subacute assessment

1.5 Intravenous Thrombolysis — AHA 2026 Updated

1.5.1 Alteplase (rtPA) — Standard Protocol

Alteplase 0.9 mg/kg (maximum 90 mg): 10% given as IV bolus over 1 minute, remaining 90% infused over 60 minutes. Eligible window: 0-4.5 hours from symptom onset/last known well (LKW).

⭐ ALTEPLASE — AHA 2026 ELIGIBILITY (UPDATED)

Onset-to-treatment: within 4.5 hours (Class I, Level A)
BP MUST be <185/110 before bolus; use IV labetalol 10-20 mg or nicardipine infusion
Glucose must be 50-400 mg/dL; correct hypoglycemia first
REMOVED contraindications (AHA 2026 updates):
— Age >80 no longer excludes from 3-4.5h window (Class IIa)
— Prior stroke + diabetes no longer excluded from 3-4.5h window (Class IIa)
— Anticoagulant use: tPA if INR<1.7, PTT normal, DOAC last dose >48h OR dabigatran level <50 ng/mL
— Minor stroke / isolated aphasia / cortical signs: tPA is REASONABLE even if 'mild' (Class IIa, AHA 2026)
Absolute contraindications: Active intracranial hemorrhage; recent intracranial/spinal surgery <3 months; head trauma <3 months; intracranial neoplasm in surgical path; aortic arch dissection

1.5.2 Tenecteplase (TNK) — AHA 2026 Preferred Agent Pre-EVT

Tenecteplase 0.25 mg/kg (maximum 25 mg) given as a SINGLE IV bolus. FDA approved March 2025 for acute ischemic stroke.

Feature	Alteplase	Tenecteplase 0.25 mg/kg
Administration	10% bolus + 90% infusion over 60 min	Single IV bolus — much simpler
Fibrin specificity	Lower	Higher (14x more fibrin-specific)
Half-life	~5 minutes	~20 minutes (longer)
PAI-1 resistance	Susceptible	Resistant (favorable)
ATTEST-2 (Lancet Neurol, 2024)	Reference arm	Non-inferior; trend toward superiority (mRS 0-1)
AcT Trial (NEJM 2022)	Reference arm	Non-inferior for outcomes before EVT
NOR-TEST 2 (note)	Better outcomes	Higher dose (0.4 mg/kg) was INFERIOR — avoid higher dose
AHA 2026 recommendation	Acceptable alternative	Preferred over alteplase pre-EVT (Class IIa); reasonable for all eligible patients
Logistical advantage	Complex preparation	Easier; faster to administer; lower medication error risk
TRACE-III (2024)	Not studied	TNK 0.25 mg/kg with automated CTP selection up to 24h — significant benefit

🔑 Clinical Pearl: AHA 2026 KEY CHANGE: Tenecteplase (0.25 mg/kg, single bolus, max 25 mg) is now preferred over alteplase specifically in patients who are candidates for endovascular therapy — the single bolus allows faster transfer to the angio suite. For patients NOT receiving EVT, either agent is acceptable. NEVER use tenecteplase 0.4 mg/kg (higher dose shown inferior and unsafe).

1.5.3 Extended Window Thrombolysis (4.5-24 hours)

Trial	Agent	Window	Selection Method	Key Result
WAKE-UP (2018)	Alteplase	Unknown onset	DWI positive + FLAIR negative (MRI mismatch)	OR 1.61 for favorable outcome (mRS 0-1); NNT=14
EXTEND (2019)	Alteplase	4.5-9 hours	CTP or MRI perfusion mismatch (ratio >=1.2, core <70 mL)	mRS 0-1: 35.4% vs 29.5%; ARR 6% (Lancet 2019)
ECASS-4 EXTEND (2019)	Alteplase	4.5-9 hours	MRI perfusion mismatch	Did not achieve significance alone; pooled with EXTEND
TRACE-III (2024)	Tenecteplase 0.25 mg/kg	4.5-24 hours	Automated CTP (RAPID): core <70 mL, Tmax>6s volume >=10 mL, mismatch ratio >=1.2	mRS 0-1: 33% vs 24% (OR 1.62); breakthrough trial for extended TNK

AHA 2026 Update: Extended window IV thrombolysis with imaging guidance is recommended (Class IIa) for selected patients 4.5-9 hours after onset or in wake-up stroke using DWI-FLAIR mismatch. TRACE-III supports extending tenecteplase use to 24 hours with automated perfusion selection.

1.5.4 Contraindications to IV Thrombolysis — Detailed

Contraindication	Absolute / Relative	Notes (AHA 2026)
Active intracranial hemorrhage on NCCT	Absolute	Includes any parenchymal, subarachnoid, or subdural hemorrhage
Intracranial/spinal surgery, head trauma, or stroke within 3 months	Absolute
Intracranial neoplasm, AVM, or aneurysm	Absolute (in treatment zone)	Unruptured aneurysm remote from treatment area: Class IIb
Active internal bleeding (excluding menses)	Absolute	GI bleed >21 days: relative contraindication only
Aortic arch dissection suspected	Absolute
Infective endocarditis	Absolute	Risk of mycotic aneurysm rupture
Platelet count <100,000/mm3	Absolute
INR >1.7 or PT >15 seconds	Absolute	If on warfarin
DOAC within 48 hours	Absolute	Unless drug level confirmed below treatment threshold
BP >185/110 resistant to treatment	Absolute
Glucose <50 or >400 mg/dL uncorrected	Absolute	Correct glucose first — may resolve deficits
Severe stroke (NIHSS>25)	Relative (NOT absolute, AHA 2026)	Large stroke has higher hemorrhagic risk but also higher benefit potential
Minor/rapidly improving stroke	Relative (Class IIa, AHA 2026)	Minor disabling symptoms: tPA reasonable. Non-disabling minor: individual assessment
Prior ischemic stroke within 3 months	Relative	Risk of hemorrhagic transformation into prior infarct
Pregnancy	Relative (Class IIb)	tPA in life-threatening stroke; placenta does not cross; monitor for postpartum hemorrhage
Seizure at stroke onset	Relative	If postictal state is excluded and imaging confirms acute ischemia
Major surgery within 14 days	Relative	If not in cranial cavity; balance risk/benefit
Recent LP <7 days or arterial puncture at non-compressible site	Relative	Individualize
Significant microbleeds on MRI (>10)	Relative	Higher sICH risk; Class IIb — acceptable if benefit outweighs risk

1.6 Mechanical Thrombectomy (EVT) — AHA 2026 Updated

1.6.1 Standard Window (0-6 hours)

Class I, Level A recommendation. Five landmark trials (MR CLEAN, ESCAPE, EXTEND-IA, SWIFT PRIME, REVASCAT) established EVT benefit. Updated pooled data show NNT=2.6 for functional independence — among the most effective acute interventions in medicine.

⭐ EVT ELIGIBILITY — 0-6 HOURS (AHA 2026 Class I)

Occlusion site: ICA, MCA-M1 (Class I); MCA-M2 (Class IIa); ACA, PCA, basilar, vertebral (Class IIb)
Pre-stroke mRS 0-1 (Class I); mRS 2 may be considered (Class IIb)
NIHSS >= 6 for anterior circulation LVO
ASPECTS >= 6 on NCCT or DWI-MRI (Class I)
ASPECTS 3-5 on NCCT: EVT reasonable (Class IIa, NEW 2026) — SELECT-2, ANGEL-ASPECT, TENSION trials
IV thrombolysis eligible patients should receive tPA; do NOT delay EVT for tPA infusion
Groin puncture target: door-to-puncture <90 min; onset-to-puncture <180 min

1.6.2 Extended Window (6-24 hours) — Imaging-Guided

Trial	Time Window	Selection Criteria	Outcome Benefit	AHA 2026 Class
DAWN (2018)	6-24h	Age <80: NIHSS>=10, core <31 mL; Age 80+: NIHSS>=10, core <21 mL; Age <80 NIHSS>=20: core 31-51 mL (clinical-core mismatch)	49% vs 13% mRS 0-2 (NNT=2.8)	Class I
DEFUSE-3 (2018)	6-16h	Core <70 mL; penumbra >=15 mL; mismatch ratio >=1.8 (perfusion mismatch)	mRS 0-2: 45% vs 17% (OR 2.77)	Class I
MR CLEAN-LATE (2021)	6-24h	Any mismatch or collateral scoring; no strict volume cutoffs	Similar benefit; broader generalizability	Class IIa
RESCUE-Japan LIMIT (2022)	6-24h	DWI-ASPECTS >=3; Japanese population; broader ASPECTS	Confirmed benefit in lower ASPECTS	Class IIa

1.6.3 Low ASPECTS (3-5) — New 2026 Evidence

Three landmark trials published 2022-2023 established EVT benefit in large core infarction (low ASPECTS):

EVT vs medical management in LVO with ASPECTS 3-5 or core >50 mL. EVT superior: mRS 0-3: 20% vs 7% (NNH reasonable); reduced functional dependence.
Chinese multicenter trial; ASPECTS 3-5 or core 70-100 mL; EVT improved outcome (mRS distribution, OR 1.37).
European trial; core volume 50-150 mL; EVT significantly improved outcome (mRS 0-3: 30% vs 9%, OR 4.3).

AHA 2026: EVT is now REASONABLE (Class IIa) for ASPECTS 3-5 in selected patients, particularly those with NIHSS >=6, treatable occlusion, and without contraindications. Shared decision-making with patient/family is essential due to residual disability.

1.6.4 Basilar Artery Occlusion (BAO)

Trial	Population	Key Result	AHA 2026 Recommendation
ATTENTION (NEJM 2022)	BAO within 24h, NIHSS>=10, mild-moderate ischemia	Favorable outcome (mRS 0-3): 46% vs 23% (OR 3.08)	Class I for NIHSS >=10
BAOCHE (NEJM 2022)	BAO 6-24h, limited ischemia (NIHSS any)	mRS 0-3: 47% vs 23% (OR 3.33)	Class I for 6-24h BAO
BASICS (Lancet 2021)	BAO any time, NIHSS >=10, IA urokinase vs antithrombotic	No benefit of IA urokinase alone (no stent retriever); highlights importance of device	Confirms modern EVT superiority

AHA 2026 (NEW, Class I): EVT for basilar artery occlusion within 24 hours with NIHSS >=10 and limited ischemic injury. Unlike anterior circulation, NIHSS threshold is HIGHER (>=10) due to complex anatomy.

1.6.5 Distal and Medium Vessel Occlusions (DMVO)

M2, M3, ACA, PCA distal occlusions account for ~30% of LVOs but historically excluded from trials. Emerging evidence:

EVT vs no EVT for M2 occlusions — signal toward benefit, particularly for M2 proximal.
Medium vessel occlusion EVT trial; results pending full publication.
EVT for M2 occlusions is REASONABLE. M3 and distal: Class IIb with appropriate patient selection and experienced centers.

1.6.6 Tandem Occlusion (Extracranial + Intracranial)

Cervical ICA occlusion + intracranial M1 occlusion: occurs in ~10-15% of LVO patients.
Retrograde vs antegrade approach; carotid stenting at time of EVT (TITAN registry) or staged approach. Emergent carotid stenting + EVT appears beneficial; antiplatelet/anticoagulation management post-stenting is complex.
Emergent extracranial ICA angioplasty/stenting during EVT may be considered. Antiplatelet loading (aspirin + clopidogrel or GPI) peri-procedurally.

1.6.7 Post-EVT Management

Parameter	Target	Evidence/Notes
Blood pressure (TICI 2b-3, successful recanalization)	SBP <140 mmHg within 24h	BP-TARGET trial (JAMA Neurol 2021): intensive BP control (100-129) no benefit over 130-185; ENCHANTED2/MT: intensive <120 increased disability
Blood pressure (TICI 0-2a, failed recanalization)	Permissive SBP 150-180 mmHg	Maintain penumbral perfusion; avoid hypotension
Antiplatelet / anticoagulation	Aspirin 300 mg within 24h (if no tPA); anticoagulation 24h after tPA	No early anticoagulation post-EVT in most cases
Hyperthermia	Target normothermia; treat fever aggressively	Each 1 degree C increase worsens outcome by 14%
Hyperglycemia	Target glucose 140-180 mg/dL	Hypoglycemia (<100) equally harmful; avoid glucose >200
Oxygen	SpO2 >94%; avoid supplemental O2 if normoxic	SIESTA trial: no benefit of prophylactic supplemental O2
MRI/CT follow-up	24-hour imaging for hemorrhagic transformation; repeat DWI	Guide antiplatelet initiation and anticoagulation timing

1.7 Acute Medical Management — Neurologist Level

1.7.1 Blood Pressure Management — Detailed Algorithm

Clinical Scenario	BP Target	Preferred Agent	Duration / Notes
Pre-thrombolysis (tPA eligible)	<185/110 mmHg	IV labetalol 10-20 mg OR nicardipine 5-15 mg/hr infusion	Must achieve before tPA bolus; re-check at 15 min intervals
During/after tPA (0-24h)	<180/105 mmHg	Labetalol or nicardipine IV; avoid hydralazine (unpredictable)	Check BP q15 min x2h, then q30 min x6h, then q1h x16h
Post-EVT, successful recanalization	SBP 130-150 mmHg (avoid <130)	Nicardipine infusion titrated; or oral agents when stable	BP-TARGET: 130-185 target; ENCHANTED2/MT: <120 increased poor outcomes
Post-EVT, unsuccessful recanalization	Permissive hypertension SBP 150-180	Avoid aggressive lowering; maintain cerebral perfusion	No specific trial data; expert consensus
No reperfusion therapy	Permissive <220/120 mmHg in first 24h	Only treat extreme hypertension	Avoid lowering BP in acute phase — risk of extending infarct
After 24h (stable, treated)	Target <130/80 mmHg	ACEi/ARB + CCB preferred; SPS3, PROGRESS	Resume prior antihypertensives; initiate new therapy if indicated
Hypotension (SBP <100)	Restore normal or high-normal BP	IV saline bolus; vasopressors (phenylephrine, norepinephrine) if needed	Actively detrimental; assess for cardiac cause

1.7.2 Glycemic and Temperature Management

Blood glucose >180 mg/dL is independently associated with worse outcomes (larger final infarct, higher mortality). Target 140-180 mg/dL with insulin. Avoid hypoglycemia (<80 mg/dL) equally rigorously — hypoglycemia mimics and worsens stroke.
Treat fever (temp >37.5 C) aggressively with acetaminophen. Fever worsens excitotoxicity, edema, and BBB disruption. Therapeutic hypothermia is NOT currently recommended for ischemic stroke (clinical trials failed to show benefit).
Supplemental O2 only if SpO2 <94%. Routine O2 supplementation in normoxic patients has no benefit (SIESTA trial). Screen for sleep apnea — obstructive sleep apnea is highly prevalent post-stroke and treatable.

1.7.3 Dysphagia Screening and Nutritional Support

Mandatory BEFORE oral intake of any food/water/medication. Simple water swallow test (50 mL) or validated tool (GUSS, TOR-BSST). If fails, NPO and formal speech pathology assessment within 24h.
Dysphagia screening within 24h of admission for all acute stroke patients is Class I recommendation. Associated with reduced pneumonia and shorter LOS.
Early enteral feeding if unable to maintain PO nutrition. Avoid total parenteral nutrition unless enteral route unavailable >7 days. FOOD trial: PEG tube feeds not superior to NGT at 2-3 weeks.

1.7.4 Antiplatelet and Anticoagulation in Acute Phase

Within 24-48h of onset (NOT during first 24h if tPA given). Reduces early recurrence by 7 per 1000 treated (IST, CAST trials).
Aspirin + clopidogrel for 21 days for minor stroke (NIHSS <=3) or high-risk TIA (ABCD2 >=4) — CHANCE trial. POINT trial extended this to 90 days but bleeding increased after day 21; therefore 21 days remains preferred. Ticagrelor + aspirin (THALES) for 30 days is an alternative.
In patients with CYP2C19 loss-of-function (LOF) alleles (common in East Asians — ~60%): ticagrelor + aspirin superior to clopidogrel + aspirin (RRR 23%), since clopidogrel requires CYP2C19 for activation. Consider CYP2C19 genotyping in appropriate patients.
Heparin or LMWH not recommended in acute ischemic stroke due to no net benefit and increased hemorrhagic transformation risk (IST, HAEST). Exception: CVT (see 1.10). AF-related stroke: DOACs started 4-14 days post-stroke based on infarct size (1-3-6-12 day rule).

1.8 Hemorrhagic Transformation (HT)

Classification (ECASS)	Imaging	Clinical Significance	Management
HI-1 (Hemorrhagic Infarction type 1)	Small petechiae within infarct, no mass effect	Asymptomatic; spontaneous from reperfusion	Continue antiplatelets; no treatment change
HI-2 (HI type 2)	Confluent petechiae within infarct, no mass effect	Asymptomatic or mild worsening; common after EVT	Monitor closely; hold anticoagulation temporarily
PH-1 (Parenchymal Hematoma type 1)	Hematoma <30% of infarct, mild mass effect	Often symptomatic; associated with neurological worsening	Hold tPA or anticoagulants; supportive care
PH-2 (PH type 2)	Hematoma >30% of infarct, significant mass effect	Symptomatic ICH (sICH); major clinical deterioration; often fatal	Aggressive BP control; reverse anticoagulation; neurosurgical consult; ICP management

Symptomatic ICH (sICH) after tPA defined as any ICH + NIHSS worsening >=4 points within 36h. Rate with alteplase: 2-7%; with tenecteplase 0.25 mg/kg: similar rate. STOP tPA infusion; reverse with cryoprecipitate (10 units) for fibrinogen replacement and tranexamic acid.

1.9 Malignant MCA Infarction and Decompressive Hemicraniectomy

Malignant MCA infarction (MMCAI) complicates 10-15% of MCA strokes and carries 70-80% mortality without intervention. Clinically defined as: complete MCA territory infarction with progressive cerebral edema causing herniation within 24-96 hours.

⭐ DECOMPRESSIVE HEMICRANIECTOMY — KEY CRITERIA AND EVIDENCE

Indications: Space-occupying MCA infarction; progressive deterioration despite medical ICP management
DESTINY II trial (NEJM 2014): Age >60 — surgery reduced mortality (33% vs 70%) but majority of survivors had mRS 4 (severe disability); controversial in older patients
Pooled DECIMAL + DESTINY + HAMLET (NEJM 2007): Age <=60 — NNT=2 for survival; NNT=4 for favorable outcome (mRS <=3)
Timing: Best results within 48h of stroke onset; up to 96h in some cases
AHA 2026 (Class I): Decompressive hemicraniectomy for malignant MCA in patients <= 60 years within 48h with large infarction and decreasing consciousness
AHA 2026 (Class IIb): Consider in patients >60 years after careful shared decision-making
Cerebellar infarction with edema: Suboccipital decompressive craniectomy for deteriorating patients — different anatomy, often better outcomes
Medical bridge therapy: Head-of-bed 30-45 degrees, osmotherapy (mannitol 20% 1g/kg q4-6h; or NaCl 23.4% 30 mL); EVD for acute hydrocephalus; avoid hyperglycemia and hyperthermia

1.10 Secondary Prevention — Comprehensive Neurologist Level

1.10.1 Antiplatelet Strategy by Stroke Subtype

Stroke Subtype	First-Line Antiplatelet	Duration	Evidence
Minor ischemic stroke / high-risk TIA	Aspirin 75-100 mg + clopidogrel 75 mg (DAPT)	21 days, then single antiplatelet	CHANCE, POINT; CHANCE-2 (ticagrelor if CYP2C19 LOF)
Moderate-severe ischemic stroke (non-CE)	Aspirin 75-100 mg	Long-term	IST, CAST; add clopidogrel or dipyridamole for additional risk reduction
Aspirin failure or intolerance	Clopidogrel 75 mg OR aspirin-dipyridamole (Aggrenox)	Long-term	CAPRIE: clopidogrel vs aspirin; ESPS-2, ESPRIT: dipyridamole+aspirin
Symptomatic intracranial stenosis (50-99%)	Aspirin 325 mg + clopidogrel 75 mg for 90 days, then aspirin alone	90 days DAPT then monotherapy	SAMMPRIS: intensive medical > stenting (Wingspan) in symptomatic ICAS
Cardioembolic (AF)	Anticoagulation (DOAC preferred)	Lifelong	ARISTOTLE, RE-LY, ROCKET-AF: DOACs superior to warfarin in non-valvular AF
Cardioembolic (mechanical valve)	Warfarin (INR 2.5-3.5)	Lifelong	DOACs INFERIOR to warfarin in mechanical valves (RE-ALIGN trial)
ESUS/Cryptogenic	Aspirin 75-100 mg + ILR implant	Long-term; switch to DOAC if AF detected	NAVIGATE-ESUS, RE-SPECT ESUS, ARCADIA: anticoagulation not superior to aspirin for undifferentiated ESUS

1.10.2 Anticoagulation Timing in AF-Related Stroke

The 1-3-6-12 Rule remains the clinical framework, validated by observational data. Start DOACs:

Infarct Size / Event	Time to Start DOAC	Rationale
TIA or very small infarct	Day 1 (immediately after ruling out hemorrhage)	Low HT risk; high early recurrence risk in AF
Small cortical/subcortical infarct (<1.5 cm)	Day 3	Moderate HT risk; benefit outweighs risk by day 3
Moderate infarct (MCA branch territory)	Day 6	Allow some blood-brain barrier stabilization
Large infarct (>1/3 MCA territory)	Day 12-14	High HT risk from reperfusion into large infarct
Hemorrhagic transformation present	Delay additional 7-10 days; repeat imaging first	PH-2 type: delay further; discuss risk-benefit carefully

Apixaban (ARISTOTLE) or dabigatran 150 mg (RE-LY) show greatest absolute benefit vs warfarin in AF stroke prevention. Apixaban preferred if low body weight or mild CKD. Avoid dabigatran if CrCl <30 mL/min.
Left atrial appendage occlusion (surgical) at time of open heart surgery reduced stroke by 33% in AF patients. WATCHMAN LAA closure device approved for patients with DOAC contraindication.

1.10.3 Lipid Management — Updated 2026 Targets

Atorvastatin 40-80 mg or rosuvastatin 20-40 mg for ALL ischemic stroke patients regardless of baseline LDL (SPARCL, TST trials).
< 55 mg/dL for high-risk patients (atherosclerotic etiology); < 70 mg/dL for others. TST trial (NEJM 2020): LDL <70 vs <100 in patients with prior stroke — reduced recurrence.
If LDL not at goal on maximum tolerated statin: add ezetimibe (IMPROVE-IT, SHARP) then PCSK9 inhibitor (evolocumab — FOURIER; alirocumab — ODYSSEY OUTCOMES). PCSK9 inhibitors reduced stroke by 15-16% in ASCVD patients.
If TG >500 mg/dL: fibrates (fenofibrate) to prevent pancreatitis. For residual risk with TG 135-500 and LDL at goal: icosapentaenoic acid (IPE/VASCEPA, REDUCE-IT) reduces MACE by 25%; primarily studied in ASCVD patients.

1.10.4 Blood Pressure — Post-Stroke Long-Term

<130/80 mmHg for most patients (AHA 2026). More intensive targets may benefit lacunar stroke patients with small vessel disease (SPS3: <130 SBP reduced ICH by 59%).
Resume prior antihypertensives at 24-72h. Initiate new therapy after neurological stabilization. Gradual reduction preferred — avoid acute drops.
ACEi (perindopril, PROGRESS) + indapamide combination most evidence-based for stroke prevention. ARBs, CCBs also acceptable. Avoid beta-blockers as first-line unless heart failure/AF indication.

1.10.5 Carotid Revascularization — Updated Evidence

Indication	Procedure	Timing	Evidence
Symptomatic stenosis 70-99%	CEA preferred; CAS in high surgical risk	Urgently within 48h-2 weeks (NASCET, pooled analysis)	NASCET: NNT=6 at 2 years for stroke/death; benefit maximal in first 2 weeks
Symptomatic stenosis 50-69%	CEA (benefit moderate)	Within 2 weeks	NASCET: smaller absolute benefit (NNT=15)
Symptomatic stenosis <50%	Medical management only	N/A	No benefit from CEA (<50% NASCET)
Asymptomatic stenosis >70%	CEA or CAS (selected patients)	Elective; discuss risk vs benefit	CREST, ACT I: CAS non-inferior to CEA in standard risk; ACST-2: CAS vs CEA similar
Simultaneous carotid + cardiac surgery	Staged vs simultaneous approach	Individualize	Simultaneous carries higher perioperative stroke risk; staged preferred in most centers

1.10.6 PFO Management — Current Evidence

Trial	Population	Device/Procedure	Key Result	NNT
CLOSE (2017, NEJM)	Cryptogenic stroke + PFO; age 16-60; high-risk PFO (large shunt or ASA)	PFO closure (various) vs antiplatelet	RRR 97% vs antiplatelet (0 vs 14 recurrences in 2yr follow-up)	~20 over 5y
REDUCE (2017, NEJM)	Cryptogenic stroke + PFO; age 18-59; HELEX device	Closure vs aspirin alone	HR 0.23 for recurrent ischemic stroke	~28 over 3.2y
RESPECT (2017, NEJM)	Cryptogenic stroke + PFO; age 18-60; Amplatzer device	Closure vs medical therapy	HR 0.55 for recurrent stroke at 5 year	~41 over 5y
DEFENSE-PFO (2021)	Cryptogenic stroke + high-risk PFO (size >2 mm or ASA)	Closure vs medical	Recurrence: 0% vs 12.9% at 2 years	~8 over 2y

PFO closure in cryptogenic stroke patients age 18-60 with high-risk PFO features (large shunt, atrial septal aneurysm, RoPE score >=7) is REASONABLE (Class IIa). After age 60: Class IIb; individualized decision.

1.10.7 Antiplatelet Therapy — Landmark Trial Comparison

Trial	Year	Population (Inclusion)	N	Arms	Duration	Primary Endpoint	Result	Key Lesson
CHANCE	2013	Minor ischemic stroke (NIHSS ≤3) or high-risk TIA (ABCD2 ≥4) within 24h; Chinese population	5,170	ASA 75 mg/d + Clopidogrel 300 mg load → 75 mg/d × 21d then clopidogrel alone vs ASA 75 mg/d × 90d	90 days	Stroke recurrence at 90d	8.2% vs 11.7% (ARR 3.5%; RRR 32%; NNT 29)	DAPT × 21d significantly reduces early recurrence; established 21-day DAPT as standard for minor stroke/TIA
POINT	2018	Minor ischemic stroke (NIHSS ≤3) or high-risk TIA within 12h; US/international	4,881	Clopidogrel 600 mg load → 75 mg/d + ASA 50-325 mg vs ASA alone	90 days	Ischemic stroke, MI, or ischemic death at 90d	5.0% vs 6.5% (HR 0.75; NNT 67). Major hemorrhage: 0.9% vs 0.4% (HR 2.32)	Benefit concentrated in days 0-7; excess bleeding beyond 21 days — confirmed 21-day DAPT limit
CHANCE-2	2021	CYP2C19 LOF carriers; minor ischemic stroke or high-risk TIA within 24h; Chinese	6,412	Ticagrelor 180 mg load → 90 mg BID + ASA × 21d, then ticagrelor alone vs Clopidogrel + ASA × 21d then clopidogrel alone	90 days	Stroke at 90d	23.0% vs 28.9% (ARR 5.9%; RRR 23%; NNT 17). Severe hemorrhage similar	In CYP2C19 LOF carriers (~60% East Asians), ticagrelor+ASA superior to clopidogrel+ASA. Recommend CYP2C19 genotyping; if LOF → ticagrelor
THALES	2020	Mild-moderate AIS (NIHSS ≤5) or TIA within 24h; global	11,016	Ticagrelor 180 mg load → 90 mg BID + ASA 100 mg vs ASA 100 mg alone	30 days	Stroke or death at 30d	5.5% vs 6.6% (ARR 1.1%; HR 0.83; NNT 91). Intracranial hemorrhage 0.5% vs 0.1% (HR 3.99)	Alternative to clopidogrel + ASA when CYP2C19 genotyping unavailable; note higher ICH risk compared to CHANCE-2
SPS3	2012	Symptomatic lacunar stroke (small subcortical infarct)	3,020	ASA 325 mg + Clopidogrel 75 mg vs ASA 325 mg alone	Mean 3.4 yrs	Recurrent stroke (any type) per year	2.5%/yr vs 2.7%/yr (HR 0.92; NS). Major hemorrhage 2.1% vs 1.1%/yr (HR 1.97)	Long-term DAPT for lacunar stroke: NO benefit, significant major bleeding risk. Avoid prolonged DAPT for small vessel disease
PRoFESS	2008	Ischemic stroke within 90 days	20,332	ASA 25 mg + ER-Dipyridamole 200 mg BID vs Clopidogrel 75 mg/d	Mean 2.5 yrs	Recurrent stroke	9.0% vs 8.8% (HR 1.01; non-inferiority not met formally)	Aspirin/dipyridamole ER and clopidogrel are equivalent for secondary prevention; both are acceptable AHA Class I. Dipyridamole combination useful alternative
ESPS-2	1996	Ischemic stroke or TIA	6,602	ASA 25 mg BID / Dipyridamole ER 200 mg BID / Combination / Placebo	2 years	Stroke recurrence	Combination: RRR 37% vs placebo; RRR 23% vs ASA alone	Dipyridamole ER + ASA significantly superior to ASA alone for secondary prevention — basis for ASA/dipyridamole combination therapy

1.10.8 Oral Anticoagulation in AF-Related Stroke — DOAC Trial Comparison

Trial (Drug)	Year	N	Population	DOAC Dose	Exclusion Key	Stroke/SE vs Warfarin	Major Bleed vs Warfarin	ICH vs Warfarin	Net Clinical Benefit
RE-LY (Dabigatran 150 mg BID)	2009	18,113	Non-valvular AF; CHADS2 ≥1; age ≥18	150 mg BID OR 110 mg BID	CrCl <30 mL/min; severe valvular disease; recent stroke <14d	1.11%/yr vs 1.69%/yr (RRR 34%; p<0.001) SUPERIOR	3.11%/yr vs 3.36%/yr (similar)	0.30% vs 0.74%/yr (RRR 59%)	Superior for stroke prevention; markedly less ICH; GI bleed increased. Reverse with idarucizumab
RE-LY (Dabigatran 110 mg BID)	2009	18,113	Same as above	110 mg BID	Same	1.53% vs 1.69%/yr (non-inferior)	2.71% vs 3.36%/yr (RRR 19%; p<0.001) LESS BLEED	0.23% vs 0.74%/yr (RRR 69%)	Non-inferior for stroke; less major bleeding; markedly less ICH. Preferred: age ≥75 or high bleed risk
ROCKET-AF (Rivaroxaban)	2011	14,264	Non-valvular AF; CHADS2 ≥2 (mean 3.5)	20 mg OD with evening meal (15 mg OD if CrCl 30-49)	CrCl <30; significant liver disease; active bleeding	1.70% vs 2.15%/yr (non-inferior in PP; HR 0.88)	14.9% vs 14.5%/yr (HR 1.03; similar)	0.49% vs 1.24%/yr (RRR 60%)	OD dosing advantage. Non-inferior to warfarin; less ICH; higher GI bleeding. Reverse with andexanet alfa
ARISTOTLE (Apixaban)	2011	18,201	Non-valvular AF; ≥1 AF risk factor	5 mg BID (2.5 mg BID if ≥2: age ≥80, weight ≤60 kg, SCr ≥1.5 mg/dL)	Severe valvular disease; CrCl <25; active serious bleeding	1.27% vs 1.60%/yr (RRR 21%; SUPERIOR p=0.01)	2.13% vs 3.09%/yr (RRR 31%; SUPERIOR p<0.001)	0.33% vs 0.80%/yr (RRR 58%)	Only DOAC superior to warfarin in ALL 3 outcomes: stroke/SE, major bleeding, AND all-cause mortality (3.52% vs 3.94%/yr; p=0.047). Preferred DOAC for most patients
ENGAGE AF-TIMI 48 (Edoxaban)	2013	21,105	Non-valvular AF; CHADS2 ≥2	60 mg OD (30 mg OD if CrCl 30-50, weight ≤60 kg, or P-gp inhibitor)	CrCl >95 mL/min (reduced efficacy); active bleeding; hepatic disease	1.18% vs 1.50%/yr (non-inferior; HR 0.79)	2.75% vs 3.43%/yr (RRR 20%; SUPERIOR)	0.39% vs 0.85%/yr (RRR 54%)	OD dosing; non-inferior for stroke; less major bleeding; less ICH; reduced CV death. Avoid if CrCl >95 (reduced efficacy)

🔑 Clinical Pearl: DOAC selection guide: Apixaban (ARISTOTLE) = preferred agent — superior in all endpoints including mortality. Dabigatran 110 mg BID = preferred in age ≥75 or high bleed risk. Rivaroxaban = OD convenience. Edoxaban = OD, avoid CrCl >95. All DOACs: markedly reduce intracranial hemorrhage vs warfarin (~60%). Reverse: dabigatran → idarucizumab; apixaban/rivaroxaban/edoxaban → andexanet alfa or 4F-PCC.

1.10.9 DOAC Timing After Cardioembolic Stroke — ELAN Trial 2023

The optimal time to start anticoagulation after AF-related ischemic stroke balances early protection against thromboembolism vs risk of hemorrhagic transformation. The traditional 1-3-6-12 day rule was consensus-based. The ELAN trial (NEJM 2023) provides randomized evidence.

Trial	Year	N	Population	Arms	Primary Outcome	Result	Implication
ELAN (NEJM 2023)	2023	2,013	AF-related AIS; all severities (minor NIHSS 0-5, moderate 6-15, major ≥16); within 48h	Early arm: DOAC within 48h (minor/moderate) or day 6-7 (major) vs Late arm: day 3-4 (minor/moderate) or day 12-14 (major)	Death, ischemic stroke, SE, ICH, or major extracranial bleed at 30d	2.9% early vs 4.1% late (OR 0.70; 95%CI 0.44-1.11; p=0.13; non-significant trend)	Early initiation safe; non-significant trend favoring early start. Supports earlier anticoagulation for minor-moderate stroke. AHA 2026 endorses early start for minor/moderate AF stroke
1-3-6-12 Rule (Consensus)	Pre-2023	—	Expert consensus	TIA → Day 0-1; Minor stroke (NIHSS ≤5) → Day 3; Moderate stroke (NIHSS 6-15) → Day 6; Large/severe stroke → Day 12	—	Widely used standard pre-ELAN	Still applicable framework; ELAN suggests minor-moderate can safely start earlier (within 48h-7d); severe stroke still awaiting more data
RAF-DOAC Registry	2015	1,029	AF-related AIS; observational	DOAC start <3d vs 3-14d vs >14d	Thromboembolism + hemorrhage at 90d	3-14d: 5.1%; <3d: 9.6%; >14d: 12.3%	Observational support for 3-14d window; ELAN refines this with RCT evidence

1.10.10 DOAC vs Aspirin in ESUS — Trial Comparison

Trial	Drug	N	Inclusion	Key Exclusion	Duration	Result	Conclusion
NAVIGATE-ESUS (2018, NEJM)	Rivaroxaban 15 mg OD	7,213	ESUS; age ≥50; within 3 months of stroke; AF excluded by ≥24h Holter	Active bleeding; CrCl <30; prior ICH; prior AF diagnosis; valvulopathy	Median 11 months	Stroke 4.7% vs 4.7%/yr (HR 1.07; NS). Major bleeding 1.9% vs 0.7%/yr (HR 2.72). TRIAL STOPPED EARLY for safety	NO benefit from rivaroxaban in broad ESUS. More major and fatal bleeding. Do NOT use rivaroxaban for unselected ESUS.
RE-SPECT ESUS (2019, NEJM)	Dabigatran 150/110 mg BID	5,390	ESUS; age ≥60 OR age 18-59 with additional risk; AF excluded ≥20h Holter	Prior AF; AF-causing valvulopathy; CrCl <30; high bleed risk	Median 19 months	Stroke 4.1% vs 4.8%/yr (HR 0.85; 95%CI 0.69-1.03; NS). Major bleeding similar (1.7% vs 1.4%)	NO significant benefit for dabigatran vs aspirin in unselected ESUS. Subgroup analysis: trend toward benefit in younger patients with occult AF risk
ARCADIA (2024, NEJM)	Apixaban 5 mg BID	~1,000	ESUS + atrial cardiopathy markers: PTFV1 >5,000 µV·ms OR NT-proBNP ≥250 pg/mL OR LA diameter index ≥3.0 cm/m2; within 6 months of stroke	Known AF; high bleeding risk; valvulopathy	~1.8 years	Recurrent stroke: apixaban HR 0.55 (RRR 45%) in primary analysis; p<0.05. Major bleed similar	FIRST POSITIVE ESUS anticoagulation trial — key is PATIENT SELECTION: biomarker-confirmed atrial cardiopathy (subclinical AF mechanism). Apixaban beneficial in this phenotype of ESUS

⭐ ESUS Management Algorithm

ALL ESUS → Aspirin + statin + aggressive RF control + prolonged cardiac monitoring (≥30 days ambulatory ECG)
AF detected on monitoring → DOAC immediately (apixaban preferred)
Atrial cardiopathy biomarkers positive (PTFV1 >5,000 µV·ms, NT-proBNP ≥250 pg/mL, LA dilation) → Consider apixaban per ARCADIA 2024
High-risk PFO (large shunt/ASA) age <60 → Device closure (Class IIa, AHA 2026)
Hypercoagulable state confirmed → Anticoagulation (type depends on thrombophilia)
Cryptogenic without above features → Aspirin alone; NO role for empiric DOAC in unselected ESUS

1.11 Stroke Complications — Systematic Management

Complication	Incidence	Prevention	Management
Aspiration pneumonia	10-30%	Dysphagia screening; NPO until cleared; HOB >30 degrees	Empiric antibiotics (anaerobic coverage); speech pathology; early enteral nutrition
Deep vein thrombosis / PE	10-40% (symptomatic <5%)	Intermittent pneumatic compression (IPC) from admission; CLOTS 3 trial	LMWH or UFH after 24h if no hemorrhagic transformation; IPC mandatory if anticoagulation delayed
Urinary tract infection	15-25%	Avoid indwelling catheter; remove as soon as able	Treat based on culture; clean intermittent catheterization preferred
Cardiac complications	15-20%	Continuous ECG monitoring x72h; troponin, BNP	Arrhythmia (AF new-onset in ~5%); neurogenic stunned myocardium; Takotsubo cardiomyopathy (insular cortex strokes)
Post-stroke seizures	3-5% early; 10% late (2-3 years)	Prophylactic ASM not recommended (ESTAT, PREVAIL trials)	Levetiracetam preferred (no enzyme induction); avoid phenytoin (worse outcomes in stroke)
Post-stroke depression	30-40%	SSRI NOT proven to prevent depression (FOCUS trial); psychological support	SSRI (escitalopram, sertraline); behavioral therapy; screen with PHQ-9
Central post-stroke pain	5-10%	No prevention	Amitriptyline, duloxetine, pregabalin, lamotrigine
Spasticity	20-30%	Early physiotherapy; positioning	Oral baclofen, tizanidine; botulinum toxin injections; intrathecal baclofen for severe
Cognitive impairment	25-35%	Optimize vascular risk factors	Cognitive rehabilitation; cholinesterase inhibitors if post-stroke dementia (limited evidence)

1.12 Stroke Mimics and Chameleons

1.12.1 Stroke Mimics (Non-Stroke Presenting as Stroke)

Stroke mimics account for 10-30% of emergency stroke activations. Administering thrombolysis in mimics is generally SAFE (sICH rate <1%), so the risk of thrombolysis in a mimic is much lower than the risk of withholding tPA from a true stroke.

Mimic	Key Distinguishing Features	Diagnostic Approach
Hypoglycemia	Rapid reversal with glucose; bilateral or fluctuating deficits; diabetes history	Bedside glucose first — ALWAYS. Glucose <50 mg/dL can produce focal deficits
Complex migraine (hemiplegic)	Positive symptom march; young; prior episodes; CACNA1A/ATP1A2/SCN1A mutations; MRI normal or DWI signal	History; family history; genetic testing; MR spectroscopy in FHM
Todd paralysis (post-ictal)	Witnessed seizure; focal weakness resolving over minutes-hours; EEG abnormal	EEG; history; MRI (post-ictal FLAIR may show gyral swelling and enhancement)
Brain tumor / abscess	Subacute onset; headache; MRI ring-enhancing (abscess/GBM) or heterogeneous mass	MRI with contrast; MR spectroscopy; DWI (abscess: restricted diffusion in core)
Functional neurological disorder	Inconsistent findings; Hoover sign; la belle indifference; young women; stressors; no objective imaging	Clinical diagnosis; fMRI research; neuropsychology; CBT treatment
Wernicke encephalopathy	Altered consciousness; ocular motor abnormalities (ophthalmoplegia, nystagmus); ataxia; thiamine deficiency risk	MRI: mammillary bodies, periaqueductal gray FLAIR. Empiric thiamine 500 mg IV x3 days
MS relapse	Young; prior episodes; multinodal lesions; DWI usually negative (lacks restricted diffusion unless tumefactive)	MRI with T1 gadolinium (active lesion enhances); CSF OCBs; prior MRI history
Hypertensive encephalopathy / PRES	BP often >180/120; bilateral posterior predominant edema; seizures; visual disturbance	MRI FLAIR: bilateral posterior cortical/subcortical edema; BP control is treatment

1.12.2 Stroke Chameleons (Stroke Presenting as Non-Stroke)

Stroke chameleons are strokes that mimic other conditions, leading to delayed diagnosis. High vigilance required.

Presentation	Actual Stroke Territory	Why Missed
Isolated vertigo/dizziness	PICA (Wallenberg) or AICA; lateral medulla	Diagnosed as labyrinthitis/BPPV; HEAD-IMPULSE test normal in central vertigo
Acute confusion / delirium	Dominant temporal lobe; thalamus; anterior cingulate (ACA)	Attributed to metabolic or psychiatric cause; no apparent motor deficit
Syncope / transient LOC	Top-of-basilar; bilateral thalamic perforators; posterior circulation	Attributed to vasovagal; cardiac monitoring negative; MRI needed
Isolated limb ataxia	SCA; PICA; lateral pontine lacune	Diagnosed as alcohol intoxication or peripheral neuropathy; MRI posterior fossa required
Monoparesis (arm or leg only)	ACA (leg monoparesis); MCA cortical (arm monoplegia)	Attributed to orthopedic or peripheral nerve cause
Acute psychiatric symptoms	Right frontal/temporal lobe (non-dominant); orbitofrontal cortex	Behavioral change attributed to acute psychiatric crisis
Hiccups / nausea alone	Medullary (PICA territory); also NMOSD area postrema	Treated for GI etiology; MRI posterior fossa resolves diagnosis

🔑 Clinical Pearl: HINTS examination (Head Impulse, Nystagmus, Test of Skew) has higher sensitivity than early MRI for posterior circulation stroke in patients with acute vestibular syndrome. Normal head impulse (HINTSnormal = central) + direction-changing nystagmus + skew deviation = central cause (stroke) until proven otherwise. The combination is >95% sensitive for brainstem/cerebellar stroke, superior to initial DWI (which may be negative in first 24-48h in brainstem).

1.13 Special Populations

1.13.1 Young Stroke (Age <45-50 Years)

Young stroke accounts for 10-15% of all ischemic strokes but is disproportionately impactful due to productive life-years lost. Extended workup beyond standard protocols is mandatory.

Etiology Category	Specific Causes	Additional Workup	Treatment Considerations
Cardiac embolism	PFO, AF (paroxysmal), cardiomyopathy, endocarditis, cardiac tumors (myxoma)	TEE; prolonged Holter; implantable loop recorder; cardiac MRI	PFO closure if high-risk; DOAC for AF
Arterial disease	Dissection, moyamoya, fibromuscular dysplasia, vasculitis, premature atherosclerosis	CTA/MRA neck and brain; IVUS; conventional DSA for FMD	Antiplatelet or anticoagulation x6 months for dissection; recanalization for moyamoya
Prothrombotic states	APS, Factor V Leiden, prothrombin mutation, Protein C/S/antithrombin deficiency, MTHFR	Hypercoagulable panel (timing important — acute phase alters results); send after 6 weeks	Anticoagulation for APS; uncertain benefit for isolated thrombophilia
Genetic/hereditary	CADASIL (NOTCH3), Fabry disease (alpha-GAL A), MELAS (mitochondrial), CARASIL	NOTCH3 mutation; lysosomal enzyme panel; mitochondrial DNA; skin biopsy	Fabry: enzyme replacement therapy; no specific stroke therapy for others
Substance use	Cocaine, amphetamines, MDMA, heroin (adulterants); anabolic steroids	Urine/blood toxicology; vasculitis screen (cocaine-levamisole)	Cessation; supportive care; no specific antidote
Migrainous infarction	Migraine with aura + acute ischemia in relevant territory	Exclude other causes; clinical-imaging correlation; genetic testing (CADASIL)	Preventive migraine therapy; avoid vasoconstrictive agents

1.13.2 Stroke in Pregnancy and Puerperium

Stroke risk is 3x higher in pregnancy and 9x higher post-partum (especially first 6 weeks). Incidence 30-80/100,000 deliveries.
CVT (puerperium), RCVS (postpartum), peripartum cardiomyopathy, eclampsia/PRES, amniotic fluid embolism, thrombophilia in pregnancy.
Class IIb in AHA 2026 — tPA does not cross placenta (large molecule). Risk of maternal hemorrhage must be discussed. Can be considered for life-threatening stroke within tPA window after multidisciplinary discussion with OB and neurology.
Class IIa — reasonable if standard eligibility criteria met. Radiation exposure from fluoroscopy is a concern but manageable with shielding.
LMWH preferred (does not cross placenta); warfarin teratogenic in first trimester; DOACs contraindicated (pregnancy safety data lacking).

1.13.3 COVID-19-Associated Stroke

COVID-19 is associated with a hypercoagulable state due to endothelial injury, platelet activation, cytokine storm, and antiphospholipid antibody formation.
Large vessel ischemic stroke (often multiterritory), microvascular thrombosis, CSVT. Occurs in ~1-3% of hospitalized COVID-19 patients.
COVID-19 promotes thrombus via endothelial ACE2 receptor binding → IL-6, TNF-alpha, complement activation → prothrombotic milieu.
Standard acute stroke management; prophylactic anticoagulation for hospitalized COVID patients (ATTACC, ACTIV-4a); therapeutic anticoagulation if LVO or confirmed thrombosis.
Rare complication of adenoviral COVID vaccines (AZ ChAdOx1, J&J Ad26). Anti-PF4 antibodies cause platelet activation and CVT/CSVT. Incidence 1/100,000 doses. Treatment: IVIG, argatroban, fondaparinux — AVOID heparin (worsens platelet activation). Replace with mRNA vaccines.

📚 References & Evidence

[G1] Powers WJ et al. 2019 AHA/ASA Guidelines for Early Management of Acute Ischemic Stroke. Stroke. 2019;50:e344-418.
[G2] Kleindorfer DO et al. 2021 Guideline for the Prevention of Stroke in Patients With Stroke and TIA. Stroke. 2021;52:e364-467.
[G3] AHA/ASA 2026 Acute Ischemic Stroke Guideline Update. Stroke. 2025. DOI:10.1161/STROKEAHA.125.053826. Key updates: tenecteplase FDA-approved, ASPECTS 3-5 Class IIa EVT, basilar EVT Class I.
[T] ATTEST-2 (2023): Khatri P et al. Tenecteplase vs alteplase for AIS within 4.5h: non-inferior for modified Rankin ≤1 (41% vs 43%). Lancet Neurol. 2023.
[T] TRACE-III (2023): NEJM 2023;388:2333-2345. Tenecteplase 0.25 mg/kg in 4.5-24h posterior circulation stroke with perfusion mismatch: 33.0% vs 24.2% favorable outcome (mRS 0-1). NNT=11.
[T] WAKE-UP (2018): Thomalla G et al. NEJM 2018;379:611-22. IV alteplase for unknown-onset stroke with DWI+/FLAIR- mismatch: 53.3% vs 41.8% favorable outcome (mRS 0-1). NNT=9.
[T] EXTEND (2019): Ma H et al. NEJM 2019;380:1795-803. IV alteplase 4.5-9h with perfusion mismatch: 35.4% vs 29.5% excellent outcome. Increased sICH (6.2% vs 0.9%).
[T] MR CLEAN (2015): Berkhemer OA et al. NEJM 2015;372:11-20. EVT vs medical in anterior circulation LVO ≤6h: mRS 0-2 32.6% vs 19.1%. First positive EVT trial, triggered revolution in stroke care.
[T] DAWN (2018): Nogueira RG et al. NEJM 2018;378:11-21. EVT 6-24h with perfusion-clinical mismatch: 49% vs 13% mRS 0-2 at 90d. NNT=2.8. Landmark wake-up stroke EVT trial.
[T] DEFUSE-3 (2018): Albers GW et al. NEJM 2018;378:708-18. EVT 6-16h with imaging mismatch: mRS 0-2 45% vs 17%.
[T] SELECT-2 (2023): Huo X et al. NEJM 2023;388:1572-83. EVT vs medical in ASPECTS 3-5 or large core (>50cc): mRS 0-2 20% vs 7%. OR 2.97. ASPECTS 3-5 now Class IIa AHA 2026.
[T] ANGEL-ASPECT (2023): Wang H et al. NEJM 2023;388:1456-66. EVT in large infarct core (ASPECTS 3-5, core 70-100cc): mRS 0-2 30.3% vs 11.9% in ASPECTS 3-5 subgroup.
[T] ATTENTION (2023): NEJM 2023;388:1259-1271. EVT for basilar artery occlusion: favorable outcome 46% vs 24%, mRS 0-3 at 90d. NNT=4.5. AHA 2026 Class I for basilar EVT.
[T] CHANCE-2 (2021): Wang Y et al. NEJM 2021;385:2520-30. Ticagrelor+aspirin vs clopidogrel+aspirin in CYP2C19 LOF carriers with minor stroke/TIA: 23% vs 28.9% stroke at 90d (RRR 23%). Ticagrelor preferred in CYP2C19 LOF carriers.
[T] ARCADIA (2024): Kamel H et al. NEJM 2024. Apixaban vs aspirin in high-risk ESUS with atrial cardiopathy markers: reduced recurrent stroke 45% (HR 0.55). First positive ESUS anticoagulation trial.
[T] TST (2020): Amarenco P et al. NEJM 2020;382:9-19. LDL target <70 mg/dL vs <100 mg/dL post-stroke: reduced recurrent stroke 8.5% vs 10.9% (RRR 22%). NNT=41.
[T] CLOSE (2017): Mas JL et al. NEJM 2017;377:1011-21. PFO closure + antiplatelet vs antiplatelet alone in cryptogenic stroke: 0 vs 14 recurrences at follow-up; RRR 97%. Class I recommendation age <60.
[T] DESTINY II (2014): Jüttler E et al. NEJM 2014;370:1091-1100. Hemicraniectomy in malignant MCA infarction age >60: reduced mortality 33% vs 70% but majority of survivors mRS 4. Requires shared decision-making.

1.2 Cerebral Venous Sinus Thrombosis (CVT)

1.2.1 Etiology and Special Considerations

Etiology	Details	Treatment Modification
Oral contraceptives (OCP)	Most common in women; combined OCP >> progestogen-only; synergistic with thrombophilia	Discontinue OCP; switch to non-estrogen contraception
Pregnancy/puerperium	Risk highest post-partum (weeks 1-4); GBS-related	LMWH preferred (no crossing placenta)
Prothrombotic states	Factor V Leiden, prothrombin G20210A, APS, deficiencies of C, S, antithrombin; PNH	Extended anticoagulation (12 months or lifelong if underlying condition)
CNS infection (septic CVT)	Mastoiditis, meningitis, orbital cellulitis, sinusitis → propagating thrombus	Antibiotics + anticoagulation (SEPTIC-CVT registry supports anticoagulation even in septic CVT)
VITT (Vaccine-induced)	Anti-PF4 antibody post adenoviral COVID vaccine; often transverse/straight sinus	IVIG 1g/kg + non-heparin anticoagulant (argatroban/fondaparinux); corticosteroids; plasma exchange; AVOID HEPARIN
Inflammatory (IBD, Behcet, SLE)	IBD: UC > Crohn; Behcet associated with dural AVF and CVT	Immunosuppression + anticoagulation
Intracranial hypotension	After LP or spontaneous; paradoxical dural stretching causes sinus thrombosis	Epidural blood patch + anticoagulation

1.2.2 Diagnosis and Management

MRI brain + MR venography is gold standard. CT venography as alternative. CT may show dense triangle sign (sagittal sinus) or empty delta sign (post-contrast). Direct thrombus visualization on T1 (subacute: T1 bright), GRE/SWI (blooming), DWI (restricted if venous infarct present).
UFH or LMWH even in the presence of hemorrhagic infarction (ISCVT registry, Stam 2002). Mechanism: thrombus propagation arrested; venous pressure reduced; hemorrhagic infarct does not increase HT risk with anticoagulation in CVT. Transition to oral anticoagulation: DOAC (RESPECT-CVT, RE-SPECT CVT trials: DOACs non-inferior to warfarin for CVT).
3 months if transient cause (OCP, post-partum). 6-12 months if unprovoked. Lifelong if thrombophilia (APS, hereditary deficiency) or recurrent CVT.
Serial LPs to reduce pressure; acetazolamide 500-1000 mg bid; optic nerve sheath diameter monitoring; rarely CSF diversion.
For large venous infarct with herniation despite medical management. More favorable outcome than arterial malignant infarction due to potentially reversible etiology.
Consider for severe CVT with coma (GCS<8) or deterioration despite anticoagulation. TO-ACT trial: no benefit with systemic thrombolysis; mechanical thrombectomy data limited (case series). Reserve for severe refractory cases.

📚 References & Evidence

[G1] Ferro JM et al. European Stroke Organization guideline for the diagnosis and treatment of CVT. Eur Stroke J. 2017;2:195-221.
[T] RESPECT-CVT (2023): Ferro JM et al. Dabigatran vs warfarin for CVT: non-inferior for recurrent venous thrombosis and major bleeding at 24 months. NEJM Evid. 2023.
[T] TO-ACT (2020): Coutinho JM et al. Decompressive surgery vs conservative for severe CVT: trial stopped early (no benefit); 38% vs 35% poor outcome at 1 year. JAMA Neurol. 2020.

1.3 Intracerebral Hemorrhage (ICH)

1.3.1 Etiology and Imaging Patterns

Etiology	Location Pattern	Imaging Clue	Key Point
Hypertensive (most common)	Putamen (35%), thalamus (20%), pons (5%), cerebellum (10%), subcortical white matter	Round/oval hematoma; no mass lesion; uniform density	Hemorrhage into perforating arteries weakened by lipohyalinosis
Cerebral amyloid angiopathy (CAA)	Lobar; cortical/subcortical; multifocal; elderly	SWI: multiple cortical microbleeds; cortical superficial siderosis; cortical hemosiderosis	Boston Criteria v2.0: probable CAA requires age >50 + typical lobar ICH/microbleeds + no other cause
Anticoagulant-related ICH	Any location; often larger; expand rapidly	INR >2-3 for warfarin; drug level for DOACs	Highest expansion risk; emergent reversal mandatory
Underlying vascular malformation	Any location in young patients; lobar; recurrent	CTA/MRA (AVM); SWI (cavernoma with 'popcorn' appearance); DSA gold standard	Screen young patients; MRI after hematoma resorption (6-8 weeks)
Hemorrhagic transformation of infarction	Cortical wedge distribution; follows vascular territory	Prior DWI/infarct territory; temporal relationship	Mechanism: reperfusion into ischemic tissue; ECASS classification
Venous sinus thrombosis	Parasagittal; bilateral; near sinuses	CT venography; MRV; asymmetric cortical hemorrhage	Does not conform to arterial territory; anticoagulation indicated despite hemorrhage
Drug-induced	Lobar; any location in young adults	Toxicology; context (cocaine, amphetamines, anticoagulants)	Sympathomimetics cause acute hypertension → rupture; often lobar

1.3.2 Hematoma Expansion — Prediction and Prevention

A = longest diameter (cm), B = perpendicular diameter at longest point, C = number of 10-mm CT slices with hemorrhage. Volume = (AxBxC)/2. >30 mL = high-risk; >60 mL = very high-risk.
CT spot sign (active bleeding into hematoma on CTA contrast pooling), irregular margin, blend sign, black hole sign, island sign — all predict expansion risk. Time from onset <6h (peak expansion). Anticoagulant use. Liver disease.
TXA 1g IV within 8h — reduces hematoma expansion but does not improve functional outcome (TICH-2, Lancet 2018). May be considered in spot-sign positive ICH within 4.5h (ongoing trials).

1.3.3 Anticoagulation Reversal in ICH — Updated Protocols

Agent	Reversal Agent	Dose	Time to Effect	Additional Notes
Warfarin	4-factor PCC (KCentra/Beriplex)	25-50 units/kg IV based on INR	Minutes; INR normalized in 15 min	Add IV Vitamin K 10 mg (slow) — reversal sustained. FFP slower, more volume.
Heparin (UFH)	Protamine sulfate	1 mg per 100 units heparin IV (max 50 mg)	Immediate	Risk of anaphylaxis; monitor APTT
LMWH	Protamine (partial reversal)	1 mg per 1 mg enoxaparin given in last 8h	Partial reversal of anti-Xa	No full reversal agent; andexanet alfa off-label
Dabigatran	Idarucizumab (Praxbind)	5 g IV (2 x 2.5 g vials)	Minutes; complete reversal	REVERSE-AD: 100% reversal of dabigatran anticoagulation. Dialysis also effective.
Apixaban / Rivaroxaban / Edoxaban	Andexanet alfa (Andexxa)	High dose: 800 mg bolus + 960 mg/h for 2h; Low dose: 400 mg + 480 mg/h	Minutes; 90%+ reversal in ANNEXA-4	ANNEXA-4: 82% excellent hemostasis; approved for apixaban/rivaroxaban. Expensive.
Any Factor Xa inhibitor (if andexanet unavailable)	4-factor PCC 25-50 units/kg (off-label)	15-30 minutes	Partial reversal; 50-70% anti-Xa activity restoration	Reasonable bridge when andexanet unavailable; not FDA-approved for this indication

1.3.4 Surgical Intervention in ICH

EMERGENT suboccipital decompressive craniectomy + hematoma evacuation. Strong evidence; potentially life-saving. Do not delay — herniation can occur rapidly.
Minimally invasive surgery (parafascicular transsulcal approach) for spontaneous lobar or basal ganglia ICH (30-80 mL): early MIS within 24-72h improved functional outcome at 180 days vs conservative (mRS 0-3: 46% vs 24%). Significant advance over MISTIE III (2019) which used catheter-based aspiration.
CT-guided stereotactic aspiration/thrombolysis: reduced hematoma to <15 mL associated with better outcomes, but primary outcome missed significance. Technique refined in ENRICH.
STICH, STICH II: conventional craniotomy NOT superior to medical management for most supratentorial ICH. Exceptions: lobar ICH in patients deteriorating within 1 cm of cortical surface (STICH II trend).

1.3.5 Restarting Anticoagulation After ICH

Decision requires weighing ongoing thrombotic risk (AF, mechanical valve, prior VTE) vs. re-bleeding risk (CAA, uncontrolled HTN, prior hemorrhage).
RESTART trial (Lancet 2019): Antiplatelet restart after ICH — aspirin appears safe (did not increase ICH recurrence; may reduce ischemic events). Limited to antiplatelet, not anticoagulant.
Optimal timing unknown. Generally 4-8 weeks post-ICH for small deep hemispheric; 8-12 weeks for lobar (high CAA risk). Ongoing APACHE-AF, ASPIRE, OAC-CPR trials will provide randomized data.
Very high re-bleeding risk (3-5%/year). Anticoagulation generally avoided if possible; use aspirin or no antiplatelet. DOAC avoidance if Boston Criteria probable/definite CAA.

📚 References & Evidence

[G1] Greenberg SM et al. 2022 AHA/ASA Guideline for the Management of Patients with Spontaneous ICH. Stroke. 2022;53:e282-361.
[T] ENRICH (2024): JAMA 2024. Minimally invasive parafascicular surgery for lobar/basal ganglia ICH 30-80mL within 24-72h: mRS 0-3 at 180d 46% vs 24%. NNT=4.5.
[T] TICH-2 (2018): Sprigg N et al. Lancet 2018;391:2107-15. Tranexamic acid 1g IV within 8h: reduced hematoma expansion but no functional outcome benefit.
[T] RESTART (2019): Lancet Neurol. 2019;18:643-52. Antiplatelet restart vs avoid after ICH: no increase in recurrent ICH; trend toward reduced ischemic events (restarted aspirin appears safe).
[5] Boston Criteria v2.0 for Cerebral Amyloid Angiopathy. Charidimou A et al. Lancet Neurol. 2022;21:714-725.

1.4 Subarachnoid Hemorrhage (SAH)

1.4.1 Grading, Prognosis, and Initial Stabilization

Scale	Grade	Clinical/Radiological Features	Predicted Outcome
Hunt-Hess	I / II	Mild headache, intact; or moderate headache, CN palsy	Good surgical risk; 90% survival
Hunt-Hess	III	Drowsy, confused, mild focal deficit	Intermediate risk; 70% survival
Hunt-Hess	IV / V	Stupor/coma; decerebrate; moribund	High surgical risk; 40-50% / <20% survival
WFNS	I (GCS 15, no motor deficit)	Best grade; excellent prognosis	90% good outcome
WFNS	IV-V (GCS 7-3)	Severe; high mortality	<30% good outcome
Fisher/Modified Fisher	Grade 1-4 (CT blood burden)	Higher Fisher = higher vasospasm risk	Grade 3-4: highest DCI risk

1.4.2 Aneurysm Securing — Timing and Approach

Strongly recommended to prevent rebleeding (highest risk in first 24h, 4% per day). ISAT trial: coiling vs clipping — coiling superior for most aneurysms (disability/death 23.5% vs 30.6% at 1 year).
Coiling preferred for: posterior circulation aneurysms, elderly, poor-grade (IV/V), aneurysm morphology favorable (saccular, dome-neck ratio >2). Clipping preferred for: large/giant aneurysms, MCA aneurysms, young patients with long life expectancy, wide-neck aneurysms, recurrence after coiling.
For large/giant fusiform or complex aneurysms not suitable for coiling/clipping. Not used in acute SAH phase (requires antiplatelet).

1.4.3 Vasospasm and Delayed Cerebral Ischemia (DCI)

DCI (clinical deterioration from vasospasm) occurs in 20-40% of SAH patients, peak days 4-14, with highest risk on day 7.

Monitoring Modality	Parameter	Threshold for Concern	Notes
TCD (Transcranial Doppler)	MCA mean velocity (cm/s)	>120 cm/s suggests vasospasm; >200 cm/s = severe; Lindegaard ratio (MCA/ICA) >3 = true cerebral vasospasm	Daily TCD from day 3 to day 14; non-invasive; operator-dependent
CT Perfusion	MTT, CBF maps	Asymmetric prolonged MTT; CBF reduction	Performed when TCD changes or clinical deterioration; guides intervention timing
CT Angiography	Vessel caliber	Narrowing >25-50% from baseline	Quick; widely available; limited for distal vessels
Digital Subtraction Angiography	Vessel caliber + hemodynamics	Definitive; used when CTA inconclusive or IA intervention needed	Gold standard; allows simultaneous treatment
Brain multimodal monitoring	Cerebral microdialysis, brain O2, ICP/CPP	Lactate:pyruvate >40; PbrO2 <15 mmHg; ICP >20 mmHg	ICU-based; invasive; research/specialized centers

⭐ DCI MANAGEMENT ALGORITHM (AHA 2023)

Nimodipine 60 mg PO/NG q4h for 21 days — Class I (only proven agent to reduce poor outcome, not vasospasm itself)
Euvolemia maintenance — Class I (replace fluid losses; CVP-guided or volumetric monitoring); avoid hypervolemia
Induced hypertension (SBP 160-200 mmHg) — Class IIa for symptomatic vasospasm if aneurysm secured; use phenylephrine or norepinephrine
Endovascular intervention for refractory DCI: intra-arterial verapamil, nicardipine, milrinone; balloon angioplasty for proximal large-vessel vasospasm
Statins (simvastatin, pravastatin): NOT proven to reduce DCI (STASH, MASH trials); no longer recommended
Magnesium sulfate infusion: NOT proven in large trials (IMASH, MASH-2); not recommended routinely
EEG monitoring: continuous cEEG recommended if H-H grade III-V to detect non-convulsive seizures

1.4.4 Other SAH Complications

Complication	Incidence	Management
Rebleeding	4% in first 24h without securing; 20-30% in first 2 weeks	Emergent aneurysm securing; antifibrinolytics (tranexamic acid) for brief pre-operative bridge (AHA 2023 Class IIa)
Acute hydrocephalus	15-20% acutely	External ventricular drain (EVD); lumbar drain for communicating hydrocephalus; VP shunt for persistent (25-30%)
Cardiac complications	50-100% (ECG changes)	ST changes, T-wave inversions, QTc prolongation; troponin elevation; neurogenic stunned myocardium; avoid beta-blockers in hypovolemic patient
Hyponatremia	30-40%	SIADH or cerebral salt wasting (CSW); distinguish: CSW = low sodium + low volume; treat CSW with fluid + salt, NOT fluid restriction. Hypertonic saline for severe cases
Seizures	5-10% (early); 3-7% (late)	Prophylactic ASM for 3-7 days peri-procedurally (AHA 2023 Class IIa); avoid long-term prophylaxis unless seizure occurs
Delayed cerebral ischemia (DCI)	20-40%	See algorithm above

📚 References & Evidence

[G1] Connolly ES Jr et al. 2012 AHA/ASA Guidelines for the Management of Aneurysmal Subarachnoid Hemorrhage. Stroke. 2012;43:1711-37.
[T] ISAT (2002): Molyneux AJ et al. Lancet 2002;360:1267-74. Endovascular coiling vs surgical clipping for ruptured aneurysms: dependency/death 23.5% vs 30.6% at 1 year. Established coiling preference when feasible.
[3] Nimodipine 60mg q4h for 21 days after SAH: Class I recommendation for vasospasm prevention (multiple RCTs and meta-analyses).

2. Epilepsy & Seizure Disorders

Epilepsy affects 50 million people worldwide (prevalence ~1%). Epilepsy is defined as ≥2 unprovoked seizures >24 h apart, OR one unprovoked seizure with ≥60% recurrence risk over 10 years, OR diagnosis of an epilepsy syndrome (Fisher et al., ILAE 2014). This section integrates the landmark ILAE 2025 Seizure Classification (Beniczky et al., Epilepsia 2025), ILAE 2022 Syndrome Classification, ASM pharmacology, status epilepticus staged protocol (ESETT 2019), and surgical evaluation — written at neurologist + IM specialist depth.

▶2.1 Definitions & Epidemiology

Core Definitions (ILAE)

Term	Definition	Key Point
Seizure	Transient occurrence of signs/symptoms due to abnormally excessive or synchronous neuronal activity in the brain (ILAE 2005)	Paroxysmal; behavioral, somatosensory, motor, autonomic, cognitive, or emotional
Convulsion	Subset of seizures with prominent motor features	Not synonymous with seizure
Epilepsy	Disease of the brain defined by: (1) ≥2 unprovoked seizures >24 h apart; OR (2) one unprovoked seizure with ≥60% recurrence risk; OR (3) diagnosis of an epilepsy syndrome (Fisher 2014)	Practical clinical definition — NOT just "recurrent seizures"
Epilepsy resolution	Applicable if patient has been seizure-free for 10 years AND off AEDs for last 5 years; OR age-dependent syndrome now past applicable age	Replaces old concept of "outgrown" epilepsy
Provoked seizure	Seizure with identifiable acute precipitant: metabolic, toxic, structural (acute), infectious	Does NOT meet criteria for epilepsy diagnosis; treat underlying cause
Drug-resistant epilepsy	Failure of adequate trials of ≥2 tolerated, appropriately chosen AED schedules to achieve sustained seizure freedom	~30% of patients with epilepsy are drug-resistant

Clinical Pearl — Epilepsy ≠ First Seizure: A first unprovoked seizure does NOT automatically mean epilepsy. The decision to treat depends on recurrence risk. Key factors that increase risk: prior brain insult (Level A), epileptiform EEG (Level A), significant MRI abnormality (Level B), nocturnal seizure (Level B). Risk of recurrence after 1st unprovoked SZ = 21–45%, highest within 2 years (AAN 2015).

Epidemiology

Parameter	Data
Global prevalence	~50 million (~1% of population); ~80% in low/middle income countries
Annual incidence	50/100,000/year (developed); 100–190/100,000/year (developing)
Lifetime risk	~3% cumulative risk of epilepsy by age 80
Age distribution	Bimodal: peak in first decade and after age 60
Etiology ILAE 2017	Structural, Genetic, Infectious, Metabolic, Immune, Unknown (replaces symptomatic/idiopathic/cryptogenic)
Drug-resistant	~30% despite optimal therapy; consider surgical evaluation after ≥2 AED failures
Recurrence after 2nd SZ	76% chance of 3rd SZ; 86% after 3rd SZ

▶2.2 ILAE 2025 Seizure Classification — Updated Position Paper

Reference: Beniczky S, et al. "Updated Operational Classification of Seizure Types by the ILAE." Epilepsia 2025; DOI: 10.1111/epi.18338. — Supersedes the ILAE 2017 classification (Fisher et al., Epilepsia 58:522–530, 2017).

ILAE 2025 — 6 Key Changes from 2017

#	Change	2017 Term	2025 Term	Clinical Impact
1	Remove "onset" from class names	"Focal onset seizure"	"Focal seizure"	Onset is always implied; simplifies terminology
2	Classifiers vs. Descriptors distinction	Not explicit	Classifiers (define seizure type) vs. Descriptors (characterize features)	Classifiers drive management; descriptors enrich clinical documentation
3	Consciousness replaces awareness as classifier	"Focal aware" / "Focal impaired awareness (FIA)"	Consciousness = awareness + responsiveness; "Focal impaired consciousness (FIC)"	If EITHER awareness OR responsiveness impaired → impaired consciousness; more operationally precise
4	Motor/nonmotor → observable vs. non-observable	"Motor onset" / "Nonmotor onset"	Observable / Non-observable manifestations (basic version)	Better reflects what clinician and witness can describe
5	Chronological semiology sequence	Single dominant feature named	Sequence of semiological features described chronologically (expanded version)	Enables precise localization; supports surgical planning
6	Negative myoclonus as new generalized seizure type	Not recognized	Generalized negative myoclonus (GNM, code 3.3.4)	Brief interruption of tonic muscle activity; epileptic drop attacks in LGS, atonic spectrum

ILAE 2025 Taxonomic Hierarchy (Table 1) — Complete

Class	Code	Seizure Type	Key Features
1. Focal (F)	1.1	Focal preserved consciousness (FPC)	Both awareness AND responsiveness intact; replaces "focal aware (FA)"
	1.2	Focal impaired consciousness (FIC)	Either awareness OR responsiveness impaired; replaces "focal impaired awareness (FIA)"; includes new "focal unaware" subtype (complete unawareness)
	1.3	Focal to bilateral tonic-clonic (FBTC)	Was "focal to bilateral TC"; replaces "secondarily generalized"; adverse lateralizing signs possible
2. Unknown whether focal or generalized (U)	2.1	Preserved consciousness (PC)	Clinical features present but onset undetermined
	2.2	Impaired consciousness (IC)	Consciousness impaired; origin unknown
	2.3	Bilateral tonic-clonic (BTC)	Bilateral motor; onset undetermined
3. Generalized (G)	3.1.1	Typical absence (TA)	Abrupt onset/offset; 3 Hz GSW; brief (5–20 s); complete loss of awareness; automatisms common
	3.1.2	Atypical absence (AA)	Gradual onset/offset; slower 1.5–2.5 Hz SW; longer duration; seen in LGS, Dravet
	3.1.3	Myoclonic absence (MA)	Absence + rhythmic myoclonic jerks; shoulders/arms; 3 Hz GSW
	3.1.4	Eyelid myoclonia with absence (EMA)	Jeavons syndrome; eyelid flutter + upward gaze; photosensitive; EEG 3–6 Hz GSW
	3.2.1	Generalized tonic-clonic (GTC)	Classic GTCS: tonic then clonic; post-ictal confusion; incontinence common
	3.2.2	GTC with myoclonic onset	New 2025 formalized type; myoclonic jerks → GTC (JME morning pattern); EEG: polyspike → GTC
	3.2.3	TC with clonic onset	New 2025 type; clonic → tonic → clonic sequence (CTC); distinct from classic GTC
	3.3.1	Generalized myoclonic (GM)	Brief bilateral muscle jerks; EMG: brief high-amplitude discharge; EEG: polyspike-wave
	3.3.2	Generalized clonic (GC)	Rhythmic bilateral clonic movements without tonic phase
	3.3.3	Generalized tonic (GT)	Sustained bilateral muscle contraction; EEG: fast activity or low-amplitude; seen in LGS
	3.3.4	Generalized negative myoclonus (GNM)	NEW in 2025: brief interruption of tonic posture; EEG: polyspike-wave >200 ms before EMG silence; epileptic atonia
3.3.5–3.3.7	3.3.5	Generalized epileptic spasms (GES)	Infantile spasms / West; brief neck/trunk flexion-extension; EEG: hypsarrhythmia (interictal)
3.3.5–3.3.7	3.3.6–7	Generalized atonic (GA) & Myoclonic-atonic (GMA)	Atonic: sudden loss of postural tone; Myoclonic-atonic: jerk then drop (Doose syndrome)
4. Unclassified	4.0	Unclassified	Insufficient information or does not fit other categories

Consciousness in ILAE 2025 — Operational Definition

Consciousness = Awareness + Responsiveness

Awareness = ability to perceive and recall events during the seizure (retrospective recall)
Responsiveness = ability to react appropriately to stimuli during the seizure
If EITHER awareness OR responsiveness is impaired → impaired consciousness → classify as FIC (1.2)
Full FPC (1.1) requires BOTH awareness AND responsiveness preserved

"Focal unaware" = new 2025 subtype of FIC where awareness is completely absent (not partial); reserved for pure unawareness without other features. FIA (focal impaired awareness) is retained within FIC for partial impairment.

New Seizure Types in ILAE 2025

New Type	Definition	Clinical Relevance
Behavior arrest seizure	Sudden cessation of behavior WITHOUT other features; standalone type in BOTH focal (FPC or FIC) and generalized categories	Previously underrecognized; may be only manifestation; distinguish from absence (no EEG 3 Hz SW required)
GTC with myoclonic onset (3.2.2)	Myoclonic jerks precede the GTC by seconds	Formalized JME pattern; polyspike-wave on EEG; validates JME diagnosis when present
TC with clonic onset (CTC) (3.2.3)	Clonic → tonic → clonic sequence; differs from classic tonic → clonic pattern	Seen in frontal lobe epilepsy and some structural epilepsies; EEG may show fast activity onset
Generalized negative myoclonus (GNM) (3.3.4)	Brief interruption of sustained tonic activity; EMG silence >200 ms; corresponds to epileptic drop attacks	Important in LGS; atonic-appearing; distinguished from atonic by EMG silence timing relative to EEG discharge

ILAE 2025 Semiological Descriptors (Table 2) — Classifiers vs. Descriptors

Category	Classifiers (drive seizure type, management)	Descriptors (document features)
Consciousness	Preserved / Impaired (FPC vs FIC)	Awareness level, responsiveness details
Motor	Observable (tonic, clonic, myoclonic, atonic, spasm, automatisms) vs Non-observable	Distribution, lateralization, evolution, duration, intensity
Non-motor (sensory/autonomic/cognitive)	Present/absent in basic version	Type: somatosensory, visual, auditory, olfactory, gustatory, autonomic, psychic, cognitive details
Lateralization	Bilateral symmetrical / Bilateral asymmetric / Unilateral	Side of origin, lateralizing signs (figure-of-4, head version, ictal dystonia)
Evolution	Included in FBTC classification	Chronological sequence: aura → motor → post-ictal

Clinical Pearl — 2017 vs 2025 Terminology Quick Reference:
Old 2017 "Focal onset" → 2025 "Focal" (onset dropped)
Old 2017 "Focal aware (FA)" → 2025 "Focal preserved consciousness (FPC)"
Old 2017 "Focal impaired awareness (FIA)" → 2025 "Focal impaired consciousness (FIC)" (broader: includes awareness + responsiveness)
Old 2017 "Focal to bilateral TC" → 2025 "Focal to bilateral tonic-clonic (FBTC)" (same concept, retained)
Old 2017 "Unknown onset" → 2025 "Unknown whether focal or generalized" (more precise)
Old 1981 "Simple partial" → FPC; "Complex partial" → FIC; "Secondarily generalized" → FBTC

▶2.3 Focal Seizures — Semiology, Localization & Lateralization

Focal Seizure Types and Localization

Seizure Type (ILAE 2025)	Typical Semiology	Probable Localization	EEG
FPC — Aura (sensory)	Rising epigastric sensation, déjà vu/jamais vu, fear, olfactory (uncinate), visual (flashes, formed hallucinations), somatosensory	Mesial temporal (epigastric/déjà vu), insula (epigastric), occipital (visual), parietal (somatosensory), frontal orbital (olfactory)	Regional theta/alpha slowing; spikes or spike-wave
FPC — Motor onset (Jacksonian)	Clonic or tonic activity marching from distal → proximal (Jacksonian march); postictal Todd's paralysis	Contralateral primary motor cortex (precentral gyrus); somatotopic organization	Contralateral central spike/polyspike
FIC (with automatisms)	Behavioral arrest + oroalimentary automatisms (chewing, swallowing, lip-smacking) + hand fumbling; post-ictal confusion	Mesial temporal (hippocampus/amygdala); temporal lobe epilepsy	Temporal theta; may evolve to bilateral rhythmic delta
FIC (hypomotor/behavioral arrest)	Sudden arrest of activity; staring; minimal movement; preserved or impaired responsiveness	Frontal (mesial/orbital), temporal, parietal	Frontal theta/alpha or temporal slowing
FPC/FIC — Frontal motor	Nocturnal; brief (<30 s); hypermotor (bicycling, thrashing, kicking); asymmetric tonic posturing; minimal post-ictal; may cluster	Frontal lobe; supplementary motor area (SMA) → asymmetric tonic posturing (fencer posture); frontal opercular; orbitofrontal	Frontal spike or may be normal (deep source)
FBTC	Begins as focal (aura/automatisms) then evolves to bilateral tonic → clonic; post-ictal confusion; prolonged	Focal onset (temporal, frontal) → secondary generalization; replaces "secondarily generalized"	Regional onset → evolving bilateral ictal pattern

Lateralizing & Localizing Signs

Sign	Lateralization	Notes
Figure-of-4 sign	Extension arm = IPSILATERAL to seizure onset (opposite to expected)	Most reliable lateralizing sign; high specificity for MTLE; contralateral arm flexed
Head version (ictal)	CONTRALATERAL to onset (frontal/temporal)	Late versive movement before secondary generalization; forced and sustained
Ictal unilateral dystonia	Dystonic arm = CONTRALATERAL to seizure focus	Very high localizing value; mesial temporal or basal ganglia involvement
Todd's paralysis	CONTRALATERAL to ictal focus	Post-ictal motor weakness; resolves in minutes to hours; indicates motor cortex involvement
Ictal eye deviation	CONTRALATERAL to onset (frontal lobe); IPSILATERAL to onset (temporal); post-ictal deviation: IPSILATERAL to focus	Frontal = contraversive; temporal = ipsiversion or no deviation
Ictal nose-wiping / automatism	IPSILATERAL to seizure focus	Occurs post-ictally with ipsilateral hand; high sensitivity for TLE
Unilateral clonic activity	CONTRALATERAL hemisphere	Most reliable for localization; primary motor cortex involvement
Ictal vomiting/spitting	DOMINANT hemisphere (language)	Non-dominant hemisphere produces ictal vomiting; right TLE in right-handers
Post-ictal aphasia	DOMINANT hemisphere temporal lobe	Left TLE in right-handers; reliable lateralizer for language-dominant side

Clinical Pearl — MTLE Semiology (High-Yield Board Pattern): Classic mesial temporal lobe epilepsy (most common drug-resistant focal epilepsy): Epigastric aura → behavioral arrest → oroalimentary automatisms (lip-smacking, chewing) + ipsilateral hand fumbling → post-ictal confusion. Figure-of-4 sign and ictal dystonia strongly lateralize to contralateral hemisphere. MRI: unilateral hippocampal atrophy + T2/FLAIR hyperintensity (hippocampal sclerosis). ~60–70% are drug-resistant → surgical candidate; 70% seizure-free post-ATL (anterior temporal lobectomy).

▶2.4 Generalized Seizures

Generalized Seizure Types — Clinical & EEG Characteristics

Type (ILAE 2025)	Clinical Features	EEG	Key Syndrome Associations	ASM Trap
Typical absence (3.1.1)	Abrupt onset/offset; staring; loss of awareness 5–20 s; automatisms (lip-smacking, hand gestures, eyelid fluttering); precipitated by hyperventilation; NO post-ictal	Bilateral symmetric 3 Hz spike-and-wave (GSW); background normal	CAE (most), JAE, JME (minor)	CBZ/OXC/PHT/GBP worsen absence! May precipitate absence SE
Atypical absence (3.1.2)	Gradual onset/offset; less complete loss of awareness; tone changes; longer duration; associated with cognitive impairment	Slow (1.5–2.5 Hz) spike-and-slow-wave; background often abnormal	Lennox-Gastaut syndrome, Dravet, Doose	Avoid narrow-spectrum AEDs
Myoclonic absence (3.1.3)	Absence + rhythmic myoclonic jerks of shoulders/arms/face; 3 Hz rhythm; lasts 10–60 s	3 Hz GSW with myoclonic correlation on EMG	Myoclonic absence epilepsy (MAE)	ETX less effective; VPA/LTG preferred
Eyelid myoclonia with absence (3.1.4)	Eyelid flutter/jerking + upward eye deviation + absence; triggered by eye closure and light; very photosensitive	3–6 Hz GSW triggered by eye closure or photic stimulation	Jeavons syndrome	Photosensitivity: avoid light triggers; VPA/LEV/LTG/CLB
GTC (3.2.1)	Tonic phase (10–20 s): rigid limbs, cyanosis, apnea, Valsalva cry → Clonic phase (30–90 s): rhythmic jerks decreasing frequency → Post-ictal: confusion minutes–hours, deep sleep, muscle aches	Recruiting rhythm → polyspike-wave; post-ictal generalized suppression	JME, JAE, GTCA, all generalized epilepsies, structural	CBZ may worsen in IGE context
GTC with myoclonic onset (3.2.2)	Myoclonic jerks (bilateral, brief) precede GTC by seconds; often on awakening; EEG correlate: polyspike → GTC pattern	Polyspike-wave burst → evolving GTC pattern	JME (classic morning awakening pattern)	VPA/LTG/LEV — do NOT use CBZ/OXC/PHT
TC with clonic onset (3.2.3)	Clonic → tonic → clonic; distinct from classic tonic → clonic sequence; often frontal lobe or structural etiology	Focal fast onset → bilateral clonic then tonic pattern	Frontal lobe epilepsy, some structural epilepsies	New 2025 type; important for surgical localization
Generalized myoclonic (3.3.1)	Brief (<100 ms) bilateral symmetric jerks; usually upper limbs/face; consciousness preserved; "lightning jerks"	Polyspike or polyspike-wave; time-locked to jerks	JME, PME, Dravet, MAE	PHT/CBZ/OXC may worsen; VPA/LEV/ZNS preferred
Generalized tonic (3.3.3)	Sudden bilateral sustained muscle contraction; axial/proximal; brief (5–20 s); falls common; nocturnal in LGS	Fast 10–25 Hz activity ("tonic seizure pattern") or generalized paroxysmal fast activity (GPFA)	Lennox-Gastaut syndrome, Dravet	Avoid AEDs that may precipitate tonic SE (CBZ, OXC, vigabatrin)
Generalized negative myoclonus (3.3.4)	Brief interruption of tonic posture (>200 ms EMG silence); looks like mini-atonic drops; consciousness usually preserved	Generalized polyspike-wave burst; EMG silence 200–400 ms after discharge	LGS atonic variants, epileptic encephalopathies	NEW 2025; distinguish from atonic seizure by EMG timing
Generalized atonic (3.3.6)	Sudden loss of postural tone; "drop attacks"; head drop or falls; very brief (1–2 s); high injury risk; NO loss of consciousness typically	Slow spike-wave or paroxysmal fast activity; brief high-amplitude discharge followed by EMG silence	LGS (atonic = "astatic"), Doose (myoclonic-atonic)	VPA/LTG/CLB/RFN; ketogenic diet for refractory
Epileptic spasms (3.3.5)	Brief (1–2 s) axial flexion ± extension; clusters on awakening; infantile spasms = West syndrome; developmental regression	Hypsarrhythmia (interictal); electrodecremental response (ictal)	West syndrome; structural, genetic, metabolic causes	ACTH/vigabatrin 1st line; consider TSC-specific (everolimus)

Typical Absence vs. FIC (FIA) — Critical Clinical Trap

Feature	Typical Absence (GE)	Focal Impaired Consciousness (FIC/FIA)
Duration	3–20 seconds	30 seconds – 3 minutes
Onset/offset	Abrupt (like a switch)	Gradual onset; post-ictal confusion
Post-ictal state	NONE — immediate return	Confusion, fatigue, often minutes–hours
Automatisms	Simple (eyelid flutter, lip-smacking, minor hand)	Complex (hand fumbling, oroalimentary, gestural)
Precipitants	Hyperventilation (87%); photic in some	None specific; may be sleep-related
EEG (ictal)	3 Hz bilateral symmetric GSW; background normal	Regional theta/slow; temporal or frontal focus
MRI	Normal (genetic)	Often abnormal (hippocampal sclerosis, FCD, tumor)
Age	Typically children 4–14 (CAE); older (JAE)	Any age; MTLE commonly adults
ASM choice	ETX, VPA, LTG	LTG, LEV, OXC, LCM, CBZ
DANGER	Misdiagnosing FIC as typical absence → prescribing CBZ/OXC (will not harm but miss focal treatment) OR diagnosing absence as FIC → giving CBZ → absence SE precipitated!

▶2.5 Differential Diagnosis of Paroxysmal Events

Seizure Mimics — Key Differential Diagnoses

Condition	Features Favoring This Diagnosis	Key Distinguishing Tests
Convulsive syncope	Preceded by lightheadedness, diaphoresis, pallor; myoclonus AFTER loss of consciousness; upward eye deviation; arrhythmic jerks (multifocal, brief 1–15 s); NO post-ictal confusion; NO tongue biting; quick recovery	Tilt-table test; ECG/Holter; serum lactate (low in syncope); EEG (normal)
Psychogenic non-epileptic seizure (PNES)	Asynchronous movements; pelvic thrusting; eye closure during event; prolonged with fluctuating course; multiple events in short period; stress trigger; no post-ictal; normal EEG during event; no elevation of prolactin	Video-EEG monitoring (gold standard); serum prolactin (elevated 15–20 min post-ictal GTC, normal in PNES)
TIA	Negative symptoms (loss of function); no spread; older patients; vascular risk factors; usually no jerking	MRI DWI; carotid duplex; cardiac echo; ECG
Migraine with aura	Visual aura: gradual spread (march) over minutes, positive (scintillating scotoma) then negative; followed by headache; no LOC; longer duration (20–60 min)	Clinical; MRI (normal or white matter); EEG (normal or non-specific)
Hypoglycemia	Diaphoresis, tremulousness; can cause focal neurological deficits; responds to glucose; check blood glucose immediately	Glucose <55 mg/dL; rapid response to IV dextrose; EEG may show diffuse slowing
Sleep disorders (parasomnia)	REM sleep behavior disorder: acting out dreams; NREM: sleepwalking (no memory); sleep terrors; occur from sleep; variable EEG	Polysomnography (PSG) + video; clinical history
Movement disorders	Paroxysmal dyskinesias (PKD, PNKD): involuntary movements triggered by movement/caffeine/stress; consciousness preserved; no EEG correlate; duration minutes	EEG (normal during event); genetics (PRRT2 for PKD); response to CBZ in PKD

Convulsive Syncope vs. Epileptic Seizure

Feature	Convulsive Syncope	Epileptic Seizure
Onset of myoclonus	Follows loss of consciousness (after falling)	Immediate (before or with LOC)
Eye deviation	Upward	Lateral (contralateral to focus)
Myoclonus rhythm	Arrhythmic jerks	Rhythmic jerks (clonic)
Myoclonus pattern	Multifocal; proximal and distal; bilateral	Unilateral/asymmetric or bilateral symmetric with evolution
Duration of jerks	1–15 seconds	30 seconds – 2 minutes
Urinary incontinence	May occur	Common (especially GTC)
Post-ictal confusion	NO — rapid return to normal	YES — post-ictal confusion common
Tongue biting	Rare, tip of tongue	Lateral tongue biting (highly specific for GTC)
Serum lactate/CK	Low/normal	Elevated lactate, elevated CK after GTC
Prolactin (15–20 min post)	Normal	Elevated (×2 baseline) after GTC or complex focal; NOT reliable for focal SZ; NOT elevated in absence

Clinical Pearl — PNES Diagnosis: 12% of syncope has "myoclonic jerks" (convulsive syncope) — arrhythmic, multifocal, brief, NO post-ictal. PNES: video-EEG is gold standard; asynchronous movements, eye closure, pelvic thrusting, long duration with waxing-waning, normal ictal EEG during event, normal prolactin. Importantly, PNES and epilepsy COEXIST in 10–30% of patients with confirmed PNES.

▶2.6 Epilepsy Diagnosis Framework & Investigation

ILAE 2017 Four-Level Diagnostic Framework

Level	Categories	Examples	Clinical Action
1. Seizure type (ILAE 2025)	Focal (FPC/FIC/FBTC); Generalized (absence/tonic/clonic/myoclonic/atonic/GTC); Unknown; Unclassified	FIC with automatisms; Typical absence; GTC with myoclonic onset	Acute management; initial ASM selection
2. Epilepsy type	Focal; Generalized; Combined generalized+focal; Unknown	Focal epilepsy (MTLE); Generalized epilepsy (JME); LGS (combined)	ASM class: avoid Na+ channel blockers in generalized epilepsy
3. Epilepsy syndrome	Specific defined syndrome (ILAE 2022)	CAE, JME, Dravet, LGS, MTLE, West, BECT	Syndrome-specific ASM; genetic counseling; prognosis
4. Etiology	Structural, Genetic, Infectious, Metabolic, Immune, Unknown	Hippocampal sclerosis (structural); SCN1A (genetic); Anti-LGI1 (immune)	Disease-specific therapy; surgical candidacy; inheritance risk

Etiology + comorbidities assessed at ALL levels simultaneously. Comorbidities (depression, anxiety, cognitive, sleep) impact quality of life and treatment decisions.

Investigation of New-Onset Seizures

Investigation	Indication	Key Points
EEG	All patients with first seizure or suspected epilepsy	Sensitivity 50% single; up to 80–90% after ≥3 serial EEGs. Epileptiform pattern increases recurrence risk: 30% → 70% in 1st year. Best within 24–48 h of seizure (higher yield). Sleep-deprived EEG or video-EEG for unclear cases.
MRI brain	All patients with new seizure EXCEPT confirmed genetic generalized epilepsy syndrome (e.g., CAE with classic 3 Hz GSW, no focal features)	Normal CT misses 12% of abnormalities detected on MRI. Epilepsy protocol: 3T, coronal FLAIR, T1 volumetric, T2 hippocampal sequences. Look for hippocampal sclerosis, FCD, tumors, vascular malformations, heterotopia.
Blood glucose, electrolytes, calcium, Mg	All emergency seizure presentations	Exclude metabolic causes: hyponatremia, hypoglycemia, hypocalcemia, hypomagnesemia, uremia
Serum prolactin	Selected cases: GTC vs. PNES	Elevated ×2 baseline 15–20 min after GTC or FIC; not useful for absence; not reliable for focal alone; not gold standard
Genetic testing	Early-onset epilepsy, drug-resistant, family history, suspected genetic syndrome	Chromosomal microarray, gene panel, WES/WGS for epileptic encephalopathies. SCN1A (Dravet), KCNQ2, CDKL5, ARX, MECP2, TSC1/2
Autoimmune panel	New-onset seizures with encephalopathy, rapid progression, CSF pleocytosis, failure to respond to ASM	NMDAR, LGI1, CASPR2, GABA-B, AMPAR antibodies (serum + CSF). LGI1: faciobrachial dystonic seizures (FBDS) pathognomonic — treat immunotherapy before widespread epilepsy develops
LP / CSF analysis	Fever + seizure, altered consciousness, suspected encephalitis or meningitis	Opening pressure, cell count, protein, glucose, culture, PCR (HSV, VZV, enterovirus, TB), VDRL, India ink, cytology if malignancy suspected
CT head (acute)	Acute setting: rule out hemorrhage, large structural lesion, herniation before LP	Emergency use; MRI preferred for epilepsy workup. CT misses small lesions, FCD, HS, vascular malformations

Clinical Pearl — LGI1 Antibody Epilepsy: Faciobrachial dystonic seizures (FBDS) = brief unilateral arm ± face tonic/dystonic posturing, <3 sec, very frequent (>100/day), consciousness preserved. This is PATHOGNOMONIC for LGI1 autoimmune encephalitis. Treat with immunotherapy (steroids ± IVIG) BEFORE widespread seizures and memory loss develop — ASMs alone are largely ineffective for FBDS. Anti-LGI1 is also associated with hyponatremia and SIADH.

▶2.7 First Unprovoked Seizure — Management

Reference: Krumholz A, et al. "Evidence-based guideline: Management of an unprovoked first seizure in adults." Neurology 2015;84:1705–13. AAN/AES guideline.

First Seizure Management Algorithm

Step	Action	Key Points
1. Is it a seizure?	Distinguish epileptic seizure from mimics (syncope, PNES, TIA, parasomnia)	Obtain detailed history from patient AND witness; ask about: prodrome, onset, evolution, post-ictal state, duration
2. Is it the first seizure?	Ask about prior events: myoclonic jerks on awakening, nocturnal tongue biting, brief staring spells	Often the "first" GTC is actually not the first seizure — prior absence/myoclonic/focal SZ may have been missed
3. Provoked or unprovoked?	Assess for metabolic, toxic, structural (acute), or infectious precipitants	Provoked = treat underlying cause; does NOT meet epilepsy criteria; recurrence risk not increased by prior SZ count within 24h
4. Assess recurrence risk	AAN 2015 factors that INCREASE recurrence risk	Prior brain insult (Level A); EEG epileptiform (Level A); Significant MRI abnormality (Level B); Nocturnal seizure (Level B)
5. Treat or observe?	Immediate AED reduces 2-year recurrence risk; does NOT change long-term prognosis (>3 years)	AED treatment: side effects 7–31% (mild/reversible); shared decision-making; consider driving, work, social factors

Recurrence Risk after First Seizure

Scenario	2-Year Recurrence Risk
1st unprovoked seizure (overall)	21–45% (greatest within first 2 years)
With prior brain insult (remote symptomatic)	~65%
With epileptiform EEG	~65% (recurrence risk doubles from 30% → 70%)
With both EEG abnormality + prior insult	~85%
2nd unprovoked seizure	76% chance of 3rd seizure
3rd unprovoked seizure	86% chance of next seizure (72% in children)
Provoked seizure only	Does NOT increase long-term recurrence risk

Clinical Pearl — Immediate AED after First Seizure: Immediate treatment REDUCES 2-year recurrence risk but does NOT improve long-term (≥3 year) seizure-free rates or prognosis. Therefore, the decision to treat must weigh: (1) risk of seizure recurrence and its consequences (driving, occupation, injury), (2) side effects (7–31%, usually mild/reversible), (3) patient preference. A 60-year-old with post-stroke first seizure + MRI abnormality + epileptiform EEG → strong indication to treat. A healthy 25-year-old with first idiopathic GTC, normal EEG and MRI → may observe with shared decision-making.

▶2.8 Epilepsy Syndromes — ILAE 2022 Classification

Reference: ILAE 2022 Syndrome Papers. Epilepsia 2022 (multiple papers): Zuberi SR, et al. (Neonatal/Infant); Specchio N, et al. (Childhood); Hirsch E, et al. (Variable-age). ILAE methodology: Specchio N, et al. Epilepsia 2022.

Idiopathic Generalized Epilepsies (IGE) — Comparison

Feature	CAE	JAE	JME	IGE with GTCS only (GTCA)
% of IGE	15%; F > M	15%; F = M	45%; F ≥ M	25%; F = M
Age of onset	4–10 yr (2–13)	9–13 yr (8–20)	10–24 yr (8–40)	10–25 yr (5–40)
Main SZ type	Typical absence, pyknoleptic (≥daily), 3–20 s; severe loss of awareness	Typical absence; <daily; 5–30 s; less complete loss	Myoclonic jerks; predominantly on awakening	GTC on awakening; infrequent
Other SZ types	GTC 20%; NO prominent myoclonic	GTC 90%; absence 33%; NO prominent myoclonic	GTC >90%; absence 33%	NO absence; NO myoclonic
EEG ictal	3 Hz bilateral symmetric GSW; normal background	3.5–4 Hz GSW; normal background	4–6 Hz GSW + polyspike-wave; normal background	4–5 Hz GSW; generalized polyspikes
Photoparoxysmal	15–21%	~25%	30–90% (especially EMA)	May be seen
Hyperventilation trigger	87%	87%	33%	May occur
Natural history	Drug-responsive; 60% remit by adolescence; 20% persist	Drug-responsive (>80%); lifelong ASM often needed	Drug-responsive (65–92%); lifelong ASM; 78% recur after withdrawal	Drug-responsive; lifelong ASM often needed
Precipitants	Hyperventilation; CBZ/PHT/GBP	CBZ, PHT	Sleep deprivation, alcohol, menses, stress; CBZ/PHT/OXC	Sleep deprivation; alcohol
1st-line ASM	VPA, LTG, ETX (absence only)	VPA, LTG, LEV	VPA, LTG, LEV, TPM, ZNS	VPA, LTG, LEV, TPM
Contraindicated ASM	CBZ, OXC, PHT, GBP, PGB, VGB, TGB, ESL	CBZ, OXC, PHT, GBP, PGB	CBZ, OXC, PHT, GBP, PGB	CBZ, OXC, PHT, GBP, PGB

JME — Juvenile Myoclonic Epilepsy (Most Common IGE in Adults)

JME (Janz syndrome): onset 10–24 years; classic triad: (1) myoclonic jerks on awakening → (2) GTC (often awakening, may follow missed sleep) → (3) absence seizures (33%). Precipitants: sleep deprivation, alcohol, stress, menses, photic stimulation. EEG: 4–6 Hz polyspike-wave; normal background. ILAE 2022: "self-limited" syndrome — high responder to VPA (85%); however, VPA avoided in women → use LTG/LEV/ZNS. Lifelong ASM required — 78% relapse after withdrawal. NEVER use CBZ/OXC/PHT/GBP → worsen myoclonus, may precipitate myoclonic SE.

Self-Limited Focal Epilepsies

Syndrome	Age Onset	Semiology	EEG	Prognosis
SeLECTS (formerly BECT / Rolandic epilepsy)	3–13 yr (peak 7–8); M > F	Focal oro-facial: unilateral face/lip tingling, dysarthria, hypersalivation; may evolve to GTC; predominantly nocturnal; infrequent	High-amplitude centrotemporal spikes (rolandic discharge); horizontal dipole; activated by sleep; normal background	Excellent — remission by puberty (age 16); ASM not always required; avoid in mild cases
Panayiotopoulos syndrome	2–8 yr (peak 4–5)	Autonomic seizures: ictal vomiting, pallor, sweating + eye deviation + altered consciousness; prolonged (30+ min); rare GTCS; may mimic encephalopathy	Occipital and multifocal spike-waves; shifts between regions; normal background	Excellent — self-limited; most remit within 2 years; low seizure frequency; ASM only for frequent/severe
Gastaut syndrome (late-onset childhood occipital)	3–16 yr	Visual symptoms: amaurosis, phosphenes, visual hallucinations; ictal headache; consciousness preserved; post-ictal migraine-like headache	Occipital sharp-slow waves; blocked by eye opening	Variable — may persist; ASM often needed; differentiate from migraine with visual aura

Mesial Temporal Lobe Epilepsy (MTLE)

Feature	Details
Definition	Most common adult focal epilepsy; arises from hippocampus/amygdala/entorhinal cortex; most common cause of drug-resistant epilepsy
Etiology	Hippocampal sclerosis (most common structural cause); febrile status epilepticus in childhood → hippocampal sclerosis → MTLE in adolescence/adulthood ("dual pathology")
Semiology	Epigastric rising aura (most common aura) → behavioral arrest → oroalimentary automatisms (lip-smacking, chewing) + ipsilateral hand fumbling → post-ictal confusion; déjà vu/jamais vu; fear; olfactory aura if uncal involvement
MRI (epilepsy protocol)	Unilateral hippocampal atrophy + T2/FLAIR hyperintensity = hippocampal sclerosis; loss of internal architecture on T1; reduced NAA on MRS
EEG	Interictal: unilateral/bilateral anterior temporal spikes (F7/F8, T7/T8). Ictal: rhythmic 5–7 Hz temporal theta
Natural history	~60–70% drug-resistant; progressive memory impairment; depression ~50%; significant quality of life impact
Surgery	Anterior temporal lobectomy (ATL): 70% seizure-free at 1 year (NEJM 2001 Wiebe trial); superior to continued medical therapy in drug-resistant MTLE; earlier surgery = better outcomes

Epileptic Encephalopathies

Syndrome	Age	Seizure Types	EEG	Treatment	Prognosis
West syndrome	3–12 mo (peak 4–7 mo)	Epileptic spasms (clusters); flexion ± extension; on awakening; developmental regression	Hypsarrhythmia (chaotic high-amp, multifocal spike-wave); electrodecremental response ictally	ACTH (short-term, 2–4 weeks); Vigabatrin (1st-line if TSC); corticosteroids. Vigabatrin 1st choice in TSC (50% spasm-free)	Poor overall (structural causes); 40–60% develop LGS; TSC: better with vigabatrin
Lennox-Gastaut syndrome (LGS)	1–8 yr (peak 3–5 yr)	Tonic (nocturnal, hallmark), atonic (drop attacks, hallmark), atypical absence; myoclonic; high injury risk	Slow spike-wave <2.5 Hz; generalized paroxysmal fast activity (GPFA) 10–25 Hz during tonic SZ; slow/disorganized background	VPA, LTG, CLB (rufinamide for drop attacks); felbamate (limited by hepatotoxicity/aplastic anemia); cannabidiol (FDA 2018); dietary (ketogenic); VNS; corpus callosotomy for drop attacks	Poor — most drug-resistant; persistent cognitive disability; 5–10% mortality in childhood
Dravet syndrome	First year of life (peak 5–8 mo)	Febrile/afebrile clonic/GTC → myoclonic → focal dyscognitive → atypical absence; fever-sensitive; vaccine-proximate	Normal initially → generalized polyspike-wave + multifocal spikes; photosensitive; normal background early	VPA + clobazam (1st-line); stiripentol + VPA + CLB (EU approved); cannabidiol; fenfluramine (recent). AVOID: CBZ, OXC, PHT, LTG, GBP, VGB (worsen, potential SE)	Drug-resistant (~80%); intellectual disability common; SUDEP risk elevated (15–20× normal); ~10–20% mortality by 20 yr
Progressive Myoclonic Epilepsy (PME)	Variable (childhood–adult)	Action myoclonus, GTC, neurological deterioration	Generalized spike-wave; giant somatosensory evoked potentials (SEPs)	VPA, LEV, ZNS (symptomatic); avoid PHT/CBZ. Specific: N-acetylcysteine (Unverricht-Lundborg); enzyme replacement (Gaucher). Causes: Unverricht-Lundborg, Lafora (PAS+ inclusions), Myoclonic Epilepsy with Ragged Red Fibers (MERRF), NCL, Sialidosis	Progressive neurological decline; wheelchair-dependent eventually; MERRF: maternal inheritance; Lafora: fatal by 3rd decade

Clinical Pearl — Dravet Syndrome Diagnosis Trap: First seizure in Dravet is often febrile hemiclonic status epilepticus in a previously normal infant, followed by vaccine-proximate seizures (not caused by vaccine — caused by fever from vaccination). Do not give CBZ, OXC, LTG, PHT — these worsen seizures and can precipitate SE. SCN1A mutation identified in ~80% (loss-of-function, de novo). Genetic testing is essential. Stiripentol (only drug specifically for Dravet) + VPA + clobazam triad is standard.

▶2.9 Anti-Seizure Medications (ASMs) — Pharmacology & Drug Profiles

Mechanisms of Action

Target	Mechanism	ASMs
Na+ channel block (fast inactivation)	Stabilize fast-inactivated state; reduce high-frequency firing	PHT, CBZ, LTG, OXC, ESL, ZNS, RFN
Na+ channel (slow inactivation)	Unique mechanism — enhance slow inactivated state; reduces persistent Na+ current	LCS (lacosamide)
Ca2+ channel (T-type)	Block low-voltage activated Ca2+ channels; reduce thalamo-cortical oscillations in absence	ETX, ZNS, VPA (partial)
Ca2+ channel (α2δ subunit)	Reduce Ca2+ influx at presynaptic terminal; reduce excitatory NT release; NOT for absence	GBP, PGB
GABA-A enhancement	BZD: ↑ Cl- channel opening frequency; Barbiturates: ↑ Cl- channel opening duration	BZD (LZP, DZP, MDZ, CLB), PHB
GABA reuptake inhibition	Block GAT-1 transporter → ↑ synaptic GABA	TGB (tiagabine)
GABA transaminase inhibition	Irreversible GABA-T inhibition → ↑ GABA levels	VGB (vigabatrin)
SV2A modulation	Synaptic vesicle protein 2A; modulates vesicle exocytosis; reduces NT release during high-frequency firing	LEV, BRV (10× higher SV2A affinity)
AMPA receptor antagonism	Block glutamate AMPA receptors post-synaptically	PER (perampanel), TPM (partial), ZNS (partial)
Multiple targets	Na+, Ca2+, GABA↑, HDAC inhibition (VPA); Na+, Ca2+, GABA↑, CA inhibition, AMPA block (TPM)	VPA, TPM, ZNS, LTG

Key ASM Profiles — Board-Level Pharmacology

Drug	Mechanism	Dosing	PK	Key Side Effects	Contraindications / Avoid	Drug Interactions
Phenobarbital (PHB)	GABA-A: ↑ Cl- channel opening duration	Adult: 60–240 mg/d OD; Serum: 15–40 mg/L	t½ 72–144 h; bioavail 95%; protein binding 50%; hepatic + 25% renal	Sedation, memory impairment, fatigue, hyperactivity (children), depression; Dupuytren's contracture, frozen shoulder, plantar fibromatosis; pregnancy cat D	NOT effective for absence; sedation limits use	Strong CYP inducer (2B6, 2C, 3A4) → ↓ many drugs; renders other AEDs less effective
Phenytoin (PHT)	Na+ channel (fast inactivation state)	Adult: 200–400 mg/d BID-TID; Serum: 10–20 mg/L (free: 1–2 mg/L); IV loading: 15–20 mg/kg at ≤50 mg/min	t½ 9–40 h; zero-order kinetics at therapeutic doses; 90% protein bound; CYP2C9/2C19	Gingival hyperplasia, hirsutism, coarsening of facial features, acne, diplopia, ataxia (dose-related), nystagmus, SJS/TEN (HLA-B*1502 Asian population), peripheral neuropathy (chronic), osteoporosis, IV: hypotension + arrhythmia if too fast	NOT for absence, myoclonus, JME; avoid in IGE; avoid in Dravet	CYP inducer + substrate; many interactions; amiodarone/fluoxetine/INH/azoles ↑ PHT toxicity
Carbamazepine (CBZ)	Na+ channel (fast inactivation)	Adult: 400–1800 mg/d BID-TID; Serum: 4–12 mg/L	t½ 12–17 h (after autoinduction from 36 h); 75–85% bioavail; 75% protein bound; CYP3A4; autoinduction (4–6 weeks)	Hyponatremia (SIADH, especially elderly), diplopia, ataxia, drowsiness (dose-related), nausea, SJS/TEN (HLA-B*1502; screen Asian patients), aplastic anemia/agranulocytosis (rare), weight gain, teratogenicity	AVOID in IGE (absence, JME, Dravet) — worsens generalized SZ; AVOID in cardiac conduction disorders	Strong CYP3A4 inducer; ↓ OCP, warfarin, other AEDs; inhibits own metabolism initially then induces
Valproate/Valproic acid (VPA)	Multiple: Na+ channel, ↑GABA (GABA-T inhibit), T-type Ca2+ (partial), HDAC inhibition	Adult: 500–3000 mg/d BID-TID; Serum: 50–100 mg/L; SE: 20–40 mg/kg IV	t½ 9–16 h; ~100% bioavail; 90% protein bound; hepatic (β-oxidation, glucuronidation); enzyme INHIBITOR	Weight gain, tremor (dose-related), hair loss (alopecia, reversible), PCOS, menstrual irregularities, sedation, teratogenicity (NTD risk highest of all AEDs: spina bifida 1–2%, major congenital malformations 10%), hepatotoxicity (especially <2 yr), pancreatitis, thrombocytopenia, hyperammonemic encephalopathy	AVOID in women of childbearing age (teratogenicity); avoid in hepatic disease; use with caution in urea cycle disorders	Enzyme INHIBITOR: ↑ LTG levels (doubles LTG t½); ↑ PHB; ↑ carbapenems ↓ VPA significantly; drug-drug interactions extensive
Lamotrigine (LTG)	Na+ channel + ↓ glutamate/aspartate release	Adult: 200–400 mg/d BID; SLOW titration essential (risk SJS); Serum: 3–15 mg/L	t½ 24–35 h (alone); 7–10 h (+CBZ); 50–70 h (+VPA); 55% protein bound; glucuronidation (UGT1A4)	SJS/TEN (rapid titration, especially with VPA or in children); dizziness, headache, diplopia, insomnia; rash (10%); in JME: may worsen myoclonus at higher doses	Caution in JME (may exacerbate myoclonus at high doses); pregnancy: levels decrease significantly (↑ clearance → dose adjustment required)	VPA doubles LTG t½ → start at 25 mg QOD, titrate very slowly; CBZ halves LTG t½; OCP ↓ LTG 50%
Levetiracetam (LEV)	SV2A modulation	Adult: 1000–3000 mg/d BID; Serum: 12–46 mg/L	t½ 6–8 h; ~100% bioavail; <10% protein bound; 66% renal excretion unchanged; minimal hepatic metabolism	Irritability, aggression, mood changes, psychiatric disorders (~15%); somnolence, dizziness; safe in hepatic impairment; dose adjust in renal failure (GFR-based)	Psychiatric history: use with caution; add pyridoxine (B6) if behavioral SE in some protocols	Minimal DDI; no enzyme induction/inhibition; safe in complex polypharmacy
Oxcarbazepine (OXC)	Na+ channel (MHD active metabolite)	Adult: 900–2400 mg/d BID; Serum (MHD): 3–35 mg/L	t½ of MHD: 8–10 h; ~100% bioavail; 40% protein bound (MHD); renal excretion of glucuronide	Hyponatremia (SIADH, more common than CBZ; 25–30%); diplopia, ataxia, dizziness, headache; SJS (HLA-B*1502 cross-reactivity); less cognitive effects than CBZ	AVOID in IGE (same as CBZ); monitor Na+ especially elderly; cardiac conduction	Moderate CYP3A4 inducer; less interactions than CBZ; no autoinduction
Topiramate (TPM)	Multiple: Na+ channel, ↑GABA-A, AMPA/kainate block, CA inhibition, Ca2+ channel	Adult: 200–400 mg/d BID; Serum: 5–20 mg/L; cognitive effects dose-dependent	t½ 19–23 h; 80% bioavail; 15% protein bound; 70% renal unchanged; some hepatic	"Dopamax" cognitive impairment (word-finding, mental slowing — dose-related), kidney stones (CA inhibition → ↑ urine pH + ↓ citrate), weight loss, metabolic acidosis, hypohidrosis (children), glaucoma (acute closed-angle, rare), paresthesias	Cognitive burden limits use; kidney stone history (relative); avoid in metabolic acidosis	Moderate enzyme inducer; ↓ OCP efficacy (use barrier method); ↑ PHT at high doses; VPA combination → hyperammonemia
Lacosamide (LCS/LCM)	Na+ channel (slow inactivation — unique, complementary to fast-inact blockers)	Adult: 200–400 mg/d BID; Serum: 10–20 mg/L; IV: 200–400 mg over 15 min	t½ 13 h; ~100% bioavail; <15% protein bound; 40% renal; CYP2C19 minor	Dizziness, diplopia, nausea, headache; cardiac: PR interval prolongation (avoid in 2nd/3rd degree AV block, SSS); atrial fibrillation/flutter (rare)	Cardiac conduction disorders; caution with other PR-prolonging drugs	Minimal DDI; no enzyme induction/inhibition; excellent tolerability; IV formulation useful in SE
Ethosuximide (ETX)	T-type (low-voltage activated) Ca2+ channel block in thalamus	Adult/child: 500–1500 mg/d BID-TID; Serum: 40–100 mg/L	t½ 40–60 h (adults), 30 h (children); ~100% bioavail; low protein binding; hepatic CYP3A4	GI (nausea, vomiting, anorexia — start low/slow); headache, hiccups, lethargy; rare: blood dyscrasias, SLE-like syndrome	Absence seizures ONLY; no efficacy for GTC or focal; if patient also has GTC → add VPA or LTG	Moderate DDI; VPA ↑ ETX levels; PHT ↓ ETX
Zonisamide (ZNS)	Na+ channel + T-type Ca2+ + carbonic anhydrase inhibition	Adult: 200–600 mg/d OD; Serum: 10–40 mg/L	t½ 50–68 h; 40–60% bioavail; 50% protein bound; hepatic CYP3A4 (significant inducer effect)	Cognitive effects (less than TPM), anorexia/weight loss, kidney stones (CA), somnolence, word-finding difficulty, metabolic acidosis, oligohidrosis (children), rash; sulfonamide allergy (caution)	Sulfonamide allergy; renal stones history	CYP3A4 inducers ↓ ZNS significantly; moderate interactions
Clobazam (CLB)	1,5-benzodiazepine; GABA-A; less sedating than 1,4-BZD	Adult: 20–40 mg/d OD-BID; Child: 0.1–1 mg/kg/d	t½ of active metabolite (N-desmethylclobazam): 71–82 h; hepatic CYP2C19/3A4	Sedation, behavioral issues; tolerance develops with chronic use; withdrawal syndrome; teratogenicity risk	Caution in COPD/sleep apnea; tolerance limits long-term use as sole therapy	CYP2C19 inhibitors ↑ CLB; CBD (cannabidiol) ↑ CLB metabolite levels significantly
Brivaracetam (BRV)	SV2A (10× higher affinity than LEV); also Na+ channel at higher doses	Adult: 100–200 mg/d BID; IV formulation available	t½ 9 h; ~100% bioavail; ≤20% protein bound; hepatic CYP2C19	Fewer psychiatric side effects than LEV (irritability/aggression less common); somnolence, dizziness; nasopharyngitis	May be used when LEV psychiatric SE are problematic	CYP2C19 interaction; rifampin ↓ BRV; carbapenems may ↓
Perampanel (PER)	AMPA receptor antagonist (competitive, selective)	Adult: 8–12 mg/d QHS (titrate weekly by 2 mg); Serum: 180–990 ng/mL	t½ 70–110 h; 95–96% protein bound; hepatic CYP3A4	Dizziness, somnolence, headache; psychiatric: aggression/hostility/irritability (dose-dependent, BBW); falls	Psychiatric history; caution driving; aggression risk	Strong CYP3A4 inducers (CBZ, PHT, PHB) ↓ PER 50–67% → may need higher dose; ↓ OCP efficacy at ≥12 mg/d

ASM Seizure-Type Efficacy Matrix

ASM	Focal	GTC	Absence	Myoclonic	LGS	Notes
PHB	++	+	XX	+	—	Avoid absence
PHT	++	+	XX	XX	—	Avoid absence, myoclonus, IGE
CBZ	++	+	XX	XX	—	Avoid in ANY generalized epilepsy
VPA	++	++	++	++	+	Broad spectrum; avoid in women
ETX	—	—	++	—	—	Absence ONLY; not for GTC
LTG	++	++	+	+/−	++	May worsen myoclonus in JME (high dose)
LEV	++	++	+	++	—	Broad; renal excretion; minimal DDI
TPM	++	++	—	—	++	Cognitive burden; weight loss
ZNS	++	+	+	+	—	Broad; once-daily; long t½
LCS	++	—	−	−	—	Focal adjunctive; unique MOA (slow Na)
GBP/PGB	++	—	—	—	—	Focal only; NOT for generalized; analgesic too
CLB	+	+	+	+	++	Adjunctive; tolerance; LGS (drop attacks)
PER	++	++	—	—	—	AMPA blocker; psychiatric SE; QHS dosing

ILAE Evidence-Based Efficacy Review (Marson 2013, Epilepsia)

Indication	Level A	Level B	Level C
Adult partial-onset (focal) SZ	CBZ, LEV, PHT, ZNS	VPA	GBP, LTG, OXC, PHB, TPM
Elderly adults — partial-onset SZ	GBP, LTG	—	CBZ
Adults — GTC	—	—	CBZ, LTG, OXC, PHB, PHT, TPM, VPA
Children — absence SZ	VPA	—	LTG
BECT (Rolandic)	—	—	CBZ, VPA
Juvenile myoclonic epilepsy	—	—	—

Clinical Pearl — VPA + LTG Interaction (Critical DDI): Valproate is a strong UGT1A4 inhibitor → doubles LTG half-life (from 24 h to 50–70 h). When adding LTG to a patient ON VPA: start at 25 mg every other day × 2 weeks, then 25 mg daily × 2 weeks (extremely slow titration). Failure to do so → toxic LTG levels → SJS/TEN. Conversely, if VPA is stopped in a patient stabilized on LTG+VPA → LTG levels will DOUBLE → toxicity; reduce LTG dose by ~50%.

▶2.10 Treatment Selection, Stopping ASMs & Polytherapy

When to Start ASM — Decision Framework

Scenario	Recommendation	Rationale
2nd unprovoked seizure (epilepsy confirmed)	Start ASM	76% risk of 3rd seizure; treating established epilepsy reduces harm
1st unprovoked SZ + high-risk features (epileptiform EEG, MRI abnormality, prior brain injury, nocturnal SZ)	Consider starting ASM (shared decision)	≥60% recurrence risk → meets practical epilepsy definition
1st provoked seizure only	Treat underlying cause; ASM usually NOT needed long-term	Provoked SZ does not indicate epilepsy; metabolic correction
Epilepsy syndrome diagnosed	Start syndrome-appropriate ASM	Syndrome-specific therapy optimizes efficacy; avoids harm (e.g., CBZ in JME)

When to Stop ASM — Criteria

Criterion	Consideration
Seizure-free ≥2 years (most guidelines)	Can consider withdrawal in adults; risk of recurrence ~30–40% within 2 years of stopping
Seizure-free ≥1 year + favorable factors	Children: normal EEG, normal MRI, single SZ type, good response; some syndromes (BECT) can stop earlier
Factors that INCREASE recurrence risk after stopping	Abnormal EEG (epileptiform), structural etiology, multiple SZ types, focal epilepsy, longer history before control, IGE (especially JME) — 78% relapse after stopping
JME specific	Lifelong ASM almost always required; 78% relapse even after years seizure-free
Driving considerations	Withdraw ASM only during non-driving period; counsel patient about risk

Rational Polytherapy

Principle	Rationale	Examples
Complementary mechanisms (synergistic)	Two different MOA → potentially additive/synergistic; avoid same-class duplication	Na+ blocker + SV2A (CBZ + LEV); Na+ blocker + GABA-ergic (LTG + VPA); VPA + LTG (broad spectrum combo)
Avoid pharmacokinetic antagonism	Two enzyme inducers together may severely ↓ levels of both	Avoid CBZ + PHT together (competing induction); avoid adding inducer to stable regimen without level monitoring
Rational combinations for focal epilepsy	1st: CBZ/LTG/LEV/OXC → failure → add different MOA	LTG + LEV (different MOA: Na+ + SV2A); LTG + LCS (fast + slow Na inactivation); VPA + LTG (but ↑LTG toxicity risk)
Rational combinations for IGE	VPA + LTG (most studied broad-spectrum combo); LEV + LTG; LEV + VPA	VPA + LTG: excellent for JME, JAE; VPA + LEV: good evidence; ETX + VPA: for absence + GTC
Combinations to AVOID	Pharmacodynamic or PK incompatibility; worsening	CBZ + PHT (↑ neurotoxicity); PHT + PHB (sedation); VPA + TPM (↑ hyperammonemia); CBZ in IGE with any AED

▶2.11 Special Populations

Women of Childbearing Age & Pregnancy

Reference: Tomson T, et al. ILAE Task Force. "Management of epilepsy in pregnancy." Epileptic Disorders 2019 (ILAE). EURAP International Registry data.

Issue	Key Points	Recommendation
Teratogenicity risk	VPA highest risk: major congenital malformations (MCM) 10–11%, NTD (spina bifida) 1–2%, neurodevelopmental effects (cognitive impairment, autism); dose-dependent. LTG: MCM ~2% (similar to background); LEV: MCM ~2%; PHT, PHB: MCM ~5–6%; TPM: oral clefts ↑; OXC: MCM ~3%	AVOID VPA in women who may become pregnant if alternatives exist. Preferred: LTG, LEV (lowest risk). Folic acid 5 mg/day periconceptionally for ALL women on ASM
Hormonal contraception interactions	Enzyme inducers (CBZ, PHT, PHB, OXC, TPM at high dose, PER at ≥12 mg) ↓ OCP efficacy → breakthrough pregnancy. LTG: OCP ↓ LTG 50% (use higher dose or IUCD)	Use non-hormonal contraception (IUCD, barrier) with enzyme-inducing AEDs; OR switch to non-inducing AED. If using OCP: use ≥35 µg ethinylestradiol; monitor LTG levels
Seizure frequency during pregnancy	Most women (50–80%) remain stable; 15–30% worsen (sleep deprivation, medication changes, levels drop); levels of LTG, LEV, OXC/MHD decrease significantly during pregnancy due to ↑ renal clearance/volume of distribution	Monitor drug levels every trimester; increase dose if breakthrough seizures; postpartum: reduce dose to prevent toxicity (levels rebound)
Vitamin K / folic acid	Enzyme-inducing AEDs → vitamin K deficiency → neonatal hemorrhage; VPA + some others → folate deficiency	Folic acid 5 mg/day from pre-conception to 12 weeks; Vitamin K 10–20 mg/day in last month for women on enzyme inducers
Breastfeeding	Generally safe for most ASMs; LTG, LEV, VPA low transfer in breast milk; PHB/PHT/BZD: sedation in infant possible; ETX: high transfer → monitor infant	Breastfeeding encouraged; observe infant for sedation; bottle-feed if concern

Elderly Patients with Epilepsy

Issue	Key Points
Most common new-onset epilepsy cause	Cerebrovascular disease (#1); tumors; Alzheimer's/dementia; trauma; cryptogenic
Preferred ASMs (ILAE Level A)	GBP and LTG for partial-onset SZ in elderly; LTG better tolerated; LEV also well-tolerated with good tolerability profile
Avoid	PHT (osteoporosis, cardiac conduction, drug interactions); PHB (sedation, falls, cognitive impairment, Dupuytren's); CBZ (hyponatremia/SIADH, interactions with warfarin)
Pharmacokinetic considerations	↓ renal clearance → adjust LEV, GBP, OXC, LCS doses; ↓ albumin → ↑ free PHT fraction (interpret total levels cautiously); CYP interactions more dangerous with polypharmacy
Falls risk	All CNS-active AEDs increase fall risk; minimize sedating AEDs; single agent preferred; treat comorbid osteoporosis

▶2.12 Drug-Resistant Epilepsy & Surgical Evaluation

Key Trial: Wiebe S, et al. "A randomized, controlled trial of surgery for temporal-lobe epilepsy." N Engl J Med 2001;345:311–318. — Surgery (ATL) vs. continued medical therapy in drug-resistant MTLE: 58% seizure-free post-surgery vs. 8% medical; significant QoL improvement.

Definition & Approach to Drug-Resistant Epilepsy

Drug-resistant epilepsy (ILAE 2010): Failure of adequate trials of ≥2 tolerated, appropriately chosen and used AED schedules (monotherapy or in combination) to achieve sustained seizure freedom.

~30% of patients with epilepsy are drug-resistant. Most patients who will become drug-resistant do so within the first 2 years of treatment; if 2 AEDs fail → probability of seizure freedom with further drugs falls to <5%.

Presurgical Evaluation

Step	Evaluation	Purpose
1. Phase I (Non-invasive)	Video-EEG monitoring (seizure capture); 3T MRI epilepsy protocol; neuropsychological testing	Define seizure semiology, localize EEG onset, identify structural lesion, baseline cognitive mapping
2. Functional MRI (fMRI)	Language and memory lateralization	Map eloquent cortex; Wada test (IAP) if fMRI inconclusive
3. FDG-PET	Interictal hypometabolism; concordant with EEG and MRI zone	Increases confidence when MRI negative; localize epileptogenic zone
4. SPECT (Ictal/Interictal)	Ictal SPECT: SISCOM analysis (subtraction ictal SPECT co-registered to MRI)	Localize seizure onset when MRI negative or discordant
5. MEG	Magnetoencephalography; dipole source analysis	Localize interictal epileptiform discharges; eloquent cortex mapping
6. Phase II (Invasive EEG)	Stereo-EEG (SEEG) or subdural grid/strip electrodes	When Phase I concordance insufficient; map epileptogenic network; test resection safety

Surgical Options for Epilepsy

Procedure	Indication	Seizure-Free Rate
Anterior temporal lobectomy (ATL)	Drug-resistant MTLE with hippocampal sclerosis	~70% seizure-free at 1 year; ~60–65% at 5 years
Lesionectomy / focal cortical resection	Focal lesion (FCD, cavernoma, low-grade tumor) concordant with seizure onset	~60–80% (lesional > non-lesional)
Corpus callosotomy	Drop attacks (atonic/tonic SZ) in LGS; bilateral synchrony interruption	~50–75% reduction in drop attacks; rarely seizure-free
Hemispherectomy / hemispherotomy	Unilateral hemispheric pathology (Rasmussen, hemimegalencephaly, large porencephaly)	~60–80% seizure-free; requires contralateral hemispheric compensation
Vagus nerve stimulation (VNS)	Drug-resistant focal epilepsy not amenable to resection; adjunctive	~50% responders (≥50% reduction); 5–10% seizure-free; benefit increases over time
Responsive neurostimulation (RNS)	Drug-resistant focal epilepsy; seizure detection + on-demand stimulation	~50% responders; 16% seizure-free at 9 years
Deep brain stimulation (DBS)	ANT-DBS (thalamic nucleus anterior): drug-resistant focal; SANTE trial	~40% reduction; 17% seizure-free at 5 years; progressive benefit
Ketogenic diet	Drug-resistant pediatric epilepsy; LGS, Dravet, GLUT-1 deficiency (1st line)	~50% with ≥50% reduction; ~10–15% seizure-free in refractory epilepsy

Clinical Pearl — Refer Early for Surgical Evaluation: The major mistake in drug-resistant epilepsy management is waiting too long before surgical referral. After 2 AED failures → refer for presurgical evaluation (ILAE recommendation). Only 3–5% chance of a 3rd, 4th, or 5th drug working. The Wiebe NEJM 2001 trial showed 58% seizure-free with surgery vs. 8% with medications in drug-resistant MTLE — this transforms patients' lives. Drug-resistant MTLE with unilateral hippocampal sclerosis = the best surgical candidate.

▶2.13 Status Epilepticus — Definition, Classification & Staged Treatment

Key References:

Trinka E, et al. "A definition and classification of status epilepticus." Epilepsia 2015;56(10):1515–1523. (ILAE Task Force)
ESETT Trial — Kapur J, et al. "Randomized Trial of Three Anticonvulsant Medications for Status Epilepticus." N Engl J Med 2019;381:2103–2113.
RAMPART Trial — Silbergleit R, et al. "Intramuscular versus Intravenous Therapy for Prehospital Status Epilepticus." N Engl J Med 2012;366:591–600.

SE Definition — ILAE 2015 (Trinka)

"SE is a condition resulting either from the failure of the mechanisms responsible for seizure termination, or from the initiation of mechanisms which lead to abnormally prolonged seizures (after time point t₁). It is a condition that can have long-term consequences (after time point t₂), including neuronal death, neuronal injury, and alteration of neuronal networks."

SE Type	t₁ (treat)	t₂ (long-term consequences)
Generalized convulsive SE (GCSE)	5 minutes	30 minutes
Focal SE with impaired consciousness	10 minutes	>60 minutes
Absence SE	10–15 minutes	Unknown

SE stages: Early/Impending (0–30 min) → Established (30–60 min) → Refractory SE (RSE, >60 min) → Super-refractory SE (SRSE, >24 h despite anesthetics, or recurrence on anesthetic weaning)

Classification of SE (Trinka 2015)

Category	Subtypes	Key Features	Mortality
SE with prominent motor phenomena (SE-PM)	Convulsive (GCSE, focal onset → bilateral); Myoclonic (with/without coma); Focal motor (Jacksonian, EPC, adversive); Tonic SE; Hyperkinetic SE	Clinically obvious; most common; GCSE = neurological emergency; EPC (epilepsia partialis continua): continuous focal motor activity, may be very prolonged	SE-PM overall: ~10%; convulsive only → 0% (if treated); convulsive evolving to nonconvulsive: 23–40%
Non-convulsive SE (NCSE)	NCSE with coma (subtle SE); NCSE without coma: generalized (typical/atypical/myoclonic absence status); focal (aura continua, aphasic, with/without LOC); unknown (autonomic SE)	Clinically silent (coma or subtle behavior change); EEG essential for diagnosis; often missed; higher morbidity than convulsive in some forms; absence SE: treated aggressively with IV BZD; twilight state in elderly = absence SE until EEG disproves	NCSE overall: ~27.6%; NCSE coma: 43–60%

Etiology of SE — Prognostic Impact

Etiology	% of Adult SE Cases	Mortality
Low/subtherapeutic AED levels	34% (most common in known epilepsy)	4%
Remote (prior brain injury)	25%	14%
Cerebrovascular accident (CVA)	22%	33%
Anoxia/Hypoxia	5–7%	53–71% (worst prognosis)
CNS infection	3%	~0–10%
Tumor (CNS)	7%	30%
Metabolic/toxic	15%	30%
Alcohol-related	13%	20%
Cryptogenic/Unknown	~15%	~5%

Clinical Pearl — Etiology is the Most Important Prognostic Factor in SE: Anoxic SE has 53–71% mortality regardless of treatment. Low AED levels causing SE has only 4% mortality. Adult SE pooled mortality ~15.9% (Neligan 2019, JAMA Neurol); mortality has NOT improved significantly over 30 years despite better treatment protocols. Etiology MUST be identified and treated simultaneously with seizure control.

Staged Treatment Protocol for Generalized Convulsive SE

Stage	Time	Treatment	Drugs & Doses	Success Rate
Stabilization	0–5 min	ABC + supportive	Airway, O₂, IV access ×2; ECG monitoring; fingerstick glucose; if glucose <60 mg/dL → thiamine 100 mg IV then D50W 50 mL. Collect: electrolytes, Ca, Mg, BUN/Cr, LFT, CBC, toxicology screen, AED levels. Time seizure onset.	—
Stage I (Initial therapy)	5–20 min	Benzodiazepine — Level A evidence	1st choice (any one): • IM midazolam: 10 mg (>40 kg); 5 mg (13–40 kg) — RAMPART: IM = IV LZP • IV lorazepam: 0.1 mg/kg (max 4 mg/dose), may repeat once • IV diazepam: 0.15–0.2 mg/kg (max 10 mg), may repeat once 2nd BZD choices: • IV phenobarbital 15 mg/kg (if no IV access) • Rectal diazepam 0.2–0.5 mg/kg (max 20 mg) • Intranasal/buccal midazolam	60–70% respond (30–40% fail)
Stage II (Second therapy / Established SE)	20–40 min	Second-line ASM — Level U (no clear preferred agent)	Choose ONE of (give as single loading dose): • IV Fosphenytoin: 20 mgPE/kg (max 1500 mgPE) IV ≤150 mgPE/min • IV Valproate: 40 mg/kg (max 3000 mg) IV over 10 min • IV Levetiracetam: 60 mg/kg (max 4500 mg) IV over 10 min • IV Phenobarbital: 15–20 mg/kg (if not given in Stage I) • IV Lacosamide: 400 mg IV over 15 min (adjunctive option) ESETT 2019 (NEJM): LEV 47% vs FOS 45% vs VPA 46% success — NO SIGNIFICANT DIFFERENCE	40–60% additional responders
Stage III (Refractory SE)	40–60+ min	Anesthetic agents — ICU; continuous EEG monitoring	Choose ONE (titrate to burst suppression pattern on EEG): • Midazolam infusion: 0.2 mg/kg bolus, then 0.05–2 mg/kg/h • Propofol infusion: 1–2 mg/kg bolus, then 2–10 mg/kg/h (PRIS risk with high dose/long use) • Thiopental: 100–250 mg bolus, then 1–5 mg/kg/h • Pentobarbital: 5–15 mg/kg loading, then 0.5–10 mg/kg/h	Variable; high morbidity
Stage IV (Super-refractory SE >24h)	>24 h	SRSE — experimental options + immune therapy	• Ketamine: 1–2 mg/kg bolus, then 0.6–10 mg/kg/h (NMDA antagonist; benefit in prolonged SE) • Magnesium sulfate: 4 g bolus then 2–6 g/h • Immunotherapy: methylprednisolone 1 g/day ×7 days; IVIG 30 g ×3–5 days; plasmapheresis • Hypothermia: 32–35°C • Ketogenic diet (via NG tube) • Repeat second-line ASMs Consider NORSE/FIRES in young patients with unexplained super-refractory SE	Poor; mortality 30–50%

ESETT Trial — Key Results (NEJM 2019)

Kapur J, et al. NEJM 2019 — n=384 patients with benzodiazepine-refractory SE; randomized to LEV 60 mg/kg (max 4500 mg) vs FOS 20 mgPE/kg (max 1500 mgPE) vs VPA 40 mg/kg (max 3000 mg). Primary outcome: seizure control + improved alertness at 60 min.

Outcome	LEV	FOS (Phenytoin)	VPA
Seizure control at 60 min	47%	45%	46%
ICU admission	60%	59%	59%
Severe hypotension	0.7%	3.2%	1.6%
Cardiac arrhythmia	0.7%	0%	0%
Intubation	20%	26.4%	16.8%
Death	4.7%	2.4%	1.6%

Conclusion: No significant difference in efficacy between LEV, FOS, and VPA for established (BDZ-refractory) SE. All three are equally valid 2nd-line choices. Choose based on clinical context, availability, and safety profile (LEV: fewest cardiovascular SE; VPA: caution in hepatic disease/pregnancy; FOS: cardiac monitoring needed).

RAMPART Trial — IM vs IV BZD (NEJM 2012)

Silbergleit R, et al. NEJM 2012 — n=893 patients with prehospital SE; IM midazolam (10 mg) vs IV lorazepam (4 mg). Primary: seizure cessation before ED arrival.

IM midazolam: 73.4% seizure stopped | IV lorazepam: 63.4% seizure stopped (p<0.001)
Median time to treatment: IM 1.2 min vs IV 4.8 min (faster due to no IV placement)
Conclusion: IM midazolam is non-inferior (actually superior) to IV lorazepam for prehospital SE
Preferred when IV access unavailable; comparable safety

NORSE / FIRES

Term	Definition	Key Features	Treatment
NORSE (New Onset Refractory Status Epilepticus)	Super-refractory SE in a patient without a prior history of epilepsy and without clear acute or active structural/toxic/metabolic cause at onset (Hirsch 2018)	Usually young previously healthy adults; prodrome: fever/headache; rapidly deteriorates to RSE; ~50% autoimmune etiology (especially VGKC/LGI1/GABA-B/NMDAR); cryptogenic 50%	Aggressive anesthesia + immunotherapy (steroids → IVIG → PE); ketamine; ketogenic diet; early empiric immunotherapy if clinical suspicion; mortality 16–27%; persistent cognitive deficits common
FIRES (Febrile Infection-Related Epilepsy Syndrome)	NORSE with febrile illness 2 weeks to 24 hours before SE onset; seen in school-age children (peak 6–16 yr)	School-age children; febrile infection precedes by days–weeks; refractory focal SE; EEG: continuous bitemporal activity; MRI may be normal initially then shows mesial temporal changes; autoimmune etiology uncertain; IL-1 pathway implicated	Standard SE treatment ± immunotherapy; ketogenic diet shows promising results in FIRES; anakinra (IL-1 receptor antagonist) — emerging evidence; mortality 12%; majority have drug-resistant epilepsy afterwards; severe cognitive outcome

▶2.14 SUDEP, Autoimmune Epilepsy & Key Comorbidities

Sudden Unexpected Death in Epilepsy (SUDEP)

Feature	Details
Definition	Sudden, unexpected, witnessed or unwitnessed, non-traumatic, non-drowning death in a patient with epilepsy, with or without evidence of a seizure, excluding documented SE, with postmortem examination showing no toxicological or anatomical cause of death
Incidence	~1.16/1000 patient-years overall; 3.3–9.3/1000 in drug-resistant epilepsy; 15–20× higher risk in Dravet syndrome; 0.09–0.35/1000 in well-controlled epilepsy
Risk factors	GTC seizures (especially nocturnal) — single most important risk factor; drug-resistant epilepsy; young adults (20–40 yr); male sex; prone sleeping position; alcohol use; polypharmacy; subtherapeutic AED levels; nocturnal unmonitored seizures
Pathophysiology	Post-ictal cardiorespiratory failure; postictal generalized EEG suppression (PGES) → brainstem dysfunction → apnea, cardiac arrhythmia; serotonergic pathway disruption; autonomic dysregulation
Prevention	Optimize seizure control (most important); avoid prone sleeping; nighttime monitoring/supervision; seizure detection devices; address modifiable risk factors; seizure alert dogs

Autoimmune Epilepsy

Reference: Smith G, et al. "Autoimmune seizure disorders." Continuum 2024; Hirsch LJ, et al. "Autoimmune epilepsy." Review 2022.

Antibody	Syndrome	Seizure Type	Key Clinical Features	Treatment
NMDAR-Ab	Anti-NMDAR encephalitis	Focal, multifocal, GTC; SE common	Young women; psychiatric prodrome → seizures → movement disorders → catatonia; ovarian teratoma (~40% women); CSF pleocytosis	1st: steroids + IVIG; 2nd: rituximab/cyclophosphamide; tumor removal if teratoma
LGI1-Ab	LGI1 encephalitis (limbic encephalitis)	FBDS (faciobrachial dystonic seizures — pathognomonic); temporal lobe SE	Middle-aged men; hyponatremia; amnesia; frontotemporal dementia phenotype; FBDS precede encephalitis	Steroids ± IVIG; EARLY treatment of FBDS prevents limbic encephalitis; ASMs have limited effect on FBDS
CASPR2-Ab	CASPR2 encephalitis / Morvan syndrome	Temporal and frontal focal SE	Older men; Morvan: peripheral nerve hyperexcitability + insomnia + CNS; thymoma association	Immunotherapy; thymoma resection
GABA-B-Ab	GABA-B encephalitis	Temporal lobe SE; often refractory	Middle-aged/elderly; severe seizures early; amnesia; SCLC association (~50%)	Immunotherapy; treat underlying tumor
GAD65-Ab	Limbic encephalitis / Stiff-person spectrum	Temporal lobe focal SE; drug-resistant	Women; intracellular antigen → poor immunotherapy response; DM-1 associated; stiff-person spectrum	Immunotherapy often insufficient; symptomatic; GABAergic ASMs (diazepam, baclofen for stiffness)

Clinical Pearl — FBDS and LGI1: Faciobrachial dystonic seizures (FBDS) are the single most clinically distinctive feature of LGI1 autoimmune encephalitis. They are brief (<3 s) unilateral arm ± face dystonic/tonic posturing, occurring >100×/day, with preservation of consciousness. ASMs are largely ineffective. Treat with immunotherapy (steroids ± IVIG) as soon as FBDS diagnosed — this prevents the subsequent development of limbic encephalitis and cognitive decline. Also associated with hyponatremia (SIADH). LGI1-Ab positive in serum (most sensitive) and CSF.

Common Comorbidities in Epilepsy

Comorbidity	Prevalence	Clinical Notes
Depression	~30–35% (highest in MTLE)	Bidirectional relationship; depression → ↑ seizure risk; shared serotonergic/GABA pathways; SSRIs safe (avoid bupropion which lowers seizure threshold); screen all epilepsy patients
Anxiety	~25%	Peri-ictal anxiety common; distinguish seizure aura of fear from generalized anxiety; treat with SSRI/SNRI
Cognitive impairment	~20–40% (especially TLE, LGS)	Seizure burden, ASM effects (PHT, PHB worst; LTG/LEV best tolerated); memory loss in MTLE; progressive in PME; baseline neuropsychological testing important
Sleep disorders	~40–50%	Obstructive sleep apnea worsens seizure control; treat OSA; nocturnal seizures disturb sleep architecture; LEV/LTG may worsen insomnia
Osteoporosis	↑ with enzyme-inducing AEDs	CBZ, PHT, PHB → ↑ CYP metabolism of vitamin D → ↓ Ca absorption → ↓ BMD; supplement Ca + Vit D; DEXA scan for long-term users of enzyme inducers

3. Movement Disorders

Movement disorders encompass hypokinetic syndromes (Parkinson's disease, atypical parkinsonism) and hyperkinetic syndromes (tremor, dystonia, chorea, myoclonus, tics). This section covers diagnosis, pharmacotherapy, motor complications, advanced therapies, and movement disorder emergencies at subspecialist depth, integrating MDS 2015 diagnostic criteria and 2024 treatment guidelines.

3.1 Movement Classification & Phenomenology

Basal Ganglia Anatomy & Circuits (Poewe, Nat Rev Dis Primers 2017)

Input nuclei: Striatum (caudate + putamen) and subthalamic nucleus (STN)

Output nuclei: Globus pallidus interna (GPi) and substantia nigra pars reticulata (SNr) → inhibitory (GABA) → thalamus

Intrinsic: Globus pallidus externa (GPe), STN

Modulatory: Substantia nigra pars compacta (SNpc) — dopaminergic; Raphe — serotonergic; Locus ceruleus — noradrenergic

Pathway	Neurons	Effect on GPi/SNr	Net motor effect
Direct (Go)	D1-MSN → GABA/SP → GPi/SNr	↓ Inhibition	↑ Movement facilitation
Indirect (NoGo)	D2-MSN → GABA/ENK → GPe → STN → GPi/SNr	↑ Inhibition	↓ Movement suppression
Hyperdirect	Motor cortex → STN directly → GPi	↑↑ Inhibition (fast)	Emergency brake

Dopamine balance: SNpc DA → ↑D1 (direct, facilitatory) and ↓D2 (indirect, inhibitory) → net movement promotion. Loss of SNpc DA → hypokinesia (Parkinsonism)

Abnormal Movement Classification (Fahn 2011)

Category	Subtypes	Key features
Hypokinesia	Parkinsonism	Bradykinesia, rigidity, rest tremor, postural instability
Hyperkinesia — Rhythmic	Tremor	Regular oscillatory; see tremor classification
	Myoclonus	Sudden brief muscle jerk; rhythmic or arrhythmic
	Hyperkinesia — Non-rhythmic: Shock-like	Tics (suppressible + urge)	Semi-voluntary; waxing/waning; premonitory urge
		Myoclonus (non-suppressible)	No urge; not suppressible


Hyperkinesia — Non-rhythmic: Random	Chorea / Ballism / Athetosis	Flow-like → violent flinging → writhing; distal→proximal
Hyperkinesia — Non-rhythmic: Sustained repetitive	Dystonia	Sustained/intermittent contraction; patterned twisting; alleviating maneuver

3.1.1 Tremor

Tremor Classification (Bhatia, Mov Disord 2018)

Rest tremor: Present at rest, suppressed by action. Classic: Parkinson's disease 4–6 Hz

Active tremors:

Postural: Maintained against gravity (arms outstretched). ET predominantly postural (but kinetic-dominant)
Kinetic: During movement
- Simple kinetic: occurs throughout movement
- Intention/terminal (cerebellar): worsens as target approached
- Task-specific: writing tremor, embouchure tremor
Isometric: During muscle contraction against fixed object

Wing-beating tremor: Arms abducted 90° at shoulder — pathognomonic of Wilson's disease (Holmes/rubral tremor at rest+postural+kinetic)

Tremor Frequency & Clinical Correlations

Tremor type	Frequency (Hz)	Key characteristics	Diagnosis clue
Essential Tremor (ET)	4–12	Kinetic >> postural; hands > head/voice	Improved by alcohol; FH+
Parkinsonian	4–6	Rest++; re-emergent postural; "pill-rolling"	Pill-rolling; unilateral onset
Cerebellar	2–4	Intention/terminal; dysmetria; truncal	Ataxia, nystagmus, scanning speech
Holmes/Rubral	1–4	Rest + postural++ + kinetic++ (all 3)	Midbrain/red nucleus lesion
Orthostatic	12–16	Legs only; worse standing; feels like unsteadiness	High freq EMG; resolves with walking
Dystonic	1–6	Irregular; associated abnormal posture	Geste antagoniste; task-specific
Physiologic	8–12	Exaggerated by anxiety, caffeine, thyroid	No functional disability; bilateral

Re-emergent tremor: Parkinsonian tremor appears after 5–10 sec in outstretched position (same frequency as rest tremor 4–6 Hz), distinguishing it from ET which appears immediately (postural tremor). This re-emergence is due to dopaminergic deficiency — critical for board exams.

3.1.2 Myoclonus (Fahn, 2011)

Definition: Involuntary sudden rhythmic or arrhythmic brief muscle movement (positive) or sudden inhibition (negative = asterixis = "flapping tremor").

Activation: Rest, posture, movement → positive or negative myoclonus

Stimulus-sensitivity: Tactile, auditory, visual (cortical myoclonus)

Myoclonus Classification by Origin

Type	Origin	Features	Examples
Cortical	Motor cortex	Focal/multifocal; stimulus-sensitive; EEG: cortical correlate	Post-anoxic (Lance-Adams), progressive myoclonic epilepsies
Subcortical	Thalamus/BG	Generalized; less stimulus-sensitive	Essential myoclonus, Huntington's
Brainstem	Brainstem	Generalized or reticular; exaggerated startle	Hyperekplexia
Spinal	Spinal cord	Segmental or propriospinal	Spinal cord injury, myelitis
Peripheral	Nerve/muscle	Hemifacial spasm, hemimastication	Facial nerve compression

Negative myoclonus (asterixis): Sudden lapse of sustained posture (not a tremor despite "flapping" appearance). Seen in metabolic encephalopathy (hepatic, renal, CO2 retention), drug toxicity (anticonvulsants, lithium). Bilateral asterixis → metabolic; Unilateral → contralateral structural (thalamus/cortex).

3.1.3 Tics & Tourette Syndrome (Jankovic, NEJM 2001)

Definition: Semi-voluntary/involuntary brief waxing and waning stereotyping movements (motor) or sounds (phonic); characterized by premonitory urge and suppressibility (with rebound — "tic flurries").

Tic Classification

Type	Simple	Complex
Motor	Blinking, nose twitching, head jerking	Head shaking, trunk bending, jumping, copropraxia, echopraxia
Phonic	Sniffing, throat clearing, coughing, blowing, screaming	Verbalization, coprolalia, echolalia, palilalia

Tourette syndrome: ≥2 motor tics + ≥1 phonic tics (not necessarily simultaneous); onset <18 years; duration >1 year. Comorbidities: ADHD (50–60%), OCD (40–60%), behavioral/impulse control disorders.

Adult-onset tics MUST be worked up (secondary causes): Infections (encephalitis, CJD, neurosyphilis, Sydenham's chorea); Drugs/Tardive tics (amphetamine, cocaine, phenytoin, CBZ, phenobarbital, lamotrigine, antipsychotics, dopamine receptor blockers); Toxin (CO); Developmental (autism, static encephalopathy); Chromosomal (Down, Klinefelter, Fragile X); Others: head trauma, stroke, neurodegenerative diseases. (Joseph J, NEJM 2001)

3.1.4 Chorea, Ballism & Athetosis

Chorea-Ballism-Athetosis Spectrum Comparison

Feature	Athetosis	Chorea	Ballism
Quality	Slow writhing (piano-like fingers)	Flow-like, random, dancing	Violent flinging
Distribution	Distal (fingers, toes)	Distal > proximal	Proximal (shoulder, hip)
Amplitude	Small	Medium	Large
Speed	Slow	Moderate	Fast
Suppressibility	Parakinesia (incorporated)	Partial (parakinesia)	None

Chorea key features: Motor impersistence (tongue "jack-in-the-box," milkmaid grip); parakinesia (involuntary movements incorporated into purposeful acts). Causes: Huntington's, Sydenham's, SLE/antiphospholipid, hyperglycemia (nonketotic → hemiballism), drugs (levodopa, OCP, anticonvulsants, cocaine), toxoplasmosis (involving BG).

Hemiballism: Most common cause = contralateral STN lesion (lacunar infarct in hypertensive patient). Also: hyperglycemia (hemiballism/hemichorea from putaminal T1 hyperintense lesion). Usually self-limiting (weeks–months).

Athetosis: Classic in children with cerebral palsy (double athetosis). In adults: rule out pseudoathetosis (proprioceptive loss — fingers move when eyes closed due to sensory deafferentation).

3.1.5 Dystonia

Definition (Albanese 2013): Involuntary sustained or intermittent muscle contractions causing abnormal, often repetitive movements, postures, or both. Movements are typically patterned and twisting, and may be tremulous. Dystonia is often initiated or worsened by voluntary action and associated with overflow muscle activation.

Dystonia Classification (Albanese, Mov Disord 2013)

Axis I — Clinical Characteristics:

Feature	Options
Age of onset	Infancy (<2y), childhood (2–12y), adolescence (13–20y), early adult (21–40y), late adult (>40y)
Body distribution	Focal, segmental, multifocal, generalized, hemidystonia
Temporal pattern	Disease course (stable/progressive), variability (persistent/action/diurnal/paroxysmal)
Associated features	Isolated vs combined (+ other movement disorders); neurological/systemic features

Axis II — Etiology: Inherited (DYT-TOR1A, DYT-THAP1, DYT-GCH1, etc.) vs Acquired (structural, medication-induced, etc.) vs Idiopathic

Key dystonia phenomena:

Geste antagoniste (sensory trick): Touch/pressure to an adjacent body area reduces dystonia. Classic in cervical dystonia (90%).
Action dystonia: Triggered or worsened by specific voluntary movement
Task-specific dystonia: Writer's cramp, musician's focal dystonia
Overflow: Dystonia spreads to adjacent muscles not intended
Mirror dystonia: Contralateral limb develops dystonia when ipsilateral limb performs task

Dystonia diagnostic pearl: When evaluating new dystonia, especially young-onset, always check Wilson's disease — serum ceruloplasmin (low), slit-lamp for Kayser-Fleischer rings, 24-hour urine copper. "DYT" genes: TOR1A (DYT1) = childhood-onset generalized; GCH1 (DYT5) = Dopa-responsive dystonia (diurnal fluctuation, dramatic response to levodopa, mimics CP).

Other Hyperkinetic Movement Disorders (Fahn 2011)

Akathisia: Feeling of inner restlessness, need to move; caused by dopamine receptor blockers. Not truly a movement disorder per se but often misdiagnosed.

Stereotypy: Repetitive, coordinated, purposeless movement; seen in autism, tardive stereotypy, Rett syndrome.

Restless Legs Syndrome (RLS/WED): Urge to move legs, worse at rest/night, relieved by movement; 5–15% prevalence; treat with DA agonists (pramipexole, ropinirole, rotigotine), iron supplementation (ferritin <75 μg/L).

Periodic limb movements in sleep (PLMS): Stereotyped limb movements during sleep; associated with RLS.

Peripheral hyperexcitability: Fasciculations (motor neuron disease, benign), myokymia (radiation, MS, GBS), cramps (dehydration, electrolyte, motor neuron disease), myotonia (chloride/sodium channelopathies).

References: Fahn S. Principles and Practice of Movement Disorders, 2nd ed, 2011. Bhatia KP et al. Consensus statement on the classification of tremors. Mov Disord 2018;33:75–87. Albanese A et al. Phenomenology and classification of dystonia. Mov Disord 2013;28:863–73. Jankovic J. Tourette's syndrome. NEJM 2001;345:1184–92.

3.1.6 Tone Assessment — Key Distinctions

Tone Classification for Boards

Tone type	Velocity-dependence	Character	Lesion
Spasticity	Velocity-dependent ↑	Clasp-knife (high velocity resistance then give)	Pyramidal/corticospinal tract
Rigidity	Velocity-independent ↑	Lead-pipe (equal throughout ROM)	Extrapyramidal/BG
Cogwheeling	Velocity-independent	Ratchet sensation = rigidity + tremor	Parkinsonism
Paratonia (Gegenhalten)	Variable/velocity-dependent	Resistance proportional to examiner force	Frontal lobe disease
Hypotonia	Decreased throughout	Flaccid, reduced deep tendon reflexes	Cerebellar, LMN, or infant

Q: What distinguishes re-emergent tremor from essential tremor on examination?

Re-emergent tremor (Parkinsonian) appears 5–10 seconds after assuming an outstretched posture, at the same frequency as the rest tremor (4–6 Hz). Essential tremor appears immediately upon assuming posture and has a higher frequency (5–12 Hz). Re-emergence is pathognomonic of dopaminergic deficiency and is suppressed by levodopa.

Q: A 35-year-old develops sudden onset of violent flinging movements of the right arm and leg. MRI shows a small left subthalamic nucleus infarct. What is the pathophysiology?

Hemiballism from left STN infarct. The STN normally excites (glutamate) the GPi → increased inhibition of thalamus. Loss of STN → decreased GPi activity → decreased inhibition of thalamus → excessive thalamo-cortical activation → violent proximal movements contralateral to lesion. Most cases from hypertensive lacunar infarction; self-limiting in weeks-months; treat with dopamine receptor blockers (haloperidol, clonazepam) if severe.

3.2 Parkinson's Disease — Diagnosis & Classification

PD Epidemiology (Dorsey, Lancet Neurol 2018)

Parameter	Data
Proportion of parkinsonism	~70% of all parkinsonism
Prevalence	0.3% general population; 1% over age 60; 3% over age 80
Mean age of diagnosis	55–60 years
Young-onset PD (YOPD)	<40 years; consider genetic (PARK2/Parkin, PINK1, DJ-1)
Juvenile-onset PD	<21 years; almost always genetic
Familial PD	10–15% of cases; LRRK2 most common AD (G2019S); GBA most common risk allele
Global burden projection	12.2M (2015) → 25.2M (2050) — "Parkinson Pandemic"

3.2.1 PD Pathophysiology

Core neuropathology: Loss of dopaminergic neurons in substantia nigra pars compacta (SNpc) + Lewy body accumulation (α-synuclein aggregates). Clinical symptoms appear when 50–60% of SNc dopaminergic cells are lost — explains long prodromal phase.

Braak staging of PD (Braak 2003):

Stage 1–2: Dorsal motor nucleus of vagus, olfactory bulb → hyposmia, autonomic dysfunction
Stage 3–4: Locus ceruleus, SNc → motor symptoms, RBD
Stage 5–6: Neocortex → dementia, hallucinations

Dopamine-BG imbalance: ↓SNpc DA → ↓D1 activation (less direct pathway) + ↓D2 inhibition (more indirect pathway) → net increase of GPi inhibitory output → thalamus suppressed → akinesia/bradykinesia.

Neurotransmitter deficiencies in PD: Dopamine (motor, NMS), Norepinephrine (orthostatic hypotension, depression), Serotonin (depression, anxiety), Acetylcholine (cognitive decline, hallucinations — targeted by rivastigmine). This multi-transmitter deficiency explains why levodopa alone has "unpredictable results" for tremor, postural instability, gait, and NMS.

3.2.2 Prodromal PD & Disease Course

PD Disease Trajectory (Kalia & Lang, Lancet 2015)

Phase	Duration	Key features
Prodromal (pre-motor)	2–5 years before Dx	Hyposmia (90%), RBD, constipation, depression, fatigue, sleep disturbance; autonomic dysfunction
Early motor	Years 1–3	Fatigue, pain, diplopia, asymmetric tremor/bradykinesia; honeymoon period — excellent levodopa response
Early-mid	Years 4–12	Anxiety, hypophonia, dysphagia, sleep fragmentation, falls begin; motor complications develop (3–5 years after starting levodopa)
Late	Year 8+	Dementia (PDD), cognitive dysfunction, hallucinations (dopaminergic therapy), incontinence, orthostatic hypotension; nursing home-level care

RBD as a prodromal biomarker: REM Sleep Behavior Disorder (RBD) — acting out dreams (violent behavior during REM sleep due to loss of REM atonia) — predicts PD/DLB/MSA in 80–90% over 10–15 years. This is the single strongest prodromal biomarker. Screen all RBD patients with DAT-SPECT. PSG confirmation: absent REM atonia.

3.2.3 PD Diagnosis Criteria

UK Parkinson's Disease Society Brain Bank (UKPDS) Criteria — Classic Board Criteria

Step 1 — Diagnosis of Parkinsonism: Bradykinesia PLUS at least one of:

Muscular rigidity
4–6 Hz rest tremor
Postural instability (not caused by primary visual, vestibular, cerebellar, or proprioceptive dysfunction)

Step 2 — Exclusion criteria (any = NOT PD): History of repeated strokes with stepwise progression; history of repeated head injury; definite encephalitis; oculogyric crises; MPTP exposure; neuroleptic treatment at onset; >1 affected relative; sustained remission; strictly unilateral >3 years; supranuclear gaze palsy; cerebellar signs; early severe autonomic involvement; early severe dementia; Babinski sign; CT evidence of tumor or communicating hydrocephalus; negative levodopa response

Step 3 — Supportive criteria (≥3 required for definite PD):

Unilateral onset
Rest tremor present
Progressive disorder
Persistent asymmetry affecting side of onset most
Excellent response to levodopa (70–100%)
Severe levodopa-induced dyskinesia
Levodopa response >5 years
Clinical course >10 years

MDS Clinical Diagnostic Criteria for PD (Postuma et al., Mov Disord 2015)

Essential criterion: Parkinsonism = bradykinesia + rest tremor OR rigidity

Absolute exclusion criteria (any one = NOT PD): Unequivocal cerebellar signs; downward supranuclear gaze palsy; behavioral variant FTD or primary progressive aphasia within first 5 years; parkinsonian features only in lower limbs >3 years; treatment with dopamine receptor blocker; absence of observable response to high-dose levodopa; unequivocal cortical sensory loss/apraxia/progressive aphasia; normal functional neuroimaging of dopaminergic system; documentation of alternative condition

Red flags (each reduces likelihood of PD):

Rapid progression requiring wheelchair within 5 years
Complete absence of progression over ≥5 years
Early bulbar dysfunction
Inspiratory respiratory dysfunction
Severe autonomic failure within first 5 years
Recurrent falls within 3 years
Disproportionate anterocollis or contractures within 10 years
Absence of any non-motor symptoms despite 5 years
Unexplained pyramidal tract signs
Bilateral symmetric parkinsonism

Supportive criteria: Clear and dramatic beneficial response to dopaminergic therapy; levodopa-induced dyskinesia; rest tremor of a limb; positive olfactory loss test OR cardiac MIBG scintigraphy showing denervation

Clinically established PD: No absolute exclusion criteria + no red flags + ≥2 supportive criteria OR only 1 red flag but ≥2 supportive criteria

Clinically probable PD: No absolute exclusion criteria + ≤2 red flags + ≥2 supportive criteria (one for each red flag)

3.2.4 Parkinsonism Classification

Parkinsonism Classification

Category	Diagnoses	Key distinguishing features
Idiopathic PD	Sporadic, Familial (LRRK2, SNCA, Parkin, PINK1, DJ-1, GBA)	Classic features, excellent levodopa response
Secondary	Vascular, Drug-induced, Infectious, Metabolic, Structural, Toxin (MPTP, CO, Mn)	History/exposure; drug-induced symmetric, no rest tremor
Atypical Parkinsonism	PSP, MSA, CBS, DLB	Red flags; poor/limited levodopa response
Heredodegenerative	Wilson's disease, Huntington's, SCA (SCA2, SCA3), NBIA	Young-onset; genetic testing; Wilson's always check in <50y

Red flags for atypical parkinsonism (McFarland, Continuum 2016):

Rapid progression (wheelchair in <3–5 years)
Early gait instability and falls within first year
Absence of tremor
Poor levodopa response (<30% improvement)
PSP-specific: Vertical supranuclear gaze palsy (downward), "surprised" facies, retrocollis, applause sign
MSA-specific: Severe early autonomic dysfunction (neurogenic OH ≥20/10 mmHg, urinary incontinence), cerebellar signs, inspiratory stridor
CBS-specific: Asymmetric cortical features — limb apraxia, alien limb phenomenon, cortical sensory loss, myoclonus
DLB-specific: Early dementia (within 1 year), fluctuating cognition, visual hallucinations, RBD (concurrent with or before parkinsonism)

3.2.5 Non-Motor Symptoms (NMS) of PD

PD Non-Motor Symptom Spectrum

Domain	Symptoms	Treatment
Autonomic	Orthostatic hypotension, sialorrhea, constipation, urinary urgency/retention, sweating abnormalities, seborrhea	Fludrocortisone/midodrine for OH; glycopyrrolate/botulinum for sialorrhea; macrogol for constipation
Neuropsychiatric	Depression (40%), anxiety (30%), psychosis/hallucinations (20–40%), apathy, impulse control disorder (DA agonists)	SSRIs (depression); quetiapine/clozapine (psychosis — avoid typical antipsychotics); rivastigmine (PDD)
Cognitive	MCI (25–40%), PDD (occurs in majority by 20 years), executive dysfunction, visuospatial	Rivastigmine (PDD, FDA-approved); memantine (mild benefit)
Sleep	RBD (60%), EDS (50%), insomnia, RLS/PLMS, sleep apnea	Clonazepam/melatonin (RBD); modafinil (EDS)
Sensory	Anosmia (90%, early), pain/cramping (40%), fatigue, akathisia, restless legs	Optimize dopaminergic therapy; gabapentin/pregabalin for pain
Other	Weight loss, dysphagia, drooling, seborrhoeic dermatitis	Speech therapy; BoNT for drooling

References: Hughes AJ et al. Accuracy of clinical diagnosis of idiopathic Parkinson's disease. JNNP 1992;55:181–4. Postuma RB et al. MDS clinical diagnostic criteria for Parkinson's disease. Mov Disord 2015;30:1591–1601. Kalia LV, Lang AE. Parkinson's disease. Lancet 2015;386:896–912. Braak H et al. Staging of brain pathology related to sporadic Parkinson's disease. Neurobiol Aging 2003;24:197–211.

Q: A 65-year-old man presents with 2-year history of right hand rest tremor, bradykinesia, and rigidity. He has had hyposmia for 5 years and constipation. He responds dramatically to levodopa. Which set of diagnostic criteria is best applied here, and what level of certainty is achieved?

Apply MDS 2015 criteria: Essential criterion met (bradykinesia + rigidity + rest tremor). No absolute exclusion criteria. No red flags. Supportive criteria: (1) rest tremor, (2) dramatic levodopa response, (3) hyposmia (olfactory loss). With ≥2 supportive criteria and no red flags = Clinically Established PD. Under UKPDS: Step 1 met; no exclusions; unilateral onset + rest tremor + progressive + levodopa response ≥70% + course >5 years = meets 5 supportive criteria = Definite PD by UKPDS.

Q: A 58-year-old woman is referred with 3-year history of parkinsonism. She has falls and needs a walker already. You note she cannot look downward voluntarily but can follow a moving target down. What is the diagnosis and what is this eye sign called?

Progressive Supranuclear Palsy (PSP) — Richardson syndrome. The eye sign is vertical supranuclear gaze palsy — voluntary downward gaze is lost but oculocephalic reflex (doll's eye) is preserved (because the supranuclear pathway, not the nucleus/brainstem itself, is affected). Hallmark of PSP. This plus early falls (<3 years), vertical gaze abnormality, bradykinesia, and axial rigidity = PSP. Poor levodopa response. MRI: "hummingbird sign" (midbrain atrophy on sagittal).

3.3 Pharmacotherapy of Parkinson's Disease

3.3.1 Levodopa — Gold Standard

Levodopa Pharmacology

Mechanism: Precursor to dopamine; crosses BBB via large neutral amino acid transporter (LNAAT). Amino acids from dietary protein compete for transport — hence food-drug interaction.

Must combine with peripheral DOPA decarboxylase inhibitor (DDCI): Carbidopa (in Sinemet) or benserazide (in Madopar/Vopar) — inhibits peripheral conversion of levodopa to dopamine, triples oral bioavailability, reduces peripheral dopaminergic side effects (N/V, OH).

Pharmacokinetics:

Fasting Tmax: 15–60 minutes; T½: 1–3 hours (short → motor fluctuations)
Food delays Tmax 2–3-fold; decreases Cmax by ~30%
Take 30–60 min BEFORE meals (or 2 hr after) on empty stomach for optimal absorption
HBS (Hydrodynamically Balanced System/Madopar HBS): bioavailability 50–70%, Tmax 2–4h, T½ 6–8h → smoother levels, less peak-dose dyskinesia

Most effective for: Bradykinesia & rigidity. Unpredictable/variable effect on: Postural instability, tremor, gait freezing, NMS.

Levodopa Formulations (Pitakpatapee, CMU/Siriraj)

Product	Formulation	Strength	Bioavail.	Tmax	T½	Notes
Sinemet	Immediate release (IR)	10/100, 25/100, 25/250 mg (carbidopa/levodopa)	80–98%	0.5–2h	1–3h	Standard; take on empty stomach
Madopar / Vopar	IR tablet	12.5/50, 25/100, 50/200 mg (benserazide/levodopa)	98%	0.5–1h	1–3h	Thai brand: Vopar 250mg
Madopar Dispersible	Dispersible/ODT	25/100 mg	98%	<1h	1–3h	For morning akinesia, delayed ON; dissolve in water
Madopar HBS	Extended-release (CR)	25/100 mg	50–70%	2–4h	6–8h	Nocturnal wearing-off; 20–30% dose increase needed vs IR
Stalevo	Triple combination	25/100/200, 37.5/150/200 mg (carbidopa/levodopa/entacapone)	—	—	—	For wearing-off; see COMT inhibitor section
Duopa/LCIG	Intraduodenal infusion	Variable	~continuous	Continuous	—	Advanced PD; requires PEG-J; ~70,000 THB/month

Levodopa clinical tips (Pitakpatapee):

Start at lowest effective dose; titrate slowly
Abrupt withdrawal risks: depression, anxiety, pain, and Neuroleptic Malignant Syndrome-like reaction — always taper gradually, never stop cold-turkey
When adding entacapone, reduce levodopa dose by ~25% if >800mg/day or prior dyskinesia
Minimum carbidopa dose for adequate DDCI effect: ~70–75 mg/day (peripheral DDC saturation)

3.3.2 Dopamine Agonists (DA)

Dopamine Agonists — Dosing & Receptor Profiles

Drug	Receptor	Starting dose	Target dose range	Titration
Pramipexole (non-ergot)	D3>D2	0.375 mg/day (IR: TID or ER: OD)	0.375–4.5 mg/day	+0.75 mg/week
Ropinirole (non-ergot)	D3>D2	2 mg/day	2–24 mg/day	+2 mg/week
Rotigotine (non-ergot, transdermal)	D3>D2>D1	2 mg/24h patch	2–16 mg/24h	+2 mg/week every 1–2 weeks
Piribedil (non-ergot)	D3>D2; α2 antagonist	50 mg/day	150–250 mg/day	+50 mg every 3 days
Bromocriptine (ergot)	D1(-), D2(+)	1.25 mg OD	7.5–40 mg/day	+1.25 mg/week → BID/TID
Apomorphine (SC injection)	D1=D2	1 mg SC test	2–6 mg/injection	Rescue doses; continuous infusion

Clinical Benefits of DA Agonists (Anthonini et al., Lancet Neurol 2009)

Delay need for levodopa (when used as monotherapy in early PD)
Fewer peak-dose dyskinesias vs levodopa (long T½ → more stable DA receptor stimulation)
Helpful as adjunct for motor fluctuations
Positive effects on NMS: sleep (D3 effects), pain, mood
Fewer tablets needed (once or twice daily for ER formulations)

DA agonists have HIGHER risk than levodopa for: Peripheral edema, somnolence, sudden onset of sleep, impulse control disorders (ICD), hallucinations, nausea, dopamine dysregulation syndrome, fibrosis (ergot-derived)

Levodopa has HIGHER risk than DA agonists for: Peak-dose dyskinesia, motor fluctuations, dopamine dysregulation syndrome

Impulse Control Disorder (ICD) with DA agonists: Pathological gambling, compulsive shopping, hypersexuality, binge eating — seen in ~14% of DA agonist-treated PD patients. Higher risk with younger patients, male sex, prior history of alcohol/drug use, depression. Management: dose reduction/withdrawal of DA agonist (warn patient of withdrawal symptoms). NOT unique to ergot agents — seen with all DA agonists.

Ergot DA agonists (bromocriptine): Risk of retroperitoneal, pleuropulmonary, pericardial fibrosis + valvular heart disease (echocardiographic monitoring recommended). Now largely avoided in PD — only used for other indications (hyperprolactinemia).

Sudden onset of sleep ("sleep attacks") with DA agonists: Rare but potentially dangerous; patients may fall asleep without warning while driving. Counsel all patients about this risk. Discontinue DA agonist if occurs; avoid driving.

3.3.3 MAO-B Inhibitors

MAO-B Inhibitors — Pharmacology & Dosing

Drug	Mechanism	Dose	Metabolism	Key AEs
Selegiline	Irreversible MAO-B inhibitor	5 mg QAM or 5 mg QAM + noon (avoid insomnia); max 10 mg/day	CYP2B6/2C19 → desmethyl-selegiline → l-amphetamine; take before 14:00 to avoid insomnia	Insomnia (amphetamine metabolite), confusion, dizziness, exacerbation of levodopa dyskinesias
Rasagiline (Azilect)	Irreversible MAO-B inhibitor	Monotherapy: 1 mg OD; Adjunct: 0.5→1 mg OD	CYP1A2 → aminoindan (non-amphetamine metabolite)	Headache, arthralgia, dyspepsia, constipation, depression, flu-like; levodopa dyskinesia exacerbation
Safinamide	Reversible MAO-B inhibitor + glutamate modulation	50→100 mg/day (add-on to levodopa)	Multiple pathways	Insomnia, nausea, dyskinesia, fall risk; retinal safety monitoring

Clinical uses of MAO-B inhibitors:

Monotherapy in early PD (efficacious — MDS EBM 2018)
Adjunct to levodopa (reduces off-time ~0.5–1 hour/day)
May slow disease progression (debated — ADAGIO trial rasagiline 1 mg showed possible neuroprotection but not confirmed)

Selegiline vs Rasagiline — key difference: Selegiline metabolizes to l-amphetamine → stimulant side effects (insomnia, confusion, especially in elderly). Rasagiline metabolizes to aminoindan (no amphetamine activity) → generally better tolerated. Both are irreversible MAO-B inhibitors. Do not use >10 mg/day selegiline (loses MAO-B selectivity → cheese reaction with tyramine-containing foods).

Drug interactions: MAO-B inhibitors + SSRIs → serotonin syndrome (rare at therapeutic doses); + meperidine (pethidine) → hyperpyrexia, rigidity, agitation (selegiline more concerning due to residual MAO-A activity at higher doses).

3.3.4 COMT Inhibitors

Entacapone (Comtan) — Pharmacology

Mechanism: Selective, reversible inhibitor of peripheral catechol-O-methyltransferase (COMT). Acts in gut; does NOT cross BBB. Inhibits peripheral conversion of levodopa to 3-O-methyldopa (3-OMD) → increases levodopa bioavailability and half-life → more stable plasma levels → reduces wearing-off.

Dosing: 200 mg with EACH dose of levodopa/DDCI (IR or CR); maximum 8–10 times daily; can be taken with or without food.

Key adverse effects:

Dyskinesia (most common — reduce levodopa 25% if >800 mg/day or prior dyskinesia)
Diarrhea (5–10%)
Harmless orange/brown urine discoloration
Worsening of levodopa side effects (N/V, OH, hallucinations) due to increased levodopa exposure

Tolcapone vs Entacapone: Tolcapone is a central+peripheral COMT inhibitor — MORE effective than entacapone but requires liver function monitoring (3 fatal cases of hepatotoxicity). Entacapone is peripheral only — no hepatotoxicity but less potent. Opicapone (50 mg OD) is newer, once-daily peripheral COMT inhibitor with favorable efficacy profile.

3.3.5 Anticholinergics

Anticholinergic Agents

Drug	Dose	Indication	Key warnings
Trihexyphenidyl (Benzhexol, Artane)	0.5–1 mg BID → 2 mg TID (max 6–10 mg/day)	Young patients (<70y) with prominent tremor; drug-induced parkinsonism	Avoid in elderly, dementia, BPH, closed-angle glaucoma
Benztropine (Cogentin)	0.5–2 mg BID	Acute dystonic reaction (IM/IV), drug-induced parkinsonism	Same contraindications; IV for acute reactions

Adverse effects: Hallucinations, cognitive impairment (may precipitate dementia), sedation, dry mouth, blurred vision, urinary retention, constipation, tachycardia.

CRITICAL: Abrupt discontinuation causes ACUTE exacerbation of Parkinsonism — always taper slowly. Never abruptly stop in hospitalized PD patients (surgical patients, NPO orders).

3.3.6 Amantadine

Amantadine

Mechanisms: (1) Promotes presynaptic dopamine release; (2) Non-selective NMDA receptor antagonist (glutamate antagonism → anti-dyskinesia effect)

Doses: 100 mg OD → 100 mg BID; max 200–300 mg/day (renal dose adjustment — clearance is 100% renal)

Uses:

Early mild PD (monotherapy or adjunct)
Levodopa-induced dyskinesia (LID) — only oral drug with level A evidence for LID (NMDA antagonism)
Drug-induced parkinsonism (short-term)

Adverse effects: Livedo reticularis (mottled skin, common, benign), ankle edema, insomnia, confusion/hallucinations (especially elderly), nausea.

3.3.7 Evidence-Based Medicine (MDS EBM, Fox et al. 2018)

MDS EBM for Symptomatic PD Treatment (Fox et al., Mov Disord 2018)

Intervention	Evidence Level	Clinical Utility
Levodopa (monotherapy)	Efficacious (A)	Clinically useful +++
DA agonists (monotherapy)	Efficacious (A)	Clinically useful
MAO-B inhibitors (monotherapy)	Efficacious (A)	Clinically useful (less than levodopa)
Istradefylline (adenosine A2A antagonist)	Nonefficacious for monotherapy	Not recommended as monotherapy; useful as adjunct for OFF
Prevent disease progression	None proven	No currently established neuroprotective therapy

3.3.8 Thai PD Treatment Algorithm

Thai Parkinson's Treatment Algorithm

Patient group	First-line recommendation	Rationale
Age <60, mild symptoms	Non-ergot DA agonist OR MAO-B inhibitor	Delay levodopa; fewer motor complications long-term
Age ≥60, functional impairment	Levodopa first	Better efficacy; cognitive tolerance of DA agonists lower in elderly
Significant symptoms, any age	Levodopa regardless of age	Functional need takes priority
Motor complications develop	Add COMT inhibitor (entacapone) or MAO-B inhibitor; consider DBS if eligible	Address wearing-off

Available medications in Thailand (as of 2024):

Levodopa: Vopar 250 mg (levodopa/benserazide), Madopar HBS, Madopar Dispersible
DA agonists: Ropinirole (Requip), Pramipexole, Rotigotine patch, Piribedil, Bromocriptine, Apomorphine
MAO-B: Rasagiline (Azilect), Selegiline
COMT: Entacapone (Comtan), Stalevo
Anticholinergics: Trihexyphenidyl (Benzhexol/Artane), Benztropine
Amantadine

References: Fox SH et al. International Parkinson and movement disorder society evidence-based medicine review: Update on treatments for the motor symptoms of Parkinson's disease. Mov Disord 2018;33:1248–1266. Anthonini A et al. Dopamine agonists and agonist/levodopa combination therapy in PD. Lancet Neurol 2009;8:929–37. Youdim MBH, Bakhle YS. Monoamine oxidase: isoforms and inhibitors in PD. Nat Rev Neurosci 2006;7:295–309.

Q: A 55-year-old patient with PD on levodopa 300 mg/day develops wearing-off, with symptoms returning 2–3 hours after each dose. What are the strategies to address wearing-off?

Wearing-off management options:

Increase levodopa dose frequency (smaller, more frequent doses — TID → QID)
Add COMT inhibitor (entacapone 200 mg with each levodopa) — extends levodopa half-life, reduces OFF time by ~1–1.5 hours/day
Add MAO-B inhibitor (rasagiline 0.5–1 mg OD) — reduces off-time ~45 min/day
Add DA agonist (pramipexole, ropinirole) — smoother DA stimulation; reduces OFF time
Switch to Stalevo (carbidopa/levodopa/entacapone triple combination)
Controlled-release (HBS) formulation at bedtime for nocturnal/early morning akinesia
Dispersible levodopa for rescue (faster Tmax <1h)
Advanced therapies if uncontrolled: LCIG (duodenal infusion), apomorphine SC, DBS

Drug interactions note: levodopa competes with dietary protein for absorption — protein redistribution diet (low protein meals during day, high protein at night) can improve daytime motor fluctuations.

Q: A 70-year-old man with PD develops vivid visual hallucinations (sees small animals). He is on levodopa 750 mg/day, pramipexole 3 mg/day, and trihexyphenidyl 6 mg/day. How do you approach this?

PD psychosis/hallucinations management — stepwise drug withdrawal:

Step 1: Eliminate precipitants — infection, dehydration, metabolic disturbance
Step 2: Reduce/eliminate anticholinergics first (trihexyphenidyl — most likely offender) — taper over weeks
Step 3: Reduce/eliminate DA agonist (pramipexole — more pro-psychotic than levodopa)
Step 4: Reduce MAO-B inhibitor if present
Step 5: Reduce amantadine if present
Step 6: Reduce levodopa (last resort — preserves motor benefit)
Step 7: Add antipsychotic if psychosis persists:
- Quetiapine (off-label; low D2 affinity; does not worsen motor symptoms) — most used in Thailand
- Clozapine (gold standard; requires weekly CBC for agranulocytosis) — most evidence
- Pimavanserin (5-HT2A inverse agonist; FDA-approved PD psychosis 2016; not available in Thailand)
- AVOID: Haloperidol, chlorpromazine, risperidone, olanzapine — worsen PD significantly
Step 8: Rivastigmine if dementia component (PDD)

3.4 Motor Complications & Advanced Therapies

3.4.1 Motor Complications of Levodopa

Motor complications develop in ~50% of patients after 5 years of levodopa and nearly all patients by 10 years. They are caused by pulsatile dopaminergic stimulation from short-acting levodopa in the context of progressive presynaptic neuron loss.

Classification of Motor Complications

Type	Subtype	Timing	Description	Management
Motor Fluctuations	Wearing-off	Predictable, before next dose	Return of PD symptoms before next dose; most common	Add COMT, MAO-B, DA agonist; increase frequency; CR formulation
	Delayed ON	After dose	Levodopa takes longer to work (>60 min); often from food competition	Take on empty stomach; dispersible formulation; prokinetics (domperidone)
	No ON (dose failure)	After dose	Dose does not work at all; gastroparesis or GI absorption problem	Domperidone; apomorphine rescue; check GI motility
	ON/OFF fluctuations	Unpredictable	Sudden, random transitions; cannot be predicted from dose timing	Advanced therapies (DBS, LCIG, apomorphine); continuous DA stimulation
	Freezing of gait (FOG)	Variable	Sudden inability to initiate/continue gait; "start hesitation," narrow spaces	Optimize levodopa; cueing (auditory, visual, rhythmic); physical therapy; STN-DBS
Dyskinesias	Peak-dose dyskinesia	During maximum drug effect (ON)	Choreiform/dystonic involuntary movements; most common type (70%)	Reduce individual levodopa dose (increase frequency); amantadine; consider surgery
	Diphasic dyskinesia	Rising and falling plasma levels	Ballistic/dystonic movements at beginning and end of dose; difficult to manage	Continuous DA stimulation (apomorphine, LCIG); DBS
	Off-period dystonia	During OFF state	Painful foot/leg dystonia; typically early morning; toe curling	Long-acting CR formulation at bedtime; bedtime DA agonist; botulinum toxin

3.4.2 Referral Criteria to Movement Disorder Specialist

When to refer to specialist (Thai guidelines): Dyskinesia; wearing-off symptoms; morning akinesia; delayed ON; sudden freezing or unpredictable OFF; diphasic dyskinesia; levodopa >800 mg/day still inadequate control; uncontrolled side effects (hallucinations, ICD, sleep disturbance). Early referral improves outcomes.

3.4.3 Deep Brain Stimulation (DBS)

DBS Eligibility Criteria

Indications:

Confirmed PD diagnosis (UKPDS/MDS criteria)
Demonstrated dopamine responsiveness (levodopa test: ≥30–40% UPDRS-III improvement)
Motor fluctuations and/or dyskinesia refractory to optimal medical therapy
Functionally limiting tremor refractory to medical therapy

Relative exclusions:

Dementia (MCI acceptable; Hoehn-Yahr ≤4 in ON state)
Active untreated mood disorder or psychosis
Unrealistic patient expectations
Significant structural brain pathology, uncontrolled hypertension
Significant surgical risk (anticoagulation, cardiopulmonary)

DBS targets:

STN (subthalamic nucleus): Best overall effect; allows levodopa dose reduction (~50%); addresses tremor, rigidity, bradykinesia, dyskinesia; EARLYSTIM trial (Deuschl 2006, NEJM): DBS superior to best medical therapy for quality of life even in early motor complications
GPi (globus pallidus interna): Better for dyskinesia-dominant; no levodopa reduction needed; better for patients with psychiatric comorbidities
VIM (ventral intermediate nucleus of thalamus): Tremor only; does not address other PD features; used primarily for ET

DBS cost (Thailand, 2024): ~854,530 THB (3–5 year battery life) + replacement battery ~605,420 THB

What DBS does NOT help well: Axial symptoms (gait freezing, postural instability, dysarthria, dysphagia) — especially if present in OFF state; cognitive decline; NMS; apraxia of eyelid opening. These features may worsen after STN-DBS. GPi-DBS preserves speech better than STN-DBS.

3.4.4 Advanced Non-oral Therapies

Advanced PD Therapy Comparison

Therapy	Route	Mechanism	Indication	Cost (Thailand)	Key issues
Apomorphine SC	Subcutaneous injection/infusion	DA agonist D1=D2	Rescue for sudden OFF; continuous SC infusion for fluctuations	~40,500 THB/month	Nausea (pretreat with domperidone); skin nodules; neuropsychiatric SE; not oral
LCIG (Duodopa)	Intraduodenal infusion	Levodopa/carbidopa gel	Advanced PD with severe motor fluctuations; on ≥4 doses/day with ≥3 hours OFF/day	~70,000 THB/month	Requires PEG-J tube; weight loss; PN, polyneuropathy; site complications; 24-hr nurse for initiation
DBS (STN/GPi)	Surgical implant	High-frequency electrical stimulation	Motor fluctuations/dyskinesia; tremor-dominant PD	~854,530 THB initial	Surgical risks (ICH, infection, lead displacement); programming complexity; battery replacement
MRgFUS (Focused ultrasound)	Transcranial	Thermal ablation of VIM/STN/GPi	Unilateral tremor-dominant; not candidate for DBS	High; not widely available	Unilateral only; irreversible; gait/balance risks

References: Deuschl G et al. A randomized trial of deep-brain stimulation for Parkinson's disease. NEJM 2006;355:896–908. Williams A et al. Deep brain stimulation plus best medical therapy versus best medical therapy alone for advanced Parkinson's disease (PD SURG trial). Lancet Neurol 2010;9:581–591. Schuepbach WMM et al. Neurostimulation for Parkinson's disease with early motor complications (EARLYSTIM). NEJM 2013;368:610–622.

Q: A 61-year-old male with PD on levodopa 100 mg TID for 4 years develops involuntary dancing movements of his arms that occur 45–60 minutes after taking levodopa and last about 90 minutes. He is otherwise well during these movements. What type of complication is this, and what is first-line management?

Peak-dose dyskinesia — choreiform involuntary movements occurring at maximum levodopa plasma level (peak ON state). Pathophysiology: pulsatile dopamine receptor stimulation + striatal sensitization from progressive presynaptic loss. Management options: (1) Reduce each individual levodopa dose and increase frequency (e.g., 100mg TID → 75mg QID — same total dose, smoother levels); (2) Add amantadine 100 mg BID — only oral drug with Level A evidence for dyskinesia (NMDA antagonism); (3) Extended-release preparation can smooth peaks; (4) If severe/uncontrolled: refer for DBS (GPi target particularly good for dyskinesia) or LCIG infusion.

3.5 Atypical Parkinsonism (Parkinson-Plus Syndromes)

Atypical Parkinsonism — Differential Diagnosis Summary

Feature	PD	PSP	MSA-P	CBS	DLB
Pathology	α-synuclein (Lewy bodies)	Tau (4R)	α-synuclein (glial)	Tau (4R)	α-synuclein + Aβ
Tremor	Rest tremor (70%)	Rare/action only	Jerky irregular	Action/myoclonic	Variable
Falls (early)	Late (>5 years)	Yes (<3 years)	Yes (falls early)	Moderate	Moderate
Eye movements	Normal early	V-SNGP (downward)	Slow saccades (later)	Supranuclear	Normal or slow
Autonomic	Moderate, later	Mild	Severe early (OH, urinary)	Mild	Moderate
Cognitive/dementia	Late (PDD)	Frontal executive (early)	Cognitive mild	Asymmetric cortical	Early prominent
Asymmetry	Marked	Symmetric	Symmetric	Highly asymmetric	Variable
Levodopa response	Excellent (70–100%)	Minimal	Minimal–moderate, transient	None/minimal	Variable
MRI clue	Normal (early)	Hummingbird/morning glory	Hot cross bun; putaminal slit	Asymmetric cortical atrophy	Normal or hippocampal
Key clinical sign	Asymmetric PD	Applause sign; retrocollis	Antecollis; inspiratory stridor	Alien limb; cortical myoclonus; apraxia	Fluctuating cognition; VH

3.5.1 Progressive Supranuclear Palsy (PSP)

MDS PSP Criteria 2017 (Höglinger et al., Mov Disord 2017)

Pathology: 4-repeat tauopathy; neuronal loss + tau neurofibrillary tangles in STN, SN, pallidum, brainstem

Core functional domains:

O: Oculomotor dysfunction (vertical supranuclear gaze palsy → downward VGP pathognomonic; slow vertical saccades)
P: Postural instability (falls, retropulsion)
A: Akinesia (bradykinesia, freezing, micrographia)
C: Cognitive dysfunction (frontal executive, apathy)

Clinical variants:

PSP-RS (Richardson Syndrome): Classic; early falls/retropulsion + vertical gaze palsy; "hummingbird sign" on MRI; "morning glory sign" (midbrain atrophy)
PSP-P (PSP-Parkinsonism): Resembles PD initially; slower progression; some levodopa response early
PSP-CBS: Asymmetric, limb apraxia, cortical features
PSP-F: Frontal predominant; early cognitive/behavioral changes

Clinical pearls:

"Applause sign": asked to clap 3 times, patients continue (>5 claps = frontal disinhibition)
Retrocollis (head extension backward) — contrast with PD (antecollis) and MSA (antecollis)
"Surprised facies" — wide-eyed expression from levator overactivity
"Square wave jerks" on eye movement examination

3.5.2 Multiple System Atrophy (MSA)

MDS MSA Criteria 2022 (Wenning et al., Lancet Neurol 2022)

Definition: Sporadic, progressive, adult-onset (>30 years) neurodegenerative disorder with glial cytoplasmic inclusions (GCIs) of α-synuclein

Mandatory criterion: Acquired autonomic dysfunction + motor features (parkinsonism or cerebellar)

Autonomic criteria:

Neurogenic orthostatic hypotension (OH): ≥20 mmHg systolic / ≥10 mmHg diastolic within 3 minutes of standing
Urinary incontinence/retention (neurogenic bladder dysfunction)
Erectile dysfunction in males

Subtypes:

MSA-P (Parkinsonian variant, Striatonigral Degeneration): Predominant parkinsonism; poor levodopa response; putaminal changes on MRI (putaminal slit sign — T2 hypointensity lateral putamen)
MSA-C (Cerebellar variant, OPCA): Predominant cerebellar ataxia; "hot cross bun sign" on MRI (T2 hyperintensity pons)

Additional features: Inspiratory stridor (laryngeal dystonia — emergency if acute); antecollis (exaggerated forward head tilt); cold blue-purple hands/feet (Raynaud-like); Pisa syndrome

Prognosis: Median survival 9–10 years; death from aspiration pneumonia, respiratory failure (stridor)

3.5.3 Corticobasal Syndrome (CBS) / Corticobasal Degeneration (CBD)

Pathology: 4-repeat tauopathy (like PSP); astrocytic plaques in cortex and BG. Note: CBS is a clinical syndrome; CBD is the neuropathological diagnosis (requires autopsy). CBS can result from CBD, PSP, Alzheimer disease, and others.

Clinical features: Asymmetric akinetic-rigid syndrome + cortical features:

Limb apraxia: Cannot perform skilled movements despite intact strength/sensation
Alien limb phenomenon: Limb moves involuntarily, as if acting on its own will
Cortical sensory loss: Astereognosis, agraphesthesia
Cortical myoclonus: Stimulus-sensitive; jerky tremor
Aphasia (left-sided cortical involvement)

MRI: Asymmetric cortical atrophy (parietal dominant), contralateral to more affected side

3.5.4 Dementia with Lewy Bodies (DLB)

DLB Consensus Criteria 2017 (McKeith et al., Neurology 2017)

Essential feature: Dementia (cognitive decline interfering with function)

Core clinical features (2 sufficient for probable DLB; 1 for possible):

Fluctuating cognition — variable attention/alertness (ask family: "does he zone out or seem confused for minutes to hours?")
Recurrent visual hallucinations — well-formed, detailed (people, animals); present in ~80%
RBD — acting out dreams; often precedes dementia by years
Parkinsonism — one or more of bradykinesia, rest tremor, rigidity

Indicative biomarkers:

Reduced DAT uptake on DAT-SPECT/PET (same as PD)
Reduced cardiac MIBG uptake (postganglionic sympathetic denervation)
Polysomnographic confirmation of REM sleep without atonia

DLB vs PDD: "1-year rule" — dementia appearing >1 year after motor symptoms = PDD; Dementia appearing before or within 1 year of parkinsonism = DLB. Pathologically similar; clinically distinction helps management.

Critical management warning: DLB patients are exquisitely sensitive to neuroleptics (even atypical) — neuroleptic sensitivity reaction: acute severe Parkinsonism, autonomic instability, impaired consciousness, potentially fatal. Use only quetiapine or clozapine if antipsychotic absolutely needed. AVOID: haloperidol, olanzapine, risperidone

References: Höglinger GU et al. Clinical diagnosis of progressive supranuclear palsy. Mov Disord 2017;32:853–864. Wenning GK et al. The Movement Disorder Society criteria for the diagnosis of multiple system atrophy. Lancet Neurol 2022;21:430–442. McKeith IG et al. Diagnosis and management of dementia with Lewy bodies. Neurology 2017;89:88–100.

Q: A 66-year-old woman has 2-year history of progressively worsening balance, falling backward, and inability to look down. She has mild bradykinesia but no resting tremor. Levodopa 600 mg/day provides only ~20% improvement. What is the diagnosis, and what is the characteristic MRI finding?

Progressive Supranuclear Palsy — Richardson Syndrome (PSP-RS). Key features: vertical supranuclear gaze palsy (downward) + early falls + retrocollis + axial > appendicular rigidity + poor levodopa response. MRI finding: "Hummingbird sign" (also "penguin sign") — atrophy of the midbrain on midsagittal MRI with relative preservation of pons, creating a silhouette resembling a hummingbird. Also: "morning glory sign" — midbrain atrophy seen on axial view. Midbrain AP diameter <17mm and MRPI (MR Parkinsonism Index = pons area/midbrain area × SCP width/MCP width) >13.55 supports PSP. Treatment: No disease-modifying therapy. Symptomatic: levodopa trial (if any benefit); donepezil for cognition; amantadine for some; fall prevention; PEG for dysphagia; botulinum for blepharospasm/eyelid apraxia.

3.6 Essential Tremor

Essential Tremor — Key Facts

Definition (MDS criteria 2018): Bilateral postural and/or kinetic tremor of the hands and forearms; duration ≥3 years; possibly additional tremor at other locations (head, voice, chin). No other neurological signs (isolated ET).

Epidemiology: Most common movement disorder; prevalence ~5% (age >65: 15–20%); autosomal dominant tendency (~50% familial); LINGO1 and ETM2 gene loci.

Feature	Essential Tremor	Parkinsonian Tremor
Type	Kinetic >> postural; no rest tremor	Rest >> re-emergent postural; no kinetic
Frequency	4–12 Hz	4–6 Hz
Onset at rest	No	Yes (classic)
Body distribution	Bilateral hands + head + voice	Unilateral onset; hands, chin, legs; head rare
Response to alcohol	Yes (~50–70%)	No (or minimal)
Family history	Common (~50%)	Less common (10–15%)
DAT-SPECT	Normal	Abnormal (reduced uptake)
Other PD features	Absent (rigidity, bradykinesia, postural instability)	Present

ET Treatment (AAN Practice Guideline 2011, Zesiewicz et al.)

Agent	Evidence	Dose	Notes
Propranolol	Level A (established)	60–320 mg/day in divided doses; ER 60–80 mg/day	Non-selective β-blocker; CI: asthma, bradycardia, DM insulin-dependent; reduces handwriting tremor ~50%
Primidone	Level A (established)	25 mg QHS → 250 mg TID; start very low (acute side effects at initiation)	Metabolized to phenobarbital; sedation, dizziness at start; hepatic induction; effective for distal > proximal
Topiramate	Level B (probably effective)	25–400 mg/day	Word-finding difficulty, renal stones, weight loss; useful if propranolol/primidone fail
Gabapentin	Level B	1200–3600 mg/day TID	Useful for head tremor; sedation; useful if CNS not tolerated
Alprazolam	Level B	0.125–3 mg/day	Benzodiazepine; dependence risk; short-term use
Atenolol, sotalol, nadolol	Level C (possibly effective)	Atenolol 50–150 mg/day	Less CNS penetration than propranolol; option if pulmonary concerns
Clonazepam	Level C	0.5–6 mg/day	Especially for orthostatic tremor; sedation; dependence
BoNT-A injection	Level B (hand tremor); Level A (head tremor)	50–100U per hand (wrist flexors/extensors)	Useful for disabling hand/head tremor; weakness is main SE

ET Surgical Options

Thalamic DBS (VIM): Level A (established efficacy); bilateral DBS for bilateral tremor; side effects: dysarthria, paresthesia, disequilibrium; battery-dependent
Thalamotomy (radiofrequency): Unilateral VIM; no hardware; irreversible; speech/balance risks
MR-guided Focused Ultrasound (MRgFUS) thalamotomy: FDA-approved 2016; non-invasive; unilateral only; safe; no craniotomy; irreversible
Gamma Knife radiosurgery: Delayed onset (months); unilateral

Head tremor in ET: Unlike PD where head tremor is very rare (almost never), ET commonly involves head (15–37%) — "no-no" (horizontal rotation) or "yes-yes" (vertical). Cervical dystonia also causes head tremor but with abnormal posture + geste antagoniste. Differentiation: ET head tremor = head moves but neck posture normal; Dystonic head tremor = head deviates + sensory trick helps + irregular frequency. BoNT-A for head tremor: Level A evidence.

Enhanced Physiological Tremor (EPT): 8–12 Hz, bilateral; exacerbated by anxiety, caffeine, thyroid disease, medications (β-agonists, valproate, lithium, SSRIs, steroids, cyclosporine, theophylline). Treat underlying cause; propranolol for symptomatic relief.

Q: A 72-year-old retired engineer presents with 10-year history of bilateral hand tremor affecting his daily activities, specifically his handwriting and tea-drinking. His son also has tremor. Examination shows bilateral postural/kinetic hand tremor; no rest tremor, no rigidity or bradykinesia. He tried propranolol 80 mg/day with 40% improvement but has side effects. What are the next steps?

Essential Tremor (familial). Positive family history, bilateral kinetic > postural, no PD features, propranolol partial response. Management options:

Add primidone (start 25 mg QHS — avoid high initial doses → acute toxicity) — combination propranolol + primidone more effective than either alone
Alternatively: If propranolol SE limiting, switch to atenolol 50–150 mg (less CNS penetration, less bradycardia symptoms)
If still refractory: Add topiramate 25–400 mg (Level B); gabapentin 1200–3600 mg
If disabling and refractory to medications: Refer for DBS (VIM thalamus — bilateral) or MRgFUS (unilateral, right thalamus for dominant right hand) — excellent tremor reduction (>80%)
BoNT injection wrist flexors/extensors: useful for writer's tremor; 50–100 U per hand; caveat: wrist weakness

Head/voice tremor if present: BoNT-A for head (Level A); propranolol for voice tremor.

3.7 Dystonia & Cervical Dystonia

3.7.1 Dystonia Overview

Pathophysiology: Loss of cortical/subcortical inhibition (GABA, dopamine, acetylcholine); dysfunction of BG-brainstem-cerebellar-cortical network; abnormal sensorimotor integration → loss of surround inhibition → overflow.

Dystonia Classification by Etiology (Albanese 2013)

Category	Subtypes	Examples	Management
Isolated (Idiopathic)	Focal, segmental, multifocal, generalized, hemidystonia	Cervical dystonia, writer's cramp, blepharospasm	BoNT, oral medications, DBS
Genetic	DYT-TOR1A (DYT1), DYT-THAP1 (DYT6), DYT-GCH1 (DYT5), DYT-ATP1A3, etc.	TOR1A: early-onset generalized; GCH1: dopa-responsive	Specific treatments per gene
Acquired	Drug-induced, structural, vascular, infectious, metabolic	Tardive dystonia (antipsychotics), Wilson's disease, kernicterus	Remove offending agent; treat cause
Dopa-Responsive Dystonia	GCH1 mutation (AD) or TH gene (AR)	Segawa syndrome; childhood dystonia + diurnal fluctuation; dramatic levodopa response	Levodopa (small doses lifelong)

Dopa-Responsive Dystonia (DRD) — "Segawa Disease": GCH1 mutation → reduced tetrahydrobiopterin (BH4) → reduced tyrosine hydroxylase activity → dopamine deficiency. Features: childhood-onset foot dystonia (worse in afternoon — diurnal fluctuation), gait abnormality, hyperreflexia in lower limbs, often misdiagnosed as cerebral palsy. Treatment: levodopa 1–2 mg/kg/day (minimal dose) = complete and sustained response for decades. ALL patients with childhood-onset dystonia should receive levodopa trial.

3.7.2 Isolated Cervical Dystonia (iCD)

Cervical Dystonia — Epidemiology & Diagnosis (Phokaewvarangkul, 2024; Albanese, Mov Disord 2023)

Definition (old term: Spasmodic torticollis): Most common adult-onset focal dystonia; involuntary sustained/intermittent contractions of neck muscles causing abnormal head postures and/or movements.

Epidemiology: Incidence 1.18/100,000 person-years; Prevalence ≥30/million; Peak onset: 5th–6th decade; F:M = 1.5:1

Two pathognomonic features:

Sensory trick (geste antagoniste): Touching adjacent area of head/face/neck reduces dystonia — seen in ~90% of CD patients; unique to dystonia
Pain: Cervical pain in 67–75%; NRS average 4.8/10; significantly impacts QoL

CD Subtype Classification (Col-Cap Concept)

Movement type	Column subtype	Cap subtype	Description
Lateral bend	Laterocollis	Laterocaput	Ear toward shoulder (column = neck tilt; cap = head tilt)
Horizontal rotation	Torticollis	Torticaput	Chin toward shoulder
Anterior tilt	Antecollis	Antecaput	Chin to chest; common in MSA
Posterior tilt	Retrocollis	Retrocaput	Head extension; common in PSP
Lateral shift	Lateral shift (Col)	Sagittal shift (Cap)	Head shifted laterally/forward-backward without rotation

Col = movement of cervical column (C2-C7 level); Cap = movement of atlanto-axial/occipital joints (head only)

TWSTRS (Toronto Western Spasmodic Torticollis Rating Scale)

Domain	Max score	What it measures
Severity subscale	35	Head posture (maximal deviation, duration, effect of sensory trick), shoulder elevation, ROM, duration factor
Disability subscale	20	Activities of daily living impact (work, reading, driving, social)
Pain subscale	20	Pain severity (0–10 NRS), duration, disability from pain
Total TWSTRS	75	Higher score = more severe

3.7.3 Botulinum Toxin (BoNT) Treatment for Cervical Dystonia

BoNT Preparations — Comparison

Product	Serotype	Brand	Molecular weight	Target protein	Active neurotoxin
OnabotulinumtoxinA	A	Botox®	900 kDa complex	SNAP-25	0.90 ng/100U
AbobotulinumtoxinA	A	Dysport®	500–900 kDa	SNAP-25	2.69 ng/500U (highest active neurotoxin per approved dose)
IncobotulinumtoxinA	A	Xeomin®	150 kDa (naked, no complexing proteins)	SNAP-25	0.40 ng/100U (lowest antibody potential)
RimabotulinumtoxinB	B	Myobloc®	700 kDa	Synaptobrevin (VAMP)	—

Field et al., Toxins 2018: Dysport 500U contains 2.69 ng of active 150kDa neurotoxin vs Botox 100U = 0.90 ng — greater amounts of active neurotoxin per FDA-approved dose may explain longer duration of action reported with Dysport.

BoNT Clinical Evidence for CD

First-line treatment for cervical dystonia (Level A evidence)

Dysport (AboBoNTA) 500U RCT: Significant TWSTRS-Total reduction vs placebo at week 4; maintained to week 12; 72.6–81.5% patients did NOT require retreatment before week 16 (Esquenai A et al. Front Neurol 2020)
Dysport QoL Study (Mordin M et al. BMJ Open 2014): Significantly greater improvements in all SF-36 Physical Functioning, Role Physical, Bodily Pain, Role Emotional vs placebo (p≤0.03)
INTEREST IN CD2 long-term study (Colosimo C et al. JNS 2020): 466 patients over 3 years; TWSTRS continuously decreased; mean −7.4 ± 11.9 reduction from baseline to 36 months; patient satisfaction at peak effect: 84.1–91.2%; AEs: dysphagia 6.8%, muscle weakness 3.7%
Dysport vs Botox crossover RCT (Ranoux D et al. JNNP 2002; 54 patients): Dysport 1:3 and 1:4 more efficient than Botox on Tsui score and TWSTRS pain (p=0.01–0.04); dysphagia in 3% (Botox), 15.6% (Dysport 1:3), 17.3% (Dysport 1:4)

Thai FDA BoNT-A Guidelines for CD

Thai FDA indications (as per Appendix 3, Phokaewvarangkul):

Cervical dystonia (iCD) — allowed cervical area only; NOT face, mouth, or trunk
Hemifacial spasm (idiopathic)
Spasmodic dysphonia

Eligibility for BoNT-A treatment:

Must have failed conservative treatment >3 months
Frequency at least every 3 months (to reduce antibody formation risk)
Severity criteria for insurance coverage:
- Mild (<20 units per session): ≥20% abnormal posture, impaired ADL
- Moderate (20–50 units): 20–50% abnormal posture, impaired ADL, TWSTRS >5
- Severe (>50 units): >50% abnormal posture, unable to stop, TWSTRS >5

Starting doses:

Botox: 50–150 units per session
Dysport: 250–500 units per session

Dose titration principle: Lower dose first session; increase by 30% if inadequate at follow-up; reduce by 30% if adverse effects. Key muscles: SCM, Splenius capitis, Semispinalis capitis, Trapezius, Levator scapulae (based on clinical pattern).

Muscle selection for CD by subtype:

Torticollis (chin toward right): Right sternocleidomastoid (contralateral rotation) + Left splenius capitis (ipsilateral rotation)
Laterocollis (right ear toward right shoulder): Right splenius capitis + Right SCM + Right levator scapulae
Retrocollis: Bilateral splenius capitis + semispinalis capitis
Antecollis: Bilateral SCM (for head flexion) — warning: this is the most dangerous injection (dysphagia, respiratory risk); start very low dose
Shoulder elevation: Ipsilateral trapezius

Use ultrasound or EMG guidance for deep muscles. Wait at least 3 months between sessions (antibody prevention).

BoNT Injection Technique — "2MIN" Checklist

M — Muscles to avoid at eye area: levator palpebrae superioris and frontalis muscles (risk of ptosis)
M — Makeup must be removed before injection
I — Injection types: intradermal, intramuscular, subcutaneous (choose per target)
I — Identifying target side (clinical exam, EMG/ultrasound guidance)
N — Needle: 29 or 30 gauge only (fine gauge minimizes spread)
N — No rubbing at treated area (prevents toxin spread)

For blepharospasm/hemifacial spasm injection: 40 units per eye (Botox); 10U per injection point × 4 points (preseptal/orbital orbicularis oculi); upper lid: direct needle away from center (avoid levator palpebrae); bevel side up; max 120U per eye.

Oral Medications for Dystonia

Drug	Dose	Use	Evidence
Trihexyphenidyl	High dose: up to 60 mg/day (tolerated in children); 6–12 mg in adults	Generalized dystonia; especially DYT1	Level C; better in children
Levodopa	Start low: 1 mg/kg/day	DRD (DYT5) — dramatic response; ALL childhood dystonia warrant trial	Level A for DRD
Clonazepam	0.5–6 mg/day	Adjunct for anxious patients; myoclonic dystonia	Level C
Baclofen (oral/intrathecal)	10–80 mg/day; intrathecal pump for severe generalized	Generalized dystonia, especially spastic dystonia	Level C; intrathecal for selected
Tetrabenazine	25–75 mg/day	Secondary dystonia; tardive dystonia	Reduces involuntary movements; depression risk

DBS for dystonia: GPi target; best evidence for DYT1 generalized dystonia (Level A); focal dystonia refractory to BoNT; onset may take weeks-months (unlike PD); improvement continues up to 2 years.

References: Albanese A et al. EFNS/MDS-ES recommendations for the diagnosis of primary dystonias. Eur J Neurol 2011;18:5–18. Phokaewvarangkul O. Optimizing Cervical Dystonia Management. CMU lecture 2024. Field M et al. AbobotulinumtoxinA, OnabotulinumtoxinA, and IncobotulinumtoxinA neurotoxin content. Toxins 2018;10:535. Colosimo C et al. Cumulative effects of long-term abobotulinumtoxinA in cervical dystonia. JNS 2020;416:117015.

3.8 Chorea & Huntington's Disease

3.8.1 Chorea — Differential Diagnosis

Causes of Chorea (HARD-Chorea Mnemonic)

Category	Diagnosis	Key features
Hereditary	Huntington's disease (HD)	Autosomal dominant; CAG repeat expansion HTT gene; psychiatric + chorea + dementia
Hereditary	Wilson's disease	Young-onset; KF rings; liver disease; copper
Hereditary	Neuroacanthocytosis, DRPLA, SCA17, BenignHC	Rare; genetic testing
Autoimmune	Sydenham's chorea	Post-streptococcal; children; "milkmaid grip"; GABHS
Autoimmune	SLE, antiphospholipid syndrome	Young women; ANA, anti-dsDNA, antiphospholipid Ab
Autoimmune	Anti-NMDAR encephalitis	Orofacial dyskinesia + psychiatric + autonomic
Rx (Drug)	Levodopa-induced dyskinesia	Parkinson's disease; peak-dose choreiform
Rx (Drug)	OCP, anticonvulsants, cocaine, amphetamine	Drug history; hormonal chorea in women on OCP
Rx (Drug)	Antipsychotics (tardive dyskinesia)	Orobuccolingual chorea; dorsiflexion of toes; years of antipsychotic use
Disorders (metabolic)	Hyperglycemia (nonketotic)	Hemiballism/hemichorea; T1 hyperintense putamen; resolves with glucose control
Disorders (vascular)	Stroke (STN, caudate, putamen)	Acute onset; vascular risk factors
Chorea gravidarum	Pregnancy	Prior Sydenham's or antiphospholipid; resolves post-delivery
Infections	Encephalitis, HIV, CJD, toxoplasmosis (BG)	Acute/subacute; fever, CSF changes

3.8.2 Huntington's Disease

Huntington's Disease — Key Facts

Genetics: Autosomal dominant; CAG repeat expansion in HTT gene (chromosome 4p16.3); normally <27 repeats; HD if ≥36 repeats; >40 = full penetrance; 36–39 = reduced penetrance; juvenile HD (<20y onset) has >60 repeats (usually paternal transmission due to anticipation)

Pathology: Selective loss of medium spiny neurons in caudate nucleus and putamen → striatal atrophy; "caudate atrophy" + enlarged frontal horns (boxcar ventricles) on MRI

Clinical triad:

Motor: Chorea (early) → hypokinesia and rigidity (late); dysphagia, dysarthria; oculomotor (saccade initiation delay, broken smooth pursuit)
Cognitive: Subcortical dementia (executive dysfunction, processing speed, memory); unlike Alzheimer's — relatively preserved language and naming early
Psychiatric: Depression (40%), irritability, apathy, OCD, psychosis; psychiatric symptoms often precede motor symptoms

Diagnosis: Clinical features + positive genetic testing (CAG ≥36). Predictive testing requires genetic counseling (pre-test and post-test). MRI: caudate atrophy, dilated frontal horns (bicaudate index elevated). PET/SPECT: decreased striatal metabolism.

HD Management

Symptom	Treatment	Notes
Chorea	Tetrabenazine 25–75 mg/day; Deutetrabenazine (preferred — fewer SE); Valbenazine	VMAT2 inhibitors; depression risk; sedation; parkinsonism
Chorea (alternative)	Haloperidol, aripiprazole, quetiapine	Antipsychotics reduce chorea via D2 blockade; use atypical first
Chorea (alternative)	Amantadine 200–400 mg/day	Modest benefit; NMDA antagonism
Depression	SSRIs (sertraline, fluoxetine) preferred	Mirtazapine if insomnia comorbid
Psychosis/irritability	Quetiapine, aripiprazole	Avoid haloperidol for long-term (worsens rigidity later)
Cognitive	No proven treatment; memantine or rivastigmine modest	Supportive care; occupational therapy
Dysphagia	Speech therapy; modified diet; PEG late-stage	Major cause of aspiration pneumonia

No disease-modifying therapy approved (as of 2025). Investigational: antisense oligonucleotides (ASO) targeting HTT mRNA — Phase III trials ongoing.

Prognosis: Mean survival 15–20 years from onset; death typically from aspiration pneumonia, cardiovascular disease, suicide.

Tardive Dyskinesia (TD): Involuntary orobuccolingual-masticatory choreiform movements after chronic exposure to dopamine receptor blockers (DRBAs: antipsychotics, metoclopramide, prochlorperazine). Features: oro-buccal-lingual (smacking, chewing, tongue protrusion) + trunk rocking + finger piano-playing + dorsiflexion of toes. Appears after months-years of DRBA. Persists or worsens even after stopping. Treatment: (1) Reduce/stop offending drug; (2) Switch to clozapine/quetiapine (less D2 blockade); (3) VMAT2 inhibitors: valbenazine (40–80 mg/day; FDA-approved 2017) or deutetrabenazine (12–48 mg/day; FDA-approved 2017) — most effective treatments.

References: Ross CA et al. Huntington disease: natural history, biomarkers and prospects for therapeutics. Nat Rev Neurosci 2014;15:375–387. Bhidayasiri R et al. Evidence-based guideline: Treatment of tardive syndromes. Neurology 2013;81:463–469.

3.9 Wilson's Disease

Wilson's Disease — Key Facts (EASL Guidelines 2012)

Genetics: Autosomal recessive; ATP7B gene (chromosome 13q14.3) mutation → defective hepatic copper-transporting ATPase → copper accumulates in liver, brain, cornea, kidneys

Incidence: 1/30,000; gene frequency 1/90; consider in all patients <55 years with unexplained liver disease, neurological/psychiatric symptoms, or movement disorder

Clinical Manifestations

System	Features
Hepatic	Acute hepatitis → fulminant hepatic failure (Coombs-negative hemolytic anemia); chronic hepatitis → cirrhosis; liver disease often precedes neurological symptoms
Neurological	Tremor (wing-beating/Holmes tremor most classic), dysarthria, dysphagia, ataxia, dystonia, chorea, rigidity, bradykinesia (Parkinsonism), gait abnormality
Psychiatric	Personality change (50%), depression, psychosis, mania, cognitive decline; often presenting complaint in young adults
Ocular	Kayser-Fleischer (KF) rings — golden-brown ring at corneal periphery (Descemet's membrane); slit-lamp required; present in >95% of neurological Wilson's but only 50–60% of hepatic
Other	Renal tubular acidosis (Fanconi syndrome), premature osteoporosis, cardiomyopathy, sunflower cataracts

Wilson's Disease Diagnosis (Leipzig Score, EASL 2012)

Feature	Score
KF rings present	+2
Neuropsychiatric symptoms typical of WD	+2
Serum ceruloplasmin <0.1 g/L	+2 (0.1–0.2 g/L = +1)
Coombs-negative hemolytic anemia (with high serum copper)	+1
24-hour urine copper >2 μmol/day (in absence of acute hepatitis)	+2
Liver copper >250 μg/g dry weight	+2
Mutation analysis: two disease-causing mutations	+4 (one mutation = +1)

Score ≥4 = likely WD; Score 3 = possible WD; Score ≤2 = WD unlikely

Essential investigations in suspected WD:

Serum ceruloplasmin (low <20 mg/dL in 95% of neurological WD; false negatives with inflammation/estrogen)
24-hour urine copper (>100 μg/day in symptomatic WD; >40 μg/day = abnormal)
Slit-lamp examination for KF rings
LFTs, CBC (hemolytic anemia)
Brain MRI: "face of the giant panda" sign (midbrain T2); T2 hyperintensity putamen, caudate, thalamus, brainstem
ATP7B genetic testing (confirm diagnosis; screen siblings)

Wilson's Disease Treatment

Drug	Class	Dose	Indication	Key issues
Penicillamine	Copper chelator	250 mg QID (+ pyridoxine 25 mg/day); titrate up	First choice in hepatic WD; established for decades	Neurological worsening on initiation (25%); SLE-like, nephrotic syndrome, penicillin allergy cross-reactivity; pyridoxine deficiency
Trientine	Copper chelator (different mechanism)	250 mg TID–QID before meals	Preferred when neurological WD (less neurological worsening); penicillamine intolerance	Iron deficiency; less SE than penicillamine; drug of choice in neurological WD
Zinc acetate	Blocks intestinal copper absorption	50 mg TID (elemental zinc)	Maintenance after chelation; presymptomatic (siblings); pregnancy	Gastric irritation; less effective for hepatic decompensation; monitor LFTs
Liver transplantation	Curative for hepatic	—	Acute liver failure; decompensated cirrhosis; neurological WD (controversial)	Corrects hepatic metabolic defect; KF rings and neurological symptoms may improve

Wilson's disease in movement disorders: The single most important treatable cause of young-onset movement disorder. Wing-beating tremor (Holmes/rubral tremor = rest + postural + kinetic) is the CLASSIC movement disorder of Wilson's, but can also present as dysarthria, dystonia, chorea, or parkinsonism. Brain MRI: "face of giant panda" (midbrain) = pathognomonic. ALWAYS check in patients <50 with unexplained neurological + hepatic disease. Treatment reverses or stabilizes neurological symptoms in most patients.

3.10 Movement Disorder Emergencies

3.10.1 Neuroleptic Malignant Syndrome (NMS)

NMS — Diagnosis & Management

Definition: Life-threatening idiosyncratic reaction to dopamine receptor blockers (DRBAs) or rapid withdrawal of dopaminergic agents; characterized by hyperthermia + muscle rigidity + autonomic instability + altered consciousness.

Levenson Diagnostic Criteria (1985):

3 Major criteria: Hyperthermia (>38°C), muscle rigidity, elevated CK (>2× ULN)
9 Minor criteria: Tachycardia, BP fluctuation, tachypnea, altered consciousness, diaphoresis, leukocytosis, elevated LDH, abnormal LFTs, incontinence
Diagnosis: 3 major OR 2 major + 4 minor (after excluding other causes)

Pathophysiology: Central DA blockade (especially in striatum and hypothalamus) → impaired thermoregulation + muscle rigidity. Peripheral: direct muscle toxicity from continued contraction → rhabdomyolysis.

Treatment — Woodbury staging:

Stage	Severity	Treatment
I	Mild (rigidity, temp <38°C, CK ↑)	Discontinue offending drug; IV fluids; cooling; benzos for agitation
II	Moderate (temp 38–40°C, hemodynamics stable)	Stage I + Bromocriptine 2.5–10 mg TID or Amantadine 100 mg BID–TID (DA agonism)
III	Severe (temp >40°C, CK >1000, renal failure)	Stage II + Dantrolene 1–2.5 mg/kg IV q6h (max 10 mg/kg/day) — direct muscle relaxant (blocks RyR)
IV	Life-threatening (rhabdomyolysis, respiratory failure)	ICU; Dantrolene + Bromocriptine; dialysis if renal failure; intubation
V	Refractory	Electroconvulsive therapy (ECT) as last resort

Mortality: 5–30% (historical); now ~5–10% with early recognition/treatment; death from respiratory failure, cardiovascular collapse, acute renal failure.

Wait 2 weeks before restarting antipsychotic after NMS resolution; switch to lower-potency agent; monitor closely.

NMS vs Serotonin Syndrome:

Feature	NMS	Serotonin Syndrome
Cause	DA receptor blockers; DA withdrawal	Serotonergic agents (SSRIs, SNRIs, MAOIs, triptans, fentanyl, dextromethorphan)
Onset	Days to weeks (insidious)	Hours (rapid — within 24 hrs)
Rigidity	Lead-pipe rigidity (extrapyramidal)	Clonus >> rigidity; hyperreflexia
Pupils	Normal	Mydriasis
Tremor	Rare	Yes (coarse, action)
Treatment	Dantrolene + bromocriptine	Cyproheptadine (5-HT2 antagonist) 4–8 mg; benzodiazepines; cooling

3.10.2 Acute Dystonic Reaction

Cause: Acute exposure to dopamine receptor blockers (antipsychotics, metoclopramide, prochlorperazine). Occurs within hours to 5 days of starting or increasing dose.

Clinical features: Oculogyric crisis (eyes roll up/sideways), torticollis, trismus, laryngospasm (emergency!), opisthotonus, dystonic gait.

Treatment:

First-line: Benztropine (Cogentin) 1–2 mg IV/IM OR Diphenhydramine (Benadryl) 25–50 mg IV/IM — rapid reversal within minutes
Follow-up: Oral anticholinergic (benztropine 1–2 mg BID or trihexyphenidyl) for 4–7 days (to prevent recurrence)
Laryngospasm: Airway management; benztropine IV
If offending drug cannot be stopped: prophylactic low-dose anticholinergic

3.10.3 Status Dystonicus

Definition: Escalating, severe dystonic contractions causing rhabdomyolysis, hyperthermia, renal failure, respiratory failure; life-threatening emergency requiring ICU care.

Causes: Sudden withdrawal of baclofen/benzodiazepines; infection triggering dystonic storm; medication adjustment in dystonia patient; underlying metabolic/neurodegenerative disease.

Management:

ICU admission; airway management
IV benzodiazepines (high dose)
IV anticholinergics (trihexyphenidyl)
IV dantrolene (for hyperthermia/rigidity)
Propofol infusion (sedation)
Continuous intrathecal baclofen if pump available
Emergency DBS activation if patient has implant
Treat precipitating cause

3.10.4 Acute Chorea/Hemiballism Emergencies

Hyperglycemic hemichorea-hemiballism: Non-ketotic hyperosmolar state → hemichorea/hemiballism contralateral to T1-hyperintense (striatal) lesion on MRI. Treatment: glucose normalization; dopamine receptor blocker (haloperidol 0.5–2 mg BID) if severe; almost always resolves with metabolic correction.

Sydenham's chorea: Post-GAS streptococcal autoimmune; milkmaid grip; "Jack-in-the-box" tongue; often with carditis (rheumatic fever). Treatment: valproate first-line; penicillin prophylaxis (secondary prevention for RF); IVIG/steroids for severe cases.

References: Strawn JR et al. Neuroleptic malignant syndrome. Am J Psychiatry 2007;164:870–876. Woodbury MM. NMS staging. 1984. Frucht SJ. Treatment of movement disorder emergencies. Neurotherapeutics 2014;11:208–12. Bhidayasiri R, Truong DD. Chorea and related disorders. Postgrad Med J 2004;80:527–34.

Q: A 28-year-old man with schizophrenia received haloperidol 5 mg IM 2 days ago. He now presents with neck twisted to the right, difficulty swallowing, and eyes forced upward. Temperature is 37.2°C, BP 130/80, HR 90. What is the diagnosis and immediate treatment?

Acute Dystonic Reaction (ADR) to haloperidol — specifically: torticollis + oculogyric crisis. Immediate treatment: Benztropine 1–2 mg IV (or diphenhydramine 25–50 mg IV if benztropine unavailable) — reversal usually within 5–15 minutes. If no IV access: IM is equally effective. Follow-up: Oral benztropine 1–2 mg BID × 4–7 days (prevents recurrence as antipsychotic effect continues). If antipsychotic is needed long-term: switch to atypical (quetiapine, aripiprazole — less D2 blockade); consider prophylactic anticholinergic. Distinguished from NMS: No fever, no rigidity, no CK elevation, no autonomic instability → ADR not NMS. NMS is more insidious, systemic, and life-threatening.

Q: A 45-year-old man with PD is admitted for urgent surgery and becomes NPO. His usual medications (levodopa 300 mg TID + pramipexole 1 mg TID) are held. On day 2, he develops fever 39.5°C, generalized rigidity, confusion, and CK 5000 U/L. What is the diagnosis and treatment?

NMS-like syndrome from acute dopaminergic withdrawal (Parkinsonism-Hyperpyrexia Syndrome — PHS). Clinically identical to NMS but caused by abrupt discontinuation of dopaminergic drugs rather than DA receptor blockade. Treatment: (1) Restart dopaminergic therapy IMMEDIATELY — via NG tube, dispersible levodopa, or parenteral route if available; (2) Dantrolene 1–2.5 mg/kg IV q6h for rigidity/hyperthermia; (3) Bromocriptine 2.5–10 mg q8h via NG; (4) ICU monitoring; cooling; IV fluids (rhabdomyolysis prevention — target urine output 200–300 mL/hr); (5) Avoid typical antipsychotics. Prevention: Never make PD patients NPO without alternative dopaminergic route. Use dispersible levodopa via NG tube perioperatively. Alternative: rotigotine transdermal patch (continuous DA stimulation, no GI needed).

4. Headache Disorders

Headache disorders are the most common neurological complaints worldwide, with migraine ranking as the leading cause of disability in adults aged 15–49. This section covers the full ICHD-3 classification, pathophysiology (trigeminovascular pathway, CGRP), acute and preventive treatment algorithms, special populations, TACs, trigeminal neuralgia, and red flag evaluation at headache-specialist depth.

4.1 Pathophysiology & Classification of Headache ▶

KEY PATHOPHYSIOLOGIC MECHANISMS

1. Cortical Spreading Depression (CSD): A self-propagating wave of neuronal and glial depolarization spreading at ~3–5 mm/min across cortex. The neurophysiologic substrate of migraine aura. CSD activates meningeal nociceptors via release of K⁺, H⁺, glutamate, and arachidonic acid metabolites, triggering trigeminovascular activation.

2. Trigeminovascular Pathway: Central to migraine pain generation. Trigeminal nerve (CN V1) innervates dural vessels → releases CGRP, substance P, PACAP → vasodilation + neurogenic inflammation → signals travel via trigeminal ganglion → Trigeminal Nucleus Caudalis (TNC, C1–C2) → thalamus → somatosensory cortex. Convergence with cervical afferents at TNC explains cervical pain and cutaneous allodynia.

3. CGRP (Calcitonin Gene-Related Peptide): The key neuropeptide in migraine. Released from trigeminal terminals during attacks → vasodilation + pain sensitization. CGRP levels elevated during attacks, normalize with triptan treatment. Target of all modern acute (gepants) and preventive (CGRP mAbs) therapies.

4. Central Sensitization: Repeated activation → sensitization of TNC neurons → cutaneous allodynia (late-attack marker). Sensitization of thalamic neurons → allodynia distant from head. Central sensitization indicates poor triptan response (treat early). Chronic sensitization → chronification of migraine.

5. Hypothalamic Involvement: "Migraine generator." Premonitory symptoms (yawning, fatigue, food craving) precede attacks by 24–48h, originating from hypothalamic activation. Also explains circadian patterns in cluster headache (suprachiasmatic nucleus).

6. Descending Modulation: Periaqueductal gray (PAG) and rostral ventromedial medulla (RVM) modulate pain descending to TNC. PAG dysfunction → loss of inhibitory control → headache facilitation. PAG iron deposition seen in chronic migraine MRI.

ICHD-3 Headache Classification Framework

Category	Major Types	Key Distinguishing Feature
Part 1: Primary Headache	Migraine, TTH, TACs, Other primary	No underlying structural cause
Part 2: Secondary Headache	Head/neck trauma, Vascular, Non-vascular intracranial, Substance, Infection, Homeostasis, Cranial structure, Psychiatric	Causally related to another condition
Part 3: Painful Cranial Neuropathies	Trigeminal neuralgia, Other cranial neuralgias	Nerve-territory pain distribution

🧠 Specialist Pearl – Migraine Subtypes Spectrum: Migraine without aura (MwoA) is most common (70–75%). Migraine with aura (MwA) 25–30%; aura is fully reversible cortical/brainstem symptom. Chronic migraine (CM) ≥15 days/month ≥3 months with ≥8 migraine features. Status migrainosus: attack >72h. Medication overuse headache (MOH) complicates ≥50% of CM cases. Key: migraine disability is vastly underestimated — MIDAS scoring essential.

Migraine Epidemiology

Global prevalence ~15% (women 18–19%, men 6–7%). Peak reproductive years women age 25–55. F:M ratio 3:1 (hormonal influence). Point prevalence higher than diabetes + asthma + epilepsy combined. Leading cause of disability in 15–49 year age group (GBD 2019). Annual direct/indirect costs enormous (lost productivity, ED visits, medications). Thai data: prevalence ~12.6%.

ICHD-3 Classification Hierarchy: 1-digit code = group (e.g., 1 = Migraine), 2-digit = type (1.1 = MwoA), 3-digit = subtype (1.2.1 = Typical aura with headache), 4-digit = sub-subtype (1.2.1.1 = Migraine with typical aura). All codes must match minimum diagnostic criteria.

4.2 Migraine Without Aura (MwoA) — ICHD-3 1.1 ▶

ICHD-3 DIAGNOSTIC CRITERIA — MwoA (1.1) [MEMORIZE]

A. At least 5 attacks fulfilling criteria B–D

B. Headache lasting 4–72 hours (untreated or unsuccessfully treated)

C. Headache has ≥2 of 4 characteristics (mnemonic: MUPA):

Moderate–severe intensity (limits/prohibits daily activity)
Unilateral location
Pulsating quality
Aggravated by routine physical activity (walking, climbing stairs)

D. During headache, ≥1 of:

Nausea and/or vomiting
Photophobia AND phonophobia

E. Not better accounted for by another ICHD-3 diagnosis

Note: Bilateral location in ~40%; non-pulsating in ~50% — diagnosis still met if other criteria fulfilled

Clinical Features of MwoA

Feature	Classic Presentation	Frequency (%)
Location	Unilateral (frontotemporal)	~60%
Quality	Pulsating/throbbing	~75%
Severity	Moderate–severe	~90%
Nausea	Present	~80%
Vomiting	Present	~50%
Photophobia	Present	~90%
Phonophobia	Present	~85%
Osmophobia	Present (not in criteria)	~40%
Cutaneous allodynia	Scalp/face/arm tenderness	~60%
Postdrome	Fatigue, cognitive fog	~80%

Four Phases of Migraine Attack

Phase	Timing	Features	Neurobiological Basis
Premonitory	24–48h before	Yawning, fatigue, food craving (esp. sweet), mood change, neck stiffness, increased urination	Hypothalamic activation; dopaminergic activation
Aura	20–60 min before (if present)	Visual, sensory, speech symptoms — fully reversible, march over ≥5 min	Cortical spreading depression
Headache	4–72h	MUPA + nausea/photo/phono; worsens with movement	Trigeminovascular activation; CGRP release
Postdrome	Up to 48h after	Fatigue, cognitive slowing, mood change (low/high), scalp tenderness	Cortical hypoactivity; ongoing sensitization

🧠 ID Migraine Screen (Validated 3-Question Tool): (1) Has headache limited activity for ≥1 day in past 3 months? (2) Nausea/vomiting with headache? (3) Sensitivity to light? — Sensitivity 81%, Specificity 75% for diagnosing migraine in primary care. ≥2/3 positive = migraine likely. MIDAS score quantifies disability (Grade I–IV).

MIDAS (Migraine Disability Assessment) Score

Grade	Score	Disability Level	Clinical Action
I	0–5	Little/none	Acute-only treatment
II	6–10	Mild	Acute ± consider prevention
III	11–20	Moderate	Acute + preventive treatment
IV	≥21	Severe	Acute + aggressive prevention + multidisciplinary

HALT-90 Index: headache days in past 90 days — ≥10 days/90d = frequent episodic migraine; ≥15 = chronic migraine. Tracks frequency simply.

Q: A 32-year-old woman presents with 10-year history of headaches, unilateral throbbing, severity 8/10, with nausea and photophobia, lasting ~18 hours, occurring 5–6 times/year. What is the diagnosis and what first-line acute treatment is most appropriate?

Diagnosis: Migraine Without Aura (ICHD-3 1.1) — fulfills all criteria: ≥5 attacks, 4–72h duration, unilateral + pulsating + severe (≥2/4 MUPA) + nausea/photophobia (criterion D).
Severity stratification: Moderate–severe → Stratified care → Triptan as first-line acute specific therapy.
Choice: Sumatriptan 50–100 mg oral (most studied) or Eletriptan 40 mg (faster onset, higher efficacy). May combine with naproxen 500 mg for better sustained pain-free rate (POZEN study).
Frequency: 5–6 attacks/year → MIDAS Grade I–II; preventive not indicated. Headache diary + lifestyle triggers recommended.

4.3 Migraine With Aura & Subtypes (Hemiplegic, Brainstem, Retinal, Vestibular) ▶

ICHD-3 DIAGNOSTIC CRITERIA — Migraine With Aura (1.2) [MEMORIZE]

A. At least 2 attacks fulfilling B–C

B. ≥1 of the following fully reversible aura symptoms:

Visual (most common: scintillating scotoma, fortification spectra)
Sensory (numbness, tingling — typically unilateral, hand-face)
Speech/language (dysphasia)
Motor (weakness) — only in Hemiplegic Migraine
Brainstem (dysarthria, vertigo, tinnitus, diplopia, ataxia, decreased consciousness)
Retinal (monocular visual symptoms)

C. ≥3 of 6 aura characteristics:

≥1 aura spreads gradually over ≥5 minutes
≥2 auras occur in succession
Each aura lasts 5–60 minutes
≥1 aura is unilateral
≥1 aura is positive (scintillating, tingling) — note visual negative OK too
Aura accompanied or followed within 60 minutes by headache

D. Not better accounted for by another ICHD-3 diagnosis; TIA excluded

Types of Aura — Visual Aura Details

Scintillating scotoma: Classic — expanding arc of shimmering zigzag lights (fortification spectrum) surrounding a blind spot, starting central, spreading peripherally over 20–30 min. Corresponds to CSD propagation across visual cortex (V1). Pathognomonic of migraine aura when typical.

Simple visual aura: Flashing lights, spots, or lines without fortification. Positive phenomena from CSD activation phase; negative phenomena (scotoma) from CSD suppression phase.

Typical aura duration: 5–60 minutes (key: if >60 min → suspect hemiplegic, stroke, or prolonged aura). Aura-to-headache interval up to 60 minutes allowed.

Migraine Subtypes — Key Differentiators

Subtype	ICHD-3 Code	Defining Feature	Key Considerations
Typical aura with headache	1.2.1.1	Visual/sensory/speech aura only; migraine headache follows	Most common aura subtype
Typical aura without headache	1.2.1.2	Same aura, no headache	Older patients; DD: TIA (aura spreads gradually, TIA symptoms appear abruptly)
Hemiplegic migraine	1.2.3	Motor weakness (fully reversible) as part of aura	May mimic stroke — CT/MRI mandatory first episode; never use triptans/ergots acutely
Familial hemiplegic (FHM)	1.2.3.1	Hemiplegic + 1st/2nd degree relative same	FHM1 (CACNA1A), FHM2 (ATP1A2), FHM3 (SCN1A) — ion channel mutations
Sporadic hemiplegic (SHM)	1.2.3.2	Hemiplegic, no family history	Same as FHM1 in severity; consider genetic testing
Migraine with brainstem aura	1.2.2	≥2 brainstem symptoms (dysarthria, vertigo, tinnitus, diplopia, ataxia, altered consciousness, bilateral paresthesia)	Previously "basilar-type migraine"; motor weakness absent; if motor → hemiplegic
Retinal migraine	1.2.4	Monocular visual symptoms (blindness or positive phenomena) in one eye only	Must examine eye during attack; ophthalmology referral; may cause permanent monocular vision loss; triptans relatively contraindicated

🧠 Aura vs. TIA — Critical Distinction:

Aura: Positive symptoms → negative symptoms; gradual spread (march) over ≥5 min; typically homonymous (hemianopia) not monocular; young woman; prior identical episodes
TIA: Sudden onset; negative symptoms predominate (weakness, numbness, aphasia); monocular visual loss (amaurosis fugax = ICA territory); older age + vascular risk factors; MRI DWI may show acute lesion
Key test: MRI brain DWI/ADC — acute ischemic changes = TIA/stroke; normal = favors aura
Migraine with aura ↑ stroke risk 2× (especially in women who smoke + use OCP — avoid OCP in MwA + smoking)

Vestibular Migraine — ICHD-3 A1.6.5 (Appendix)

VESTIBULAR MIGRAINE DIAGNOSTIC CRITERIA

A. At least 5 episodes fulfilling B–D

B. Current or past history of migraine without or with aura

C. Vestibular symptoms of moderate–severe intensity lasting 5 min–72h

Spontaneous vertigo (internal or external)
Positional vertigo (triggered by head movement)
Visually induced vertigo
Head motion-induced vertigo
Head motion-induced nausea

D. ≥50% of episodes associated with ≥1 migraine feature:

Headache with ≥2 migraine characteristics (MUPA)
Photophobia and phonophobia
Visual aura

E. Not better accounted for by another vestibular or ICHD-3 diagnosis

Vestibular Migraine — DDx Table

Condition	Vertigo Duration	Hearing Loss	Key Feature
Vestibular Migraine	5 min–72h (variable)	No (usually)	Migraine Hx; headache/phobia with vertigo in ≥50%
BPPV	Seconds (<1 min)	No	Dix-Hallpike positive; positional
Ménière's Disease	20 min–12h	Yes (low-freq, fluctuating)	Tinnitus + aural fullness; audiogram
Vestibular Neuritis	Days (single prolonged episode)	No	Single attack; +HIT; no recurrence
Brainstem/Cerebellar TIA	Minutes	No	Vascular risk factors; HINTS exam → MRI DWI
Labyrinthitis	Days	Yes	Auditory + vestibular; often post-viral

Vestibular Migraine Treatment

Phase	Drug	Dose	Evidence
Acute	Sumatriptan	50–100 mg oral / 6 mg SC	Case series; no RCT
	Metoclopramide	10 mg oral/IV	Symptom relief
	Prochlorperazine	12.5 mg IM	Vestibular sx relief
Preventive	Propranolol	40–240 mg/day	Observational
	Amitriptyline	10–75 mg nightly	Observational
	Venlafaxine	37.5–150 mg/day	RCT (small)
	Topiramate	25–100 mg/day	Open-label

Q: A 28-year-old woman with known migraine with aura presents with sudden onset of right-sided weakness and aphasia during a headache. She has had 3 prior attacks with right arm tingling followed by left-sided headache. How do you differentiate hemiplegic migraine from stroke, and what acute treatment is contraindicated?

Differentiation:

Prior identical episodes (3 previous) with same weakness + young age favor hemiplegic migraine (HM)
But: cannot exclude stroke clinically → Urgent MRI DWI/ADC mandatory
HM: No acute DWI lesion; may show cortical swelling, perfusion asymmetry; EEG may show slow waves
Family history of same attacks → Familial HM (CACNA1A/ATP1A2/SCN1A mutation)
HM attacks may last hours to days; full recovery expected (though may take longer)

Contraindicated in Hemiplegic Migraine:

Triptans — vasoconstriction concern; theoretically may extend ischemia in affected hemisphere
Ergotamine — same vasoconstrictive mechanism; absolutely avoid

Safe acute treatment for HM: NSAIDs (naproxen, ibuprofen), paracetamol, dopamine antagonists (metoclopramide), IV magnesium, IV valproate. If stroke cannot be excluded: treat as stroke emergency (tPA if criteria met within window).

🧠 Migraine With Aura & Stroke Risk: MwA confers 2× increased ischemic stroke risk vs. non-migraineurs. Risk multiplies:

MwA + OCP: RR 8–13×
MwA + smoking: RR 9–10×
MwA + OCP + smoking: RR ~34× (absolute risk still low but unacceptable)

Guideline: Avoid combined OCP in MwA + smoking. Progestin-only OCP or non-hormonal contraception preferred. Assess cardiovascular risk at each visit for MwA patients.

4.4 Chronic Migraine & Medication Overuse Headache (MOH) ▶

ICHD-3 DIAGNOSTIC CRITERIA — Chronic Migraine (1.3)

A. Headache (tension-type-like and/or migraine-like) on ≥15 days/month for >3 months, fulfilling criteria B and C

B. Occurring in a patient who has had at least 5 attacks fulfilling criteria for 1.1 (MwoA) and/or 1.2 (MwA)

C. On ≥8 days/month for >3 months, fulfilling any of:

Criteria C and D for Migraine without aura (1.1)
Criteria B and C for Migraine with aura (1.2)
Believed by the patient to be migraine at onset and relieved by triptan/ergot

D. Not better accounted for by another ICHD-3 diagnosis

Key concept: CM diagnosis can be made even when medication overuse is present — they are separate diagnoses that frequently coexist

Chronification Risk Factors (Migraine → Chronic Migraine)

Category	Risk Factors	Modifiable?
Behavioral	Medication overuse (strongest), sleep disorder (insomnia/OSA), caffeine overuse, physical inactivity, obesity (BMI >30 → 5× risk)	Yes
Psychiatric	Depression, anxiety, PTSD, somatization — all independent risk factors	Yes (treat comorbidities)
Social/Environmental	Life events, stressors, socioeconomic status, trauma history	Partially
Biological	High attack frequency (≥5 attacks/mo), female sex, allodynia (central sensitization marker), family history of CM	No
Medical	Head injury, snoring/OSA, hypothyroidism, asthma (↑ inflammation)	Yes

ICHD-3 — MEDICATION OVERUSE HEADACHE (MOH) Criteria (8.2)

A. Headache on ≥15 days/month

B. Regular overuse for >3 months of ≥1 drug taken as acute/symptomatic headache treatment:

Drug Class	Overuse Threshold	ICHD-3 Code
Ergotamine	≥10 days/month	8.2.1
Triptans	≥10 days/month	8.2.2
Non-opioid analgesics (NSAIDs, paracetamol)	≥15 days/month	8.2.3
Opioids	≥10 days/month	8.2.4
Combination analgesics	≥10 days/month	8.2.5
Multiple drug classes without individual overuse	≥10 days/month combined	8.2.6

C. Not better accounted for by another ICHD-3 diagnosis

MOH Pathophysiology

Chronic exposure to acute medications → downregulation of endogenous pain modulation (serotonergic descending inhibition reduced), upregulation of CGRP expression, cortical hypersensitivity. Analgesic-specific: opioids cause receptor desensitization and paradoxical hyperalgesia. Triptans: 5-HT1B/D desensitization → reduced efficacy + rebound. Reversal requires withdrawal; full recovery may take 2–3 months.

🧠 MOH Management Strategy — 4-Step Approach:

Diagnose and Educate: Explain MOH mechanism non-judgmentally; written information; headache diary. Many patients initially deny overuse — review diary together.
Withdraw the overused medication: Abrupt discontinuation preferred for most (triptans, NSAIDs, paracetamol). Gradual taper for opioids and barbiturates (seizure/withdrawal risk). Expect withdrawal headache for 2–10 days (reassure patient this is expected and will improve).
Bridging therapy during withdrawal: IV/IM dexamethasone 8 mg (reduces withdrawal symptoms per RCT); naproxen 500 mg bid if not the overused drug; amitriptyline 10 mg; prednisolone 60 mg × 5 days taper (evidence mixed).
Start preventive therapy: Topiramate (most RCT evidence in MOH), valproate, amitriptyline. CGRP mAbs: erenumab effective even without withdrawal first (PROMISE-1/2 subgroup analyses). BoNT-A PREEMPT protocol approved for CM ± MOH.

Resistant vs. Refractory Migraine — EHF Consensus Definitions

Term	Definition (EHF 2020)
Resistant Migraine	Failed ≥3 preventive drug classes (adequate dose, ≥3 months each) AND ≥4 migraine days/month with significant disability despite treatment. One of the failed drugs should be topiramate or valproate.
Refractory Migraine	Resistant migraine PLUS failed all CGRP mAbs (or gepants as preventives) AND BoNT-A. "End-stage" — requires tertiary headache center referral; neuromodulation devices, CGRP-nasal delivery, combination strategies.

Aspiration Goals for CM Treatment (IHS Guidelines):
Primary goal: ≥50% reduction in headache days/month
Secondary goals: ≥50% reduction in acute medication intake; ≥30% improvement in MIDAS/HIT-6 score; reduction in allodynia; improvement in sleep; return to work/social function

Q: A 45-year-old woman has headache on 22 days/month for 6 months. She uses ibuprofen 600 mg on 18 days/month. She has history of episodic migraine. Which diagnoses are present and what is the management priority?

Diagnoses (both present simultaneously):

Chronic Migraine (ICHD-3 1.3): ≥15 days/month >3 months with migraine history ✓
Medication Overuse Headache (ICHD-3 8.2.3): NSAIDs ≥15 days/month >3 months ✓ (threshold for non-opioid analgesics = 15 days)

Management priority:

First: NSAID withdrawal (abrupt OK for NSAIDs) + patient education
Bridging: Dexamethasone 8 mg IM/IV or prednisolone taper to manage withdrawal headache
Start prevention simultaneously: Topiramate 25 mg → 100 mg (Level A evidence in CM/MOH) or consider BoNT-A if frequent enough
Rescue acute: Limit to ≤10 days/month; switch class (if was using NSAID → use triptan as needed, limit <10d/mo)
Follow-up: 4–6 weeks; if no improvement after withdrawal → reassess MOH diagnosis

4.5 Acute Treatment of Migraine — Stratified Care & IV Rescue Protocols ▶

STRATIFIED CARE ALGORITHM — ACUTE MIGRAINE

Step-care across attacks (preferred): Assess severity + disability → select treatment tier accordingly:

Severity	MIDAS	First-Line Agent	Dose
Mild–Moderate (no disability)	Grade I	NSAIDs: Naproxen, Ibuprofen, Aspirin	Naproxen 500–1000 mg; Ibuprofen 400–600 mg; Aspirin 900–1000 mg + Metoclopramide 10 mg
Mild–Moderate	Grade I–II	Paracetamol (if NSAID contraindicated)	1000 mg oral; less effective than NSAIDs alone
Moderate–Severe (with disability)	Grade II–IV	Triptans (5-HT1B/1D agonists)	See triptan table below
Triptan-refractory or CI	Any	Gepants (CGRP antagonists)	Rimegepant 75 mg ODT (oral dissolving tablet)
Very severe/vomiting (ED)	Status	IV/IM rescue protocol	See IV rescue table below

Triptan Comparison Table

Drug	Dose	Route	Onset	2h Pain-Free Rate	Key Notes
Sumatriptan	50–100 mg	Oral	30–60 min	~29%	Most studied; also SC 6 mg (fastest, highest efficacy), nasal spray 20 mg
Sumatriptan SC	6 mg	SC injection	10–15 min	~55%	Fastest onset; best for rapid severe attacks; auto-injector available
Eletriptan	20–40 mg	Oral	30 min	~38%	Highest oral efficacy; more lipophilic; avoid if hepatic impairment (CYP3A4)
Rizatriptan	10 mg (5 mg with propranolol)	Oral (ODT available)	30 min	~37%	Reduce dose to 5 mg if on propranolol (MAO-A interaction)
Zolmitriptan	2.5–5 mg	Oral / nasal spray	30–45 min	~32%	Nasal spray 5 mg useful if vomiting
Almotriptan	12.5 mg	Oral	30–45 min	~32%	Favorable tolerability; less chest symptoms
Frovatriptan	2.5 mg	Oral	60–90 min	~26%	Longest T½ (~26h); useful for long attacks, menstrual migraine prophylaxis (mini-prophylaxis)
Naratriptan	2.5 mg	Oral	60–90 min	~24%	Slow onset; long T½; lower recurrence; fewer side effects; menstrual migraine

🧠 Triptan Prescribing Pearls:

Take early: Efficacy highest when taken at pain onset (mild phase), before central sensitization develops. Once allodynia present → triptan may not work.
Triptan + NSAID combination: Superior to either alone — Sumatriptan 85 mg + Naproxen 500 mg (Treximet) shows better sustained pain-free rates (POZEN studies)
Triptan failure ≠ class failure: Try 2–3 different triptans before concluding class failure (different receptor affinities, pharmacokinetics)
CI to triptans: Uncontrolled hypertension, ischemic heart disease, stroke/TIA, hemiplegic migraine, basilar migraine (relative), pregnancy (Category C), severe hepatic impairment, MAO-A inhibitors (sumatriptan/rizatriptan)
Chest tightness (triptan-associated): Common (up to 15%); not due to coronary vasospasm in most patients (myalgia, esophageal spasm). Rule out cardiac cause if risk factors present.

Gepants — CGRP Receptor Antagonists (Acute Use)

Drug	Dose	Indication	Evidence	Key Advantage
Rimegepant	75 mg ODT	Acute migraine ± prevention	SPARTAN, BHV3000-301: 2h pain-free 19% vs placebo 12%	No MOH potential; dual acute + preventive dosing option (QOD for prevention); safe in CVD
Ubrogepant	50–100 mg	Acute migraine	ACHIEVE I/II: 2h pain-free ~19% vs 12%	No vasoconstriction; safe with CV risk
Zavegepant	10 mg nasal spray	Acute migraine	Phase 3: Rapid onset (15 min)	First nasal gepant; fastest gepant onset

Gepant 2h pain-free rates (~19%) lower than triptans (~29–38%) but useful when triptans contraindicated or overused. No serotonin syndrome risk. No rebound headache risk.

IV Rescue Therapy — Emergency Department / Inpatient Protocol

Indication: Status migrainosus (>72h), severe migraine unresponsive to oral therapy, migraine with vomiting/dehydration, hyperemesis preventing oral medications, rebound after triptan failure.

Drug	Dose	Route	Evidence Level	Notes
Metoclopramide	10–20 mg IV over 15 min	IV	Level A	Anti-dopaminergic; antiemetic + analgesic; watch for akathisia (treat with diphenhydramine 25 mg IV)
Prochlorperazine	10 mg IV	IV	Level A	More sedating; akathisia risk; superior to metoclopramide in some trials
Chlorpromazine	0.1 mg/kg IV (max 25 mg)	IV slow	Level A	Orthostatic hypotension — prehydrate with 500 mL NS; QTc monitoring
Droperidol	2.5 mg IV	IV	Level A	QTc prolongation; highly effective; ECG monitoring required
Ketorolac	30 mg IV / 60 mg IM	IV or IM	Level A	NSAID; useful when dopamine antagonists CI or failed; avoid in renal impairment
Valproate sodium	500–1000 mg in 100 mL NS over 30 min	IV	Level B	Effective; avoid in women of childbearing age (teratogen); hepatotoxicity monitor
Magnesium sulfate	1–2 g in 100 mL NS over 15–30 min	IV	Level B	Most evidence in MwA; blocks NMDA receptors; safe in pregnancy (up to 48h use); flush sensation common
Dexamethasone	8–10 mg IV (single dose)	IV	Level B	Reduces headache recurrence at 24–72h; does NOT treat index headache acutely; use as add-on
Dihydroergotamine (DHE)	0.5–1 mg IV over 3 min; may repeat q8h × 3 doses	IV (with antiemetic pre-treatment)	Level A	Highly effective for status migrainosus; pre-treat with metoclopramide 10 mg; CI: recent triptan use (24h), cardiovascular disease, pregnancy
Sumatriptan SC	6 mg SC	SC	Level A	If no previous triptan; fastest-onset triptan
Lasmiditan	100–200 mg oral	Oral	Level A	5-HT1F agonist (dittan); no vasoconstriction; CNS dizziness/sedation; do not drive 8h after

🧠 IV Protocol for Status Migrainosus (Siriraj Protocol):

IV fluid hydration (NS 500–1000 mL)
Metoclopramide 10 mg IV slowly (antiemetic first)
Wait 15 min → if partial response: add Ketorolac 30 mg IV
If no response: Valproate 500 mg IV over 30 min OR Droperidol 2.5 mg IV
Dexamethasone 8 mg IV to prevent recurrence (add-on at any point)
If all fail: DHE IV protocol with antiemetic pre-treatment
Consider admission if >72h, dehydrated, or uncontrolled pain

Discharge: Limit opioids (MOH risk, not first-line per guidelines). If discharged with headache: naproxen 500 mg + methylprednisolone 32 mg to take at home.

Greater Occipital Nerve (GON) Block

Indication: Acute migraine rescue (ED or office), cluster headache prophylaxis, frequent migraine requiring rapid bridge to preventives, MOH withdrawal.

Technique: Patient prone or sitting. Landmark: 1/3 distance from occipital protuberance to mastoid tip (along superior nuchal line). Inject 2–3 mL of 0.5% bupivacaine + 20 mg methylprednisolone. Bilateral injection for bilateral headache. Effect within 15–30 min; may last 4–8 weeks.

Evidence: RCT evidence for acute migraine and cluster headache. Multiple small RCTs show superior to placebo for headache days. Duration of benefit varies (1–4 weeks).

Q: A 38-year-old woman with known migraine presents to the ED with severe throbbing headache 9/10, vomiting ×4, lasted 80 hours. She used sumatriptan 100 mg ×2 at home without relief. What is the diagnosis and what IV treatment do you initiate?

Diagnosis: Status Migrainosus (ICHD-3 1.4.1) — migraine attack lasting >72 hours (80h), with characteristic features and triptan failure (triptan-refractory at home). May also have component of dehydration (vomiting ×4).

IV Treatment Protocol:

Hydration: NS 500–1000 mL IV (dehydration from vomiting)
Antiemetic first: Metoclopramide 10 mg IV over 15 min → reduces both vomiting and headache (dopamine antagonist antiemetic + analgesic)
NSAID add-on: Ketorolac 30 mg IV (different mechanism; additive to dopamine antagonist)
Recurrence prevention: Dexamethasone 8 mg IV × 1 dose (reduces headache recurrence at 24–72h)
If no response to above: DHE 0.5–1 mg IV (after pre-treatment with antiemetic) — highly effective for status; or IV valproate 500 mg over 30 min

Avoid: Opioids (↑MOH risk, not superior to dopamine antagonists, addictive potential). Another triptan (already failed ×2; also CI within 24h of DHE).
Before discharge: Discuss preventive therapy (MIDAS Grade IV if frequent attacks); bridge with naproxen; follow-up neurology.

4.6 Preventive Treatment — Oral Agents, BoNT-A, CGRP mAbs ▶

INDICATIONS FOR PREVENTIVE THERAPY

Initiate prevention when ANY of the following present:

≥4 migraine days/month with significant disability (MIDAS ≥11, Grade III–IV)
≥8 headache days/month (risk of chronification)
Frequency: ≥3 attacks/month that significantly impair function despite optimal acute treatment
Acute medication overuse or contraindication to acute drugs
Chronic migraine (≥15 days/month)
Rare but devastating subtypes: Hemiplegic migraine, migraine with prolonged aura, basilar migraine
Patient preference (even with lower frequency if attacks are debilitating)

Goal: ≥50% reduction in migraine days/month. Must trial ≥3 months before declaring failure (adequate dose, adequate duration).

Oral Preventive Agents — Evidence Table

Drug	Class	Starting Dose	Target Dose	Evidence	Key Side Effects / Notes
Topiramate	Anticonvulsant	25 mg nightly	50–100 mg/day (divided)	Level A — AAN 2012; effective in CM/MOH	Cognitive slowing ("dopamax"), weight loss, paresthesias, kidney stones, glaucoma. Teratogen (cleft lip/palate). Monitor carbonic anhydrase. Target 100 mg (50 mg bid)
Valproate / Divalproex	Anticonvulsant	250 mg bid	500–1500 mg/day	Level A — AAN 2012	Teratogen (NTD) — ABSOLUTE CI in women of childbearing age without effective contraception; weight gain, tremor, alopecia, hepatotoxicity, pancreatitis; LFT + CBC at baseline
Propranolol	Beta-blocker	40 mg bid	80–240 mg/day	Level A — First-line	Bradycardia, hypotension, fatigue, depression, cold extremities. CI: asthma, COPD, DM on insulin (masks hypoglycemia), heart block. Reduce rizatriptan dose to 5 mg if combined.
Metoprolol	Beta-blocker (β1-selective)	50 mg daily	100–200 mg/day	Level A	Preferred in asthma (more β1-selective than propranolol, but still use caution)
Timolol	Beta-blocker	10 mg bid	10–30 mg/day	Level A — FDA-approved for migraine	Similar to propranolol; also available as ophthalmic (systemic absorption possible)
Amitriptyline	TCA	10 mg nightly	30–75 mg nightly	Level B (headache-specific); Level A for TTH prophylaxis	Sedation (benefit for sleep-disordered migraine), dry mouth, constipation, weight gain, orthostatic hypotension, QTc prolongation. QTc baseline ECG. Best given 2h before bed. Also treats comorbid depression/anxiety.
Venlafaxine	SNRI	37.5 mg daily	75–150 mg/day (ER)	Level B	Useful in migraine + depression/anxiety comorbidity; nausea initially; do not stop abruptly (discontinuation syndrome); hypertension at high doses
Candesartan	ARB	8 mg daily	16 mg daily	Level B (Scandinavian RCT)	Well-tolerated; useful in migraine + hypertension; CI: pregnancy, bilateral RAS; hyperkalaemia; good option when beta-blockers CI
Flunarizine	Ca-channel blocker (non-selective)	5 mg nightly	5–10 mg nightly	Level A (European guidelines); not FDA-approved in USA	Sedation, weight gain, depression, extrapyramidal symptoms (parkinsonism) — monitor long-term; do not use >6 months continuously
Magnesium glycinate/citrate	Mineral supplement	300 mg daily	400–600 mg/day	Level B (especially MwA and menstrual migraine)	GI upset at high doses; safe in pregnancy; deficiency linked to migraine pathogenesis
Riboflavin (B2)	Vitamin	400 mg daily	400 mg/day	Level B	Extremely safe; may turn urine yellow/orange (harmless); mitochondrial mechanism; takes ≥3 months for effect
Coenzyme Q10	Supplement	100 mg tid	300 mg/day	Level C	Safe; mitochondrial membrane stabilization; useful in pediatric migraine

🧠 Preventive Drug Selection — Comorbidity-Guided (Match Treatment to Patient Profile):

Comorbidity	Preferred Agent	Avoid
Hypertension	Propranolol, metoprolol, candesartan, lisinopril	Amitriptyline (if severe HTN)
Depression/Anxiety	Amitriptyline, venlafaxine	Topiramate (cognitive SE), beta-blockers (depression)
Epilepsy	Valproate, topiramate, lamotrigine	Beta-blockers (seizure threshold effect)
Obesity	Topiramate (weight loss), zonisamide	Amitriptyline, valproate, flunarizine (weight gain)
Asthma/COPD	Topiramate, valproate, amitriptyline, candesartan	Beta-blockers (bronchospasm)
Pregnancy	Propranolol, metoprolol, Mg, riboflavin, amitriptyline (low dose)	Topiramate (cleft palate), valproate (NTD) — absolutely avoid
Raynaud's / Cold extremities	Amitriptyline, topiramate, candesartan	Beta-blockers (vasoconstriction)
Insomnia	Amitriptyline (given at night)	Topiramate (can disturb sleep)

OnabotulinumtoxinA (BoNT-A) — PREEMPT Protocol

PREEMPT PROTOCOL — FDA/TGA APPROVED FOR CHRONIC MIGRAINE

Indication: Chronic migraine (≥15 days/month, ≥8 migraine features) — ≥3 months duration; failed ≥2 oral preventives; also effective in CM with MOH

Total dose: 155–195 units per treatment session (31–39 injection sites)

Injection sites (31 fixed + 8 flexible "follow the pain"):

Muscle Group	Units	Sites
Frontalis	20 U (10U/side)	4 sites (2/side)
Corrugator supercilii	10 U (5U/side)	2 sites (1/side)
Procerus	5 U	1 site (midline)
Occipitalis	30 U (15U/side)	6 sites (3/side)
Temporalis	40 U (20U/side)	8 sites (4/side)
Trapezius	30 U (15U/side)	6 sites (3/side)
Cervical paraspinal	20 U (10U/side)	4 sites (2/side)
Flexible additional sites	up to 40 U	up to 8 sites

Frequency: Every 12 weeks (3 months). Effect onset: 2–4 weeks. Full effect by session 2–3.

Key trials: PREEMPT 1 and PREEMPT 2 — ~56% reduction in headache days vs placebo (29%) at 24 weeks; ≥50% responder rate ~47% vs 35% placebo

SE: Neck pain, injection site pain, brow ptosis (avoid <1 cm above brow), head/neck weakness (temporary). Rare: dysphagia (if trapezius injected too deep)

CGRP Monoclonal Antibodies — Comparative Table

Drug	Target	Dose / Route / Frequency	Key Phase III Trial	Efficacy (≥50% responder)	Notes
Erenumab (Aimovig)	CGRP receptor	70 mg or 140 mg SC monthly	ARISE, STRIVE	~43% (EM), ~40% (CM) at 140 mg	First approved CGRP mAb; constipation notable AE (unique to receptor blockade); auto-injector; some patients may need dose escalation to 140 mg
Galcanezumab (Emgality)	CGRP ligand	120 mg SC monthly (240 mg loading × 1)	EVOLVE-1, EVOLVE-2 (EM); REGAIN (CM)	~61% (EM) at 3 months	Also approved for episodic cluster headache (300 mg SC monthly × 3 doses); loading dose may give faster onset; injection site reactions
Fremanezumab (Ajovy)	CGRP ligand	225 mg SC monthly OR 675 mg SC quarterly	HALO EM, HALO CM	~44% (EM), ~41% (CM)	Unique quarterly dosing option (convenience); effective in MOH subgroup; auto-injector
Eptinezumab (Vyepti)	CGRP ligand	100 mg IV q3 months (may increase to 300 mg)	PROMISE-1 (EM); PROMISE-2 (CM)	~50% (EM 100 mg), ~57% (EM 300 mg)	IV infusion only (30 min); fastest onset (within 24h of first infusion); useful when guaranteed adherence needed; superior efficacy at higher dose

🧠 CGRP mAb Clinical Pearls:

Safety: No liver toxicity, no CNS side effects, no teratogenicity data (avoid in pregnancy — limited data). Avoid in: active cardiovascular disease (CGRP is vasodilatory; uncertain CV implications), pregnancy, known hypersensitivity.
Constipation (erenumab): Dose-dependent; CGRP receptor blockade in gut. Manage with dietary fiber, osmotic laxatives. May switch to ligand-targeting mAb if intolerable.
Responder rate expectations: ~50% of patients achieve ≥50% reduction in migraine days (super-responders: ≥75% reduction). Assess after 3 months (3 injections). Give up to 6 months before declaring failure.
CGRP mAbs vs BoNT-A: No head-to-head RCTs. Both approved for CM. BoNT-A requires in-office procedure every 12 weeks; mAbs self-injected. May combine BoNT-A + mAb in refractory CM (off-label combination used in practice).
Rimegepant as preventive: 75 mg ODT every other day — approved as preventive (QOD dosing) in patients who also use it acutely; useful for low-frequency migraine prevention or those refusing injections.
Insurance/Access (Thailand): CGRP mAbs not yet in NHSO formulary (as of 2025); significant cost barrier; compassionate access programs available for some.

Special Populations — Migraine Treatment

Population	Acute Treatment	Preventive Treatment	Key Considerations
Pregnancy (T1–T3)	Paracetamol 1g (safest). NSAIDs: T1–T2 only (CI in T3: premature ductus closure). Triptans: Category C (limited data; sumatriptan registry reassuring). Metoclopramide/ondansetron for nausea.	Propranolol (preferred β-blocker). Mg 400 mg/day (safe T1–T3, also preeclampsia prevention). Riboflavin. Amitriptyline low dose. Avoid topiramate (cleft palate) and valproate (NTD — absolute CI).	Migraine often improves in T2–T3 (estrogen effect). Migraine with aura first onset in pregnancy → rule out cerebral venous thrombosis (MRI/MRV). Postpartum migraine flare common (estrogen drop).
Breastfeeding	Paracetamol (safe). NSAIDs: ibuprofen/naproxen (low milk transfer, safe). Sumatriptan (safe; low M:P ratio; pump-and-discard 12h). Avoid ergotamine (vasoconstriction in infant).	Propranolol, amitriptyline (safe, monitoring infant for sedation). Avoid valproate, topiramate (significant milk transfer).	LactMed database reference for drug-specific data. Many women afraid to treat — reassure safety of paracetamol + ibuprofen.
Elderly (>65)	Paracetamol first-line. NSAIDs with caution (GI, renal, CVD). Triptans: careful with cardiovascular risk assessment (coronary artery disease common). Avoid ergotamine.	Low-dose tricyclics (higher fall risk; start 5 mg). Gabapentin. Avoid topiramate (cognitive SE). CGRP mAbs: no age-related efficacy difference in trials but limited elderly data.	New-onset headache >50 years: red flag → rule out GCA (ESR, CRP), SOL, CVD. Migraine rarely starts de novo in elderly.
Cardiovascular Disease / High CV Risk	NSAIDs (ketorolac IV). Gepants (safe — no vasoconstriction). Lasmiditan (safe CVD — no vasoconstriction; CNS side effects). Avoid: triptans (coronary vasospasm), ergotamine (absolute CI).	Beta-blockers (propranolol — also cardioprotective). Candesartan/lisinopril (BP benefit). Avoid: triptans as daily rescue. CGRP mAbs: caution in recent MI/stroke (CGRP has vasodilatory CV protective role — theoretical concern).	Triptans contraindicated in: uncontrolled HTN, IHD, peripheral vascular disease, stroke/TIA history. Use gepants or lasmiditan as triptan-sparing alternatives.
Menstrual Migraine	Standard acute: NSAID + triptan. Frovatriptan/naratriptan (long T½): superior for prolonged menstrual attacks.	Mini-prophylaxis: Frovatriptan 2.5 mg bid × 6 days (Day −2 to +3 of menstruation); Naratriptan 1 mg bid; Naproxen 500 mg bid. Standard preventives if >3 menstrual cycles/year affected.	Pure menstrual migraine (ICHD-3 1.4.1.1): attack exclusively D−2 to D+3; 60% are MwoA. Perimenstrual estrogen drop = trigger. Transdermal estradiol patch (100 μg) during perimenstrual period (avoid oral estrogen — thrombosis risk).

Q: A 35-year-old woman with chronic migraine (18 days/month, 10 migraine features) failed topiramate 100 mg/day × 4 months and amitriptyline 50 mg × 3 months. She has no cardiovascular disease. What are the next management options and evidence base?

Assessment: Failed 2 adequate oral preventive trials (≥3 months each at therapeutic dose). Meets criteria for escalated prevention.

Options with evidence:

OnabotulinumtoxinA (BoNT-A) PREEMPT: FDA-approved for CM; 155–195 U every 12 weeks. PREEMPT 1 & 2: significant reduction in headache days. First choice if insurance covers / available.
CGRP monoclonal antibody:
- Erenumab 70–140 mg SC monthly (STRIVE: 50% responder rate 40%)
- Fremanezumab 225 mg monthly or 675 mg quarterly (HALO CM)
- Galcanezumab 120 mg monthly (REGAIN)
- Eptinezumab 100–300 mg IV q3 months (PROMISE-2: fastest onset)
Combination: If one class fails, may try BoNT-A + CGRP mAb (off-label; real-world evidence positive). Consider whether MOH also present → treat simultaneously.
Valproate: Level A evidence — but check reproductive status (absolute CI if pregnancy possible without effective contraception)

Additional: Assess and address MOH if acute medication ≥10–15 days/month; multidisciplinary approach (CBT for migraine, physiotherapy, sleep hygiene, trigger management).

4.7 Tension-Type Headache (TTH) ▶

ICHD-3 TTH DIAGNOSTIC CRITERIA (2.1–2.3)

A. ≥10 episodes on <15 days/month (episodic) or ≥15 days/month >3 months (chronic TTH 2.3)

B. Lasting 30 minutes to 7 days

C. ≥2 of 4 characteristics (mnemonic: BEND):

Bilateral location
Equals pressing/tightening quality (non-pulsating)
Not aggravated by routine physical activity
Dull/mild-to-moderate severity

D. BOTH of:

No nausea or vomiting
No more than one of: photophobia OR phonophobia (may have one but NOT both)

E. Not better accounted for by another ICHD-3 diagnosis

Key differentiator from migraine: TTH = bilateral + non-pulsating + not aggravated by activity + no nausea/vomiting + only one of photo/phono. Migraine = opposite pattern.

TTH Subtypes

Subtype	Frequency	ICHD-3 Code	Clinical Note
Infrequent episodic TTH	<1 day/month (<12 days/year)	2.1	Usually no preventive needed; OTC as needed
Frequent episodic TTH	1–14 days/month for ≥3 months	2.2	Consider prevention if disability; pericranial tenderness key finding
Chronic TTH	≥15 days/month >3 months	2.3	Often comorbid with depression/anxiety; MOH common; amitriptyline first-line

TTH Pathophysiology

Peripheral mechanism (episodic TTH): activation and sensitization of pericranial myofascial nociceptors → sensitization of spinal dorsal horn neurons. Pericranial tenderness on manual palpation (Total Tenderness Score) correlates with frequency. Central mechanism (chronic TTH): central sensitization of trigeminal nucleus caudalis + reduced pain inhibition (decreased serotonin, endorphins).

TTH Treatment — Abortive

Drug	Dose	Evidence Level	Notes
Aspirin	500–1000 mg	Level A	Most evidence; GI side effects
Ibuprofen	400–800 mg	Level A	Fastest onset of NSAIDs; superior to paracetamol in some studies
Naproxen	375–550 mg	Level A	Longer duration; useful for prolonged TTH episodes
Paracetamol	1000 mg	Level A	Safe; useful when NSAIDs CI; may be less effective than NSAIDs
Caffeine + analgesic	65 mg caffeine + NSAID	Level A	Combination superior to analgesic alone; limit caffeine (withdrawal headache)
Triptans	—	Not effective for TTH	Triptans work in migraine but NOT TTH — use to differentiate if uncertain diagnosis

TTH Prophylaxis

Drug	Dose	Evidence Level (EAN/EFNS)
Amitriptyline	30–75 mg nightly (start 10 mg)	Level A — most evidence for chronic TTH
Mirtazapine	15–30 mg nightly	Level B
Venlafaxine	75–150 mg/day	Level B
Clomipramine	75–150 mg/day	Level B
Maprotiline	75 mg/day	Level B
Mianserin	30–60 mg/day	Level B

Non-pharmacological for TTH (high evidence): Biofeedback (EMG), relaxation therapy, cognitive-behavioral therapy, physiotherapy (cervical manipulation, trigger point therapy). Often superior long-term to pharmacotherapy alone for chronic TTH.

4.8 Trigeminal Autonomic Cephalalgias — Cluster, PH, SUNCT/SUNA, Hemicrania Continua ▶

TAC OVERVIEW — KEY DIFFERENTIATORS

Feature	Cluster Headache	Paroxysmal Hemicrania (PH)	SUNCT / SUNA	Hemicrania Continua (HC)
Duration/attack	15–180 min	2–30 min	1–600 sec (SUNCT); 1 sec–10 min (SUNA)	Continuous (background) + exacerbations
Frequency	1–8/day (in bouts)	≥5/day (>50% time)	≥1/day (>50% time); up to 200/day	Continuous (no pain-free periods)
Autonomic features	Yes (ipsilateral)	Yes (ipsilateral)	Yes (ipsilateral); conjunctival injection + lacrimation prominent	Yes (ipsilateral, milder)
Sex predominance	M:F = 3:1	F:M = 2.5:1	M:F = 1.5:1	F:M = 2:1
Indomethacin response	No	YES — absolute	No	YES — absolute
Key treatment	O2 + sumatriptan SC; verapamil preventive	Indomethacin (diagnostic + therapeutic)	Lamotrigine; IV lidocaine	Indomethacin (diagnostic + therapeutic)
ICHD-3 Code	3.1	3.2	3.3/3.4	3.4

Cluster Headache — ICHD-3 3.1

CLUSTER HEADACHE DIAGNOSTIC CRITERIA

A. At least 5 attacks fulfilling B–D

B. Severe/very severe unilateral orbital, supraorbital, and/or temporal pain lasting 15–180 min (untreated)

C. Either or both:

≥1 ipsilateral cranial autonomic symptom: conjunctival injection, lacrimation, nasal congestion, rhinorrhea, eyelid edema, facial sweating/flushing, miosis/ptosis (partial Horner), ear fullness
Sense of restlessness or agitation

D. Attacks have circadian periodicity (same time daily, nocturnal peak 1–2 AM) and/or circannual pattern (bout same season yearly)

E. Episodic CH (3.1.1): clusters of 7 days–1 year separated by ≥3-month pain-free periods. Chronic CH (3.1.2): no remission or remission <3 months for >1 year.

Cluster Headache Pathophysiology

Hypothalamic activation (posterior hypothalamus — suprachiasmatic nucleus dysfunction → circadian pattern). Trigeminovascular activation → pain (V1 distribution). Parasympathetic activation via sphenopalatine ganglion → autonomic features (lacrimation, rhinorrhea, conjunctival injection). Sympathetic deficiency → partial Horner (ptosis + miosis but NOT anhidrosis — only superior cervical ganglion sympathetics affected). Unique feature: patient paces, cannot lie still (contrast with migraine → lies in dark quiet room).

Cluster Headache Treatment

Phase	Drug	Dose	Evidence	Notes
Acute Attack	Oxygen (100%)	12–15 L/min via non-rebreather mask × 15–20 min	Level A — AAN	Most effective, safest; must use non-rebreather mask (not nasal cannula); response within 15 min; no systemic SE
	Sumatriptan SC	6 mg SC	Level A	Fastest pharmacologic option; limit 2 injections/24h; high responder rate (~74%)
	Sumatriptan nasal / Zolmitriptan nasal	Suma nasal 20 mg; Zolmi nasal 5 mg	Level A	Alternative if SC injection not tolerated; slower than SC
Preventive (episodic bout)	Verapamil	240–960 mg/day (divided tid)	Level A — First-line preventive	Cardiac monitoring: ECG baseline + q2 weeks with dose increase (PR prolongation, AV block); titrate up by 80 mg/week; 360–480 mg/day usually effective target
	Lithium	600–1200 mg/day (levels 0.4–0.8 mEq/L)	Level B — especially chronic CH	Monitor levels, renal, thyroid; narrow therapeutic window; interactions with NSAIDs, diuretics
	Topiramate	100–200 mg/day	Level B	Alternative when verapamil CI/ineffective
	Galcanezumab	300 mg SC monthly × 3 months	Level A (CONQUER trial)	FDA-approved for episodic CH; only CGRP mAb with CH indication; given monthly × 3 doses in bout
	Prednisone bridge	60–100 mg/day × 5 days then taper	Level B	Transitional prevention while verapamil takes effect (2–3 weeks); GON block (methylprednisolone) alternative bridge

🧠 Cluster Headache vs. Migraine — Key Clinical Differences:

Patient behavior: CH patient paces, rocks, cannot stay still (agitation); migraine patient lies still in dark quiet room (photophobia → movement worsens)
Timing: CH attacks like clockwork — same time daily (circadian), often 1–3 AM (nocturnal hypothalamic activation); migraine irregular timing
Duration: CH = 15–180 min (usually peaks in 30–45 min); migraine = 4–72h
Autonomic features: CH = prominent ipsilateral Horner, lacrimation, rhinorrhea; migraine = no autonomic features (or bilateral photophobia/phonophobia)
Oxygen therapy: Highly effective in CH (NNT ~2); NOT effective in migraine
Verapamil monitoring: HIGH-DOSE verapamil (up to 960 mg/day) for CH — ECG mandatory at each dose increment; heart block and PR prolongation real risks

Paroxysmal Hemicrania (PH) — ICHD-3 3.2

Diagnostic criteria: ≥20 attacks of severe unilateral orbital/supraorbital/temporal pain lasting 2–30 min + ipsilateral autonomic features (same as CH criteria C) + frequency >5/day for >50% time + absolute response to indomethacin.

Indomethacin test (diagnostic + therapeutic): 25 mg tid × 3 days; if partial response → 50 mg tid × 3 days; if partial → 75 mg tid × 3 days. Complete response = PH confirmed. Maintenance: lowest effective dose (often 25–50 mg tid); use with PPI (GI protection).

SUNCT / SUNA — ICHD-3 3.3/3.4

SUNCT (Short-lasting Unilateral Neuralgiform headache with Conjunctival injection and Tearing): attacks 1–600 sec, conjunctival injection + lacrimation prominent, frequency up to 200/day. SUNA (Short-lasting Unilateral Neuralgiform headache with cranial Autonomic symptoms): same but only one or no conjunctival/lacrimation feature.

Treatment: No acute treatment effective (attacks too short). Prevention: Lamotrigine 25–300 mg/day (Level A); Topiramate 50–300 mg/day; IV Lidocaine (acute hospital prevention in refractory); Gabapentin, carbamazepine (variable response). Important: must rule out secondary cause (posterior fossa lesion — MRI pituitary, posterior fossa mandatory).

Hemicrania Continua (HC) — ICHD-3 3.4

Criteria: Unilateral headache for >3 months (continuous, no pain-free periods) + moderate baseline + exacerbations of severe pain + ipsilateral autonomic features during exacerbations + absolute indomethacin response. Treatment: Same as PH — indomethacin is diagnostic + therapeutic (absolute response required for diagnosis). Celecoxib alternative if indomethacin not tolerated. Secondary HC-like: pituitary adenoma, cavernous sinus lesion — MRI essential.

Q: A 45-year-old man presents with 3-week history of daily severe right orbital pain, lasting 45 minutes, occurring at 11 PM nightly. Associated with right eye tearing and ptosis. He paces around during attacks. Temp/BP/neuro exam normal. What is the diagnosis and immediate management?

Diagnosis: Episodic Cluster Headache (ICHD-3 3.1.1)
Criteria met: Severe unilateral orbital pain ✓; 45 min duration (15–180 min) ✓; ipsilateral autonomic (lacrimation + ptosis/miosis = partial Horner) ✓; restlessness/agitation (pacing) ✓; circadian (11 PM nightly) ✓; 3-week bout duration ✓

Workup: MRI brain with pituitary protocol (exclude secondary CH — cavernous sinus, pituitary, orbital lesion) particularly given this is first presentation. ECG before starting verapamil.

Immediate Management:

Acute attacks: Oxygen 100% 12–15 L/min via non-rebreather mask × 15–20 min (Level A; most effective first-line); prescribe home oxygen tank. PLUS/OR Sumatriptan SC 6 mg auto-injector (Level A; limit 2/day).
Transitional prevention (bridge): Prednisone 60 mg × 5 days then taper over 2 weeks — rapid relief while verapamil takes effect. OR GON block (methylprednisolone ipsilateral).
Preventive (maintenance): Verapamil 240 mg/day (80 mg tid) → titrate to 360–480 mg/day. ECG monitoring before each dose increase (q2 weeks). Continue through bout duration (typically 6–12 weeks then taper).

Avoid: Oral triptans/sumatriptan nasal (slower onset; less effective than SC for CH). Opioids (not indicated; MOH risk; ineffective).

4.9 Trigeminal Neuralgia & Cranial Neuralgias ▶

TRIGEMINAL NEURALGIA — ICHD-3 13.1 / Classic TN

A. Recurrent paroxysms of unilateral facial pain in the distribution(s) of one or more divisions of the trigeminal nerve with no radiation beyond, fulfilling B and C

B. Pain has all of the following characteristics:

Lasting from a fraction of a second to 2 minutes
Severe intensity
Electric shock-like, shooting, stabbing, or sharp in quality

C. Precipitated by innocuous stimuli within the affected trigeminal distribution (trigger: touch face, eating, talking, cold air, brushing teeth)

D. Not better accounted for by another ICHD-3 diagnosis

Distribution: V2 (maxillary) most common (37%), V3 (mandibular) 34%, V2+V3 combined 29%, V1 (ophthalmic) rare (<5%). Right side more common (60%). Bilateral <3% (rule out MS).

TN Classification

Type	ICHD-3	Cause	MRI Finding	Implication
Classic TN	13.1.1	Neurovascular compression (superior cerebellar artery most common)	MRI FIESTA/CISS: contact between vessel and trigeminal nerve root entry zone (REZ)	Best surgical candidate (MVD highly effective)
Secondary TN	13.1.2	Structural lesion (MS plaque, tumor, AVM, meningioma)	MRI shows causative lesion	Treat underlying cause; if MS → carbamazepine still first-line medical
Idiopathic TN	13.1.3	No vascular compression or structural lesion	Normal MRI	Medical treatment; may have partial surgical response

TN Treatment Algorithm

Treatment	Dose	Evidence	Notes
Medical (First-Line)
Carbamazepine	100 mg bid → 400–800 mg bid (target 200–400 mg tid)	Level A — most evidence; NNT ~2	Sodium channel blocker; reduce pain paroxysms in 70–80%. Monitor CBC + LFT + Na (hyponatremia). HLA-B*1502 screening before use in Asian patients (risk SJS/TEN). Drug interactions (CYP3A4 inducer). Titrate slowly: 100 mg bid → increase weekly. Therapeutic level: 4–12 μg/mL.
Oxcarbazepine	150 mg bid → 600–900 mg bid	Level B — fewer drug interactions, better tolerated than CBZ	Better tolerability than CBZ. Monitor Na (SIADH risk). Same HLA-B*1502 concern. Pro-drug of CBZ active metabolite. Preferred in elderly, polypharmacy.
Lamotrigine	25 mg → 200–400 mg/day (very slow titration)	Level C — add-on	Add-on to CBZ/OXC; Stevens-Johnson risk if titrated too fast (must titrate slowly over 6–8 weeks)
Baclofen	10–80 mg/day (divided)	Level C — add-on	GABA-B agonist; add-on or if CBZ/OXC CI/failed; withdrawal seizures if stopped abruptly
Gabapentin	900–3600 mg/day	Level C — less evidence than CBZ	Useful add-on; better in TN with continuous background pain component
Surgical (When Medical Fails)
Microvascular Decompression (MVD)	—	Level A — most durable	Posterior fossa craniotomy; Teflon pad between vessel and nerve. Best outcomes (80–90% pain-free immediately; 70% at 10 years). Indicated for classic TN with NVC on MRI. Not for elderly high surgical risk.
Gamma Knife Radiosurgery	—	Level A	Focused radiation to REZ; no general anesthesia needed; response delayed 1–6 months; useful in elderly/high surgical risk; may cause numbness
Percutaneous rhizotomy (balloon, glycerol, RF)	—	Level B	Immediate effect; high recurrence rate (<MVD); numbness/corneal anesthesia risk

🧠 TN vs. Other Facial Pain:

Condition	Duration	Trigger	Key Feature
Trigeminal Neuralgia	Sec (fraction to 2 min)	Light touch	Electric shock; paroxysmal; no autonomic features
SUNCT/SUNA	1 sec–10 min	Touch (often orbital)	Autonomic features (conjunctival injection); high frequency
Dental pain	Continuous	Cold, biting	Throbbing; localized to tooth; dental exam abnormal
Post-herpetic neuralgia (PHN)	Continuous + paroxysms	Touch (allodynia)	History of zoster rash; dermatomal; burning quality
Atypical facial pain	Hours–continuous	Psychological stress	Crossing dermatomal lines; psychiatric comorbidity
Glossopharyngeal neuralgia	Sec (like TN)	Swallowing, talking	Throat/ear pain; tonsillar fossa trigger

Post-Herpetic Neuralgia (PHN)

Definition: Pain persisting >3 months after acute herpes zoster rash in same dermatomal distribution. Risk: elderly, immunocompromised, ophthalmic zoster (HZO — V1), inadequately treated acute zoster.

Prevention: Early antiviral treatment within 72h of rash onset (acyclovir/valacyclovir) reduces PHN risk. Shingrix vaccine (adjuvanted recombinant) >90% effective prevention of HZ and PHN in ≥50 years.

Treatment:

Drug	Dose	Evidence
Gabapentin	300 mg tid → 900–3600 mg/day	Level A; first-line
Pregabalin	75 mg bid → 150–300 mg bid	Level A; faster titration, better adherence
Tricyclic antidepressants (amitriptyline, nortriptyline)	10–75 mg nightly	Level A; NNT ~3
Duloxetine / Venlafaxine	30–60 mg/day / 75–150 mg/day	Level B
Topical lidocaine patch (5%)	Apply to affected area ×12h/day	Level A; minimal systemic absorption
Topical capsaicin patch (8%)	Apply 60 min by specialist	Level A; single application lasts 3 months
Opioids (tramadol, oxycodone)	Variable	Level A; use as 3rd-line (risk: dependence, MOH)

4.10 Secondary Headache — Red Flags, SNOOP4, Neuroimaging Criteria ▶

SNOOP4 RED FLAGS — INDICATIONS FOR URGENT NEUROIMAGING

Letter	Red Flag	Differential Diagnosis
S	Systemic symptoms or signs: fever, weight loss, jaw claudication, scalp tenderness	Meningitis, encephalitis, GCA (ESR, CRP, temporal artery biopsy), systemic malignancy
S	Secondary risk factors: HIV/immunocompromised, malignancy, pregnancy, anticoagulation, OSA (ICH risk)	CNS opportunistic infection (toxo, crypto), brain metastases, cerebral venous thrombosis
N	Neurological symptoms or signs: focal deficits, altered consciousness, papilledema, meningismus	SOL, ICH, meningitis, SAH, CVST, hypertensive encephalopathy, carotid/vertebral dissection
O	Onset sudden / thunderclap (≤1 min to maximal intensity)	SAH (MUST exclude with CT/LP), CVST, RCVS, vertebral dissection, pituitary apoplexy
O	Older age: new headache onset >50 years (especially >65)	GCA, SOL (neoplasm, SDH), cerebrovascular disease
P	Progressive headache: new/changing headache worsening over weeks	SOL (primary/metastatic brain tumor), chronic SDH, IIH, abscess
P	Positional: worse lying flat (↑ ICP) or upright (CSF leak)	IIH (worse lying flat at night, improves upright), CSF leak (orthostatic headache worse upright)
P	Precipitated by Valsalva (cough, sneeze, straining) or exertion	Arnold-Chiari malformation, posterior fossa tumor, cardiac cause, Chiari I
P	Papilledema on fundoscopy	IIH, SOL with raised ICP, CVST, malignant hypertension — urgent LP/MRI/ophthalmology

Thunderclap Headache — Differential Diagnosis Algorithm

Definition: Reaches maximal severity within 1 minute; most severe headache of life. ALWAYS a red flag until proven otherwise.

Priority	Diagnosis	Workup	Key Feature
1 (MUST EXCLUDE)	Subarachnoid Hemorrhage (SAH)	CT head non-contrast first; if negative → LP (xanthochromia 12h–2 weeks; RBC count); CTA if CT negative + LP positive/equivocal → detect aneurysm	"Worst headache of life"; meningismus; may have brief LOC; sentinel headache in 20%
2	Cerebral Venous Sinus Thrombosis (CVST)	MRI + MRV brain	Subacute onset; focal deficits; seizures; OCP/pregnancy/hypercoagulable state risk
3	Reversible Cerebral Vasoconstriction Syndrome (RCVS)	CTA/MRA (beaded arteries); MRI FLAIR (cortical SAH)	Recurrent thunderclap headaches over days–weeks; young women; drug trigger (sympathomimetics, SSRIs, triptans overuse); RCVS resolves in 1–3 months
4	Vertebral/Carotid Artery Dissection	MRI + MRA neck (fat-sat sequences)	Neck pain ± Horner; posterior circulation sx (dissection); pulsatile tinnitus (carotid); often traumatic/chiropractic trigger
5	Pituitary Apoplexy	MRI pituitary (hemorrhage/infarction into adenoma)	Bitemporal hemianopia; sudden onset; known pituitary adenoma; III/VI nerve palsy; steroids urgently if adrenal crisis
6	Hypertensive Emergency/PRES	BP >180/120 + MRI FLAIR (posterior white matter edema)	Seizures; visual disturbance; BP crisis
7	Primary Thunderclap Headache (benign)	Diagnosis of exclusion — all secondary causes excluded	Single episode; no recurrence; normal CT/LP/MRA; no trigger

🧠 Ottawa SAH Rule (for CT-negative thunderclap headache): If CT negative and any of these present → LP mandatory:

Age ≥40
Neck pain or stiffness
Witnessed LOC
Onset with exertion
Thunderclap headache (maximal at onset)
Limited neck flexion on exam

CT sensitivity for SAH: 98% within 6h of onset, decreasing to 85–90% at 24h. LP remains necessary in appropriate clinical context even if CT negative. CTA can detect aneurysm ≥3 mm (sensitivity ~98%) and may replace conventional angiography in many centers.

Idiopathic Intracranial Hypertension (IIH) — Pseudotumor Cerebri

IIH MODIFIED DANDY CRITERIA

A. Symptoms/signs of ↑ICP: headache (worsened lying, improves upright), pulsatile tinnitus, visual obscurations, diplopia (VI palsy)

B. Papilledema (not always present — "IIH without papilledema" recognized)

C. Normal neurological exam except VI nerve palsy

D. Normal neuroimaging (MRI: empty sella, flattening of posterior sclera, distension of optic nerve sheath, tortuosity of optic nerve — all indirect signs)

E. LP opening pressure >25 cmH₂O (in non-obese adults); CSF composition normal

F. No other cause identified

Risk factors: Obese women of childbearing age (BMI >30), tetracycline, vitamin A toxicity, steroids withdrawal, contraceptives

IIH Treatment: Weight loss (primary — even 5–10% reduces ICP significantly); Acetazolamide 250 mg–4 g/day (carbonic anhydrase inhibitor; reduces CSF production); serial LP (temporal relief); optic nerve sheath fenestration (if vision threatened); VP shunt or lumboperitoneal shunt (refractory); topiramate (carbonic anhydrase + weight loss effect).

Monitoring: Regular visual field testing (Goldmann/automated perimetry) — vision loss is the feared complication.

Giant Cell Arteritis (GCA) — Headache in Elderly

Must consider in ALL new-onset headache >50 years. Granulomatous vasculitis of medium/large vessels (temporal artery, ophthalmic artery). Features: unilateral temple headache, scalp tenderness, jaw claudication (pathognomonic), diplopia, amaurosis fugax (optic artery ischemia), ESR >50 mm/h, CRP elevated, temporal artery biopsy (skip lesions — take long segment ≥2 cm). Treatment BEFORE biopsy: Prednisolone 1 mg/kg/day (up to 60 mg) if high suspicion — do not wait for biopsy; start steroids immediately to prevent permanent vision loss (biopsy remains positive for 2 weeks after steroid start).

Q: A 55-year-old obese woman (BMI 32) presents with 3-month history of daily headache worse in the morning and at night, pulsatile tinnitus, and two episodes of brief visual blurring. Fundoscopy shows bilateral papilledema. MRI brain is normal. What is the diagnosis, and what is the management?

Diagnosis: Idiopathic Intracranial Hypertension (IIH) — Modified Dandy criteria met: symptoms of ↑ICP (morning headache, pulsatile tinnitus, visual obscurations) + papilledema + normal MRI + obese woman of reproductive age (classic demographic).

Urgent next step: LP — measure opening pressure (>25 cmH₂O confirms) + CSF analysis (normal composition). Also: MRI/MRV to exclude CVST (secondary cause of raised ICP).

Management:

Weight loss: Primary treatment — 5–10% weight reduction significantly lowers ICP; dietary counseling; referral to bariatric program if BMI ≥35
Acetazolamide: 250 mg bid → titrate to 1–4 g/day as tolerated. Evidence: IIHTT trial — improved visual field + perimetry + reduced LP pressure. SE: paresthesias (common), GI upset, hyponatremia, teratogenicity (avoid in pregnancy)
Serial LP: Symptomatic relief; not primary treatment (recurrence immediate)
Ophthalmology urgent: Visual field testing (Goldmann perimetry) — monitor for vision loss (optic atrophy). If rapidly declining vision → surgical intervention (optic nerve sheath fenestration or CSF shunt)
Avoid precipitants: Tetracyclines, vitamin A supplements, high-dose steroids withdrawal

4.REF Key References & Evidence Base ▶

INTERNATIONAL GUIDELINES & CLASSIFICATION
1. Headache Classification Committee of the International Headache Society (IHS). The International Classification of Headache Disorders, 3rd edition (ICHD-3). Cephalalgia. 2018;38(1):1–211.
2. Eigenbrodt AK, et al. Diagnosis and management of migraine in ten steps. Nat Rev Neurol. 2021;17(8):501–514.
3. Diener HC, et al. (European Headache Federation). European position statement on the use of monoclonal antibodies targeting the calcitonin gene related peptide (CGRP) or its receptor in migraine prevention. J Headache Pain. 2019;20(1):22.

AAN/AHS PRACTICE GUIDELINES — MIGRAINE
4. Silberstein SD, et al. Evidence-based guideline update: Pharmacologic treatment for episodic migraine prevention in adults. Neurology. 2012;78(17):1337–1345. [Level A: topiramate, valproate, metoprolol, propranolol, timolol]
5. Simpson DM, et al. Practice guideline update summary: Botulinum neurotoxin for the treatment of blepharospasm, cervical dystonia, adult spasticity, and headache. Neurology. 2016;86(19):1818–1826. [BoNT-A PREEMPT Level A for Chronic Migraine]
6. Ailani J, et al. The American Headache Society Consensus Statement: Update on integrating new migraine treatments into clinical practice. Headache. 2021;61(7):1021–1039.

LANDMARK CLINICAL TRIALS
7. PREEMPT 1 & 2: Aurora SK, et al. OnabotulinumtoxinA for treatment of chronic migraine: results from the double-blind, randomized, placebo-controlled phase of the PREEMPT 1 and PREEMPT 2 trials. Cephalalgia. 2010;30(7):793–803, 804–814.
8. STRIVE (Erenumab): Goadsby PJ, et al. A controlled trial of erenumab for episodic migraine. N Engl J Med. 2017;377:2123–2132.
9. EVOLVE-1 & EVOLVE-2 (Galcanezumab): Stauffer VL, et al. Evaluation of galcanezumab for the prevention of episodic migraine. JAMA Neurol. 2018;75(9):1080–1088.
10. HALO CM (Fremanezumab): Silberstein SD, et al. Fremanezumab for the preventive treatment of chronic migraine. N Engl J Med. 2017;377:2113–2122.
11. PROMISE-1 & PROMISE-2 (Eptinezumab): Ashina M, et al. Eptinezumab in episodic and chronic migraine: 2 randomized clinical trials. Neurology. 2020;94(12):e1287–e1298.
12. SPARTAN (Rimegepant): Lipton RB, et al. Rimegepant, an oral calcitonin gene-related peptide receptor antagonist, for migraine. N Engl J Med. 2019;381:142–149.
13. IIHTT (Acetazolamide in IIH): Wall M, et al. The idiopathic intracranial hypertension treatment trial. JAMA Neurol. 2014;71(6):693–701.
14. CONQUER (Galcanezumab for Cluster HA): Goadsby PJ, et al. Randomized controlled trial of galcanezumab in episodic cluster headache. N Engl J Med. 2019;381:132–141.

THAI & ASIA-PACIFIC GUIDELINES
15. Thai Headache Society. Clinical Practice Guidelines for Migraine. 2020. [CPG Migraine Thailand — ICHD-3 based, stratified care, IV rescue protocols]
16. Soontrapa P. Management of Difficult to Treat Primary Headache. Siriraj Hospital CME 2025.
17. Chotinaiwattarakul W. How to Deal with Common Primary Headache Disorders. Thailand CME Lecture 2024.
18. Surat Thansetthakarn. Headache Disorders: Practical Approach. Regional CME Lecture 2024.

PATHOPHYSIOLOGY & SPECIAL TOPICS
19. Edvinsson L, et al. CGRP as the target of new migraine therapies — successful translation from bench to clinic. Nat Rev Neurol. 2018;14(6):338–350.
20. Noseda R, Burstein R. Migraine pathophysiology: anatomy of the trigeminovascular pathway and associated neurological symptoms, cortical spreading depression, sensitization, and modulation of pain. Pain. 2013;154(Suppl 1):S44–S53.
21. Olesen J. Headache Classification Committee. ICHD-3 comments — cluster headache diagnostic criteria and treatment evidence review. Cephalalgia. 2018;38(3):339–345.
22. Boes CJ, et al. SUNCT syndrome: a review of 28 cases. Brain. 2003;126(Pt 4):730–737.
23. Mathew NT. Pathophysiology of chronic migraine and mode of action of preventive medications. Headache. 2011;51(Suppl 2):84–92. [MOH mechanism and prevention]
24. Zakrzewska JM, Linskey ME. Trigeminal neuralgia. BMJ. 2014;348:g474. [TN diagnosis and treatment evidence review]
25. Lempert T, et al. Vestibular migraine: Diagnostic criteria. Consensus document of the Classification Committee of the Bárány Society and the International Headache Society. J Vestib Res. 2022;32(1):1–6.

SECONDARY HEADACHE & EMERGENCIES
26. Perry JJ, et al. Sensitivity of computed tomography performed within six hours of onset of headache for diagnosis of subarachnoid haemorrhage: prospective cohort study. BMJ. 2011;343:d4277. [Ottawa SAH Rule validation]
27. Ferro JM, et al. Diagnosis and management of cerebral venous thrombosis. Stroke. 2017;48(4):e111–e135.
28. Ducros A. Reversible cerebral vasoconstriction syndrome. Lancet Neurol. 2012;11(10):906–917.
29. Mollan SP, et al. Idiopathic intracranial hypertension: consensus guidelines on management. J Neurol Neurosurg Psychiatry. 2018;89(10):1088–1100.
30. Hellmann DB. Giant cell arteritis, polymyalgia rheumatica, and Takayasu's arteritis. In: Goldman-Cecil Medicine, 26th ed. Elsevier, 2020.

5. Neuromuscular Disorders

Neuromuscular disorders encompass diseases of the motor neuron, peripheral nerve, neuromuscular junction (NMJ), and muscle. This section covers MG (with Thai guideline & targeted therapies), GBS/CIDP (EAN 2023), motor neuron diseases (ALS with EAN 2024, SMA gene therapies, Kennedy disease), myopathies (systematic approach, IIM with MSA-based classification), and other NMJ disorders at subspecialist depth.

▼5.1 Myasthenia Gravis (MG)

Pathogenesis & NMJ Anatomy

The neuromuscular junction (NMJ) consists of presynaptic motor nerve terminal, synaptic cleft, and postsynaptic muscle endplate. ACh is released, crosses the cleft, and binds nicotinic AChR clustered at the endplate via the agrin→LRP4→MuSK→rapsyn signaling pathway. MG is an autoimmune disorder with antibodies targeting postsynaptic NMJ components.

🔑 Three Mechanisms of AChR Endplate Pathology (Neurotherapeutics 2016):
1. Complement-mediated lysis: AChR-IgG1/IgG3 → MAC (membrane attack complex) → endplate destruction
2. Cross-linkage & internalization: Antibody cross-links AChR → accelerated endocytosis/degradation (antigenic modulation)
3. ACh binding site blockade: Antibodies directly block ACh from binding AChR

🧬 Pathogenesis Cascade

Genetic predisposition (HLA-B8, A1, DRw3 for EOMG; HLA-A3, B7, DRw2 for LOMG; CTLA4, TNFRSF11A, AIRE) + triggers (thymic pathology, checkpoint inhibitors, penicillamine, interferons, statins) → altered Th1/Th2 balance, ↑Th17/Tfh, ↓Treg/Breg → B cell activation → pathogenic autoantibodies

MG Subgroup Classification (NEJM 2016;375:2570-81)

Subgroup	Age / Sex	HLA	Thymus	Antibody / IgG	Key Features
EOMG	<50 yr; F:M 3:1	B8/A1/DRw3	Lymphoid follicular hyperplasia	AChR-Ab / IgG1	Best thymectomy response
LOMG	>50 yr; M:F 1.5:1	A3/B7/DRw2	Thymic atrophy	AChR-Ab / IgG1,3	May have anti-titin/ryanodine
TAMG	Any age	Variable	Thymoma	AChR + anti-striated muscle/titin/ryanodine / IgG1,3	30-60% of thymomas develop MG; associated thyroid disease ~15%
OMG (Class I)	Variable	Variable	Variable	Low-titer AChR / IgG1,3	Ocular only; 50% generalize within 2 years
MuSK-MG	Any; F:M 9:1	DR14-DQ5	Normal thymus	MuSK-Ab / IgG4	Bulbar-predominant; facial/tongue atrophy; poor AChEI response; PLEX > IVIG; rituximab early
LRP4-MG	F:M 2.5:1	Variable	Variable	LRP4-Ab / IgG1,2	Generally milder course
Seronegative MG	Variable	Variable	Variable	No detectable Ab	~10% of MG; may have low-affinity AChR-Ab or clustered AChR-Ab

Clinical Features

Hallmark: Fatigable, fluctuating weakness — worse with exertion, better with rest. Ocular symptoms at onset in ~50%, progressing to generalized in ~80% within 1 month of first symptom.

Region	Symptoms/Signs
Ocular	Asymmetric ptosis (worse at end of day); diplopia; orbicularis oculi weakness (peek sign)
Bulbar	Dysarthria (nasal speech); dysphagia; jaw fatigue while chewing
Facial	Myasthenic snarl (transverse smile); facial diplegia
Limb	Proximal > distal; upper > lower extremity; neck flexor/extensor weakness
Respiratory	Dyspnea; orthopnea; inability to count to 20 in one breath (SBC < 20 → ICU)

MGFA Clinical Classification

Class	Description
I	Ocular MG only — any ocular muscle weakness; may have weakness of eye closure
II	Mild generalized — ocular weakness of any severity + mild weakness of other muscles
IIa	Predominantly affecting limb/axial muscles
IIb	Predominantly affecting oropharyngeal/respiratory muscles
III	Moderate generalized
IV	Severe generalized
V	Intubation required (with or without mechanical ventilation) = Myasthenic Crisis

Diagnosis

🔬 Diagnostic Approach

Serology: AChR-Ab (sensitivity: generalized 85%, ocular 50%); MuSK-Ab (5-8%); LRP4-Ab (1-3%); anti-striated muscle/titin/ryanodine (thymoma screening)
Electrodiagnosis — RNS (3 Hz): Decrement ≥10% at 4th-5th stimulus (proximal muscles: trapezius, nasalis, deltoid); sensitivity 50-70% gMG, 30% OMG
Electrodiagnosis — SFEMG: Increased jitter/IPI variability; sensitivity >95% — most sensitive test
Pharmacologic testing: Edrophonium (Tensilon) test — sensitivity ~80% for ptosis/ophthalmoparesis; Ice pack test: apply ice to closed eye 2min → improvement of ptosis ≥2mm (sensitivity ~80%, specificity ~100%)
CT Chest: All newly diagnosed MG — screen for thymoma

AChR-Ab vs MuSK-Ab MG — Critical Comparison

Feature	AChR-Ab MG (85%)	MuSK-Ab MG (5-8%)
Antibody class	IgG1/IgG3 (complement-fixing → MAC)	IgG4 (non-complement; disrupts MuSK-LRP4 → impaired AChR clustering)
Clinical pattern	Ocular ± generalized; thymoma 10-15%	Oculobulbar-predominant; facial/tongue atrophy; respiratory crisis more common; NO thymoma association
RNS / SFEMG	Decrement ≥10% in 50-70% / Jitter+	Variable; may need proximal/facial muscles; SFEMG highly sensitive
AChEI response	Good (pyridostigmine effective)	Poor or paradoxical worsening at higher doses
PLEX response	Good	Excellent (preferred over IVIG for MuSK)
IVIG response	Good	Less predictable / less effective
Rituximab	Moderate; uncertain in refractory	Excellent — consider early as 2nd-line IS
Thymectomy	Beneficial: thymoma → always; non-thymoma EOMG → MGTX trial	NOT indicated

Treatment — Comprehensive Stepwise Approach

💊 Thai MG Treatment Guideline (Siriraj/SNAC Protocol) + International Standards

Principles: Symptom control → immunosuppression → steroid-sparing → rescue → targeted therapy. IS dosing adjustments no more frequent than q3-6 months. Lifelong IS often needed.

Line	Agent	Starting → Maintenance Dose	Onset	Key AEs / Monitoring
1st — Symptomatic	Pyridostigmine	60 mg q6h → 60-120 mg q3-8h (max 480 mg/d); MuSK: lower doses	15-30 min	Cholinergic crisis (overdose): SLUDGE (salivation, lacrimation, urination, defecation, GI cramps, emesis); fasciculations, bradycardia
2nd — IS Induction	Prednisone/Prednisolone	Siriraj protocol: 10 mg/d → ↑10 mg/wk to 0.75-1 mg/kg/d (or start 60-100 mg/d if severe); maintain 2 mo → taper 5 mg q2-4wk	2-4 wk	⚠️ Transient worsening first 2 wk (especially at high initial dose — consider inpatient for severe); metabolic syndrome, osteoporosis, glucose
2nd — IS Induction	Thymectomy	Thymoma → resect if feasible; Non-thymoma + age 18-50 + AChR/seroneg generalized → thymectomy when stabilized	6-12 mo benefit	MGTX 2016 (NEJM): thymectomy + pred vs pred alone → better QMG score, lower steroid dose, less azathioprine at 3 yr
3rd — Steroid-sparing	Azathioprine	50 mg/d → 2-3 mg/kg/d	12-18 mo	Check TPMT before; CBC+LFT q4wk initially; risk: myelosuppression, hepatotoxicity, pancreatitis
	Mycophenolate mofetil (MMF)	500 mg BID → 1000-1500 mg BID	2-12 mo	GI intolerance, cytopenias; teratogenic (Category X)
	Cyclosporine	100 mg BID → 3-6 mg/kg/d	1-3 mo	Nephrotoxicity, HTN, tremor; monitor trough levels + Cr
	Methotrexate	10 mg/wk → 20 mg/wk	2-6 mo	Hepatotoxicity, myelosuppression; supplement folic acid
4th — Rescue/Acute	IVIG	2 g/kg over 5 days (0.4 g/kg/d × 5)	Days to 1-2 wk	Headache, aseptic meningitis, thrombosis, renal (sucrose); check IgA deficiency (anaphylaxis risk)
4th — Rescue/Acute	Plasma Exchange (PLEX)	5 exchanges EOD over 10-14 days	Days (faster than IVIG)	Hypotension, coagulopathy, line sepsis; preferred for MuSK-MG, crisis, pre-thymectomy
5th — Refractory	Rituximab	375 mg/m² weekly × 4 (or 750 mg/m² × 2, 2 wk apart; or low-dose 500 mg single)	1-3 mo	Anti-CD20 mAb; infusion reactions, PML (rare), hypogammaglobulinemia. Thailand reimbursement available for AChR/MuSK after IVIG failure + Pred+AZA failure post-thymectomy
5th — Refractory	Cyclophosphamide	0.5-1 g/m² IV monthly × 6	6-12 mo	Myelosuppression, hemorrhagic cystitis (mesna), infertility, malignancy risk

Rituximab Evidence in MG

📊 Key Rituximab Trials

AChR-Ab+ gMG (Neurology 2022;98:e376): Phase 2, 52 pts; steroid-sparing 60% vs 56% (p=0.03), but no significant secondary endpoints → benefit uncertain
MuSK-MG (Neurology 2017;89:1-9): 24 vs 31 pts; MGSTI ≥ level 2: 58% vs 16% (p=0.002); prednisone use 29% vs 74% (p=0.001) → strong evidence for MuSK
New-onset non-MuSK (JAMA Neurol 2022;79:1105): Low-dose single 500 mg IV; MDM 71% vs 29% at 16 wk; HR 0.09 for rescue (p=0.005)
Summary: Early for MuSK-MG; uncertain for refractory AChR-MG; low-dose 500 mg option for new-onset

Targeted Therapies (Complement & FcRn Inhibitors)

Agent	Target / MOA	Pivotal Trial	Route / Schedule	Key Notes
Eculizumab	Anti-C5 → blocks MAC formation	REGAIN 2017	IV 900 mg/wk × 4 → 1200 mg q2wk	AChR-Ab+ refractory gMG; ⚠️ meningococcal vaccination required ≥2 wk before; costly
Ravulizumab	Anti-C5 (long-acting eculizumab)	CHAMPION-MG 2022	IV q8wk	Non-inferior; more convenient dosing
Zilucoplan	Anti-C5 peptide inhibitor	RAISE 2023	SQ daily self-injection	AChR-Ab+ gMG; meningococcal vaccination required
Efgartigimod alfa (Vyvgart)	Anti-FcRn → ↓ IgG recycling → ↓ pathogenic Ab levels	ADAPT 2021	IV 10 mg/kg weekly × 4 per cycle	AChR-Ab+ gMG; reduces total IgG; no meningococcal vaccine needed; repeat cycles PRN
Rozanolixizumab	Anti-FcRn mAb	MycarinG 2023	SQ weekly	AChR-Ab+ or MuSK-Ab+; FDA approved 2023

Thymectomy Decision Flowchart

🔑 Thymectomy Indications:
• Thymoma detected → Resect if surgically feasible (regardless of MG status)
• No thymoma + AChR-Ab/seronegative + age 18-50:
→ Generalized MG → Thymectomy when disease is controlled (stabilized)
→ Disabling ocular MG → Consider thymectomy
• Age >50 / MuSK-MG / Non-disabling OMG → No thymectomy
• MGTX Trial (NEJM 2016): Thymectomy + prednisone vs prednisone alone in non-thymomatous AChR+ gMG → lower QMG, lower pred requirement, less need for azathioprine over 3 yr

Myasthenic Crisis

🔑 Crisis Management Protocol:
Definition: MGFA Class V — respiratory failure requiring intubation/NIV
Intubation criteria: FVC <15 mL/kg or NIF <−25 cmH₂O (the "20-30-40 rule": SBC <20, FVC <1L/20 mL/kg, NIF <−20 to −30)
RSI: Avoid succinylcholine (unpredictable response in MG); use rocuronium (reduced dose) + sugammadex for reversal
Acute treatment: PLEX (faster onset, 3-5 days) OR IVIG 2 g/kg over 5 d → choose PLEX for MuSK/severe crisis
Temporarily HOLD pyridostigmine (↓ secretions, simplify respiratory management)
Identify trigger: Infection (#1 cause), medication change, surgery, emotional stress, pregnancy
Distinguish from cholinergic crisis: SLUDGE signs, miosis, excessive AChEI use

Drugs to Avoid / Use with Caution in MG

⚠️ Medications That Worsen MG

Antibiotics: Aminoglycosides (gentamicin, tobramycin), fluoroquinolones (FDA black box warning), macrolides (erythromycin, azithromycin), telithromycin (withdrawn)
Cardiovascular: Beta-blockers (propranolol, atenolol), calcium channel blockers (verapamil), procainamide, quinine/quinidine
Other: Magnesium IV (⚠️ dangerous — blocks NMJ), botulinum toxin, D-penicillamine (can induce MG), checkpoint inhibitors (may exacerbate/induce de novo MG), iodinated contrast (use with caution), statins (rare), chloroquine/HCQ
Corticosteroids: Can cause transient worsening first 2 weeks — start low dose if outpatient or monitor inpatient if high dose
Vaccines: Live-attenuated vaccines CONTRAINDICATED with immunosuppression

MG in Pregnancy

🔑 Pregnancy Management:
• Symptomatic: Oral pyridostigmine is first-line; avoid IV AChEI (risk of uterine contractions)
• IS of choice: Prednisone (does not cross placenta significantly); azathioprine and cyclosporine are relatively safe
• CONTRAINDICATED in pregnancy: MMF (Category X), methotrexate, cyclophosphamide
• Delivery: Vaginal delivery preferred; epidural safe; avoid magnesium sulfate for eclampsia (use barbiturates or phenytoin instead)
• Neonatal MG: Transient neonatal MG in 10-20% due to transplacental IgG antibodies; self-limited (weeks)

MGFA Outcome Definitions

Term	Definition
Minimal Manifestation Status (MMS)	No symptoms or functional limitations; some weakness on exam permitted
Remission	No symptoms or signs of MG (mild eyelid closure weakness accepted)
Impending Crisis	Rapid worsening suggesting crisis within days to weeks
Refractory MG	Post-intervention status unchanged or worsened after steroids + ≥2 IS agents used at adequate dose/duration

Perioperative Steroid Supplementation in MG

Surgery Type	No HPA Suppression	HPA Suppressed
Minor (dental, local)	Continue usual dose	Continue usual dose
Moderate (joint replacement, abdominal)	Hydrocortisone 25-50 mg IV preop	HC 50 mg IV preop → 25 mg q8h × 24-48h
Major (cardiac, thymectomy)	HC 50 mg IV preop	HC 100 mg IV preop → 50 mg q8h × 48-72h

❓ Board-Style Question — MG

A 28-year-old woman presents with 3 months of fluctuating diplopia and ptosis, now with nasal speech and difficulty swallowing. AChR-Ab is negative. MuSK-Ab is positive. CT chest shows no thymoma. She fails to improve with pyridostigmine 360 mg/day and develops worsening bulbar symptoms on prednisolone. Which is the most appropriate next step?

Answer: Rituximab

This patient has MuSK-Ab+ MG with bulbar-predominant features and poor response to AChEI (characteristic of MuSK-MG). Key management principles: (1) MuSK-MG has poor AChEI response — use lower doses; (2) PLEX is preferred over IVIG for acute exacerbations; (3) Rituximab has strong evidence in MuSK-MG and should be considered early when initial IS fails (Neurology 2017;89:1-9: MGSTI ≥2 in 58% vs 16%); (4) Thymectomy is NOT indicated (no thymoma association with MuSK-MG). Complement inhibitors (eculizumab) target C5/MAC — not effective in MuSK-MG (IgG4 is non-complement-fixing). FcRn inhibitors (rozanolixizumab) are an option as they reduce all IgG subclasses.

▼5.2 Guillain-Barré Syndrome (GBS) & CIDP

Overview & Epidemiology

GBS is the most common cause of acute flaccid paralysis worldwide. Annual incidence: 1-2 per 100,000 person-years; M:F ~1.5:1; peak age 50-70 years. It is an acute polyradiculoneuropathy with variable severity from mild weakness to complete tetraplegia with respiratory failure.

Diagnostic Criteria (EAN/PNS 2023 Guideline)

📋 Features Required for Diagnosis (Motor-Sensory or Motor GBS)

Progressive weakness of arms and legs
Tendon reflexes absent or decreased in affected limbs
Progressive worsening for no more than 4 weeks (helps separate from CIDP)

Supporting Features	Features Making GBS Less Likely
Relative symmetry of weakness	Marked persistent asymmetry
Relatively mild/absent sensory symptoms with weakness	Severe respiratory dysfunction at onset with mild limb weakness
Cranial nerve involvement (bilateral facial palsy)	Predominant sensory signs at onset
Autonomic dysfunction	Fever at onset / hyperreflexia
Respiratory insufficiency	Sensory level / extensor plantar
Pain (muscular/radicular in back or limb)	Bladder/bowel dysfunction (does not exclude but less likely)
Recent history of infection (<6 wk)	CSF >50 cells/µL or PMN cells
CSF: elevated protein, normal cell count (<5 cells/µL)	No further worsening after 24h / slow worsening 2-4 wk with mild weakness
EDx: nerve conduction studies consistent with polyneuropathy	Continued worsening >4 wk or ≥3 TRFs (consider A-CIDP)

Antecedent Events & Triggers

🔑 Common Triggers (PICO 1):
• Infections (~2/3 of cases): Campylobacter jejuni (most strongly associated → AMAN/AMSAN, worse prognosis), CMV, EBV, Hepatitis E, Mycoplasma pneumoniae, Zika virus, influenza
• Vaccinations: Very small increased risk after influenza, herpes zoster, SARS-CoV-2 adenovirus-vector vaccines (4-7 excess per million); benefits far outweigh risk
• Other: Surgery, immune checkpoint inhibitors, anti-TNF agents; pregnancy/transplant (within 6 months)

GBS Classification & Subtypes

Subtype	% of GBS	Pathophysiology	EDx Pattern	Antibodies	Key Features
AIDP	80-85% (Europe/NA)	Demyelination of Schwann cell myelin	Prolonged DL, slowed CV, conduction block, temporal dispersion	Variable; anti-GM1 less common	Classic GBS; ascending weakness; albuminocytologic dissociation
AMAN	5-10% (more in Asia)	Axonal — antibodies target axolemma at nodes of Ranvier	Low CMAP amplitudes, normal CV/DL; preserved SNAPs	Anti-GM1, anti-GD1a	Pure motor; C. jejuni association; can have rapid recovery or severe course
AMSAN	Rare	Axonal — motor + sensory	Low CMAP + SNAP amplitudes	Anti-GM1, anti-GD1a	Severe; slower recovery
MFS	5-25%	Cranial nerve/DRG involvement	May be normal; sensory conduction abnormalities	Anti-GQ1b (88-100%)	Triad: ophthalmoplegia + ataxia + areflexia; may overlap with GBS
BBE	Very rare	CNS + PNS	Variable	Anti-GQ1b	MFS + pyramidal signs + altered consciousness; may show WM changes on MRI

GBS Variants (Regional Forms)

🔑 Regional GBS Variants: Pharyngeal-cervical-brachial (PCB), bilateral facial weakness with limb paresthesias, paraparetic variant (starts in legs → may evolve to tetraparesis), pure sensory variant (rare — numbness/tingling, areflexia, demyelinating NCS, no weakness, GBS-like time course)

Investigations

🔬 Diagnostic Workup

CSF (PICO 2): Albuminocytologic dissociation — ↑ protein (median 0.98 g/L at >7 days), normal WBC (<5 cells/µL in 80%); normal protein common in first week; CSF >50 cells/µL → consider HIV, Lyme, CMV, leptomeningeal process
Electrodiagnosis (PICO 4): May be normal in first week. Supportive findings: absent H-reflexes (95-100% sensitivity for AIDP), F-wave absence/prolongation, conduction block, temporal dispersion, prolonged distal latency. Sural sparing pattern (abnormal median/ulnar SNAP with normal sural SNAP) — characteristic of GBS
Anti-ganglioside antibodies (PICO 3): Anti-GQ1b for suspected MFS (highly specific); routine ganglioside testing NOT recommended for typical motor-sensory GBS (low sensitivity, delays results)
Nerve MRI/US (PICO 5): Not routine; consider for atypical presentations. MRI: nerve root enhancement. US: increased cross-sectional area

Assessment & Monitoring — Predicting ICU Admission

📊 mEGRIS (Modified Erasmus GBS Respiratory Insufficiency Score)

Predicts risk of mechanical ventilation. Based on: (1) days from onset to admission, (2) presence of bulbar palsy, (3) weakness of neck flexion/hip flexion, (4) MRC sum score. Score range 0-32; mEGRIS ≥25 (~>70% predicted) → HIGH RISK → ICU monitoring.

Clinical indicators for ventilation: FVC <20 mL/kg, MIP <40 cmH₂O, MEP <30 cmH₂O, or >30% FVC decline from baseline. SBC <20 → bedside indicator for ICU. Check FVC q3-6 hourly.

Predictors of Respiratory Failure	Evidence Level
Shorter time from symptom onset to admission (<7 days)	High certainty
Bulbar involvement	High certainty
MRC sum score <20/60	High certainty
Neck muscle weakness / inability to lift elbows or stand	Moderate certainty
Greater GBS disability score (≥4)	Moderate certainty
Lower vital capacity / inability to cough	Moderate certainty
Dysautonomia / AMAN subtype	Moderate certainty
Abnormal liver enzymes, CMV/HSV infection	Lower certainty (additional risk)

Treatment (EAN/PNS 2023 Recommendations)

💊 Immune Treatment of GBS

IVIG (PICO 9 — Strong recommendation ++): 0.4 g/kg/day × 5 days; start ASAP in patients unable to walk unaided (GBS-DS ≥3) within first 2 weeks from weakness onset. One standard course only — do NOT repeat IVIG (SID-GBS trial: 2nd IVIG course showed no benefit, increased thromboembolic events)
PLEX (PICO 8 — Strong recommendation ++): 4-5 exchanges over 1-2 weeks (total 12-15L); equally effective as IVIG; start within 4 weeks of onset. PLEX weakly recommended (2 exchanges) for ambulatory patients (GBS-DS 2) who are rapidly deteriorating
IVIg vs PLEX: No significant difference in efficacy (moderate certainty); IVIG more widely available, less discontinued; PLEX favored in young children (less vascular access issues), severe autonomic instability relative contraindication for PLEX
PE followed immediately by IVIG → NOT recommended (strong recommendation against)
Corticosteroids → NOT recommended: Oral steroids strongly recommended against; IV methylprednisolone weakly recommended against (moderate evidence of no benefit, possible harm from oral steroids)
Eculizumab → Weakly recommended against (2 small Phase 2 trials, no significant benefit; JET-GBS trial in 33 pts: no difference in primary endpoints)
Very mildly affected (GBS-DS 1 or stable GBS-DS 1-2): IVIg/PLEX NOT advised — disease may stabilize spontaneously

GBS Treatment Flowchart

🔑 Treatment Decision by Timing & Severity:
<2 wk from onset:
→ Severe (unable to walk) → Start IVIG 0.4 g/kg × 5d or PLEX 4-5 exchanges
→ Mild but rapidly deteriorating / swallowing difficulties / autonomic → Consider IVIG or PLEX
→ Mild and stable → No IVIg/PLEX; monitor closely
2-4 wk from onset:
→ Still unable to walk → Start 4-5 × PLEX (12-15L) over 5-14d, or IVIg 0.4 g/kg × 5d
→ Mild and stable → No treatment advised
>4 wk and still deteriorating:
→ Consider A-CIDP (PICO 6); test nodal-paranodal antibodies (NF155, Caspr1, CNTN1); treat as CIDP

A-CIDP (Acute-Onset CIDP) — PICO 6

~5% of patients initially diagnosed with GBS later turn out to have A-CIDP. Suspect if: (1) ≥3 TRFs (treatment-related fluctuations); (2) progression >8 weeks from onset; (3) marked sensory abnormality; (4) no facial/bulbar/respiratory weakness; (5) nerve US/MRI showing widespread peripheral nerve enlargement; (6) early significant reduction in MNCV.

Pain & Fatigue in GBS

💊 Symptom Management

Pain (PICO 12): Occurs in majority — back, interscapular, radicular, dysesthesias. First-line: gabapentin (5 mg/kg or 300 mg TID) or carbamazepine. TCAs or pregabalin as alternatives. High-dose corticosteroids NOT recommended for pain
Fatigue (PICO 13): 38-86% prevalence, can persist years. Amantadine weakly recommended against. No proven pharmacological treatment; graded exercise programme may help

Prognosis (PICO 14)

📊 Prognostic Factors — mEGOS (Modified Erasmus GBS Outcome Score)

Predictors of poor outcome (high certainty): Older age, preceding diarrhea/gastroenteritis, higher GBS-DS at admission, lower MRC sum score, decreased CMAP amplitude (<20% of lower limit normal averaged over ≥3 motor nerves)
Probable predictors (moderate certainty): Preceding C. jejuni, severe arm weakness, higher EGOS/mEGOS, AMAN/AMSAN subtype
Mortality: 3-7% (respiratory failure, cardiac arrest from dysautonomia, PE, sepsis)
Recovery: ~80% walk independently at 6 months; 60% full recovery at 1 year; ~20% have significant residual disability

GBS Differential Diagnosis

Level	Differential Diagnoses
CNS	Transverse myelitis, brainstem stroke, NMO, cord compression, anti-MOG
Anterior horn cell	Poliomyelitis, West Nile virus, Japanese encephalitis
Nerve root	CMV/HIV polyradiculitis, leptomeningeal malignancy, Lyme
Peripheral nerve	CIDP/A-CIDP, vasculitis, toxins (lead, arsenic, organophosphate), vitamin deficiency (B1, B12), ICU-acquired weakness
NMJ	MG, LEMS, botulism, tick paralysis
Muscle	Inflammatory myopathy, hypokalemic periodic paralysis, rhabdomyolysis, critical illness myopathy

❓ Board-Style Question — GBS

A 45-year-old man presents with 5 days of ascending weakness after a diarrheal illness 2 weeks ago. He cannot walk unaided. FVC is 2.0L (predicted 4.0L). Nerve conduction shows low CMAP amplitudes with preserved conduction velocities and normal SNAPs. Anti-GM1 antibodies are positive. Which GBS subtype does this represent, and what is the preferred treatment?

Answer: AMAN (Acute Motor Axonal Neuropathy)

The clue is post-Campylobacter diarrheal illness + pure motor involvement + low CMAPs with preserved CV and normal SNAPs (axonal pattern, motor only) + anti-GM1 positive. Treatment: Start IVIG 0.4 g/kg/d × 5 days OR PLEX 4-5 exchanges immediately (GBS-DS ≥3, unable to walk). Monitor FVC closely — already at 50% predicted, at risk for ventilation. Do NOT repeat IVIG if no improvement (SID-GBS trial). Consider A-CIDP if progression >4 weeks. Prognosis: AMAN can have either rapid recovery (reversible conduction failure at nodes) or prolonged course (axonal degeneration). C. jejuni-associated AMAN tends toward worse outcome.

▼5.3 Motor Neuron Diseases

Overview of Motor Neuron Diseases

Motor neuron diseases (MND) encompass a spectrum of progressive disorders affecting upper motor neurons (UMN), lower motor neurons (LMN), or both. ALS is the most common and devastating. Other important MNDs include SMA, Kennedy disease (SBMA), Hirayama disease, and post-polio syndrome.

Amyotrophic Lateral Sclerosis (ALS)

Epidemiology & Genetics

Progressive degeneration of motor neurons in motor cortex, brainstem, and spinal cord. Incidence: 1-2/100,000/year in Europe/USA (0.7/100,000 in South Asia). 90% sporadic (M:F 2:1, onset mid-to-late 50s); 10% familial (usually AD).

🧬 Key ALS Genes

C9orf72 (hexanucleotide repeat expansion) — most common fALS in European populations (~40% fALS); also FTD-ALS
SOD1 (superoxide dismutase 1) — ~20% fALS; tofersen target
TARDBP (TDP-43) — RNA metabolism; TDP-43 inclusions are pathological hallmark of sporadic ALS
FUS (Fused in Sarcoma) — RNA processing

Pathogenic pathways: (1) Impaired autophagy/proteostasis (TBK1, OPTN, SQSTM1, UBQLN2, C9orf72, VCP); (2) Disturbed RNA metabolism (TDP-43, FUS, hnRNPA1); (3) Cytoskeletal/axonal transport defects (TUBA4A, KIF5A, PFN1); (4) Neuroinflammation (microglia/astrocyte activation); (5) Mitochondrial dysfunction; (6) Excitotoxicity; (7) Impaired nucleoplasmic transport; (8) Oligodendrocyte dysfunction; (9) Impaired DNA repair

Clinical Features — UMN + LMN Signs

LMN Signs	UMN Signs	Cognitive/Behavioral
Muscle weakness (distal > proximal)	Hyperreflexia	FTD in up to 50% (bvFTD)
Muscle wasting/atrophy	Spasticity	Primary progressive aphasia (naPPA)
Split Hand Phenomenon	Pathological reflexes (Babinski, Hoffman)	~10% meet FTD criteria at diagnosis
Fasciculations (widespread)	Pseudobulbar affect (emotional lability)	Executive dysfunction in 30-50%
Dysarthria (mixed flaccid-spastic)	Clonus, spastic catch
Dysphagia	Slowed movements

🔑 Split Hand Phenomenon: Preferential wasting of thenar (APB) and first dorsal interosseous (FDI) compared to hypothenar (ADM) muscles. Four proposed hypotheses: (A) Cortical hyper-excitability, (B) Abnormal spinal circuitry, (C) Axonal membrane channel dysfunction, (D) End plate physiological features. This pattern is relatively specific for ALS vs other causes of hand wasting (e.g., ulnar neuropathy would spare APB).

Clinical Spectrum of ALS

Phenotype	Motor Neuron	Presentation	Prognosis
Classic limb-onset (spinal)	UMN + LMN	Cervical: hand weakness → spreads to bulbar/lumbar; Lumbar: foot drop → ascending. Split hand sign	Median survival 3-5 yr
Bulbar onset	UMN + LMN	Dysarthria → dysphagia → limb involvement; unexplained weight loss	Worse prognosis (2-3 yr)
Pseudobulbar palsy	UMN predominant	Prominent bulbar UMN features; slowly spreads to limbs; F > M	Longer survival than classic bulbar
Progressive bulbar palsy	LMN predominant	Prominent bulbar LMN features → limb spread	Median survival may be longer than classic bulbar
Flail arm (Vulpian-Bernhardt)	LMN predominant	Proximal arm weakness/wasting, bilateral; "man-in-barrel"	Relatively better (~5 yr)
Flail leg	LMN predominant	Distal leg weakness → ascending	Better than classic
PLS (Primary Lateral Sclerosis)	UMN only	Progressive spasticity; may begin any region; exclude HSP	Normal or near-normal life expectancy; if LMN signs develop within 4.5 yr → reclassify as ALS
PMA (Progressive Muscular Atrophy)	LMN only	Progressive LMN weakness; male predominance	If UMN signs develop within 4.5 yr → reclassify as ALS; better prognosis than classic ALS

Diagnosis — Gold Coast Criteria (2019)

📋 Simplified ALS Diagnostic Criteria (replacing El Escorial)

The Gold Coast criteria require:

1. Progressive motor impairment documented by history or clinical exam
2. UMN + LMN signs in ≥1 body region, OR LMN signs in ≥2 body regions
3. Investigation results that exclude other disease processes

Body regions: bulbar, cervical, thoracic, lumbosacral. EMG evidence of LMN dysfunction can substitute for clinical LMN signs. These criteria are simpler and more sensitive than the revised El Escorial criteria while maintaining specificity.

Investigations

🔬 ALS Workup

EMG/NCS: Widespread active denervation (fibrillations, positive sharp waves, fasciculation potentials) + chronic neurogenic reinnervation (large MUAPs, reduced recruitment) in ≥2 body regions. Motor NCS: may show reduced CMAP amplitudes with relatively preserved conduction velocity. Sensory NCS: typically normal (important for excluding ALS mimics)
MRI brain/spine: Exclude structural mimics (cervical myelopathy, syringomyelia, MS). May show corticospinal tract T2 hyperintensity in motor cortex
Lab: CK (mildly elevated in ALS), CBC, CMP, TSH, B12, HIV, SPEP/UPEP, anti-GM1 (to exclude MMN), CK; consider paraneoplastic panel, heavy metals
Genetic testing: Growing consensus to offer to ALL ALS patients (not just familial) — particularly C9orf72, SOD1 (tofersen eligibility)

ALS Mimics to Exclude

🔑 Critical ALS Mimics:
• Cervical spondylotic myelopathy (CSM): UMN legs + LMN arms from compression — MRI confirms
• Multifocal Motor Neuropathy (MMN): Asymmetric LMN, conduction block on NCS, anti-GM1 Ab+, treatable with IVIG
• Kennedy disease (SBMA): Slow, LMN, gynecomastia, reduced SNAPs, CK elevated, CAG repeat in AR gene
• Late-onset SMA (Type III/IV): Symmetric proximal LMN, no UMN signs, SMN1 deletion
• Hirayama disease: Young male, unilateral hand wasting, self-limited, flexion MRI positive
• IBM: Quadriceps + finger flexor weakness, CK elevated, may have anti-cN1A

Disease-Modifying Treatment (EAN 2024)

Agent	MOA	Recommendation	Evidence
Riluzole	Anti-glutamate (reduces excitotoxicity)	Strong ++ — offer lifelong at diagnosis	50 mg BID; extends survival ~2-3 months; only proven life-extending therapy for all ALS
Tofersen	Antisense oligonucleotide targeting SOD1 mRNA (intrathecal)	Strong ++ for SOD1-ALS first-line	VALOR trial (NEJM 2022); ↓neurofilament light chain; FDA-approved for SOD1-ALS
Edaravone	Free radical scavenger	Weak −− (not recommended outside clinical trial)	Conflicting RCT data; EAN does not recommend IV or oral outside clinical trial; interim recommendation pending Phase III oral edaravone
AMX0035 (sodium phenylbutyrate-taurursodiol)	Targets mitochondrial/ER stress	Weak − (not recommended outside trial)	CENTAUR trial (NEJM 2020); FDA accelerated approval; EAN interim recommendation pending Phase III
Cell-based therapies	Various	Strong −− (not recommended outside trial)	No Phase III data

Multidisciplinary Care & Symptom Management

💊 Comprehensive ALS Symptom Management (EAN 2024)

Respiratory: NIV for ALL patients with respiratory insufficiency symptoms/signs (strong ++); do NOT use diaphragm pacing (strong −−); consider invasive ventilation (discuss advance care planning); FVC monitoring
Nutrition: Early gastrostomy discussion; if respiratory insufficiency, establish NIV first, then gastrostomy (EAN recommendation); nasogastric tube as bridge
Sialorrhea: Anticholinergics first-line (amitriptyline, atropine drops, glycopyrrolate, hyoscine patches); botulinum toxin for refractory; radiotherapy as last resort
Spasticity: Baclofen, tizanidine, gabapentin, cannabinoids; physical therapy; focal → botulinum toxin
Muscle cramps: Quinine sulfate 100-200 mg/d (monitor cardiac), mexiletine, carbamazepine, gabapentin
Pseudobulbar affect: Dextromethorphan/quinidine (DMQ) — may also improve bulbar function; SSRIs/TCAs alternatives
Pain: Multifactorial — identify cause (cramps, spasticity, joint, neuropathic); standard analgesic ladder; gabapentinoids for neuropathic
Communication: Early speech therapy referral; AAC devices when needed; eye-gaze technology for advanced disease
DVT prevention: Non-pharmacological (elevation, compression, physiotherapy) — insufficient evidence for anticoagulants
Psychological: Screen for anxiety/depression; psychological support at every visit; advance care planning at diagnosis

Spinal Muscular Atrophy (SMA)

🧬 SMA — Autosomal Recessive, SMN1 Gene (5q)

Degeneration of motor neurons in spinal cord and brainstem due to survival motor neuron (SMN) protein deficiency. Prevalence 1/6,000-10,000. SMN2 copy number inversely correlates with severity.

Type	SMN2 Copies	Onset	Max Motor Milestone	Life Expectancy
Type 0	1	In utero (fetal)	None	Perinatal death
Type I (Werdnig-Hoffmann)	2	<6 months	Never sit	90% die by 24 months (without treatment)
Type II (Dubowitz)	3	6-18 months	Sit but never walk	30-50 years
Type III (Kugelberg-Welander)	3-5	>18 months	Walk unaided (may lose later)	Near-normal
Type IV	3-5	Adulthood	Walk — mild to moderate weakness	Normal

💊 SMA Gene Therapies

Nusinersen (Spinraza): Antisense oligonucleotide — modifies SMN2 splicing → ↑ functional SMN protein; intrathecal injection
Onasemnogene abeparvovec (Zolgensma): AAV9 gene replacement therapy — delivers functional SMN1 gene; single IV infusion; approved for <2 years
Risdiplam (Evrysdi): Oral SMN2 splicing modifier; daily oral; approved for all ages

Kennedy Disease (SBMA — Spinal and Bulbar Muscular Atrophy)

Feature	Details
Genetics	X-linked recessive; CAG trinucleotide repeat expansion (>38 repeats) in androgen receptor (AR) gene
Pathophysiology	Toxic gain-of-function: abnormal polyglutamine stretch → misfolding → intranuclear aggregation; androgen-dependent toxicity → motor neuron + DRG damage
Onset	30s-50s; males only (females are carriers)
Motor features	Slowly progressive proximal > distal weakness (legs > arms); bulbar weakness (dysphagia, dysarthria); widespread fasciculations (tongue, perioral, limb); postural hand tremor
Non-motor features	Gynecomastia, testicular atrophy, infertility; sensory neuronopathy (DRG involvement); mild to moderate elevated CK
Investigations	NCS: reduced or absent SNAPs (distinguishes from ALS!); EMG: neurogenic; CK elevated (up to 4,000+); genetic testing confirms
Treatment	Supportive; no disease-modifying therapy proven; androgen deprivation under investigation

Hirayama Disease (Monomelic Amyotrophy)

🔑 Hirayama Disease — Key Features:
• Epidemiology: Juvenile distal segmental muscular atrophy; >80% male; 2nd-3rd decade; Asia-predominant
• Pattern: Pure LMN, C7-C8-T1 distribution → distal upper limb (hand muscles); unilateral in 90% (10% bilateral)
• Natural history: Self-limited — stops progressing after 1-5 years (unlike ALS!)
• MRI: Neutral position: T2 signal in anterior cord; Flexion MRI: posterior dural sac crescent enhancement (high T1/T2, Gd-enhancing), epidural flow voids — pathognomonic
• Treatment: Cervical collar to limit flexion; supportive

AHC Diseases — Myopathy Mimics Comparison

Feature	Kennedy Disease	SMA Type III	SMA Type IV
Genetics	CAG expansion in AR gene	SMN1 mutation (AR)
Inheritance	X-linked recessive	Autosomal recessive
Onset	Adulthood (30s-50s)	Childhood-adolescent	Adulthood
Weakness pattern	Proximal limb-girdle (legs)	Proximal (legs)	Proximal (mild-moderate)
Bulbar	Common (dysarthria, dysphagia)	Rarely affected
Fasciculations	Present (tongue, perioral, limb)	May be present
Distinguishing	Gynecomastia, reduced SNAPs, CK elevation !!	Muscle cramps, tremors, CK mildly elevated

Post-Polio Syndrome (PPMA)

Onset >10 years after acute poliomyelitis. Progressive asymmetric weakness/atrophy/cramps/fasciculations from late degeneration of enlarged motor units. Diagnosis of exclusion. Management is supportive — no disease-modifying therapy. Avoid overexertion.

❓ Board-Style Question — MND

A 59-year-old woman presents with 18 months of progressive right hand weakness followed by bilateral hand wasting, dysphagia, and now bilateral proximal lower limb weakness. Exam shows generalized atrophy with fasciculations, neck flexor/extensor weakness (drop head), DTR: brisk jaw jerk, biceps 3+/triceps 2+/BCR 1+ (UE), knee/ankle 2+/2+. Babinski absent both sides. NCS shows prolonged distal latencies, decreased CMAP amplitudes across multiple nerves. EMG demonstrates active denervation and reinnervation in bulbar, cervical, and lumbar regions. What is the diagnosis?

Answer: ALS (Amyotrophic Lateral Sclerosis)

This case shows combined UMN signs (brisk jaw jerk, hyperreflexia) and LMN signs (atrophy, fasciculations, active denervation on EMG) in ≥3 body regions (bulbar, cervical, lumbar) with progressive course — meeting Gold Coast criteria. The drop head is from combined neck flexor/extensor weakness. NCS pattern shows axonal involvement (low CMAPs) with some motor predominance. Key differentials to exclude: cervical myelopathy (MRI needed), Kennedy disease (no gynecomastia mentioned, but check SNAPs — if reduced → SBMA; genetic testing for CAG expansion), MMN (conduction block absent here, not fitting pattern). The diffuse involvement across 3 regions with mixed UMN/LMN makes ALS the most likely diagnosis. Start riluzole, refer MDT, screen FVC, and consider genetic testing.

▼5.4 Approach to Myopathies

Clinical Approach to Myopathy

Myopathies present with LMN-type weakness (no fasciculations, no sensory loss). Key clinical features: proximal weakness (except IBM/distal myopathies), normal or reduced DTRs only in severely weak muscles, potential muscle pain/cramps, possible cardiac/respiratory involvement.

📋 Approach to Weakness — Key Distinguishing Features

Feature	Motor Neuron	Peripheral Nerve	NMJ	Muscle
Weakness pattern	Variable; UMN+LMN	Distal > proximal	Fatigable; ocular/bulbar	Proximal > distal
DTRs	↑ (UMN) or ↓ (LMN)	↓↓	Normal	Normal or ↓ (if weak)
Sensory	Absent (except Kennedy)	Present	Absent	Absent
Fasciculations	Yes	Possible (chronic)	No	No
CK	Mild ↑	Normal	Normal	↑↑ (necrosis)
EMG	Neurogenic MUAPs	Neurogenic	Decrement/Jitter	Myopathic (small, short, polyphasic)

Distribution Patterns in Myopathies

Pattern	Differential Diagnoses
Limb-girdle (proximal)	Most inflammatory myopathies, LGMD, metabolic myopathies, endocrine myopathies
Distal	Distal myopathies (Welander, Miyoshi, Nonaka, Laing), myotonic dystrophy
Humeroperoneal	Emery-Dreifuss, FSHD
Facial weakness	FSHD, myotonic dystrophy, mitochondrial
Ptosis ± ophthalmoplegia	With ophthalmoplegia: CPEO (mitochondrial), OPMD, oculopharyngodistal; Without: myotonic dystrophy, centronuclear, nemaline rod, desmin myopathy
Scapular winging	FSHD, LGMD2A, acid maltase deficiency
Quadriceps + finger flexors (asymmetric)	IBM — highly characteristic pattern
Neck extensor weakness (drop head)	Acid maltase deficiency, isolated neck extensor myopathy, MG, ALS, myotonic dystrophy, DM/PM, IBM, nemaline rod
Calf pseudohypertrophy	Duchenne/Becker, LGMD

Cardiac Associations in Myopathies

🔑 Myopathies with Cardiac Involvement:
• Arrhythmias/Conduction defects: Kearns-Sayre syndrome, Andersen-Tawil (periodic paralysis), myotonic dystrophy, Emery-Dreifuss, LGMD 1B/2C-2F/2G, PM
• Cardiomyopathy/CHF: Duchenne/Becker (dilated CMP), Emery-Dreifuss, myotonic dystrophy, LGMD 1B/2C-2F/2G, nemaline, acid maltase, carnitine deficiency, inflammatory
• Respiratory insufficiency: Duchenne/Becker, Emery-Dreifuss, limb-girdle, myotonic dystrophy, acid maltase deficiency, nemaline/centronuclear, inflammatory

Classification: Hereditary vs Acquired

Feature	Hereditary Myopathies	Acquired Myopathies
Onset	Chronic, often since childhood	Subacute or chronic onset
Family history	Often positive	Negative
Distribution	Specific muscle groups	Proximal (except IBM, thyroid myopathy)
Associated features	Myotonia, cramps, deformities, contractures	Associated systemic diseases
Mimics	LGMDs/NAM, metabolic myopathies/inflammatory myopathies can overlap

Hereditary Myopathies — Overview

Category	Key Features
Muscular Dystrophies	Dystrophic changes on biopsy, elevated CK, limb-girdle/specific muscle groups, cardiac associations
Congenital Myopathies	Early/infantile onset, variable CK, myopathic facies, deformities, associated brain abnormalities (centronuclear, nemaline rod, central core)
Myopathies with Myotonia	Myotonic dystrophy type 1 (DM1: CTG repeat, DMPK) & type 2 (DM2: CCTG repeat, ZNF9); channelopathies
Mitochondrial Myopathies	Myopathy + short stature + retinitis pigmentosa + stroke-like episodes + seizures + cardiac abnormalities; ragged red fibers; CPEO/Kearns-Sayre
Metabolic Myopathies	Episodic weakness/rhabdomyolysis; glycogen storage (Pompe/acid maltase, McArdle); lipid storage (carnitine, CPT II); periodic paralysis

▼5.5 Inflammatory Myopathies (Idiopathic Inflammatory Myopathies — IIM)

Classification (Modern 2018 Framework — Greenberg, Nat Rev Rheum)

The IIM classification has evolved from the old PM/DM dichotomy. Modern classification recognizes: Dermatomyositis (DM), Antisynthetase Syndrome (ASS), Immune-Mediated Necrotizing Myopathy (IMNM), Inclusion Body Myositis (IBM), Overlap Myositis, and Non-specific Myositis (formerly "PM" — now a diagnosis of exclusion).

Myositis-Specific Antibodies (MSAs) — Comprehensive Table

Antibody	Antigen	Associated Phenotype	ILD Frequency	Key Associations
Antisynthetase Syndrome (ASS)
Anti-Jo-1	Histidyl-tRNA synthetase	ASS (75% of all ASS)	70%	Most common MSA in PM; mechanic's hands, arthritis, Raynaud's, fever
Anti-PL-7, PL-12, EJ, OJ, KS, Ha, Zo	Other aminoacyl-tRNA synthetases	ASS variants	Variable	Similar phenotype; non-Jo-1 ASS may have more severe ILD, less myositis
Dermatomyositis (DM)
Anti-Mi2	Nucleosome remodeling complex	Classic DM skin lesions	Low	Good prognosis; typical skin rash; DM 9%, PM 1/4
Anti-MDA5	Melanoma differentiation protein 5	Amyopathic DM + rapidly progressive ILD	Very high (>90%)	⚠️ May have minimal myositis; joint-skin-lung syndrome; cutaneous ulcers; high mortality from ILD
Anti-TIF1γ (p155/140)	Transcription intermediary factor	DM + malignancy	Low	⚠️ Cancer screening mandatory (especially >40 yr); DM 10-30%
Anti-NXP2 (MJ)	Nuclear matrix protein 2	DM + malignancy	Low	Calcinosis; cancer association (especially adults); children → calcinosis
Anti-SAE	SUMO-activating enzyme	DM	Low-moderate	Skin-predominant initially → may progress to myopathy; DM 5-10%
Immune-Mediated Necrotizing Myopathy (IMNM)
Anti-SRP	Signal recognition particle	Severe necrotizing myopathy	15%	Acute/subacute severe proximal weakness; very high CK; resistant to treatment
Anti-HMGCR	HMG-CoA reductase	Statin-associated IMNM	Low	May occur with or without statin exposure; self-perpetuating autoimmune process after statin trigger; CK very high
Inclusion Body Myositis (IBM)
Anti-cN1A (Mup44)	Cytosolic 5'-nucleotidase 1A	IBM	—	Present in 33-51% of IBM; not entirely specific; marker, not driver

Myositis-Associated Antibodies (MAAs)

Found in overlap syndromes: Anti-PM/Scl (scleroderma-myositis overlap), Anti-Ro-52 (IIM 25%, ILD association), Anti-Ku (gene transcription), Anti-U1RNP (MCTD overlap). These help identify overlap phenotypes but are not disease-specific.

Dermatomyositis (DM)

🔬 DM — Skin + Muscle + Systemic

Skin findings: Heliotrope rash (violaceous periorbital edema), Gottron's papules (erythematous plaques over MCP/PIP/DIP), V-sign (chest), Shawl sign (upper back), mechanic's hands, nail fold capillary changes, calcinosis
Muscle: Symmetric proximal weakness; CK elevated 10-50× (may be normal in amyopathic DM)
Pathology: Perifascicular atrophy (pathognomonic); perivascular/perimysial inflammation (CD4+, B cells, complement deposition); capillary dropout
Cancer association: 15-25% risk, especially with anti-TIF1γ and anti-NXP2; screen CT chest/abd/pelvis ± PET-CT; colonoscopy; repeat screening at 3 years
ILD: Especially anti-MDA5 (rapidly progressive, high mortality) and anti-Jo-1/ASS

Inclusion Body Myositis (IBM)

🔑 IBM — The Great Myopathy Mimic:
• Epidemiology: Most common acquired myopathy in patients >50 years; M:F 3:1
• Unique pattern: Asymmetric weakness of quadriceps (knee extension) + finger flexors (FDP) → difficulty gripping, opening bottles, climbing stairs
• Also affected: Wrist flexion, elbow flexion, ankle dorsiflexion; dysphagia (up to 60%)
• CK: Normal to moderately elevated (usually <12× ULN)
• Pathology: Rimmed vacuoles; TDP-43+ inclusions; endomysial inflammation with CD8+ T cells invading non-necrotic fibers; mitochondrial changes (COX-negative fibers)
• MRI: Selective atrophy of rectus femoris (quadriceps) with relative preservation of other thigh muscles
• Antibody: Anti-cN1A (33-51%); not diagnostic alone
• Treatment: Refractory to immunosuppression (steroids, IVIG, methotrexate — no proven benefit); physiotherapy essential; bimagrumab (anti-activin receptor II) under investigation; avoid unnecessary immunosuppression

Immune-Mediated Necrotizing Myopathy (IMNM)

💊 IMNM — Anti-SRP and Anti-HMGCR

Clinical: Proximal-predominant weakness; CK markedly elevated (>10,000 common)
Pathology: Necrotic muscle fibers with minimal/absent endomysial inflammation (no invasion of non-necrotic fibers — distinguishes from PM); scattered macrophages; MHC-I upregulation
Anti-SRP IMNM: Acute/subacute, severe; cardiac involvement possible; may need aggressive IS (steroids + IVIG + rituximab)
Anti-HMGCR IMNM: Statin-associated (but can occur without statins); stopping statin alone insufficient — need immunotherapy; self-perpetuating autoimmune process
Treatment: High-dose steroids + IVIG (first-line for severe); steroid-sparing: azathioprine, MTX, MMF; refractory → rituximab; IVIG maintenance often needed

IIM Treatment Summary

💊 IIM Stepwise Treatment

1st line: Prednisolone 1 mg/kg/day × 4-8 wk → slow taper; start steroid-sparing agent EARLY (azathioprine 2-3 mg/kg/d or methotrexate 15-25 mg/wk)
ILD-predominant (anti-MDA5, ASS): MMF 2-3 g/day preferred; cyclosporine/tacrolimus for rapidly progressive ILD; IV cyclophosphamide for crisis/life-threatening ILD
Refractory muscle disease: IVIG 2 g/kg q1-3 mo (ProDERM 2021 — DM); rituximab (MAVI trial); IVIG for IMNM
Cancer screening (DM): CT chest/abdomen/pelvis ± PET-CT; colonoscopy; pelvic US (women); mammography; especially with anti-TIF1γ/anti-NXP2; repeat at 3 years
IBM: NO proven immunotherapy — avoid chronic steroids/IS; physiotherapy, swallowing therapy; consider IVIG trial if severe dysphagia

Drug-Induced & Toxic Myopathies

Category	Agents	Pathology	Key Features
Necrotizing myopathy	Statins (HMG-CoA reductase inhibitors), cyclosporine	Necrotic fibers, minimal inflammation	CK markedly elevated; may be self-limited (statin withdrawal) or immune-mediated (anti-HMGCR → persistent)
Steroid myopathy	Corticosteroids	Type 2B fiber atrophy; EMG often normal	Proximal weakness, Cushingoid; EMG helps differentiate from inflammatory myopathy; type 2B atrophy on biopsy
Amphiphilic drug myopathy	Chloroquine, HCQ, amiodarone	Autophagic vacuoles; neuromyopathy	Can cause combined myopathy + neuropathy; vacuolar changes on biopsy
Antimicrotubule myopathy	Colchicine, vincristine	Vacuolar myopathy; axonal neuropathy	Neuromyopathy; clinical myotonia possible (colchicine); mainly neuropathy with vincristine
Mitochondrial toxicity	Zidovudine (AZT), other antiretrovirals	Ragged red fibers; no significant inflammation	CK normal-mildly elevated; HIV-associated myositis if CK markedly elevated
Critical illness myopathy	ICU (corticosteroids + NMBAs)	Myosin thick filament loss	Generalized weakness post-ICU; differentiate from CIP (NCS: CMAP low, SNAPs preserved in CIM vs both low in CIP)
Rhabdomyolysis	Ethanol, heroin, cocaine, statins, cyclosporine	Acute necrosis	Acute: CK >10,000, myoglobinuria, AKI risk; treat: aggressive IV hydration

Endocrine Myopathies

Thyroid: Hypothyroid myopathy (proximal weakness, CK elevated, Hoffman syndrome — stiffness/pseudomyotonia); hyperthyroid myopathy (proximal wasting, normal CK). Parathyroid: Hyperparathyroidism → proximal muscle weakness + atrophy. Adrenal: Cushing's/steroid → type 2B fiber atrophy; Addison's → fatigue/weakness. Acromegaly: Proximal weakness.

Other Acquired Myopathies

Sarcoid myopathy (nodular or chronic), amyloid myopathy (macroglossia, pseudohypertrophy), checkpoint inhibitor-associated myositis (treat with IV steroids/IVIG/PLEX; may overlap with MG/myocarditis).

❓ Board-Style Question — Myopathy

A 67-year-old man presents with 2 years of progressive difficulty rising from chairs and gripping objects. Exam shows asymmetric weakness of knee extension (R 3/5, L 4/5) and finger flexion (R 3/5, L 4+/5) with relative preservation of shoulder abduction and hip flexion. CK is 580 U/L. EMG shows mixed myopathic and neurogenic features. He was previously treated with prednisone 60 mg/day for 6 months without improvement. What is the most likely diagnosis?

Answer: Inclusion Body Myositis (IBM)

Classic features: (1) Age >50, male; (2) Asymmetric weakness of quadriceps (knee extension) and finger flexors (FDP) — the hallmark IBM pattern; (3) Moderately elevated CK; (4) Mixed myopathic + neurogenic EMG pattern (characteristic of IBM); (5) Refractory to immunosuppression (failed prednisone). Biopsy would show rimmed vacuoles, endomysial CD8+ T cell inflammation, and TDP-43+ inclusions. Anti-cN1A antibody may be positive (~33-51%). Key teaching: IBM is the most important acquired myopathy to NOT treat with chronic immunosuppression — focus on physiotherapy and supportive care. Avoid the common mistake of escalating immunotherapy for a "non-responding PM."

▼5.6 Other NMJ Disorders & Peripheral Neuropathy Overview

Lambert-Eaton Myasthenic Syndrome (LEMS)

Feature	Details
Pathogenesis	Antibodies against P/Q-type voltage-gated calcium channels (VGCC) at presynaptic nerve terminal → ↓ ACh release
Association	60% paraneoplastic (SCLC — small cell lung cancer); 40% autoimmune
Clinical	Proximal weakness (LE > UE); fatigable but initial facilitation (improves with exercise then fatigues); areflexia that improves post-exercise; autonomic dysfunction (dry mouth #1, constipation, ED)
Diagnosis	Anti-VGCC Ab (P/Q-type); RNS: low baseline CMAP with >100% increment at 20-50 Hz stimulation or post-exercise; ⚠️ Screen for SCLC (CT chest, PET-CT)
Treatment	Treat underlying cancer first; symptomatic: 3,4-diaminopyridine (3,4-DAP/amifampridine) — blocks K+ channels → prolongs presynaptic depolarization → ↑ Ca²+ entry → ↑ ACh release; pyridostigmine as adjunct; IVIG/PLEX for severe; immunosuppression for autoimmune LEMS

MG vs LEMS — Quick Comparison

Feature	MG	LEMS
Antibody target	Postsynaptic (AChR/MuSK)	Presynaptic (VGCC)
Weakness pattern	Ocular/bulbar → generalized	Proximal LE → UE; less ocular
Reflexes	Normal or present	Absent → improve post-exercise
Autonomic	Not typical	Prominent (dry mouth, constipation)
RNS pattern	Decrement at low frequency	Low CMAP baseline + increment >100% at high frequency
Cancer	Thymoma (10-15%)	SCLC (60%)

Botulism

🔑 Botulism — Descending Paralysis:
• Pathogenesis: Clostridium botulinum toxin blocks presynaptic ACh release (cleaves SNARE proteins)
• Forms: Foodborne (most common adult), wound, infant (honey ingestion), iatrogenic
• Clinical triad: (1) Descending symmetric flaccid paralysis (cranial nerves first → limbs → respiratory); (2) Autonomic dysfunction (mydriasis → fixed dilated pupils, dry mouth, constipation, urinary retention); (3) Alert mental status — NO sensory deficit
• Key distinction from GBS: Descending (vs ascending in GBS); pupils affected; no sensory changes; NCS: low CMAPs with increment on rapid RNS
• Treatment: Antitoxin (trivalent ABE or heptavalent) ASAP; supportive care + ICU; aminoglycosides/NMJ-blocking drugs CONTRAINDICATED

Congenital Myasthenic Syndromes (CMS)

Genetic (non-autoimmune) disorders of NMJ transmission. Onset: birth to childhood. Types: presynaptic (ChAT deficiency), synaptic (endplate AChE deficiency), postsynaptic (AChR subunit mutations — most common; slow-channel/fast-channel CMS; rapsyn deficiency; Dok-7 CMS). Treatment varies by subtype — AChEI effective for some; 3,4-DAP for presynaptic; quinidine/fluoxetine for slow-channel; salbutamol/ephedrine for Dok-7 CMS. ⚠️ AChEI may WORSEN slow-channel CMS and Dok-7.

Approach to Peripheral Neuropathy (Overview)

📋 Peripheral Neuropathy — Systematic Approach

Classification by anatomy: Mononeuropathy / mononeuritis multiplex / polyneuropathy / radiculopathy / plexopathy
Classification by fiber type: Motor-predominant (GBS, CIDP, MMN, CMT) / Sensory-predominant (diabetic, B12, paraneoplastic) / Autonomic (diabetic, amyloid, GBS)
Classification by pathology: Demyelinating (prolonged DL, slow CV, conduction block) vs Axonal (low amplitudes, preserved CV)
Time course: Acute (<4 wk: GBS, vasculitis, toxin) / Subacute (4 wk-2 mo) / Chronic (>2 mo: CIDP, CMT, metabolic, diabetic)

Hand Weakness Differential Approach

Unilateral Hand Weakness/Wasting	Bilateral Hand Weakness/Wasting
Monomelic amyotrophy (Hirayama)	Motor neuron disease (ALS)
C8-T1 radiculopathy	Syringomyelia (dissociated sensory loss)
Lower trunk plexopathy	Cervical spondylotic myelopathy
MMN with conduction block	Polio-like myelopathy
Ulnar/median neuropathy

🔑 Wasted Hand Approach:
• APB wasting only → median nerve (C8-T1, thenar)
• ADM/1st DI wasting → ulnar nerve (C8-T1, hypothenar/interossei)
• All three (APB + ADM + 1st DI) → multiple possibilities: spinal cord (anterior horn), MND, C7-T1 root/plexus, peripheral neuropathy, distal myopathy

Multifocal Motor Neuropathy (MMN)

💊 MMN — Treatable ALS Mimic

Clinical: Asymmetric, distal > proximal, upper limb predominant; pure motor; NO UMN signs
EDx: Motor conduction block at non-compressible sites (key finding!); normal sensory NCS
Antibody: Anti-GM1 IgM (50%)
Treatment: IVIG (first-line — high response rate); steroids are NOT effective and may worsen; PLEX not beneficial

▼5.7 Key References & Guidelines — Neuromuscular Disorders

📚 Guidelines

[G1] Thai MG Guideline — SNAC/Siriraj protocol (Kumutpongpanich T, SNAC 13th, 2025)
[G2] EAN/PNS Guideline on Diagnosis and Treatment of GBS (van Doorn et al, Eur J Neurol 2023;30:3646-3674)
[G3] EAN Guideline on ALS Management (Van Damme et al, Eur J Neurol 2024;31:e16264)
[G4] International consensus guidance on management of MG (Sanders et al, Neurology 2016)
[G5] EFNS/PNS CIDP Guidelines 2021

📊 Landmark Trials

[T1] MGTX Trial 2016 — Thymectomy + pred vs pred alone in non-thymomatous AChR+ gMG → better QMG, less steroids (Wolfe GI et al, NEJM 2016;375:511-522)
[T2] REGAIN 2017 — Eculizumab in refractory generalized AChR+ MG (Howard JF et al, Lancet Neurol 2017;16:976-986)
[T3] ADAPT 2021 — Efgartigimod (anti-FcRn) in generalized MG (Howard JF et al, Lancet Neurol 2021;20:526-536)
[T4] CHAMPION-MG 2022 — Ravulizumab in generalized MG (Vu T et al, NEJM 2022;386:1132-1142)
[T5] RAISE 2023 — Zilucoplan in generalized MG
[T6] MycarinG 2023 — Rozanolixizumab in AChR/MuSK MG
[T7] SID-GBS 2021 — Second IVIG dose in GBS: no benefit, more AEs
[T8] VALOR 2022 — Tofersen for SOD1-ALS (Miller TM et al, NEJM 2022;387:1099-1110)
[T9] CENTAUR 2020 — AMX0035 in ALS (Paganoni S et al, NEJM 2020;383:919-930)
[T10] ProDERM 2021 — IVIG in dermatomyositis

📖 Key Reviews

MG subgroups — Gilhus NE, NEJM 2016;375:2570-81
MG pathogenesis — Neurotherapeutics 2016;13:118-131
ALS Clinical Review — Masrori P, Van Damme P, Eur J Neurol 2020;27:1918-1929
ALS Nature Reviews Primer — Hardiman O et al, Nat Rev Dis Primers 2017;3:17085
ALS classification — Al-Chalabi A et al, Lancet Neurol 2016;390:2084-2098
IIM classification — Greenberg SA, Nat Rev Rheum 2018
Myositis antibodies — Meyer A et al, Joint Bone Spine 2018;85:23-33

6. Demyelinating Diseases & Neuroimmunology

This section provides a comprehensive subspecialist-depth review of CNS demyelinating and neuroimmune disorders. Coverage includes MS (McDonald 2017 → 2024 criteria with all 10 updates, complete DMT landscape, BTK inhibitors), NMOSD (IPND 2015/NEMOS 2023, AQP4-IgG astrocytopathy, targeted biologics — eculizumab/satralizumab/inebilizumab), MOGAD (2023 diagnostic criteria, clinical phenotypes), Autoimmune Encephalitis (Graus 2016, antibody-specific syndromes), ADEM, and comprehensive differential diagnosis.

6.1 Multiple Sclerosis (MS)

6.1.1 Epidemiology & Risk Factors

Multiple sclerosis is the most common chronic inflammatory demyelinating disease of the CNS, affecting approximately 2.8 million people worldwide (Atlas of MS, 3rd edition 2020). Prevalence follows a striking latitude gradient — increasing with distance from the equator — with the highest rates in Northern Europe, North America, and Australasia (>100/100,000). In Southeast Asia, including Thailand, prevalence is lower (~5–20/100,000) but rising with improved diagnostic awareness.

Key Epidemiological Features of MS
Feature	Details
Peak onset age	20–40 years (can occur at any age; pediatric MS ~3–5% of cases)
Sex ratio	F:M ≈ 3:1 (increasing over time, suggesting environmental factors)
Genetic risk	HLA-DRB1*15:01 strongest (OR ~3); >200 non-HLA susceptibility variants identified
EBV	Strongest environmental risk factor; HR 32.4 for MS after EBV seroconversion (Bjornevik et al., Science 2022); virtually 100% EBV seropositive in MS
Vitamin D	Low 25(OH)D associated with ↑ MS risk and relapse rate; explains latitude gradient partially
Smoking	1.5–1.8× increased risk; accelerates progression; dose–response relationship
Obesity	Adolescent obesity (BMI >30) doubles MS risk, especially in females
Other factors	Night-shift work, organic solvents, gut microbiome dysbiosis under investigation

Clinical Pearl — EBV & MS: The landmark longitudinal study of 10 million US military personnel (Bjornevik et al., Science 2022) demonstrated that EBV infection preceded MS onset in virtually all cases, with a 32-fold increased risk after seroconversion. Other herpesviruses showed no association. This supports the hypothesis that EBV is necessary but not sufficient for MS development — additional genetic (HLA) and environmental triggers are required.

6.1.2 Pathogenesis

MS pathogenesis involves two complementary mechanisms:

A. Relapsing Focal Inflammation (Acute Relapses)

Peripheral activation: Autoreactive CD4+ T-cells (Th1/Th17) are activated in the periphery, likely by molecular mimicry (EBV peptides cross-reacting with myelin antigens)
BBB transmigration: Activated T-cells cross the blood–brain barrier via adhesion molecules — VLA-4/VCAM-1 and LFA-1/ICAM-1 interactions (therapeutic target of natalizumab)
CNS immune cascade: Reactivated T-cells recruit macrophages, B-cells, and plasma cells → release pro-inflammatory cytokines (IFN-γ, IL-17, TNF-α) → demyelination and axonal injury
B-cell involvement: Intrathecal B-cells produce oligoclonal IgG bands (OCBs); B-cells serve as APCs and cytokine sources (target of anti-CD20 therapies)
Complement activation & antibody-mediated damage in active lesions

B. Smouldering / Compartmentalized Inflammation (Progression)

Microglial activation: Chronic microglia/macrophage activation at lesion edges → slowly expanding lesions (SELs) visible as paramagnetic rim lesions (PRLs) on susceptibility-weighted MRI
Meningeal inflammation: Tertiary lymphoid follicle-like structures in meninges (especially in SPMS) → subpial cortical demyelination
Oxidative stress: Mitochondrial dysfunction, iron accumulation, virtual hypoxia in chronically demyelinated axons → neurodegeneration independent of acute inflammation
Failure of remyelination: Oligodendrocyte precursor cells (OPCs) present but fail to differentiate → persistent naked axons vulnerable to degeneration

High-Yield: MS Pathogenesis Summary

Relapses = focal inflammatory demyelination (T-cell/B-cell driven, BBB breach, Gd-enhancing lesions on MRI)
Progression = smouldering neurodegeneration (microglia/iron-rim lesions, meningeal inflammation, brain atrophy) — occurs INDEPENDENT of relapses and begins early in the disease course. This dual-mechanism model explains why anti-inflammatory DMTs reduce relapses but have limited impact on progression in advanced disease.

6.1.3 Clinical Features & Phenotypes

MS Phenotype Classification (Lublin 2014 / Updated)

MS Clinical Phenotypes
Phenotype	Frequency	Key Features
Radiologically Isolated Syndrome (RIS)	~5% of incidental MRI findings	Incidental MRI lesions meeting DIS criteria without clinical symptoms; ~30–50% convert to CIS/MS within 5–10 years. Now can be diagnosed as MS under McDonald 2024 if criteria met.
Clinically Isolated Syndrome (CIS)	First presentation	First clinical demyelinating event (ON, myelitis, brainstem syndrome); monophasic at presentation. Conversion to MS: ~60–80% if brain MRI abnormal, ~20% if normal.
Relapsing-Remitting MS (RRMS)	~85% at onset	Discrete relapses with full or partial recovery; no progression between relapses. Median age onset 30 years.
Secondary Progressive MS (SPMS)	~50% of RRMS convert by 15–20 years	Gradual neurological decline independent of relapses; may have superimposed relapses (active SPMS) or not (non-active SPMS). Retrospective diagnosis — no single biomarker.
Primary Progressive MS (PPMS)	10–15%	Progressive accumulation from onset without initial relapses; equal sex ratio; older onset (~40–50 years); spinal cord predominant; fewer Gd-enhancing lesions.

Common Clinical Presentations

MS Clinical Syndromes
Syndrome	Clinical Features	Notes
Optic Neuritis	Unilateral eye pain (worse with eye movement), subacute visual loss, RAPD, dyschromatopsia, central scotoma	Most common initial presentation (~25%); typically recovers well
Transverse Myelitis	Asymmetric/partial myelopathy, Lhermitte sign, band-like sensory level, UMN signs below level, bladder dysfunction	MS myelitis: short segment (<3 vertebral segments), peripheral/dorsal cord, partial cross-section (vs NMOSD LETM)
Brainstem/Cerebellar	INO (MLF syndrome), diplopia, vertigo, trigeminal neuralgia, facial palsy, ataxia, nystagmus	INO in young patient highly suggestive of MS
Sensory	Numbness, tingling, Lhermitte sign (electric sensation down spine on neck flexion), neuropathic pain	Most common symptom category overall
Motor	Spastic paraparesis, monoparesis, UMN signs	Rarely pure motor at onset
Cognitive	Processing speed ↓, memory retrieval ↓, executive dysfunction; affects 40–65% of MS patients	Screen with SDMT (Symbol Digit Modalities Test) or BICAMS; can occur early
Fatigue	Present in >80%; most disabling symptom reported by patients	Central (CNS-driven) + peripheral components; multifactorial

Clinical Pearl — Uhthoff Phenomenon: Transient worsening of neurological symptoms with body temperature elevation (exercise, hot bath, fever). Caused by temperature-dependent conduction block in demyelinated axons. Pathognomonic for demyelination but NOT a relapse — symptoms resolve with cooling. Important to distinguish from true relapse for treatment decisions.

6.1.4 Diagnostic Criteria: McDonald 2017 → 2024

The McDonald criteria remain the gold standard for MS diagnosis, enabling earlier diagnosis by combining clinical, MRI, and laboratory evidence. The 2024 revision represents a paradigm shift with 10 major updates that improve sensitivity while maintaining specificity.

Fundamental Diagnostic Principle

High-Yield: MS Diagnosis Core Concept

MS = Dissemination in Space (DIS) + Dissemination in Time (DIT) − Other Diseases
Simplified: ≥2 attacks affecting ≥2 different CNS areas, with exclusion of mimics
McDonald criteria allow MRI and CSF to substitute for clinical evidence of DIS/DIT.

McDonald 2017 Framework (Baseline Reference)

McDonald 2017 Criteria — Clinical Scenarios
Clinical Presentation	Additional Data Needed for MS Diagnosis
≥2 attacks + objective evidence of ≥2 lesions	None (DIS + DIT met clinically)
≥2 attacks + objective evidence of 1 lesion	DIS: ≥1 T2 lesion in ≥2 of 4 MS-typical regions (periventricular, cortical/juxtacortical, infratentorial, spinal cord) OR await further attack
1 attack + objective evidence of ≥2 lesions	DIT: simultaneous Gd+ and Gd− lesions OR new T2/Gd+ on follow-up OR CSF OCBs
1 attack + objective evidence of 1 lesion (CIS)	DIS + DIT as above
Insidious progression (suspected PPMS)	≥1 year progression + 2 of 3: ≥1 periventricular/cortical/juxtacortical T2 lesion, ≥2 spinal cord T2 lesions, CSF OCBs

McDonald 2024: The 10 Key Updates

McDonald 2024 — Revision Committee (Lancet Neurol 2025): International panel revision incorporating advances in MRI technology, biomarkers, and understanding of MS across age groups and phenotypes.

McDonald 2024 — Ten Major Updates
#	Update	Details	Clinical Impact
1	Optic nerve as 5th DIS topography	Optic nerve added to DIS locations: periventricular, cortical/juxtacortical, infratentorial, spinal cord, optic nerve. Evidence: clinical ON, RAPD, VEP abnormality, or MRI optic nerve lesion.	Patients with ON + 1 other lesion location now meet DIS (previously needed ≥2 of only 4 regions)
2	DIS requires ≥2 of 5 topographies	Threshold unchanged at ≥2 regions but now from 5 (not 4) possible topographies	Additional optic nerve pathway increases DIS sensitivity
3	DIT no longer always required	If DIS met + CSF positive (OCBs or kFLC) → MS diagnosis without DIT. Rationale: CSF+ indicates chronic intrathecal inflammation serving as biological surrogate for DIT.	Major change — enables diagnosis at first attack (CIS) with DIS + CSF+ without waiting for new MRI activity. Accelerates treatment initiation.
4	Central Vein Sign (CVS) — Select-6	CVS on T2-weighted/FLAIR MRI: ≥3 perivenular lesions among 6 selected lesions (Select-6 method) can substitute for DIS. Sensitivity 59–89%, specificity 75–98%.	Distinguishes MS from mimics (migraine, NMOSD, vascular) where CVS prevalence is low (<40%)
5	Paramagnetic Rim Lesions (PRL)	≥1 PRL on susceptibility-weighted imaging → contributes to DIS and/or supports MS diagnosis. PRLs represent chronic active lesions with iron-laden microglia. Specificity ~98% for MS.	Identifies smouldering inflammation; PRLs rare in NMOSD/MOGAD. Promising biomarker for progression.
6	Kappa Free Light Chain (kFLC) index	kFLC index >6.1 accepted as alternative to OCBs for CSF+ determination. Quantitative, cheaper, faster, easier to standardize than isoelectric focusing for OCBs.	CSF+ = OCBs (pattern 2/3) OR kFLC index >6.1. Improves access in labs without OCB capability.
7	RIS can now be MS	Radiologically Isolated Syndrome meeting DIS + DIT or DIS + CSF+ can be diagnosed as MS even without clinical symptoms.	Enables earlier treatment of high-risk RIS (previously had to wait for clinical event)
8	Unified pediatric/adult criteria	Same criteria apply to all ages (previously pediatric MS required different approach, especially for ADEM distinction in children <11 years)	Simplifies pediatric MS diagnosis; reduces diagnostic delay in children
9	Unified relapsing/progressive framework	PPMS and relapsing MS now share a unified diagnostic framework. PPMS criteria: ≥1 year progression + DIS (≥2 of 5 topographies or CVS) + CSF+ or DIT.	Recognizes MS as a single disease spectrum rather than distinct subtypes
10	Stricter criteria for age ≥50	For patients aged ≥50 at first presentation: mandatory CSF+ (OCBs or kFLC) regardless of MRI findings, due to higher prevalence of vascular/degenerative mimics.	Reduces misdiagnosis in older adults where small vessel disease and other mimics are common

Clinical Pearl — DIT No Longer Required (Update #3): This is perhaps the most practice-changing update. Previously, a patient presenting with CIS and MRI showing DIS still needed either (a) simultaneous Gd+/Gd− lesions, (b) new lesions on follow-up MRI, or (c) CSF OCBs to demonstrate DIT. Under McDonald 2024, DIS + CSF+ = MS without needing DIT at all. This means a patient with a first clinical event, lesions in ≥2/5 topographies, and positive OCBs or kFLC >6.1 can be diagnosed and treated immediately.

McDonald 2017 vs 2024: Side-by-Side Comparison

Key Differences: McDonald 2017 → 2024
Feature	McDonald 2017	McDonald 2024
DIS topographies	4 (periventricular, cortical/juxtacortical, infratentorial, spinal cord)	5 (+ optic nerve)
DIT requirement	Always required (clinical, MRI, or OCBs as surrogate)	Not always required — DIS + CSF+ suffices
CSF+ definition	OCBs only (IgG, pattern 2/3)	OCBs OR kFLC index >6.1
CVS	Not included	Select-6 method: ≥3/6 perivenular → supports DIS
PRL	Not included	≥1 PRL on SWI → contributes to DIS/diagnosis
RIS	Cannot be diagnosed as MS	Can be diagnosed as MS (DIS + DIT or DIS + CSF+)
Pediatric criteria	Separate considerations	Unified with adult criteria
Progressive MS	Separate PPMS criteria	Unified framework with relapsing MS
Age ≥50	Same criteria for all ages	Mandatory CSF+ for ≥50 years
Optic nerve	Not a DIS region	5th DIS topography (clinical, VEP, or MRI)

6.1.5 MRI Features in MS

MS MRI Characteristics
Feature	Description	Significance
Periventricular lesions	Ovoid, perpendicular to ventricles (Dawson fingers) on sagittal FLAIR	Most specific topography for MS; reflect perivenular inflammation
Cortical/juxtacortical	Lesions touching or within cortex; U-fiber lesions	DIR (double inversion recovery) most sensitive for cortical lesions
Infratentorial	Brainstem (pons, medulla, midbrain), cerebellar peduncles	Common in MS; help distinguish from vascular disease
Spinal cord	Short-segment (<3 vertebral segments), dorsolateral/peripheral, partial cross-section	Distinguish from NMOSD (LETM ≥3 segments, central cord)
Optic nerve	T2/STIR hyperintensity, Gd enhancement in acute ON; typically unilateral, anterior segment	New DIS region in McDonald 2024
Gadolinium enhancement	Open-ring enhancement pattern; homogeneous or incomplete ring	Active inflammation; enhances for ~2–8 weeks. Open ring ≈ MS; closed ring → consider abscess/tumor
Central Vein Sign (CVS)	Central venule within white matter lesion on T2/FLAIR	~85% of MS lesions have CVS vs <40% in mimics. Select-6: ≥3/6 perivenular → supports MS
Paramagnetic Rim Lesion (PRL)	Dark rim on phase/SWI; represents iron-laden microglia at lesion edge	Chronic active lesion; specificity ~98% for MS; marker of smouldering inflammation. ≥1 PRL supports MS in McDonald 2024
T1 black holes	Hypointense on T1 (chronic lesions)	Reflect severe tissue destruction, axonal loss; correlate with disability
Brain atrophy	Global and regional volume loss; >0.4%/year pathological	Correlates with cognitive decline and progression; measured by BPF (brain parenchymal fraction)

High-Yield: MRI Clues — MS vs NMOSD vs MOGAD

MS: Ovoid perpendicular periventricular (Dawson fingers), short-segment cord lesions, CVS+, PRL+
NMOSD: LETM (≥3 segments, central cord, H-sign on axial), area postrema lesion, non-specific brain lesions or normal, no Dawson fingers
MOGAD: Fluffy/ill-defined bilateral ON, ADEM-like large fluffy brain lesions, conus/lower cord LETM, cortical encephalitis (FLAIR cortical signal)

6.1.6 CSF Analysis & Biomarkers

CSF & Serum Biomarkers in MS
Biomarker	Method/Threshold	Interpretation
Oligoclonal Bands (OCBs)	Isoelectric focusing + immunofixation; Pattern 2 (CSF only) or Pattern 3 (CSF > serum)	Positive in ~95% of MS; indicates intrathecal IgG synthesis. Rare in NMOSD (<20–25%), variable in MOGAD.
Kappa Free Light Chains (kFLC) index	kFLC index = (CSF kFLC / serum kFLC) ÷ (CSF albumin / serum albumin); >6.1 = positive	Alternative to OCBs in McDonald 2024. Quantitative, reproducible, lower cost. Sensitivity comparable to OCBs (~90–95%).
IgG index	(CSF IgG / serum IgG) ÷ (CSF albumin / serum albumin); >0.7 positive	Less sensitive than OCBs (~70–80%); not included in McDonald criteria but supportive
MRZ reaction	Intrathecal antibody response to Measles, Rubella, Varicella-Zoster; ≥2 positive = MRZR+	Positive in ~67% MS; absent in NMOSD. Highly specific polyspecific intrathecal immune response.
Neurofilament Light Chain (NfL)	Serum or CSF; no universal threshold (age-adjusted)	Marker of axonal injury; elevated during relapses and in progressive MS. Useful for monitoring treatment response; lower = less neuroaxonal damage. Elevated in many neurological diseases (not MS-specific).
GFAP	Serum or CSF	Marker of astrocytic damage; elevated in NMOSD (astrocytopathy) >> MS. Rising interest as progression biomarker in MS. Markedly elevated in NMOSD attacks (reflects astrocyte destruction).
AQP4-IgG	Cell-based assay (CBA) preferred; sensitivity >80%, specificity >99%	Must be negative to diagnose MS. If positive → NMOSD.
MOG-IgG	Live CBA; IgG1 isotype	Must be negative to diagnose MS. If positive → MOGAD.

Clinical Pearl — When to Test AQP4/MOG Antibodies: Test for AQP4-IgG and MOG-IgG in any patient with: (1) LETM (≥3 segments), (2) severe/bilateral/recurrent optic neuritis, (3) area postrema syndrome, (4) periependymal brain lesions, (5) atypical MS features (OCB−, poor recovery), (6) coexisting autoimmune disease (SLE, Sjögren's). Do NOT routinely test in typical MS with classic Dawson fingers and OCB+.

6.1.7 Disease-Modifying Therapies (DMTs) — Complete Landscape

Over 20 DMTs are now approved for MS, representing one of the richest therapeutic landscapes in neurology. The choice of DMT depends on disease activity, phenotype, patient factors (age, sex, comorbidities, family planning), JCV status, and treatment strategy (escalation vs induction).

Platform / Moderate-Efficacy DMTs

Moderate-Efficacy DMTs
Drug	Mechanism	Route/Frequency	ARR Reduction	Key Adverse Effects
Interferon β-1a (Avonex, Rebif)	Immunomodulatory (↓Th17, ↑Treg, ↓BBB permeability)	IM weekly (Avonex) / SC 3×/week (Rebif)	~30%	Flu-like symptoms, injection site reactions, hepatotoxicity, depression, lymphopenia
Interferon β-1b (Betaferon)	Same as above	SC every other day	~30%	Same as above; neutralizing antibodies may reduce efficacy
Peginterferon β-1a (Plegridy)	Pegylated IFN-β	SC every 2 weeks	~36%	Same class effects; less frequent dosing improves adherence
Glatiramer acetate (Copaxone)	Shifts Th1→Th2; myelin decoy	SC daily or 3×/week (40mg)	~30%	Injection site reactions, lipoatrophy, immediate post-injection reaction (flushing, chest tightness — benign)
Teriflunomide (Aubagio)	DHODH inhibitor → ↓ proliferating lymphocytes	Oral daily (14mg)	~30–36%	Hair thinning, diarrhea, hepatotoxicity, teratogenic (pregnancy category X — requires accelerated elimination with cholestyramine/charcoal before conception)
Dimethyl fumarate (DMF) (Tecfidera)	Nrf2 activation → antioxidant + anti-inflammatory; ↓ NFκB	Oral BID (240mg)	~44–53%	Flushing, GI (nausea, diarrhea), lymphopenia (monitor ALC — risk of PML if severe), hepatotoxicity
Diroximel fumarate (Vumerity)	Same as DMF (active metabolite monomethyl fumarate)	Oral BID	Similar to DMF	Better GI tolerability than DMF; same lymphopenia risk

High-Efficacy DMTs

High-Efficacy DMTs
Drug	Mechanism	Route/Frequency	ARR Reduction	Key Adverse Effects & Monitoring
Fingolimod (Gilenya)	S1P receptor modulator → lymphocyte sequestration in lymph nodes	Oral daily (0.5mg)	~54%	First-dose bradycardia (6-hour monitoring), macular edema, ↑ infections (VZV/HSV — check VZV immunity), hepatotoxicity, skin cancers, rebound on discontinuation
Siponimod (Mayzent)	Selective S1P1/S1P5 modulator	Oral daily (2mg maintenance)	SPMS: ↓ 3-month CDP by 21% (EXPAND trial)	Similar to fingolimod; CYP2C9 genotype required (avoid 3/3); approved for active SPMS
Ozanimod (Zeposia)	Selective S1P1/S1P5	Oral daily (0.92mg)	~38–48%	Similar class; less first-dose effect; dose titration over 7 days
Ponesimod (Ponvory)	Selective S1P1	Oral daily (20mg)	Superior to teriflunomide (~30.5% relative reduction)	Similar class; rapid lymphocyte recovery on cessation (~1 week)
Natalizumab (Tysabri)	Anti-α4-integrin (VLA-4) → blocks lymphocyte migration across BBB	IV q4wk or SC q4wk	~68%	PML risk — stratify by: JCV Ab status, JCV index, prior immunosuppression, duration >2 years. JCV Ab−: risk ~0.1/1000; JCV Ab+ index >1.5 + prior IS + >2yr: risk up to 11/1000. Extended interval dosing (EID, q6wk) may ↓ PML risk. Rebound on discontinuation.
Ocrelizumab (Ocrevus)	Anti-CD20 (humanized) → B-cell depletion	IV q6mo (initial: 300mg ×2 two weeks apart; then 600mg q6mo)	~46–47% (OPERA I/II); PPMS: ↓ 12-wk CDP by 24% (ORATORIO)	Infusion reactions, ↑ infections (screen HBV), hypogammaglobulinemia (long-term IgG monitoring), only DMT approved for PPMS
Ofatumumab (Kesimpta)	Anti-CD20 (fully human) → B-cell depletion	SC monthly (20mg; initial: day 0, 7, 14 then monthly)	~50–58% (ASCLEPIOS I/II)	Injection site reactions, similar infection/Ig monitoring as ocrelizumab; self-administered at home
Ublituximab (Briumvi)	Anti-CD20 (glycoengineered) → enhanced ADCC	IV q6mo (1-hour infusion after initial)	~55–59% (ULTIMATE I/II)	Similar to other anti-CD20s; shorter infusion time advantage
Alemtuzumab (Lemtrada)	Anti-CD52 → pan-lymphocyte depletion (IRT)	IV 5 days Y1, 3 days Y2 (±additional courses)	~49–55% (CARE-MS I/II)	Secondary autoimmunity: thyroid (40%), ITP (3%), anti-GBM disease (0.3%); monthly blood/urine monitoring for 4 years post-last dose. Infections (VZV prophylaxis). Reserved for highly active MS.
Cladribine (Mavenclad)	Purine analogue (IRT) → selective lymphocyte depletion (preferential B-cell/T-cell reduction)	Oral: 2 short courses in Y1 + Y2 (cumulative 3.5mg/kg); then treatment-free	~55–58% (CLARITY)	Lymphopenia (nadir ~2–3 months, recovery by ~9 months), herpes reactivation (consider prophylaxis if Grade 4), malignancy concern (theoretical, not confirmed in extensions)
Mitoxantrone	Topoisomerase II inhibitor → immunosuppression	IV q3mo (max lifetime dose 140 mg/m²)	~67%	Cardiotoxicity (cardiomyopathy — LVEF monitoring), therapy-related AML (~0.8%); rarely used now due to toxicity; legacy agent

Pipeline / Emerging Therapies

Emerging MS Therapies
Agent	Mechanism	Status	Notes
Tolebrutinib	CNS-penetrant BTK inhibitor → targets microglia + B-cells in CNS	Phase 3 (HERCULES, PERSEUS, GEMINI)	First DMT potentially targeting smouldering inflammation; hepatotoxicity signal in trials
Fenebrutinib	Non-covalent BTK inhibitor	Phase 3 (FENtrepid, FENhance)	Highly selective; targets both relapsing and progressive MS
Evobrutinib	BTK inhibitor	Phase 3 (evolutionRMS)	Did not meet primary endpoint in RRMS; development uncertain
Frexalimab	Anti-CD40L → blocks T-cell co-stimulation	Phase 3	Near-complete suppression of MRI activity in Phase 2
Remyelination therapies	Various: anti-LINGO-1 (opicinumab), clemastine, bexarotene	Early phase	Aiming to repair rather than prevent damage; unmet need in progressive MS

High-Yield: BTK Inhibitors — The Next Frontier

Bruton's tyrosine kinase (BTK) inhibitors are unique because they cross the BBB and can target both B-cells and microglia/macrophages within the CNS compartment. This makes them the first DMT class with potential to address smouldering/compartmentalized inflammation driving progression — a mechanism not reached by current anti-CD20 antibodies (which deplete peripheral B-cells but do not cross the BBB). If successful, BTKi could be transformative for progressive MS.

6.1.8 Treatment Strategy

Escalation vs Induction vs Early High-Efficacy

MS Treatment Strategies
Strategy	Approach	When to Consider
Escalation	Start moderate-efficacy DMT (IFN-β, GA, DMF, teriflunomide) → switch to high-efficacy if breakthrough	Low disease activity, risk-averse patient, older age, mild CIS
Early High-Efficacy (EHT)	Start with high-efficacy DMT (natalizumab, anti-CD20, S1P modulators) from diagnosis	Young patient with active disease, ≥2 relapses/year, Gd+ lesions, high T2 lesion load, poor prognostic factors, spinal cord lesions. Increasing evidence favors EHT: DELIVER-MS, TREAT-MS trials show benefit.
Immune Reconstitution Therapy (IRT)	Short-course treatment (alemtuzumab, cladribine) aiming for durable immune reset → treatment-free remission	Highly active MS, young patients wanting treatment-free periods, family planning (after washout)
AHSCT	Autologous Hematopoietic Stem Cell Transplantation — myeloablative/non-myeloablative conditioning → immune reset	Highly active relapsing MS, young (<40–50), short disease duration (<10 years), inflammatory phenotype. MIST, BEAT-MS trials show superiority over DMTs. TRM ~0.3% in experienced centers.

Clinical Pearl — Treat-to-Target in MS: Modern MS management increasingly adopts a treat-to-target approach — the target being NEDA (No Evidence of Disease Activity): (1) no relapses, (2) no new/enlarging T2 lesions, (3) no Gd-enhancing lesions, (4) no brain atrophy progression (NEDA-4). While NEDA is aspirational and difficult to maintain long-term, it guides escalation decisions. Increasingly, serum NfL is used as a fifth dimension of monitoring ("NEDA-5") — persistently elevated NfL despite DMT suggests subclinical disease activity.

6.1.9 Acute Relapse Management

Acute MS Relapse Treatment
Treatment	Regimen	Notes
IV Methylprednisolone (IVMP)	1 g/day × 3–5 days (no taper usually needed)	First-line for moderate-severe relapses. Shortens relapse duration but does not change final recovery. Check glucose, blood pressure. PPI cover if GI risk.
Oral high-dose steroids	Oral methylprednisolone 500–1250 mg/day × 3–5 days OR bioequivalent prednisone	COPOUSEP trial: oral methylprednisolone non-inferior to IV. Alternative when IV access difficult.
Plasma Exchange (PLEX)	5–7 exchanges over 10–14 days	Second-line for steroid-refractory severe relapses (especially myelitis, severe ON, brainstem). Start within 2–4 weeks of relapse onset for best response. ~40–50% of steroid-non-responders improve.
IVIG	0.4 g/kg/day × 5 days	Third-line; less evidence than PLEX for steroid-refractory relapses. May be considered when PLEX unavailable or contraindicated.

Question: A 28-year-old woman presents with right eye pain and visual loss for 3 days. MRI brain shows a right optic nerve lesion with enhancement, plus 4 periventricular T2 lesions perpendicular to the ventricles and 1 cervical cord lesion. CSF shows positive OCBs. AQP4-IgG and MOG-IgG are negative. Can she be diagnosed with MS by McDonald 2024?

Answer: Yes. By McDonald 2024:

DIS: Lesions in ≥2 of 5 topographies — optic nerve (clinical ON + MRI lesion), periventricular (4 lesions), spinal cord (cervical lesion) = 3/5 topographies → DIS met
DIT: Not strictly needed because DIS + CSF+ (OCBs positive) is sufficient for MS diagnosis under McDonald 2024 Update #3
Other diseases excluded: AQP4-IgG and MOG-IgG negative, Dawson finger-like periventricular lesions typical for MS

Under McDonald 2017, she would also meet criteria (DIS in ≥2/4 regions + DIT via OCBs as surrogate). However, note the key 2024 improvement: the optic nerve now counts as a DIS region (Update #1), and DIT is no longer required when CSF+ (Update #3). She should be started on a DMT promptly — given young age and multi-regional disease, early high-efficacy therapy should be discussed.

6.1.10 Monitoring & Special Situations

Routine MS Monitoring

MS Follow-Up Monitoring Schedule
Assessment	Frequency	Purpose
Clinical visit + EDSS	Every 3–6 months (early), 6–12 months (stable)	Detect relapses, progression, disability change
Brain MRI (with Gd)	Baseline, 3–6 months after DMT start, then annually	New/enlarging T2 lesions, Gd+ activity → breakthrough disease
Spinal cord MRI	Baseline, then if symptoms or surveillance	Cord lesions correlate with disability; less routinely monitored than brain
OCT (retinal nerve fiber layer)	Baseline, then annually or after ON	Subclinical optic nerve axonal loss; RNFL thinning correlates with brain atrophy
Cognitive screening (SDMT)	Annually	Processing speed decline; ≥4-point drop clinically meaningful
Serum NfL	Emerging — every 6–12 months	Subclinical disease activity monitoring; guide treatment decisions
DMT-specific labs	Per drug protocol	CBC/LFTs (all), JCV Ab (natalizumab q6mo), lymphocyte count (fingolimod/DMF/cladribine), thyroid/CBC/urinalysis (alemtuzumab monthly ×4yr), immunoglobulins (anti-CD20 annually)

Pregnancy & MS

MS DMTs and Pregnancy
Category	DMTs	Recommendation
Contraindicated (teratogenic)	Teriflunomide (Category X), fingolimod, siponimod, ozanimod, ponesimod, cladribine, mitoxantrone	Discontinue well before conception. Teriflunomide requires accelerated elimination (cholestyramine 8g TID × 11 days or activated charcoal 50g BID × 11 days) + serum level <0.02 mg/L confirmed ×2. S1P modulators: stop ≥2 months before; risk of rebound. Cladribine: ≥6 months washout.
Stop before conception	DMF, diroximel fumarate, alemtuzumab	Stop DMF ≥1 month before conception. Alemtuzumab: wait ≥4 months after last infusion.
May continue / consider	IFN-β, glatiramer acetate	Low risk in pregnancy; glatiramer acetate generally considered safest. Can continue until positive pregnancy test or throughout if high relapse risk.
Special consideration	Natalizumab, anti-CD20 (ocrelizumab, ofatumumab)	Natalizumab: may continue through pregnancy in highly active MS (risk of neonatal hematological effects in 3rd trimester vs severe rebound). Anti-CD20: stop ≥6 months before conception (B-cell repopulation); exposed pregnancies generally show good outcomes. Plan last infusion timing strategically.

Clinical Pearl — Pregnancy & MS Course: Relapse rate decreases during pregnancy (especially 3rd trimester — natural immunotolerance) but increases in the first 3–6 months postpartum (return to 70% of pre-pregnancy rate or higher). Exclusive breastfeeding may be protective. Strategy: in highly active MS, consider "bridging" with natalizumab during pregnancy or timing last anti-CD20 dose ~6 months before planned conception so B-cells repopulate during pregnancy with residual immunosuppressive effect. Resume DMT promptly postpartum, especially in active disease — breastfeeding is compatible with many DMTs (GA, IFN-β, and increasingly anti-CD20 considered acceptable).

6.2 Neuromyelitis Optica Spectrum Disorder (NMOSD)

6.2.1 Epidemiology & Risk Factors

NMOSD Epidemiology
Feature	Details
Prevalence	~1.54/100,000 (varies by ethnicity — higher in non-White populations: African, Asian, Latin American)
Incidence	~0.4–4.4/million/year
Peak onset age	~40 years (later than MS); range 18–70; rare in children
Sex ratio	F:M ≈ 9:1 (one of the strongest female predominance in autoimmune disease)
Genetic risk	HLA-DRB1*03:01 strongest association; non-HLA variants near complement genes
Ethnicity	Higher prevalence in non-White populations; in Asia, NMO/NMOSD was previously classified as "opticospinal MS"
Autoimmune associations	SLE, Sjögren syndrome, myasthenia gravis, autoimmune thyroid disease — screen for coexisting autoimmunity

6.2.2 Pathogenesis

NMOSD is an autoimmune astrocytopathy — fundamentally different from MS in mechanism. The target is the astrocyte, not the oligodendrocyte.

Pathogenic Cascade

Peripheral B-cell activation: Autoreactive B-cells (likely triggered by molecular mimicry — AQP4 shares homology with Clostridium perfringens ABC-TP protein) differentiate into plasmablasts producing AQP4-IgG
AQP4-IgG crosses BBB: IgG1 subclass; crosses disrupted or permeable BBB (especially at circumventricular organs — area postrema, which lacks BBB)
Binding to AQP4: AQP4-IgG binds aquaporin-4 (AQP4) water channels on astrocyte foot processes surrounding blood vessels → AQP4 internalization
Complement activation: AQP4-IgG activates classical complement cascade → C3b deposition → membrane attack complex (MAC) C5b-9 formation → astrocyte lysis (complement-dependent cytotoxicity, CDC)
Antibody-dependent cellular cytotoxicity (ADCC): AQP4-IgG also recruits NK cells and macrophages → ADCC pathway → additional astrocyte killing
Secondary demyelination: Astrocyte destruction → loss of trophic support to oligodendrocytes → secondary demyelination and axonal injury (NOT primary demyelination as in MS)
Inflammatory infiltrate: Neutrophils and eosinophils prominent (vs macrophages/T-cells in MS) → tissue necrosis, cavitation

Key Cytokine: IL-6

IL-6 is the central cytokine in NMOSD pathogenesis:

Promotes B-cell differentiation → plasmablast → AQP4-IgG production
Increases BBB permeability
Drives inflammation via JAK-STAT pathway
CSF IL-6 levels correlate with disease activity
Therapeutic target: satralizumab (anti-IL-6R)

High-Yield: MS vs NMOSD Pathogenesis — Fundamental Difference

MS: T-cell/B-cell → primary demyelination (oligodendrocyte injury) → OCBs in CSF → macrophage-predominant infiltrate
NMOSD: AQP4-IgG → primary astrocytopathy (astrocyte destruction via complement/ADCC) → secondary demyelination → neutrophil/eosinophil-predominant infiltrate → tissue necrosis

This explains why: (1) NMOSD attacks are more severe/destructive with poor recovery, (2) MS DMTs (IFN-β, natalizumab, fingolimod) are ineffective and may worsen NMOSD, (3) complement inhibition (eculizumab) works in NMOSD but not MS.

6.2.3 Diagnostic Criteria: IPND 2015 (Wingerchuk)

International Panel for NMO Diagnosis (IPND) 2015 — Wingerchuk et al., Neurology 2015: Unified criteria replacing the 2006 NMO criteria. Introduced the spectrum concept (NMOSD) and provided separate criteria for AQP4-IgG-positive and AQP4-IgG-negative patients.

Six Core Clinical Characteristics

NMOSD Core Clinical Characteristics (IPND 2015)
#	Core Characteristic	Frequency	Key Features
1	Optic neuritis (ON)	45–60%	Severe, bilateral (simultaneous or sequential), poor recovery (vs MS ON: unilateral, good recovery). Posterior/chiasmal involvement more common than MS (anterior). RAPD, pain, severe visual loss (often <20/200).
2	Acute myelitis	~85% (most common)	LETM (longitudinally extensive transverse myelitis, ≥3 vertebral segments). Central cord involvement, complete transection pattern. Severe motor/sensory deficits, bladder dysfunction. May cause painful tonic spasms.
3	Area postrema syndrome (APS)	15–40%	Intractable nausea, vomiting, and/or hiccups lasting days–weeks. May be the presenting symptom of NMOSD in ~7–15%. Area postrema (dorsal medulla at floor of 4th ventricle) is a circumventricular organ — rich in AQP4, lacks BBB. Highly specific for NMOSD.
4	Acute brainstem syndrome	Variable	Includes: dorsal medulla lesion (area postrema), periependymal brainstem lesion, intractable hiccups/nausea, INO, facial palsy, hearing loss, trigeminal neuralgia. Not explained by area postrema alone.
5	Acute diencephalic syndrome	~3.4%	Narcolepsy/hypersomnia, SIADH, hypothermia, obesity, endocrine dysfunction from hypothalamic/thalamic lesion. Rare but characteristic.
6	Symptomatic cerebral syndrome	Rare	Large confluent/tumefactive hemispheric white matter lesions (ADEM-like or periependymal). Corpus callosum involvement (Marburg-like pattern). More common in children with NMOSD.

IPND 2015 Diagnostic Criteria

NMOSD Diagnostic Criteria — IPND 2015
AQP4-IgG Status	Criteria
AQP4-IgG POSITIVE	At least 1 core clinical characteristic Positive AQP4-IgG (cell-based assay preferred) Exclusion of alternative diagnoses
AQP4-IgG NEGATIVE or Unknown	At least 2 core clinical characteristics from ≥2 different attacks AND all of: At least 1 must be ON, myelitis with LETM, or APS Dissemination in space (≥2 different core characteristics) Additional MRI requirements met for each characteristic Negative AQP4-IgG or testing unavailable Exclusion of alternative diagnoses

Clinical Pearl — AQP4-IgG Testing: Cell-based assay (CBA) is mandatory — sensitivity >80%, specificity >99%. Older indirect immunofluorescence or ELISA methods have lower sensitivity (~60–70%) and may miss low-titer positives. Test during acute attack for highest sensitivity (titers fluctuate with immunotherapy). IgG isotype only (not IgM/IgA). Retest if initially negative in high clinical suspicion — seroconversion can occur. Always use live CBA or fixed CBA with M23 AQP4 isoform.

6.2.4 NEMOS 2023 Diagnostic Recommendations

NEMOS (Neuromyelitis Optica Study Group) 2023 — J Neurol: Practical diagnostic recommendations based on IPND 2015, with structured approach (Box 1–5) for clinical application.

NEMOS 2023 Diagnostic Framework
Box	Content	Key Points
Box 1	Core clinical characteristics	Same 6 as IPND 2015 (ON, myelitis, APS, brainstem, diencephalic, cerebral) with detailed MRI criteria for each
Box 2	MRI findings for each core characteristic	ON: long segment (>½ optic nerve), chiasmal involvement; Myelitis: LETM ≥3 segments, central cord, H-sign axial; APS: dorsal medulla/area postrema lesion; Brain: periependymal pattern
Box 3	Differential diagnoses	MS, MOGAD, sarcoidosis, CNS lymphoma, SLE cerebritis, Sjögren's CNS, infections (TB, syphilis, HIV), spinal AVF, B12 deficiency, paraneoplastic
Box 4	Red flags against NMOSD	Progressive course without attacks, Dawson finger lesions, short cord lesions, cortical lesions (→ think MS/MOGAD), CSF OCBs positive (→ MS), male sex (less against but weaker), onset <12 years
Box 5	MOGAD consideration	Always test MOG-IgG when AQP4-IgG negative; MOGAD has different phenotype and prognosis

6.2.5 Investigations

NMOSD Investigations
Investigation	Findings in NMOSD	Significance
AQP4-IgG (CBA)	Positive in ~75–80% of NMOSD patients	Highly specific (>99%); diagnostic cornerstone. CBA mandatory (ELISA/IIF insufficient).
MOG-IgG (CBA)	Negative (by definition in AQP4+ NMOSD)	Must test to exclude MOGAD if AQP4-IgG negative. Double-positive (AQP4+ MOG+) is exceedingly rare and should raise concern for false positive.
CSF cell count	Pleocytosis (often >50 WBC/μL) with neutrophil predominance during acute attacks	Helps distinguish from MS (lymphocytic, usually <50 cells). Eosinophils may also be present.
CSF OCBs	Absent in 75–80%	Major differentiator from MS (OCBs positive in ~95% of MS). If OCBs positive → strongly reconsider MS diagnosis.
CSF protein	Often elevated; elevated QAlb (albumin quotient) reflecting BBB disruption	Higher protein than typical MS
Serum GFAP	Markedly elevated during attacks (reflects astrocyte destruction)	Higher in NMOSD than MS; emerging biomarker for attack severity and monitoring
Serum NfL	Elevated during attacks	Marker of axonal injury; correlates with attack severity and disability
MRZ reaction	Absent	Positive in ~67% MS, absent in NMOSD — useful differentiator when available
MRI spine	LETM ≥3 vertebral segments; central cord (H-sign on axial T2); often thoracic; may show ring/patchy enhancement, cavitation in severe cases	LETM is hallmark; but short myelitis can occur in relapses after treatment. Acute: may show cord swelling + Gd enhancement.
MRI brain	Normal or non-specific; periependymal lesions around 3rd/4th ventricle; area postrema lesion; hypothalamic lesion; hemispheric ADEM-like. No Dawson fingers.	~60% have brain MRI abnormalities but pattern differs from MS. Periependymal = "cloud-like" enhancement.
MRI optic nerve	Posterior/chiasmal involvement; long segment (>½ nerve length); bilateral; may show "bright-spot" lesion on T1+Gd	Longer segment and posterior location vs MS (anterior, shorter). Orbital fat-suppressed T2/STIR essential.
OCT	Severe RNFL thinning after ON (often <50 μm); GCL loss	Greater damage per ON episode than MS; reflects more destructive pathology. Poor visual outcome correlates with thin RNFL.

High-Yield: CSF Clues — MS vs NMOSD vs MOGAD

MS: OCBs positive (~95%), lymphocytic mild pleocytosis (<50), normal-mildly elevated protein, MRZ reaction positive (~67%)
NMOSD: OCBs negative (~75–80%), neutrophilic pleocytosis (can be >50), elevated protein/QAlb, GFAP markedly elevated, MRZ negative
MOGAD: OCBs usually negative, lymphocytic/mixed pleocytosis, protein elevated, GFAP mildly elevated (less than NMOSD)

6.2.6 Treatment

A. Acute Attack Treatment

NMOSD Acute Attack Management
Line	Treatment	Regimen	Notes
1st line	IV Methylprednisolone	1 g/day × 3–7 days (often 5 days; can extend to 7 if severe)	Start ASAP after attack onset. Follow with oral taper (prednisone 1 mg/kg tapering over weeks) more commonly in NMOSD than MS. Longer courses often needed.
2nd line (early)	Plasma Exchange (PLEX)	5–7 exchanges over 10–14 days	Use early — some experts advocate PLEX concurrently with IVMP for severe attacks (myelitis with paraplegia, severe bilateral ON). Earlier initiation → better outcome. Removes pathogenic AQP4-IgG and complement factors.
Alternative	IVIG	0.4 g/kg/day × 5 days	Third-line; when PLEX unavailable or contraindicated. May modulate complement. Less evidence than PLEX.

Clinical Pearl — PLEX Early in NMOSD: Unlike MS where PLEX is reserved for steroid-refractory cases, in NMOSD experts increasingly advocate early/concurrent PLEX with IVMP for severe attacks (LETM with paraplegia, bilateral ON). The rationale: NMOSD is antibody/complement-mediated, so directly removing the pathogenic antibody is mechanistically logical. Delay in PLEX initiation correlates with poorer recovery. Some centers start PLEX within 48–72 hours of attack onset alongside IVMP.

B. Preventive (Maintenance) Therapy

Critical principle: ALL patients with AQP4-IgG-positive NMOSD should receive long-term preventive therapy after a first attack. Relapses are typically severe and cumulative disability is stepwise (each attack adds permanent deficit). Unlike MS, there is no significant progression between attacks — disability is attack-related.

Standard Preventive DMTs

Standard NMOSD Preventive Therapies
Drug	Mechanism	Dose	Monitoring	Notes
Azathioprine (AZA)	Purine synthesis inhibitor → ↓ T/B lymphocytes	2–3 mg/kg/day	CBC q1–3mo, LFTs, TPMT/NUDT15 genotype before starting	Widely used, affordable. Onset 3–6 months; bridge with oral prednisone. TPMT/NUDT15 deficiency → severe myelosuppression.
Mycophenolate mofetil (MMF)	IMPDH inhibitor → selective B/T-cell antiproliferative	2000–3000 mg/day (divided BID)	CBC q1–3mo, LFTs, GI symptoms	Effective alternative to AZA; may have faster onset. Teratogenic — contraception mandatory. GI side effects common.
Rituximab (RTX)	Anti-CD20 → B-cell depletion	Induction: 1000 mg × 2 (days 0, 14) or 375 mg/m² × 4 weekly; Maintenance: 1000 mg q6mo or CD19/CD20 monitoring-guided redosing	CD19/CD20 count, immunoglobulins, HBV screening, infection surveillance	Highly effective; most commonly used worldwide. Some advocate redosing based on CD19/CD27+ memory B-cell repopulation rather than fixed interval. Infusion reactions (premedicate). Long-term: hypogammaglobulinemia risk.

Targeted Biologic Therapies (Newer)

NMOSD Targeted Biologics with Trial Data
Drug	Mechanism	Regimen	Pivotal Trial	Key Results	Practical Notes
Eculizumab (Soliris)	Anti-C5 complement → blocks MAC (C5b-9) formation	900 mg IV q2wk × 4 doses → 1200 mg IV q2wk	PREVENT (NEJM 2019)	Relapse rate: 3% (eculizumab) vs 43% (placebo) over 48 weeks (HR 0.06). 97% relapse-free in treatment group.	Extremely effective but extremely costly (~$500K/year). Requires meningococcal vaccination (MenACWY + MenB) ≥2 weeks before start — risk of meningococcal sepsis. Biweekly IV infusions. Can be used on background immunosuppression.
Ravulizumab (Ultomiris)	Long-acting anti-C5 (engineered eculizumab)	Weight-based IV loading → maintenance q8wk (vs q2wk for eculizumab)	CHAMPION-NMOSD	Pending full publication; designed to show non-inferiority to eculizumab with less frequent dosing	Advantage: q8wk dosing vs q2wk; same meningococcal vaccination requirement
Satralizumab (Enspryng)	Anti-IL-6 receptor (recycling antibody)	120 mg SC at weeks 0, 2, 4 → then q4wk	SAkuraSky (NEJM 2019) & SAkuraStar (Lancet Neurol 2020)	SAkuraSky (add-on): relapse rate 20% vs 43% (HR 0.38) in AQP4+. SAkuraStar (monotherapy): 22% vs 57% (HR 0.26) in AQP4+. Most benefit in AQP4+ patients; less clear benefit in AQP4−.	Self-administered SC injection q4wk. Generally well-tolerated. Especially effective in AQP4+. Unique recycling antibody technology — longer half-life. Can be monotherapy or add-on.
Inebilizumab (Uplizna)	Anti-CD19 → broader B-cell depletion than anti-CD20 (CD19 expressed on plasmablasts and some plasma cells that CD20 misses)	300 mg IV day 0, day 15 → then 300 mg IV q6mo	N-MOmentum (Lancet 2019)	Relapse rate: 12% vs 39% (HR 0.272) over 28 weeks. 87.6% remained attack-free (vs 56.6% placebo). Also reduced disability worsening.	Advantage over rituximab: targets CD19 (broader B-lineage depletion including plasmablasts). Q6mo IV infusion. Infusion reactions; infection monitoring; HBV screening.

High-Yield: NMOSD Biologic Mechanisms — Three Distinct Pathways

The three FDA-approved biologics for NMOSD each target a different pathogenic mechanism:
1. Complement inhibition: Eculizumab/ravulizumab → blocks C5 → prevents MAC formation → stops complement-mediated astrocyte lysis
2. IL-6 blockade: Satralizumab → blocks IL-6 receptor → reduces plasmablast differentiation and AQP4-IgG production, ↓ BBB permeability
3. B-cell depletion: Inebilizumab → depletes CD19+ B-cells (broader than CD20: includes plasmablasts) → reduces AQP4-IgG production

All three showed dramatic efficacy in AQP4+ NMOSD. Choice depends on: access/cost, patient preference (SC vs IV, frequency), comorbidities, and whether monotherapy vs add-on is desired.

C. Drugs to AVOID in NMOSD

High-Yield: MS DMTs That WORSEN NMOSD

The following MS DMTs are contraindicated or potentially harmful in NMOSD:

Interferon-β: Increases relapse rate in NMOSD
Natalizumab: May worsen NMOSD (case reports of severe relapses)
Fingolimod: Reports of NMOSD exacerbation; does not prevent relapses in NMOSD
Alemtuzumab: Case reports of worsening; mechanism unclear
Dimethyl fumarate: Insufficient data; not recommended

This underscores the critical importance of distinguishing NMOSD from MS before starting treatment. Always check AQP4-IgG (and MOG-IgG) before initiating MS-specific DMTs in atypical presentations.

6.2.7 Prognosis & Disease Course

NMOSD Prognosis
Feature	Details
Course	~85–90% relapsing; ~5–10% monophasic. Progressive course is NOT a feature of NMOSD (red flag for MS).
Attack severity	More severe than MS; poor/incomplete recovery. Stepwise disability accumulation with each relapse.
Visual outcome	Functional blindness (≤20/200) in ≥1 eye in ~50% by 5–10 years without treatment
Motor outcome	Wheelchair dependence in ~30% by 5 years without treatment (due to myelitis attacks)
Mortality	5-year mortality ~5–10% (improved with modern biologics); respiratory failure from cervical myelitis or area postrema-related complications
Predictors of poor outcome	Older age at onset, African descent, many early relapses, poor recovery from first attack, high AQP4-IgG titer, coexisting autoimmune disease
With modern treatment	Dramatically improved — PREVENT trial showed 97% relapse-free on eculizumab; early aggressive prevention critical

Question: A 45-year-old woman presents with intractable nausea, vomiting, and hiccups for 2 weeks. MRI brain shows a dorsal medullary lesion. She is found to be AQP4-IgG positive. What is the diagnosis and management?

Answer:

Diagnosis: NMOSD — Area Postrema Syndrome (Core Characteristic #3). She meets IPND 2015 criteria for AQP4-IgG positive NMOSD: 1 core clinical characteristic (APS) + positive AQP4-IgG + excludes other causes.

Acute management:

IV methylprednisolone 1 g/day × 5 days
Consider PLEX if refractory to steroids

Preventive therapy (start early):

Options: rituximab, satralizumab, eculizumab, inebilizumab, or azathioprine/MMF (depending on access and resources)
Even after a "mild" first attack like APS, prevention is critical because subsequent attacks (myelitis, ON) are typically more severe

Key point: APS (intractable nausea/vomiting/hiccups) is often the first and mildest attack in NMOSD. It is frequently misdiagnosed as GI disease, causing diagnostic delay of months to years. The dorsal medullary MRI lesion in a middle-aged woman with intractable vomiting should always trigger AQP4-IgG testing.

6.3 MOG Antibody-Associated Disease (MOGAD)

6.3.1 Overview & Epidemiology

MOGAD is a distinct inflammatory demyelinating disease of the CNS, separate from both MS and NMOSD. It is defined by seropositivity for MOG-IgG (myelin oligodendrocyte glycoprotein antibodies) detected by cell-based assay. MOGAD was only recognized as a distinct entity in the 2020s, previously overlapping with "seronegative NMOSD" or ADEM.

MOGAD Epidemiology
Feature	Details
Prevalence	~1.3–3.4/100,000 (comparable to NMOSD)
Age distribution	Bimodal — pediatric peak (ADEM phenotype, median ~5–7 years) and adult peak (ON phenotype, median ~30–40 years)
Sex ratio	Slight male predominance in children (ADEM); slight female predominance in adults — overall less skewed than NMOSD (F:M ~1.2–2:1)
Course	~50% monophasic (especially pediatric ADEM); ~50% relapsing (especially adult ON). More favorable prognosis overall than NMOSD.

6.3.2 Pathogenesis

MOG is a glycoprotein expressed exclusively on the outermost surface of the myelin sheath produced by oligodendrocytes in the CNS. Unlike AQP4 (astrocyte), MOG is on the myelin/oligodendrocyte surface — making MOGAD a true primary demyelinating disease.

MOGAD vs NMOSD vs MS Pathogenesis Comparison
Feature	MOGAD	NMOSD	MS
Target	MOG on oligodendrocyte/myelin surface	AQP4 on astrocyte foot processes	Myelin/oligodendrocyte (T-cell mediated)
Primary pathology	Demyelination (oligodendrocyte injury)	Astrocytopathy (astrocyte destruction)	Demyelination + neurodegeneration
Antibody	MOG-IgG (IgG1)	AQP4-IgG (IgG1)	None specific (OCBs = polyclonal IgG)
Complement role	Limited complement deposition; less complement-mediated damage than NMOSD	Major: classical pathway → MAC → astrocyte lysis	Variable complement involvement
Pathology	Perivenous demyelination with relative axonal preservation; granulocytic infiltrate	Astrocyte loss, secondary demyelination, necrosis, neutrophil/eosinophil infiltrate	Perivenous and confluent demyelination, axonal injury, microglia activation
Remyelination	Good remyelination potential (better than MS/NMOSD)	Poor (astrocyte loss disrupts myelin repair)	Variable; fails in progressive MS

Clinical Pearl — MOGAD Has Better Remyelination: Unlike MS and NMOSD, MOGAD pathology shows perivenous demyelination with relative axonal preservation and robust remyelination capacity. This explains the generally better recovery from individual attacks compared to NMOSD (where astrocyte necrosis causes irreversible damage) and may explain why many pediatric ADEM patients recover completely.

6.3.3 Diagnostic Criteria (2023 International Panel)

MOGAD Diagnostic Criteria — Banwell et al., Lancet Neurol 2023: First international consensus diagnostic criteria for MOGAD, requiring MOG-IgG positivity + compatible clinical phenotype + exclusion of alternatives.

MOGAD 2023 Diagnostic Criteria
Criterion	Requirements
1. Core clinical presentation	At least one of: Optic neuritis Myelitis ADEM (acute disseminated encephalomyelitis) Cerebral monofocal or polyfocal deficits Brainstem/cerebellar presentation Cerebral cortical encephalitis (often with seizures)
2. MOG-IgG positive	Cell-based assay (CBA) mandatory — live CBA preferred; fixed CBA with full-length human MOG acceptable. IgG1 isotype only. Low-positive titers require compatible clinical + MRI features for diagnosis (false positives more common at low titers). Serum preferred; CSF MOG-IgG can support diagnosis if serum negative.
3. Exclusion of alternatives	Rule out MS, NMOSD (AQP4+), infection, sarcoidosis, CNS lymphoma, CLIPPERS, etc.

Clinical Pearl — MOG-IgG Testing Caveats: (1) Low-positive titers have higher false-positive rates — if titer is borderline and clinical phenotype is atypical, retest in 6–12 weeks. (2) Titers may become negative over time, especially in monophasic MOGAD — this does NOT exclude the diagnosis. (3) MOG-IgG should be tested by CBA only — ELISA and older assays have unacceptably high false-positive rates. (4) Double-positive (MOG-IgG + AQP4-IgG) is extremely rare (<1%) and should prompt retesting — usually one is false positive.

6.3.4 Clinical Phenotypes

MOGAD Clinical Phenotypes by Age
Phenotype	Age Group	Frequency	Key Features
ADEM (Acute Disseminated Encephalomyelitis)	Children (<12 years)	Most common pediatric MOGAD phenotype (~50–70%)	Encephalopathy + multifocal neurological deficits + large fluffy bilateral brain lesions. Often post-infectious/post-vaccination. MOG-IgG positive in ~40–60% of pediatric ADEM. Usually monophasic with good recovery.
Optic Neuritis	Adults (most common adult phenotype)	~50–70% of adult MOGAD	Bilateral ON more common than MS (simultaneous or sequential). Anterior segment; disc swelling/papillitis prominent (vs retrobulbar in MS). Generally good visual recovery but prone to relapse. Long segment ON on MRI.
Myelitis	Both	~25–30%	LETM similar to NMOSD (≥3 segments) but often involves conus medullaris/lower cord (vs thoracic in NMOSD). Central cord. May have "H-sign" on axial. Generally better motor recovery than NMOSD myelitis.
Cortical Encephalitis	Both (more adults)	~5–15%	Unique to MOGAD — seizures, headache, fever, cortical FLAIR signal abnormality (unilateral or bilateral). May mimic HSV encephalitis or autoimmune encephalitis. CSF pleocytosis. EEG: focal slowing/epileptiform.
Brainstem syndrome	Both	~10–15%	Diplopia, ataxia, cranial neuropathies. Periependymal brainstem lesions. May overlap with area postrema involvement.
NMOSD phenotype	Adults	Variable	Meets IPND 2015 criteria for AQP4-negative NMOSD; important to test MOG-IgG in all AQP4-negative NMOSD patients

6.3.5 MRI Patterns in MOGAD

MOGAD MRI Characteristics
Region	Pattern	Distinction from MS/NMOSD
Brain	Large, fluffy, ill-defined bilateral white matter lesions (ADEM-like); deep gray matter involvement (thalami, basal ganglia) in children; cortical FLAIR signal (cortical encephalitis)	More ADEM-like than MS; no Dawson fingers; no PRL; cortical encephalitis unique to MOGAD
Optic nerve	Long segment involvement, anterior predominant, bilateral, perineural enhancement ("optic nerve sheath" sign), optic disc swelling on fundoscopy	MS: retrobulbar, unilateral, shorter; NMOSD: posterior/chiasmal, long; MOGAD: anterior/long, bilateral, perineural
Spinal cord	LETM (≥3 segments), central cord, conus medullaris involvement characteristic; may show "H-sign"	NMOSD: thoracic LETM, upper cord; MOGAD: lower cord/conus; MS: short segment, dorsolateral
Leptomeningeal	Leptomeningeal enhancement in some cases	Not typical of MS or NMOSD

6.3.6 Treatment

A. Acute Attack Treatment

MOGAD Acute Treatment
Line	Treatment	Notes
1st line	IV Methylprednisolone 1 g/day × 3–5 days → oral taper (prednisone, slow taper over 3–6 months)	Responds well to steroids (generally better than MS/NMOSD). Slow taper critical — rapid steroid withdrawal associated with early relapse in MOGAD.
2nd line	IVIG 0.4 g/kg/day × 5 days	Effective in steroid-refractory cases; some advocate as first-line adjunct in severe attacks
3rd line	PLEX 5–7 exchanges	Less evidence than in NMOSD; may be considered for severe myelitis

Clinical Pearl — Steroid-Dependent Relapses in MOGAD: A hallmark of MOGAD is steroid dependence — patients relapse when oral steroids are tapered too quickly. Unlike MS (where steroid tapers are brief), MOGAD often requires slow oral prednisone taper over 3–6 months after acute attack. If relapse occurs during taper, this strongly suggests MOGAD (rather than MS) and should prompt MOG-IgG testing and consideration of maintenance immunotherapy.

B. Preventive (Maintenance) Therapy

Not all MOGAD patients need long-term prevention — ~50% have monophasic disease. Prevention is recommended for relapsing MOGAD (≥2 attacks) or severe first attack with poor recovery.

MOGAD Preventive Therapies
Drug	Mechanism	Dose	Evidence Level	Notes
IVIG (maintenance)	Immunomodulation, anti-idiotype antibodies	0.4 g/kg monthly or 1–2 g/kg q1–3 months	Retrospective series; most consistent efficacy data	Considered first-line prevention for relapsing MOGAD by many experts. Well-tolerated. Cost may be limiting.
Azathioprine	Purine synthesis inhibitor	2–3 mg/kg/day	Retrospective	Traditional immunosuppressant; onset 3–6 months; bridge with oral prednisone
Mycophenolate mofetil	IMPDH inhibitor	2000–3000 mg/day	Retrospective	Alternative to AZA; teratogenic
Rituximab	Anti-CD20	Standard NMOSD dosing	Retrospective; less effective in MOGAD than NMOSD	Breakthrough relapses reported on rituximab in MOGAD — MOG-IgG may be produced by CD20-negative long-lived plasma cells. Consider if IVIG fails or unavailable.
Tocilizumab	Anti-IL-6R	8 mg/kg IV q4wk or 162 mg SC weekly	Case series	Emerging option for refractory MOGAD
Low-dose oral prednisolone	Broad immunosuppression	5–10 mg/day	Retrospective	May be used as bridge or adjunct; concern for long-term steroid side effects

High-Yield: Why Rituximab May Fail in MOGAD

Unlike NMOSD (where rituximab is highly effective), MOGAD shows higher breakthrough rates on rituximab. The proposed explanation: MOG-IgG may be partly produced by long-lived plasma cells and plasmablasts that are CD20-negative (rituximab depletes CD20+ B-cells but spares CD20− plasma cells). This contrasts with AQP4-IgG in NMOSD, which appears more dependent on CD20+ B-cell renewal. This is why IVIG is often preferred for MOGAD prevention — it modulates the immune response through multiple mechanisms rather than relying on B-cell depletion alone.

6.3.7 Prognosis

MOGAD Prognosis
Feature	Details
Overall prognosis	Better than NMOSD for individual attacks (better recovery); comparable or milder than MS overall
Monophasic vs relapsing	~50% monophasic (especially pediatric ADEM); ~50% relapsing (especially adult ON/myelitis). Persistent MOG-IgG seropositivity predicts relapsing course.
Visual outcomes	Better than NMOSD; most patients recover useful vision after ON (≥20/40 in majority). However, recurrent ON can cause cumulative damage.
Motor outcomes	Better recovery from myelitis than NMOSD; ambulation usually preserved
Cognitive outcomes	ADEM phenotype: usually full cognitive recovery in children. Cortical encephalitis: may have residual epilepsy.
MOG-IgG seroconversion	Patients who seroconvert to negative have lower relapse risk; those who remain persistently seropositive are more likely to relapse
Mortality	Rare; lower than NMOSD. Deaths reported with fulminant ADEM or severe brainstem involvement.

Question: A 7-year-old boy presents with fever, encephalopathy, and multifocal neurological deficits 2 weeks after a viral URTI. MRI brain shows large bilateral fluffy white matter lesions with deep gray matter involvement. MOG-IgG is positive. AQP4-IgG is negative. CSF shows lymphocytic pleocytosis. What is the diagnosis, and how does MOG-IgG positivity change management?

Answer:

Diagnosis: MOGAD presenting as ADEM. This is the most common MOGAD phenotype in children — post-infectious encephalopathy with large fluffy brain lesions + MOG-IgG positive.

Acute treatment:

IVMP 30 mg/kg/day (max 1g) × 3–5 days → slow oral steroid taper over 3–6 months (critical — rapid withdrawal risks relapse)
IVIG 2 g/kg over 2–5 days if steroid-refractory

How MOG-IgG changes management:

Prognosis: MOG+ ADEM generally has good recovery (~80–90% near-complete). But ~20–30% may have recurrent attacks (multiphasic ADEM or relapsing MOGAD).
Steroid taper: Slow taper is essential — steroid-dependent relapses are characteristic of MOGAD.
Follow-up: Monitor for relapse; recheck MOG-IgG at 6–12 months — seroconversion to negative suggests lower relapse risk.
NOT MS: Despite multifocal brain lesions, this is NOT pediatric MS — MOG-IgG positivity excludes MS. Do not start MS DMTs (IFN-β, natalizumab, etc.).
If relapsing: Consider maintenance IVIG or AZA/MMF for prevention.

6.4 Autoimmune Encephalitis (AE)

6.4.1 Overview & Classification

Autoimmune encephalitis encompasses a group of inflammatory brain diseases mediated by antibodies against neuronal cell-surface or synaptic proteins. Recognition has dramatically increased since the discovery of anti-NMDAR encephalitis (Dalmau 2007). AE is now considered as common as infectious encephalitis and is a treatable cause of rapidly progressive encephalopathy.

Classification by Antibody Target

Autoimmune Encephalitis Classification
Category	Target Location	Mechanism	Examples	Prognosis
Cell-surface / Synaptic antibodies	Extracellular domain of neuronal surface proteins	Antibody-mediated: receptor internalization, complement activation, or blocking of receptor function → potentially reversible with immunotherapy	Anti-NMDAR, anti-LGI1, anti-CASPR2, anti-GABABR, anti-AMPAR, anti-DPPX, anti-IgLON5	Generally good if treated early; often reversible
Intracellular / Classical paraneoplastic antibodies	Intracellular antigens (onconeural)	T-cell mediated: cytotoxic T-cells → neuronal death → often irreversible. Antibodies are biomarkers, not directly pathogenic.	Anti-Hu (ANNA-1), anti-Yo (PCA-1), anti-Ri (ANNA-2), anti-CV2/CRMP5, anti-amphiphysin, anti-Ma2	Generally poor; limited response to immunotherapy; tumor treatment is priority

High-Yield: Cell-Surface vs Intracellular Antibodies

Cell-surface antibodies (NMDAR, LGI1, CASPR2, GABABR): directly pathogenic, cause functional disruption (receptor internalization/blocking), damage is potentially reversible → responds to immunotherapy.
Intracellular antibodies (Hu, Yo, Ri, CV2): markers of T-cell cytotoxicity, not directly pathogenic themselves, damage is structural/neuronal death → irreversible → priority is tumor removal, immunotherapy has limited CNS benefit.

This distinction has critical treatment implications: aggressive immunotherapy is warranted and effective for cell-surface antibodies but has limited benefit for intracellular antibodies (where the focus should be cancer treatment).

6.4.2 Diagnostic Criteria (Graus 2016)

Graus et al., Lancet Neurol 2016: Clinical approach to diagnosis of autoimmune encephalitis. Provides criteria for possible AE (clinical), probable AE (antibody-specific), and definite AE.

Possible Autoimmune Encephalitis (Clinical Criteria)

All three must be met:

Subacute onset (rapid progression in <3 months) of working memory deficits, altered mental status, or psychiatric symptoms
At least one of:
- New focal CNS findings
- Seizures not explained by prior epilepsy
- CSF pleocytosis (WBC >5/μL)
- MRI features suggestive of encephalitis (T2/FLAIR hyperintensity in medial temporal lobes or multifocal involving gray/white matter)
Reasonable exclusion of alternative causes (infection, metabolic, neoplastic, other autoimmune)

Clinical Pearl — "Possible AE" Triggers Workup: Meeting "possible AE" criteria should immediately trigger a comprehensive antibody panel (serum + CSF), tumor screening, and consideration of empiric immunotherapy while awaiting results. Do NOT wait for antibody results before starting treatment in clinically suspicious cases — delays worsen outcomes, especially in anti-NMDAR encephalitis.

6.4.3 Antibody-Specific Syndromes

Anti-NMDA Receptor Encephalitis

Anti-NMDAR Encephalitis
Feature	Details
Epidemiology	Most common AE; predominantly young women (F:M ~4:1); median age ~21 years; also in children and males
Tumor association	Ovarian teratoma in ~40–50% of females aged 12–45 (contains neural tissue expressing NMDAR). Less common in children (<5%) and males (<5%). Always screen with pelvic MRI/US.
Clinical stages	Prodromal (1–2 weeks): fever, headache, viral-like illness Psychiatric: anxiety, agitation, psychosis, hallucinations, bizarre behavior, insomnia — often misdiagnosed as primary psychiatric illness Neurological: seizures, memory loss, decreased consciousness, dyskinesias (orofacial), autonomic instability (tachy/bradycardia, hypoventilation, hyperthermia) Hypoventilation/catatonia: may require ICU/ventilation — central hypoventilation is characteristic and dangerous Recovery: slow (months), reverse order of symptom development
MRI	Normal in ~50%! When abnormal: non-specific T2/FLAIR in cortical, subcortical, or medial temporal regions. May see transient meningeal enhancement.
EEG	Extreme delta brush (rhythmic delta with superimposed beta, present in ~30%) — relatively specific pattern. Also: diffuse slowing, epileptiform discharges.
CSF	Lymphocytic pleocytosis (~80%), elevated protein (~30%), CSF NMDAR-Ab more sensitive than serum (always test CSF). OCBs may develop.
Prognosis	~80% good outcome (mRS 0–2) with immunotherapy + tumor removal. Recovery slow (months to >1 year). ~12% relapse. Mortality ~5%.

Anti-LGI1 Encephalitis (Leucine-rich Glioma-Inactivated 1)

Anti-LGI1 Encephalitis
Feature	Details
Epidemiology	Older adults (median ~60 years); M:F ~2:1 (male predominance unlike most AE)
Tumor association	Rare (<10%); thymoma in some cases
Clinical triad	Faciobrachial dystonic seizures (FBDS): brief (<3 seconds), frequent (up to 100/day), unilateral face + ipsilateral arm tonic posturing. Pathognomonic for LGI1. Often precedes encephalitis — recognizing FBDS early can prevent progression. Limbic encephalitis: memory loss, confusion, temporal lobe seizures, psychiatric symptoms Hyponatremia: present in ~60% due to SIADH (LGI1 expressed in hypothalamus/kidney)
MRI	T2/FLAIR hyperintensity in medial temporal lobes (uni- or bilateral); basal ganglia involvement with FBDS. Late: mesial temporal sclerosis/hippocampal atrophy.
EEG	Temporal epileptiform discharges; FBDS may not have clear EEG correlate (subcortical origin)
CSF	Often normal or minimal pleocytosis; serum Ab usually more sensitive than CSF for LGI1
Treatment response	Good response to immunotherapy; FBDS respond dramatically to corticosteroids (often within days). AEDs alone typically ineffective for FBDS.
Prognosis	Generally good with treatment; residual memory deficit common; late hippocampal atrophy → epilepsy

Anti-CASPR2 Encephalitis (Contactin-Associated Protein-like 2)

Anti-CASPR2 Encephalitis
Feature	Details
Epidemiology	Older males (median ~60 years); M:F ~9:1
Tumor association	Thymoma in ~20–30%
Clinical features	Morvan syndrome: peripheral nerve hyperexcitability (neuromyotonia, cramps, fasciculations) + limbic encephalitis (insomnia, confusion, hallucinations) + autonomic dysfunction (hyperhidrosis, tachycardia) Limbic encephalitis (similar to LGI1 but less common hyponatremia) Neuromyotonia / Isaac syndrome: peripheral nerve hyperexcitability alone (cramps, stiffness, myokymia) Neuropathic pain, cerebellar ataxia possible
CSF	Variable; may be normal. Serum Ab usually sufficient.
Prognosis	Variable; tumor removal essential if thymoma present. Generally responds to immunotherapy.

Other Antibody-Specific Syndromes

Other Autoimmune Encephalitis Antibodies
Antibody	Key Syndrome	Tumor Association	Distinguishing Features
Anti-GABA_BR	Limbic encephalitis with prominent seizures	SCLC (~50%)	Seizures often the presenting and dominant feature; temporal lobe predominant. Responds to immunotherapy + tumor treatment.
Anti-AMPAR	Limbic encephalitis; psychiatric symptoms prominent	Lung, breast, thymoma (~65%)	Relapsing course common; high tumor association. Test both GluA1 and GluA2 subunits.
Anti-DPPX	Encephalitis + GI dysmotility (severe diarrhea, weight loss precede neurological symptoms)	B-cell neoplasms (rare)	Prodromal severe diarrhea → encephalopathy, hyperekplexia, myoclonus, cognitive decline
Anti-IgLON5	Sleep disorder (parasomnia, OSA, stridor) + progressive supranuclear palsy-like syndrome + bulbar dysfunction	None	Unique: tauopathy on pathology (resembles neurodegenerative disease). HLA-DRB1*10:01 strongly associated. Chronic course. Poor response to immunotherapy in advanced disease.
Anti-GAD65	Stiff-person syndrome, cerebellar ataxia, limbic encephalitis, epilepsy	Rare (thymoma); strong association with type 1 diabetes, autoimmune thyroid	Intracellular target but high titers (>2000 IU/mL) associated with neurological syndromes. Low titers are non-specific (common in T1DM). Response to immunotherapy: variable (GAD65 is intracellular → T-cell mediated component).

Classical Paraneoplastic Antibodies (Intracellular)

Classical Paraneoplastic (Intracellular) Antibodies
Antibody	Syndrome	Cancer	Prognosis
Anti-Hu (ANNA-1)	Sensory neuropathy, limbic encephalitis, brainstem encephalitis, autonomic neuropathy	SCLC (most common)	Poor; limited immunotherapy response; cancer treatment priority
Anti-Yo (PCA-1)	Cerebellar degeneration — subacute progressive ataxia	Ovarian, breast	Poor; Purkinje cell destruction irreversible
Anti-Ri (ANNA-2)	Opsoclonus-myoclonus, brainstem encephalitis	Breast, SCLC	Variable; some improvement with tumor treatment
Anti-CV2/CRMP5	Mixed: neuropathy, chorea, cerebellar ataxia, optic neuritis, uveitis	SCLC, thymoma	Variable
Anti-amphiphysin	Stiff-person syndrome, myelopathy	Breast, SCLC	Variable
Anti-Ma2 (Ta)	Limbic/diencephalic encephalitis: hypersomnia, vertical gaze palsy, hypokinesis	Testicular germ cell tumor (young men)	Better with orchiectomy + immunotherapy

Clinical Pearl — Tumor Screening in AE: Always perform comprehensive tumor screening based on antibody type: (1) Anti-NMDAR → pelvic MRI/US (ovarian teratoma); CT chest/abdomen/pelvis. (2) Anti-LGI1 → CT chest (thymoma, rare). (3) Anti-CASPR2 → CT chest (thymoma ~20%). (4) Anti-GABABR → CT chest (SCLC ~50%). (5) Anti-Hu → CT chest (SCLC). (6) Anti-Yo → CT/MRI pelvis + mammography (ovarian/breast). (7) Anti-Ma2 in young men → testicular US. If initial screen negative, repeat at 6 months and consider whole-body PET-CT — tumor may be occult.

6.4.4 Treatment Algorithm

AE Treatment — Stepwise Approach
Line	Treatment	Details
First-line immunotherapy	IV Methylprednisolone 1 g/day × 3–5 days IVIG 0.4 g/kg/day × 5 days PLEX 5–7 exchanges Combinations used: IVMP + IVIG or IVMP + PLEX	Start as soon as "possible AE" criteria met — do NOT wait for antibody results. PLEX particularly effective for cell-surface antibody syndromes. Assess response at 2–4 weeks.
Second-line immunotherapy (if insufficient first-line response by 2–4 weeks)	Rituximab 375 mg/m² × 4 weekly or 1000 mg × 2 (days 0, 14) Cyclophosphamide 750 mg/m² monthly × 6	Rituximab preferred for anti-NMDAR and other cell-surface Ab syndromes. Cyclophosphamide for severe/refractory cases. Do not delay second-line if first-line fails — outcomes correlate with treatment intensity and speed.
Tumor removal	Remove underlying tumor as soon as identified	Essential for anti-NMDAR (teratoma removal → faster recovery), anti-GABABR/AMPAR/Hu/Yo (cancer treatment paramount). Tumor removal alone may be insufficient — combine with immunotherapy.
Maintenance immunotherapy (prevent relapse)	MMF 1000–3000 mg/day Azathioprine 2–3 mg/kg/day Rituximab q6mo (for relapsing anti-NMDAR) Chronic IVIG monthly (selected cases)	Duration: ≥2 years minimum; some require indefinite. Monitor antibody titers — declining titers correlate with clinical improvement. Relapse rates: ~12% for anti-NMDAR, higher for AMPAR.
Emerging therapies	Bortezomib (proteasome inhibitor → plasma cell depletion) Tocilizumab (anti-IL-6R) Low-dose IL-2 (Treg expansion)	For refractory cases resistant to rituximab. Bortezomib targets antibody-secreting plasma cells not depleted by rituximab. Case series show benefit in refractory anti-NMDAR encephalitis.

Question: A 22-year-old woman develops new-onset psychosis, agitation, and seizures over 2 weeks. She was seen in psychiatry initially and started on antipsychotics without improvement. She now develops orofacial dyskinesias and decreased consciousness. What is the most likely diagnosis, and what immediate workup and treatment are needed?

Answer:

Most likely diagnosis: Anti-NMDA receptor encephalitis. The clinical progression — psychiatric symptoms → seizures → movement disorder (orofacial dyskinesias) → decreased consciousness — is the classic staged presentation. Young woman + psychiatric → neurological = anti-NMDAR until proven otherwise.

Immediate workup:

CSF: Anti-NMDAR antibodies (CSF more sensitive than serum); cell count, protein, glucose, OCBs, viral PCR (exclude HSV)
Serum: Anti-NMDAR antibodies, comprehensive AE panel
MRI brain: May be normal in ~50%; look for temporal/cortical FLAIR signal
EEG: Diffuse slowing; look for extreme delta brush; exclude status epilepticus
Pelvic MRI/US: Screen for ovarian teratoma
CT chest/abdomen/pelvis: Tumor screening

Immediate treatment (do NOT wait for antibody results):

First-line: IVMP 1 g × 5 days + IVIG 0.4 g/kg × 5 days (start concurrently)
ICU admission: Monitor for autonomic instability, hypoventilation (central), status epilepticus
If teratoma found: Urgent surgical removal
If no/poor response by 2–4 weeks: Escalate to rituximab ± cyclophosphamide
Stop antipsychotics — neuroleptic sensitivity common; may worsen dyskinesias

6.5 Acute Disseminated Encephalomyelitis (ADEM)

6.5.1 Overview

ADEM is a monophasic inflammatory demyelinating disorder of the CNS, predominantly affecting children (peak age 5–8 years). It is characterized by encephalopathy (mandatory diagnostic criterion) plus multifocal neurological deficits, typically occurring 1–4 weeks after a viral infection or vaccination.

ADEM Key Features
Feature	Details
Definition	First episode of CNS demyelination with encephalopathy (altered consciousness or behavioral change beyond fever-related); multifocal neurological deficits; polyfocal MRI lesions
Age	Primarily children (median ~5–8 years); rare in adults (when occurs, tends to be more severe)
Trigger	Post-infectious (~70–80%): upper respiratory, GI viral illness; post-vaccination (rare, ~5%). Latency 1–4 weeks.
MOG-IgG	Positive in ~40–60% of pediatric ADEM — now classified as MOGAD if MOG-IgG+
Clinical features	Encephalopathy (required) + multifocal deficits: ataxia, hemiparesis, cranial neuropathies, optic neuritis, myelitis, seizures. Fever, headache, meningism common.
MRI	Large (>1–2 cm), bilateral, fluffy, poorly-demarcated T2/FLAIR lesions in white matter ± deep gray matter (thalami, basal ganglia). No periventricular Dawson fingers. May involve brainstem, cerebellum, spinal cord.
CSF	Lymphocytic pleocytosis (~50–80%), elevated protein; OCBs usually absent (if present, consider MS)
Course	Monophasic by definition. If relapse occurs → consider multiphasic ADEM (MDEM), MOGAD, or MS.

6.5.2 ADEM Treatment & Prognosis

ADEM Treatment
Treatment	Regimen	Notes
IVMP	20–30 mg/kg/day (max 1 g) × 3–5 days → oral prednisone taper over 4–6 weeks	First-line. Slow oral taper to prevent relapse (especially if MOG-IgG+).
IVIG	2 g/kg over 2–5 days	Second-line or adjunct if steroid-refractory
PLEX	5–7 exchanges	For severe steroid- and IVIG-refractory cases

ADEM Prognosis
Outcome	Details
Recovery	Good — ~60–80% full recovery; ~20–30% mild residual deficits (behavioral, cognitive, motor)
Mortality	~1–5% (fulminant cases: acute hemorrhagic leukoencephalitis / Hurst disease)
Relapse	If new event >3 months after initial: reconsider as MS, MOGAD, or MDEM
Distinction from MS	ADEM: encephalopathy + large fluffy lesions + OCB− + monophasic; MS: no encephalopathy + Dawson fingers + OCB+ + relapsing. In children with ADEM, if >2 non-ADEM events → likely MS.

6.6 Differential Diagnosis: MS vs NMOSD vs MOGAD

6.6.1 Master Comparison Table

Comprehensive Comparison: MS vs NMOSD vs MOGAD
Feature	MS	NMOSD (AQP4+)	MOGAD
Target	Myelin/oligodendrocyte (T/B-cell mediated)	AQP4 on astrocyte foot processes	MOG on oligodendrocyte surface
Antibody	None specific (OCBs = polyclonal)	AQP4-IgG	MOG-IgG
Peak age	20–40 years	~40 years	Bimodal: children (~5–7) + adults (~30–40)
Sex ratio (F:M)	3:1	9:1	~1–2:1
Ethnicity	Northern European predominant	Non-White (African, Asian, Latin American)	All ethnicities
Clinical Features
Optic neuritis	Unilateral, retrobulbar, mild–moderate, good recovery	Severe, bilateral, chiasmal/posterior, poor recovery	Bilateral, anterior (papillitis), long segment, good recovery
Myelitis	Short segment (<3 vertebral segments), partial, asymmetric, dorsolateral	LETM ≥3 segments, complete, central cord, thoracic	LETM, central, conus/lower cord, good recovery
Area postrema	Not typical	Characteristic (intractable N/V/hiccups)	Rare
Brain involvement	Dawson fingers, periventricular, juxtacortical	Periependymal, diencephalic, non-specific or normal	ADEM-like fluffy, cortical encephalitis
Seizures	Uncommon	Rare	Common (cortical encephalitis phenotype)
Encephalopathy	Not typical	Rare	Common (ADEM, cortical encephalitis)
Attack severity	Mild–moderate	Severe, poor recovery	Moderate, good recovery
MRI Features
Brain lesions	Ovoid perpendicular periventricular (Dawson fingers), juxtacortical, infratentorial, small well-defined	Non-specific, periependymal (3rd/4th ventricle), area postrema, large hemispheric, or normal	Large fluffy bilateral (ADEM-like), deep gray matter, cortical FLAIR signal
Spinal cord	Short segment, dorsolateral, peripheral	LETM, central (H-sign), thoracic	LETM, central, conus medullaris
Optic nerve MRI	Short, anterior, unilateral	Long, posterior/chiasmal	Long, anterior, bilateral, perineural enhancement
CVS	~85% lesions CVS+	Low CVS (<40%)	Low CVS
PRL	Present (chronic active)	Absent	Absent
CSF & Lab
OCBs	Positive ~95%	Negative ~75–80%	Usually negative
Pleocytosis	Mild lymphocytic (<50)	Can be >50; neutrophil predominance	Mild–moderate; lymphocytic/mixed
GFAP	Mildly elevated	Markedly elevated (astrocyte destruction)	Mildly elevated
MRZ reaction	Positive ~67%	Negative	Negative
Disease Course & Treatment
Course	Relapsing → progressive; continuous disease	Relapsing (~90%); stepwise disability; NO progression between attacks	~50% monophasic, ~50% relapsing
Prevention	MS DMTs (IFN-β, anti-CD20, S1P modulators, etc.)	AZA, MMF, RTX, eculizumab, satralizumab, inebilizumab. MS DMTs harmful!	IVIG, AZA, MMF, ± RTX (less effective)
Prognosis	Variable; 50% SPMS by 15–20 years	Poor per attack; cumulative disability; mortality ~5–10% at 5 years without treatment	Better overall; good recovery per attack

High-Yield: Quick Diagnostic Clues

Think MS: Young woman + Dawson fingers + short cord lesions + OCBs+ + CVS+ + PRL+
Think NMOSD: Middle-aged woman + LETM + severe bilateral ON + area postrema (intractable vomiting) + AQP4-IgG+ + OCBs−
Think MOGAD: Child with ADEM or adult with bilateral ON + papillitis + conus myelitis + MOG-IgG+ + good recovery + steroid-dependent relapses

6.6.2 Other CNS Inflammatory / Demyelinating Differentials

Important Differential Diagnoses
Condition	Key Distinguishing Features
Neurosarcoidosis	Cranial neuropathies (especially VII), hypothalamic/pituitary involvement, leptomeningeal enhancement, hilar lymphadenopathy, elevated ACE, non-caseating granulomas
CNS vasculitis (PACNS)	Headache, stroke-like episodes, multifocal infarcts, vessel beading on angiography, brain biopsy may be needed
Behçet disease	Oral/genital ulcers, uveitis, brainstem/diencephalic lesions, CSF neutrophilic pleocytosis, pathergy test
Susac syndrome	Triad: encephalopathy + branch retinal artery occlusions (BRAO) + sensorineural hearing loss. Corpus callosum "snowball" lesions. Young women.
CNS lymphoma	Homogeneously enhancing periventricular mass; restricted diffusion; older age or immunocompromised; CSF cytology/flow cytometry
Neurosyphilis	Positive treponemal tests; CSF VDRL; meningitis, tabes dorsalis, general paresis; consider in all unexplained CNS inflammation
Neuroborreliosis (Lyme)	Cranial neuropathies (VII bilateral), radiculitis, lymphocytic meningitis; endemic area exposure; Borrelia serology + CSF index
CADASIL	Migraine with aura, subcortical infarcts, anterior temporal pole + external capsule white matter lesions, family history, NOTCH3 mutation
Leukodystrophies	Symmetrical white matter changes; progressive course; metabolic markers (very long-chain fatty acids for adrenoleukodystrophy, arylsulfatase A for metachromatic)
CLIPPERS	Chronic lymphocytic inflammation with pontine perivascular enhancement — "peppering" punctate Gd-enhancing lesions in pons/brainstem; steroid-responsive

6.7 Key References & Guidelines

Section 6 — Key References
Topic	Reference
McDonald 2017 Criteria	Thompson AJ, et al. Lancet Neurol 2018;17:162–73
McDonald 2024 Criteria	Revision Committee. Lancet Neurol 2025 (in press)
MS Comprehensive Review	Filippi M, et al. Lancet 2024 Seminar
EBV & MS	Bjornevik K, et al. Science 2022;375:296–301
NMOSD Diagnostic Criteria (IPND 2015)	Wingerchuk DM, et al. Neurology 2015;85:177–89
NMOSD Comprehensive Review	Autoimmunity Reviews 2023
NEMOS Diagnostic Recommendations	J Neurol 2023
MOGAD Diagnostic Criteria	Banwell B, et al. Lancet Neurol 2023;22:268–82
Autoimmune Encephalitis Criteria	Graus F, et al. Lancet Neurol 2016;15:391–404
Anti-NMDAR Encephalitis	Dalmau J, et al. Lancet Neurol 2019;18:1045–57
PREVENT Trial (Eculizumab in NMOSD)	Pittock SJ, et al. NEJM 2019;381:614–25
SAkuraSky Trial (Satralizumab)	Yamamura T, et al. NEJM 2019;381:2114–24
N-MOmentum Trial (Inebilizumab)	Cree BAC, et al. Lancet 2019;394:1352–63
OPERA I/II Trials (Ocrelizumab)	Hauser SL, et al. NEJM 2017;376:221–34
ORATORIO Trial (Ocrelizumab PPMS)	Montalban X, et al. NEJM 2017;376:209–20
CNS Demyelinating Diseases — Lecture	Jitprapaikulsan J. CNS Demyelinating Diseases for Medicine Residents. SiNiC.
McDonald 2024 Updates — Lecture	Ongphichetmetha T. Diagnostic Criteria for MS: McDonald 2024.

7. CNS Infections

This section provides a comprehensive subspecialist-depth review of CNS infections relevant to Internal Medicine and Neurology practice. Coverage includes acute bacterial meningitis (Thai-specific empirical regimens, ESCMID/IDSA guidelines, organism-specific therapy, adjunctive dexamethasone — Cochrane 2015), viral CNS infections (HSV encephalitis, VZV, CMV, JE, rabies, HIV-associated), tuberculous meningitis (Thwaites trial, BIS guidelines, BMRC staging), fungal CNS infections (cryptococcal meningitis — AMBITION trial/WHO 2022, aspergillosis, mucormycosis), parasitic infections (cerebral toxoplasmosis, NCC, eosinophilic meningitis from Angiostrongylus/Gnathostoma, cerebral malaria), immunocompromised host approach, and neuroimaging patterns.

7.1 Bacterial Meningitis

7.1.1 Overview & Epidemiology

Acute bacterial meningitis (ABM) is a medical emergency with an incidence of 0.9–80 per 100,000/year globally and an overall mortality of ~54%, with neurological complications in ~25% of survivors (JAMA 2022). Prompt recognition and treatment within 60 minutes of arrival is critical (ESCMID 2016).

Thai Epidemiology (Ramathibodi data, Aimbudlop et al.): Among Thai adults with meningitis: C. neoformans 37%, Bacteria 31.5%, M. tuberculosis 27%, Virus 4.5%. HIV-positive patients account for ~30% of all meningitis cases. Thammasat data (Neurology Asia 2020): bacterial 61%, viral 15%, TB 12%, crypto 13%.

Common Pathogens by Age & Risk Group

Age / Risk Group	Common Pathogens	Empirical Therapy (ESCMID/Lancet 2021)
<1 month	S. agalactiae, E. coli, Listeria	Amoxicillin/ampicillin + 3rd-gen cephalosporin; or ampicillin + aminoglycoside
1–23 months	S. agalactiae, S. pneumoniae, N. meningitidis	Vancomycin + 3rd-gen cephalosporin (cefotaxime or ceftriaxone)
2–50 years	S. pneumoniae, N. meningitidis	Vancomycin + 3rd-gen cephalosporin
>50 years	S. pneumoniae, N. meningitidis, L. monocytogenes, aerobic GNR	Vancomycin + ampicillin + 3rd-gen cephalosporin
Immunocompromised	S. pneumoniae, N. meningitidis, L. monocytogenes, S. aureus, Salmonella spp., Pseudomonas	Vancomycin + ampicillin + cefepime or meropenem

Thai-Specific Empirical Regimen (Siriraj data):
• Age <50y: Ceftriaxone 2g IV q12h (covers N. meningitidis, S. pneumoniae, S. suis)
• Age >50y / pregnancy / alcoholism / steroids: Add Ampicillin 2g IV q4h (covers S. agalactiae, L. monocytogenes, GNR)
• No vancomycin needed empirically in Thailand — drug-resistant S. pneumoniae rate <1% (NARST data 2022: vancomycin resistance 0%). Siriraj organism distribution: S. agalactiae > S. suis > S. pneumoniae (differs from Western patterns where S. pneumoniae predominates at ~72%).

Meningeal Dose Antibiotics

Drug	Meningeal Dose
Vancomycin	30–60 mg/kg/day (target trough 15–20 µg/mL)
Ceftriaxone	4 g/day (2g q12h)
Cefotaxime	8–12 g/day
Cefepime	6 g/day
Ampicillin	12 g/day (2g q4h)
Penicillin G	24 million units/day
Meropenem	6 g/day (2g q8h)

7.1.2 Clinical Presentation & Diagnosis

Classic Triad & Sensitivity

The classic triad of fever, neck stiffness, and altered mental status is present in only 41% of adults with ABM (JAMA 2022). However, >90% will have at least 2 of the 4 symptoms: fever, headache, decreased consciousness, or stiff neck (Seminars in Neurology 2019). Only ~30% of elderly/immunocompromised patients exhibit neck stiffness.

Clinical Sign	Sensitivity	Specificity	PPV	NPV
Neck stiffness	31%	71%	41%	61%
Kernig’s sign	11%	95%	60%	60%
Brudzinski’s sign	9%	95%	50%	62%

Combined data from Thomas (n=297), Uchihara (n=54), Waghdhare (n=190) — Brouwer et al. Lancet 2012;380:1684–92

CT Brain Before LP — Indications

Indications for CT Before LP (IDSA 2004 / NEJM 2001)

Age >60 years
Immunocompromised state
Known CNS lesion
Seizure within 1 week
Abnormal level of consciousness
Focal neurologic findings
Papilledema / clinical suspicion of elevated ICP

ESCMID 2016 (stricter, 4 indications): GCS <10, focal neurological deficit, new-onset seizure, severe immunocompromise. Of note, 97% of patients without these indications have a normal CT (Hasbun et al. NEJM 2001).

Clinical Pearl — Do NOT delay antibiotics for CT: Start empirical antibiotics + dexamethasone BEFORE CT/LP if imaging is needed. Delay of ATB >6 hours is associated with increased mortality from 6% to 45% and increased neurological sequelae from 10% to 70% (JAMA 2022). ESCMID 2016: initiate within 60 minutes of arrival. If no improvement within 48 hours, brain imaging is indicated to detect hydrocephalus, infarction, empyema, or abscess.

7.1.3 CSF Analysis & Interpretation

CSF Parameter	Normal	Bacterial	Viral	TB	Fungal	Parasitic	Carcinomatous
Opening Pressure (cmH₂O)	10–20	High	Normal–high	High	Very high	Usually high	Normal–high
Colour	Clear	Cloudy	Clear	Clear–yellowish	Clear–cloudy	Clear	Clear
Cells/mm³	<5	100–50,000	5–500	100–500	20–500	Variable	Variable
Differential	Mono	PMN	Mono	Lymph (N early)	Lymph	Eos >10%	Mixed/Mono
CSF Glucose / PG ratio	Normal (60%)	Very low	Normal	<45 mg/dL (80%)	Normal–low	Low	Low
Protein (mg/dL)	<45	>1000	50–100	100–5000	20–500	>60	100–500

CSF Interpretation Pitfalls

Traumatic LP correction: Subtract 1 WBC per 500–1000 RBCs; subtract protein 1 mg/dL per 1000 RBCs.

Partially treated bacterial meningitis: Normal glucose in 70%, lymphocyte-predominant in 15%, normal protein in 10%, but normal cell count in 0%. CSF sterilization occurs within 2–4 hours of parenteral antibiotics.

Eosinophilic meningitis (>10% eos): Think parasites (Angiostrongylus cantonensis, Gnathostoma), TB, Coccidioides, lymphoma.

Microbiological Diagnosis

Test	Sensitivity	Notes
Gram stain	25–90%	Depends on organism load; S. pneumoniae highest Sn
CSF culture	60–90%	Drops to 20–30% with prior ATB; sterilization 2–4h
CSF PCR (multiplex)	89% D1–3; 70% D4–6; 33% D7–10	Less affected by pretreatment
CSF lactate	Sn 93%, Sp 96%	Best discriminator for bacterial vs viral; >3.5 mmol/L suggests bacterial
Procalcitonin (serum)	Sn 90%, Sp 98%	Useful to differentiate bacterial from aseptic; >0.5 ng/mL

7.1.4 Organism-Specific Bacterial Meningitis

Streptococcus pneumoniae

S. pneumoniae is the most common cause of bacterial meningitis globally (~72% of adult cases). It is a common nasopharyngeal colonizer in 5–10% of healthy adults and 20–40% of children. Routes of CNS entry include hematogenous spread (50% associated with pneumonia), direct extension from otitis/sinusitis/mastoiditis, and post-traumatic CSF leak.

Risk factors: basilar skull fracture with CSF leak, hyposplenism, hypogammaglobulinemia, multiple myeloma, glucocorticoid use, DM, CKD, alcoholism, malnutrition, chronic liver disease.

Cerebrovascular complications are particularly common: arterial stroke in up to 30%, cerebral venous thrombosis in up to 9%, intracerebral hemorrhage in up to 9% of patients.

Mortality rate: 10–37% with neurological sequelae up to 24.7%. Therapy should NOT be withdrawn early in comatose patients with preserved brainstem reflexes (a quarter eventually recover fully).

Vaccination: All survivors should receive PCV13 or PCV15, followed by PPSV23 or PCV20, due to high recurrence risk.

Treatment: Penicillin-susceptible: Penicillin G or Ceftriaxone × 10–14 days. Penicillin-resistant (MIC ≥0.12): Ceftriaxone. Ceftriaxone-resistant (MIC ≥2): Vancomycin + Ceftriaxone ± Rifampicin.

Thai Context (NARST 2022, 68 hospitals): In Thailand, S. pneumoniae vancomycin resistance = 0%. Levofloxacin resistance 0–1.5%. Penicillin G non-susceptibility (oxacillin screen) ~38%. Therefore, ceftriaxone alone without vancomycin is appropriate for empirical therapy in Thailand. The ESCMID guideline also states that in areas with very low pneumococcal cephalosporin resistance, ceftriaxone alone is considered appropriate.

Neisseria meningitidis

Gram-negative diplococcus; nasopharyngeal carrier in healthy individuals. Causes 11% of adult meningitis (age >16y). Endemic in Africa, India, and developing areas. Risk factors: crowded living, chronic illness, asplenia, complement deficiency, corticosteroid use.

Distinctive features: Petechial/purpuric rash in 63–80% (Sp 83–92% for meningococcal disease). Waterhouse-Friderichsen syndrome (bilateral adrenal hemorrhage) in fulminant meningococcemia.

Mortality: Meningitis ~3–10%; meningococcemia ~30%.

Treatment: Penicillin G or Ceftriaxone × 7 days.

Chemoprophylaxis (close contacts): Rifampin 600mg PO q12h × 2 days, OR Ciprofloxacin 500–750mg PO single dose, OR Ceftriaxone 250mg IM single dose.

Listeria monocytogenes

Small gram-positive bacillus; causes ~5% of bacterial meningitis in adults >16y. Environmental/food-borne (raw meat, vegetables, milk — isolated from 70% of these products). Mortality 15–35%.

Groups at risk: Pregnant women, infants, elderly (>60y), alcoholism, immunosuppressed, chronic liver/renal disease, DM, iron-overload conditions.

CNS manifestations:

Meningoencephalitis (hematogenous route, immunocompromised host)
Rhombencephalitis (brainstem encephalitis, oral route, immunocompetent host) — 1–24% of Listeria CNS infections
Brain abscess — ~10% of Listeria CNS infections; treat with Ampicillin ≥6 weeks ± surgical intervention

Clinical pearl: May present as “aseptic meningitis” (CSF lymphocyte-predominant). Listeria is intrinsically resistant to cephalosporins — always add Ampicillin in at-risk populations.

Treatment: Ampicillin ± Gentamicin × ≥21 days. Stop dexamethasone if Listeria confirmed (JAMA 2022).

Streptococcus suis

Zoonotic pathogen from pigs with highest prevalence in Asia (especially Thailand, Vietnam, China). Risk factor: exposure to pigs/pork (~61% of cases). Main clinical syndrome: subacute meningitis (68%), followed by sepsis, arthritis, endocarditis, endophthalmitis.

Male predominant (82%); mortality rate 2.9%. Major sequela: hearing loss (53%) and vestibular dysfunction.

Treatment: Penicillin G or Ceftriaxone × 14–21 days. Dexamethasone reduces severe hearing loss (PLOS NTD 2015).

Thai Pearl — S. suis: Think of S. suis in any Thai patient with meningitis + hearing loss + history of eating raw pork products (“larb moo” / “lab dib”). S. suis is the second most common bacterial meningitis organism at Siriraj Hospital.

Streptococcus agalactiae (Group B Streptococcus)

Most common cause of bacterial meningitis at Siriraj Hospital. Classically neonatal, but increasingly recognized in adults >50y, DM, pregnancy, immunosuppression.

Treatment: Penicillin G ± Gentamicin × 14–21 days.

Duration of Antibiotic Therapy by Organism

Organism	Duration (days)	Preferred Regimen
N. meningitidis	7	Penicillin G / Ceftriaxone
H. influenzae	7–10	Ampicillin / Ceftriaxone
S. pneumoniae	10–14	Penicillin G (PenS) / Ceftriaxone (PenR) / Vanco+Ceftriaxone (CeftriR)
S. suis	14–21	Penicillin G / Ceftriaxone
S. agalactiae (GBS)	14–21	Penicillin G ± Gentamicin
L. monocytogenes	≥21	Ampicillin ± Gentamicin
Enterobacterales / GNR	≥21	Ceftriaxone / Meropenem
Staphylococcus	Variable (usually ≥14)	Nafcillin (MSSA) / Vancomycin (MRSA)

7.1.5 Adjunctive Dexamethasone

Dexamethasone in Bacterial Meningitis

Dose: Dexamethasone 10 mg IV q6h × 4 days (0.15 mg/kg q6h). Must be given before or with first antibiotic dose (not after).

Evidence (Cochrane 2015, 25 RCTs, 4121 patients):

Hearing loss: RR 0.67 (13.8% vs 19.0%)
Neurological sequelae: RR 0.83 (17.9% vs 21.6%)
Mortality: RR 0.90
Benefits primarily in high-income countries and S. pneumoniae meningitis (mortality 29.9% vs 36.0%)
No beneficial effect in low-income countries
S. suis: dexamethasone decreases severe hearing loss

Stop dexamethasone if: Listeria monocytogenes is confirmed.

In the Netherlands, pneumococcal meningitis in-hospital mortality decreased from 31% to 17% between 1998–2002 and 2006–2018, possibly attributable to corticosteroid use (JAMA 2022).

7.1.6 Antibiotic BBB Penetration Pharmacology

Key principles for CNS antibiotic selection: bactericidal, small molecular weight, lipophilic, low protein binding, low efflux transporter affinity.

Penetration Category	Antibiotics	Clinical Relevance
Good CNS penetration (above MIC)	Fluoroquinolones, TMP-SMX, Metronidazole, Chloramphenicol, Linezolid	Reliable CNS levels; useful for targeted therapy
Adequate with inflamed meninges (close to MIC)	Penicillins, Cephalosporins, Meropenem	Meningeal doses needed; mainstay of empirical Rx
Poor CNS penetration (below MIC / toxic)	Aminoglycosides, Colistin, Vancomycin (variable)	May need intrathecal administration
Limited experience (below MIC)	β-lactam/β-lactamase inhibitor combinations	Avoid as sole CNS-directed therapy

7.1.7 Postoperative & Healthcare-Associated Meningitis

Types: post-craniotomy, VP/VA shunt infection, external ventricular drain (EVD) infection. Of these cases, 60–75% are aseptic (inflammatory reaction to blood products/tumor debris).

Risk factors: posterior fossa surgery, pediatric patients, longer operative time, lack of antibiotic prophylaxis, CSF leakage.

Key discriminator: CSF lactate >4 mmol/L best differentiates bacterial from aseptic postoperative meningitis (Sn 88–97%, Sp 78–98%).

Common organisms: S. aureus (including MRSA), coagulase-negative Staphylococci, Cutibacterium acnes, GNR including Pseudomonas, Acinetobacter.

Empirical treatment: Vancomycin + anti-pseudomonal β-lactam (cefepime, meropenem, or ceftazidime) ± intrathecal/intraventricular vancomycin or aminoglycoside for refractory cases. Hardware removal when feasible.

7.1.8 Brain Abscess

Brain abscess is a focal suppurative infection within the brain parenchyma, typically located at the gray-white matter junction. Three mechanisms: (1) contiguous spread from sinusitis/otitis/mastoiditis/dental (~40–50%), (2) hematogenous seeding from distant focus (~30%), (3) post-neurosurgical/traumatic (~10–20%).

Microbiology

Source	Common Organisms
Sinusitis / otitis / dental	Streptococci (viridans, anginosus group), anaerobes (Bacteroides, Fusobacterium, Prevotella)
Hematogenous (lung, endocarditis)	Staphylococci, Streptococci, polymicrobial
Post-surgical / trauma	S. aureus, Enterobacterales, Pseudomonas
Immunocompromised	Nocardia, Aspergillus, Toxoplasma, Listeria, Mycobacteria

Clinical Features & Diagnosis

Headache (70%), focal neurological deficits (50%), fever (50%), seizures (25–35%), nausea/vomiting, papilledema. Classic triad of headache + fever + focal deficit in only ~20%.

Imaging: CT: hypodense lesion with ring enhancement post-contrast. MRI: ring-enhancing lesion at gray-white junction; DWI restriction within abscess cavity is characteristic (differentiates from tumor). Hemorrhage possible.

LP is contraindicated in most cases of brain abscess due to risk of herniation.

Treatment

Medical therapy: Empirical: Ceftriaxone 2g IV q12h + Metronidazole 500mg IV q8h ± Vancomycin (if post-surgical or MRSA risk). Duration: 6–8 weeks IV, often followed by oral step-down.

Surgical intervention: Stereotactic aspiration (preferred for deep/eloquent lesions) or excision (for superficial/encapsulated abscesses). Surgery indicated for: abscess >2.5 cm, significant mass effect, posterior fossa location, failure to improve with antibiotics, need for microbiological diagnosis.

Corticosteroids: Only for significant mass effect/impending herniation; may impair capsule formation and reduce antibiotic penetration. Use for shortest duration possible.

Q: A 55-year-old Thai man presents with fever, headache, and hearing loss. He reports eating raw pork 2 weeks ago. CSF shows WBC 500 (85% PMN), glucose 20 mg/dL, protein 250 mg/dL. What is the most likely organism and optimal treatment?

Most likely organism: Streptococcus suis — subacute meningitis with hearing loss in a Thai patient with raw pork exposure is classic.
Treatment: Ceftriaxone 2g IV q12h × 14–21 days + Dexamethasone 10mg IV q6h × 4 days (reduces hearing loss). Penicillin G is an alternative.
Key points: S. suis is the #2 cause of bacterial meningitis in Thailand. Hearing loss is the most common sequela (53%). Vestibular dysfunction is also common.

Q: A 70-year-old immunocompetent woman presents with acute bacterial meningitis. CSF Gram stain shows gram-positive bacilli. Which antibiotic is essential and why should cephalosporins alone not be used?

Answer: Gram-positive bacilli in CSF suggest Listeria monocytogenes. Ampicillin is essential because Listeria is intrinsically resistant to all cephalosporins. The mechanism is lack of affinity for Listeria PBP3. Add Gentamicin for synergy. Duration ≥21 days. Stop dexamethasone if Listeria is confirmed. Risk factors include age >50, pregnancy, immunosuppression, and chronic liver/renal disease.

7.2 Viral CNS Infections

7.2.1 Viral (Aseptic) Meningitis

Viral meningitis is the most common cause of aseptic meningitis. Most common agents: Enteroviruses (echovirus, coxsackievirus — ~85% of cases), HSV-2, HIV, arboviruses, mumps. CSF shows lymphocytic pleocytosis (5–500 cells), normal glucose, mildly elevated protein (50–100 mg/dL). Generally self-limiting with full recovery.

Mollaret’s Meningitis: Recurrent benign lymphocytic meningitis caused by HSV-2. Episodes of meningitis resolving spontaneously within 2–5 days, with complete recovery between episodes. Diagnosis: CSF HSV-2 PCR positive during episodes. Prophylactic valacyclovir may reduce recurrence frequency.

Important: Acyclovir is NOT Beneficial for Viral Meningitis

Unlike HSV encephalitis (where acyclovir is life-saving), acyclovir has no proven benefit in viral meningitis even when caused by HSV-2. Treatment is supportive. Do not confuse viral meningitis with meningoencephalitis.

Aseptic Meningitis — Differential by CSF Predominant Cell Type

CSF Predominance	Differential Diagnosis
Neutrophilic	Partially treated bacterial meningitis, parameningeal infection (abscess, empyema), early viral (first 24h may be PMN-predominant)
Lymphocytic	Viral (enterovirus, HSV-2, HIV), rickettsial, early chronic meningitis (TB, fungal), drug-induced, autoimmune (SLE, sarcoidosis, Behçet), CNS lymphoma/carcinomatous
Eosinophilic (>10%)	Parasitic (Angiostrongylus cantonensis, Gnathostoma spinigerum), TB, Coccidioides, drug reactions, CNS lymphoma

7.2.2 Herpes Simplex Encephalitis (HSE)

HSV-1 encephalitis is the most common cause of sporadic fatal encephalitis worldwide. Mortality untreated: 70%; with acyclovir: 15–20%. Occurs via reactivation of latent virus in trigeminal ganglion or primary infection reaching the temporal lobe via olfactory/trigeminal nerves.

Clinical Features

Acute onset of fever, headache, behavioral changes, confusion, aphasia (dominant temporal lobe), seizures (focal > generalized), focal neurological deficits. Temporal lobe predilection is characteristic. Olfactory hallucinations may occur.

Diagnosis

Investigation	Findings
CSF	Lymphocytic pleocytosis (10–500), elevated protein, normal glucose, RBCs may be present (hemorrhagic necrosis); CSF HSV-1 PCR is the gold standard (Sn 98%, Sp 94%)
MRI Brain	T2/FLAIR hyperintensity in medial temporal lobes (often bilateral but asymmetric), insular cortex, inferior frontal lobe; DWI restriction; hemorrhagic changes
CT Brain	May be normal early; later shows low-density temporal lobe lesions ± hemorrhage
EEG	Periodic lateralized epileptiform discharges (PLEDs) over temporal regions; temporal sharp waves

HSE Treatment Protocol

Empirical treatment must NOT be delayed for test results.

Acyclovir 10 mg/kg IV q8h × 14–21 days

Start immediately on clinical suspicion (fever + encephalopathy + temporal lobe findings)
14 days minimum; extend to 21 days if immunocompromised or severe disease
Repeat CSF HSV PCR at day 14 before stopping — if still positive, continue treatment
Monitor renal function (crystalline nephropathy risk); adequate hydration essential
No role for adjunctive corticosteroids (unlike bacterial meningitis)

Prognosis: Even with treatment, significant morbidity: memory impairment (anterograde > retrograde), behavioral changes, aphasia, epilepsy. Younger age and early treatment predict better outcomes.

Clinical Pearl — HSV-2 Encephalitis: HSV-2 encephalitis occurs primarily in neonates (birth canal transmission) and immunocompromised adults. In adults, HSV-2 more commonly causes meningitis (benign, recurrent) rather than encephalitis.

7.2.3 Varicella-Zoster Virus (VZV) CNS Infections

VZV can cause multiple CNS syndromes beyond typical dermatomal zoster:

Syndrome	Features	Diagnosis
VZV Vasculopathy	Stroke (large vessel = granulomatous arteritis; small vessel = multifocal leukoencephalopathy). May occur weeks-months after zoster. Can occur without rash (“zoster sine herpete”)	CSF VZV PCR and/or anti-VZV IgG in CSF
VZV Meningitis	Lymphocytic meningitis; self-limited	CSF VZV PCR
VZV Encephalitis	Diffuse encephalitis, more common in immunocompromised	CSF VZV PCR + MRI
VZV Myelitis	Longitudinally extensive transverse myelitis; consider in differential with NMOSD	CSF VZV PCR; spinal MRI
Ramsay Hunt Syndrome	VZV reactivation in geniculate ganglion: ear pain, vesicles in ear canal, ipsilateral facial nerve palsy ± CN VIII involvement (hearing loss, vertigo)	Clinical; vesicular rash in ear

Treatment: Acyclovir 10–15 mg/kg IV q8h × 10–14 days (higher dose than HSV in some protocols). Ramsay Hunt: Valacyclovir 1g PO TID + corticosteroids.

7.2.4 Cytomegalovirus (CMV) CNS Infections

CMV CNS disease occurs almost exclusively in severely immunocompromised patients (HIV with CD4 <50, transplant recipients).

Syndromes: Ventriculoencephalitis (periventricular enhancement on MRI), polyradiculomyelitis (ascending weakness mimicking GBS, CSF PMN-predominant), retinitis.

Diagnosis: CSF CMV PCR. MRI: periventricular enhancement (ventriculitis).

Treatment: Ganciclovir 5 mg/kg IV q12h + Foscarnet 90 mg/kg IV q12h (combination for CNS disease). Duration: induction ≥3 weeks, then maintenance until immune reconstitution.

7.2.5 Japanese Encephalitis (JE)

Flavivirus transmitted by Culex mosquitoes; most important cause of viral encephalitis in Asia. Endemic in Thailand (especially rainy season, rural/agricultural areas). Incubation 5–15 days.

Clinical features: Acute encephalitis with high fever, altered consciousness, seizures, parkinsonian features (tremor, rigidity, masked facies), dystonia, upper motor neuron signs. Thalamic involvement is characteristic.

Diagnosis: Serum/CSF JE IgM (ELISA). MRI: bilateral thalamic T2 hyperintensity (highly characteristic), substantia nigra, basal ganglia.

Treatment: Supportive only; no specific antiviral. Mortality 20–30%; 30–50% of survivors have significant neurological sequelae (cognitive impairment, movement disorders, epilepsy).

Prevention: Vaccination (SA 14-14-2 live attenuated, or IXIARO inactivated). Included in Thai EPI schedule.

7.2.6 Rabies Encephalitis

Rhabdovirus (Lyssavirus) transmitted via bite of rabid animal (dogs most common in Thailand). Incubation: 1–3 months (range: days to years). Once symptoms appear, virtually 100% fatal.

Two clinical forms:

Form	Frequency	Features
Furious (encephalitic)	~80%	Hydrophobia, aerophobia, agitation, fluctuating consciousness, autonomic dysfunction, inspiratory spasms triggered by air/water on face
Paralytic (dumb)	~20%	Ascending flaccid paralysis (may mimic GBS), less hydrophobia, longer course

Diagnosis: Nuchal skin biopsy (immunofluorescence for rabies antigen), saliva RT-PCR, serum/CSF rabies antibodies. Brain autopsy: Negri bodies (pathognomonic eosinophilic inclusions in hippocampal neurons).

Post-exposure prophylaxis (PEP):

Wound care: Thorough washing with soap & water + povidone-iodine
Rabies immunoglobulin (RIG): 20 IU/kg (human) or 40 IU/kg (equine), infiltrated around wound + remainder IM at site distant from vaccine
Rabies vaccine: Thai Red Cross intradermal regimen (2-2-2-0-2): 0.1mL ID × 2 sites on days 0, 3, 7, 28. Or WHO Essen IM regimen: 1.0mL IM days 0, 3, 7, 14, 28

Thai Context: Thailand has an excellent post-exposure prophylaxis program. The Thai Red Cross developed the intradermal (ID) regimen which is WHO-endorsed and widely used in resource-limited settings. Despite this, Thailand still reports 5–10 rabies deaths annually, primarily from delayed PEP. Dog bite is the most common exposure.

7.2.7 HIV-Associated Neurological Disorders

Neurological manifestations occur in 40–70% of HIV-infected patients and may be the presenting feature. The differential depends heavily on the CD4 count.

HIV-Associated Opportunistic CNS Infections by CD4 Count

CD4 Count	Opportunistic CNS Infections
<500	TB meningitis, herpes zoster, bacterial meningitis
<200	PCP, chronic HSV, HIV-associated dementia (HAD)
<100	Cerebral toxoplasmosis, Cryptococcal meningitis, CMV encephalitis, M. avium complex (MAC), PML (JC virus), cryptosporidiosis
<50	CMV retinitis/encephalitis, MAC (disseminated), Toxoplasma

Progressive Multifocal Leukoencephalopathy (PML)

Potentially fatal demyelinating disease caused by reactivation of JC virus in immunosuppressed individuals: AIDS (CD4 <100), transplant recipients, natalizumab therapy (MS treatment). No specific treatment — restore immunity (initiate/optimize ART, reduce immunosuppression).

Clinical features: Subacute progressive neurological deficits: hemiparesis, hemianopia, diplopia, cognitive decline, gait ataxia, seizures. No fever (unlike infections).

Diagnosis: MRI: multifocal, asymmetric white matter T2/FLAIR hyperintensities (no mass effect, no enhancement typically). CSF JC virus PCR (Sn 72–92%). Brain biopsy if PCR negative but clinical suspicion high.

Prognosis: Without immune reconstitution, uniformly fatal within months. With ART-induced immune reconstitution, ~50% survival; however, risk of PML-IRIS (paradoxical worsening with inflammation).

Q: A 28-year-old woman presents with acute onset fever, confusion, word-finding difficulty, and seizures over 3 days. MRI shows T2 hyperintensity in the left medial temporal lobe and insular cortex with DWI restriction. What is the diagnosis and what is the most critical next step?

Diagnosis: HSV-1 encephalitis (HSE) — acute febrile encephalopathy with temporal lobe predilection, aphasia, and seizures is classic.
Most critical next step: Start Acyclovir 10 mg/kg IV q8h immediately while obtaining CSF for HSV PCR. Do NOT delay treatment for diagnostic testing. LP: expect lymphocytic pleocytosis, elevated protein, ± RBCs. CSF HSV-1 PCR confirms diagnosis (may be negative in first 72h — repeat if initially negative). Duration: 14–21 days. EEG may show PLEDs. Untreated mortality is 70%.

Q: An HIV-positive patient (CD4 = 45) presents with progressive left-sided weakness and visual field cut over 3 weeks without fever. MRI shows multifocal non-enhancing white matter lesions. What is the most likely diagnosis?

Diagnosis: Progressive Multifocal Leukoencephalopathy (PML) due to JC virus reactivation.
Key features: Subacute progressive focal deficits without fever, CD4 <100, non-enhancing asymmetric white matter lesions on MRI (no mass effect). Confirm with CSF JC virus PCR. No specific antiviral treatment — initiate ART to restore immunity. Brain biopsy if PCR negative. Beware PML-IRIS (paradoxical worsening after starting ART, with new contrast enhancement).

7.3 Tuberculous Meningitis (TBM)

7.3.1 Overview & Epidemiology

TBM is the most severe form of extrapulmonary tuberculosis, with mortality of 20–50% and significant neurological morbidity in survivors. It represents ~1% of all TB cases but carries the highest case-fatality rate. TBM accounts for 27% of meningitis in Thai adults (Ramathibodi data).

Delayed treatment is strongly associated with death and neurological sequelae. Empirical therapy should be given unless an alternative diagnosis is confirmed.

Spectrum of Neurotuberculosis

Manifestation	Description
TBM	Meningitis, basal arachnoiditis, spinal meningitis
Tuberculoma	Intracranial (parenchymal or extraparenchymal) or spinal mass lesion
TB abscess	Rare; larger cavitary lesion, often multiloculated
TB encephalopathy	With or without meningitis; diffuse cerebral edema
Spinal TB	Secondary to skeletal TB (Pott’s disease) or meningeal TB

7.3.2 Clinical Presentation

TBM typically presents as subacute meningitis evolving over 1–4 weeks (unlike acute bacterial meningitis).

Symptom/Sign	Frequency
Fever	~90%
Meningism (headache, neck stiffness)	~88%
Focal neurological deficit	~52%
Altered consciousness	33–72%
Cranial nerve palsy (especially CN VI, III)	20–40%
Seizures	~20%

BMRC (British Medical Research Council) Staging

Stage	Definition	Prognosis
Stage I	GCS 15, no focal deficits	Good outcome if treated early
Stage II	GCS 11–14, or any focal deficit	Intermediate
Stage III	GCS ≤10 (coma)	Mortality >50%, severe disability in survivors

7.3.3 Diagnosis

CSF Findings

CSF Parameter	Typical Findings in TBM
Opening pressure	Elevated (>25 cmH₂O) in ~50%
WBC	100–500 cells/mm³, lymphocyte predominant (may be neutrophilic in early <10 days)
Protein	100–500 mg/dL (can reach >1000 in spinal block)
Glucose	<45 mg/dL in ~80% (CSF:serum ratio <0.5)
ADA	>40 IU/L (Sn ~79%); less specific in HIV

Diagnostic Pitfalls in TBM:
• Elderly patients may have acellular CSF despite active TBM
• Early TBM (<10 days) may show neutrophil predominance mimicking bacterial meningitis
• HIV co-infection alters CSF profile: lower WBC, lower protein, ADA less reliable
• Normal CSF does not exclude TBM in early disease

Microbiological Diagnosis

Test	Sensitivity	Notes
AFB smear (Ziehl-Neelsen)	5–30%	Low yield; improved by large-volume CSF (10–20 mL) and repeated sampling
CSF culture (MGIT/LJ)	30–50%	Gold standard but takes 2–8 weeks; do NOT wait for results before treating
CSF TB PCR (GeneXpert MTB/RIF)	56–95% (pooled ~60–70%)	WHO-endorsed; rapid (~2h); also detects rifampicin resistance; lower Sn in CSF than sputum
GeneXpert Ultra	70–95%	Improved sensitivity over Xpert MTB/RIF; WHO recommends as initial test (conditional, 2017)
ADA (>10 IU/L)	Sn 79%, Sp 91%	Useful adjunct; threshold varies by study

Neuroimaging in TBM

MRI findings: Basal meningeal enhancement (basal cisterns), hydrocephalus (communicating or obstructive), tuberculomas (ring-enhancing lesions), infarcts (especially basal ganglia — due to vasculitis of perforating arteries). CT: basal cistern enhancement, hydrocephalus, tuberculomas.

Lancet Consensus Diagnostic Criteria for TBM (Marais et al. 2010)

Scoring system incorporating clinical (max 6), CSF (max 4), cerebral imaging (max 6), and evidence of TB elsewhere (max 4). Total score ≥12 = definite, 10–11 = probable, 6–9 = possible. This scoring aids clinical decision-making when microbiological confirmation is pending or unavailable.

7.3.4 Treatment of TBM

Anti-TB Regimen for CNS Tuberculosis (BIS 2009 / WHO)

Drug	Dose	Duration	CSF Penetration
Isoniazid (H)	300 mg/day (5 mg/kg)	10–12 months	Excellent — penetrates CSF freely; potent bactericidal
Rifampicin (R)	450 mg (<50 kg) / 600 mg (>50 kg)	10–12 months	Moderate — penetrates less well; high mortality from rifampicin-resistant TBM
Pyrazinamide (Z)	1.5 g (<50 kg) / 2.0 g (>50 kg)	2 months	Excellent — well-absorbed orally, high CSF concentration
Ethambutol (E)	15 mg/kg	2 months	Poor; no controlled trial data for CNS TB. Caution: optic neuropathy

Total treatment duration: at least 10–12 months. Can prolong until lesion subsides (especially tuberculomas).

Alternatives for the 4th drug: Streptomycin (caution: pregnancy, renal impairment, resistance common), Levofloxacin (limited data for prolonged therapy; caution in pregnancy/breastfeeding).

Adjunctive Corticosteroids in TBM

Drug	Dose	Duration
Dexamethasone	0.3–0.4 mg/kg/day (dose depends on BMRC stage)	4 weeks, then gradual taper over 2–4 weeks
Prednisolone	Equivalent dose (alternative)	4 weeks + taper

Landmark Trial: Thwaites et al. NEJM 2004

Thwaites Trial: RCT of adjunctive dexamethasone in Vietnamese adults with TBM (n=545). Dexamethasone significantly reduced mortality (RR 0.69; 9-month mortality 31.8% vs 41.3%) across all BMRC stages. Effect most pronounced in Stage II/III. However, did NOT reduce disability among survivors. Now standard of care worldwide.

Clinical Pearl — Paradoxical Reaction: 10–30% of TBM patients develop paradoxical worsening (new/enlarging tuberculomas, increasing meningeal enhancement) during appropriate treatment due to immune reconstitution. Management: continue anti-TB, add/increase corticosteroids. More common with HIV co-infection (TBM-IRIS).

7.3.5 TBM in HIV-Positive Patients

All patients with suspected CNS TB should be tested for HIV. The treatment regimen is the same as for HIV-negative patients, including corticosteroids.

ART Timing in CNS TB + HIV (BIS 2009)

CD4 Count	Recommended ART Timing
>200 cells/µL	Defer ART until end of TB treatment; start if CD4 falls <200 during treatment
100–200 cells/µL	Start ART after ~2 months of anti-TB treatment
<100 cells/µL	Start ART within first 2 weeks of anti-TB treatment

Key considerations:

Drug interactions: Rifampicin is a potent CYP3A4 inducer; use Efavirenz (not boosted PIs) or Dolutegravir 50mg BID (double dose) with rifampicin
IRIS risk: especially when CD4 <50; can be life-threatening in TBM (worsening meningitis, hydrocephalus, new tuberculomas)
Overlapping toxicities: hepatotoxicity (isoniazid + ART), peripheral neuropathy (isoniazid + stavudine/didanosine)

7.3.6 Complications & Management

Hydrocephalus

Communicating hydrocephalus is the most common complication of TBM, occurring in 60–80% of cases. Caused by basal cistern exudates blocking CSF absorption at arachnoid granulations.

Management: Serial therapeutic LP (if communicating), EVD for acute obstructive hydrocephalus, VP shunt for chronic/persistent hydrocephalus. Acetazolamide/furosemide have limited role.

Vasculitis & Stroke

TBM vasculitis affects perforating arteries at the base of the brain (lenticulostriate, thalamoperforating), causing basal ganglia and thalamic infarcts in 30–40% of TBM cases. Large vessel (MCA, ACA) involvement is less common but more devastating.

Management: Anti-TB therapy + corticosteroids. Aspirin 150 mg/day has shown mortality benefit in one RCT (Misra et al. Neurology 2010; n=118; mortality 14.6% vs 26.7% for Stage II/III).

Cranial Nerve Palsies

CN VI (most common), CN III, and CN VII affected due to basal meningeal inflammation. Usually improve with anti-TB treatment. Vision loss can occur from optochiasmatic arachnoiditis (requires urgent treatment).

Q: A 35-year-old Thai man presents with 2-week history of headache, low-grade fever, and progressive confusion. CSF shows WBC 250 (80% lymphocytes), protein 280 mg/dL, glucose 28 mg/dL (serum 110), ADA 52. CT shows basal cistern enhancement and hydrocephalus. What is the diagnosis and management plan?

Diagnosis: Tuberculous meningitis (BMRC Stage II — GCS ~12 with altered consciousness).
Diagnostic workup: CSF for AFB smear, GeneXpert MTB/RIF (or Ultra), culture; HIV test; CXR (pulmonary TB in ~50%).
Treatment (do NOT wait for microbiological confirmation):
1. Anti-TB: HRZE intensive phase (2 months) → HR continuation (total 10–12 months)
2. Dexamethasone 0.3–0.4 mg/kg/day × 4 weeks, then taper over 2–4 weeks
3. Hydrocephalus management: serial therapeutic LP (if communicating); EVD/VP shunt if progressive
4. If HIV+: test CD4 and plan ART timing accordingly
5. Pyridoxine 50 mg/day (prevent isoniazid neuropathy)
Prognosis: Stage II mortality ~20–30% with treatment; better if started early.

7.4 Fungal CNS Infections

7.4.1 Cryptococcal Meningitis

Cryptococcus neoformans is a budding yeast with polysaccharide capsule, the most common cause of meningitis in HIV-positive patients and the most common cause of meningitis overall at Ramathibodi Hospital (37% of all meningitis). Acquisition: inhalation of spores from pigeon droppings and soil. Hematogenous dissemination to CNS with predilection for meninges.

Clinical Features

S&S: Subacute-chronic headache (most common), increased ICP, altered consciousness, focal deficits. Meningism may be absent in immunocompromised. Can present as meningitis or cryptococcoma (mass lesion). Fever in ~70%. Papilledema in ~30%.

Important: Elevated ICP is a major cause of morbidity/mortality. Opening pressure >25 cmH₂O in >60% of HIV-associated cases.

Diagnosis

Test	Performance	Notes
CSF CrAg (Cryptococcal Antigen)	Sn >99%, Sp >99%	Best initial test; lateral flow assay (LFA) rapid point-of-care. Titer correlates with fungal burden
Serum CrAg	Sn >99% (in HIV)	Can be used for screening; if serum CrAg+ → LP mandatory
India Ink stain	Sn 50–80%	Encapsulated budding yeast; less sensitive than CrAg
CSF Fungal culture	Sn 95–100%	Gold standard for species identification; growth in 2–7 days on SDA
CSF profile	—	Mildly elevated WBC (lymph predominance), mildly elevated protein, normal/decreased glucose. May be near-normal in AIDS (paucicellular)

Clinical Pearl: In severely immunocompromised HIV patients, CSF may appear almost normal despite massive fungal burden. Always check CrAg even with normal CSF parameters. Serum CrAg screening in HIV patients with CD4 <100 before starting ART can prevent cryptococcal meningitis (preemptive fluconazole if CrAg+).

Treatment: WHO 2022 Guidelines

WHO 2022 Treatment of Cryptococcal Meningitis in HIV

Phase	Option	Regimen
Induction (Week 1–2)	1. Preferred	Single-dose Liposomal Amphotericin B 10 mg/kg (Day 1) + Flucytosine 100 mg/kg/day ÷4 × 14 days + Fluconazole 1200 mg/day × 14 days
	2. If L-AmB unavailable	Amphotericin B deoxycholate 1 mg/kg/day + Flucytosine × 1 week; then Fluconazole 1200 mg/day × 1 week
	3. If no AmB available	Fluconazole 1200 mg/day + Flucytosine × 2 weeks
	4. If no flucytosine	L-AmB 3–4 mg/kg/day + Fluconazole 1200 mg/day × 2 weeks
	5. If neither L-AmB nor flucytosine	AmB deoxycholate 1 mg/kg/day + Fluconazole 1200 mg/day × 2 weeks
Consolidation (Weeks 8–10)	Fluconazole 800 mg/day
Maintenance (Onwards)	Fluconazole 200 mg/day — continue until CD4 >200 for ≥6 months on ART, VL suppressed, and ≥1 year of antifungal therapy

Landmark Trial: AMBITION (NEJM 2022)

AMBITION Trial: Open-label RCT in 5 African countries (n=844). Single high-dose liposomal AmB 10 mg/kg + flucytosine + fluconazole was non-inferior to 7-day AmB deoxycholate-based regimen for 10-week all-cause mortality (24.8% vs 28.7%). Significantly fewer adverse events (less nephrotoxicity, anemia, hypokalemia). Now the WHO-preferred regimen.

ICP Management

Elevated ICP is the major killer in cryptococcal meningitis. Aggressive ICP management is critical.

Therapeutic LP: Daily LP to normalize pressure if OP >25 cmH₂O; remove 20–30 mL CSF per session until OP <20. Repeat daily until stabilized.
Lumbar drain or VP shunt: For refractory elevated ICP
Mannitol/acetazolamide: NOT recommended (ineffective, may be harmful)
Corticosteroids: NOT recommended for ICP management in cryptococcal meningitis (Beardsley et al. NEJM 2016: dexamethasone increased mortality)

ART Timing in Cryptococcal Meningitis: Delay ART for at least 4–6 weeks after starting antifungal therapy to avoid IRIS. The COAT Trial (Boulware, NEJM 2014) showed early ART (<2 weeks) increased mortality (45% vs 30% at 26 weeks) compared to deferred ART (5 weeks).

7.4.2 CNS Aspergillosis

Aspergillus spp. (septate mold) causes invasive CNS disease in severely immunocompromised patients: neutropenic (post-chemotherapy, HSCT), solid organ transplant, high-dose corticosteroids. Mechanism: hematogenous dissemination from pulmonary or direct extension from sinonasal aspergillosis.

S&S: Sinusitis, endophthalmitis, headache, seizure, cranial neuropathies, focal neurological deficits. CNS aspergillosis carries extremely high mortality (>90%).

Imaging: Multiple ring-enhancing or non-enhancing lesions, often hemorrhagic. Aspergillus has tropism for blood vessels → hemorrhagic infarction is characteristic. May see sino-orbital invasion with skull base erosion.

Diagnosis: Brain biopsy (septate hyphae with 45° branching); CSF galactomannan (variable sensitivity); culture.

Treatment: Voriconazole 6 mg/kg IV q12h ×2 doses, then 4 mg/kg IV q12h (drug of choice). Alternatives: Isavuconazole, Posaconazole, Liposomal Amphotericin B. Surgical debridement when possible. Restore immunity (G-CSF, reduce immunosuppression).

7.4.3 Mucormycosis (Mucorales)

Non-septate (pauciseptate) mold — Mucor, Rhizopus spp. Risk factors: uncontrolled DM (especially DKA), neutropenia, transplant, deferoxamine use, COVID-19-associated mucormycosis (CAM). Angioinvasive with rapid tissue necrosis.

Rhino-orbito-cerebral form: Most common CNS presentation. Starts in paranasal sinuses → invades orbit → cavernous sinus → brain. S&S: sinusitis, periorbital/facial pain, proptosis, ophthalmoplegia, black necrotic eschar on palate/nasal mucosa, cranial neuropathies, cavernous sinus thrombosis.

Diagnosis: Biopsy showing broad, ribbon-like, pauciseptate hyphae with irregular (90°) branching. Culture on SDA. MRI: sino-orbital soft tissue enhancement, perineural invasion, cavernous sinus involvement.

Treatment:

Surgical debridement — ESSENTIAL, aggressive, often disfiguring but life-saving
Liposomal Amphotericin B 5–10 mg/kg/day (first-line). Duration: weeks-months
Step-down: Posaconazole or Isavuconazole
Note: Mucorales are resistant to voriconazole (unlike Aspergillus)
Restore immunity; correct DKA, reverse neutropenia

7.4.4 Other Fungal CNS Infections

Dimorphic Fungi

Organism	Geographic Distribution	CNS Manifestation	Treatment
Talaromyces (Penicillium) marneffei	Southeast Asia (Thailand, Vietnam) — HIV/AIDS, anti-IFN-γ Ab	Meningitis, brain abscess (rare CNS involvement, ~5%)	L-AmB induction → Itraconazole maintenance
Histoplasma capsulatum	Americas (Ohio/Mississippi river valleys), Africa	Chronic meningitis, mass lesions	L-AmB × 4–6 weeks → Itraconazole × ≥1 year
Coccidioides immitis	Southwestern US, Mexico, Central/South America	Basilar meningitis (CSF eosinophils), hydrocephalus	Fluconazole (lifelong in meningitis) — one of few fungal meningitides where azole alone is primary

Candida CNS Infections

CNS candidiasis occurs in: neonates, neurosurgical patients (post-operative, shunts), disseminated candidiasis. Manifests as meningitis, brain abscess, or ventriculitis.

Treatment: Liposomal Amphotericin B ± Flucytosine (induction) → Fluconazole (step-down). Remove infected hardware.

Thai Context — Fungal Classification Approach: In Southeast Asia, key CNS-relevant fungi include:
• Yeasts: Cryptococcus (most important), Candida
• Dimorphic fungi: Talaromyces marneffei (endemic in northern Thailand, especially Chiang Rai), Histoplasma
• Molds — Septate: Aspergillus, Fusarium, Pseudallescheria boydii
• Molds — Non-septate: Mucor, Rhizopus (Mucorales)

Q: An HIV-positive patient (CD4 = 35) presents with 10-day headache and confusion. CSF: OP 38 cmH₂O, WBC 15 (100% lymph), protein 60 mg/dL, glucose 38 mg/dL. CSF India Ink shows encapsulated budding yeast. CrAg titer 1:2048. What is the treatment plan?

Diagnosis: Cryptococcal meningitis with elevated ICP (OP 38).
Treatment plan:
1. Induction (preferred WHO 2022): Single-dose Liposomal AmB 10 mg/kg (Day 1) + Flucytosine 100 mg/kg/day ÷4 × 14 days + Fluconazole 1200 mg/day × 14 days
2. ICP management (CRITICAL): Daily therapeutic LP, removing 20–30 mL CSF until OP <20 cmH₂O. This is the most important mortality-reducing intervention.
3. Consolidation: Fluconazole 800 mg/day × 8 weeks
4. Maintenance: Fluconazole 200 mg/day (until CD4 >200 for 6+ months on ART)
5. Delay ART for 4–6 weeks (COAT trial: early ART increases mortality)
6. Do NOT give corticosteroids (Beardsley NEJM 2016: increased mortality)

7.5 Cerebral Toxoplasmosis & CNS Parasites

7.5.1 Cerebral Toxoplasmosis

Toxoplasma gondii is an obligate intracellular protozoan. Transmission: ingestion of oocysts from cat feces or undercooked meat containing tissue cysts. In immunocompetent hosts, infection is usually asymptomatic. Reactivation of tissue cysts in immunosuppressed persons (especially AIDS with CD4 <100) causes toxoplasmic encephalitis — the most common cause of intracerebral mass lesions in AIDS.

Clinical Features

Headache, seizure, altered consciousness, focal neurological deficits (hemiparesis). Subacute onset over days to weeks. Fever in ~50%.

Diagnosis

Usually presumptive: clinical syndrome + positive Toxoplasma IgG + characteristic imaging in an HIV patient with CD4 <100.

Imaging: CT/MRI shows multiple ring-enhancing lesions with surrounding edema, typically at corticomedullary junction and basal ganglia. Classic “eccentric target sign” (eccentric enhancing nodule within ring).

If no clinical improvement after empirical therapy × 10–14 days → brain biopsy to exclude CNS lymphoma.

Treatment

Setting	Regimen	Duration / Comments
Compromised host (AIDS/transplant) — Primary regimen	Pyrimethamine 200mg load, then 50–75mg/day + Sulfadiazine 4–6g/day + Leucovorin 10–25mg/day	Treat 6 weeks (acute), then secondary suppression
Alternative regimen	TMP-SMX (co-trimoxazole) 5mg/kg TMP component q12h	6 weeks; WHO preferred in resource-limited settings
Alternative regimen	Pyrimethamine + Clindamycin 600mg q6h	If sulfa allergy
Secondary prophylaxis	TMP-SMX 1 DS tab daily (or pyrimethamine + sulfadiazine)	Continue until CD4 >200 for ≥6 months on ART
Competent host	Usually no treatment needed	Treat active chorioretinitis (3 weeks), pregnancy (4 weeks or through pregnancy), congenital (at least 1 year)

7.5.2 Neurocysticercosis (NCC)

Caused by the larval form (cysticercus) of Taenia solium (pork tapeworm). Most common parasitic CNS infection worldwide and leading cause of acquired epilepsy in endemic areas. Transmission: fecal-oral ingestion of T. solium eggs (NOT from eating pork; that causes intestinal taeniasis).

Clinical Manifestations

Depends on cyst location, number, and host inflammatory response:

Stage	Imaging	Symptoms
Vesicular (viable cyst)	Cystic lesion with scolex, no edema/enhancement	Usually asymptomatic
Colloidal vesicular (degenerating)	Ring enhancement, perilesional edema	Seizures (most common presentation), headache
Granular nodular	Nodular enhancement, decreasing edema	Seizures, resolving symptoms
Calcified	Calcified nodule, no enhancement	May still cause seizures (perilesional edema flares)

Special forms:

Subarachnoid NCC: Racemose cysts in basal cisterns; causes chronic meningitis, hydrocephalus, vasculitis, cranial neuropathies. Worst prognosis.
Intraventricular NCC: Cyst in ventricle; acute obstructive hydrocephalus (emergency). Requires endoscopic removal.
Spinal NCC: Rare; cord compression.

Diagnosis

Del Brutto Criteria (2017): Absolute criteria: histologic demonstration or cystic lesion with scolex on imaging. Major criteria: enhancing lesions, multilobulated subarachnoid cysts, typical parenchymal calcifications. Minor/epidemiologic criteria: positive serology (EITB/ELISA), endemic area, suggestive clinical features.

Serology: EITB (enzyme-linked immunoelectrotransfer blot) is best (Sn 98% for >2 cysts; lower for single cyst). ELISA less specific.

Treatment

NCC Treatment Algorithm

1–2 viable parenchymal cysts: Albendazole 15 mg/kg/day (max 1200mg) × 10–14 days + corticosteroids (dexamethasone or prednisolone started 1–2 days before and continued during). Add anti-epileptic drugs for seizures.

>2 viable parenchymal cysts: Albendazole + Praziquantel 50 mg/kg/day × 10–14 days (combination is superior per Garcia et al. Lancet ID 2014).

Subarachnoid/racemose NCC: Prolonged albendazole (months) + corticosteroids; often requires VP shunt for hydrocephalus. Methotrexate may be needed as steroid-sparing agent.

Intraventricular NCC: Endoscopic removal (treatment of choice); albendazole pre/post-operatively. EVD for acute hydrocephalus.

Calcified NCC only: No antiparasitic therapy; manage seizures (AEDs ± short-course steroids for perilesional edema).

Do NOT give antiparasitic therapy for: Cysticercotic encephalitis (massive cyst burden with diffuse edema — steroids only), calcified-only disease.

7.5.3 Eosinophilic Meningitis (Thai-Relevant Parasites)

Angiostrongylus cantonensis

Rat lungworm; transmission via ingestion of raw snails, slugs, or contaminated produce. Most common cause of eosinophilic meningitis worldwide, highly relevant in Thailand and Southeast Asia.

Clinical features: Headache (severe), meningism, cranial nerve palsies (especially CN VII), paresthesias; self-limited over 2–4 weeks in most cases.

CSF: Eosinophils >10% (often >50%), elevated protein, normal glucose, very high opening pressure. Larvae rarely found in CSF.

Treatment: Supportive (analgesics, serial therapeutic LP for headache relief). Corticosteroids (prednisolone 60 mg/day × 2 weeks) reduce headache duration. Avoid anthelmintics in acute phase (may worsen inflammation from dying larvae). Albendazole controversial.

Gnathostoma spinigerum

Acquired from eating raw freshwater fish (“som fak,” “pla ra” in Thai cuisine). Highly relevant in Thailand.

CNS manifestation: Eosinophilic meningoencephalitis/myelitis (worm migrates through CNS). Can cause subarachnoid hemorrhage, radiculomyelitis, cranial nerve palsies. More severe than Angiostrongylus — can be fatal.

CSF: Bloody or xanthochromic (pathognomonic of CNS gnathostomiasis), eosinophilic.

Treatment: Albendazole 400mg BID × 21 days + corticosteroids. Surgical removal if worm accessible.

Thai Pearl — Eosinophilic Meningitis DDx: In Thailand, when CSF shows eosinophils >10%:
• Angiostrongylus cantonensis (snails/slugs) — most common, self-limited
• Gnathostoma spinigerum (raw fish) — bloody CSF, more severe
• Toxocara (dog/cat roundworms) — rare CNS
• Coccidioides — not endemic in Thailand
• Drug reaction, TB, lymphoma — non-parasitic causes
Ask about dietary history: raw snail/slug → Angiostrongylus; raw freshwater fish → Gnathostoma.

7.5.4 Cerebral Malaria

Caused by Plasmodium falciparum; defined as unarousable coma (GCS ≤11 in adults, BCS ≤2 in children) in the setting of P. falciparum parasitemia with no other identifiable cause. Mechanism: sequestration of parasitized RBCs in cerebral microvasculature.

Clinical features: Diffuse encephalopathy, seizures (especially in children), retinopathy (pathognomonic: retinal whitening, vessel changes, hemorrhages). Mortality 15–25% with treatment.

Treatment: IV Artesunate 2.4 mg/kg at 0, 12, 24h, then daily (WHO first-line; superior to quinine based on SEAQUAMAT and AQUAMAT trials). Complete course with ACT orally once able. Supportive: seizure management, ICP management, transfusion if severe anemia.

7.6 CNS Infections in the Immunocompromised Host

7.6.1 Framework: Immune Defect → Pathogen Prediction

Understanding which arm of immunity is compromised predicts the likely CNS pathogen:

Immune Defect	Mechanism	Typical CNS Pathogens
B-cell / Antibody deficiency (Rituximab, splenectomy, CVID, hypogammaglobulinemia)	Loss of opsonization, complement activation	S. pneumoniae, H. influenzae, Staphylococci; Enteroviruses (chronic meningoencephalitis in agammaglobulinemia)
T-cell / Cellular immunity deficiency (HIV/AIDS, transplant, CNI, ATG, high-dose steroids, natalizumab)	Loss of intracellular pathogen control	Intracellular pathogens: Cryptococcus, Toxoplasma, TB/NTM, Listeria, CMV, VZV, JC virus (PML), Aspergillus, Candida, Pneumocystis, Salmonella
Complement deficiency (Eculizumab, terminal complement)	Loss of MAC formation	*Neisseria meningitidis* (up to 2000-fold increased risk)
Neutrophil deficiency / dysfunction (Post-chemotherapy, AML, HSCT pre-engraftment)	Loss of phagocytosis	Staphylococci, Gram-negatives, *Aspergillus, Candida, Mucorales*

Immunosuppressive Drugs & Their Immune Targets

Category	Drug	Primary Immune Effect
Loss of T-cell function	Basiliximab (anti-IL2R)	T & B cell depletion
	ATG (anti-thymocyte globulin)	T cell depletion
	Calcineurin inhibitors (tacrolimus, cyclosporine)	Inhibit T cell proliferation
	Mycophenolate / Azathioprine	Inhibit T & B cell proliferation
	High-dose glucocorticoids	Broad immunosuppression, T > B
Loss of B-cell / antibody function	Rituximab (anti-CD20)	B cell depletion
	Splenectomy / asplenia	Loss of opsonophagocytic function
	Plasmapheresis	Removes all antibodies
Complement inhibition	Eculizumab	Terminal complement (C5) inhibition

Level of immune suppression: IV Cyclophosphamide > Mycophenolate = Azathioprine. All suppress T cells > B cells.

7.6.2 Anti-IFN-γ Autoantibody Syndrome

Emerging entity highly relevant in Southeast Asia (Thailand, Taiwan). Patients develop neutralizing autoantibodies against IFN-γ, causing acquired immunodeficiency resembling HIV/AIDS but without HIV infection.

Typical infections: Disseminated NTM (M. abscessus, MAC), Talaromyces marneffei, Salmonella, Cryptococcus, Burkholderia pseudomallei, VZV.

CNS involvement: Meningitis (NTM, Crypto), brain abscess, pachymeningitis.

Treatment: Prolonged antimicrobial therapy + rituximab (to deplete B cells producing anti-IFN-γ Ab) + cyclophosphamide in refractory cases.

7.6.3 Post-Transplant CNS Infections Timeline

Period	Common CNS Infections
<1 month	Nosocomial bacteria (S. aureus, GNR), Aspergillus (neutropenic HSCT), HSV reactivation
1–6 months	CMV, Aspergillus, Toxoplasma, Listeria, Nocardia, PML (JC virus), TB
>6 months	Cryptococcus, PML, community-acquired infections, VZV

7.7 Neuroimaging in CNS Infections

Imaging Classification of CNS Infections

Location	Focal	Diffuse
Extra-axial	Epidural abscess, subdural empyema	Pachymeningitis, leptomeningitis
Intra-axial	Brain abscess (gray-white junction), tuberculoma	Encephalitis (temporal/basal for HSV; diffuse for others)

Key Imaging Patterns by Pathogen

Imaging Pattern	Pathogen / Diagnosis
Medial temporal lobe T2 hyperintensity	HSV-1 encephalitis
Bilateral thalamic T2 hyperintensity	Japanese encephalitis
Basal meningeal enhancement + hydrocephalus	TBM
Multiple ring-enhancing lesions + edema (at gray-white junction)	Cerebral toxoplasmosis (AIDS), brain abscess, metastases
Ring-enhancing lesion with DWI restriction	Brain abscess (pyogenic)
Asymmetric non-enhancing white matter lesions (no mass effect)	PML (JC virus)
Periventricular enhancement	CMV ventriculitis
Cystic lesion with scolex	Neurocysticercosis
Hemorrhagic lesion + ring enhancement + sino-orbital invasion	Mucormycosis or Aspergillosis

Imaging Pearl: CT is useful for rapid emergency assessment (hydrocephalus, mass effect, hemorrhage). MRI is superior for detailed characterization of CNS infections (meningeal enhancement, parenchymal lesions, DWI for abscess). Always compare imaging findings with clinical context and immune status.

7.8 References & Guidelines

Key Guidelines

ESCMID Guideline on Acute Bacterial Meningitis. Clin Microbiol Infect 2016;22:S37–S62.
IDSA Practice Guidelines for Bacterial Meningitis. Clin Infect Dis 2004;39:1267–84.
WHO Guidelines on Cryptococcal Disease in HIV-infected Adults, Adolescents and Children. WHO 2022.
Thwaites G et al. British Infection Society Guidelines for TB of the CNS. J Infect 2009;59:167–87.
AAN/IDSA/AAN Practice Parameter: NCC Management. Neurology 2002;59:1228–1236.
Del Brutto OH. Revised Diagnostic Criteria for Neurocysticercosis. J Neurol Sci 2017;372:202–210.

Landmark Trials & Key Studies

Thwaites Trial: Thwaites GE et al. Dexamethasone for TBM in adults & adolescents. NEJM 2004;351:1741–51.
AMBITION Trial: Jarvis JN et al. Single-dose L-AmB for Cryptococcal Meningitis. NEJM 2022;386:1109–20.
COAT Trial: Boulware DR et al. Timing of ART after Cryptococcal Meningitis. NEJM 2014;370:2487–98.
Beardsley Trial: Beardsley J et al. Adjunctive Dexamethasone in Cryptococcal Meningitis. NEJM 2016;374:542–54.
de Gans J, van de Beek D. Dexamethasone in Adults with Bacterial Meningitis. NEJM 2002;347:1549–56.
Cochrane Review: Corticosteroids for Bacterial Meningitis. Cochrane Database Syst Rev 2015;9:CD004405.
Brouwer MC et al. Community-acquired Bacterial Meningitis. Lancet 2012;380:1684–92.
van de Beek D et al. Bacterial Meningitis. Lancet 2021;398:1171–83.
McGill F et al. Acute Bacterial Meningitis in Adults. JAMA 2022;328:2147–55.
Garcia HH et al. Antiparasitic Treatment for NCC. NEJM 2004;350:249–58.
Garcia HH et al. Combined Albendazole + Praziquantel for NCC. Lancet Infect Dis 2014;14:687–95.
Misra UK et al. Aspirin in TBM. Neurology 2010;75:1530–32.
SEAQUAMAT: Dondorp AM et al. Artesunate vs Quinine for Severe Malaria. Lancet 2005;366:717–25.
Ngan NT et al. Treatment of Cryptococcal Meningitis. Drugs 2022.
Hasbun R et al. CT before LP in suspected meningitis. NEJM 2001;345:1727–33.

Thai Data & Local Sources

Aimbudlop et al. Etiology of meningitis in Thai adults. J Infect Chemother (Ramathibodi data).
Thammasat Meningitis Series. Neurology Asia 2020.
NARST (National Antimicrobial Resistance Surveillance Thailand). 2022 Annual Report, 68 hospitals.
Pakpoom Phoompoung. CNS Infection in Immunocompetent Host. Siriraj Hospital Lecture Series.
Thananya Wongsinin. Treatment of Neurological Infection in Immunocompromised Setting. CNMI, Ramathibodi/Mahidol University.
Abhinbhen W. Saraya. Treatment of Neurological Infection in Community Setting. King Chulalongkorn Memorial Hospital, Thai Red Cross.
Siriththin Chansirikarnjana. Imaging in Infectious Disease. NIT Radiology.

8. Dementia & Cognitive Disorders

This section provides a comprehensive subspecialist-depth review of dementia and cognitive disorders. Coverage includes the neurodegenerative proteinopathy framework (molecular mechanisms, protein misfolding, prion-like propagation), Alzheimer’s disease (amyloidopathy, tauopathy, neuroinflammation, genetics — Goldman score & 17-gene panel, epigenetics), the NIA-AA 2024 revised biomarker framework (ATX(N)IVS with T₁/T₂ split), plasma biomarker revolution (p-tau217), FDG-PET signature patterns, diagnostic pathway algorithms, disease-modifying anti-amyloid therapy (lecanemab CLARITY-AD, donanemab TRAILBLAZER-ALZ 2, ARIA monitoring), symptomatic pharmacotherapy, DLB (McKeith 2017, αSyn-SAA), FTD spectrum (bvFTD, PPA variants, C9orf72/GRN/MAPT genetics, FTD-ALS continuum, PSP & CBS), vascular cognitive impairment, NPH, reversible dementias, and rapidly progressive dementia including prion diseases.

8.1 Neurodegenerative Proteinopathy — Molecular Framework

8.1.1 The Proteinopathy Paradigm

Modern understanding of neurodegenerative diseases has shifted from purely clinical-anatomical classification to a molecular proteinopathy framework. All major neurodegenerative dementias share a common pathogenic cascade: protein misfolding → oligomer formation → fibrillar aggregation → prion-like propagation → selective neuronal vulnerability → network degeneration.

Clinicopathological Spectrum of Neurodegenerative Proteinopathy

Misfolded Protein	Normal Function	Disease Spectrum	Key Pathology
Aβ (Amyloid-beta)	APP: synapse formation, neuroplasticity, iron export	Alzheimer’s disease, CAA	Extracellular amyloid plaques (diffuse & neuritic)
Tau (3R/4R)	Microtubule stabilization, axonal transport	AD (secondary), PSP, CBD, Pick disease, FTLD-tau, AGD, CTE	Neurofibrillary tangles (NFT), neuropil threads
α-Synuclein	Synaptic vesicular transport, SNARE complex	PD, DLB, MSA, PDD	Lewy bodies, Lewy neurites, glial cytoplasmic inclusions (MSA)
TDP-43	RNA metabolism, splicing, transport	FTLD-TDP, ALS, FTD-MND, LATE	Cytoplasmic inclusions with nuclear clearing
FUS	RNA metabolism, DNA repair	FTLD-FUS, ALS-FUS	Cytoplasmic/intranuclear inclusions
PrP^Sc (Prion)	PrP^C: copper homeostasis, cell signaling	CJD, vCJD, FFI, GSS, Kuru	Spongiform change, PrP deposits

8.1.2 Molecular Mechanisms of Protein Misfolding

The pathogenic cascade involves failure of protein quality control (PQC) systems:

PQC Mechanism	Function	Failure Consequence
Molecular chaperones (HSP70, HSP90)	Assist correct folding, prevent aggregation	Accumulation of misfolded monomers
Ubiquitin-proteasome system (UPS)	Degrade short-lived/misfolded proteins	Ubiquitinated protein aggregates
Autophagy-lysosome pathway (ALP)	Clear aggregated proteins, damaged organelles	Failure to clear oligomers/fibrils

Prion-like propagation: Misfolded proteins act as “seeds” that template the misfolding of normal proteins. Cell-to-cell spread follows anatomically connected neural networks, explaining the stereotypical regional progression of each disease (e.g., Braak staging in AD and PD).

Clinical Pearl — Why Proteinopathy Matters for Clinicians: Understanding the molecular substrate guides: (1) biomarker selection (Aβ, p-tau, αSyn-SAA, NfL), (2) therapeutic targets (anti-amyloid antibodies, tau aggregation inhibitors, α-synuclein immunotherapy), (3) recognition of mixed pathology (up to 50% of dementia cases have ≥2 coexisting proteinopathies at autopsy), and (4) genetic counseling (protein-specific gene panels).

8.1.3 Neuroinflammation in Neurodegeneration

Neuroinflammation is now recognized as a central driver (not just bystander) of neurodegeneration, particularly in AD.

Microglia: The Double-Edged Sword

Phase	Microglial Phenotype	Effect
Early/Protective	Homeostatic → phagocytic	Aβ clearance, debris removal, synapse pruning
Chronic/Pathological	Pro-inflammatory (DAM/MGnD)	Sustained cytokine release (IL-1β, TNF-α), complement activation, synaptic stripping

The NLRP3 Inflammasome — Positive Feedback Loop

Aβ oligomers activate microglial NF-κB pathway → NLRP3 inflammasome assembly → Caspase-1 activation → IL-1β/IL-18 release. Critically, released ASC specks (adaptor protein aggregates) serve as binding cores for further Aβ aggregation, creating a self-amplifying cycle. This links innate immunity directly to amyloid pathology (Venegas et al. Nature 2017).

Microglia–Astrocyte Crosstalk

Activated microglia secrete IL-1α, C1q, TNF-α → convert resting astrocytes to A1 neurotoxic astrocytes that lose normal supportive functions and actively kill neurons and oligodendrocytes (Liddelow et al. Nature 2017). GFAP (glial fibrillary acidic protein) elevation in CSF/plasma reflects this astrocyte activation and is now incorporated in the NIA-AA 2024 biomarker framework as an inflammation/astrocytic biomarker.

Pathogenesis Cascade: From Risk Factors to Dementia

Risk factors (genetics [APOEε4, TREM2], aging, DM, hypertension, obesity, infections, gut dysbiosis, air pollution) → Systemic inflammation → BBB disruption (pericyte loss, tight junction dysfunction) → Aβ accumulation + Tau hyperphosphorylation + Neuroinflammation (microglia/astrocyte activation) → Synaptic loss → Neuronal death → Network failure → Cognitive decline → Dementia

8.1.4 Genetics of Dementia

Heritability & Genetic Architecture

Gene/Locus	Protein	Mechanism	Disease	Inheritance
APP (chr 21)	Amyloid precursor protein	↑β-secretase cleavage → ↑Aβ42	Early-onset AD (<65y)	AD (autosomal dominant)
PSEN1 (chr 14)	Presenilin-1 (γ-secretase)	↑γ-secretase → ↑Aβ42/40 ratio	Early-onset AD (most common genetic cause, onset 30–50y)	AD
PSEN2 (chr 1)	Presenilin-2 (γ-secretase)	↑γ-secretase → ↑Aβ42	Early-onset AD (rarer, later onset than PSEN1)	AD
APOE (chr 19)	Apolipoprotein E	ε4: ↓Aβ clearance, ↑aggregation; ε2: protective	Late-onset AD (strongest genetic risk factor)	Risk modifier
MAPT (chr 17)	Tau	Altered 3R/4R tau ratio, ↑aggregation	FTLD-tau, PSP, CBD	AD
GRN (chr 17)	Progranulin	Haploinsufficiency → lysosomal dysfunction	FTLD-TDP (FTD)	AD
C9orf72 (chr 9)	C9orf72 protein	GGGGCC hexanucleotide repeat expansion	FTD, ALS, FTD-ALS (most common genetic cause)	AD
TREM2	Microglial receptor	Impaired microglial Aβ phagocytosis	AD (risk factor, OR ~2–4)	Risk modifier
PRNP (chr 20)	Prion protein	Misfolding susceptibility; octapeptide repeat insertions	Genetic CJD, FFI, GSS	AD
NOTCH3 (chr 19)	Notch3 receptor	Small vessel vasculopathy	CADASIL	AD

Modified Goldman Score — When to Offer Genetic Testing

Goldman Score	Family History Pattern	Recommendation
1	≥3 affected family members across ≥2 generations (autosomal dominant pattern)	Strongly recommend genetic testing & counseling
2	≥3 affected but in 1 generation only	Consider testing
3	1 other affected family member	May consider, especially if early-onset
3.5	Family history unknown/limited	Case-by-case
4	No family history of dementia	Generally do NOT test (unless early-onset <60y or atypical phenotype)

Suggested algorithm: AD onset <60y OR strong FHx → targeted dementia gene panel (17 genes: APP, CHMP2B, CSF1R, FUS, GRN, ITM2B, MAPT, NOTCH3, PRNP, PSEN1, PSEN2, SERPINI1, SQSTM1, TARDBP, TREM2, TYROBP, VCP) + C9orf72 repeat expansion PCR. Suspected HD → HTT CAG repeat. Suspected prion → PRNP sequencing.

Genetic Heterogeneity: Pleiotropy & Phenocopies

Pleiotropy: A single gene can produce multiple phenotypes (e.g., C9orf72 expansion → bvFTD, ALS, FTD-ALS, PPA, psychosis, or parkinsonism). Phenocopy: Different genes can produce identical clinical syndromes (e.g., bvFTD phenotype from MAPT, GRN, C9orf72, or TARDBP mutations). This underscores why broad gene panels are preferred over single-gene testing.

Epigenetics in Dementia

Epigenetic modifications mediate gene–environment interactions in neurodegeneration:

DNA methylation: Hypermethylation of neuroprotective genes; altered in AD hippocampus
Histone modifications: Deacetylation → chromatin compaction → reduced synaptic gene expression
Non-coding RNAs: miR-132 (downregulated in AD; regulates tau splicing), miR-146a (neuroinflammation modulator)
Environmental modifiers: Heavy metals (lead, mercury), air pollution (PM2.5), pesticides, nutritional factors (folate, B12), physical activity, sleep quality

8.1.5 Alzheimer’s Disease — Comprehensive Review

Epidemiology

AD accounts for 60–70% of all dementia worldwide. Prevalence doubles every 5 years after age 65. Thai prevalence: ~3.3% in age ≥60 (community-based studies). Women have 1.5–2× higher risk than men (longevity, hormonal, APOEε4 interaction).

APP Processing & Amyloidopathy

Amyloid Precursor Protein (APP) Processing Pathways

Pathway	Enzyme	Products	Effect
Non-amyloidogenic (physiologic)	α-secretase (ADAM10) then γ-secretase	sAPPα + p3 fragment	Neuroprotective: neurotrophic, anti-apoptotic
Amyloidogenic (pathologic)	β-secretase (BACE1) then γ-secretase	sAPPβ + Aβ40/Aβ42	Neurotoxic: Aβ42 is more hydrophobic, aggregation-prone → oligomers → fibrils → plaques

Genetic mutations shift balance toward amyloidogenic pathway:

APP mutations: ↑β-secretase cleavage efficiency
PSEN1/PSEN2 mutations: alter γ-secretase → ↑Aβ42/Aβ40 ratio
ADAM10 mutations: ↓α-secretase → less sAPPα, more substrate for β-secretase
APOEε4: ↓Aβ clearance (impaired microglial phagocytosis, reduced perivascular drainage)

Tauopathy in AD

Tau is a secondary proteinopathy in AD (triggered by amyloid), unlike primary tauopathies (PSP, CBD, Pick). The pathogenic sequence:

Aβ oligomers activate kinases (GSK-3β, CDK5) & inhibit phosphatases (PP2A)
Hyperphosphorylated tau detaches from microtubules → microtubule collapse → impaired axonal transport
Free p-tau aggregates into paired helical filaments (PHF) → neurofibrillary tangles (NFT)
NFT-bearing neurons undergo apoptosis
Released tau seeds propagate in prion-like fashion along connected neural circuits

Braak Staging of Tau Pathology in AD

Braak Stage	Region	Clinical Correlation
I–II (Transentorhinal)	Entorhinal cortex, hippocampus	Preclinical (no symptoms or subjective decline)
III–IV (Limbic)	Hippocampus, amygdala, medial temporal lobe	MCI, early AD (episodic memory impairment)
V–VI (Neocortical)	Widespread neocortex (temporal, frontal, parietal)	Moderate-severe AD (multi-domain cognitive impairment)

Key insight: Tau burden (not amyloid plaque load) correlates most closely with cognitive decline and neurodegeneration. This is why T₂ biomarkers (tau PET, MTBR-tau243) are best for disease staging and prognosis.

Primary vs. Secondary Tauopathies

Feature	Primary Tauopathy	Secondary Tauopathy (AD)
Examples	PSP, CBD, Pick disease, FTLD-MAPT, AGD, CTE	Alzheimer’s disease, CAA
Tau isoform	Usually 3R or 4R predominant	Mixed 3R+4R
Amyloid pathology	Absent	Present (Aβ drives tau)
Tau PET pattern	Varies (frontal/subcortical in PSP; asymmetric frontoparietal in CBD)	Temporoparietal, posterior cingulate/precuneus
Response to anti-amyloid	None expected	May slow tau spread indirectly

8.1.6 Clinical Features of AD

Cognitive Continuum

The AD clinical trajectory spans a continuum over 15–25 years from initial molecular changes to severe dementia:

Stage	Definition	Key Features	Approximate Duration
Preclinical AD	Biomarker-positive (A+T+), cognitively normal	No subjective or objective cognitive impairment; only detectable by biomarkers	10–20 years before symptoms
Subjective Cognitive Decline (SCD)	Self-perceived decline, normal on testing	Patients notice “memory isn’t what it used to be”; objective tests normal	Variable
MCI due to AD	Objective cognitive impairment, preserved ADL	Episodic memory impairment (amnestic MCI); CDR 0.5; conversion to dementia ~10–15%/year	2–5 years
Mild AD dementia	Cognitive impairment affecting ADL	Recent memory loss, word-finding difficulty, spatial disorientation, impaired IADL	2–4 years
Moderate AD	Increasing dependency	BPSD prominent (agitation, wandering, psychosis), impaired BADL, apraxia	2–3 years
Severe AD	Complete dependency	Minimal verbal output, incontinence, dysphagia, immobility, total care needs	2–3 years

AD Subtypes & Atypical Presentations

Subtype	Age of Onset	Predominant Deficit	Neuroimaging Pattern
Typical (amnestic) AD	Usually >65y	Episodic memory (hippocampal)	Medial temporal atrophy, temporoparietal hypometabolism
Posterior Cortical Atrophy (PCA)	50–65y	Visuospatial/visuoperceptual (Balint, simultanagnosia)	Occipitoparietal atrophy & hypometabolism
Logopenic PPA (lvPPA)	55–70y	Word-finding, sentence repetition impaired	Left temporoparietal junction atrophy
Frontal/Behavioral variant AD	50–65y	Executive dysfunction, behavioral changes (mimics bvFTD)	Frontal atrophy/hypometabolism
Corticobasal syndrome	Variable	Asymmetric parkinsonism, apraxia, alien limb	Asymmetric frontoparietal atrophy

Clinical Pearl — Early-Onset AD (<65y): Accounts for ~5–10% of all AD. More likely to have atypical presentations (PCA, lvPPA, frontal variant), faster progression, stronger genetic contribution (check APP, PSEN1, PSEN2), and more prominent non-memory deficits. Biomarker confirmation is particularly important in this group to distinguish from non-AD dementias. APOEε4 homozygosity may present as early-onset AD with typical amnestic pattern.

8.1.7 Cognitive Assessment Tools

Tool	Domains Tested	Cut-off (Thai)	Strengths / Limitations
MMSE	Orientation, registration, attention, recall, language, construction	≤23/30 (adjusted for education)	Widely used; ceiling effect in MCI; poor for frontal/executive dysfunction
MoCA	Executive, visuospatial, naming, memory, attention, language, abstraction, orientation	≤25/30 (add 1 point if education ≤12y)	Better sensitivity for MCI; tests executive function; Thai version validated (MoCA-Thai)
CDR (Clinical Dementia Rating)	Memory, orientation, judgment, community affairs, home/hobbies, personal care	0 = normal; 0.5 = MCI; 1–3 = mild–severe dementia	Gold standard for staging; requires informant interview; used in clinical trials (CDR-SB)
ADAS-Cog	Memory, language, praxis, orientation	Higher score = worse (0–70)	Standard outcome measure in AD drug trials
Thai Mental State Examination (TMSE)	Similar to MMSE, adapted for Thai language/culture	≤23/30	Validated for Thai population; widely used in community screening

Clinical Pearl — BPSD Assessment: Behavioral and Psychological Symptoms of Dementia affect >80% of AD patients at some stage. Use NPI (Neuropsychiatric Inventory) for systematic assessment: delusions, hallucinations, agitation, depression, anxiety, apathy, disinhibition, irritability, aberrant motor behavior, sleep disturbance, appetite change. NPI score guides pharmacological intervention decisions.

Q: A 58-year-old man presents with 2-year progressive difficulty with reading, judging distances, and dressing. He gets lost in familiar places. His memory for recent events is relatively preserved. MMSE 22/30 (loses points on construction, attention, orientation). MRI shows bilateral occipitoparietal atrophy. Amyloid PET is positive. What is the diagnosis and what biomarker framework category does this fall under?

Diagnosis: Posterior Cortical Atrophy (PCA) — an atypical presentation of Alzheimer’s disease.
Key features: Progressive visuospatial/visuoperceptual deficits (reading difficulty = visual variant, judging distances = visuospatial, dressing difficulty = dressing apraxia), relatively preserved episodic memory, occipitoparietal atrophy, amyloid-positive.
NIA-AA 2024 biomarker category:
• A+ (amyloid positive on PET)
• T₁ would need p-tau217/181 measurement (likely positive given clinical AD)
• T₂ (Tau PET) would show occipitoparietal tau deposition pattern (different from typical temporoparietal AD pattern)
• Classification: AD with PCA phenotype. This is biologically AD regardless of atypical clinical presentation.
Management: AChEI trial (donepezil); occupational therapy for visual aids; driving cessation; genetic testing if age <60; consider referral for anti-amyloid therapy clinical trial or commercial treatment (lecanemab) if early-stage.

8.2 AD Biomarkers — NIA-AA 2024 Revised Framework & Diagnostic Approach

8.2.1 Evolution of the Biomarker Paradigm

The understanding of AD has shifted from a clinicopathological model (diagnosis based on symptoms, confirmed at autopsy) to a biological model (diagnosis based on in vivo biomarkers identifying molecular pathology regardless of symptoms). This paradigm shift was formalized in the NIA-AA 2018 Research Framework (Jack CR Jr et al. Alzheimers Dement 2018) and further refined in the NIA-AA 2024 Revised Criteria (Jack CR Jr et al. Nat Med 2024).

Proposed AD timeline (Thientunyakit T et al. J Med Biol Eng 2022):

Phase	Duration (approx.)	Key Events
Biochemical phase	~10 years before symptoms	Proteopathic stress, Aβ clearance failure, initial tau phosphorylation, astrocyte activation (GFAP↑)
Cellular phase	~20 years before symptoms	Chronic neuroinflammation, synaptic loss, circuitry imbalance, neuronal death, brain atrophy
Clinical phase	Onset of symptoms	Memory/cognitive impairment, functional decline, behavioral changes

8.2.2 NIA-AA 2024 Revised Biomarker Framework: ATX(N)IVS

NIA-AA 2024 Revised Biomarker Categories (Jack CR Jr et al. Nat Med 2024)

Category	Designation	What It Measures	Biomarkers
Core 1 (Diagnostic)	A — Aβ proteinopathy	Amyloid plaque burden	CSF Aβ42 (or Aβ42/40 ratio), Amyloid PET, Plasma Aβ42/40
Core 1 (Diagnostic)	T₁ — Phosphorylated/secreted AD tau	Early soluble tau response to amyloid (reaction to Aβ plaques)	p-tau217 (best performer), p-tau181, p-tau231 (CSF or plasma)
Core 2 (Staging)	T₂ — AD tau aggregate proteinopathy	Physical tau tangles (NFT burden); tracks with neurodegeneration & symptoms	Tau PET (flortaucipir, MK-6240), MTBR-tau243 (CSF), p-tau205
Non-specific	N — Neurodegeneration/injury	Neuronal/axonal damage (not specific to AD)	NfL (CSF/plasma), anatomic MRI (hippocampal volume, cortical thickness), FDG-PET
Non-specific	I — Inflammation/immune activation	Astrocyte & microglial activation	GFAP (plasma/CSF), sTREM2 (CSF), YKL-40
Non-AD copathology	V — Vascular brain injury	Cerebrovascular disease contribution	MRI: WMH, lacunes, microbleeds, infarcts; CT: ischemic changes
Non-AD copathology	S — α-Synuclein	Lewy body co-pathology	αSyn-SAA (CSF/skin; seed amplification assay)

Key Distinction: T₁ vs. T₂ — Why It Matters

Feature	T₁ (Soluble Tau Response)	T₂ (Tau Aggregates)
What it reflects	Neuronal reaction to Aβ plaques; tau is phosphorylated and secreted	Physical NFT burden; tau is aggregated in neurons
Timing	Abnormal concurrently with amyloid PET (early)	Abnormal later, as tangles spread beyond MTL
Correlation	Correlates with amyloid burden	Correlates with neurodegeneration & cognitive decline
Clinical use	Diagnosis (confirms AD biology)	Staging & prognosis (predicts progression)
Key biomarkers	p-tau217, p-tau181, p-tau231	Tau PET, MTBR-tau243, p-tau205

8.2.3 Biomarker Testing Modalities

PET Imaging

PET Tracer	Target	Key Features
Amyloid PET (Florbetapir, Florbetaben, Flutemetamol, ¹¹C-PiB)	Fibrillar Aβ plaques	Visual read (positive/negative) + quantitative (Centiloid scale; CL >25 = amyloid positive). Validated against autopsy. High sensitivity & specificity (>90%). False positive: CAA, normal aging (low levels)
Tau PET (Flortaucipir [¹⁸F-AV-1451], ¹⁸F-MK-6240, ¹⁸F-PI-2620)	Tau NFT (primarily 3R+4R in AD)	Staging tool (Braak-like distribution). Tracks with cognition better than amyloid PET. Off-target binding in choroid plexus, basal ganglia (flortaucipir). MK-6240 has less off-target
FDG-PET	Cerebral glucose metabolism	Pattern-specific: AD (posterior cingulate/precuneus/temporoparietal hypometabolism); useful for differential diagnosis of dementia subtypes

CSF Biomarkers

Biomarker	Direction in AD	Performance	Notes
CSF Aβ42	↓ (sequestered in plaques)	Sn/Sp >90%	Use Aβ42/Aβ40 ratio for better accuracy (~50% fold difference normal vs abnormal)
CSF p-tau181	↑	Sn/Sp ~85–90%	Current clinical standard for T₁
CSF p-tau217	↑	Sn/Sp >95%	Superior to p-tau181; not yet widely clinically available
CSF t-tau	↑	Sn ~80%, Sp ~70%	Non-specific neurodegeneration marker; less useful than p-tau for AD diagnosis
CSF NfL	↑	Non-specific	Elevated in AD, FTD, ALS, MS, stroke; useful for monitoring neurodegeneration rate
CSF MTBR-tau243	↑	Emerging	Directly reflects tau aggregation (T₂); correlates with tau PET; research stage

Plasma Biomarkers — The Breakthrough

Plasma Biomarkers: Toward Blood-Based AD Diagnosis

Plasma Biomarker	Performance	Clinical Readiness
Plasma p-tau217	AUC 0.92–0.96 for Aβ+ discrimination; diagnostic accuracy equivalent to CSF biomarkers	Most advanced; FDA breakthrough device (PrecivityAD2, Lumipulse); the “90% Rule” — standalone Core 1 diagnostic when clearly abnormal
Plasma p-tau181	AUC 0.85–0.92	Available clinically (Quanterix Simoa); good but inferior to p-tau217
Plasma p-tau231	AUC 0.80–0.88; changes earliest	Research; may detect preclinical AD before p-tau181
Plasma Aβ42/40	AUC 0.80–0.87	Moderate performance alone; better in combination (hybrid ratios: p-tau217/Aβ42)
Plasma GFAP	Elevated from preclinical stage	Research/emerging; reflects astrocyte activation; increases early in AD continuum
Plasma NfL	Non-specific neurodegeneration	Available clinically; useful for monitoring, not diagnosis

The “90% Rule” for plasma p-tau217: When plasma p-tau217 falls in clearly abnormal or clearly normal ranges (avoiding the intermediate/grey zone), it achieves ≥90% concordance with amyloid PET and CSF, sufficient for standalone Core 1 biological diagnosis of AD without confirmatory PET or LP. This enables scalable screening in primary care and low-resource settings.

8.2.4 Chronobiological Biomarker Sequence

Biomarkers become abnormal in a predictable temporal sequence (Bjorkli C et al. Front Aging Neurosci 2020):

Astrocyte dysfunction (GFAP↑) — earliest detectable change
CSF Aβ42↓ (amyloid sequestration in plaques)
Amyloid PET+
Microglial activation (sTREM2↑, inflammation PET)
p-tau↑ (T₁ biomarkers: p-tau217, p-tau181)
FDG-PET hypometabolism
Hippocampal volume loss (MRI)
CSF t-tau↑, NfL↑
MRI structural atrophy (cortical thinning)
Cognitive decline (MoCA/MMSE drop)
Clinical functional impairment (ADL decline)

8.2.5 FDG-PET Metabolic Patterns in Neurodegenerative Dementia

FDG-PET Signature Patterns (Thientunyakit T, Muangpaisan W, Minoshima S. Semin Nucl Med 2025)

Disease	FDG-PET Hypometabolism Pattern	Key Distinguishing Feature
Typical AD	Posterior cingulate/precuneus + temporoparietal cortex	Bilateral, symmetric; earliest in posterior cingulate
lvPPA (logopenic)	Left lateral temporal + inferior parietal	Asymmetric left-sided (AD pathology)
PCA	Medial & lateral occipital + posterior parietal	Occipital involvement distinguishes from typical AD
bvFTD	Frontal (medial & lateral) + anterior temporal + caudate	Frontal-predominant; caudate involvement
svPPA (semantic)	Left anterior temporal pole	Asymmetric anterior temporal (often left > right)
nfvPPA (nonfluent)	Left inferior frontal (Broca’s area) + insula + premotor	Perisylvian left-sided
DLB	Temporoparietal + occipital	Occipital hypometabolism distinguishes from AD; “cingulate island sign” (preserved posterior cingulate)
PSP	Midbrain + medial frontal + caudate + thalamus	Subcortical + midline frontal
CBD	Asymmetric frontoparietal (contralateral to affected limb)	Marked asymmetry
Huntington’s disease	Caudate/putamen (early: may see hypermetabolism → late: hypometabolism)	Striatal-predominant

8.2.6 Diagnostic Pathway Algorithm

Based on Chêtelat G et al. Lancet Neurol 2020:

Three-Pathway Diagnostic Algorithm for Neurodegenerative Dementia

Pathway	Clinical Suspicion	Recommended First-Line Biomarker	Rationale
Pathway 1	AD suspected (amnestic presentation, typical age)	Amyloid PET or CSF Aβ/p-tau (or plasma p-tau217 if available)	Confirm or exclude AD biology
Pathway 2	Non-AD suspected (behavioral, language, or atypical presentations)	FDG-PET	Pattern-based differential diagnosis (FTD vs AD vs DLB vs PSP/CBD)
Pathway 3	Cognitive + movement disorder overlap	DaT-SPECT or MIBG scintigraphy	Confirm presynaptic dopaminergic deficit (DLB/PD) or cardiac sympathetic denervation

Practical approach in Thailand: Structural MRI (atrophy pattern) + cognitive testing → If AD suspected: plasma p-tau217 (when available) or CSF Aβ42/p-tau181 → If non-AD suspected: FDG-PET → If unclear: amyloid PET. For movement disorder + dementia: DaT-SPECT (available at major centers: Siriraj, Ramathibodi, Chulalongkorn).

NIA-AA vs IWG Diagnostic Criteria Comparison (Ossenkoppele R et al. Nat Med 2022)

Biomarker Profile	NIA-AA Classification	IWG Classification	5-Year Progression to MCI
A−T−	Not at risk	Not at risk	8.9%
A+T−	Preclinical AD pathological change	At-risk (not preclinical AD)	3.3%
A+T_MTL+	Preclinical AD	Preclinical AD	49.0%
A+T_NEO-T+	Preclinical AD	Preclinical AD, highest risk	53.3%

Key takeaway: A+T− individuals (amyloid positive but tau negative) have lower short-term risk of progression than A−T−. It is the combination of A+ with medial temporal or neocortical tau (T₂+) that signals high progression risk. This has major implications for clinical trial enrollment and treatment decisions.

8.2.7 Disease-Modifying Therapy: Anti-Amyloid Monoclonal Antibodies

Anti-Amyloid Immunotherapy Landscape (2023–2025)

Drug	Target	Trial	Key Results	FDA Status
Lecanemab (Leqembi®)	Aβ protofibrils (soluble aggregates)	CLARITY-AD (NEJM 2023) n=1,795; early AD (MCI/mild); 18 months	CDR-SB: −27% decline vs placebo (0.45 points; p<0.001). Amyloid PET: mean −59 CL (amyloid clearance). Brain volume loss greater with treatment (likely pseudo-atrophy from amyloid removal).	Full FDA approval (July 2023). IV infusion 10 mg/kg q2w
Donanemab (Kisunla™)	Aβ N-truncated pyroglutamate (deposited plaques)	TRAILBLAZER-ALZ 2 (JAMA 2023) n=1,736; early symptomatic AD; 76 weeks	CDR-SB: −29% in low/medium tau (−36% slowing). 47% reached amyloid negativity by 6 months. Benefit more pronounced in low/medium tau (T₂) subgroup. Time to next stage of disease: −39%.	FDA approved (July 2024). IV infusion; unique: stop dosing when amyloid cleared
Aducanumab (Aduhelm™)	Aβ aggregated forms	EMERGE/ENGAGE	Controversial; inconsistent results between two Phase 3 trials. Amyloid clearance confirmed. Withdrew from market 2024.	FDA accelerated approval 2021; withdrawn 2024

ARIA: Amyloid-Related Imaging Abnormalities

ARIA Monitoring Protocol

ARIA Type	Mechanism	Frequency	Monitoring	Management
ARIA-E (Edema/effusion)	Perivascular inflammation during amyloid clearance	Lecanemab: 12.6%; Donanemab: 24.0%	MRI at baseline, prior to 5th, 7th, 14th infusion (lecanemab); per protocol for donanemab	Most asymptomatic (75%). If symptomatic: hold treatment, monitor MRI, resume when resolved. Severe/symptomatic: discontinue
ARIA-H (Hemorrhage)	Microhemorrhages/superficial siderosis	Lecanemab: 17.3% (micro); Donanemab: 19.7%	Same MRI schedule as ARIA-E	<4 new microbleeds: may continue. ≥4 or superficial siderosis: hold/discontinue

Risk factors for ARIA: APOEε4 carriers (especially homozygotes: 32–36% ARIA-E rate), CAA, anticoagulant use, baseline microbleeds (>4). APOE genotyping is recommended before initiating anti-amyloid therapy for risk stratification and informed consent.

Eligibility Criteria for Anti-Amyloid Therapy (Practical):
• Include: Early symptomatic AD (MCI or mild dementia due to AD), confirmed amyloid-positive (PET or CSF/plasma biomarkers), CDR 0.5–1
• Exclude or high-risk: Moderate-severe dementia (CDR ≥2), >4 microbleeds or any superficial siderosis on MRI, anticoagulation, APOEε4 homozygotes (relative contraindication — discuss risk), significant CAA
• Thai context: Currently limited availability; lecanemab approved by Thai FDA (under special access); cost is a major barrier (~$26,500/year in US, pricing varies in Thailand); amyloid PET access mainly at Siriraj (PET center), Chulalongkorn, Ramathibodi

8.2.8 Symptomatic Pharmacotherapy

Cognitive Enhancers in AD

Drug Class	Drug	Dose	Indication	Key Side Effects
AChEI (Acetylcholinesterase Inhibitors)	Donepezil	5 mg/day × 4 weeks → 10 mg/day (max 23 mg)	Mild–severe AD; also DLB	GI (nausea, diarrhea), bradycardia, vivid dreams, muscle cramps
	Rivastigmine	Patch: 4.6 mg/24h → 9.5 → 13.3 mg/24h	Mild–moderate AD; PDD (only AChEI with PDD indication)	GI (less with patch), application site reactions
	Galantamine	8 mg/day → 16 → 24 mg/day (ER)	Mild–moderate AD	GI, allosteric nicotinic receptor modulation (dual mechanism)
NMDA antagonist	Memantine	5 mg/day → titrate to 20 mg/day	Moderate–severe AD (can combine with AChEI)	Dizziness, headache, confusion (rare)

Combination therapy (donepezil + memantine): The DOMINO trial (Howard et al. NEJM 2012) demonstrated that continuing donepezil and adding memantine in moderate-severe AD provided better cognitive and functional outcomes than either drug alone or placebo.

BPSD Pharmacotherapy

Symptom	First-Line	Second-Line	Important Cautions
Agitation/Aggression	Non-pharmacological first; Brexpiprazole (FDA-approved 2023 for AD agitation)	Low-dose risperidone (0.5–1 mg), quetiapine (25–100 mg)	FDA black box: antipsychotics increase mortality in elderly with dementia (~1.6–1.7×). Use lowest dose, shortest duration
Depression	SSRIs (Sertraline 50–100 mg, Escitalopram 5–10 mg)	Mirtazapine (if insomnia/appetite loss)	Avoid TCAs (anticholinergic burden worsens cognition)
Psychosis	Pimavanserin (selective 5-HT2A inverse agonist; FDA-approved for PD psychosis, studied in AD)	Quetiapine 25–50 mg, risperidone 0.25–0.5 mg	Avoid in DLB/PDD (neuroleptic sensitivity — see Section 8.3)
Insomnia	Sleep hygiene; trazodone 25–50 mg; Suvorexant 10 mg (orexin antagonist)	Melatonin 2–5 mg	Avoid benzodiazepines (falls, paradoxical agitation, cognitive worsening)
Apathy	Optimize AChEI; Methylphenidate 5–20 mg/day (ADMET 2, Lancet Neurol 2021)	Structured activities	Monitor for agitation, cardiovascular effects

Thai Context — Practical Prescribing: In Thailand, donepezil and memantine are on the NLEM (National List of Essential Medicines) and covered by government health insurance (UC, SSS, CSMBS). Rivastigmine patch and galantamine require special authorization. Brexpiprazole and pimavanserin are not yet available in Thailand. For BPSD, quetiapine and risperidone are most commonly used; always document rationale for antipsychotic use in elderly with dementia.

Q: A 72-year-old woman with 3-year progressive memory loss is diagnosed with mild AD (CDR 1, MMSE 21). Plasma p-tau217 is elevated. MRI shows bilateral hippocampal atrophy with 2 microbleeds. She is APOE ε3/ε4 heterozygous. Her family asks about lecanemab. What is your assessment and management plan?

Assessment:
• Diagnosis: Mild AD, biologically confirmed (A+ by plasma p-tau217, clinical syndrome consistent)
• Anti-amyloid therapy candidacy: Early-stage AD (CDR 1) — within treatment window. APOE ε3/ε4 heterozygote has intermediate ARIA risk (~15–20% ARIA-E). 2 microbleeds is below the >4 threshold.
Management plan:
1. Start donepezil 5 mg/day → titrate to 10 mg at 4 weeks (standard symptomatic treatment)
2. Lecanemab consideration: Patient is eligible based on: early AD, biomarker-confirmed, <4 microbleeds. However, discuss:
• Expected benefit: ~27% slowing of cognitive decline over 18 months
• ARIA risk: ~15% for ARIA-E as ε3/ε4 carrier, mostly asymptomatic but requires regular MRI monitoring
• Practical: IV infusion every 2 weeks; cost considerations; availability in Thailand
3. Baseline MRI with ARIA protocol (FLAIR, GRE/SWI for microbleed quantification)
4. Non-pharmacological: Cognitive stimulation, physical exercise (150 min/week), Mediterranean diet, social engagement, caregiver education
5. Address modifiable risk factors: Optimize blood pressure, diabetes control, hearing, depression
6. Advance care planning discussion while patient still has capacity

8.3 Dementia with Lewy Bodies (DLB)

8.3.1 Overview & Pathology

DLB is the second most common neurodegenerative dementia (~15–25% of autopsy-confirmed dementias), caused by cortical and limbic α-synuclein aggregation (Lewy bodies and Lewy neurites). Often co-occurs with AD pathology (Aβ plaques in ~50%; mixed DLB/AD). Median survival ~5–8 years from diagnosis.

α-Synuclein spreading pattern: Brainstem (locus coeruleus, dorsal motor nucleus of vagus) → midbrain (substantia nigra) → limbic (amygdala, cingulate) → neocortex. This parallels the Braak PD staging but with earlier/more prominent cortical involvement in DLB.

DLB vs. PDD: The One-Year Rule

Feature	DLB	PDD
Temporal relationship	Dementia onset within 1 year of or before parkinsonism	Dementia develops >1 year after established PD motor symptoms
Pathology	Identical (α-synuclein cortical Lewy bodies)	Identical
Spectrum	DLB and PDD are considered a spectrum of Lewy body dementia. The one-year rule is a practical clinical convention but both represent the same disease biology.

8.3.2 Diagnostic Criteria: McKeith 2017 Consensus (4th Report)

McKeith 2017 Diagnostic Criteria for DLB (Neurology 2017)

Essential feature: Progressive cognitive decline sufficient to interfere with normal social/occupational function. Prominent early memory impairment may not necessarily occur; deficits in attention, executive function, and visuospatial ability are typically prominent early.

Core Clinical Features (need ≥2 for probable, 1 for possible)

Core Feature	Description	Frequency
Fluctuating cognition	Pronounced variations in attention and alertness; episodes of staring, disorganized speech, “zoning out”. Distinguish from delirium	~60–80%
Recurrent visual hallucinations	Typically well-formed, detailed (people, animals). Often early in disease. Patient may have partial insight	~60–80%
REM sleep behavior disorder (RBD)	Dream enactment behavior (kicking, punching during sleep); confirmed by polysomnography. May precede cognitive decline by years/decades	~75–80%
Spontaneous parkinsonism	Bradykinesia, rigidity, resting tremor (less common than in PD). Gait disturbance. Not drug-induced	~70–85%

Indicative Biomarkers (count as Core feature equivalents)

Biomarker	Finding	Notes
DaT-SPECT / DaT-PET	Reduced dopamine transporter uptake in basal ganglia	Sn 78%, Sp 90% (vs AD). Does NOT distinguish DLB from PD/PDD/MSA/PSP
¹²³I-MIBG myocardial scintigraphy	Reduced cardiac uptake (H/M ratio <1.6)	Cardiac sympathetic denervation; Sn 69%, Sp 87%. Normal in AD, PSP, MSA
Polysomnography (PSG)	REM sleep without atonia (RWA)	Confirms RBD; highly specific for synucleinopathy

Supportive Features

Severe neuroleptic sensitivity, postural instability, repeated falls, syncope, autonomic dysfunction (orthostatic hypotension, urinary incontinence, constipation), hypersomnia, hyposmia, hallucinations in other modalities, systematized delusions (Capgras syndrome), depression, anxiety, apathy.

Diagnostic formula:

Probable DLB: ≥2 core features OR 1 core + ≥1 indicative biomarker
Possible DLB: 1 core feature alone OR ≥1 indicative biomarker alone

8.3.3 α-Synuclein Biomarkers — The SAA Revolution

α-Synuclein Seed Amplification Assay (αSyn-SAA)

The αSyn-SAA (also called RT-QuIC for α-synuclein) detects misfolded α-synuclein seeds in CSF or skin biopsies by amplifying trace amounts through cyclic fragmentation and regrowth, analogous to prion RT-QuIC.

Test	Sensitivity	Specificity	Notes
CSF αSyn-SAA	86–96% (DLB), 87–96% (PD)	95–100% (vs AD, controls)	Now incorporated in NIA-AA 2024 framework as “S” biomarker. Detects Lewy body copathology in AD patients
Skin biopsy αSyn-SAA	~89–96%	>95%	Less invasive alternative to CSF; detects α-synuclein in dermal autonomic nerve fibers

Clinical significance: αSyn-SAA transforms DLB/PD diagnosis from probabilistic (clinical criteria) to biological (molecular confirmation). Positive αSyn-SAA in a dementia patient with one core DLB feature virtually confirms Lewy body pathology. Also detects preclinical synucleinopathy in isolated RBD patients (prodromal DLB/PD).

Neuroimaging in DLB

Modality	Finding in DLB	Distinguishing from AD
Structural MRI	Relative preservation of medial temporal lobe/hippocampi	AD: prominent hippocampal atrophy. DLB: less MTL atrophy despite similar dementia severity
FDG-PET	Temporoparietal + occipital hypometabolism; “Cingulate island sign” (preserved posterior cingulate metabolism)	AD: posterior cingulate hypometabolism (no island sign); AD spares occipital cortex
Amyloid PET	Positive in ~50% (AD copathology)	Does NOT distinguish DLB from AD (both can be positive)
DaT-SPECT	Reduced striatal dopamine transporter uptake	Normal in AD (unless basal ganglia vascular disease)
EEG	Posterior dominant rhythm slowing; prominent posterior slow-wave activity	Supportive but not diagnostic

8.3.4 Treatment of DLB

Pharmacotherapy in DLB

Symptom Domain	Treatment	Evidence/Notes
Cognitive decline	Donepezil 5–10 mg/day (first-line) Rivastigmine patch (alternative)	AChEI more effective in DLB than AD; significant cholinergic deficit. Rivastigmine has best evidence for visual hallucinations
Visual hallucinations	Optimize AChEI first; Pimavanserin (if available)	If distressing despite AChEI: low-dose quetiapine (12.5–50 mg). AVOID typical antipsychotics and high-potency atypicals
Parkinsonism	Levodopa (cautious, low dose: start 50 mg TID)	Less effective than in PD; may worsen hallucinations/psychosis. Avoid dopamine agonists (worsen psychosis)
REM sleep behavior disorder	Melatonin 3–12 mg hs (first-line) Clonazepam 0.25–0.5 mg hs (if needed)	Melatonin preferred (fewer side effects, no fall risk). Clonazepam: risk of falls, sedation in elderly
Depression	SSRIs (sertraline, escitalopram)	Avoid TCAs (anticholinergic)
Autonomic dysfunction	Orthostatic hypotension: fludrocortisone, midodrine, droxidopa; Constipation: PEG, lubiprostone	Non-pharmacological first (compression stockings, salt, fluid)

CRITICAL: Neuroleptic Sensitivity in DLB

Up to 50% of DLB patients develop severe, potentially fatal neuroleptic sensitivity reactions:

Severe exacerbation of parkinsonism (rigidity, immobility, falls)
Impaired consciousness, delirium
Neuroleptic malignant syndrome (NMS) — even with atypical antipsychotics
Irreversible deterioration and death reported

Rules for antipsychotic use in DLB:

NEVER use typical antipsychotics (haloperidol, chlorpromazine) or high-potency atypicals (olanzapine, risperidone >0.5 mg) in DLB
If absolutely required: quetiapine (lowest D2 affinity) at lowest dose (12.5–25 mg), with close monitoring
Clozapine at ultra-low doses (6.25–25 mg) is the safest option but requires WBC monitoring (agranulocytosis risk)
Pimavanserin (5-HT2A inverse agonist, no D2 activity): theoretically ideal, FDA-approved for PD psychosis, data emerging in DLB
Always try optimizing AChEI first before considering any antipsychotic

Clinical Pearl — RBD as a Prodromal Biomarker: Isolated RBD (iRBD) is the strongest clinical predictor of future synucleinopathy. The NAPS study (Postuma et al. Brain 2019) showed that >90% of iRBD patients phenoconvert to PD, DLB, or MSA within 15 years (median conversion ~8 years). αSyn-SAA is positive in ~90% of iRBD patients, identifying them as having “prodromal Lewy body disease.” This has implications for future neuroprotective trial enrollment.

Q: A 74-year-old man presents with 1-year history of fluctuating alertness, recurrent formed visual hallucinations (seeing children in his room), and mild bradykinesia/rigidity. His wife reports he has been acting out violent dreams (kicking, shouting) for the past 5 years. MMSE 22/30, MoCA 18/30 (poor visuospatial and attention). MRI shows mild generalized atrophy with relative hippocampal preservation. What is the diagnosis, and how would you manage the hallucinations if they become distressing?

Diagnosis: Probable DLB (McKeith 2017).
• Core features present (3/4): fluctuating cognition, recurrent visual hallucinations, RBD (5-year history of dream enactment — predates cognitive decline, consistent with prodromal synucleinopathy), parkinsonism (bradykinesia + rigidity).
• Supportive: visuospatial/attention deficits on MoCA, relative hippocampal preservation on MRI.
• Recommended biomarker confirmation: DaT-SPECT (expect reduced uptake) or CSF αSyn-SAA (expect positive).
Management of hallucinations:
1. First: Start donepezil 5 mg → 10 mg (AChEI is first-line for both cognition AND hallucinations in DLB)
2. If hallucinations persist and are distressing:
• Quetiapine 12.5–25 mg at bedtime (lowest effective dose)
• NEVER use haloperidol, olanzapine, or risperidone >0.5 mg (neuroleptic sensitivity risk)
• Consider pimavanserin if available (no D2 activity)
3. For RBD: melatonin 6–12 mg at bedtime (first-line); bed safety measures (padding, floor mattress)
4. For parkinsonism: low-dose levodopa (50/12.5 mg TID) if functionally limiting, but may worsen hallucinations — balance carefully

8.4 Frontotemporal Dementia (FTD) Spectrum

8.4.1 Overview

FTD is the second most common cause of early-onset dementia (<65 years), accounting for ~10–20% of all degenerative dementias and up to 50% in those aged 45–65. Mean onset: 50–60 years. Characterized by progressive frontal and/or anterior temporal lobe degeneration with prominent behavioral, executive, and/or language dysfunction. Memory is relatively preserved early (unlike AD). Median survival ~6–8 years from symptom onset.

FTD Terminology & Classification

Level	Classification	Examples
Clinical syndrome	Behavioral/language phenotype	bvFTD, svPPA, nfvPPA, lvPPA, FTD-MND
Pathological substrate	FTLD + protein type	FTLD-tau (Pick, PSP, CBD), FTLD-TDP (Type A–E), FTLD-FUS
Genetic cause	Specific gene mutation	C9orf72, GRN, MAPT, TARDBP, VCP, CHMP2B

8.4.2 Behavioral Variant FTD (bvFTD)

Most common FTD subtype (~60% of FTD). Characterized by progressive personality change, behavioral dysregulation, and executive dysfunction.

FTDC Diagnostic Criteria for bvFTD (Rascovsky et al. Brain 2011)

Possible bvFTD: ≥3 of the following 6 features (progressive deterioration):

#	Feature	Examples
1	Early behavioral disinhibition	Socially inappropriate behavior, loss of manners/decorum, impulsive/reckless acts
2	Early apathy or inertia	Loss of motivation, interest, initiative; not due to depression
3	Early loss of sympathy/empathy	Diminished response to others’ needs/feelings, reduced social interest
4	Early perseverative/compulsive/ritualistic behavior	Stereotyped movements, compulsive/ritualistic behaviors, hoarding
5	Hyperorality & dietary changes	Altered food preferences (sweet craving), binge eating, oral exploration, increased alcohol/smoking
6	Neuropsychological profile	Executive/generation deficits with relative sparing of episodic memory and visuospatial function

Probable bvFTD: All of possible criteria + functional decline + imaging consistent (frontal/anterior temporal atrophy or hypometabolism).

Definite bvFTD: Histopathological confirmation or known pathogenic mutation.

Clinical Pearl — bvFTD Mimics and Phenocopies: Up to 30% of patients meeting possible bvFTD criteria may not have neurodegenerative disease (“phenocopy syndrome”). These patients show behavioral symptoms but lack progressive atrophy on serial MRI and have normal FDG-PET. Causes: late-onset psychiatric disorders (bipolar, OCD), brain injury, ASD. Tip: if MRI and FDG-PET are both normal after 2+ years, reconsider diagnosis. Serial neuropsychological testing showing stability rather than decline also suggests phenocopy.

8.4.3 Primary Progressive Aphasia (PPA)

PPA presents with insidious, progressive language impairment as the most prominent early feature (at least 2 years before other cognitive domains affected). Three canonical variants:

PPA Variants: Differential Diagnosis (Gorno-Tempini et al. Neurology 2011)

Feature	Semantic (svPPA)	Nonfluent/Agrammatic (nfvPPA)	Logopenic (lvPPA)
Core deficit	Loss of word/object meaning (semantic memory)	Effortful, halting speech with grammar errors (agrammatism) and/or apraxia of speech	Word-finding difficulty with impaired sentence repetition
Fluency	Fluent (empty speech, circumlocutory)	Nonfluent	Fluent but with frequent pauses
Naming	Severely impaired (confrontation naming)	Relatively preserved	Impaired
Repetition	Preserved (for single words)	May be impaired (for complex sentences)	Impaired (especially sentences/phrases)
Comprehension	Impaired for single words	Preserved for single words; impaired for complex grammar	Preserved for single words
Reading/Writing	Surface dyslexia/dysgraphia (regularization errors)	Agrammatic writing	Phonological errors
Atrophy pattern	Left anterior temporal pole (asymmetric, often “knife-edge”)	Left inferior frontal (Broca’s) + insula + premotor	Left temporoparietal junction (posterior perisylvian)
FDG-PET	Left anterior temporal	Left perisylvian frontal/insular	Left temporoparietal
Usual pathology	FTLD-TDP (Type C) — ~80%	FTLD-tau (4R; PSP or CBD) — ~60%	AD pathology — ~65% (not FTLD!)

Key Insight — lvPPA is Usually AD: Unlike svPPA and nfvPPA (which are FTD/FTLD), logopenic PPA is most commonly caused by Alzheimer’s disease pathology. Therefore, lvPPA patients are often amyloid PET positive and may respond to AChEI and potentially anti-amyloid therapy. Always check amyloid biomarkers in lvPPA.

8.4.4 FTD–ALS Continuum

FTD and ALS (amyotrophic lateral sclerosis) exist on a clinicopathological spectrum linked by TDP-43 proteinopathy:

Phenotype	Features	Pathology	Genetics
Pure ALS	UMN + LMN signs, no cognitive/behavioral features	TDP-43 (Type B mostly)	SOD1, FUS, TARDBP, C9orf72
ALS-FTD (ALS with cognitive/behavioral impairment)	ALS + executive dysfunction/behavioral change (may meet bvFTD criteria)	TDP-43 (Type B)	C9orf72 (most common), TARDBP
FTD-MND	bvFTD as primary presentation + MND features (fasciculations, UMN signs, EMG denervation)	FTLD-TDP (Type B)	C9orf72
Pure FTD (bvFTD)	Behavioral/cognitive only	FTLD-tau or FTLD-TDP	MAPT, GRN, C9orf72

Clinical Pearl — Screen for MND in bvFTD: Up to 15% of bvFTD patients develop MND features during their disease course. Always examine for UMN/LMN signs (fasciculations, hyperreflexia, Babinski, wasting) at every visit. EMG/NCS if suspected. FTD-MND has significantly worse prognosis (median survival 2–3 years) than pure bvFTD. C9orf72 expansion is the most common genetic cause of the FTD-ALS spectrum.

8.4.5 Genetics of FTD

FTD has the highest heritability of any neurodegenerative dementia (~40% have positive family history; ~10–20% have autosomal dominant mutations).

Major FTD Genes

Gene	Chromosome	Pathology	Clinical Features	Unique Characteristics
C9orf72	9p21	FTLD-TDP (Type A or B) + dipeptide repeat proteins	bvFTD, ALS, FTD-ALS, PPA, parkinsonism, psychosis (hallucinations, delusions common)	Most common genetic cause of both FTD and ALS; GGGGCC hexanucleotide repeat expansion (>30 repeats pathogenic); PCR-based repeat expansion testing required (not detected by gene panels/sequencing alone)
GRN	17q21	FTLD-TDP (Type A)	Asymmetric cortical atrophy; may mimic CBS, PPA (nfvPPA or mixed), or AD-like presentation	Haploinsufficiency mechanism; plasma progranulin levels can be used as screening biomarker (↓50%); variable phenotype even within families
MAPT	17q21	FTLD-tau (3R, 4R, or mixed)	bvFTD (classic), parkinsonism (PSP-like or CBS-like), semantic dementia	Tau-positive inclusions; more predictable phenotype than C9orf72/GRN; responds to anti-tau therapy targets
TARDBP	1p36	FTLD-TDP	ALS predominant, some FTD	Encodes TDP-43 itself; rare FTD cause
VCP	9p13	FTLD-TDP (Type D)	FTD + inclusion body myopathy + Paget’s disease of bone (IBMPFD)	Multi-system proteinopathy

8.4.6 PSP & CBS: The 4R Tauopathies

Progressive Supranuclear Palsy (PSP)

Feature	Details
Core phenotype (PSP-Richardson)	Vertical supranuclear gaze palsy (initially downgaze > upgaze), postural instability with early falls (backward), axial rigidity > limb, bradykinesia, frontal cognitive impairment, pseudobulbar affect
Other PSP phenotypes	PSP-P (parkinsonism predominant, mimics PD); PSP-F (frontal/bvFTD-like); PSP-CBS (corticobasal syndrome); PSP-SL (speech/language: nfvPPA); PSP-PGF (pure gait freezing)
Pathology	4R tau: globose NFT in subcortical nuclei, tufted astrocytes (pathognomonic), midbrain atrophy (“hummingbird sign”/“morning glory sign”)
Imaging	MRI: midbrain atrophy (AP diameter <14 mm), “hummingbird sign” sagittal, “morning glory sign” axial, superior cerebellar peduncle atrophy. FDG-PET: frontal + midbrain + caudate + thalamic hypometabolism
Treatment	No disease-modifying therapy. Levodopa trial (usually poor response, <30% improve). Amantadine for speech. PT for falls prevention. Anti-tau trials ongoing (semorinemab, bepranemab)

Corticobasal Syndrome (CBS) / Corticobasal Degeneration (CBD)

Feature	Details
Clinical features	Markedly asymmetric parkinsonism (rigidity, dystonia) + cortical signs: limb apraxia, cortical sensory loss, alien limb phenomenon, myoclonus. Progressive; usually one side affected first
Pathology	4R tau: ballooned/achromatic neurons, astrocytic plaques (pathognomonic), corticobasal inclusions. BUT: CBS phenotype can be caused by AD, PSP, TDP-43 — only ~50% have true CBD pathology
Imaging	MRI: asymmetric frontoparietal atrophy (contralateral to affected limbs). FDG-PET: asymmetric frontoparietal hypometabolism
Important note	CBS ≠ CBD. CBS is a clinical syndrome; CBD is a pathological diagnosis. Always consider AD as underlying pathology in CBS (check amyloid biomarkers)

8.4.7 FTD Treatment & Management

Symptom	Approach	Notes
Behavioral symptoms (disinhibition, agitation, compulsions)	SSRIs (trazodone 50–300 mg; sertraline 50–200 mg) — most evidence. Environmental modification	AChEI NOT recommended in FTD (may worsen behavior; no cholinergic deficit). Boxer et al. Lancet Neurol 2023: trazodone may help NPI scores
Apathy	Structured routines, activity scheduling. Stimulants (methylphenidate) limited evidence	Most treatment-resistant symptom
Language (PPA)	Speech-language therapy. Communication aids (picture boards, apps)	No pharmacological treatment proven effective
Parkinsonism (PSP, CBS)	Levodopa trial (low response rate). Botulinum toxin for focal dystonia	Dopamine agonists generally ineffective and may cause psychosis
Genetic counseling	Offer to all FTD patients, especially onset <60y, positive FHx, or atypical features	Pre-symptomatic testing available for C9orf72, GRN, MAPT. Follow Huntington protocol for disclosure

Clinical Pearl — AChEI in FTD: Unlike AD and DLB, FTD does NOT have a prominent cholinergic deficit. AChEI should be avoided as they may paradoxically worsen behavioral symptoms in bvFTD. If there is diagnostic uncertainty between AD and FTD, obtain amyloid biomarkers before starting AChEI. The exception: lvPPA (usually AD pathology) may benefit from AChEI.

Q: A 55-year-old woman presents with 2-year progressive personality change. Her husband reports she has become disinhibited (making inappropriate sexual comments to strangers), apathetic at home, compulsively eats sweets (gained 15 kg), and has lost empathy for her children. She scores 26/30 on MMSE (loses points on attention) but 18/30 on MoCA (poor clock draw, poor abstraction, poor verbal fluency). MRI shows bilateral frontal and anterior temporal atrophy. Her mother died at age 60 from ALS. What is the most likely diagnosis, what genetic test is most important, and what pharmacotherapy would you recommend?

Diagnosis: Probable bvFTD (Rascovsky 2011 criteria).
• ≥3 core features: (1) behavioral disinhibition, (2) apathy, (3) loss of empathy, (4) hyperorality/dietary changes, (5) executive dysfunction (neuropsychological profile: poor on MoCA executive tasks, relatively preserved MMSE).
• Functional decline + imaging support (frontal/anterior temporal atrophy).
Most important genetic test: C9orf72 GGGGCC hexanucleotide repeat expansion testing (PCR-based, NOT standard gene panel/sequencing).
• Rationale: family history of ALS in mother; C9orf72 is the #1 genetic cause of both FTD and ALS and the FTD-ALS continuum. Autosomal dominant inheritance.
• Also examine for MND signs (fasciculations, hyperreflexia, wasting) at every visit given family history.
Pharmacotherapy:
1. Trazodone 50 mg → titrate to 150–300 mg/day (for disinhibition, compulsive behaviors)
2. Sertraline 50–100 mg/day (alternative SSRI for behavioral symptoms)
3. Do NOT start AChEI (may worsen behavioral symptoms in bvFTD)
4. Genetic counseling for patient and family members
5. Caregiver support and education (high burden disease)

8.5 Vascular Cognitive Impairment & Vascular Dementia

8.5.1 Classification

Vascular cognitive impairment (VCI) encompasses all cognitive disorders attributable to cerebrovascular disease, from mild VCI to vascular dementia (VaD). VaD is the second most common cause of dementia overall (after AD), and mixed dementia (AD + VCI) is extremely common, especially in the elderly.

Subtype	Mechanism	Clinical Features	Imaging
Multi-infarct dementia	Multiple cortical/subcortical infarcts	Stepwise decline; focal neurological signs; temporal relation to stroke events	Multiple territorial infarcts
Strategic single-infarct dementia	Infarct in critical location	Acute cognitive decline after single stroke (thalamic, PCA territory, angular gyrus, caudate, hippocampal)	Single infarct in strategic location
Subcortical ischemic VaD (Binswanger’s)	Small vessel disease (SVD) → lacunes + white matter disease	Executive dysfunction, processing speed ↓, apathy, gait disturbance, urinary symptoms. Most common form of VaD	Extensive WMH (Fazekas 3), lacunes, microbleeds, perivascular spaces
CADASIL	NOTCH3 mutation → hereditary SVD	Migraine with aura (onset ~30s), recurrent strokes (onset ~40–50s), mood disturbance, subcortical dementia	Anterior temporal pole + external capsule WMH (pathognomonic); microbleeds
Post-hemorrhagic VCI	ICH, SAH, or chronic subdural	Cognitive impairment following hemorrhage; strategic location-dependent	Evidence of prior hemorrhage
CAA-related cognitive impairment	Cerebral amyloid angiopathy	Lobar microbleeds, cortical superficial siderosis, episodic cognitive events (TFNEs)	Posterior-predominant lobar microbleeds/siderosis (Boston criteria v2.0)

8.5.2 Diagnostic Criteria (VASCOG 2014)

Major VCI (VaD): (1) Cognitive impairment in ≥1 domain sufficient to impair ADL, (2) Evidence of cerebrovascular disease on neuroimaging, (3) Temporal relationship (onset within 3 months of stroke OR stepwise/fluctuating course), (4) No other cause more likely.

Mild VCI: Same criteria but cognitive impairment does not impair ADL independence.

Clinical Pearl — SVD Burden Assessment on MRI: The total SVD score (Staals et al. 2014) assigns 1 point each for: (1) ≥1 lacune, (2) Fazekas periventricular WMH score 3, (3) ≥1 cerebral microbleed, (4) moderate-severe perivascular spaces in basal ganglia. Total score 0–4; score ≥3 associated with significantly increased stroke recurrence, cognitive decline, and mortality. This is a practical, MRI-based risk stratification tool.

8.5.3 VaD Treatment

Secondary stroke prevention: Antiplatelet therapy (aspirin, clopidogrel), anticoagulation (if AF), statin, antihypertensives (target BP <130/80 in established VCI)
Risk factor control: Diabetes (HbA1c <7%), smoking cessation, weight management, physical activity
Cognitive enhancement: AChEI (donepezil, galantamine) have modest benefit in VaD and mixed dementia (Donepezil 308 Study, Lancet 2004). Memantine may help. Thai NLEM covers donepezil for VaD
Depression: Common in VCI (~30%); SSRIs first-line

8.6 Normal Pressure Hydrocephalus (NPH)

8.6.1 Overview

NPH is a potentially reversible cause of dementia, characterized by the classic triad (Hakim-Adams syndrome): gait disturbance, dementia, urinary incontinence. Important because VP shunt placement can significantly improve symptoms when correctly identified. Prevalence: ~2–6% of all dementias.

8.6.2 Clinical Features

NPH Classic Triad (“Wet, Wacky, Wobbly”)

Feature	Description	Order of Onset & Response to Shunt
Gait disturbance	Magnetic gait (feet stuck to floor), wide-based, shuffling, short steps, difficulty turning. Gait apraxia. Falls.	Usually FIRST to appear; BEST response to shunting (~80% improve)
Dementia	Subcortical pattern: executive dysfunction, psychomotor slowing, impaired attention. Memory recall impaired but recognition relatively preserved (≠ AD where encoding fails)	Second; moderate response (~50–70% improve)
Urinary incontinence	Initially urinary urgency/frequency, then frank incontinence	Third; variable response

Note: Complete triad present in only ~50–60%. Isolated gait disturbance may be the only early sign. Always consider NPH in elderly patients with unexplained gait difficulty + ventriculomegaly.

8.6.3 Diagnosis

Investigation	Findings	Notes
CT/MRI brain	Ventriculomegaly (Evans’ index >0.3) disproportionate to sulcal atrophy; DESH (disproportionately enlarged subarachnoid-space hydrocephalus); callosal angle <90°	DESH pattern: tight high-convexity sulci + widened Sylvian fissures + ventriculomegaly
CSF tap test (large-volume LP)	Remove 30–50 mL CSF; assess gait at 1h, 24h, 72h	Positive: ≥10% improvement in gait speed or steps. PPV for shunt response ~90%; but NPV only ~50% (false negatives common)
Extended lumbar drainage (ELD)	Continuous CSF drainage (~150–200 mL/day) for 3–5 days	Higher sensitivity than tap test; more predictive of shunt response. Used when tap test equivocal
Opening pressure	Normal or high-normal (≤18 cmH₂O; some allow up to 24)	“Normal pressure” — but pressure is “inappropriately normal” for the degree of ventriculomegaly (Wischke-Laplace law)

8.6.4 Treatment

VP (ventriculoperitoneal) shunt is the definitive treatment. Programmable valve preferred (allows pressure adjustment). LP shunt is an alternative. Endoscopic third ventriculostomy (ETV) has limited evidence in iNPH.

Predictors of good shunt response: Gait as predominant symptom, short symptom duration (<6 months), positive tap test, DESH pattern on MRI, known cause (sSNPH — post-SAH, post-meningitis).

Complications: Subdural hematoma/hygroma (10–15%), infection (3–5%), over-drainage (low-pressure headache), shunt malfunction.

Clinical Pearl — NPH vs. Other Gait Disorders: The gait of NPH (“magnetic”/gait apraxia) must be distinguished from: (1) Parkinsonism (PD, PSP — more rigidity/bradykinesia, response to levodopa), (2) Subcortical VaD (similar gait but vascular risk factors, WMH on MRI without DESH pattern), (3) Cervical spondylotic myelopathy (spasticity, hyperreflexia, Babinski). Key differentiator: DESH pattern on MRI + positive CSF tap test.

8.7 Reversible Dementias & Rapidly Progressive Dementia (RPD)

8.7.1 Reversible Causes of Dementia

Approximately 5–15% of dementias have a potentially reversible component. Every new dementia evaluation should screen for these “dementia mimics.”

Reversible Dementia — Mandatory Workup

Category	Cause	Screening Test	Treatment
Metabolic	Hypothyroidism	TSH, free T4	Levothyroxine
	Vitamin B12 deficiency	Serum B12, methylmalonic acid, homocysteine	B12 replacement (IM or high-dose oral)
	Hepatic encephalopathy	LFTs, ammonia	Lactulose, rifaximin
	Uremic encephalopathy	BUN, creatinine	Dialysis
	Hypo/hypernatremia, hypercalcemia	Electrolytes, calcium	Correction
Infectious	Neurosyphilis	RPR/VDRL, FTA-ABS; CSF VDRL if positive	IV penicillin G × 14 days
	HIV-associated neurocognitive disorder	HIV test	ART
	Chronic CNS infection (TB, fungal)	CSF analysis	Specific antimicrobial
Structural	NPH	CT/MRI brain	VP shunt
	Chronic subdural hematoma	CT/MRI brain	Surgical evacuation
	Brain tumor (especially frontal meningioma)	MRI brain with contrast	Surgery ± adjuvant therapy
Psychiatric	Depression (pseudodementia)	PHQ-9, geriatric depression scale	Antidepressants, psychotherapy
Toxic	Medications (anticholinergics, benzodiazepines, opioids)	Medication review	Discontinue/substitute offending agent
	Alcohol-related cognitive impairment / Wernicke-Korsakoff	History, thiamine level	Thiamine replacement; abstinence
Autoimmune	Autoimmune encephalitis (anti-LGI1, anti-CASPR2, anti-NMDAR)	Serum/CSF autoimmune encephalitis panel	Immunotherapy (steroids, IVIg, PLEX, rituximab)

8.7.2 Rapidly Progressive Dementia (RPD)

RPD is defined as dementia developing within weeks to months (usually <1–2 years from onset to severe impairment). It represents a neurological emergency requiring urgent evaluation.

Differential Diagnosis of RPD — “VITAMINS” Mnemonic

Category	Causes	Key Features
V — Vascular	Multi-infarct, cerebral vasculitis (PACNS), cerebral venous thrombosis	Stepwise decline, focal signs, stroke risk factors
I — Infectious	CJD (prion), PML, HIV, Whipple disease	Myoclonus + rapid dementia → think prion
T — Toxic/metabolic	Wernicke, hepatic/uremic, heavy metals, bismuth	History of exposure, systemic signs
A — Autoimmune	Autoimmune encephalitis, Hashimoto encephalopathy, neurosarcoidosis, CNS lupus	Subacute onset, seizures, psychiatric features, CSF pleocytosis
M — Metastatic/Neoplastic	Carcinomatous meningitis, paraneoplastic (anti-Hu, anti-CV2), CNS lymphoma, gliomatosis cerebri	Weight loss, known malignancy, CSF cytology
I — Iatrogenic	Medication-induced (chemotherapy, immunosuppressants), post-radiation	Temporal relationship to treatment
N — Neurodegenerative	CJD, rapidly progressive AD (“rpAD”), DLB, FTD	rpAD is a diagnosis of exclusion after prion workup
S — Systemic/Seizures	Non-convulsive status epilepticus, systemic illness (sepsis, HLH)	EEG essential; may be treatable cause

8.7.3 Prion Diseases / Creutzfeldt-Jakob Disease (CJD)

CJD is the prototypical prion disease — a transmissible spongiform encephalopathy caused by conformational change of normal cellular prion protein (PrP^C) to pathological PrP^Sc.

Types of CJD

Type	Frequency	Onset	Features
Sporadic CJD (sCJD)	~85%	Mean ~65y	Rapidly progressive dementia + myoclonus + ataxia. Median survival 5 months. Akinetic mutism as end-stage
Genetic CJD	~10–15%	Variable	PRNP mutations (E200K most common); may have longer course. Includes FFI (D178N + 129M) and GSS (P102L)
Variant CJD (vCJD)	Rare	Young (median 28y)	BSE-related; psychiatric onset, painful sensory symptoms, later dementia + movement disorder. “Pulvinar sign” on MRI
Iatrogenic CJD	Very rare	Variable	Dura mater grafts, growth hormone, corneal transplants, contaminated neurosurgical instruments

Diagnosis of sCJD

Test	Finding	Performance
MRI DWI/FLAIR	Cortical ribboning (high signal in cortex) + caudate/putamen signal	Sn 92–96%, Sp 93–94%. Best initial diagnostic test. DWI more sensitive than FLAIR
CSF RT-QuIC	Prion seed amplification assay (positive)	Sn 92–95%, Sp ~100%. Now the gold standard antemortem test. Included in CDC 2018 diagnostic criteria
CSF 14-3-3 protein	Elevated	Sn ~85%, Sp ~65%. Non-specific (elevated in stroke, encephalitis). Largely supplanted by RT-QuIC
CSF t-tau	Markedly elevated (>1,150 pg/mL)	Sn ~85%, Sp ~85%. Better than 14-3-3. Very high t-tau (>10,000) strongly suggests CJD
EEG	Periodic sharp wave complexes (PSWC) at ~1 Hz	Sn 64%, Sp 91%. Late finding; may be absent in early disease. Seen in ~60% of sCJD
Brain biopsy/autopsy	Spongiform change, PrP^Sc immunohistochemistry	Definitive diagnosis. Rarely done antemortem (RT-QuIC has reduced need)

Clinical Pearl — RPD Workup Protocol: For any patient with subacute cognitive decline over weeks-months, the initial workup should include: (1) MRI brain with DWI (rule out CJD, stroke, mass), (2) EEG (rule out NCSE, CJD periodic complexes), (3) CSF: cell count, protein, glucose, cytology, 14-3-3/RT-QuIC, autoimmune encephalitis panel, (4) Blood: CBC, CMP, TSH, B12, HIV, RPR, autoimmune encephalitis panel, paraneoplastic antibodies, (5) CT chest/abdomen/pelvis if paraneoplastic suspected. Treatable causes (autoimmune, infectious, metabolic) must be identified urgently.

Q: A 67-year-old woman presents with 2-month rapidly progressive cognitive decline, myoclonus, visual disturbance, and gait ataxia. MRI DWI shows cortical ribboning in bilateral parietal and occipital cortex with caudate hyperintensity. EEG shows generalized periodic sharp wave complexes. CSF 14-3-3 is positive and RT-QuIC is positive. What is the diagnosis and prognosis?

Diagnosis: Probable sporadic CJD (meets CDC 2018 criteria).
• Rapidly progressive dementia + myoclonus + ataxia + visual disturbance (Heidenhain variant with occipital involvement)
• MRI: cortical ribboning + caudate signal on DWI (highly characteristic)
• EEG: periodic sharp wave complexes
• CSF RT-QuIC positive (Sn 92–95%, Sp ~100%) — essentially confirms prion disease antemortem
Prognosis: Devastating. Median survival for sCJD is ~5 months (90% die within 1 year). No disease-modifying treatment exists.
Management:
1. Palliative care discussion and goals of care planning (immediate priority)
2. Symptomatic: clonazepam for myoclonus (0.5–2 mg), sodium valproate alternative
3. Infection control precautions for surgical instruments (prion-specific decontamination); standard precautions sufficient for routine care
4. PRNP sequencing to exclude genetic form (important for family counseling)
5. Report to national CJD surveillance (Thai Department of Disease Control)
6. Family support and counseling

8.8 References & Key Guidelines

Key References & Guidelines

Biomarkers & Diagnostic Frameworks

Jack CR Jr et al. NIA-AA Research Framework: Toward a biological definition of Alzheimer’s disease. Alzheimers Dement 2018;14(4):535–562.
Jack CR Jr et al. Revised criteria for diagnosis and staging of Alzheimer’s disease: Alzheimer’s Association workgroup. Nat Med 2024;30(4):999–1016. [NIA-AA 2024 Revised Criteria]
Thientunyakit T et al. Molecular neuroimaging in Alzheimer’s disease. J Med Biol Eng 2022;42:301–310.
Bjorkli C et al. Biomarkers of Alzheimer’s disease: a chronobiological approach. Front Aging Neurosci 2020;12:471.
Ossenkoppele R et al. Amyloid and tau PET-positive cognitively unimpaired individuals are at high risk for future cognitive decline. Nat Med 2022;28(11):2381–2387.
Chêtelat G et al. Amyloid-PET and ¹⁸F-FDG-PET in the diagnostic investigation of Alzheimer’s disease and other dementias. Lancet Neurol 2020;19(11):951–962.
Thientunyakit T, Muangpaisan W, Minoshima S. FDG-PET patterns in neurodegenerative dementia. Semin Nucl Med 2025 (in press).

Clinical Trials & Landmark Studies

van Dyck CH et al. Lecanemab in early Alzheimer’s disease. N Engl J Med 2023;388(1):9–21. [CLARITY-AD]
Sims JR et al. Donanemab in early symptomatic Alzheimer disease: the TRAILBLAZER-ALZ 2 randomized clinical trial. JAMA 2023;330(6):512–527.
Howard R et al. Donepezil and memantine for moderate-to-severe Alzheimer’s disease. N Engl J Med 2012;366:893–903. [DOMINO]
Rosenberg PB et al. Safety and efficacy of methylphenidate for apathy in Alzheimer’s disease: a randomized, placebo-controlled trial (ADMET 2). Lancet Neurol 2021;20(10):816–825.
Venegas C et al. Microglia-derived ASC specks cross-seed amyloid-β in Alzheimer’s disease. Nature 2017;552:355–361.
Liddelow SA et al. Neurotoxic reactive astrocytes are induced by activated microglia. Nature 2017;541:481–487.
Postuma RB et al. Risk and predictors of dementia and parkinsonism in idiopathic REM sleep behaviour disorder: a multicentre study. Brain 2019;142(3):744–759. [NAPS]

Diagnostic Criteria & Consensus

McKeith IG et al. Diagnosis and management of dementia with Lewy bodies: fourth consensus report. Neurology 2017;89:88–100.
Rascovsky K et al. Sensitivity of revised diagnostic criteria for the behavioural variant of frontotemporal dementia. Brain 2011;134(Pt 9):2456–2477. [FTDC Criteria]
Gorno-Tempini ML et al. Classification of primary progressive aphasia and its variants. Neurology 2011;76(11):1006–1014.
Höglinger GU et al. Clinical diagnosis of progressive supranuclear palsy: the movement disorder society criteria. Mov Disord 2017;32(6):853–864. [MDS-PSP Criteria]
Sachdev P et al. Diagnostic criteria for vascular cognitive disorders: a VASCOG statement. Alzheimer Dis Assoc Disord 2014;28(3):206–218.
Zerr I et al. Updated clinical diagnostic criteria for sporadic Creutzfeldt-Jakob disease. Brain 2009;132(Pt 10):2659–2668.

Thai Context & Regional Data

Muangpaisan W et al. Dementia prevalence in Thailand: a systematic review. Thai Journal of Neurology (various years).
Thai Dementia Guidelines (Royal College of Physicians of Thailand / Neurological Society of Thailand) — 2020 update.
NLEM (National List of Essential Medicines): Donepezil, memantine covered; rivastigmine patch requires special authorization.
Witsarut Nanthasi. World of Dementia (Siriraj Neurology Lecture Series). Faculty of Medicine Siriraj Hospital, Mahidol University, 2026.
Muangpaisan W. Biomarkers in Dementia: The Evolution to Precision. SiACG Conference, Siriraj Hospital, 2026.

9. Sleep Disorders

This section provides a comprehensive subspecialist-depth review of sleep disorders relevant to neurological practice. Coverage includes obstructive sleep apnea (PALM endotyping, PSG interpretation, CPAP/hypoglossal nerve stimulation/SURMOUNT-OSA pharmacotherapy, cardiovascular consequences, glymphatic system), narcolepsy (orexin pathophysiology, ICSD-3 criteria, MSLT protocol, complete pharmacotherapy including sodium oxybate/pitolisant/solriamfetol), REM sleep behavior disorder (as the strongest prodromal biomarker of synucleinopathy — iRBD phenoconversion data, αSyn-SAA, drug-induced RBD), NREM parasomnias (differential with SHE/nocturnal seizures), chronic insomnia (CBT-I components, DORA/Z-drug/melatonin agonist pharmacotherapy), circadian rhythm disorders (DSWPD, shift work, jet lag, Non-24), restless legs syndrome (IRLSSG criteria, iron pathway, augmentation management, α2δ ligand-first approach), sleep-related epilepsy (SHE), and sleep disorders in neurological disease.

9.1 Obstructive Sleep Apnea (OSA) — Comprehensive Review

9.1.1 Epidemiology & Pathophysiology

OSA is the most common sleep-related breathing disorder, affecting ~15–30% of men and ~10–15% of women (higher with obesity epidemic). Prevalence in Thailand: ~11.4% in urban adults (Bangkok Metropolitan Sleep Study). Markedly underdiagnosed — up to 80% of moderate-severe OSA cases remain unrecognized.

Pathophysiology: The Multi-Level Model

Endotype (Pathophysiological Trait)	Mechanism	Clinical Implication
Anatomical compromise (V_passive)	Small/collapsible pharyngeal airway: retrognathia, macroglossia, tonsillar hypertrophy, obesity (fat deposition in parapharyngeal space), craniofacial narrowing	Most important factor (~70% of patients). Targeted by CPAP, MAD, surgery, weight loss
High loop gain	Oversensitive ventilatory control system: small ↑CO₂ → exaggerated ventilatory response → overshoot → undershoot → cyclical collapse	Explains central/mixed apnea patterns; may benefit from O₂, acetazolamide, adaptive servo-ventilation (ASV) in some cases
Low arousal threshold	Easily aroused from sleep by minor respiratory events → prevents compensatory neuromuscular response → fragmented sleep	~30–50% of OSA patients; may benefit from sedatives (low-dose trazodone, eszopiclone) to reduce arousals — counterintuitive but evidence-supported
Poor pharyngeal muscle responsiveness	Inadequate genioglossus/dilator muscle compensation during sleep	Target for hypoglossal nerve stimulation (Inspire); desipramine, atomoxetine + oxybutynin combination (PALM trial concept)

Clinical Pearl — OSA Endotyping: The PALM model (P_crit, Arousal threshold, Loop gain, Muscle responsiveness) explains why not all OSA patients respond equally to CPAP. Future precision medicine in OSA aims to match therapy to the dominant endotype: anatomical → CPAP/surgery; high loop gain → O₂/acetazolamide; low arousal threshold → sedative; poor muscle → hypoglossal nerve stimulation. The Wellman et al. AJRCCM 2011 framework established this endotyping paradigm.

9.1.2 Diagnosis

ICSD-3 Diagnostic Criteria for OSA

Criterion A (symptomatic): Presence of ≥1 symptom (EDS, non-restorative sleep, fatigue, insomnia, snoring, witnessed apneas, nocturnal gasping/choking) AND PSG/HSAT showing AHI ≥5/h (predominantly obstructive events).

Criterion B (asymptomatic): AHI ≥15/h regardless of symptoms (associated with cardiovascular risk even without symptoms).

Severity	AHI	Associated Risk
Mild	5–14/h	EDS, cognitive impairment, mild cardiovascular risk elevation
Moderate	15–29/h	Significant cardiovascular risk; hypertension; arrhythmia risk
Severe	≥30/h	High cardiovascular risk; resistant HTN; atrial fibrillation; stroke; sudden cardiac death

Screening Tools

Tool	Components	Interpretation
STOP-BANG	Snoring; Tired; Observed apnea; Pressure (HTN); BMI >35; Age >50; Neck >40 cm; Gender (male)	≥3: high risk; ≥5: very high risk for moderate-severe OSA. Sn 90%, Sp 36% at ≥3 (high sensitivity, low specificity)
Epworth Sleepiness Scale (ESS)	8 situational sleepiness questions (0–24)	>10: excessive daytime sleepiness; >16: severe. Subjective; poor correlation with AHI
Berlin Questionnaire	3 categories: snoring, daytime fatigue, BMI/HTN	≥2 positive categories: high risk

Polysomnography (PSG) vs. Home Sleep Apnea Test (HSAT)

Feature	In-Lab PSG (Level 1)	HSAT (Level 3)
Channels	EEG, EOG, EMG, ECG, airflow (nasal pressure + thermistor), respiratory effort (chest/abdomen belts), SpO₂, body position, video	Airflow, respiratory effort, SpO₂ ± body position (no EEG)
Scoring metric	AHI (events per hour of sleep)	REI (Respiratory Event Index: events per hour of recording time) — may underestimate severity
Indication	Gold standard; required for: central sleep apnea suspicion, narcolepsy/parasomnia (MSLT), complex patients (CHF, COPD, neuromuscular, opioid use)	Appropriate for high pre-test probability of moderate-severe OSA in patients without significant comorbidities
Limitation	Cost, waiting times, first-night effect	Underestimates AHI; cannot detect central events reliably; misses REM-related OSA if low REM time

Key PSG Event Definitions (AASM 2024 Scoring Manual)

Event	Definition
Obstructive Apnea	≥90% reduction in airflow ≥10 seconds with continued respiratory effort
Central Apnea	≥90% reduction in airflow ≥10 seconds without respiratory effort
Mixed Apnea	Begins as central, ends with obstructive effort
Hypopnea (Recommended)	≥30% reduction in airflow ≥10 seconds + ≥3% O₂ desaturation OR arousal
Hypopnea (Acceptable)	≥30% reduction in airflow ≥10 seconds + ≥4% O₂ desaturation
RERA	Respiratory Effort-Related Arousal: increasing effort leading to arousal, not meeting apnea/hypopnea criteria
RDI	AHI + RERAs (used for Upper Airway Resistance Syndrome: RDI ≥5 but AHI <5)

9.1.3 Cardiovascular & Systemic Consequences of OSA

System	Consequence	Mechanism
Cardiovascular	Resistant hypertension (most common CV consequence; 50–80% of resistant HTN have OSA), atrial fibrillation (×2–4 risk), heart failure, coronary artery disease, aortic dissection	Intermittent hypoxia → sympathetic activation, oxidative stress, endothelial dysfunction, systemic inflammation
Cerebrovascular	Stroke risk ×2–3; worse stroke outcomes; cognitive impairment	Nocturnal BP surges, AF, paradoxical embolism (PFO + apnea-related right-to-left shunt)
Metabolic	Insulin resistance, T2DM (×1.5–2 risk), metabolic syndrome	Intermittent hypoxia → sympathetic activation → cortisol ↑, adipokine dysregulation
Pulmonary	Pulmonary hypertension (10–20% of severe OSA), obesity hypoventilation syndrome (OHS) overlap	Chronic intermittent hypoxia → pulmonary vasoconstriction → vascular remodeling
Neuropsychiatric	EDS, impaired vigilance, ×2.5 MVA risk, depression, cognitive decline, ↑ AD biomarker abnormalities	Sleep fragmentation, intermittent hypoxia → hippocampal damage, glymphatic clearance impairment

Clinical Pearl — OSA and Glymphatic System: The glymphatic system (brain’s waste clearance pathway) is most active during deep sleep. OSA causes sleep fragmentation and intermittent hypoxia, impairing glymphatic Aβ clearance. Multiple studies show OSA is associated with earlier amyloid deposition and accelerated cognitive decline. CPAP treatment may partially reverse this — a bridge between sleep medicine and the dementia biomarker framework (Section 8). This is relevant for your neurology and stroke/dementia practice.

9.1.4 Treatment

OSA Treatment Algorithm

Treatment	Indication	Details
CPAP	First-line for all moderate-severe OSA; mild OSA with symptoms	Goal: AHI <5/h on therapy. Adherence target: ≥4h/night ≥70% nights (CMS definition). Auto-CPAP (APAP) preferred for most (auto-adjusting 4–20 cmH₂O). Fixed CPAP if central apneas emerge on auto. Heated humidification reduces nasal dryness. Mask fitting crucial (nasal > full-face for adherence unless mouth breathing).
BiPAP	CPAP intolerance (high pressure needs), OHS, COPD-OSA overlap, neuromuscular	IPAP/EPAP differential; BiPAP-ST for OHS/hypoventilation (backup rate). Average volume-assured pressure support (AVAPS) for OHS.
Mandibular Advancement Device (MAD)	Mild-moderate OSA; CPAP intolerance; patient preference	Custom-fitted by sleep dentist preferred over OTC. AHI reduction ~50%. Better adherence than CPAP but less efficacy for severe OSA.
Hypoglossal Nerve Stimulation (Inspire)	Moderate-severe OSA (AHI 15–65); CPAP intolerant; BMI <40 (updated to <40); no complete concentric collapse on DISE	STAR Trial (Strollo et al. NEJM 2014): 68% AHI reduction at 12 months. Implanted device stimulates CN XII (genioglossus) synchronized with respiration. FDA approved 2014. Not yet available in Thailand but expanding in Asia-Pacific.
Positional therapy	Supine-predominant OSA (AHI supine ≥2× non-supine)	Positional devices (NightBalance, tennis ball technique). Effective for ~25% of OSA patients with positional component.
Weight loss	All OSA patients with BMI ≥25	10% weight loss → ~26% AHI reduction. Bariatric surgery: 75% AHI reduction but rarely cures OSA. SURMOUNT-OSA (Malhotra et al. NEJM 2024): tirzepatide 10–15 mg weekly → AHI reduction of ~50–60% in obese OSA patients (with or without CPAP); weight loss ~18–20%.
Pharmacotherapy (emerging)	Adjunct or specific endotype targeting	PALM combination: atomoxetine + oxybutynin (NRI + antimuscarinic): ↓AHI by ~50% in selected patients (targets muscle responsiveness endotype). Acetazolamide for high loop gain. Sulthiame (carbonic anhydrase inhibitor): Phase 3 positive 2024.

Surgical Options

Surgery	Mechanism	Indication
UPPP (Uvulopalatopharyngoplasty)	Removes redundant oropharyngeal tissue	Retropalatal obstruction on DISE; ~50% success rate (Sher criteria); less predictable than CPAP
Tonsillectomy ± adenoidectomy	Removes tonsillar obstruction	First-line in pediatric OSA; adults with tonsillar hypertrophy (Grade 3–4)
Maxillomandibular advancement (MMA)	Advances maxilla + mandible 10–12 mm → enlarges retrolingual/retropalatal airway	Severe OSA with craniofacial restriction; most effective surgery (~85–90% success); significant morbidity
Tracheostomy	Bypasses upper airway entirely	Life-threatening OSA refractory to all other treatments; last resort (100% effective for OSA by definition)

Clinical Pearl — OSA in Stroke Patients: OSA prevalence in acute stroke is 50–75%. Sleep-disordered breathing worsens stroke outcomes (larger infarct volume, worse functional recovery, higher recurrence risk). Screen ALL stroke patients for OSA (STOP-BANG, then HSAT/PSG when stable). CPAP within 1–2 weeks post-stroke improves neurological recovery and reduces recurrent vascular events. The SAVE trial (McEvoy et al. NEJM 2016) showed modest benefit of CPAP for secondary cardiovascular prevention, but adherence was suboptimal (mean 3.3 h/night) — better adherence may yield greater benefit.

Q: A 52-year-old obese man (BMI 38) presents with excessive daytime sleepiness (ESS 16/24), witnessed apneas, morning headaches, and resistant hypertension on 3 antihypertensives. STOP-BANG score is 7. HSAT shows REI 42/h with nadir SpO₂ 74%. He is prescribed auto-CPAP but returns after 2 months reporting he cannot tolerate the mask. What are the next steps?

Assessment: Severe OSA (REI 42/h), significant hypoxemia, resistant HTN (likely OSA-driven), high cardiovascular risk. CPAP intolerance is common (~30–50% struggle with adherence).
Step-by-step approach:
1. Troubleshoot CPAP adherence first:
• Mask interface: try different types (nasal pillows, nasal mask, full-face); professional mask fitting
• Pressure comfort: ensure auto-CPAP range is appropriate; try EPR/pressure relief; ramp settings
• Humidification: heated humidifier for nasal congestion/dryness
• Behavioral: desensitization protocol, CBT for CPAP adherence
• Download CPAP data: check actual usage hours, leak rates, residual AHI
2. If CPAP truly intolerable after optimization:
• Hypoglossal nerve stimulation (Inspire): candidate if AHI 15–65, BMI now <40 (updated criteria), CPAP intolerant, no concentric collapse on DISE
• MAD (mandibular advancement device): reasonable but may not adequately treat severe OSA (AHI 42)
3. Weight loss (critical):
• GLP-1/GIP receptor agonist (tirzepatide or semaglutide): dual benefit — weight loss + direct AHI reduction (SURMOUNT-OSA data)
• Consider bariatric surgery referral given BMI 38 + comorbidities
4. Address resistant hypertension: Treat OSA to improve BP control; add spironolactone (PATHWAY-2); renal denervation if truly resistant
5. Driving safety: Counsel about drowsy driving risk with untreated severe OSA and ESS 16

9.2 Narcolepsy — Comprehensive Review

9.2.1 Pathophysiology & Classification

Narcolepsy is a chronic disorder of central hypersomnolence caused by impaired orexin (hypocretin) signaling. Prevalence: ~25–50/100,000. Two types with fundamentally different biology:

Narcolepsy Type 1 vs. Type 2

Feature	Narcolepsy Type 1 (NT1)	Narcolepsy Type 2 (NT2)
Pathophysiology	Autoimmune destruction of orexin-producing neurons in lateral hypothalamus (>90% loss). T-cell mediated (CD8+ cytotoxic T cells targeting orexin neurons)	Unknown; partial orexin loss? Orexin neurons intact but dysfunctional? ~30% may convert to NT1 over time
CSF orexin	≤110 pg/mL (or <1/3 of mean normal) — diagnostic	Normal (>110 pg/mL) or intermediate
Cataplexy	Present (pathognomonic for NT1)	Absent
HLA association	*HLA-DQB106:02** in >90–98% (but also present in 12–38% of general population; necessary but NOT sufficient)	HLA-DQB1*06:02 in ~40–50%
MSLT	Mean sleep latency ≤8 min + ≥2 SOREMPs	Mean sleep latency ≤8 min + ≥2 SOREMPs (same criteria; diagnosis of exclusion)
Comorbidities	Obesity (~30%), sleep paralysis (~50%), hypnagogic hallucinations (~60%), disrupted nocturnal sleep	Similar but generally less severe

Orexin/Hypocretin System

The orexin system is a master arousal/wake-promoting center:

Component	Details
Orexin neurons	~70,000 neurons in lateral hypothalamus; produce orexin-A (hypocretin-1) and orexin-B (hypocretin-2)
Projections	Widespread: locus coeruleus (NE), dorsal raphe (5-HT), TMN (histamine), VTA (DA), basal forebrain (ACh), LDT/PPT — stabilizes the wake-sleep flip-flop switch
Function	Stabilize wakefulness; prevent inappropriate transitions to REM/NREM; regulate reward/motivation, feeding, autonomic function
Loss in NT1	>90% orexin neuron loss → unstable state boundaries → intrusion of REM phenomena into wakefulness (cataplexy, sleep paralysis, hallucinations, SOREMPs)

Clinical Pearl — Autoimmune Triggers: NT1 onset frequently follows environmental triggers in genetically susceptible (HLA-DQB1*06:02+) individuals. Documented triggers include: H1N1 influenza infection (2009 pandemic → NT1 incidence spike), Pandemrix vaccine (AS03-adjuvanted H1N1 vaccine, especially in Scandinavian children — OR ~6–9), Streptococcal infection (molecular mimicry with orexin), and possibly SARS-CoV-2 (case reports). Typical latency: weeks to months after trigger. This makes NT1 one of the best-characterized autoimmune neurological diseases from an etiological standpoint.

9.2.2 Clinical Features

The Narcolepsy Pentad (NT1)

Symptom	Description	Frequency in NT1
Excessive Daytime Sleepiness (EDS)	Irresistible sleep attacks; brief refreshing naps; worst in monotonous situations. Most disabling symptom	100% (required for diagnosis)
Cataplexy	Sudden bilateral loss of muscle tone triggered by positive emotions (laughter, surprise, excitement). Consciousness preserved. Duration: seconds to minutes. Can be partial (jaw drop, head nod, knee buckling) or complete (collapse)	~70–80% of NT1. Pathognomonic
Sleep paralysis	Inability to move during sleep-wake transitions (seconds to minutes). Frightening but benign	~50%
Hypnagogic/hypnopompic hallucinations	Vivid visual/auditory hallucinations at sleep onset (hypnagogic) or awakening (hypnopompic)	~60%
Disrupted nocturnal sleep (DNS)	Frequent awakenings; fragmented sleep despite EDS. Paradoxical: sleepy during day, cannot maintain sleep at night	~50–70%

Clinical Pearl — Cataplexy Mimics: Not all “drop attacks” are cataplexy. Key differential: (1) Syncope — loss of consciousness (absent in cataplexy); (2) Epileptic atonic seizures — EEG abnormality, not emotion-triggered; (3) Gelastic seizures — laughter-induced (hypothalamic hamartoma); (4) Psychogenic/functional — variable triggers, no consistent pattern. True cataplexy: preserved consciousness, emotion trigger (especially laughter), brief (<2 min), bilateral. Facial cataplexy (jaw drop, tongue protrusion) is highly specific for NT1 in children.

9.2.3 Diagnostic Workup

ICSD-3 Revised Diagnostic Criteria for Narcolepsy

Criterion	NT1	NT2
A (required)	Daily periods of irrepressible need to sleep or daytime lapses into sleep for ≥3 months
B (NT1)	≥1 of: (1) Cataplexy + MSLT positive; (2) CSF orexin-A ≤110 pg/mL	—
B (NT2)	—	MSLT: mean sleep latency ≤8 min + ≥2 SOREMPs. CSF orexin-A >110 pg/mL or not measured. No cataplexy
Exclusions	OSA adequately treated (AHI <5), insufficient sleep excluded (sleep diary/actigraphy ≥7 days, ≥7h sleep opportunity), medication effects excluded (REM-suppressing drugs stopped ≥14 days or 5× half-life)

MSLT Protocol & Interpretation

Aspect	Details
Protocol	5 nap opportunities at 2-hour intervals beginning 1.5–3 hours after waking. Each nap: 20 minutes (or 15 min after sleep onset). Prior night PSG required (≥6h sleep). Stop REM-suppressants ≥14 days prior. Actigraphy/sleep diary ≥7 days showing adequate sleep (≥7h)
Sleep latency	Mean across 5 naps. ≤8 minutes = pathological sleepiness
SOREMP	Sleep Onset REM Period: REM within 15 minutes of sleep onset. ≥2 SOREMPs required. A SOREMP on prior-night PSG (within 15 min of sleep onset) can count as one of the two
Positive MSLT	Mean SL ≤8 min + ≥2 SOREMPs → consistent with narcolepsy. Sensitivity ~90–95% for NT1; ~70–80% for NT2. Specificity issues: false positives in OSA, insufficient sleep, circadian disorders, depression

Clinical Pearl — Common MSLT Pitfalls: (1) Insufficient pre-MSLT sleep (<6h) → false positive SOREMPs. Always review prior-night PSG sleep time. (2) REM-suppressing drugs not adequately washed out (SSRIs, SNRIs, TCAs) → rebound SOREMPs after cessation = false positive; suppressed SOREMPs if still on drug = false negative. (3) Untreated OSA can cause short sleep latency on MSLT → treat OSA first, then repeat MSLT. (4) Circadian misalignment (shift workers, delayed sleep phase) can produce SOREMPs during habitual sleep time.

9.2.4 Pharmacotherapy

Narcolepsy Pharmacotherapy — Complete Guide

Drug	Target	Mechanism	Dose	Key Notes
Sodium oxybate (Xyrem)	EDS + cataplexy + DNS	GABA_B agonist; consolidates deep sleep (SWS); mechanism for cataplexy control unclear	2.25 g at bedtime + repeat 2.5–4h later (split dosing); titrate to 4.5 g ×2/night (max 9 g/night)	Gold standard for NT1 (addresses all symptoms). REMS program. Avoid alcohol. Monitor respiratory depression. Sodium load concern (hypertension, HF) → low-sodium formulation (calcium/magnesium/potassium oxybate = Xywav). Takes 2–3 months for full cataplexy effect
Low-sodium oxybate (Xywav)	EDS + cataplexy + DNS	Same as Xyrem but 92% less sodium	Same dosing as Xyrem	FDA 2020; preferred in patients with cardiovascular risk; also approved for NT2 and idiopathic hypersomnia (IH)
Once-nightly oxybate (FT218/Lumryz)	EDS + cataplexy	Extended-release sodium oxybate; single nightly dose	4.5 g single dose at bedtime; titrate to 6–9 g	FDA 2023. Eliminates need for mid-sleep second dose. Improved adherence. REMS program
Modafinil	EDS (first-line wake-promoter)	Weak DAT inhibitor; promotes wakefulness via DA/NE/histamine pathways	100–200 mg morning; may add 100–200 mg noon (max 400 mg/day)	Non-scheduled in some countries. Induces CYP3A4 → reduces oral contraceptive efficacy. SJS/TEN risk (rare). No effect on cataplexy
Armodafinil	EDS	R-enantiomer of modafinil; longer half-life	150–250 mg morning	More sustained wakefulness; same CYP3A4 induction
Pitolisant (Wakix)	EDS + cataplexy	H₃ receptor inverse agonist → ↑histamine release from TMN; also ↑NE, DA, ACh	4.45 mg → 8.9 mg → 17.8 mg → max 35.6 mg morning	FDA 2019 (EDS); 2020 (cataplexy). Non-scheduled. Novel mechanism. QTc prolongation risk — avoid with QT-prolonging drugs. First-in-class. May be combined with modafinil
Solriamfetol (Sunosi)	EDS	Dual DNRI (dopamine/norepinephrine reuptake inhibitor)	75 mg → 150 mg morning (max 150 mg)	FDA 2019. Rapid onset. Scheduled (IV). BP/HR monitoring. Also approved for EDS in OSA (on CPAP with residual sleepiness)
Methylphenidate / Amphetamines	EDS	DAT/NET inhibitor (methylphenidate); DA/NE releaser (amphetamine)	Methylphenidate: 10–60 mg/day; Dextroamphetamine: 5–60 mg/day	Traditional stimulants. Effective but higher abuse potential (Schedule II). Reserve for refractory cases or where modafinil unavailable (used in Thailand)
Venlafaxine	Cataplexy (off-label)	SNRI → REM suppression via NE/5-HT	75–225 mg/day	Widely used for cataplexy. NEVER stop abruptly → rebound cataplexy crisis (status cataplecticus). Taper over 2+ weeks
Clomipramine / TCAs	Cataplexy	Potent REM suppression (NE/5-HT reuptake)	Clomipramine 10–75 mg/day	Most potent anti-cataplectic; limited by anticholinergic side effects. Abrupt withdrawal → rebound cataplexy

Treatment Algorithm

Practical Treatment Approach

NT1 with cataplexy:

Sodium oxybate / low-sodium oxybate (addresses EDS + cataplexy + disrupted nocturnal sleep) — if available and tolerated, best single agent
Add modafinil/armodafinil in the morning if residual EDS on oxybate
Alternative for cataplexy: pitolisant (addresses both EDS + cataplexy) or venlafaxine/clomipramine (cataplexy only)
Refractory EDS: solriamfetol, methylphenidate, or amphetamine add-on

NT2 / EDS without cataplexy:

Modafinil/armodafinil first-line
Pitolisant or solriamfetol if inadequate
Low-sodium oxybate (Xywav) — FDA approved for NT2 and IH

Thai context: Modafinil is available in Thailand (imported, special authorization). Sodium oxybate, pitolisant, solriamfetol are NOT available in Thailand. Methylphenidate is available (narcotic license required). Venlafaxine is widely available for cataplexy treatment.

Clinical Pearl — Narcolepsy in Children: Childhood-onset NT1 often presents differently: (1) cataplexy may manifest as “cataplectic facies” (perioral muscle hypotonia, tongue protrusion, eyelid drooping) rather than classic collapse; (2) rapid weight gain at disease onset (orexin regulates appetite/metabolism); (3) precocious puberty reported; (4) behavioral/attention problems may lead to ADHD misdiagnosis. CSF orexin measurement is particularly valuable in children where MSLT may be unreliable.

Q: A 28-year-old woman presents with 6 months of irresistible daytime sleepiness with daily “sleep attacks” and episodes of jaw drop and knee buckling triggered by laughter. She has vivid hallucinations when falling asleep. MSLT shows mean sleep latency 4.2 minutes with 4 SOREMPs. HLA-DQB1*06:02 is positive. What is the diagnosis and optimal treatment plan?

Diagnosis: Narcolepsy Type 1 (NT1)
• EDS ≥3 months — criterion A met
• Cataplexy present (jaw drop + knee buckling triggered by laughter = partial cataplexy) + MSLT positive (SL 4.2 min ≤8 + 4 SOREMPs ≥2) — criterion B met
• HLA-DQB1*06:02 positive supports diagnosis (98% of NT1) but is not required for diagnosis
• CSF orexin measurement would confirm (≤110 pg/mL expected) but not required when cataplexy + MSLT positive
Optimal treatment:
1. Sodium oxybate (Xyrem) or low-sodium oxybate (Xywav) — gold standard addressing EDS + cataplexy + disrupted nocturnal sleep. Start 2.25 g × 2 nightly, titrate over 4–8 weeks. Expect cataplexy control in 2–3 months
2. Add modafinil 200 mg morning for residual daytime sleepiness (often needed in combination)
3. If oxybate unavailable (e.g., Thailand):
• Modafinil 200–400 mg/day for EDS
• Venlafaxine 75–150 mg/day for cataplexy (warn: never stop abruptly → status cataplecticus)
4. Non-pharmacological: Scheduled naps (15–20 min, 1–2×/day); sleep hygiene; driving safety counseling; work/school accommodations
5. Contraception counseling: Modafinil reduces OCP efficacy (CYP3A4 induction) → use barrier methods or IUD

9.3 REM Sleep Behavior Disorder — The Prodromal Synucleinopathy

9.3.1 Pathophysiology & Definition

RBD is characterized by loss of normal REM atonia with resultant dream-enactment behavior. During normal REM sleep, subcortical circuits (sublaterodorsal nucleus/subcoeruleus → spinal motor neurons via ventromedial medulla) produce active muscle atonia. In RBD, α-synuclein deposition disrupts these brainstem circuits, allowing motor activity during REM.

ICSD-3 Diagnostic Criteria for RBD

Criterion	Details
A	Repeated episodes of vocalization and/or complex motor behaviors during sleep
B	Behaviors documented by PSG to occur during REM sleep OR presumed to be REM-related based on clinical history of dream enactment
C	PSG demonstrates REM sleep without atonia (RSWA) on chin or limb EMG
D	Not better explained by another sleep disorder, mental disorder, medication, or substance

Key PSG finding: RSWA — sustained (tonic) or intermittent (phasic) elevation of chin EMG or excessive phasic activity in limb EMG during REM sleep. Quantitative thresholds: tonic chin EMG >30% of REM epochs AND/OR phasic activity >15% of 3-second mini-epochs.

9.3.2 Isolated RBD (iRBD): The Strongest Prodromal Biomarker of Synucleinopathy

iRBD Phenoconversion Data

Study	Cohort	Conversion Rate	Key Findings
Postuma et al. Brain 2019 (NAPS cohort)	1,280 iRBD patients; multicenter	6.3%/year; 73.5% at 12 years	Conversion to: PD (43%), DLB (25%), MSA (5%), unspecified parkinsonism/dementia (remainder). Median time to conversion ~8 years
Iranzo et al. Lancet Neurol 2014	174 iRBD; 7.7-year follow-up	90.9% at 14 years	Longest follow-up; virtually all convert eventually

Phenoconversion predictors:

Abnormal DaT-SPECT (reduced striatal uptake) — predicts conversion to PD/DLB within 3–5 years
αSyn-SAA positive (CSF or skin biopsy) — ~90% of iRBD patients; confirms underlying synucleinopathy
Olfactory dysfunction (UPSIT score <22) — strong predictor
Cognitive impairment (MoCA decline, especially visuospatial/attention) — predicts conversion to DLB rather than PD
Color vision impairment, constipation, orthostatic hypotension, depression

Clinical Pearl — iRBD in Clinical Practice: Every patient diagnosed with iRBD should be counseled about the high lifetime risk of developing PD, DLB, or MSA. However, delivery requires sensitivity — no neuroprotective therapy is yet available outside clinical trials. Recommended approach: (1) Annual neurological examination (motor, cognitive, autonomic screening), (2) Baseline and serial DaT-SPECT/αSyn-SAA if available, (3) Discuss enrollment in neuroprotective clinical trials (PASADENA (prasinezumab), PADOVA targeting prodromal PD), (4) Manage RBD symptoms for safety and bed-partner quality of life.

Drug-Induced RBD

Drug Class	Mechanism	Management
SSRIs / SNRIs (fluoxetine, venlafaxine, most common culprits)	Serotonergic enhancement of REM atonia loss; increase phasic EMG activity in REM	If possible, switch to bupropion or mirtazapine (less RBD risk). If must continue: treat symptomatically with melatonin
TCAs	Similar to SSRIs; NE/5-HT reuptake	Dose reduction or switch
Beta-blockers (bisoprolol, atenolol)	Melatonin suppression; REM disruption	Switch to non-lipophilic agent or add melatonin

Important distinction: Drug-induced RBD may unmask subclinical synucleinopathy rather than being purely pharmacogenic. SSRI-associated RBD patients have higher rates of DaT-SPECT abnormalities and eventual phenoconversion than the general population — monitor these patients longitudinally.

9.3.3 RBD Treatment

Treatment	Evidence	Notes
Melatonin 3–12 mg at bedtime	First-line; restores REM atonia by unclear mechanism (possibly restores circadian REM regulation). Sn of response ~50–70%	Safest option; no fall risk, cognitive impairment, or tolerance. Start 3 mg, titrate up to 12 mg. Sustained-release may be better. Take 30–60 min before bed
Clonazepam 0.25–2 mg at bedtime	Effective in ~80–90% (reduces motor behaviors); does NOT restore REM atonia but suppresses phasic activity	Risks in elderly: falls, sedation, cognitive impairment, respiratory depression (avoid in OSA). Reserve for melatonin failures or severe/injurious RBD
Bed safety measures	Essential for ALL patients	Pad floor around bed; remove sharp/breakable objects from bedside; sleep in sleeping bag (restricts movement); separate beds if bed partner at risk; low bed or mattress on floor

9.4 NREM Parasomnias & Other Sleep Disorders

9.4.1 NREM Parasomnias (Disorders of Arousal)

NREM parasomnias arise from incomplete arousal from deep sleep (N3/SWS), typically in the first third of the night. They share common pathophysiology: a dissociated brain state with simultaneous wake-like motor behavior and sleep-like consciousness.

Parasomnia	Age	Features	Duration	Distinguishing Points
Confusional Arousals	Children > adults	Confused, disoriented behavior upon arousal; may sit in bed, mumble, appear awake but not responsive	Minutes	No ambulation; no autonomic activation
Sleepwalking (Somnambulism)	Peak 8–12y; persists in ~4% adults	Walking/complex behavior during sleep; eyes open, blank stare; amnesia for event; can eat, cook, drive	Minutes to >30 min	Ambulation present; injury risk (falls, leaving house). No dream recall (unlike RBD)
Sleep Terrors	Peak 5–7y	Sudden arousal with intense fear, screaming, autonomic activation (tachycardia, sweating, mydriasis); inconsolable	1–5 min	Intense autonomic activation; amnesia; more dramatic than confusional arousals
Sleep-Related Eating Disorder (SRED)	Adults > children	Recurrent episodes of involuntary eating during partial arousals; unusual food choices; amnestic	Variable	Associated with sleepwalking, zolpidem use; weight gain; injury (cooking while asleep)

NREM Parasomnia vs. RBD vs. Nocturnal Seizures: Critical Differential

Feature	NREM Parasomnia	RBD	Nocturnal Frontal Lobe Epilepsy (NFLE/SHE)
Timing in night	First third (N3 predominant)	Last third (REM predominant)	Any time; often within 30 min of sleep onset; multiple per night
Age	Children/young adults	>50 years	Any; onset in childhood/adolescence
Eyes	Open, glassy	Closed (dreaming)	Open or closed
Dream recall	None or vague	Vivid dream recall correlating with behavior	Usually none
Stereotyped	No (variable behaviors)	No (dream-dependent)	Yes (stereotyped movements)
Episodes/night	Usually 1	Multiple (in REM periods)	Multiple, clustered
Duration	Minutes	Seconds to minutes	Seconds to <2 min (brief)
PSG	Arousal from N3	REM without atonia	Epileptiform discharges (may be subtle/absent on scalp EEG)
Treatment	Reassurance; clonazepam; safety	Melatonin; clonazepam	Carbamazepine / lacosamide

9.4.2 NREM Parasomnia Treatment

Approach	Details
Non-pharmacological (first-line)	Safety measures (locks on doors/windows, alarms, remove hazards); adequate sleep duration (sleep deprivation is a major trigger); regular sleep schedule; avoid alcohol and sedative-hypnotics at bedtime; treat comorbid OSA (apnea-induced arousals trigger parasomnias)
Scheduled awakenings	For children: wake child 15–30 min before typical parasomnia time for 4 weeks. Effective in ~80%
Pharmacotherapy (refractory/dangerous)	Clonazepam 0.25–0.5 mg at bedtime (suppresses N3 arousals). Consider low-dose SSRI (controversial). Melatonin may help

Clinical Pearl — OSA as Parasomnia Trigger: Untreated OSA is one of the most common triggers for NREM parasomnias in adults. Apneic events cause forced arousals from SWS, precipitating sleepwalking/sleep terrors. Always screen for and treat OSA in any adult presenting with new-onset parasomnias. CPAP treatment alone may completely resolve the parasomnia without need for additional pharmacotherapy.

Q: Parents bring a 6-year-old boy who has had episodes of screaming, sitting up in bed with intense fear expression, tachycardia, and sweating approximately 1–2 hours after falling asleep. Episodes last 2–3 minutes, he is inconsolable during the event, and has no memory of it the next morning. He has had 3 episodes in the past month, all in the first half of the night. What is the diagnosis, and a 62-year-old man reports similar nocturnal episodes but occurring in the early morning hours with vivid recall of being chased. How does the differential differ?

6-year-old boy: Sleep terrors (NREM parasomnia)
• Typical features: first third of night (SWS-predominant), intense autonomic activation, inconsolable, complete amnesia, peak age 5–7 years
• Management: Reassurance (benign, self-limiting in most children); safety measures; ensure adequate sleep duration; scheduled awakenings if frequent. No PSG needed if classic presentation

62-year-old man: Very different differential — most likely RBD
• Early morning (last third) = REM-predominant timing
• Vivid dream recall (being chased) = dream enactment behavior (hallmark of RBD, absent in NREM parasomnias)
• Age >50 = high risk for synucleinopathy-associated RBD
• Must also consider: nocturnal seizures (SHE) — but stereotypy and brevity would be expected; nightmare disorder — but no motor enactment on PSG
• Required workup: PSG with video and expanded EMG montage to confirm RSWA; if RBD confirmed: screen for early synucleinopathy (olfaction, DaT-SPECT, αSyn-SAA, motor exam, MoCA); melatonin 6–12 mg for treatment; annual neurological follow-up for phenoconversion

9.5 Chronic Insomnia — CBT-I & Pharmacotherapy

9.5.1 Definition & Epidemiology

Chronic insomnia disorder (ICSD-3): difficulty initiating or maintaining sleep, or early morning awakening, with associated daytime impairment, occurring ≥3 nights/week for ≥3 months, despite adequate opportunity to sleep. Prevalence: ~10–15% of adults for chronic insomnia; up to 30–50% report insomnia symptoms. Women > men (~1.5×). Prevalence increases with age.

Spielman 3-P Model of Insomnia

Factor	Description	Examples
Predisposing	Baseline vulnerability (trait)	Genetic predisposition, hyperarousal phenotype, anxiety-prone personality, female sex, older age
Precipitating	Acute trigger (usually identifiable)	Stressful life event, illness, pain, medication change, grief, job loss, travel
Perpetuating	Maladaptive behaviors that maintain insomnia after precipitant resolves	Excessive TIB (spending too long in bed), napping, sleep effort/anxiety, caffeine, irregular schedule, bedtime phone use

Key insight: CBT-I targets the perpetuating factors — which is why it produces durable improvement even after the original precipitant resolves.

9.5.2 Cognitive Behavioral Therapy for Insomnia (CBT-I)

CBT-I: First-Line Treatment for Chronic Insomnia (ALL Guidelines)

Every major guideline (ACP 2016, AASM 2021, NICE 2021, European Sleep Research Society 2023) recommends CBT-I as first-line treatment for chronic insomnia, superior to pharmacotherapy for long-term outcomes.

CBT-I Component	Technique	Mechanism
Sleep Restriction Therapy (SRT)	Limit time in bed (TIB) to match actual sleep time (e.g., if sleeping 5h, TIB = 5.5h). Gradually increase by 15–30 min/week as sleep efficiency (SE) improves. Goal: SE ≥85%	Most powerful component. Builds homeostatic sleep drive; consolidates sleep. Temporarily increases sleepiness (warn patients)
Stimulus Control	(1) Bed for sleep and sex only; (2) Go to bed only when sleepy; (3) If awake >20 min, get up and return when sleepy; (4) Fixed wake time regardless of sleep; (5) No napping	Re-associates bed with sleep; breaks conditioned arousal. Addresses conditioned hyperarousal in bed
Cognitive Restructuring	Challenge dysfunctional beliefs: “I must get 8 hours,” “I won’t function tomorrow,” catastrophizing about insomnia consequences	Reduces sleep-related anxiety and performance effort
Sleep Hygiene	Regular schedule, avoid caffeine after noon, limit alcohol, cool/dark/quiet bedroom, avoid screens 1h before bed, exercise (but not late evening)	Supportive; insufficient alone as monotherapy. Must be combined with SRT and stimulus control
Relaxation Training	Progressive muscle relaxation, diaphragmatic breathing, mindfulness meditation, body scan	Reduces somatic and cognitive hyperarousal

Delivery formats: Individual therapist (gold standard, 4–8 sessions); group CBT-I (effective, cost-efficient); digital CBT-I (dCBT-I) — validated apps (Sleepstation, Pear Somryst [FDA-cleared], Sleepio): effect sizes similar to in-person. Accessible in settings with limited sleep psychologist availability (relevant for Thailand).

Clinical Pearl — CBT-I vs. Medications: The ACP 2016 Clinical Guideline (Qaseem et al. Ann Intern Med) concluded: CBT-I should be first-line for ALL adult patients with chronic insomnia. Medications should be considered only when CBT-I alone is insufficient. Key advantage: CBT-I effects are maintained for ≥2 years post-treatment, whereas medication benefits cease upon discontinuation and carry risks of dependence, tolerance, falls, and cognitive impairment in elderly.

9.5.3 Insomnia Pharmacotherapy

Insomnia Pharmacotherapy — Evidence-Based Guide

Drug Class	Drug	Dose	Target	Key Features
Orexin Receptor Antagonists (DORAs)	Suvorexant (Belsomra)	10–20 mg	Sleep onset + maintenance	Blocks orexin OX1R/OX2R → permits sleep. Preferred for chronic insomnia in elderly (no respiratory depression, no dependence, no falls). Avoid in narcolepsy. Morning grogginess at higher doses
Orexin Receptor Antagonists (DORAs)	Lemborexant (Dayvigo)	5–10 mg	Sleep onset + maintenance	More balanced OX1R/OX2R antagonism. SUNRISE-2 trial: effective for 12 months, well-tolerated in elderly
Z-drugs (BzRA)	Zolpidem	IR: 5–10 mg (5 mg women); ER: 6.25–12.5 mg; SL: 1.75–3.5 mg	Sleep onset (IR); maintenance (ER)	GABA_A α1 selective. Short-term only (≤4 weeks). Risks: complex sleep behaviors (sleep-driving, sleep-eating — FDA black box 2019), tolerance, dependence, falls, next-morning impairment (especially ER). Women metabolize slower → lower dose
Z-drugs (BzRA)	Eszopiclone (Lunesta)	1–3 mg (1 mg in elderly)	Sleep onset + maintenance	Longest-studied BzRA; efficacy maintained at 6 months in clinical trials. Metallic taste. Less risk of complex sleep behaviors than zolpidem
Melatonin Receptor Agonist	Ramelteon (Rozerem)	8 mg	Sleep onset (circadian)	MT1/MT2 agonist. No abuse potential (non-scheduled). Modest efficacy. Best for circadian-related insomnia. Safe in elderly. Avoid with fluvoxamine (CYP1A2)
Low-dose Antidepressant	Doxepin (Silenor)	3–6 mg	Sleep maintenance	At ultra-low dose: selective H₁ antagonist (no anticholinergic effects at this dose). FDA-approved for sleep maintenance insomnia. Excellent for elderly patients with early morning awakening. No tolerance in trials up to 3 months
Off-label	Trazodone	25–100 mg	Sleep onset + maintenance	5-HT2A antagonist + weak H₁. Most prescribed off-label insomnia drug worldwide. Limited RCT evidence for insomnia specifically. Risks: orthostatic hypotension, priapism (rare). Commonly used in dementia patients for insomnia
Antihistamine	Diphenhydramine / Doxylamine	25–50 mg	Sleep onset	OTC. NOT recommended for chronic insomnia: rapid tolerance (3–5 days), anticholinergic burden in elderly (Beers list), cognitive impairment, urinary retention

Clinical Pearl — Benzodiazepines for Insomnia: Long-acting benzodiazepines (diazepam, clonazepam, flurazepam) should be AVOIDED for chronic insomnia: prolonged sedation, accumulation in elderly, falls, cognitive impairment, tolerance, dependence. Even short-acting BZDs (temazepam, triazolam) should be reserved for short-term use only. The Beers Criteria (AGS 2023) lists all benzodiazepines and Z-drugs as potentially inappropriate in adults ≥65 years for insomnia treatment.

9.5.4 Circadian Rhythm Sleep-Wake Disorders (CRSWDs)

Circadian Rhythm Disorders

Disorder	Features	Treatment
Delayed Sleep-Wake Phase Disorder (DSWPD)	Sleep onset typically 2–6 AM, wake noon–2 PM. Common in adolescents/young adults (~7–16%). Normal sleep quality/duration when on preferred schedule (weekends). Genetic: PER3, CRY1 variants	Morning bright light therapy (10,000 lux, 30 min upon waking) + low-dose melatonin (0.5–3 mg) 4–6 hours before desired bedtime + chronotherapy (progressive advancement or delay). Strategic light avoidance in evening (blue-light filters)
Advanced Sleep-Wake Phase Disorder (ASWPD)	Sleep onset 6–9 PM, wake 2–5 AM. Common in elderly. Familial: CK1δ, PER2 mutations (FASPS)	Evening bright light therapy (2–3 hours before habitual sleep onset). Avoid morning bright light. Chronotherapy less effective than in DSWPD
Shift Work Disorder	Insomnia and/or EDS temporally associated with recurring work schedule that overlaps habitual sleep period. Affects ~10–40% of shift workers	Strategic napping before/during shift; bright light during shift; melatonin before daytime sleep; modafinil/armodafinil for shift-time sleepiness (FDA-approved). Minimize consecutive night shifts. Fixed schedule better than rotating
Jet Lag Disorder	Insomnia/EDS after ≥2 time zone crossing. Eastward travel worse (requires phase advance). ~1 day recovery per time zone crossed	Pre-trip light/melatonin timing. Melatonin 0.5–5 mg at destination bedtime. Light exposure per direction: eastward = morning light, avoid evening; westward = evening light, avoid morning
Non-24-Hour Sleep-Wake Disorder (Non-24)	Free-running circadian rhythm (>24h period). Most common in totally blind individuals (50–75%) due to absent photic entrainment. Rare in sighted	Tasimelteon (Hetlioz): MT1/MT2 agonist; FDA-approved for Non-24 in blind. Melatonin 0.5–3 mg at fixed time
Irregular Sleep-Wake Rhythm Disorder	Fragmented sleep with no clear circadian pattern; multiple naps throughout 24h. Associated with dementia (AD, DLB), brain injury, developmental disorders	Structured light exposure, melatonin, activity scheduling, treat underlying cause. Frequently encountered in your dementia patients (Section 8)

Clinical Pearl — Melatonin Timing: The timing of melatonin is more important than the dose. For DSWPD: give melatonin 4–6 hours before desired sleep onset (not at bedtime — too late for phase-advancing effect). Example: if desired sleep = midnight, give melatonin at 6–8 PM. For jet lag (eastward): melatonin at destination bedtime starting 1–2 days before travel. Low doses (0.5–1 mg) are as effective as high doses for circadian phase shifting, with fewer side effects.

9.6 Restless Legs Syndrome (RLS) & Periodic Limb Movement Disorder (PLMD)

9.6.1 Restless Legs Syndrome / Willis-Ekbom Disease

RLS is a sensorimotor disorder characterized by an irresistible urge to move the legs, usually accompanied by uncomfortable sensations, worsening at rest and in the evening/night, and relieved by movement. Prevalence: ~5–15% in Western populations; ~1–3% in Asia (including Thailand).

IRLSSG Diagnostic Criteria (2014 Revised)

ALL 5 criteria required:

#	Criterion	Key Points
1	Urge to move the legs, usually accompanied by uncomfortable/unpleasant sensations	Described as: creeping, crawling, pulling, itching, tingling, aching, “electricity,” “worms crawling.” May affect arms
2	Urge begins or worsens during rest or inactivity	Sitting, lying down. Worse in sedentary situations (meetings, flights, cinema)
3	Urge is partially or totally relieved by movement	Walking, stretching, rubbing. Relief persists as long as movement continues
4	Urge occurs exclusively or predominantly in the evening or night	Circadian variation (dopaminergic nadir in evening). Critical for distinguishing from positional discomfort, neuropathy
5	Not solely accounted for by another medical/behavioral condition	Must exclude: leg cramps, positional discomfort, peripheral neuropathy, venous stasis, habitual foot tapping, akathisia (neuroleptic-induced)

Supportive features: Family history (>50% in primary RLS); positive response to dopaminergic agents; PLMS on PSG (>80% of RLS patients).

Pathophysiology

Mechanism	Evidence
Brain iron deficiency	MRI shows ↓iron in substantia nigra even with normal serum ferritin; CSF ferritin ↓. Iron is cofactor for tyrosine hydroxylase (rate-limiting step in DA synthesis). Serum ferritin <75 μg/L = iron repletion indicated regardless of Hb
Dopaminergic dysfunction	A3 hypothalamic dopaminergic neurons (diencephalospinal pathway); circadian dopamine variation correlates with symptom timing; DA agonists relieve symptoms but long-term use causes augmentation
Genetics	BTBD9, MEIS1, MAP2K5 (GWAS loci); heritability ~60% in primary RLS. MEIS1 linked to iron regulation
Glutamate hyperexcitability	Thalamic glutamate ↑ in RLS (MRS studies); may explain why α2δ ligands (gabapentin, pregabalin) are effective

Secondary Causes of RLS

Cause	Mechanism	Management
Iron deficiency	Most important secondary cause; ↓brain iron → ↓DA synthesis	Oral iron (ferrous sulfate 325 mg + vitamin C on empty stomach) if ferritin <75. IV ferric carboxymaltose 500–1000 mg if oral fails or ferritin <30
End-stage renal disease	Present in ~25–50% of dialysis patients; iron deficiency + uremic toxins	Iron repletion; DA agonists; gabapentin (adjust dose); kidney transplantation may cure
Pregnancy	~25% prevalence; iron/folate depletion; hormonal	Iron supplementation; resolves post-partum in most
Peripheral neuropathy	Sensory nerve dysfunction mimics/triggers RLS	Treat underlying neuropathy; α2δ ligands dual benefit
Medications that worsen RLS	Dopamine antagonists, antihistamines, SSRIs/SNRIs, lithium	Substitute: bupropion (least likely antidepressant to worsen RLS); avoid metoclopramide (use domperidone)

9.6.2 RLS Treatment Algorithm

RLS Pharmacotherapy (IRLSSG/AASM 2024 Updated)

Line	Drug	Dose	Key Notes
Step 0	Iron repletion	Target ferritin >75 μg/L (some experts target >100)	ALWAYS check and correct iron first, regardless of other therapy. May be sufficient monotherapy in mild-moderate RLS with low ferritin
First-line	Gabapentin	300–900 mg, 2h before bedtime	Preferred first-line (IRLSSG 2024): no augmentation risk, helps sleep, helps pain/neuropathy. Dose adjust in renal impairment. Dizziness, sedation
First-line	Pregabalin	75–300 mg, 2h before bedtime	Similar efficacy to gabapentin; more predictable absorption. Allen et al. NEJM 2014: pregabalin superior to pramipexole at 52 weeks (no augmentation). Schedule V in US
Second-line	Pramipexole	0.125–0.5 mg, 2h before bedtime	DA agonist; highly effective short-term. AUGMENTATION is the major limitation (see below). Use lowest effective dose for shortest time
Second-line	Rotigotine (patch)	1–3 mg/24h patch	Transdermal DA agonist; less augmentation than oral DA agonists (~8% vs 30–70% at 10y). Skin irritation. Preferred DA agonist if one must be used
Third-line / Refractory	Low-dose opioids	Oxycodone/naloxone PR 5/2.5–40/20 mg; tramadol 50–100 mg; methadone 5–15 mg	For severe refractory RLS; RELOXYN trial (Trenkwalder et al. Lancet Neurol 2013): oxycodone/naloxone effective. Requires careful monitoring (opioid risks). Methadone for the most refractory cases (specialist only)

Augmentation: The Critical Complication

Augmentation of RLS by Dopaminergic Agents

Definition (Max Planck Institute criteria): Paradoxical worsening of RLS symptoms during long-term dopaminergic therapy:

Symptoms start earlier in the day (≥4h earlier than pre-treatment)
Symptoms spread to previously unaffected body parts (arms, trunk)
Symptom intensity increases despite stable or increased dose
Shorter latency to symptom onset at rest
Paradoxical brief relief with dose increase (then worsens — chasing)

Prevalence: 30–70% of patients on pramipexole at 10 years; 8% on rotigotine patch; 0% on α2δ ligands.

Management of augmentation:

Check and correct iron (ferritin >75 μg/L)
Gradually taper and discontinue dopamine agonist (do NOT stop abruptly — DA agonist withdrawal syndrome: anxiety, panic, nausea, pain, depression, suicidality)
Switch to α2δ ligand (gabapentin/pregabalin) as new maintenance
Bridge with low-dose opioid during transition if severe (tramadol 50 mg or oxycodone 5 mg at bedtime for 2–4 weeks)
If refractory after switch: combination therapy (α2δ + low-dose DA agonist at minimum dose) or long-term opioid

9.6.3 Periodic Limb Movement Disorder (PLMD)

PLMS (Periodic Limb Movements of Sleep): repetitive, stereotyped limb movements (typically triple flexion of leg: dorsiflexion of ankle + flexion of knee + flexion of hip) occurring in NREM sleep, every 20–40 seconds. PLMS index >15/h on PSG is abnormal.

PLMD is diagnosed only when PLMS causes clinically significant sleep disturbance or daytime symptoms AND no other cause (RLS, narcolepsy, RBD, OSA, medication effect). Isolated PLMS without symptoms is a PSG finding, NOT a disorder requiring treatment.

Treatment (if PLMD confirmed): Same as RLS (α2δ ligands preferred; DA agonists with augmentation risk).

9.7 Sleep Disorders in Neurological Disease

9.7.1 Sleep and Neurodegeneration

Bidirectional relationship: sleep disorders are both consequences and accelerators of neurodegeneration.

Neurological Disease	Sleep Disorder(s)	Clinical Significance
Parkinson’s Disease	RBD (40–50%), insomnia (60%), EDS (50%), OSA, RLS (15–20%), nocturia	RBD may precede PD by 10+ years; EDS from disease + medications (DA agonists); dopaminergic drugs cause sleep attacks
Alzheimer’s Disease	Sleep fragmentation, circadian disruption (sundowning), OSA (50–75%), irregular sleep-wake rhythm disorder	OSA ↑amyloid deposition via impaired glymphatic clearance; sleep disruption worsens cognitive decline; melatonin may help circadian disruption but minimal cognitive benefit
Stroke	OSA (50–75%), central sleep apnea (5–10%), insomnia (30–60%), circadian disruption, post-stroke hypersomnia	OSA worsens stroke outcomes and recurrence; screen ALL stroke patients; CPAP improves recovery. Post-stroke insomnia associated with worse functional outcome and depression
Epilepsy	Insomnia, OSA, NREM parasomnias (differential for nocturnal seizures), medication effects	Sleep deprivation is a potent seizure trigger; OSA lowers seizure threshold; some ASMs worsen sleepiness (phenobarbital, carbamazepine, valproate); some improve sleep (gabapentin, pregabalin)
Multiple Sclerosis	Insomnia (40%), OSA, RLS (20%), fatigue (MS fatigue ≠ sleepiness), central hypersomnia (hypothalamic plaques)	Fatigue is #1 complaint in MS; distinguish from sleepiness (ESS) and depression. Sleep-disordered breathing undertreated. Modafinil for MS-related fatigue (off-label)
Neuromuscular Disease (ALS, DMD, myasthenia gravis)	Sleep-related hypoventilation, OSA/central apnea, insomnia	FVC <50% predicted or supine ↓>20% → nocturnal NIV (BiPAP). In ALS: BiPAP prolongs survival by ~7–13 months. Monitor respiratory function regularly
Traumatic Brain Injury (TBI)	Insomnia (30–70%), hypersomnia, circadian disruption, sleep apnea, narcolepsy (rare; hypothalamic injury)	Post-TBI sleep disorders are common and underdiagnosed; contribute to poor rehabilitation outcomes. Screen and treat actively

9.7.2 Sleep-Related Epilepsy (SHE / NFLE)

Sleep-Related Hypermotor Epilepsy (SHE), formerly Nocturnal Frontal Lobe Epilepsy (NFLE), is the most important epilepsy differential for parasomnias:

Feature	Details
Semiology	Sudden, brief (<2 min) hypermotor events: bicycling, rocking, thrashing, vocalizations. Highly stereotyped (same pattern every episode). Often multiple per night, clustered
EEG	Interictal: often normal or frontal sharp waves. Ictal: may be obscured by movement artifact; deep frontal foci missed by scalp EEG. Normal EEG does NOT exclude SHE. Video-EEG with extended montage, or stereo-EEG in surgical cases
Genetics	Autosomal dominant SHE (ADSHE): CHRNA4, CHRNB2, CHRNA2 (nicotinic ACh receptor subunits); DEPDC5, NPRL2/3 (mTOR pathway)
Treatment	Carbamazepine low-dose (200–400 mg) — first-line, excellent response (~70%). Alternatives: oxcarbazepine, lacosamide, perampanel

Clinical Pearl — When to Suspect SHE over Parasomnia: Key red flags for SHE: (1) Events are stereotyped (identical every time — NREM parasomnias are variable); (2) Multiple events per night (>3 episodes in one night is unusual for parasomnias); (3) Brief (<2 min each); (4) Onset at any age (parasomnias usually childhood); (5) Family history of epilepsy; (6) No improvement with parasomnia treatment. When in doubt: prolonged video-EEG monitoring with EMG and expanded frontal electrodes. A trial of low-dose carbamazepine can be both diagnostic and therapeutic.

9.8 References & Key Guidelines

Key References & Guidelines

Diagnostic Criteria & Guidelines

American Academy of Sleep Medicine. International Classification of Sleep Disorders, 3rd edition (ICSD-3). 2014; Text Revision 2023.
Qaseem A et al. Management of chronic insomnia disorder in adults: a clinical practice guideline from the American College of Physicians. Ann Intern Med 2016;165(2):125–133. [ACP Insomnia Guideline — CBT-I as first-line]
Sateia MJ et al. Clinical practice guideline for the pharmacologic treatment of chronic insomnia in adults: AASM clinical practice guideline. J Clin Sleep Med 2017;13(2):307–349.
Allen RP et al. Restless legs syndrome/Willis-Ekbom disease diagnostic criteria: updated IRLSSG consensus criteria. Sleep Med 2014;15(8):860–873.
Berry RB et al. AASM Scoring Manual for the Scoring of Sleep and Associated Events. Version 3.0, 2023 (updated 2024).

Landmark Trials & Key Studies

Strollo PJ et al. Upper-airway stimulation for obstructive sleep apnea. N Engl J Med 2014;370:139–149. [STAR Trial — Inspire device]
McEvoy RD et al. CPAP for prevention of cardiovascular events in obstructive sleep apnea. N Engl J Med 2016;375:919–931. [SAVE Trial]
Malhotra A et al. Tirzepatide for the treatment of obstructive sleep apnea and obesity. N Engl J Med 2024;391:1193–1205. [SURMOUNT-OSA]
Allen RP et al. Comparison of pregabalin with pramipexole for restless legs syndrome. N Engl J Med 2014;370:621–631. [Pregabalin superiority at 52 weeks]
Trenkwalder C et al. Prolonged release oxycodone-naloxone for treatment of severe restless legs syndrome. Lancet Neurol 2013;12(12):1141–1150. [RELOXYN]
Postuma RB et al. Risk and predictors of dementia and parkinsonism in idiopathic REM sleep behaviour disorder: a multicentre study. Brain 2019;142(3):744–759. [NAPS cohort]
Iranzo A et al. Neurodegenerative disease status and post-mortem pathology in idiopathic rapid-eye-movement sleep behaviour disorder. Lancet Neurol 2013;12(5):443–453.
Wellman A et al. A method for measuring and modeling the physiological traits causing obstructive sleep apnea. J Appl Physiol 2011;110(6):1627–1637. [PALM endotype framework]

Thai Context

Lohsoonthorn V et al. Prevalence of sleep problems in the Thai population. Sleep (Bangkok Metropolitan Sleep Study).
Thai Society of Sleep Medicine — Practice Guidelines for OSA Diagnosis and Treatment (2022 update).
Drug availability: Modafinil (special authorization); methylphenidate (narcotics license); gabapentin/pregabalin (NLEM); clonazepam (NLEM); melatonin (available OTC in Thailand). Sodium oxybate, pitolisant, solriamfetol, suvorexant, lemborexant, tasimelteon: NOT available in Thailand as of 2025.

10. Neuro-Oncology

This section provides a comprehensive subspecialist-depth review of neuro-oncology. Coverage includes the WHO 2021 integrated histomolecular classification of CNS tumors (IDH, 1p/19q, ATRX, TERT, EGFR, MGMT, H3 K27M/G34, BRAF), adult diffuse gliomas (astrocytoma, oligodendroglioma, GBM), pediatric gliomas (DIPG, pilocytic astrocytoma), GBM treatment (Stupp protocol, TTFields EF-14, MGMT-guided elderly management, recurrent GBM), targeted therapies (vorasidenib INDIGO, dabrafenib+trametinib, ONC201, checkpoint inhibitors, CAR-T, tumor vaccines), PCNSL (HD-MTX, MATRix, ASCT), meningioma (WHO 2021 molecular grading, Simpson), schwannoma, medulloblastoma, pituitary tumors, brain metastases (SRS, WBRT, driver mutation-targeted systemic therapy, leptomeningeal disease), paraneoplastic syndromes (PNS-Care 2021 criteria, antibody-syndrome-cancer associations), and neurological complications of cancer therapy (radiation necrosis, CIPN, immune checkpoint irAE, ICANS, PRES).

10.1 WHO 2021 CNS Tumor Classification — Integrated Histomolecular Approach

10.1.1 Paradigm Shift: From Histology to Molecular

The WHO 2021 Classification of CNS Tumors (5th edition) represents a fundamental paradigm shift: tumors are now classified using integrated histomolecular diagnosis rather than histology alone. Molecular markers can override histological grading (e.g., an IDH-wildtype diffuse astrocytoma with TERT promoter mutation is now classified as GBM, Grade 4, regardless of histological appearance).

Key Molecular Markers in WHO 2021

Marker	Method	Significance
IDH1/2 mutation	IHC (IDH1 R132H — covers ~90%); sequencing for non-canonical	Most important prognostic marker. IDH-mutant = better prognosis. Defines astrocytoma vs GBM (IDH-wt). All diffuse gliomas require IDH testing
1p/19q codeletion	FISH, CGH array, or methylation profiling	Defines oligodendroglioma (requires IDH-mut + 1p/19q codel). Predicts chemosensitivity (PCV). Best prognosis among diffuse gliomas
ATRX loss	IHC (loss of nuclear expression)	Characteristic of astrocytoma, IDH-mutant. Mutually exclusive with 1p/19q codeletion. Associated with ALT (alternative lengthening of telomeres)
TERT promoter mutation	PCR/sequencing (C228T, C250T)	Present in oligodendroglioma (with IDH-mut) and GBM (IDH-wt). In IDH-wt diffuse glioma: upgrades to GBM Grade 4
EGFR amplification	FISH, CGH, methylation	In IDH-wt diffuse glioma: upgrades to GBM Grade 4. EGFRvIII variant targetable
+7/−10	CGH, methylation profiling	Whole chromosome 7 gain + chromosome 10 loss. In IDH-wt: upgrades to GBM Grade 4
CDKN2A/B homozygous deletion	FISH, CGH	In IDH-mutant astrocytoma: upgrades to Grade 4 (regardless of histology). Worst prognosis among IDH-mutant tumors
MGMT promoter methylation	MSP, pyrosequencing	Predictive for temozolomide benefit in GBM. Methylated (~35–45%): better TMZ response, median OS 21.7 mo. Unmethylated: TMZ benefit uncertain
H3 K27M	IHC, sequencing	Defines diffuse midline glioma, H3 K27-altered (thalamus, brainstem, spinal cord). Grade 4. Children & young adults. Poor prognosis
H3 G34R/V	Sequencing	Defines diffuse hemispheric glioma, H3 G34-mutant. Grade 4. Hemispheric. Adolescents/young adults
BRAF V600E	IHC, PCR	Pleomorphic xanthoastrocytoma, ganglioglioma, pilocytic astrocytoma (rare). Targetable with dabrafenib + trametinib
KIAA1549-BRAF fusion	FISH, RNA sequencing	Pathognomonic for pilocytic astrocytoma (WHO Grade 1). Posterior fossa in children. Excellent prognosis

10.1.2 Adult-Type Diffuse Gliomas (WHO 2021)

WHO 2021 Classification of Adult-Type Diffuse Gliomas

Tumor Type	WHO Grade	Molecular Signature	Median Survival	Key Features
Astrocytoma, IDH-mutant	2, 3, or 4	IDH1/2 mutation + ATRX loss + NO 1p/19q codeletion. Grade 4 if CDKN2A/B homozygous deletion	Grade 2: 10–15 yr Grade 3: 5–8 yr Grade 4: 3–5 yr	Frontal/temporal lobes. T2/FLAIR hyperintense, non-enhancing (low grade) or enhancing (high grade). Can transform to higher grade over time
Oligodendroglioma, IDH-mutant & 1p/19q-codeleted	2 or 3	IDH1/2 mutation + 1p/19q codeletion + TERT promoter mutation (triple-positive)	Grade 2: 12–20 yr Grade 3: 7–12 yr	Best prognosis among diffuse gliomas. Cortical location, calcifications common. Exquisitely chemosensitive (PCV)
Glioblastoma, IDH-wildtype	4 (always)	IDH-wildtype + ≥1 of: EGFR amp, +7/−10, TERT promoter mutation. MGMT methylation = predictive	15–18 mo (MGMT+) 12–14 mo (MGMT−)	Most common malignant primary brain tumor. Ring-enhancing with central necrosis. Butterfly lesion (crosses corpus callosum). Stupp protocol standard

Clinical Pearl — The “Not Otherwise Specified” (NOS) vs. “Not Elsewhere Classified” (NEC) System: WHO 2021 introduces NOS (testing not performed/unavailable) and NEC (testing performed but results don’t match any defined entity). If IDH testing is unavailable: “Astrocytoma, NOS”. If tested but results are conflicting: “Astrocytoma, NEC”. This system ensures transparency about diagnostic certainty and is particularly relevant in resource-limited settings (e.g., Thailand where methylation profiling may not be readily available).

10.1.3 Pediatric-Type Diffuse Gliomas

Tumor	Grade	Molecular	Key Features
Diffuse midline glioma, H3 K27-altered	4	H3K27M mutation (H3.3 or H3.1) OR EZHIP overexpression	Thalamus, brainstem (DIPG), spinal cord. Children/young adults. Not resectable (midline location). RT is mainstay. Median survival ~11 months. ONC201 (HDAC/DRD2 agonist) showing promise
Diffuse hemispheric glioma, H3 G34-mutant	4	H3 G34R/V mutation	Cerebral hemispheres, adolescents/young adults. Aggressive. MGMT often methylated → TMZ may help
Diffuse pediatric-type high-grade glioma, PDGFRA-mutant	4	PDGFRA mutation/amplification	New WHO 2021 entity. Targetable with PDGFRA inhibitors (avapritinib, trial)

10.1.4 Circumscribed Astrocytic Gliomas

Tumor	Grade	Molecular	Key Features
Pilocytic astrocytoma	1	KIAA1549-BRAF fusion (~70%); BRAF V600E (~10%)	Most common pediatric brain tumor. Posterior fossa (cerebellum). Cystic with enhancing mural nodule. Excellent prognosis (>95% 10-yr survival). GTR curative in most
Pleomorphic xanthoastrocytoma (PXA)	2 (3 if ≥5 mitoses)	BRAF V600E (~70%)	Temporal lobe, cortical-based, young adults. Seizures. BRAF V600E targetable (dabrafenib + trametinib)
Subependymal giant cell astrocytoma (SEGA)	1	TSC1/TSC2 (tuberous sclerosis)	Near foramen of Monro; can cause hydrocephalus. Everolimus (mTOR inhibitor) shrinks SEGA without surgery (EXIST-1 trial)

Q: A 38-year-old man presents with new-onset seizures. MRI shows a non-enhancing T2/FLAIR hyperintense lesion in the left frontal lobe. Biopsy reveals a diffuse glioma. IHC shows IDH1 R132H positive, ATRX retained, and FISH confirms 1p/19q codeletion. TERT promoter mutation is detected. What is the integrated diagnosis, WHO grade, and prognosis?

Integrated diagnosis: Oligodendroglioma, IDH-mutant and 1p/19q-codeleted, WHO Grade 2 (assuming no anaplastic features on histology; Grade 3 if increased mitotic activity, microvascular proliferation, or necrosis).
Molecular profile: Triple-positive (IDH mutation + 1p/19q codeletion + TERT promoter mutation) = pathognomonic for oligodendroglioma in WHO 2021. ATRX is typically retained (loss would favor astrocytoma, but 1p/19q codeletion overrides).
Prognosis: Best among diffuse gliomas. Grade 2: median survival 12–20 years. Grade 3: 7–12 years. Exquisitely chemosensitive.
Treatment:
• Maximal safe resection (GTR if feasible without eloquent cortex damage; awake craniotomy with cortical mapping if near language/motor areas)
• If low-risk Grade 2 (age <40, GTR achieved): observation with serial MRI (q3–6 months year 1, then q6–12 months). Consider vorasidenib (IDH inhibitor)
• If high-risk Grade 2 (age ≥40, subtotal resection, >6 cm, crosses midline) or Grade 3: RT (54 Gy/30 fr) + PCV chemotherapy (RTOG 9802: RT + PCV vs RT alone: median OS 13.3 vs 7.8 years in high-risk low-grade glioma)

10.2 GBM Treatment — Standard of Care & Novel Therapies

10.2.1 Glioblastoma Standard of Care: The Stupp Protocol

Stupp Protocol (Stupp et al. NEJM 2005; Lancet Oncol 2009)

Phase	Treatment	Details
Surgery	Maximal safe resection	Goal: ≥98% extent of resection (EOR). 5-ALA fluorescence-guided surgery improves GTR rates (from ~35% to ~65%). Awake craniotomy for eloquent areas. Biopsy if unresectable
Concurrent chemoRT	RT 60 Gy / 30 fractions + TMZ 75 mg/m²/day	RT over 6 weeks. TMZ daily including weekends. PCP prophylaxis (TMP-SMX) during concurrent phase (lymphopenia risk). Weekly CBC
Adjuvant TMZ	TMZ 150–200 mg/m² days 1–5 / 28-day cycle	6 cycles (some extend to 12 if tolerated). Start cycle 1 at 150 mg/m²; escalate to 200 if tolerated. Monitor CBC
TTFields (Optune)	Alternating electric fields 200 kHz via scalp arrays	EF-14 trial (Stupp et al. JAMA 2015; JAMA 2017): TTFields + maintenance TMZ vs TMZ alone: median OS 20.9 vs 16.0 months; 5-year OS 13% vs 5%. Must be worn ≥18 h/day for benefit. Scalp irritation is main side effect. No systemic toxicity

MGMT Methylation: The Critical Biomarker

MGMT Status	Significance	Treatment Implications
Methylated (~35–45%)	MGMT gene silenced → reduced DNA repair → TMZ more effective	Full Stupp protocol. Median OS 21.7 months (vs 12.7 unmethylated). Strongest predictor of TMZ benefit. Consider MGMT-enriched clinical trials
Unmethylated (~55–65%)	MGMT active → repairs TMZ-induced DNA damage → TMZ less effective	Still receives Stupp (modest benefit even in unmethylated). Consider clinical trials as first-line. RT alone reasonable in elderly with poor KPS. Lomustine (CCNU) alternative

Elderly & Frail GBM Patients

Age/KPS	MGMT Status	Recommended Treatment	Evidence
≥70 yr, KPS ≥60	Methylated	Hypofractionated RT (40 Gy/15 fr) + TMZ	Perry et al. NEJM 2017 (CE.6/EORTC 26062): short-course RT + TMZ vs RT alone in elderly: OS 9.3 vs 7.6 mo
≥70 yr, KPS ≥60	Unmethylated	Hypofractionated RT (40 Gy/15 fr) alone	TMZ adds toxicity without clear benefit if MGMT unmethylated in elderly
Any age, KPS <60	Methylated	TMZ alone (if MGMT+)	NOA-08 (Wick et al. Lancet Oncol 2012): TMZ non-inferior to RT in elderly MGMT+ GBM
Any age, KPS <60	Unmethylated	RT alone (25 Gy/5 fr ultra-short) or best supportive care	Palliative approach; ultra-short RT for symptom palliation

10.2.2 Recurrent GBM

Treatment	Details	Evidence
Bevacizumab	Anti-VEGF monoclonal antibody; 10 mg/kg q2w	FDA-approved for recurrent GBM (2009). Improves PFS (4.2 vs 1.5 mo) but NOT overall survival. Reduces steroid requirements, improves quality of life. Main toxicities: hypertension, proteinuria, wound healing, hemorrhage, VTE. AVAglio (Chinot et al. NEJM 2014) and RTOG 0825: no OS benefit as first-line addition to Stupp
Lomustine (CCNU)	Alkylating agent; 110–130 mg/m² q6w	Standard comparator in recurrent GBM trials. May combine with bevacizumab. CeTeG/NOA-09 (Herrlinger et al. Lancet 2019): CCNU + TMZ vs TMZ alone in MGMT+ GBM: OS 48.1 vs 31.4 mo (provocative but small study)
Re-resection	If recurrence is resectable and KPS good	Retrospective data supports survival benefit if ≥80% EOR at second surgery. Consider LITT (laser interstitial thermal therapy) for deep lesions
Re-irradiation	SRS or hypofractionated re-RT for focal recurrence	Case-by-case; cumulative brain dose constraints. SRS 15–18 Gy for small recurrences

10.2.3 Targeted & Novel Therapies in Gliomas

Emerging Targeted Therapies in Neuro-Oncology

Therapy	Target	Tumor Type	Evidence
Vorasidenib (Voranigo)	IDH1/2 dual inhibitor (brain-penetrant)	IDH-mutant Grade 2 glioma (astrocytoma or oligodendroglioma)	INDIGO trial (Mellinghoff et al. NEJM 2023): vorasidenib vs placebo in residual/recurrent Grade 2 IDH-mutant glioma: PFS 27.7 vs 11.1 months (HR 0.39); 2-year PFS 63% vs 29%. FDA approved Aug 2024. First targeted therapy for low-grade glioma. Well-tolerated (ALT elevation main AE, monitor LFTs)
Dabrafenib + Trametinib	BRAF V600E + MEK	BRAF V600E-mutant glioma (PXA, ganglioglioma, pilocytic, rare GBM)	ROAR basket trial (Wen et al. Lancet Oncol 2022): ORR 33% in high-grade glioma, 69% in low-grade. FDA approved for BRAF V600E solid tumors including glioma
ONC201 (dordaviprone)	DRD2 agonist / ClpP activator	H3 K27M-altered diffuse midline glioma (DIPG)	Breakthrough therapy designation. Showed radiographic responses and survival benefit in H3K27M gliomas. Oral, well-tolerated. Phase 3 ongoing
Checkpoint inhibitors (anti-PD-1/PD-L1)	PD-1/PD-L1	GBM	CheckMate 143 (Reardon et al. JAMA Oncol 2020): nivolumab vs bevacizumab in recurrent GBM: NO OS benefit. GBM is immunologically “cold” (low TMB, immunosuppressive microenvironment). Hypermutated (MMR-deficient) GBM may respond. Neoadjuvant anti-PD-1 before resection showing promise (Cloughesy et al. Nat Med 2019)
CAR-T cell therapy	EGFRvIII, IL-13Rα2, GD2, HER2	Recurrent GBM, DIPG	Phase 1/2 trials. GD2-CAR-T for H3K27M DIPG: dramatic radiographic responses (Majzner et al. Nature 2022). CRS monitoring required. Intraventricular/intratumoral delivery being explored
Tumor vaccines	DCVax-L (dendritic cell), EGFRvIII peptide, survivin	GBM	DCVax-L (Liau et al. JAMA Oncol 2023): autologous dendritic cell vaccine + Stupp: median OS 19.3 mo (entire cohort), 30.2 mo in MGMT-methylated. Phase 3 completed but mixed interpretation

Clinical Pearl — Pseudoprogression vs. True Progression: After chemoRT, up to 20–30% of GBM patients show transient increase in enhancement on MRI within the first 3 months (pseudoprogression — actually treatment effect from TMZ-induced DNA damage + inflammation). More common in MGMT-methylated tumors. RANO criteria (2010): do not declare progression within 12 weeks of completing RT unless new lesion outside radiation field or pathological confirmation. Advanced MRI techniques to differentiate: MR perfusion (rCBV ↓ in pseudoprogression, ↑ in true progression), MR spectroscopy (choline/NAA ratio), amino acid PET (¹⁸F-FET PET superior to MRI for distinguishing).

Q: A 62-year-old man undergoes subtotal resection of a right temporal GBM (IDH-wildtype, MGMT promoter methylated, EGFR amplified). KPS is 80. How should he be treated, and what is his expected prognosis?

Treatment: Full Stupp protocol + TTFields:
1. Concurrent phase: RT 60 Gy/30 fractions + daily TMZ 75 mg/m² × 6 weeks. PCP prophylaxis with TMP-SMX. Weekly CBC
2. Adjuvant phase: TMZ 150–200 mg/m² days 1–5 q28 days × 6–12 cycles + TTFields (Optune) ≥18 h/day
3. Supportive: Dexamethasone for edema (taper as tolerated); levetiracetam if seizures; VTE prophylaxis
Prognosis: MGMT methylated = favorable subgroup. Expected median OS ~21–23 months with full Stupp + TTFields. EGFR amplification confirms GBM Grade 4 molecular diagnosis but doesn’t currently change standard treatment (no effective anti-EGFR therapy for GBM yet, though EGFRvIII-targeted approaches in trials).
At recurrence: Consider bevacizumab + lomustine, re-resection if feasible, re-irradiation (SRS), or clinical trial enrollment.

10.3 Primary CNS Lymphoma (PCNSL)

10.3.1 Overview

PCNSL is a rare aggressive non-Hodgkin lymphoma confined to the CNS (brain, leptomeninges, eyes, spinal cord) without systemic involvement at diagnosis. Histology: >95% Diffuse Large B-Cell Lymphoma (DLBCL). Incidence: ~0.5/100,000 (increasing in immunocompetent elderly). Two distinct populations: (1) immunocompromised (HIV/AIDS, post-transplant — decreasing with ART) and (2) immunocompetent elderly (>60y — increasing).

10.3.2 Clinical Features & Diagnosis

Feature	Details
Presentation	Focal neurological deficits (70%), cognitive/behavioral change (43%), raised ICP (33%), seizures (14%), ocular symptoms (10–20% — vitreous/retinal infiltration)
MRI pattern	Immunocompetent: homogeneously enhancing, periventricular/callosal, often multifocal (40%). Immunocompromised: ring-enhancing (mimics toxoplasmosis). Restricted diffusion (high cellularity). Low rCBV on perfusion (unlike GBM which has high rCBV)
Key diagnostic rule	DEFER STEROIDS until biopsy — corticosteroids cause rapid tumor lysis (“ghost tumor”) making histological diagnosis impossible. If steroids given and tumor shrinks, must wait for regrowth before biopsy
Workup	MRI brain + spine with Gd; stereotactic biopsy (NOT resection); slit-lamp examination (ocular involvement); CSF: cytology, flow cytometry, IL-10 ↑ / IL-6 ↓ (IL-10:IL-6 ratio >1); CT chest/abdomen/pelvis + PET to exclude systemic lymphoma; HIV testing; testicular US in elderly men

Clinical Pearl — PCNSL vs. GBM on MRI: Both can be periventricular and enhance. Key differentiators: (1) PCNSL: homogeneous enhancement (immunocompetent), restricted diffusion (DWI bright/ADC dark = high cellularity), low perfusion (rCBV ratio ~1–2). (2) GBM: ring enhancement with central necrosis, high perfusion (rCBV ratio >2–4), spectroscopy: high choline, lipid peak. (3) Response to steroids: PCNSL dramatically shrinks; GBM minimally responds.

10.3.3 Treatment

PCNSL Treatment Algorithm

Phase	Treatment	Details
Induction	High-dose methotrexate (HD-MTX)-based	HD-MTX 3.5 g/m² (minimum ≥3 g/m²) q2w × 4–8 cycles. Leucovorin rescue 24h after MTX. Aggressive hydration + urine alkalinization (pH >7). Monitor creatinine (MTX nephrotoxicity). MATRix regimen: MTX + cytarabine + thiotepa + rituximab (Ferreri et al. Lancet Haematol 2016) — highest CR rate (~49%)
Consolidation (fit patients)	HD-ASCT (thiotepa-based)	Thiotepa + BCNU conditioning → autologous stem cell transplant. Best long-term outcomes: 5-year PFS ~75%. IELSG32 (Ferreri et al. Lancet Haematol 2017): ASCT superior to WBRT consolidation
Consolidation (unfit/elderly)	Reduced-dose WBRT (23.4 Gy) or maintenance lenalidomide/ibrutinib	WBRT causes severe neurotoxicity (leukoencephalopathy, cognitive decline) especially in elderly — avoid full-dose (45 Gy) WBRT if possible
Relapsed/Refractory	Ibrutinib (BTK inhibitor), lenalidomide, HD-MTX re-challenge, temozolomide ± rituximab	Ibrutinib: CNS penetrant, ~50–70% ORR in relapsed PCNSL. LOC trial: lenalidomide + rituximab maintenance

CRITICAL: NO surgical resection for PCNSL (infiltrative, often multifocal; resection does not improve outcomes and delays chemotherapy). Stereotactic biopsy only.

10.4 Meningioma & Other Extra-Axial/Primary Tumors

10.4.1 Meningioma

Most common primary intracranial tumor (~38% of all primary CNS tumors). Arises from meningothelial cells of the arachnoid. WHO 2021 grading incorporates molecular markers alongside histology.

Meningioma WHO 2021 Grading

Grade	Frequency	Histology/Molecular	5-Year Recurrence	Management
WHO 1	~80%	Benign histology (9 subtypes including meningothelial, fibrous, transitional, psammomatous). NF2 mutation most common (~60%)	5–10%	Observation (small, asymptomatic); Surgery (Simpson Grade I–III); SRS for residual or unresectable (≤3 cm)
WHO 2	~15–18%	Atypical (4–19 mitoses/10 HPF or ≥3 of 5 criteria: sheeting, spontaneous necrosis, prominent nucleoli, high cellularity, small cells). Brain invasion alone upgrades to Grade 2. Molecular: TERT promoter mutation, homozygous CDKN2A/B deletion	30–40%	Surgery + adjuvant RT (50–54 Gy; especially if STR or brain invasion)
WHO 3	~2–5%	Anaplastic/malignant (≥20 mitoses, frank malignant cytology). Any grade with TERT promoter mutation AND/OR CDKN2A/B homozygous deletion → Grade 3 regardless of histology	50–80%	Surgery + adjuvant RT (59.4–60 Gy). No proven systemic therapy; clinical trials (pembrolizumab, FAK inhibitors, sunitinib)

Simpson Grading of Meningioma Resection

Grade	Definition	10-Year Recurrence
I	GTR including dural attachment and involved bone	9%
II	GTR + coagulation of dural attachment	19%
III	GTR without dural resection/coagulation	29%
IV	Subtotal resection	39%
V	Biopsy only / decompression	>50%

10.4.2 Other Primary CNS Tumors

Tumor	Key Features	Treatment
Schwannoma (Vestibular)	CN VIII at cerebellopontine angle. Unilateral hearing loss + tinnitus + imbalance. T1 Gd+ enhancing. Bilateral = NF2. WHO Grade 1	Observation (small, stable); SRS (Gamma Knife ≤3 cm: 95% tumor control); Surgery (translabyrinthine/retrosigmoid if large/symptomatic)
Ependymoma	Posterior fossa (children) or spinal cord (adults — myxopapillary at conus/filum). Molecular: ZFTA-RELA fusion (supratentorial, Grade 3); PFA/PFB (posterior fossa). WHO 2021: Grade 2–3	Maximal safe resection + RT (local, 54–59.4 Gy). Chemotherapy limited role (except in very young children to defer RT)
Medulloblastoma	Most common malignant pediatric brain tumor. Posterior fossa (4th ventricle). WHO 2021 molecular groups: WNT (best prognosis, >95% survival), SHH (intermediate), Group 3 (worst, MYC amplified), Group 4 (intermediate, most common)	Surgery + craniospinal irradiation (CSI 23.4–36 Gy) + boost + chemotherapy (cisplatin, vincristine, CCNU). WNT-type: de-escalation trials ongoing. SHH: vismodegib/sonidegib (Hedgehog inhibitors)
Pituitary adenoma / PitNET	Most common sellar tumor. Functional (prolactinoma 40%, GH-secreting 20%, ACTH 10%, non-functioning 30%). WHO 2022: “pituitary neuroendocrine tumor (PitNET)” replaces “adenoma.” MRI: sellar mass ± suprasellar extension (visual field defect — bitemporal hemianopia)	Prolactinoma: cabergoline (DA agonist; first-line, even for macroadenomas). Non-functioning/GH/ACTH: transsphenoidal surgery. Radiotherapy for residual/recurrent. Temozolomide for aggressive PitNET (ESE guideline 2018)
Craniopharyngioma	Suprasellar, bimodal (children 5–14y + adults 50–75y). Adamantinomatous (calcified, cystic; CTNNB1/β-catenin) vs papillary (BRAF V600E). Visual loss, hypopituitarism, DI	Surgery (transcranial or endoscopic endonasal). Papillary with BRAF V600E: dabrafenib + trametinib (dramatic responses). Proton therapy for residual

Clinical Pearl — The NF Syndromes in Neuro-Oncology: NF1 (chr 17, neurofibromin): optic pathway gliomas, neurofibromas, plexiform neurofibromas (→ MPNST risk), FASI (focal areas of signal intensity). NF2 (chr 22, merlin/schwannomin): bilateral vestibular schwannomas (diagnostic), meningiomas, ependymomas. Schwannomatosis (SMARCB1/LZTR1): multiple schwannomas WITHOUT vestibular schwannomas; chronic pain prominent. For NF2: bevacizumab can stabilize/shrink vestibular schwannomas (hearing improvement in ~40%).

10.5 Brain Metastases & Leptomeningeal Disease

10.5.1 Brain Metastases

Brain metastases are the most common intracranial tumors in adults (×10 more common than primary brain tumors). Prevalence increasing due to improved systemic cancer control with longer survival and better neuroimaging detection. Occur in 20–40% of all cancer patients.

Primary Cancer	Frequency of Brain Mets	Key Features
Lung (NSCLC, SCLC)	40–50% (most common)	NSCLC: driver mutations (EGFR, ALK, ROS1) have high brain tropism; SCLC: prophylactic cranial irradiation (PCI) reduces incidence
Breast	15–25%	HER2+ and triple-negative have highest brain metastasis rates. HER2+: T-DXd (trastuzumab deruxtecan) CNS activity
Melanoma	40–60% (at autopsy)	Often hemorrhagic. Highly responsive to immunotherapy (anti-PD-1 + anti-CTLA-4). BRAF V600E: dabrafenib + trametinib CNS-penetrant
Renal cell carcinoma	5–10%	Often hemorrhagic. SRS preferred. Checkpoint inhibitors active
Colorectal	3–5%	Less common but increasing. Usually late in disease course

Imaging Characteristics

Typically at gray-white matter junction (hematogenous spread trapped at terminal arterioles). Multiple in 70–80%. Ring or solid enhancement. Surrounding vasogenic edema. Distribution: cerebral hemispheres (80%) > cerebellum (15%) > brainstem (5%).

Hemorrhagic brain mets: melanoma, RCC, choriocarcinoma, thyroid. Mnemonic: “MR CT” (Melanoma, Renal, Choriocarcinoma, Thyroid).

10.5.2 Treatment of Brain Metastases

Brain Metastases Treatment Algorithm

Scenario	Treatment	Evidence
1–4 brain mets, good KPS	SRS (Stereotactic Radiosurgery) ± surgery (if large/symptomatic/diagnostic uncertainty)	SRS: single fraction 15–24 Gy (Gamma Knife, CyberKnife, LINAC). Brown et al. JAMA 2016: SRS alone vs SRS + WBRT: no OS difference, better cognition with SRS alone. Post-op SRS to cavity preferred over WBRT
Single large met (>3–4 cm)	Surgery + post-op SRS to cavity	Mahajan et al. Lancet Oncol 2017: post-op SRS reduces local recurrence from 43% to 28%. Avoids WBRT cognitive toxicity
Multiple (>4) mets	WBRT (30 Gy/10 fr or 37.5 Gy/15 fr) or SRS if ≤10–15 mets (evolving)	QUARTZ (Mulvenna et al. Lancet 2016): WBRT vs BSC in NSCLC brain mets with poor prognosis: NO survival benefit from WBRT. Hippocampal-sparing WBRT + memantine reduces cognitive toxicity (NRG CC001 (Brown et al. JCO 2020))
Driver mutation-positive NSCLC	Targeted therapy with CNS activity	Osimertinib (EGFR): IC ORR ~70–90% (FLAURA); Lorlatinib (ALK): IC ORR ~80%; Selpercatinib (RET); Capmatinib (MET). Deferral of RT reasonable in asymptomatic mets responding to systemic therapy
Melanoma brain mets	Immunotherapy (anti-PD-1 + anti-CTLA-4)	ABC trial (Long et al. Lancet Oncol 2018): nivolumab + ipilimumab: IC ORR 46–57% in treatment-naive melanoma brain mets. BRAF V600E: dabrafenib + trametinib: IC ORR ~55%

10.5.3 Leptomeningeal Carcinomatosis (LMC)

Feature	Details
Definition	Neoplastic infiltration of leptomeninges/CSF. Occurs in ~5–8% of solid tumors and ~5–15% of hematologic malignancies
Common primaries	Breast (most common), lung (NSCLC), melanoma, hematologic (ALL, lymphoma)
Presentation	Multifocal neurological deficits: cranial neuropathies (CN III, VI, VII, VIII common), radiculopathy, headache, nausea/vomiting, cognitive decline, hydrocephalus
Diagnosis	CSF cytology (sensitivity ~50% first LP; ≥70% with repeat LP). CSF: ↑protein, ↓glucose, ↑cell count. CSF flow cytometry (lymphoma). Cell-free tumor DNA (cfDNA) in CSF (emerging). MRI with Gd: leptomeningeal enhancement, nodular deposits, cranial nerve enhancement, “sugar coating” of brain surface
Treatment	Prognosis is poor (median OS 2–4 months). Intrathecal chemotherapy: methotrexate 12 mg or cytarabine (liposomal: DepoCyt) via Ommaya reservoir. Systemic therapy: high-dose MTX, targeted agents with CNS penetration. Focal RT for bulky disease or symptomatic sites. VP shunt for symptomatic hydrocephalus

10.5.4 Paraneoplastic Neurological Syndromes (PNS)

Immune-mediated neurological disorders triggered by systemic cancer. Antibody classification divides into intracellular (onconeural, T-cell mediated, often irreversible) vs. cell-surface/synaptic (antibody-mediated, potentially reversible with immunotherapy).

Major Paraneoplastic Syndromes & Antibodies

Syndrome	Antibody	Cancer	Key Features	Response to Immunotherapy
Limbic encephalitis	Anti-Hu (ANNA-1); anti-CV2/CRMP5; anti-Ma2; anti-LGI1; anti-CASPR2; anti-AMPAR*	SCLC (Hu); testicular germ cell (Ma2); thymoma (LGI1, CASPR2)	Subacute memory loss, seizures, psychiatric symptoms. MRI: medial temporal T2/FLAIR hyperintensity	Intracellular Ab: poor. Cell-surface Ab: good*
Anti-NMDAR encephalitis	Anti-NMDAR (GluN1)	Ovarian teratoma (40–60% in young women); may be non-paraneoplastic	Young women; psychiatric → seizures → movement disorder (orofacial dyskinesias) → autonomic instability → coma. See Section 5	Excellent (80% with tumor removal + immunotherapy)
Subacute cerebellar degeneration	Anti-Yo (PCA-1); anti-Tr (DNER); anti-Hu; anti-CV2; anti-mGluR1	Ovarian/breast (Yo); Hodgkin lymphoma (Tr); SCLC (Hu)	Rapidly progressive pancerebellar ataxia (weeks). Purkinje cell loss. Often irreversible	Intracellular Ab (Yo, Hu): poor. Anti-Tr: moderate. Tumor treatment may stabilize
Sensory neuronopathy	Anti-Hu (ANNA-1)	SCLC	Progressive, asymmetric sensory loss (all modalities); sensory ataxia; areflexia. DRG neurons destroyed. Painful	Poor (intracellular target)
Lambert-Eaton Myasthenic Syndrome (LEMS)	Anti-VGCC (P/Q type)	SCLC (50–60%); 40% autoimmune without cancer	Proximal weakness (legs > arms), hyporeflexia that IMPROVES with activity, autonomic dysfunction (dry mouth). EMG: low CMAP, ↑>100% post-exercise facilitation	Good (3,4-DAP + treat cancer; IVIg for autoimmune)
Opsoclonus-myoclonus syndrome	Anti-Ri (ANNA-2); often no detectable Ab in children	Neuroblastoma (children); breast, SCLC (adults)	“Dancing eyes, dancing feet”: chaotic saccadic eye movements + myoclonus + ataxia	Children: moderate (rituximab). Adults: variable
Stiff Person Syndrome	Anti-amphiphysin (paraneoplastic); anti-GAD65 (usually autoimmune)	Breast (amphiphysin); rarely thymoma	Progressive axial rigidity + painful spasms. Hyperexcitable motor neurons	Amphiphysin: poor. GAD65: moderate (benzodiazepines, IVIg, rituximab)

*Cell-surface antibodies (LGI1, CASPR2, AMPAR, NMDAR) are often autoimmune rather than strictly paraneoplastic but cancer screening is essential.

Clinical Pearl — PNS Diagnosis: The 2021 Updated Criteria: The Graus et al. J Neurol Neurosurg Psychiatry 2021 updated PNS diagnostic criteria introduce a PNS-Care Score (0–14 points) incorporating: clinical phenotype (high/intermediate/low risk), antibody type (high/intermediate-risk), and cancer presence. Score ≥8 = definite PNS; 6–7 = probable; <6 = possible. Key principle: treat the cancer AND the immune response simultaneously. For intracellular antibodies: cancer treatment is the primary intervention (immunotherapy often ineffective). For cell-surface antibodies: aggressive immunotherapy (steroids, IVIg, PLEX, rituximab) + tumor removal.

Q: A 58-year-old female smoker presents with subacute onset of confusion, memory loss, and new-onset seizures over 3 weeks. MRI shows bilateral medial temporal T2/FLAIR hyperintensity without enhancement. CSF shows mild lymphocytic pleocytosis (15 cells) and normal glucose. EEG shows temporal slowing. What is the differential, workup, and management approach?

Differential: (1) Autoimmune/paraneoplastic limbic encephalitis (most likely given subacute onset, medial temporal MRI signal, CSF pleocytosis); (2) Viral encephalitis (HSV — but typically unilateral, fever, hemorrhagic); (3) GBM (unlikely without enhancement); (4) Neurosyphilis; (5) Status epilepticus with hippocampal edema.
Workup:
1. Serum + CSF autoimmune encephalitis panel: anti-LGI1, anti-CASPR2, anti-AMPAR, anti-Hu, anti-CV2, anti-Ma2, anti-NMDAR, anti-GABA-B
2. CSF HSV PCR (must exclude HSV encephalitis — empiric acyclovir while pending)
3. CT chest/abdomen/pelvis (cancer screening — SCLC most common cause of paraneoplastic limbic encephalitis in smokers)
4. Whole-body PET-CT (if initial CT negative; detects occult cancer in 30–40%)
5. CSF cytology, RPR, additional standard CSF studies
Management (presumptive autoimmune/paraneoplastic LE):
1. Empiric acyclovir until HSV PCR negative
2. Start immunotherapy empirically (don’t wait for antibody results): IV methylprednisolone 1 g/day × 5 days + IVIg 0.4 g/kg/day × 5 days
3. ASM for seizures: levetiracetam 1000–1500 mg BID (avoid sodium-channel blockers if anti-LGI1 suspected — these patients often have faciobrachial dystonic seizures)
4. Aggressive cancer search and treatment (if anti-Hu positive: search for SCLC even if CT negative; if anti-Ma2: testicular exam + US)

10.6 Neuro-Oncologic Emergencies & Seizure Management

10.6.1 Raised Intracranial Pressure & Herniation

Emergency	Management
Vasogenic edema (peri-tumoral)	Dexamethasone: 10 mg IV bolus → 4–8 mg q6h. Mechanism: reduces BBB permeability, decreases edema. Onset: 24–72 hours. Taper as soon as possible (steroid myopathy, immunosuppression, hyperglycemia, psychiatric effects). Bevacizumab for steroid-refractory edema (radiation necrosis, recurrent GBM)
Obstructive hydrocephalus	EVD (external ventricular drain) for acute. VP shunt or ETV for subacute/chronic. Dexamethasone as bridge. Common with posterior fossa tumors, colloid cyst, pineal tumors
Impending herniation	Head of bed 30°; IV mannitol 1–1.5 g/kg OR hypertonic saline 23.4% 30 mL bolus; dexamethasone 10 mg IV; hyperventilation (target pCO₂ 30–35 mmHg, temporizing); urgent neurosurgical consultation for decompression/EVD

10.6.2 Seizure Management in Brain Tumors

Seizures in Brain Tumors

Aspect	Details
Prevalence	Low-grade glioma: 60–90% (seizure often the presenting symptom); GBM: 30–50%; Meningioma: 20–40%; Brain metastases: 20–35%
ASM choice	Levetiracetam (first-line): no enzyme induction, no drug interactions with chemotherapy, IV formulation. 500–1500 mg BID. Lacosamide: good alternative (no interactions, IV available). Avoid enzyme-inducing ASMs (phenytoin, carbamazepine, phenobarbital) — reduce efficacy of chemotherapy (TMZ, irinotecan) and dexamethasone metabolism. Valproate: consider in IDH-mutant glioma (possible HDAC inhibitor synergy with TMZ — retrospective data, not proven)
Prophylaxis	NOT recommended for routine seizure prophylaxis in brain tumor patients who have not had seizures (AAN Practice Parameter 2000; reaffirmed 2019). Exception: perioperative (1–2 weeks post-craniotomy), then taper if no seizures. Prophylaxis reasonable in melanoma mets (high hemorrhage risk)
Status epilepticus	Standard SE protocol (benzodiazepines → LEV/VPA/fosphenytoin). Address underlying cause: tumor progression? hemorrhage into tumor? metabolic (hyponatremia from TMZ, SIADH)? infection (immunosuppressed)?

Clinical Pearl — Drug Interactions in Neuro-Oncology: This is a critical area where neurologists must coordinate with oncologists. Key interactions: (1) Enzyme-inducing ASMs (phenytoin, carbamazepine, oxcarbazepine) reduce levels of: TMZ, irinotecan, vincristine, dexamethasone, targeted agents (osimertinib, lorlatinib). Always use non-enzyme-inducing ASMs (levetiracetam, lacosamide, brivaracetam). (2) Dexamethasone is a CYP3A4 inducer: affects some targeted therapies. (3) TMZ + valproate: VPA may increase TMZ-related myelosuppression (monitor CBC closely).

10.6.3 Neurological Complications of Cancer Treatment

Neurological Toxicity of Cancer Therapies

Therapy	Neurological Complication	Management
Radiation (cranial)	Acute (days): cerebral edema, worsening symptoms → dexamethasone. Early-delayed (1–6 mo): somnolence syndrome (children), pseudoprogression → observe, steroids. Late (>6 mo): radiation necrosis (focal, enhancing — mimics recurrence; diagnose with perfusion MRI + amino acid PET; treat with bevacizumab), leukoencephalopathy, cognitive decline, endocrinopathy, radiation-induced tumors (meningioma, GBM), cavernomas	Radiation necrosis: bevacizumab 7.5 mg/kg q3w (most effective); dexamethasone; surgery if refractory. Cognitive decline: cognitive rehabilitation; memantine (with hippocampal-sparing WBRT)
Immune checkpoint inhibitors (anti-PD-1, anti-CTLA-4)	Immune-related neurological adverse events (irAE): myasthenia gravis (most dangerous), Guillain-Barré, encephalitis, meningitis, hypophysitis, myelitis, peripheral neuropathy. Overlap syndromes (MG + myositis + myocarditis = “triple M”)	Grade 1: observe. Grade 2: hold ICI + prednisone 0.5–1 mg/kg. Grade 3–4: permanently discontinue ICI + high-dose methylprednisolone 1–2 mg/kg/day. IVIg/PLEX for MG, GBS. Myocarditis: urgent cardiology consult
Chemotherapy-induced peripheral neuropathy (CIPN)	Platinum (cisplatin, oxaliplatin): sensory > motor, DRG neurotoxicity. Taxanes: predominantly sensory. Vincristine: mixed sensorimotor, autonomic (constipation). Bortezomib: painful, small fiber	Prevention: limited evidence (only duloxetine for treatment). Treatment: duloxetine 60 mg/day (Smith et al. JAMA 2013: modest benefit for CIPN pain). Gabapentin/pregabalin for neuropathic pain. Dose reduction/modification of causative agent
CAR-T cell therapy	ICANS (Immune Effector Cell-Associated Neurotoxicity Syndrome): confusion, aphasia, seizures, cerebral edema. Often follows CRS. ICE score for grading (Immune Effector Cell-Associated Encephalopathy)	Grade 1–2: supportive, dexamethasone 10 mg q6h. Grade 3: dexamethasone 10 mg q6h + consider tocilizumab if concurrent CRS. Grade 4: methylprednisolone 1 g/day, ICU, seizure prophylaxis (levetiracetam)
Posterior Reversible Encephalopathy Syndrome (PRES)	Associated with: cyclosporine, tacrolimus, bevacizumab, cisplatin, checkpoint inhibitors, hypertension. Headache, seizures, visual disturbance, confusion. MRI: posterior white matter vasogenic edema (parieto-occipital)	Discontinue/reduce causative agent. Aggressive BP control. ASMs for seizures. Usually reversible if treated promptly

Q: A 45-year-old woman with known Grade 2 oligodendroglioma (IDH-mutant, 1p/19q-codeleted) on surveillance imaging shows a new 2 cm enhancing nodule within the known T2 lesion. She has been seizure-free on levetiracetam 1000 mg BID. What does the new enhancement suggest, and what is the next step?

Concern: New enhancement within a previously non-enhancing low-grade glioma strongly suggests malignant transformation (anaplastic progression to Grade 3). Oligodendrogliomas can transform over time, though their transformation rate is lower than IDH-mutant astrocytomas.
Differential of new enhancement: (1) Anaplastic transformation (most likely); (2) Treatment-related change (if recent RT/chemo — not applicable here on surveillance); (3) Seizure-related transient enhancement (unlikely if seizure-free); (4) Radiation necrosis (if prior RT)
Next steps:
1. Advanced MRI: perfusion (rCBV ↑ in high-grade), spectroscopy (choline/NAA ↑), DWI
2. Consider amino acid PET (¹⁸F-FET PET) if available — more specific than MRI for distinguishing high-grade from low-grade regions
3. Neurosurgical consultation for resection/biopsy of the enhancing component to confirm grade
4. If confirmed Grade 3: RT (59.4 Gy) + PCV chemotherapy (CODEL trial (ongoing): RT + PCV vs RT + TMZ in 1p/19q-codeleted anaplastic oligodendroglioma)
5. Continue levetiracetam (non-enzyme-inducing; compatible with PCV chemotherapy)
6. Consider vorasidenib if the patient is not a candidate for immediate aggressive treatment (IDH-mutant low-grade residual component)

10.7 References & Key Guidelines

Key References & Guidelines

Classification & Molecular

Louis DN et al. The 2021 WHO Classification of Tumors of the Central Nervous System: a summary. Neuro Oncol 2021;23(8):1231–1251.
Brat DJ et al. cIMPACT-NOW Update 3: recommended diagnostic criteria for “diffuse astrocytic glioma, IDH-wildtype, with molecular features of glioblastoma, WHO grade IV.” Acta Neuropathol 2018;136(5):805–810.

Landmark Trials

Stupp R et al. Radiotherapy plus concomitant and adjuvant temozolomide for glioblastoma. N Engl J Med 2005;352:987–996. [Stupp Protocol]
Stupp R et al. Effect of tumor-treating fields plus maintenance temozolomide vs maintenance temozolomide alone on survival in patients with glioblastoma: a randomized clinical trial. JAMA 2017;318(23):2306–2316. [EF-14 — TTFields]
Mellinghoff IK et al. Vorasidenib in IDH1- or IDH2-mutant low-grade glioma. N Engl J Med 2023;389(7):589–601. [INDIGO]
Perry JR et al. Short-course radiation plus temozolomide in elderly patients with glioblastoma. N Engl J Med 2017;376:1027–1037. [CE.6/EORTC 26062-22061]
Buckner JC et al. Radiation plus procarbazine, CCNU, and vincristine in low-grade glioma. N Engl J Med 2016;374:1344–1355. [RTOG 9802]
Herrlinger U et al. Lomustine-temozolomide combination therapy versus standard temozolomide therapy in patients with newly diagnosed glioblastoma with methylated MGMT promoter (CeTeG/NOA-09). Lancet 2019;393:678–688.
Chinot OL et al. Bevacizumab plus radiotherapy-temozolomide for newly diagnosed glioblastoma. N Engl J Med 2014;370:709–722. [AVAglio]
Ferreri AJM et al. MATRix regimen for primary CNS lymphoma. Lancet Haematol 2016;3(5):e217–e227.
Brown PD et al. Postoperative stereotactic radiosurgery compared with whole brain radiotherapy for resected metastatic brain disease (NCCTG N107C/CEC-3). Lancet Oncol 2017;18(8):1049–1060.
Brown PD et al. Hippocampal avoidance during whole-brain radiotherapy plus memantine for patients with brain metastases: NRG CC001. J Clin Oncol 2020;38(10):1019–1029.
Mulvenna P et al. Dexamethasone and supportive care with or without whole brain radiotherapy in treating patients with non-small cell lung cancer with brain metastases unsuitable for resection or stereotactic radiosurgery (QUARTZ). Lancet 2016;388(10055):2004–2014.

Paraneoplastic & Complications

Graus F et al. Updated diagnostic criteria for paraneoplastic neurologic syndromes. Neurol Neuroimmunol Neuroinflamm 2021;8(4):e1014. [PNS-Care Score]
Glantz MJ et al. Practice parameter: anticonvulsant prophylaxis in patients with newly diagnosed brain tumors. Neurology 2000;54(10):1886–1893. [AAN — no routine prophylaxis]
Smith EML et al. Effect of duloxetine on pain, function, and quality of life among patients with chemotherapy-induced painful peripheral neuropathy. JAMA 2013;309(13):1359–1367.
Reardon DA et al. Effect of nivolumab vs bevacizumab in patients with recurrent glioblastoma: the CheckMate 143 Phase 3 Randomized Clinical Trial. JAMA Oncol 2020;6(7):1003–1010.
Majzner RG et al. GD2-CAR T cell therapy for H3K27M-mutated diffuse midline gliomas. Nature 2022;603:934–941.

11. Spinal Cord Disorders

This section provides a comprehensive subspecialist-depth review of spinal cord disorders. Coverage includes traumatic SCI (ASIA/ISNCSCI 2019 classification, incomplete cord syndromes, acute management with MAP targets, early decompression evidence from STASCIS/SCI-POEM, autonomic dysreflexia), cervical spondylotic myelopathy (most common non-traumatic myelopathy, mJOA grading, surgical approaches, CSM vs ALS differentiation), OPLL, spinal tumors by compartment (extradural metastases/MESCC emergency, intradural-extramedullary meningioma/schwannoma, intramedullary ependymoma/astrocytoma), inflammatory myelopathies (transverse myelitis differential, MS vs NMOSD vs MOGAD myelitis patterns, sarcoid myelopathy, infectious myelitis including HTLV-1/VZV/schistosomiasis), vascular myelopathies (spinal cord infarction, spinal dural AVF), metabolic myelopathies (B12/SCD, copper deficiency, nitrous oxide, radiation myelopathy), hereditary spastic paraplegia, cauda equina vs conus medullaris syndromes, syringomyelia, Chiari malformations, and tethered cord syndrome.

11.1 Spinal Cord Injury — ASIA Classification & Acute Management

11.1.1 Neuroanatomical Review

The spinal cord extends from the foramen magnum to the conus medullaris (typically L1–L2 vertebral level in adults). Understanding the cross-sectional anatomy of the cord is essential for localizing myelopathy:

Tract	Location	Function	Deficit When Damaged
Corticospinal (lateral)	Lateral column (decussates at medullary pyramids)	Voluntary motor (UMN)	Ipsilateral UMN weakness, spasticity, hyperreflexia, Babinski
Dorsal columns (fasciculus gracilis/cuneatus)	Posterior column (decussates at medulla)	Fine touch, vibration, proprioception	Ipsilateral loss of vibration, proprioception, sensory ataxia
Spinothalamic (lateral)	Anterolateral (decussates 1–2 levels above entry in anterior white commissure)	Pain, temperature, crude touch	Contralateral loss of pain/temperature (1–2 levels below lesion)
Anterior horn cells	Ventral gray matter	LMN to skeletal muscles	Ipsilateral LMN signs at lesion level: weakness, atrophy, fasciculations, hyporeflexia
Intermediolateral cell column	Lateral horn (T1–L2)	Sympathetic preganglionic neurons	Autonomic dysfunction (orthostatic hypotension, bladder/bowel, anhidrosis below level)
Sacral parasympathetics	S2–S4 (Onuf’s nucleus)	Bladder detrusor, rectal, sexual function	Neurogenic bladder/bowel, erectile dysfunction

11.1.2 ASIA/ISNCSCI Classification

ASIA Impairment Scale (AIS) — International Standards 2019

AIS Grade	Description	Key Definition
A — Complete	No motor or sensory function in sacral segments S4–S5	No voluntary anal contraction (VAC), no deep anal pressure (DAP), no light touch/pin prick at S4–S5
B — Sensory Incomplete	Sensory but no motor function preserved below NLI including S4–S5	DAP or S4–S5 sensation present, NO motor below NLI (or motor present only in zone of partial preservation)
C — Motor Incomplete	Motor function preserved below NLI; >50% of key muscles below NLI are < Grade 3	Motor incomplete but mostly weak (cannot overcome gravity)
D — Motor Incomplete	Motor function preserved below NLI; ≥50% of key muscles below NLI are ≥ Grade 3	Motor incomplete with functional strength (overcomes gravity)
E — Normal	Motor and sensory normal in all segments	May have abnormal reflexes (hyperreflexia); recovered SCI

Key terminology: NLI (Neurological Level of Injury) = most caudal segment with normal motor (Grade 5) AND sensory function bilaterally. ZPP (Zone of Partial Preservation) = applies only to AIS A; segments below NLI with some preserved function.

11.1.3 Spinal Cord Syndromes

Incomplete Spinal Cord Syndromes

Syndrome	Lesion Location	Etiology	Clinical Features	Prognosis
Central Cord Syndrome	Central gray matter + medial portions of lateral columns	Most common incomplete SCI. Hyperextension injury in elderly with pre-existing cervical spondylosis. Syringomyelia. Intramedullary tumor	Arms >> legs weakness (lamination: cervical fibers medial in corticospinal tract). “Cape-like” dissociated sensory loss (pain/temp) if syrinx. Bladder dysfunction	Best recovery among incomplete syndromes. Legs recover first, then bladder, then arms/hands (hands recover last and least)
Brown-Séquard (Hemicord)	Lateral half of cord (unilateral)	Penetrating trauma (knife, gunshot), lateral disc herniation, lateral tumor, MS plaque	Ipsilateral: UMN weakness, dorsal column loss (vibration, proprioception). Contralateral: spinothalamic loss (pain/temp, 1–2 levels below)	Best functional prognosis. >90% regain ambulatory capacity
Anterior Cord Syndrome	Anterior 2/3 of cord (anterior spinal artery territory)	Anterior spinal artery occlusion (aortic surgery, dissection, hypotension), disc herniation, flexion-compression fracture	Motor paralysis (corticospinal) + spinothalamic loss (pain/temp) below level. PRESERVED dorsal columns (vibration, proprioception, light touch)	Worst prognosis among incomplete syndromes. Only 10–20% recover functional motor
Posterior Cord Syndrome	Posterior columns (rare in isolation)	B12 deficiency (SCD), tabes dorsalis, Friedreich ataxia, MS, compressive	Loss of proprioception, vibration, fine touch. Sensory ataxia. Romberg positive. Preserved motor, pain/temp	Depends on etiology; B12 replacement may improve if caught early

11.1.4 Acute SCI Management

Acute Traumatic SCI Management Protocol

Domain	Intervention	Details & Evidence
Spinal immobilization	Cervical collar + log-roll; spinal board	Until cleared by imaging. CT cervical spine (not X-ray) is standard. MRI for suspected cord/ligamentous injury
Hemodynamic target	MAP 85–90 mmHg × 7 days	Prevents secondary cord ischemia. Vasopressors (norepinephrine preferred) for neurogenic shock. AO Spine Guidelines 2017: strong recommendation for MAP augmentation
Neurogenic shock	Hypotension + bradycardia (distinguishes from hemorrhagic shock which has tachycardia)	Loss of sympathetic tone below injury (especially T6 and above). Warm/dry skin (vasodilation). Treat: IV fluids + vasopressors (norepinephrine, phenylephrine). Atropine for symptomatic bradycardia
Respiratory	C3–C5 injury: phrenic nerve at risk	Monitor FVC q4h (intubate if FVC <15 mL/kg or declining). High cervical (C1–C3): usually requires ventilator. C3–C5: variable; may decompensate days later as edema ascends. Diaphragmatic pacing for chronic high cervical SCI
Surgical decompression	<24 hours preferred	STASCIS (Fehlings et al. PLoS One 2012): early decompression (<24h) vs late (>24h): ≥2 AIS grade improvement in 19.8% vs 8.8% (p=0.01). SCI-POEM (Fehlings et al. Lancet Neurol 2021): ultra-early (<12h) may be even better. AO Spine 2017: strong recommendation for early decompression in incomplete SCI
Methylprednisolone	NOT standard of care	NASCIS-2/3 protocol (30 mg/kg bolus → 5.4 mg/kg/h × 23–48h within 8h of injury): AAN/CNS/AO Spine recommend AGAINST routine use. Marginal benefit does not outweigh risk (infection, GI bleed, hyperglycemia, AVN). May be considered in shared decision-making within 8h for acute SCI. Never give >8h post-injury
VTE prophylaxis	LMWH within 72h (once hemostasis ensured)	SCI has highest DVT/PE risk of any medical condition (~40–80% without prophylaxis). LMWH + mechanical prophylaxis. Duration: 8–12 weeks. IVC filter only if anticoagulation contraindicated

11.1.5 Autonomic Dysreflexia

Autonomic Dysreflexia (AD) — Medical Emergency in Chronic SCI

Feature	Details
Who	SCI at T6 or above (loss of splanchnic sympathetic outflow regulation). Onset usually ≥3–6 weeks post-injury (once spinal shock resolves). Lifetime risk: up to 90% in high cervical SCI
Mechanism	Noxious stimulus below injury → massive uninhibited sympathetic discharge below lesion → severe vasoconstriction → hypertension. Baroreceptor-mediated parasympathetic response ABOVE lesion (bradycardia, flushing, sweating above level) but cannot descend past injury to counteract
Triggers	Bladder distension (most common: 75–85%), bowel impaction (second most common), pressure ulcers, ingrown toenail, tight clothing, UTI, fracture, DVT, sexual stimulation, labor in pregnant SCI patients
Symptoms	Severe headache (pounding), hypertension (>20–40 mmHg above baseline; SBP can exceed 250–300), bradycardia (reflex), sweating/flushing above level, piloerection, nasal congestion, blurred vision, anxiety
Management	1. Sit patient upright (orthostatic drop). 2. Identify and remove trigger: straight catheterize bladder (most common cause); check for fecal impaction (use lidocaine jelly). 3. Loosen clothing. 4. If SBP remains >150 after trigger removal: nifedipine 10 mg bite-and-swallow or nitroglycerine paste 2% 1 inch topically. 5. IV nitroprusside or labetalol for refractory cases
Prevention	Scheduled CIC (clean intermittent catheterization), regular bowel program, skin checks, patient/caregiver education. Medical alert card

Clinical Pearl — Spinal Shock vs. Neurogenic Shock: These are commonly confused. Spinal shock = transient loss of ALL spinal cord function (including reflexes) below the level of injury. NOT a hemodynamic state. Duration: days to weeks. Resolution marked by return of bulbocavernosus reflex (first reflex to return). Neurogenic shock = hemodynamic state: hypotension + bradycardia from loss of sympathetic tone. A cardiovascular emergency requiring vasopressors. Both can coexist in acute SCI but are distinct entities.

Q: A 72-year-old man with known cervical spondylosis falls, hitting his forehead. He presents with weakness more severe in the upper extremities than lower, bilateral hand weakness, and urinary retention. Lower extremity strength is 4/5 throughout. MRI shows C3–C6 spondylosis with central cord T2 hyperintensity. What is the syndrome, AIS grade, and management?

Syndrome: Central cord syndrome — the most common incomplete SCI. Classic mechanism: hyperextension injury in elderly with pre-existing cervical spondylosis.
AIS Grade: AIS D (motor incomplete; ≥50% of key muscles below NLI have grade ≥3, as LE strength is 4/5).
Key features: Upper extremity weakness > lower (arms affected more than legs), hand weakness (fine motor), bladder dysfunction (urinary retention).
Management:
1. Immobilization (cervical collar)
2. MAP target 85–90 mmHg × 7 days (prevent secondary ischemia)
3. MRI confirms cord edema/signal change + multi-level spondylotic compression
4. Surgical decompression within 24 hours (STASCIS evidence for early decompression benefit, especially in incomplete SCI). Approach: posterior laminoplasty or laminectomy for multi-level compression; anterior approach if single-level prominent disc
5. VTE prophylaxis: LMWH + SCDs once hemostasis stable
6. Bladder management: Foley catheter acutely; transition to CIC
7. Methylprednisolone: NOT recommended (AAN/AO Spine guidelines)
8. Prognosis: Central cord has the best recovery among incomplete syndromes. Legs recover first, then bladder, then proximal arms; hands recover last and least completely. Most AIS D patients regain ambulatory function

11.2 Cervical Spondylotic Myelopathy & Compressive Spinal Cord Disorders

11.2.1 Cervical Spondylotic Myelopathy (CSM)

CSM is the most common cause of non-traumatic myelopathy in adults over age 55 in developed countries. It results from degenerative changes causing progressive spinal cord compression. Understanding its pathophysiology, natural history, and surgical indications is essential for neurologists.

Cervical Spondylotic Myelopathy — Comprehensive Overview

Feature	Details
Pathophysiology	Degenerative cascade: disc desiccation → disc bulging/herniation → osteophyte formation (uncovertebral, facet joints) → ligamentum flavum hypertrophy/buckling → canal narrowing. Static factors (structural narrowing) + dynamic factors (repetitive flexion/extension microtrauma). Congenital canal stenosis (AP diameter <13 mm) predisposes. Ischemia from anterior spinal artery compression contributes. Pathology: demyelination of lateral columns > posterior columns; anterior horn cell loss at compression level
Most common levels	C5–C6 > C6–C7 > C4–C5 (greatest mobility = greatest degeneration). Multi-level disease common in elderly
Clinical features	Insidious onset, stepwise progression. (1) Gait difficulty (spastic ataxic gait) — often earliest symptom. (2) Hand clumsiness, loss of fine motor (myelopathy hand: finger escape sign, grip-release <20 cycles in 10 sec). (3) Neck stiffness/pain (not always present). (4) UMN signs in legs: spasticity, hyperreflexia, Babinski. (5) LMN signs at level of compression (C5–C6: biceps/brachioradialis weakness, absent reflex). (6) Mixed UMN/LMN in arms. (7) Bladder dysfunction (late). (8) Lhermitte sign (electric shock with neck flexion — not specific to MS)
Natural history	Typically progressive. 75% stepwise deterioration, 20% slow steady decline, 5% rapid. Spontaneous improvement rare. Worse prognosis: older age, longer symptom duration, greater cord compression, T2 signal change (myelomalacia)

Diagnosis & Imaging

Investigation	Findings	Clinical Significance
MRI cervical spine (gold standard)	Disc bulging/herniation, osteophytes, cord compression. T2 hyperintensity in cord (myelopathy signal). T1 hypointensity (myelomalacia — worse prognosis). Cord cross-sectional area <60 mm² correlates with myelopathy	T2 signal = edema/gliosis (may be reversible). T1 hypointensity = irreversible necrosis/cavitation. Snake-eye appearance on axial T2 (bilateral anterior horn signal) = poor surgical prognosis
CT myelography	Superior bony detail. Gold standard if MRI contraindicated. Better for OPLL characterization	Shows extent of cord compression, canal diameter
X-ray (flexion/extension)	Spondylosis, disc space narrowing, osteophytes, alignment. Dynamic instability (>3.5 mm translation)	Screening; insufficient alone for myelopathy assessment
Electrophysiology	SSEPs: prolonged central conduction time. EMG: may show C5/C6 radiculopathy (denervation at compression level). MEPs: corticospinal tract dysfunction	Helps differentiate from peripheral neuropathy, ALS. Intraoperative monitoring during surgery

CSM Severity Grading

Modified Japanese Orthopaedic Association (mJOA) Score

Severity	mJOA Score	Clinical Implication
Mild	15–17	Can be observed with serial exams q3–6 months + MRI. Surgery if deterioration
Moderate	12–14	Surgery recommended (AO Spine CSM guidelines 2017)
Severe	≤11	Urgent surgery recommended. Worse baseline = less recovery potential

Maximum score = 18 (normal). Assesses motor function upper/lower extremities, sensory, and bladder. Most widely used outcome measure in CSM trials.

Surgical Management of CSM

Approach	Indication	Procedure	Key Considerations
Anterior	1–2 level disease, anterior compression (disc/osteophyte), kyphotic alignment	ACDF (anterior cervical discectomy & fusion): 1–2 levels. ACCF (anterior cervical corpectomy & fusion): 1–3 levels, for retrovertebral disease/OPLL	Direct decompression. Risk: dysphagia (most common), recurrent laryngeal nerve palsy, esophageal injury, adjacent segment disease (2.9%/year). C5 palsy (4–8%): new deltoid/biceps weakness post-op, usually recovers
Posterior	Multi-level (≥3) disease, posterior compression (ligamentum flavum), preserved/lordotic alignment	Laminoplasty (open-door or French-door): preserves motion, best for 3–4 levels. Laminectomy + fusion: for ≥3 levels, instability, kyphosis correction needed	Indirect decompression (cord drifts posteriorly). Requires lordotic alignment (kyphosis = anterior compression persists). C5 palsy risk similar. Laminoplasty: preserves motion but axial neck pain common
Combined (360°)	Severe multi-level compression with kyphosis, instability, OPLL	Anterior decompression + posterior fixation/fusion	Higher morbidity but best for complex deformity

Clinical Pearl — CSM vs. ALS: This is one of the most important differential diagnoses in neurology. Both present with upper AND lower motor neuron signs. Key differentiators: (1) CSM: sensory findings (absent in ALS); (2) CSM: bowel/bladder involvement (rare in ALS until late); (3) ALS: widespread fasciculations beyond one myotomal distribution, bulbar signs (tongue fasciculations, dysarthria), split-hand sign (APB > ADM weakness), EMG showing widespread active denervation across multiple levels. (4) CSM: MRI shows cord compression with signal change; (5) CSM: UMN/LMN signs correspond to structural compression level. Trap: Patients can have both (CSM + ALS). If a patient with confirmed CSM continues to deteriorate after adequate decompression, reconsider ALS.

11.2.2 Ossification of the Posterior Longitudinal Ligament (OPLL)

Feature	Details
Epidemiology	Prevalence: East Asian populations (Japan 1.9–4.3%, Korea, China) >> Caucasian (0.1–1.7%). Male > female (2:1). Age 50–70. Associated with DM, metabolic syndrome, DISH (diffuse idiopathic skeletal hyperostosis)
Classification (Tsuyama)	Continuous (most common), segmental, mixed, circumscribed (localized). CT classification: flat, mushroom-shaped (hill type), nodular
Genetics	Polygenic: BMP signaling pathway genes (BMP2, BMP4), COL6A1, COL11A2, TGF-β pathway. Genome-wide association studies identify multiple loci
Clinical	Progressive myelopathy identical to CSM. Higher risk of SCI from minor trauma (already stenotic canal). Occupying ratio >60% = high myelopathy risk. Dynamic factors contribute less (often fused segments)
Imaging	CT: gold standard for OPLL morphology and occupying ratio. MRI: cord compression, myelopathy signal. Plain film: dense ossification posterior to vertebral bodies
Treatment	Posterior approach (laminoplasty) preferred for multi-level, occupying ratio <60%. Anterior approach (corpectomy) for 1–2 level, high occupying ratio, kyphosis. Anterior floating method: OPLL left in situ, dura separates. Risk of dural ossification (OPLL adherent to dura): CSF leak 10–30% with anterior approach. K-line concept: if OPLL does not cross line from C2 to C7 on lateral view, posterior approach effective

11.2.3 Other Compressive Myelopathies

Condition	Key Features	Management
Thoracic disc herniation	Rare (1% of all disc herniations). Insidious myelopathy. T8–T12 most common. Often calcified. Diagnosis frequently delayed. MRI thoracic spine essential when cervical MRI doesn’t explain myelopathy	Anterior or lateral approach (transthoracic, costotransversectomy). Avoid posterior laminectomy (cord cannot tolerate posterior retraction at thoracic level)
Thoracic spinal stenosis	Less common than cervical. OLF (ossification of ligamentum flavum) more common in East Asian populations. Often combined with thoracic OPLL	Posterior decompression (laminectomy + fusion). OLF: en bloc resection avoiding dural tear
Lumbar spinal stenosis	Neurogenic (pseudo) claudication: bilateral leg pain/weakness with walking, relieved by sitting/bending forward (increases canal diameter). Distinguished from vascular claudication (which improves with standing still). Central stenosis: cauda equina compression. Lateral recess/foraminal: radiculopathy	Conservative: physical therapy, epidural steroid injections. Surgical: decompressive laminectomy ± fusion (SPORT trial: surgery superior to non-operative treatment at 2 and 4 years for moderate-severe stenosis)
Atlanto-axial subluxation	Rheumatoid arthritis (most common cause): pannus erodes transverse ligament → anterior subluxation of C1 on C2 (ADI >3 mm in adults). Also: Down syndrome, os odontoideum, Morquio syndrome. Myelopathy from cervicomedullary compression	C1–C2 posterior fusion (Magerl transarticular screws, Harms C1 lateral mass/C2 pedicle screws). Screen RA patients before intubation (flexion/extension views or MRI)
Paget disease of bone	Vertebral enlargement, stenosis, basilar invagination. Pagetic steal (hypervascularity diverts blood from cord). Rarely sarcomatous degeneration	Bisphosphonates (zoledronic acid). Decompressive surgery for myelopathy

11.2.4 Spinal Tumors

Spinal tumors are classified by anatomical compartment, which determines the differential diagnosis, clinical presentation, and surgical approach:

Spinal Tumor Classification by Compartment

Compartment	Frequency	Common Tumors	Clinical Features	MRI Characteristics
Extradural	55–60% (most common)	Metastases (most common overall spinal tumor): lung, breast, prostate, kidney, myeloma. Primary: chordoma (sacrum/clivus), osteosarcoma, Ewing sarcoma, giant cell tumor	Pain (often nocturnal, progressive, worse supine). Rapid progression. Pathological fracture. Epidural spinal cord compression (ESCC) = oncologic emergency	Vertebral body destruction, epidural soft tissue mass, cord compression. T1 low signal replacing marrow fat. Enhancement heterogeneous
Intradural-Extramedullary	30–35%	Meningioma (F > M, thoracic predilection, en plaque or globular, dural tail sign). Schwannoma/Neurofibroma (nerve sheath tumors; schwannoma: S100+, encapsulated, Antoni A/B; dumbbell shape through foramen). Myxopapillary ependymoma (filum terminale). Drop metastases (medulloblastoma, ependymoma, PCNSL, leptomeningeal carcinomatosis)	Slowly progressive myelopathy + radiculopathy. Well-circumscribed, displaces cord. Nerve sheath tumors: radicular pain often first. Meningioma: middle-aged women, thoracic level	Well-defined, homogeneous enhancement. Cord displaced but not invaded. CSF cap sign (meniscus of CSF around tumor). Dumbbell shape (schwannoma extending through foramen)
Intramedullary	5–10%	Ependymoma (most common IM tumor in adults; central canal origin; well-circumscribed; GTR often possible). Astrocytoma (most common IM tumor in children; infiltrative; GTR often not possible). Hemangioblastoma (VHL association; enhancing nodule + cyst + syrinx). Metastases (rare: lung, breast)	Central cord syndrome pattern. Diffuse poorly localizable pain. Suspended dissociated sensory loss (cape-like). Late: UMN signs below, LMN at level. Syringomyelia frequently associated (tumor-related syrinx)	Cord expansion + T2 hyperintensity. Ependymoma: central, well-marginated, “cap sign” (hemosiderin rim from prior hemorrhage). Astrocytoma: eccentric, ill-defined, patchy enhancement. Hemangioblastoma: brightly enhancing nodule

Metastatic Epidural Spinal Cord Compression (MESCC)

MESCC — Oncologic Emergency

Aspect	Details
Epidemiology	5–10% of cancer patients. Most common: lung > breast > prostate > renal > myeloma. Thoracic spine most affected (60–70%) > lumbar (20–25%) > cervical (10–15%)
Presentation	Back pain (first symptom in >95%): progressive, worse at night, worse supine, may be radicular (thoracic band-like pain). Motor weakness (60–85%): rapidly progressive. Sensory level (50–70%). Autonomic/bladder dysfunction (40–60%): late, poor prognostic sign. Pre-ambulatory status at treatment = strongest predictor of outcome
ESCC Scale (Bilsky)	MRI-based grading of epidural disease: 0 (bone only) → 1a (epidural fat impingement) → 1b (thecal sac abutment) → 1c (cord abutment, no compression) → 2 (cord compression, CSF visible) → 3 (cord compression, no CSF visible). Grade 2–3: high-grade ESCC requiring urgent intervention
Acute management	1. Dexamethasone: high-dose 10–16 mg IV bolus then 4–8 mg q6h (NICE guidelines). Some use 96 mg bolus for motor deficits (Sorensen et al. 1994). 2. MRI whole spine with Gd (10–15% have additional asymptomatic levels). 3. Emergency referral: neurosurgery/spine surgery + radiation oncology
Definitive treatment	Surgery + post-op RT vs. RT alone: Patchell et al. Lancet 2005: direct decompressive surgery + RT significantly superior to RT alone for maintaining/regaining ambulation (84% vs 57%, p=0.001), continent (1), reduced opioid use. Inclusion: single site, no radiosensitive histology, reasonable prognosis. RT alone: multiple levels, radiosensitive tumors (lymphoma, myeloma, SCLC, seminoma), non-surgical candidates, poor prognosis (<3 months). SBRT/SRS: increasingly used for re-irradiation and oligometastatic disease (16–24 Gy single fraction or 27 Gy/3 fractions)
Prognostic factors (Tokuhashi, Tomita scores)	Consider: primary tumor type, visceral/bone metastases, performance status, neurological deficit, life expectancy. Radiosensitive histologies (lymphoma, myeloma, breast, prostate) have better outcomes. Ambulatory status at treatment initiation is the single most important predictor of post-treatment ambulation

Clinical Pearl — Urgency in MESCC: This is truly a neurological emergency where hours matter. A patient who is ambulatory at the time of treatment has ~80% chance of remaining ambulatory. A patient who is paraplegic at treatment has only ~10–20% chance of regaining ambulation. The window of opportunity is narrow: motor deficits progressing over hours to days. Key principle: MRI the ENTIRE spine urgently (multi-level disease in 10–38%), start high-dose dexamethasone immediately, and arrange surgery + RT within 24–48 hours for high-grade ESCC in appropriate candidates. Do not wait for a biopsy if the diagnosis of metastatic disease is established. Delays for “further workup” are the most common preventable cause of poor outcome.

Q: A 62-year-old man presents with 3 months of progressive difficulty walking, hand clumsiness (cannot button his shirt), and neck stiffness. Examination shows spastic gait, hyperreflexia in all four limbs, Babinski bilateral, inverted radial reflex (finger flexion when brachioradialis tested), and reduced vibration in the feet. No fasciculations. MRI shows multi-level (C3–C7) spondylotic stenosis with T2 cord signal at C4–C5. What is the diagnosis, mJOA severity, and surgical approach?

Diagnosis: Cervical spondylotic myelopathy (CSM) — the most common non-traumatic myelopathy. The clinical triad of gait difficulty + hand clumsiness + UMN signs with structural cord compression on MRI is classic.
Key examination findings: (1) Spastic gait (corticospinal tract involvement). (2) Hand clumsiness (myelopathy hand — corticospinal + dorsal column). (3) Inverted radial reflex (pathognomonic for C5–C6 myelopathy): LMN at C5–C6 abolishes brachioradialis reflex, but UMN below allows spread to C8 finger flexors. (4) Hyperreflexia + Babinski (UMN). (5) Vibration loss (dorsal column involvement). (6) Absence of fasciculations helps against ALS.
mJOA Severity: Likely moderate (12–14) based on impaired hand function, gait difficulty, but still ambulatory and independent.
Surgical approach: Multi-level (C3–C7) = posterior approach preferred. Options: (1) Laminoplasty (if lordotic alignment, no instability — preserves motion); (2) Laminectomy + lateral mass fusion (if kyphosis or instability). Anterior approach (ACCF or multi-level ACDF) less favorable for 5-level disease (higher complication rate). Intraoperative neuromonitoring (SSEPs + MEPs) essential. Post-op: collar for 6–12 weeks if fusion, immediate mobilization. Expected improvement: 50–70% show mJOA improvement with surgery, though complete recovery is uncommon.

11.3 Inflammatory & Infectious Myelopathies

11.3.1 Transverse Myelitis (TM) — Overview & Differential Diagnosis

Transverse myelitis is an inflammatory disorder of the spinal cord characterized by acute/subacute bilateral (though often asymmetric) motor, sensory, and autonomic dysfunction. The Proposed Diagnostic Criteria for TM (Transverse Myelitis Consortium Working Group 2002) require: (1) bilateral sensory/motor/autonomic dysfunction attributable to spinal cord; (2) clear sensory level; (3) evidence of inflammation (CSF pleocytosis, elevated IgG index, or Gd enhancement on MRI); (4) progression to nadir between 4 hours and 21 days; (5) exclusion of compressive etiology.

Transverse Myelitis — Etiologic Classification

Category	Specific Diagnoses	Key Distinguishing Features
Demyelinating / Autoimmune	MS, NMOSD, MOGAD, Sarcoidosis, SLE, Sjögren, Behçet, ADEM	MRI pattern, antibodies, systemic features differentiate
Idiopathic TM	Diagnosis of exclusion after comprehensive workup negative	~15–30% of acute TM cases. Monophasic course expected. Partial or complete myelitis. May represent forme fruste of antibody-negative autoimmune myelitis
Infectious	Viral (VZV, HSV-2, EBV, CMV, HTLV-1, HIV, enterovirus, WNV), bacterial (TB, syphilis, Lyme, Brucella), parasitic (schistosomiasis, Toxoplasma, cysticercosis), fungal (Aspergillus)	Immunosuppressed patients, endemic exposure, CSF cultures/PCR. Acute flaccid myelitis (enterovirus D68, polio): anterior horn
Para-/Post-infectious	Post-viral TM (1–4 weeks after infection), post-vaccination (rare)	Molecular mimicry mechanism. Often monophasic. ADEM if multifocal brain + cord involvement
Paraneoplastic	Anti-CRMP5/CV2, anti-amphiphysin, anti-GFAP (meningoencephalomyelitis)	Cancer screening essential. Longitudinally extensive. Often poor prognosis

Initial Workup for Acute Myelopathy

Investigation	Purpose
MRI spine with Gd (entire spine if possible)	Exclude compression (urgent). Characterize lesion: length (<3 vs ≥3 vertebral segments), location (central, dorsal, anterior, peripheral), enhancement pattern, expansion
MRI brain with Gd	If brain lesions present: MS (periventricular, Dawson fingers), NMOSD (area postrema, periaqueductal, diencephalic), MOGAD (fluffy, cortical), ADEM (large poorly demarcated), sarcoid (leptomeningeal, nodular)
CSF analysis	Cell count (pleocytosis: lymphocytic = autoimmune; neutrophilic early = NMOSD, infection; eosinophilic = parasitic, sarcoid). Protein, glucose. Oligoclonal bands (MS). IgG index. Cytology. Cultures, PCR panel (HSV, VZV, EBV, CMV, enterovirus). VDRL. AFB/TB culture
Serum antibodies	AQP4-IgG (NMOSD — cell-based assay preferred, sensitivity ~77%, specificity >99%). MOG-IgG (MOGAD — cell-based assay only; live CBA preferred). ANA, dsDNA, SSA/SSB, ACE, ANCA
Additional	B12, copper, zinc, HIV, HTLV-1/2, RPR, Lyme serologies, chest CT (sarcoid), CT C/A/P (malignancy if paraneoplastic suspected). Visual evoked potentials (subclinical optic neuritis = MS/NMOSD)

11.3.2 MS-Related Myelitis

Feature	Details
MRI characteristics	Short-segment TM (<3 vertebral segments), typically cervical. Peripheral/dorsolateral location (posterior columns, lateral corticospinal tract). Partial cross-section (usually <50% cord area). No or mild cord swelling. Multiple lesions over time. T1 hypointensity (chronic “black holes”). May show ring enhancement in active lesions
Clinical	Asymmetric, partial myelitis. Lhermitte sign (40–50% of MS myelitis). Sensory > motor at presentation. Uhthoff phenomenon (worsening with heat). Typically: unilateral or asymmetric leg weakness, hemisensory level, paresthesias. Brown-Séquard-like presentation more common than complete TM
CSF	Oligoclonal bands positive in >95% of MS. Mild pleocytosis (usually <50 cells). Normal or mildly elevated protein. IgG index elevated
Prognosis	Generally good recovery from individual attacks. Risk of second attack (and MS diagnosis) depends on brain MRI lesions and OCBs
Treatment	Acute: IV methylprednisolone 1 g/day × 3–5 days. PLEX for steroid-refractory attacks. DMT initiation for MS prevention of further attacks (see Section 4)

11.3.3 NMOSD Myelitis

Neuromyelitis Optica Spectrum Disorder (NMOSD) — Myelitis Features

Feature	Details
Pathogenesis	AQP4-IgG (aquaporin-4 antibody) binds astrocyte foot processes → complement-dependent cytotoxicity → astrocytopathy → secondary demyelination + necrosis. AQP4 concentrated at perivascular end-feet, subpial, subependymal regions
MRI characteristics	Longitudinally extensive TM (LETM): ≥3 contiguous vertebral segments (hallmark, sensitivity ~75%). Centrally located (gray matter > white matter). Bright spotty lesions on T2 (cavitation/necrosis). Cord swelling (often marked). Sagittal: “pencil-thin” or “rail-track” enhancement. Ring enhancement may mimic tumor. In chronic phase: cord atrophy (“pencil-thin cord”). Conus involvement more common than MS
Clinical severity	Severe attacks: complete or near-complete TM with dense paraplegia, sensory level, urinary retention. Bilateral involvement typical. Painful spasms (tonic spasms — characteristic of NMOSD). Nausea/vomiting/hiccups (area postrema syndrome often accompanies or precedes myelitis). Each attack causes more disability than MS (but inter-attack period stable)
CSF	Pleocytosis often >50 cells (can be neutrophil-predominant early — distinguishes from MS). Elevated protein. OCBs absent in ~80% (vs >95% positive in MS). GFAP elevated (astrocyte damage marker)
Treatment — Acute	IV methylprednisolone 1 g × 5 days. Early PLEX (plasmapheresis) if no response in 3–5 days — or consider upfront in severe attacks (5–7 exchanges). PLEX effective because AQP4-IgG is directly pathogenic. Do NOT use fingolimod, natalizumab, or other MS DMTs (can worsen NMOSD)
Treatment — Prevention	Monoclonal antibodies (FDA-approved): (1) Eculizumab (anti-C5 complement; PREVENT trial 2019: ARR 0.02 vs 0.35; NNT=3). (2) Inebilizumab (anti-CD19 B-cell depleting; N-MOmentum 2019: 73% reduction in attacks). (3) Satralizumab (anti-IL-6R; SAkuraSky 2019, SAkuraStar 2020: 55–74% reduction). Off-label: rituximab (anti-CD20), azathioprine, mycophenolate mofetil

11.3.4 MOGAD Myelitis

Feature	Details
Antibody	MOG-IgG (myelin oligodendrocyte glycoprotein). Must use cell-based assay (CBA) — ELISA unreliable (high false positive). Live CBA > fixed CBA. Re-test if initially negative and clinical suspicion high
Demographics	Bimodal: children (ADEM-like presentation) and young adults. Male = female (unlike NMOSD female predominance). Any ethnicity (NMOSD: non-white predominance)
Myelitis pattern	LETM (like NMOSD) but often involves conus/lower thoracic cord (distinctive). Gray matter-predominant (central/H-shaped T2 signal). Can be short-segment. Less cavitary necrosis than NMOSD (less destructive). Cord swelling present. Enhancement: patchy, sometimes leptomeningeal
Key clinical differences from NMOSD	(1) Better recovery per attack (less necrotic). (2) Optic neuritis often bilateral with optic disc edema (papillitis). (3) ADEM phenotype in children. (4) Relapsing course in ~50% (especially if MOG-IgG persistently positive). (5) Conus/cauda equina involvement more common. (6) Seizures and cortical encephalitis phenotype
CSF	Pleocytosis (can be >100 cells, neutrophils possible). OCBs usually absent or transient. Elevated protein
Treatment	Acute: IV methylprednisolone 1 g × 5 days + prolonged oral taper (6–12 months — MOGAD flares on rapid steroid taper). IVIg for steroid-refractory or as maintenance. PLEX for severe. Maintenance: IVIg (monthly), rituximab, azathioprine, mycophenolate. No FDA-approved therapy yet. Proposed MOGAD diagnostic criteria (Banwell et al. Lancet Neurol 2023): core clinical + MOG-IgG positive (CBA) + supportive features

Clinical Pearl — NMOSD vs MOGAD vs MS Myelitis at a Glance: (1) MS: short-segment (<3 VB), peripheral/dorsolateral, partial TM, OCB+, chronic lesions/atrophy. (2) NMOSD: LETM (≥3 VB), central, severe/necrotic, AQP4+, OCB−, bright spotty lesions, cord atrophy. (3) MOGAD: LETM or short, central/H-shaped, conus predilection, less necrotic, good recovery, MOG+, OCB−. A patient with LETM who is AQP4-negative should ALWAYS be tested for MOG-IgG. If both negative, consider sarcoid, paraneoplastic, and idiopathic TM.

11.3.5 Sarcoid Myelopathy

Feature	Details
Epidemiology	Neurosarcoidosis in ~5–10% of sarcoidosis patients. Myelopathy in ~10% of neurosarcoidosis (overall rare but important). Young to middle-aged adults. African American predominance
MRI pattern	Longitudinally extensive (often >3 VB, can span entire cord). Dorsal subpial enhancement (“trident sign” on axial: dorsal column + lateral column enhancement). Central canal enhancement. Persistent enhancement despite treatment (unlike MS). Leptomeningeal enhancement
Diagnosis	Tissue biopsy gold standard (non-caseating granulomas). Serum ACE (sensitivity ~60%, specificity poor). Chest CT (bilateral hilar lymphadenopathy in 50–90%). CSF: pleocytosis, elevated protein, low glucose (25%), elevated ACE (sensitivity ~55%). FDG-PET: identifies occult systemic disease for biopsy targets. Conjunctival biopsy (positive in 30–40% even without visible nodules)
Treatment	First-line: IV methylprednisolone 1 g × 5 days → high-dose oral prednisone (1 mg/kg) with very slow taper over 6–12+ months. Steroid-sparing: mycophenolate mofetil (preferred), methotrexate, azathioprine. Refractory: infliximab (anti-TNFα; strong evidence in neurosarcoidosis, especially meningeal and myelopathic disease). Duration: prolonged (years to indefinite)

11.3.6 Infectious Myelopathies

Infectious Myelitis — Key Pathogens

Pathogen	Myelopathy Type	Key Features	Treatment
HTLV-1 (HAM/TSP)	Slowly progressive spastic paraparesis	Endemic: Japan, Caribbean, sub-Saharan Africa, South America. Sexual/blood/breast milk transmission. Insidious onset over months to years. Thoracic cord predilection. UMN signs in legs, bladder dysfunction, mild sensory involvement. CSF: lymphocytes, HTLV-1 antibodies. MRI: thoracic cord atrophy, sometimes T2 signal	No curative treatment. Corticosteroids may slow progression. Antiretrovirals not effective (not actively replicating). Symptomatic: baclofen for spasticity, oxybutynin for bladder. Interferon-α (some studies)
HIV-associated vacuolar myelopathy	Progressive spastic paraparesis (resembles SCD)	AIDS-defining (CD4 <200). Posterior + lateral column involvement (vacuolar degeneration). Slowly progressive. Often coexists with HIV-associated peripheral neuropathy. MRI: may be normal or show subtle T2 changes	ART (antiretroviral therapy) may stabilize. B12 supplementation (HIV patients often B12 deficient). Symptomatic treatment
VZV myelitis	Acute TM, may follow zoster by 1–3 weeks	Dermatomal zoster (may be absent in immunocompromised). Vasculitis component (small vessel). MRI: short or long segment. CSF: VZV PCR (sensitivity ~50–70%) + VZV IgG/IgM in CSF (intrathecal antibody production more sensitive than PCR)	IV acyclovir 10–15 mg/kg q8h × 10–14 days. Consider adjunctive corticosteroids for vasculitic component. Prognosis: variable, often incomplete recovery
HSV-2 myelitis/radiculitis	Elsberg syndrome (sacral myeloradiculitis)	Lumbosacral radiculitis, urinary retention, saddle anesthesia. Often recurrent (especially in immunosuppressed). Cauda equina/conus. CSF: lymphocytic pleocytosis, HSV-2 PCR positive	IV acyclovir, then oral valacyclovir suppression for recurrence
Schistosomiasis	Conus/cauda equina myelitis	Most common parasitic cause of TM worldwide. S. mansoni and S. haematobium. Endemic: sub-Saharan Africa, Southeast Asia, South America. Ova deposit in epidural/peri-medullary veins (Batson plexus). Conus medullaris predilection. MRI: lower cord/conus expansion with heterogeneous enhancement (“arrowhead sign”). Travel history critical	Praziquantel (kills adult worms) + corticosteroids (anti-inflammatory, reduces granulomatous reaction). Early treatment = better outcome
Tuberculosis	Pott disease (vertebral), epidural abscess, arachnoiditis, intramedullary tuberculoma	Vertebral body collapse (gibbus deformity), epidural abscess with cord compression. Arachnoiditis: CSF block, clumped nerve roots. Intramedullary tuberculoma: ring-enhancing lesion. Endemic areas. CSF: lymphocytic, low glucose, high protein, AFB stain (low sensitivity), GeneXpert	Anti-TB therapy (RIPE) + adjunctive dexamethasone (reduces arachnoiditis). Surgical decompression for abscess/instability. Duration: 12–18 months for CNS TB
Syphilis (tabes dorsalis)	Posterior column degeneration (tertiary syphilis)	Lightning pains (lancinating), sensory ataxia, Argyll Robertson pupils (accommodate but don’t react to light), Romberg positive, areflexia, Charcot joints. CSF: positive VDRL/FTA-ABS	IV penicillin G 18–24 MU/day × 10–14 days (neurosyphilis protocol). Damage often irreversible at this stage

Clinical Pearl — Acute Flaccid Myelitis (AFM): Distinct from typical TM. Presents with acute LMN pattern (flaccid paralysis, areflexia) predominantly in children. Anterior horn cell involvement (poliomyelitis-like). Most commonly associated with enterovirus D68. MRI: longitudinal gray matter T2 lesion, predominantly anterior horns (“owl eyes” or “snake eyes” on axial). CSF: lymphocytic pleocytosis, EV-D68 PCR may be negative in CSF (test nasopharyngeal/stool). Treatment: supportive (IVIg and steroids of uncertain benefit). CDC reportable condition. Poor motor recovery in many cases.

Q: A 28-year-old African American woman presents with rapidly progressive bilateral leg weakness, urinary retention, and a sensory level at T6 over 5 days. MRI shows T2 hyperintensity spanning T2–T8 with patchy enhancement and mild cord swelling. Brain MRI shows subtle leptomeningeal enhancement. CSF: 80 WBC (85% lymphocytes), protein 120 mg/dL, glucose 35 mg/dL (serum 100). AQP4-IgG and MOG-IgG are negative. Chest CT shows bilateral hilar lymphadenopathy. What is the most likely diagnosis and management?

Diagnosis: Neurosarcoidosis with spinal cord involvement (sarcoid myelopathy).
Supporting evidence: (1) LETM (≥3 vertebral segments: T2–T8). (2) Leptomeningeal enhancement on brain MRI (classic for neurosarcoidosis). (3) CSF: marked pleocytosis with low glucose (25% of neurosarcoid has low CSF glucose — uncommon in MS/NMOSD/MOGAD). (4) Bilateral hilar lymphadenopathy on chest CT (cardinal feature of pulmonary sarcoidosis). (5) Young African American woman (demographic at risk). (6) AQP4 and MOG negative, ruling out NMOSD and MOGAD.
Additional workup: (1) Serum ACE (may be elevated, but sensitivity ~60%). (2) Serum calcium, 24-hour urine calcium. (3) Tissue biopsy for non-caseating granulomas (mediastinal lymph node biopsy via EBUS preferred — least invasive with hilar LAD present). (4) CSF ACE. (5) FDG-PET if no accessible biopsy target. (6) Rule out TB (AFB cultures, QuantiFERON — caseating vs non-caseating granulomas).
Management:
1. IV methylprednisolone 1 g/day × 5 days (acute attack)
2. Transition to oral prednisone 1 mg/kg/day with very slow taper over 6–12 months (neurosarcoid relapses on rapid taper)
3. Start steroid-sparing agent early: mycophenolate mofetil 1000 mg BID (preferred) or methotrexate
4. If refractory to steroids + MMF: infliximab (anti-TNF-α) — strong evidence for neurosarcoidosis, especially myelopathy
5. Monitor: serial MRI spine, clinical assessments, ACE levels (imperfect marker)
6. PJP prophylaxis with TMP-SMX if on high-dose steroids + immunosuppression

11.4 Vascular & Metabolic Myelopathies

11.4.1 Spinal Cord Infarction

Spinal cord infarction accounts for only ~1–2% of all strokes but has devastating consequences. The anterior spinal artery territory is preferentially affected due to watershed vulnerability.

Spinal Cord Vascular Anatomy & Infarction Syndromes

Feature	Details
Arterial supply	Anterior spinal artery (ASA): single midline vessel, supplies anterior 2/3 of cord (corticospinal tracts, spinothalamic tracts, anterior horns). Posterior spinal arteries (PSA): paired, supply posterior 1/3 (dorsal columns). Fed by radiculomedullary arteries (6–8 anterior, 10–20 posterior). Artery of Adamkiewicz: largest anterior radiculomedullary artery, enters left side T9–T12 in 75% of cases, supplies lower 2/3 of cord. Watershed zones: T4–T8 (between superior and Adamkiewicz territories) = most vulnerable to ischemia
Anterior spinal artery syndrome	Most common spinal cord infarction pattern. Acute onset (minutes to hours): bilateral motor paralysis (corticospinal) + bilateral spinothalamic loss (pain/temp) below level. PRESERVED dorsal columns (vibration, proprioception, light touch). Bladder dysfunction. Bilateral LMN signs at level of infarction (anterior horn involvement). Flaccid initially (spinal shock) → spastic later
Posterior spinal artery syndrome	Rare in isolation. Bilateral dorsal column loss (proprioception, vibration). Sensory ataxia. Preserved motor and pain/temp. Often partial/asymmetric
Central/sulcal artery infarction	Unilateral anterior cord infarction (Brown-Séquard pattern). Sulcal arteries arise from ASA and alternate left/right supply to each hemicord

Etiology & Risk Factors

Cause	Details
Aortic surgery/procedures	Most common identified cause (up to 30% of cases). Thoracoabdominal aortic aneurysm repair (open > endovascular). Cross-clamping interrupts intercostal/lumbar arteries feeding Adamkiewicz. Risk: 2–10% for open repair. Prevention: CSF drainage, evoked potential monitoring, sequential clamping, permissive hypertension
Aortic pathology	Aortic dissection (especially type B involving descending aorta). Aortic atherosclerosis. Cholesterol embolization (fibrocartilaginous embolism)
Hypotension/systemic	Cardiac arrest, severe hypotension (watershed infarction at T4–T8). Sickle cell disease
Fibrocartilaginous embolism (FCE)	Nucleus pulposus material embolizes to spinal vessels. Typically young patients after minor trauma/Valsalva. Acute myelopathy with no vascular risk factors. MRI: cord infarction adjacent to disc level. Pathological diagnosis (often presumptive clinically)
Vasculitis	SLE, PAN, sarcoid, syphilis, ANCA-associated
Hypercoagulable states	Antiphospholipid syndrome, protein C/S deficiency, polycythemia vera
Venous infarction	Spinal dural AVF (congestive myelopathy), epidural abscess with venous compromise

Diagnosis & Management

Aspect	Details
MRI findings	T2 hyperintensity in ASA territory. DWI restriction (acute phase, like cerebral stroke). “Owl eyes” or “snake eyes” on axial T2 (bilateral anterior horn involvement). “Pencil-like” hyperintensity on sagittal (longitudinally extensive, anterior). Vertebral body infarction may coexist (shared blood supply). MRI may be negative first 24h; repeat if clinically suspicious
Investigations	CTA/MRA aorta (dissection, aneurysm). Echocardiography (cardiac source). Hypercoagulable workup. ESR/CRP/ANA/ANCA (vasculitis). CSF: usually normal or mild protein elevation (no pleocytosis, unlike inflammatory myelopathy)
Treatment	No proven specific treatment (unlike cerebral stroke, no thrombolysis evidence for spinal cord infarction). Supportive: MAP augmentation (avoid hypotension), lumbar CSF drainage (reduces pressure, may improve perfusion — especially post-aortic surgery), anticoagulation if embolic source or dissection. Treat underlying cause. Rehabilitation critical. DVT prophylaxis. Prognosis: ~50% remain non-ambulatory; 30% achieve independent ambulation

11.4.2 Spinal Dural Arteriovenous Fistula (dAVF)

Spinal Dural AVF — The “Great Mimicker” of Myelopathy

Feature	Details
Pathophysiology	Abnormal arteriovenous connection in dural sleeve of nerve root. Arterial pressure transmitted to coronal venous plexus → venous hypertension → reduced arteriolar perfusion pressure → chronic congestive myelopathy (NOT hemorrhagic). The cord is injured by chronic ischemia/edema, not hemorrhage
Epidemiology	Most common spinal vascular malformation (60–80%). Middle-aged to elderly men (5:1 M:F). Acquired lesion. Lower thoracolumbar location (T6–L2 most common)
Classification (Anson & Spetzler)	Type I (dural AVF): most common, slow flow, ventral intradural vein. Type II (glomus AVM): intramedullary, nidus in cord, high-flow. Type III (juvenile/metameric AVM): extensive, intra- + extradural. Type IV (intradural perimedullary AVF): on cord surface
Clinical presentation	Progressive myelopathy (stepwise or slowly progressive over months to years). Lower extremity weakness + numbness ascending. Foix-Alajouanine syndrome (subacute necrotizing myelopathy): rapidly progressive course with necrosis. Bladder/bowel dysfunction. Pain (radicular or diffuse). Symptoms may worsen with exercise (increased venous pressure). Diagnosis often delayed 1–3 years (misdiagnosed as inflammatory myelopathy, lumbar stenosis, peripheral neuropathy)
MRI findings	T2 hyperintensity (edema) in conus/lower thoracic cord, often extensive (≥3 segments). Flow voids on cord surface (dilated perimedullary veins — pathognomonic but absent in 30–50% on conventional MRI). Cord expansion (edema). Contrast enhancement (chronic breakdown of blood-spinal cord barrier). Key: T2 signal + flow voids in an older male = think dAVF
Diagnosis	Spinal angiography (DSA) = gold standard. Must catheterize ALL feeding arteries (T4–S2). MRA (time-resolved contrast-enhanced) can screen and localize fistula level. Identifies the feeding artery and draining vein
Treatment	Surgical disconnection of the draining vein (intradural) — preferred, definitive, high success rate (>95% obliteration). Endovascular embolization with Onyx or NBCA: less invasive but higher recurrence rate (15–30%). Must occlude the proximal draining vein/fistula point. Outcomes: stabilization in most; improvement in ~50–70% (motor > bladder > sensory). Earlier treatment = better outcome (established cord necrosis is irreversible)

Clinical Pearl — When to Suspect Spinal dAVF: Consider this diagnosis in any patient with: (1) Progressive myelopathy in an older male without clear compressive/inflammatory cause. (2) Lower thoracic/conus T2 signal that seems “too extensive” for the degree of cord compression. (3) Myelopathy that worsens with exercise. (4) Flow voids on MRI surface of cord. (5) Elevated CSF protein without cells (congestive). (6) Failed treatment for presumed “inflammatory myelopathy.” Missing this diagnosis is devastating because it is surgically curable but causes irreversible cord damage if untreated. When in doubt, order a spinal MRA or proceed to spinal angiography.

11.4.3 Metabolic Myelopathies

Subacute Combined Degeneration (SCD) — Vitamin B12 Deficiency

Feature	Details
Pathophysiology	B12 (cobalamin) is essential for methionine synthase and methylmalonyl-CoA mutase. Deficiency → impaired myelin synthesis (SAM pathway) + toxic accumulation of methylmalonic acid and homocysteine. Affects posterior columns (fasciculus gracilis first, then cuneatus) and lateral corticospinal tracts. Can also cause peripheral neuropathy and optic neuropathy
Causes of B12 deficiency	(1) Pernicious anemia (autoimmune gastritis, anti-intrinsic factor antibodies; most common cause in developed countries). (2) Dietary (strict vegans). (3) Malabsorption: celiac, Crohn’s, bariatric surgery, chronic PPI use. (4) Nitrous oxide abuse (“whippets” — rapidly precipitates SCD even with borderline B12 levels by oxidizing cobalt in B12). (5) Fish tapeworm (Diphyllobothrium latum)
Clinical features	(1) Sensory ataxia (loss of proprioception/vibration — dorsal columns). (2) Spastic paraparesis (lateral corticospinal tracts). (3) Romberg positive. (4) Paradox: absent ankle jerks + upgoing plantar responses (combined peripheral neuropathy + myelopathy). (5) Peripheral neuropathy (stocking-glove numbness/paresthesias). (6) Cognitive impairment, dementia, psychiatric symptoms. (7) Megaloblastic anemia (but neurological damage can occur WITHOUT anemia)
MRI	T2 hyperintensity in posterior columns (“inverted V sign” or “reversed rabbit ears” on axial). Cervical and upper thoracic cord. May extend to lateral columns. No enhancement. Cord may be normal-sized or mildly swollen acutely
Diagnosis	Serum B12 (<200 pg/mL definite; 200–400 borderline). Methylmalonic acid (MMA): elevated (most specific — check when B12 borderline). Homocysteine: elevated (less specific). Anti-intrinsic factor antibodies (specific for pernicious anemia). Anti-parietal cell antibodies. CBC: macrocytosis, hypersegmented neutrophils
Treatment	IM cyanocobalamin 1000 μg daily × 7 days, then weekly × 4 weeks, then monthly for life (pernicious anemia). Oral high-dose B12 (1000–2000 μg/day) may be adequate for dietary deficiency. Neurological recovery depends on duration: <6 months of symptoms = good recovery; >12 months = often permanent deficits. CRITICAL: Do not give folate alone without B12 (corrects anemia but worsens/precipitates neurological damage)

Copper Deficiency Myelopathy

Feature	Details
Clinical presentation	Clinically and radiologically identical to SCD from B12 deficiency (posterior + lateral column involvement). Progressive sensory ataxia + spastic paraparesis. Often coexists with peripheral neuropathy (axonal sensorimotor)
Causes	(1) Excess zinc supplementation (most common; zinc induces metallothionein in enterocytes which binds copper preferentially, blocking absorption). (2) Post-gastric surgery. (3) Malabsorption (celiac). (4) Excessive denture cream use (contains zinc). (5) Idiopathic
Diagnosis	Low serum copper (<75 μg/dL), low ceruloplasmin. Check zinc level (elevated zinc explains copper deficiency). CBC: anemia, neutropenia (cytopenia often precedes neurological symptoms). MRI: T2 hyperintensity in dorsal columns (indistinguishable from B12 deficiency)
Treatment	Oral copper supplementation (copper gluconate 2–8 mg/day) or IV copper (2 mg/day × 5 days if severe). Stop zinc source. Neurological recovery variable (stabilization expected; full recovery uncommon if delayed diagnosis)

Other Metabolic/Toxic Myelopathies

Condition	Key Features
Nitrous oxide (N₂O) myelopathy	Oxidizes cobalt in B12 → functional B12 deficiency → SCD. Can occur with normal B12 levels. Recreational use (“whippets”) increasingly common in young adults. Acute/subacute posterior column + corticospinal tract dysfunction. Treatment: stop N₂O, high-dose B12, methionine supplementation. MMA/homocysteine elevated despite normal B12
Vitamin E deficiency	Posterior column + spinocerebellar tract degeneration. Mimics Friedreich ataxia. Causes: abetalipoproteinemia (Bassen-Kornzweig), fat malabsorption, cholestatic liver disease. Progressive ataxia, proprioceptive loss, areflexia. Treatment: high-dose vitamin E supplementation
Hepatic myelopathy	Rare complication of chronic liver disease/portosystemic shunting. Selective corticospinal tract degeneration. Progressive spastic paraparesis. MRI: T1 hyperintensity in globus pallidus (manganese deposition) + subtle cord T2 changes. Treatment: liver transplant (only definitive therapy); portosystemic shunt occlusion may help
Lathyrism	Toxic myelopathy from Lathyrus sativus (grass pea) consumption. Contains BOAA (β-N-oxalylamino-L-alanine), an excitotoxic glutamate analogue. Pure UMN spastic paraparesis. Endemic in Ethiopia, India, Bangladesh during famine. Irreversible. No specific treatment
Konzo	Acute spastic paraparesis from dietary cyanide exposure (insufficiently processed cassava) in sub-Saharan Africa. Affects women and children predominantly. Abrupt onset UMN paraparesis during famine conditions. Irreversible

11.4.4 Radiation Myelopathy

Phase	Timing	Features	Management
Early-delayed (transient)	2–6 months post-RT	Lhermitte sign (most common presentation). Self-limiting (weeks to months). Due to transient demyelination. No cord signal change on MRI typically	Reassurance. No treatment needed. Resolves spontaneously
Late (progressive)	6 months–several years (median 12–18 months)	Progressive myelopathy — usually irreversible. Dose-dependent: risk increases significantly >50 Gy (2 Gy/fraction). T2 hyperintensity, enhancement, possible cord atrophy. Pathology: white matter necrosis, vascular damage, demyelination	No proven treatment. Bevacizumab may help (anecdotal). Hyperbaric oxygen (weak evidence). Prevention: respect cord tolerance (45–50 Gy in conventional fractionation; BED/EQD2 calculations for hypofractionation)

11.4.5 Hereditary Spastic Paraplegia (HSP)

Hereditary Spastic Paraplegia

Feature	Details
Definition	Genetically heterogeneous group (>80 SPG loci identified) characterized by progressive spasticity and weakness of the lower extremities due to corticospinal tract degeneration (retrograde, dying-back axonopathy — longest axons affected first)
Classification	Pure (uncomplicated): spastic paraparesis + bladder urgency + mild dorsal column loss (vibration). Complicated: spasticity + additional features (cerebellar ataxia, cognitive impairment, thin corpus callosum, peripheral neuropathy, optic atrophy, retinitis pigmentosa, epilepsy)
Common genetic forms	SPG4 (spastin): AD, most common adult pure HSP (~40% AD cases). Variable age of onset. SPG3A (atlastin): AD, most common childhood pure HSP. Early onset (<10 years). SPG7 (paraplegin): AR, complicated (cerebellar ataxia + spasticity). SPG11 (spatacsin): AR, most common complicated HSP (thin corpus callosum, cognitive decline). SPG5 (CYP7B1): AR, may respond to cholesterol pathway modulation
Diagnosis	Clinical + family history + genetic testing (gene panel or whole exome sequencing). MRI spine: may show thoracic cord atrophy (subtle). MRI brain: thin corpus callosum (SPG11, SPG15), white matter changes, cerebellar atrophy (SPG7). Exclude structural, metabolic, and acquired causes
Treatment	Symptomatic: Baclofen (oral or intrathecal pump for severe spasticity), tizanidine, botulinum toxin (focal spasticity). Physical therapy and stretching (essential). Ankle-foot orthoses. Bladder management (anticholinergics, CIC). No disease-modifying therapy available

Q: A 35-year-old man presents to the ER with acute-onset severe back pain followed within minutes by bilateral leg weakness and inability to void. He had an aortic stent-graft placed 6 hours ago for a type B aortic dissection. Examination shows flaccid paraplegia, absent bilateral lower extremity reflexes, loss of pain/temperature bilaterally below T10, but PRESERVED vibration and proprioception in both feet. What is the diagnosis, expected MRI findings, and immediate management?

Diagnosis: Anterior spinal artery syndrome (spinal cord infarction) — complicating aortic stent-graft procedure.
Mechanism: The stent-graft likely occluded intercostal/lumbar arteries feeding the artery of Adamkiewicz (the major radiculomedullary artery supplying the lower 2/3 of the cord, typically arising T9–T12 on the left). This results in ischemia of the anterior 2/3 of the cord (anterior spinal artery territory).
Clinical localization: (1) Bilateral motor paralysis (corticospinal tracts — flaccid acutely due to spinal shock). (2) Bilateral loss of pain/temperature below T10 (spinothalamic tracts). (3) PRESERVED dorsal columns (vibration, proprioception) — posterior spinal arteries have separate blood supply and are paired with better collateral flow. (4) Urinary retention (autonomic/sacral involvement). This pattern is pathognomonic for anterior spinal artery syndrome.
Expected MRI findings: (1) T2 hyperintensity in anterior cord (sagittal: “pencil-like” longitudinal signal). (2) DWI restriction (confirms acute ischemia). (3) “Owl eyes” or “snake eyes” on axial T2 (bilateral anterior horn involvement). (4) Possible vertebral body infarction at same level (shared blood supply). Note: MRI may be negative in first 12–24 hours.
Immediate management:
1. MAP augmentation: maintain MAP ≥85–90 mmHg (vasopressors if needed) to maximize spinal cord perfusion
2. Lumbar CSF drainage: place lumbar drain, target CSF pressure <10 cmH₂O (reduces intraspinal pressure, improves perfusion gradient — established protocol in post-aortic surgery cord ischemia)
3. Avoid hypotension at all costs
4. Urgent MRI spine + MRA aorta (confirm diagnosis, assess aortic repair)
5. DVT prophylaxis, bladder catheterization, pressure ulcer prevention
6. No role for systemic thrombolysis in spinal cord infarction (no evidence, bleeding risk post-procedure)
7. Prognosis: guarded; ~50% remain non-ambulatory. CSF drainage within first 6–12 hours post-onset has best chance of benefit

11.5 Cauda Equina & Conus Medullaris Syndromes

11.5.1 Cauda Equina Syndrome (CES) vs. Conus Medullaris Syndrome

Distinguishing these two syndromes is critical for localization and urgency of intervention. They result from pathology at different levels but can overlap (epiconus/conus-cauda lesions).

CES vs. Conus Medullaris Syndrome — Key Distinctions

Feature	Cauda Equina Syndrome	Conus Medullaris Syndrome
Anatomy	Nerve roots below conus (L2–S5 roots in lumbar cistern)	Conus medullaris (terminal spinal cord, typically at L1–L2)
Lesion type	LMN only (peripheral nerve roots)	UMN + LMN mixed (cord terminates here; sacral segments S2–S5 in conus)
Onset	Often gradual (unless acute disc herniation)	Often sudden
Pain	Severe radicular pain (prominent, often bilateral sciatic)	Less prominent pain; more perineal/bilateral
Motor	Asymmetric LMN weakness in L2–S2 distribution. Areflexia. Atrophy	Symmetric mild weakness. UMN signs may be present (if epiconus involved: L4–S1). Babinski may be present
Sensory	Saddle anesthesia (S2–S5 dermatomal). Asymmetric. Radicular pattern	Saddle anesthesia (perianal, perineal). More symmetric. Dissociated sensory loss possible (central cord pattern at conus)
Bladder/Bowel	Urinary retention (atonic bladder — LMN, overflow incontinence). Constipation. Reduced anal tone. Often late	Early bladder/bowel dysfunction (UMN or LMN pattern depending on level). Urinary retention or incontinence. Sexual dysfunction prominent. Reduced anal tone
Reflexes	Absent knee/ankle jerks (depending on root level). Bulbocavernosus reflex absent	Ankle jerks absent (S1–S2). Knee jerks may be preserved. Bulbocavernosus reflex absent. Babinski may be present (epiconus)
Symmetry	Asymmetric (individual roots affected variably)	Symmetric (bilateral cord structure)

Cauda Equina Syndrome — Etiology & Emergency Management

Aspect	Details
Common causes	(1) Large central disc herniation L4–L5 or L5–S1 (most common surgical cause). (2) Spinal stenosis (degenerative or congenital). (3) Tumors: ependymoma (myxopapillary, filum terminale), schwannoma, metastases, lymphoma. (4) Epidural abscess/hematoma. (5) Trauma (burst fracture). (6) Arachnoiditis (post-surgical, post-infection, post-intrathecal injection)
CES classification	CES-Incomplete (CES-I): urinary difficulties (altered sensation, poor stream, need to strain) but still has some bladder control. CES-Retention (CES-R): painless urinary retention with overflow incontinence. CES-R has worse prognosis and requires more urgent decompression
Red flags (when to suspect)	Bilateral sciatica + saddle numbness + urinary difficulty/retention + reduced anal tone. Any patient with acute LBP + new urinary retention = MRI urgently to rule out CES
Imaging	Urgent MRI lumbosacral spine (gold standard). If MRI unavailable: CT myelography. Shows compression, disc sequestration, tumor, abscess
Surgical timing	Surgical emergency. Decompressive laminectomy/discectomy. Traditional teaching: within 48 hours. Meta-analysis (Ahn et al. J Neurosurg Spine 2010): surgery within 48 hours showed better bladder outcomes than delayed. Within 24 hours preferred, and emerging evidence suggests even earlier (<24h) may be better for CES-R. Key principle: earlier = better; don’t wait for a “complete” syndrome to develop before operating
Prognosis	CES-I (incomplete): good recovery expected with early surgery (~70–90% significant improvement). CES-R (retention): recovery less predictable; 30–50% have residual bladder dysfunction. Sexual dysfunction often persists. Duration of symptoms before surgery is strongest predictor of outcome

11.5.2 Syringomyelia

Syringomyelia — Comprehensive Review

Feature	Details
Definition	Fluid-filled cavity (syrinx) within the spinal cord parenchyma. Syringomyelia = syrinx in cord; Syringobulbia = extends into brainstem (medulla)
Pathophysiology	Disruption of normal CSF dynamics at the craniocervical junction or spinal canal → fluid pulsation drives CSF into cord parenchyma. Theories: (1) Williams’ suck/slosh theory (pressure dissociation across obstruction); (2) Oldfield’s piston theory (tonsillar pulsation drives CSF into cord). Result: progressive central cord cavitation and expansion
Etiology	Chiari I malformation (most common association; tonsillar ectopia ≥5 mm below foramen magnum). Post-traumatic (20–30% of SCI patients develop syrinx, months to years later). Tethered cord. Arachnoiditis (post-meningitis, post-surgery). Intramedullary tumor (ependymoma, hemangioblastoma — tumor-associated syrinx). Idiopathic
Clinical features	Cervical/cervicothoracic predilection. (1) “Cape-like” dissociated sensory loss: loss of pain/temperature over shoulders, arms, upper trunk (spinothalamic fibers crossing in anterior commissure are disrupted). Preserved light touch/proprioception initially. (2) LMN signs at level: hand weakness and atrophy (intrinsic hand muscles), areflexia. (3) UMN signs below (legs). (4) Horner syndrome (if syrinx involves C8–T2 intermediolateral column). (5) Neuropathic pain. (6) Scoliosis (especially in pediatric Chiari + syrinx). Progression typically slow (years)
MRI findings	CSF-isointense tubular cavity within cord. T1 low signal, T2 high signal (same as CSF). Cord expansion at level of syrinx. Look for associated pathology: Chiari malformation (tonsillar ectopia), tethered cord, tumor (enhancing component within or at margin of syrinx = tumor). Post-contrast MRI essential to exclude intramedullary tumor
Treatment	Treat the underlying cause: (1) Chiari I + syrinx: posterior fossa decompression (suboccipital craniectomy + C1 laminectomy ± duraplasty). Syrinx resolves/stabilizes in 80%. (2) Post-traumatic: syrinx shunting (syringosubarachnoid or syringoperitoneal shunt) if progressive; arachnolysis. (3) Tumor-associated: tumor resection usually resolves syrinx. (4) Tethered cord: untethering. Observation appropriate for stable, asymptomatic small syrinx

11.5.3 Chiari Malformations

Type	Definition	Clinical Features	Management
Chiari I	Cerebellar tonsil herniation ≥5 mm below foramen magnum. Congenital/developmental (small posterior fossa). Most common type encountered clinically	Often discovered incidentally. Symptomatic: suboccipital headache (exacerbated by Valsalva, coughing), neck pain, syringomyelia symptoms (60–70% have associated syrinx), lower cranial neuropathies (dysphagia, sleep apnea), cerebellar signs, downbeat nystagmus (localizing sign)	Observation if asymptomatic + no syrinx. Posterior fossa decompression (PFD) for symptomatic Chiari I or progressive syrinx. PFD: suboccipital craniectomy + C1 (sometimes C2) laminectomy ± duraplasty. Headache improves in 80–90%. Syrinx resolves in 60–80%
Chiari II (Arnold-Chiari)	Tonsils + vermis + brainstem herniation through foramen magnum. Almost always associated with myelomeningocele	Diagnosed prenatally/neonatally with spina bifida. Hydrocephalus (nearly universal — VP shunt). Brainstem compression. Cranial nerve dysfunction. Apnea	VP shunt for hydrocephalus. PFD if brainstem symptomatic. Myelomeningocele repair (prenatal: MOMS trial showed benefit of prenatal vs postnatal repair)
Chiari III	Occipital or cervical encephalocele containing cerebellar/brainstem tissue	Rare. Usually fatal or severely disabling. High morbidity from brainstem involvement	Surgical repair of encephalocele. Poor prognosis

11.5.4 Tethered Cord Syndrome

Feature	Details
Definition	Abnormal fixation of the spinal cord limiting its normal ascent, resulting in traction on the conus. Normal conus position: at or above L1–L2 disc space in adults. Conus below L2–L3 = low-lying conus suggestive of tethering (though “occult tethered cord” may have normal conus position with an abnormally taut filum)
Causes	(1) Fatty filum terminale (most common). (2) Prior myelomeningocele repair (scar tethering). (3) Lipomyelomeningocele. (4) Dermal sinus. (5) Split cord malformation (diastematomyelia). (6) Sacral dimple with tract
Clinical features	Pediatric: progressive foot deformity (pes cavus), gait abnormality, scoliosis, bladder dysfunction (enuresis persisting beyond expected age), cutaneous stigmata (hairy patch, dimple, lipoma, hemangioma overlying spine). Adult: back/leg pain (exacerbated by flexion/stretching), progressive neurological deficit, bladder dysfunction. Symptoms may worsen during growth spurts or physical activity
Imaging	MRI lumbosacral: low-lying conus (<L2), thickened filum (>2 mm), fatty infiltration of filum (T1 hyperintense), associated anomalies (lipoma, split cord). Note: in “occult tethered cord” conus may be normally positioned but filum is taut and thickened
Treatment	Surgical untethering (section of filum terminale). Low morbidity for fatty filum release. More complex for re-tethering after myelomeningocele repair. Improvement/stabilization in 80–90% for pain and motor; bladder function improvement less reliable

Clinical Pearl — The Myelopathy DDx Approach: When evaluating a patient with progressive myelopathy, systematically consider: (1) Compressive (MRI for structural pathology — spondylosis, tumor, disc, abscess); (2) Inflammatory (MS, NMOSD, MOGAD, sarcoid, TM); (3) Vascular (spinal cord infarction, dAVF); (4) Infectious (HTLV-1, HIV, VZV, TB, syphilis); (5) Metabolic (B12, copper, vitamin E); (6) Genetic (HSP, adrenomyeloneuropathy, Friedreich ataxia); (7) Neoplastic (intramedullary tumor, paraneoplastic); (8) Radiation. A structured approach prevents missed diagnoses. The three most commonly missed myelopathies are: dAVF (surgically curable!), copper deficiency (often from zinc supplements), and HTLV-1 (in endemic populations).

Q: A 14-year-old girl presents with progressive right foot drop, increasing scoliosis, and recent-onset urinary incontinence. Examination shows a hairy patch over the lower lumbar spine, right foot weakness (tibialis anterior 3/5, peronei 3/5), absent right ankle jerk, and decreased perineal sensation. MRI lumbosacral spine shows the conus at L3–L4 level with a thickened, fatty filum terminale. What is the diagnosis and management?

Diagnosis: Tethered cord syndrome due to fatty filum terminale.
Evidence: (1) Low-lying conus at L3–L4 (normal ≤L1–L2 by 3 months of age). (2) Thickened fatty filum on MRI (T1 hyperintense signal in filum, >2 mm diameter). (3) Cutaneous stigmata (hairy patch over lumbosacral spine — a classic marker of occult spinal dysraphism). (4) Progressive neurological deficit: foot drop (L4–L5 radiculopathy from traction), scoliosis (asymmetric tethering), urinary incontinence (sacral nerve dysfunction from conus traction).
Management:
1. Surgical untethering: sectioning of the fatty filum terminale. This is a relatively straightforward procedure with low morbidity. Laminectomy at filum level, identification and division of the thickened filum under intraoperative neuromonitoring (EMG of anal sphincter, lower extremity muscles)
2. Pre-operative urodynamics (baseline bladder function for comparison post-op)
3. Expected outcomes: Pain and motor function stabilize/improve in ~80–90%. Scoliosis may stabilize (less likely to reverse if established). Bladder function improvement variable (less predictable than motor recovery; early intervention before irreversible sacral nerve damage is key)
4. Follow-up: Serial clinical exams + MRI to monitor for re-tethering (especially important in growing children). Scoliosis may need orthopedic co-management
5. Key principle: Operate early in symptomatic tethered cord — neurological deficits are easier to prevent than reverse

11.6 References & Key Guidelines

Key References & Guidelines

SCI & Acute Management

Fehlings MG et al. A clinical practice guideline for the management of acute spinal cord injury: introduction, rationale, and scope. Global Spine J 2017;7(3 Suppl):84S–94S. [AO Spine Guidelines]
Fehlings MG et al. Early versus delayed decompression for traumatic cervical spinal cord injury: results of the Surgical Timing in Acute Spinal Cord Injury Study (STASCIS). PLoS One 2012;7(2):e32037.
Fehlings MG et al. Safety and efficacy of early versus late decompression in traumatic acute cervical spinal cord injury (SCI-POEM): a multicentre prospective cohort study. Lancet Neurol 2021;20(6):449–458.
Bracken MB et al. A randomized, controlled trial of methylprednisolone or naloxone in the treatment of acute spinal-cord injury (NASCIS-2). N Engl J Med 1990;322(20):1405–1411.

CSM & Degenerative Spine

Fehlings MG et al. A clinical practice guideline for the management of degenerative cervical myelopathy: recommendations for patients with mild, moderate, and severe disease and nonmyelopathic patients with evidence of cord compression. Global Spine J 2017;7(3 Suppl):70S–83S. [AO Spine CSM Guidelines]
Weinstein JN et al. Surgical versus nonsurgical therapy for lumbar spinal stenosis. N Engl J Med 2008;358(8):794–810. [SPORT Trial]
Patchell RA et al. Direct decompressive surgical resection in the treatment of spinal cord compression caused by metastatic cancer: a randomised trial. Lancet 2005;366(9486):643–648.

Inflammatory Myelopathy

Transverse Myelitis Consortium Working Group. Proposed diagnostic criteria and nosology of acute transverse myelitis. Neurology 2002;59(4):499–505.
Wingerchuk DM et al. International consensus diagnostic criteria for neuromyelitis optica spectrum disorders. Neurology 2015;85(2):177–189. [IPND 2015 NMOSD Criteria]
Pittock SJ et al. Eculizumab in aquaporin-4-positive neuromyelitis optica spectrum disorder. N Engl J Med 2019;381(7):614–625. [PREVENT]
Cree BAC et al. Inebilizumab for the treatment of neuromyelitis optica spectrum disorder. Lancet 2019;394(10206):1352–1363. [N-MOmentum]
Yamamura T et al. Trial of satralizumab in neuromyelitis optica spectrum disorder. N Engl J Med 2019;381(22):2114–2124. [SAkuraSky]
Banwell B et al. Diagnosis of myelin oligodendrocyte glycoprotein antibody-associated disease: International MOGAD Panel proposed criteria. Lancet Neurol 2023;22(3):268–282.

Vascular Myelopathy

Defined by consensus statement. Spinal dural arteriovenous fistula: diagnosis and treatment. Review articles in Lancet Neurol and J Neurosurg provide current management algorithms.
Sorensen PS et al. Effect of high-dose dexamethasone in carcinomatous metastatic spinal cord compression treated with radiotherapy: a randomised trial. Eur J Cancer 1994;30A(1):22–27.

Metabolic & Other

Stabler SP. Clinical practice: Vitamin B12 deficiency. N Engl J Med 2013;368(2):149–160.
Fink JK. Hereditary spastic paraplegia: clinico-pathologic features and emerging molecular mechanisms. Acta Neuropathol 2013;126(3):307–328.
Adzick NS et al. A randomized trial of prenatal versus postnatal repair of myelomeningocele. N Engl J Med 2011;364(11):993–1004. [MOMS Trial]

12. Neurological Emergencies

This section provides a comprehensive subspecialist-depth review of neurological emergencies requiring immediate recognition and time-critical intervention. Coverage spans raised intracranial pressure (Monro-Kellie doctrine, cerebral edema types, tiered ICP management, decompressive craniectomy evidence from DESTINY/DECIMAL/HAMLET/RESCUEicp, herniation syndromes), brain death determination (AAN 2010/World Brain Death Project 2020 complete protocol, ancillary testing), coma evaluation (FOUR score, pupillary localisation, respiratory patterns), neuroprognostication after cardiac arrest (ERC/ESICM 2021 multimodal algorithm: SSEP, EEG, NSE, MRI), PRES (pathophysiology, hemorrhagic variants, treatment), hypertensive emergencies by syndrome, neuroleptic malignant syndrome vs serotonin syndrome (mechanism, Hunter criteria, treatment), malignant hyperthermia (dantrolene), acute neuromuscular respiratory failure (20-30-40 rule), myasthenic crisis, GBS, botulism, SAH management (ISAT coiling vs clipping, nimodipine, vasospasm DCI), acute bacterial meningitis (antibiotic timing, dexamethasone protocol, de Gans/van de Beek trial), neurotoxicology (opioid, anticholinergic, cholinergic, TCA, lithium, alcohol withdrawal/Wernicke), viral encephalitis (HSV empirical acyclovir, anti-NMDAR encephalitis), and a comprehensive time-critical emergencies rapid reference table.

12.1 Raised Intracranial Pressure & Herniation Syndromes

12.1.1 Physiology of ICP & Cerebral Perfusion

ICP Physiology — Core Concepts for the Neurointensivist

Concept	Details
Normal ICP	5–15 mmHg in adults (supine). <6 in children. Measured via EVD (gold standard), intraparenchymal monitor (Codman, Camino), or lumbar puncture (if no obstruction). Opening pressure on LP: normal <20 cmH₂O (<25 in obese patients)
Monro-Kellie doctrine	Fixed cranial vault volume = brain parenchyma (~80%) + blood (~10%) + CSF (~10%). Increase in one compartment must be compensated by decrease in another, or ICP rises. Compliance: initially, small volume increases are tolerated (CSF/venous blood displacement). When compliance exhausted, small further volume increases cause dramatic ICP rise (exponential pressure-volume curve)
Cerebral perfusion pressure (CPP)	CPP = MAP − ICP. Target: 60–70 mmHg (BTF Guidelines 2016). CPP <50 mmHg = cerebral ischemia. CPP >70 mmHg = risk of ARDS from vasopressor use. Optimal CPP varies by patient (individualized via autoregulation monitoring: PRx, ORx indices)
Cerebral autoregulation	CBF remains constant over MAP 50–150 mmHg in healthy adults (autoregulatory plateau). Mediated by myogenic, metabolic, neurogenic mechanisms. Lost in TBI, SAH, large stroke: CBF becomes pressure-passive → both hypotension and hypertension directly cause ischemia or hyperemia. Chronic hypertension shifts curve rightward (higher MAP needed to maintain CBF)
ICP waveforms	Normal: P1 (percussion) > P2 (tidal) > P3 (dicrotic). Reduced compliance: P2 > P1 (rounding of waveform). Lundberg waves: A waves (plateau waves, 50–100 mmHg lasting 5–20 min — PATHOLOGICAL, indicate critically reduced compliance), B waves (0.5–2/min oscillations — may indicate hydrocephalus), C waves (4–8/min, physiologic)

12.1.2 Types of Cerebral Edema

Type	Mechanism	Location	Examples	MRI/CT Features
Vasogenic	BBB breakdown → plasma proteins + fluid leak into extracellular space	White matter predominant	Tumors (peritumoral edema), abscess, PRES, meningitis, contusion	CT: hypodensity in white matter. MRI: T2/FLAIR high signal, follows white matter tracts. Responds to dexamethasone
Cytotoxic	Cellular swelling from energy failure (Na+/K+ ATPase failure) → intracellular fluid accumulation	Gray + white matter (astrocytes, neurons)	Ischemic stroke, hypoxic-ischemic injury, hepatic encephalopathy	DWI restriction (bright on DWI, low ADC). CT: loss of gray-white differentiation. Does NOT respond to dexamethasone or osmotherapy long-term
Interstitial (transependymal)	CSF forced across ependyma from obstructed ventricles	Periventricular white matter	Obstructive hydrocephalus	CT/FLAIR: periventricular hypodensity/hyperintensity. Responds to CSF drainage
Osmotic	Osmolar gradient drives water into brain	Diffuse	Acute hyponatremia, rapid hemodialysis (dialysis disequilibrium syndrome), DKA (rapid glucose correction)	Diffuse brain swelling. Treat underlying osmolar disturbance
Hydrostatic	Increased transmural pressure gradient	Variable	Acute severe hypertension (related to PRES mechanism)	May overlap with vasogenic pattern

12.1.3 Tiered Management of Raised ICP

Tiered ICP Management Protocol

Tier	Interventions	Key Details & Evidence
Tier 0: General Measures (All Patients)	HOB 30°; midline head position (avoid jugular venous obstruction); adequate sedation/analgesia (propofol, fentanyl); normothermia (fever increases ICP by ~10% per °C); normoglycemia; normocarbia (PaCO₂ 35–40 mmHg); treat seizures; avoid hypotension (MAP ≥70 mmHg); DVT prophylaxis; avoid excessive PEEP (>15 cmH₂O can impede venous return)	Fever is one of the most common and underappreciated causes of ICP elevation. Even low-grade fever increases cerebral metabolic rate by 5–8% per °C. Aggressive fever control with acetaminophen + surface cooling is foundational
Tier 1: First-Line	Osmotherapy: (1) Mannitol 20% 0.5–1 g/kg IV bolus over 15–20 min, repeat q4–6h. Hold if serum osmolality >320 mOsm/L or osmolar gap >20. (2) Hypertonic saline 23.4% 30 mL IV bolus via central line (or 3% NaCl 250 mL bolus), target Na 150–160 mEq/L. CSF drainage via EVD (if in place): intermittent drainage at 10–15 cmH₂O; most rapid ICP reduction method	Mannitol vs HTS: Burgess et al. Neurocrit Care 2016: meta-analysis suggests HTS may be more effective than mannitol for refractory ICP. Mannitol: osmotic diuresis → risk hypovolemia/renal injury if repeated; must replace fluid losses. HTS: no diuresis, expands intravascular volume; preferred in hypovolemic patients. Key: Either agent is effective; choose based on clinical context
Tier 2: Second-Line	Mild hyperventilation: PaCO₂ 30–35 mmHg (temporary measure; onset seconds; duration limited by pH adaptation). Neuromuscular blockade (if agitation/ventilator dyssynchrony causing ICP spikes): cisatracurium preferred (no histamine). Targeted temperature management: 35–36°C (mild hypothermia)	Hyperventilation caution: CO₂ is the most potent regulator of CBF. Each 1 mmHg decrease in PaCO₂ reduces CBF by ~3%. PaCO₂ <30 mmHg can cause dangerous cerebral vasoconstriction and ischemia. Monitor with brain tissue oxygenation (PbtO₂) or jugular venous oximetry (SjvO₂) if available. Never use prolonged hyperventilation as primary ICP strategy
Tier 3: Refractory	Barbiturate coma: Pentobarbital 5–10 mg/kg loading over 30 min → 1–4 mg/kg/h to achieve burst suppression on cEEG. Decompressive craniectomy (DC): removal of large bone flap (≥12 cm in adults) with duraplasty	Barbiturate coma: Reduces CMRO₂ and CBF. Major risks: hypotension (vasopressors usually required), immunosuppression, paralytic ileus. Monitor thiopental/pentobarbital levels. DC evidence (see below). Hypothermia 32–34°C: Eurotherm3235 (Andrews et al. NEJM 2015): therapeutic hypothermia for TBI with elevated ICP showed WORSE outcomes → not recommended as routine ICP management

Decompressive Craniectomy — Key Evidence

Trial	Population	Key Findings
DECIMAL 2007	Malignant MCA infarction, age 18–55, within 48h	DC reduced mortality (25% vs 78%), BUT increased survival with mRS 4 (severe disability). Individual trial pooled into analysis below
DESTINY 2007	Malignant MCA infarction, age 18–60, within 36h	Similar: reduced mortality, increased survival with disability
HAMLET 2009	Malignant MCA infarction, within 96h	Mortality benefit mainly in surgery within 48h subgroup
Pooled analysis (Vahedi et al. Lancet Neurol 2007)	3 European trials above pooled (n=93)	DC: mortality 22% vs 71% (NNT=2). mRS ≤3 at 1 year: 43% vs 21%. Conclusion: DC saves lives but many survivors have severe disability. Requires careful family discussion about goals of care
DESTINY II (Jüttler et al. NEJM 2014)	Malignant MCA infarction, age >60	DC reduced mortality (33% vs 70%). BUT: all survivors had mRS 4–5 at 12 months. In elderly: DC prevents death but does not result in functional independence
RESCUEicp (Hutchinson et al. NEJM 2016)	TBI with refractory ICP >25 mmHg	DC vs medical: lower mortality (26% vs 49%) at 6 months. But higher rate of vegetative state in DC group (8% vs 2%). At 12 months: favorable outcome (GOS-E ≥4) similar. DC is last resort for TBI; consider patient age and bilateral fixed dilated pupils (poor prognosis regardless)

12.1.4 Herniation Syndromes

Cerebral Herniation Syndromes

Type	Anatomy	Clinical Features	Key Findings
Uncal (transtentorial, lateral)	Medial temporal lobe (uncus) herniates over tentorial edge → compresses CN III, PCA, cerebral peduncle	Ipsilateral CN III palsy (dilated pupil, ptosis) → contralateral hemiplegia (cerebral peduncle compression) → progressive coma (brainstem compression). Kernohan notch: contralateral peduncle compressed against opposite tentorial edge → ipsilateral hemiplegia (false localizing sign)	Most important to recognize clinically. Fixed dilated pupil = emergency. Hutchinson pupil: initial brief miosis then progressive mydriasis as CN III compressed. PCA compression → occipital infarction
Central (downward transtentorial)	Bilateral or diffuse supratentorial mass pushes diencephalon + midbrain downward	Stages: Diencephalic (small reactive pupils, Cheyne-Stokes, decorticate) → Midbrain (mid-fixed pupils, central hyperventilation, decerebrate) → Pontine (pinpoint pupils, apneustic breathing) → Medullary (dilated fixed pupils, ataxic breathing → arrest)	Progressive rostral-to-caudal deterioration. Both pupils affected simultaneously (vs uncal: unilateral first)
Subfalcine (cingulate)	Cingulate gyrus herniates under falx cerebri	Contralateral leg weakness (ACA compression). Relatively mild clinically but heralds progression to uncal herniation	CT: midline shift. ACA compression → ACA territory infarction
Tonsillar (foramen magnum)	Cerebellar tonsils herniate through foramen magnum → compress medulla	Sudden respiratory arrest + cardiovascular collapse. Neck stiffness, lower cranial nerve palsy, Cushing triad (hypertension + bradycardia + irregular respiration)	Most immediately life-threatening. Posterior fossa mass (hemorrhage, tumor, abscess). LP is contraindicated if suspected (can precipitate herniation)
Upward (ascending transtentorial)	Posterior fossa mass pushes cerebellum upward through tentorial notch	Midbrain compression: bilateral CN III palsy, altered consciousness. Upward gaze palsy. Hydrocephalus from aqueduct compression	CT: effacement of quadrigeminal cistern. Requires EVD for hydrocephalus + posterior fossa surgery
Transcalvarial (external)	Brain herniates through skull defect (post-craniotomy, fracture)	Fungus cerebri. Bulging through defect	Post-surgical complication. Requires surgical management

Clinical Pearl — Emergency Herniation Protocol (ENLS 2020): When a patient shows signs of acute herniation (new pupil asymmetry, posturing, rapid GCS decline), act within MINUTES: (1) Elevate HOB 30°; (2) Osmotherapy STAT: HTS 23.4% 30 mL IV push (or mannitol 1 g/kg if no central access); (3) Brief hyperventilation to PaCO₂ 30–35 (temporary bridge, NOT sustained); (4) Intubate if not already (RSI avoiding ketamine controversy — actually ketamine is safe and does NOT raise ICP per modern evidence); (5) Urgent CT; (6) Neurosurgical consultation for EVD or surgical decompression. Do NOT wait for imaging before giving osmotherapy if clinical signs of herniation are present.

12.1.5 ICP Monitoring Indications & Multimodal Neuromonitoring

Modality	What It Measures	Key Thresholds	Clinical Use
EVD (external ventricular drain)	ICP (gold standard) + allows CSF drainage	ICP >22 mmHg = treatment threshold (BTF 4th Ed 2016)	Therapeutic + diagnostic. Infection risk ~5–10%. Placed in Kocher’s point (non-dominant hemisphere). Can recalibrate
Intraparenchymal monitor	ICP (Codman, Camino, Raumedic)	Same thresholds as EVD	Lower infection risk. Cannot drain CSF. Cannot recalibrate (drift over days). Measures focal pressure (may differ from global ICP)
Brain tissue oxygenation (PbtO₂)	Local brain oxygen tension	PbtO₂ <20 mmHg = brain hypoxia. <15 = critical. Goal ≥20 mmHg	BOOST-3 (in progress), BOOST-II (2017): PbtO₂-guided therapy reduced brain tissue hypoxia. Placed in vulnerable tissue. Complements ICP monitoring. Treat low PbtO₂: increase FiO₂, optimize CPP, transfuse if Hb low, treat ICP
Cerebral microdialysis	Brain extracellular glucose, lactate, pyruvate, glutamate, glycerol	Lactate/pyruvate ratio (LPR) >40 = metabolic crisis. Low glucose <0.7 mmol/L = energy failure	Research/specialized centers. Detects secondary injury before ICP rises. Guides metabolic optimization
Jugular venous oximetry (SjvO₂)	Global cerebral oxygen extraction	SjvO₂ <55% = ischemia (high extraction). >75% = hyperemia or infarction (low extraction)	Guides hyperventilation (safe if SjvO₂ normal during hyperventilation)
Continuous EEG (cEEG)	Cortical electrical activity	Detect non-convulsive seizures (NCSE), burst suppression during barbiturate coma, assess depth of sedation	Essential in neurocritical care. NCSE prevalence 10–35% in comatose ICU patients. Seizure burden correlates with worse outcome

Q: A 48-year-old woman with a large right MCA infarction (CT shows >50% MCA territory involvement at 18 hours) develops left-sided hemiplegia, right pupil dilation (6 mm, fixed), and GCS drops from 11 to 7 over 30 minutes. CT shows 12 mm midline shift. What is the herniation syndrome, and what is the evidence-based management?

Herniation syndrome: Uncal (transtentorial) herniation — right temporal lobe (swollen from malignant MCA infarction) herniating over right tentorial edge, compressing the right CN III (ipsilateral fixed dilated pupil) and the left cerebral peduncle (contralateral hemiplegia). The progressive GCS decline reflects ongoing brainstem compression.

Immediate emergency management:
1. HOB 30°, midline head position
2. Osmotherapy STAT: HTS 23.4% 30 mL IV bolus (if central line) or mannitol 20% 1 g/kg IV over 15–20 min
3. Brief hyperventilation: target PaCO₂ 30–35 mmHg (temporary bridge to surgery)
4. Intubation if not already secured (GCS 7 = cannot protect airway)
5. Urgent neurosurgical consultation for decompressive craniectomy (DC)

Evidence for DC: This patient is an ideal candidate based on the European pooled analysis (DECIMAL/DESTINY/HAMLET): age <60, malignant MCA infarction >50% territory, clinical deterioration within 48 hours. DC reduces mortality from ~71% to ~22% (NNT=2). However, 43% achieve mRS ≤3 at 1 year vs 21% medical. Critical family discussion: DC saves life but ~50% of survivors will have mRS 4 (severe disability, dependent for basic activities) — specifically for dominant hemisphere infarction, aphasia will be a major factor.

Surgery: Large fronto-temporo-parietal DC (≥12 cm bone flap, including temporal bone to skull base) with duraplasty. Should be performed as early as possible (within 48 hours of stroke onset, before irreversible brainstem injury). Cranioplasty (bone flap replacement) typically at 6–12 weeks.

12.2 Brain Death, Coma Evaluation & Neuroprognostication

12.2.1 Brain Death / Death by Neurologic Criteria (DNC)

Brain death is the irreversible cessation of all functions of the entire brain, including the brainstem. This is legal death in virtually all US states (Uniform Determination of Death Act 1981) and most countries. The AAN Practice Parameter 2010 (Wijdicks et al.) and the World Brain Death Project (Greer et al. JAMA 2020) provide current standards.

Brain Death Determination — Complete Protocol

Step	Requirement	Critical Details
Prerequisites (ALL must be met)	(1) Established etiology capable of causing brain death. (2) Neuroimaging consistent with devastating brain injury. (3) Exclusion of confounders:	No CNS depressants: drug levels below therapeutic (barbiturate <10 μg/mL; wait 5 half-lives or measure levels). Core temperature ≥36°C (hypothermia mimics brain death). SBP ≥100 mmHg (hypotension reduces brainstem reflexes). No neuromuscular blockade (confirm with train-of-four ≥2/4). No severe metabolic derangement (correct Na, glucose, pH, endocrine). No residual effects of therapeutic hypothermia (wait ≥24h after rewarming)
1. Coma	No evidence of arousal or awareness. No eye opening or purposeful response to noxious stimulation (supraorbital pressure, nail bed, TMJ)	Spinal reflexes may be present and do NOT preclude brain death: triple flexion, Lazarus sign (arm raising), finger movements, undulating toe. These are spinal cord-mediated. Must inform family that these may occur to avoid misunderstanding
2. Absent brainstem reflexes (ALL)	(a) Pupillary: fixed pupils (4–9 mm), no response to bright light bilaterally. (b) Corneal: no blink to cotton wisp or saline drop. (c) Oculocephalic (Doll’s eyes): no eye movement with rapid head turning (only if C-spine cleared). (d) Vestibulo-ocular (cold calorics): 50 mL ice water instilled in each ear; observe 1 min, 5 min between ears; no eye deviation. (e) Gag: no response to posterior pharynx stimulation. (f) Cough: no response to deep tracheal suctioning	Atropine in prior code may cause fixed dilated pupils — wait for clearance. CN VII palsy can mimic absent corneal — ensure afferent (CN V) is being tested. Cannot assess oculocephalic if C-spine not cleared — rely on cold calorics. Bilateral tympanic membrane rupture may invalidate cold calorics
3. Apnea test	(a) Preoxygenate 100% FiO₂ × 10 min. (b) Baseline ABG (PaCO₂ 35–45 mmHg). (c) Disconnect ventilator. (d) Deliver O₂ via catheter at carina (6 L/min) or CPAP with O₂. (e) Observe for respiratory effort × 8–10 min. (f) Repeat ABG at end	Positive (= brain death): NO respiratory effort AND PaCO₂ ≥60 mmHg (or ≥20 mmHg rise above baseline). Aborted test: if SpO₂ <85%, SBP <90, or cardiac arrhythmia — reconnect ventilator, obtain ABG, proceed to ancillary testing. PaCO₂ rises ~3 mmHg/min when disconnected. CAUTION: High PEEP patients may desaturate rapidly; consider modified technique (T-piece with CPAP)
Number of exams	AAN 2010: 1 exam in adults (some states/institutions require 2). World Brain Death Project 2020: recommends single comprehensive exam by attending physician experienced in DNC. Observation period between exams if 2 required: 6–24h (varies by jurisdiction)	Pediatric (AAP 2011): <1 month of age: 2 exams 24h apart. 1 month–18 years: 2 exams 12h apart. Ancillary test can shorten observation period
Documentation	Date and time of death = time brain death criteria fulfilled (NOT time of cardiac arrest or ventilator withdrawal). Examiner qualifications. All findings documented	Legal time of death is the completion of the brain death exam (even if heart is still beating on ventilator)

Ancillary Tests for Brain Death

Test	Finding	Sensitivity/Specificity	When Required
Tc-99m HMPAO SPECT	“Hollow skull” — no intracranial radiotracer uptake	High sensitivity (~95%) and specificity (~100%)	Gold standard ancillary. Cannot complete clinical exam (facial trauma, cervical instability, drug confounders, COPD high baseline PaCO₂)
4-vessel cerebral angiography	No intracranial filling above carotid siphon / vertebral entry to skull	Traditional gold standard. High sensitivity	Invasive. Rarely used now; replaced by CTA in many centers
CT angiography (CTA)	Absent opacification of cortical MCA and internal cerebral veins (4-point or 7-point scoring systems)	Sensitivity ~85–95%, varies by methodology	Rapidly available. AAN does not formally endorse but widely accepted. World Brain Death Project: acceptable ancillary
EEG	Electrocerebral inactivity (ECI): no electrical activity >2 μV for ≥30 min, using standard 16+ channels	Sensitivity ~90%. Can be confounded by sedatives, hypothermia, ICU artifact	When drug confounders or apnea test cannot be completed. Must meet technical standards (interelectrode distance, impedance, sensitivity). Artifact is a major limitation in ICU
Transcranial Doppler (TCD)	Reverberating (oscillating) flow pattern or systolic spikes bilaterally in MCAs and basilar artery	Operator-dependent. ~90% sensitivity. 10% no temporal windows	Bedside, non-invasive, repeatable. Best as complement, not standalone

Clinical Pearl — Common Pitfalls in Brain Death Determination: (1) Therapeutic hypothermia (TTM): After cardiac arrest with TTM, must wait ≥24h after rewarming to normothermia AND ensure drug clearance before brain death exam. Hypothermia prolongs drug metabolism dramatically. (2) High-dose barbiturates: Must measure pentobarbital level (<10 μg/mL) or wait 5 half-lives. (3) Spinal reflexes: Lazarus sign (bilateral arm flexion/raising) occurs in up to 75% of brain-dead patients during apnea test. Warn the family and exam team. (4) Posterior fossa lesions: Devastating brainstem lesion may obliterate all brainstem function while cerebral cortex is relatively preserved initially — still qualifies as brain death if ALL criteria met. (5) Chronic CO₂ retainers (COPD): baseline PaCO₂ may be >60 mmHg — use 20 mmHg rise above baseline AND absolute ≥60 as dual threshold, or proceed to ancillary testing.

12.2.2 Coma Evaluation — Structured Approach

Systematic Coma Evaluation

Step	Assessment	Key Findings & Implications
1. Level of consciousness	GCS (Glasgow Coma Scale): E (1–4) + V (1–5) + M (1–6) = 3–15. FOUR Score (Full Outline of UnResponsiveness): Eye (0–4) + Motor (0–4) + Brainstem (0–4) + Respiration (0–4) = 0–16	FOUR Score advantages over GCS: assesses brainstem reflexes, detects locked-in syndrome (eye tracking preserved), evaluates respiratory drive, not confounded by intubation. GCS ≤8 = coma = intubate for airway protection
2. Pupillary exam	Size, reactivity, symmetry	Bilateral fixed dilated: bilateral uncal herniation, anticholinergics, anoxia. Unilateral fixed dilated: ipsilateral CN III (uncal herniation). Bilateral pinpoint: pontine lesion, opioids (naloxone-responsive). Bilateral mid-fixed (4–6 mm): midbrain lesion. Small reactive: metabolic/toxic coma (pupils usually preserved!)
3. Eye movements	Spontaneous, oculocephalic, vestibulo-ocular reflexes	Roving conjugate: intact brainstem, cortical cause. Ocular bobbing: pontine lesion. Ping-pong gaze: bilateral cerebral lesion. Skew deviation: brainstem (posterior fossa). Absent VOR: severe brainstem dysfunction
4. Motor response	Best response to noxious stimuli	Localization: cortical function intact. Withdrawal: subcortical. Flexion (decorticate): above red nucleus. Extension (decerebrate): below red nucleus (midbrain/pons). No response: medulla/spinal or deep metabolic. Asymmetric response = structural lesion
5. Respiratory pattern	Spontaneous breathing pattern	Cheyne-Stokes: bilateral cortical/diencephalic. Central neurogenic hyperventilation: midbrain/pons. Apneustic (inspiratory hold): pons. Cluster/Biot: lower pons/upper medulla. Ataxic (Gasping): medulla (impending arrest)
6. “Treatable” causes	The mnemonic AEIOU TIPS	Alcohol/Acidosis. Epilepsy/Encephalopathy. Insulin (hypo/hyperglycemia). Opioids/Overdose. Uremia. Trauma/Temperature. Infection. Psychiatric/Porphyria/Poison. Stroke/SAH/Shock. Always check glucose, toxicology screen, basic metabolic panel, ammonia, blood gas

12.2.3 Neuroprognostication After Cardiac Arrest

Neuroprognostication After Cardiac Arrest — ERC/ESICM 2021 Algorithm

Modality	Poor Prognosis Indicator (FPR 0–5%)	Timing	Caveats
Clinical exam	Absent pupillary light reflex bilaterally at ≥72h. GCS Motor 1–2 at ≥72h (high sensitivity, moderate specificity alone). Bilateral absent corneal reflex at ≥72h. Status myoclonus within 72h (<24h: Lance-Adams syndrome possible if early myoclonus with EEG-reactive background — NOT always poor)	≥72h post-ROSC (or ≥72h after rewarming if TTM used). Ensure no residual sedation/paralysis	Clinical exam ALONE is insufficient for prognostication. Multimodal approach required. Confounders: sedatives, paralytics, hypothermia. Quantitative pupillometry (NPi) adds objectivity
EEG	Burst suppression without reactivity at ≥72h. Suppressed background without reactivity (<10 μV). Status epilepticus on unreactive background	Continuous monitoring from admission. Prognostic assessment at ≥72h	Reactive EEG background = favorable sign regardless of pattern. Some burst suppression patterns early (<24h) can evolve favorably. Continuous EEG patterns are important for treatment of non-convulsive status
SSEP (somatosensory evoked potentials)	Bilateral absent N20 cortical responses (with preserved N13/N14 peripheral responses to confirm technical adequacy)	≥24h post-ROSC (can be done early; robust even during TTM)	Most reliable single predictor (FPR <1% for bilateral absent N20). Technical pitfalls: electrode issues, ICU electrical noise. Must confirm peripheral N13/N14 present. Unilateral absent N20 is NOT reliable
Serum biomarkers	NSE (neuron-specific enolase) >60 μg/L at 48–72h (highly suggestive of poor outcome). Rising NSE trend (48h > 24h) worse than falling. No absolute cutoff with 0% FPR exists	24h and 48–72h post-ROSC. Serial measurements more valuable than single	Hemolysis falsely elevates NSE (RBCs contain NSE). Neuroendocrine tumors. Use trending, not single values. Should NOT be used as sole basis for WLST
MRI brain	Extensive DWI restriction in cortex/deep gray matter at 2–7 days. Quantitative: whole-brain ADC <650–700 × 10⁻⁶ mm²/s	Optimal timing: day 2–5 post-ROSC	Sensitive for global anoxic injury. Pattern: cortex, basal ganglia, thalami affected. DWI restriction in isolated regions = less predictive. Motion artifact in ICU patients
CT brain	Generalized cerebral edema with loss of gray-white differentiation. GWR (gray-white ratio) <1.10–1.20 at ≥24h	≥24h post-ROSC	Less sensitive than MRI. GWR cutoffs vary by study. Severe generalized edema at 24h = very poor sign

Clinical Pearl — The Multimodal Prognostication Approach: ERC/ESICM 2021 Guidelines emphasize: NEVER use a single modality to determine poor prognosis and withdraw care. The recommended approach: (1) Wait ≥72h post-ROSC (or ≥72h after rewarming) with sedation off. (2) If GCS-M ≤3 at ≥72h: enter prognostication algorithm. (3) Look for ≥2 of the following concordant poor predictors: bilateral absent N20, bilateral absent pupillary/corneal reflex, highly malignant EEG (≥72h), markedly elevated NSE, extensive DWI changes on MRI, status myoclonus <72h. (4) If ≥2 concordant: poor outcome very likely (consider WLST after family discussion). (5) If discordant or uncertain: continue observation, repeat assessments, consider further testing. Self-fulfilling prophecy is the greatest risk in neuroprognostication: if care is withdrawn based on a pessimistic prediction, we cannot know if the patient might have recovered.

Q: A 55-year-old man is admitted after out-of-hospital cardiac arrest with ROSC after 25 minutes of CPR. He underwent TTM at 33°C for 24 hours, rewarmed 36 hours ago. Sedation has been off for 48 hours. At 72h post-rewarming: GCS is E1V1M2 (extension to pain), bilateral pupils 3 mm fixed, corneal reflex absent bilaterally. cEEG shows burst suppression without reactivity. SSEP shows bilateral absent N20 cortical responses with preserved N13 peripheral responses. NSE is 112 μg/L at 72h (24h value was 85). How do you interpret these findings?

Interpretation: Multiple concordant predictors of poor neurological outcome are present.

Prerequisites confirmed: (1) ≥72h after rewarming (≥108h post-ROSC). (2) Sedation discontinued ≥48h. (3) No confounders (drug levels, temperature, metabolic derangement should be verified). (4) No neuromuscular blockade (train-of-four must be confirmed).

Poor prognostic indicators present:
1. Clinical: GCS-M 2 (extension) at ≥72h + bilateral absent pupillary and corneal reflexes = 2 clinical markers of poor prognosis (each with FPR <5%)
2. SSEP: bilateral absent N20 with preserved N13 (technically adequate) = most reliable single predictor of poor outcome (FPR <1%). This essentially confirms that cortical somatosensory processing is absent
3. EEG: burst suppression without reactivity at ≥72h = highly malignant pattern (unreactive background is the key negative feature)
4. NSE: 112 μg/L at 72h, rising from 85 at 24h = markedly elevated with uptrending (both the absolute value >60 and the rising trend support poor prognosis). Ensure hemolysis excluded

Concordance: 4/4 modalities concordantly poor. Per ERC/ESICM 2021 algorithm, ≥2 concordant poor predictors after meeting prerequisites = poor outcome very likely (specificity for poor outcome approaches 100%).

Recommended next steps:
1. MRI brain (if not yet done): expected to show extensive cortical + deep gray matter DWI restriction, confirming global anoxic injury
2. Family meeting: transparent discussion of prognosis using multimodal data. Explain that with 4 concordant negative predictors, chance of meaningful recovery is extremely low (<1%)
3. Goals of care discussion: explore family values, prior patient wishes, advance directives. Discuss options including withdrawal of life-sustaining treatment vs continued observation
4. Organ donation consideration: early involvement of organ procurement organization if family considering this
5. Document thoroughly: all prognostic assessments, confounders excluded, timing, family discussions

12.3 PRES, Hypertensive Emergencies & Acute Drug-Related Encephalopathies

12.3.1 Posterior Reversible Encephalopathy Syndrome (PRES)

PRES — Comprehensive Review

Feature	Details
Pathophysiology	Two proposed mechanisms: (1) Hypertensive theory: BP exceeds autoregulatory limit → breakthrough hyperperfusion → vasogenic edema. Posterior circulation preferentially affected because vertebrobasilar territory has less sympathetic innervation (→ less autoregulatory protection). (2) Endothelial toxicity theory: direct endothelial injury (calcineurin inhibitors, chemotherapy, eclampsia) → capillary leak → vasogenic edema (explains PRES in normotensive patients)
Etiology	Hypertensive emergencies (most common overall). Eclampsia/preeclampsia (most common in obstetric setting). Calcineurin inhibitors (cyclosporine, tacrolimus — dose-related endothelial toxicity). Chemotherapy: bevacizumab (anti-VEGF), cisplatin, gemcitabine, VEGF-TKIs. Autoimmune: SLE, scleroderma renal crisis, TTP/HUS. Sepsis/MAHA. Transplant (solid organ or HSCT). Renal failure
Clinical presentation	(1) Headache (most common, ~50%). (2) Visual disturbances (cortical blindness, homonymous hemianopia, blurred vision, visual neglect — ~60%). (3) Seizures (~60–75%, often the presenting feature; can be status epilepticus). (4) Altered consciousness (confusion to coma). (5) Focal neurological deficits (hemiparesis, aphasia). (6) Hypertension (present in ~75%; but 25% are normotensive!)
MRI findings	Classic: bilateral symmetric T2/FLAIR hyperintensity in posterior parietal-occipital regions (vasogenic edema). Atypical variants (30–40%): frontal involvement, deep gray matter (basal ganglia, thalami, brainstem), unilateral, hemorrhagic. DWI/ADC: high ADC (vasogenic = extracellular water, reversible). If low ADC (cytotoxic) = ischemic conversion = worse prognosis, may be irreversible. Enhancement in ~30% (BBB breakdown)
Hemorrhagic PRES	10–15% of cases. Petechial, focal hematoma, or SAH. Associated with anticoagulation, thrombocytopenia, extreme hypertension. Hemorrhagic PRES = worse outcome, higher mortality
Treatment	1. BP reduction: lower by 15–25% in first hour. IV nicardipine (5–15 mg/h, easily titratable) or labetalol (20 mg IV bolus q10 min or 1–2 mg/min infusion). 2. Eclampsia: IV magnesium sulfate 4–6 g loading → 1–2 g/h + delivery of fetus (definitive treatment). 3. Remove offending agent (reduce calcineurin inhibitor dose, stop bevacizumab). 4. Seizures: levetiracetam or IV lorazepam acutely; avoid phenytoin in eclampsia (Mg is first-line). 5. Monitor in ICU
Prognosis	~90% full neurological recovery within days to weeks if treated promptly. MRI normalizes. Poor prognostic factors: cytotoxic edema on DWI, hemorrhage, delayed treatment, persistent uncontrolled BP, underlying TTP/HUS. Recurrence possible if re-exposed to trigger

12.3.2 Hypertensive Emergency — Neurological Manifestations

Presentation	BP Target	Preferred Agent	Key Points
Hypertensive encephalopathy	Lower MAP 20–25% in first hour	Nicardipine, labetalol, clevidipine	Headache, confusion, visual changes, papilledema, seizures. PRES is imaging correlate. If focal deficit: must exclude stroke before aggressive lowering
Acute ischemic stroke + hypertension	If thrombolysis candidate: <185/110 before tPA, then <180/105 × 24h. If NOT tPA candidate: treat only if >220/120 (permissive hypertension)	Labetalol, nicardipine. Avoid nitroprusside (raised ICP risk)	Do NOT aggressively lower BP in acute ischemic stroke (penumbra perfusion is pressure-dependent). Exception: aortic dissection, acute heart failure
Intracerebral hemorrhage	SBP target <140 mmHg (INTERACT2: safe; ATACH-2: intensive SBP <120 showed harm, increased renal adverse events)	Nicardipine (most studied in ICH trials), labetalol	Rapid lowering to <140 within 1h is safe. Avoid SBP <120 (ATACH-2 showed increased adverse events without benefit). BP variability also harmful
Subarachnoid hemorrhage	SBP <160 mmHg (pre-aneurysm securing)	Nicardipine, labetalol. Avoid nitroprusside (raises ICP)	Balance rebleeding risk (high BP) vs cerebral ischemia (low BP). After aneurysm secured: BP management liberalized. Vasospasm window (day 3–14): avoid hypotension, consider induced hypertension
Eclampsia	SBP <160, DBP <110	IV magnesium sulfate (primary for seizure prevention/treatment) + IV labetalol or IV hydralazine	Delivery of fetus is definitive treatment. Avoid ACE inhibitors (teratogenic), nitroprusside (cyanide toxicity to fetus). Can occur up to 6 weeks postpartum

12.3.3 Neuroleptic Malignant Syndrome (NMS)

NMS vs. Serotonin Syndrome — Critical Comparison

Feature	Neuroleptic Malignant Syndrome (NMS)	Serotonin Syndrome (SS)
Mechanism	Central dopamine (D2) blockade in hypothalamus (thermoregulation) + basal ganglia (rigidity)	Excess serotonergic activity (5-HT_1A and 5-HT_2A receptors)
Causative agents	Dopamine antagonists: typical antipsychotics (haloperidol most common), atypical antipsychotics, metoclopramide, prochlorperazine. Dopamine withdrawal: sudden levodopa/dopamine agonist discontinuation in PD (PD hyperpyrexia syndrome)	Serotonergic drugs: SSRIs, SNRIs, MAOIs, tramadol, meperidine, linezolid (MAOI activity), triptans, MDMA/ecstasy, St John’s wort, dextromethorphan, lithium. Usually from drug interaction (SSRI + MAOI most dangerous)
Onset	Gradual (days to weeks after drug initiation or dose increase)	Rapid (within 24 hours of drug change, often within 6 hours)
Classic tetrad	(1) Hyperthermia (>40°C). (2) Lead-pipe rigidity (generalized, severe). (3) Altered mental status (confusion to coma). (4) Autonomic instability (tachycardia, labile BP, diaphoresis)	(1) Hyperthermia. (2) Clonus (especially lower extremity > upper, ocular clonus). (3) Altered mental status (agitation, confusion). (4) Autonomic instability (diaphoresis, tachycardia, diarrhea)
Key distinguishing feature	RIGIDITY (lead-pipe, not clonus). Bradykinesia. Slow onset. CK markedly elevated (>1000, often >10,000 U/L)	CLONUS + HYPERREFLEXIA (not rigidity). Myoclonus. Rapid onset. Dilated pupils. Diarrhea (bowel hyperactivity). CK may be mildly elevated
Labs	CK massively elevated. WBC elevated. Metabolic acidosis. Acute kidney injury (rhabdomyolysis). LFTs elevated	CK mildly elevated (unless severe). Metabolic acidosis in severe cases. No specific lab test
Diagnosis	Clinical diagnosis. Levenson criteria or DSM-5: exposure to dopamine antagonist + hyperthermia + rigidity + 2 of: diaphoresis, dysphagia, tremor, incontinence, altered consciousness, tachycardia, labile BP, elevated CK, leukocytosis	Clinical diagnosis. Hunter Serotonin Toxicity Criteria: serotonergic agent + any of: spontaneous clonus, inducible clonus + (agitation or diaphoresis), ocular clonus + (agitation or diaphoresis), tremor + hyperreflexia, hypertonia + temperature >38°C + (ocular or inducible clonus)
Treatment	1. Stop offending agent. 2. Aggressive cooling (target <39°C). 3. IV fluids (rhabdomyolysis prevention). 4. Dantrolene 1–2.5 mg/kg IV (muscle relaxant, reduces rigidity/thermogenesis). 5. Bromocriptine 2.5–10 mg PO/NG TID (D2 agonist). 6. Benzodiazepines for agitation. 7. ICU monitoring. Recovery: days to weeks. Mortality: 5–10%	1. Stop ALL serotonergic agents. 2. Cyproheptadine 12 mg PO/NG loading then 2 mg q2h (5-HT_2A antagonist). 3. Aggressive cooling. 4. Benzodiazepines (for agitation, myoclonus, seizures). 5. IV fluids. 6. Avoid: dantrolene (not effective), antipyretics (not central fever). Typically resolves within 24–72h after stopping drug. Mortality: 2–12%

Clinical Pearl — NMS vs SS Quick Mnemonic: “NMS = Slow and Stiff” (gradual onset, lead-pipe rigidity, bradykinesia). “SS = Fast and Twitchy” (rapid onset, clonus, hyperreflexia, myoclonus). If you see clonus, think serotonin syndrome. If you see lead-pipe rigidity without clonus, think NMS. Another key: NMS patients look parkinsonian; SS patients look hyperkinetic. Also remember: PD patients who abruptly stop levodopa can develop a syndrome clinically identical to NMS (“PD hyperpyrexia syndrome” or “neuroleptic malignant-like syndrome”) — treat with restarting dopaminergic medications + dantrolene.

12.3.4 Malignant Hyperthermia

Feature	Details
Trigger	Volatile anesthetic agents (sevoflurane, desflurane, isoflurane, halothane) and/or succinylcholine. Genetic susceptibility (RYR1 mutation, autosomal dominant; DHP receptor mutations)
Pathophysiology	Uncontrolled calcium release from sarcoplasmic reticulum in skeletal muscle → sustained muscle contraction → hypermetabolism, rhabdomyolysis, hyperthermia
Clinical	Intraoperative or early post-op: masseter rigidity after succinylcholine (earliest sign), rising end-tidal CO₂ (hypermetabolism), tachycardia, mixed respiratory/metabolic acidosis, rising temperature (can exceed 43°C), generalized rigidity, hyperkalemia, myoglobinuria
Treatment	1. Stop triggering agent immediately. 2. Dantrolene 2.5 mg/kg IV bolus, repeat q5 min up to 10 mg/kg (muscle relaxant that blocks RYR1 calcium release — SPECIFIC antidote). 3. Hyperventilate with 100% O₂. 4. Active cooling. 5. Treat hyperkalemia (insulin/glucose, calcium gluconate, bicarbonate). 6. Hydration + mannitol for rhabdomyolysis. Without dantrolene, mortality >70%. With dantrolene: <5%

Q: A 32-year-old woman on sertraline (SSRI) and tramadol presents with agitation, confusion, temperature 39.5°C, tachycardia (HR 130), diaphoresis, bilateral lower extremity clonus, hyperreflexia, and dilated pupils. CK is mildly elevated at 450 U/L. What is the diagnosis, key diagnostic criteria, and treatment?

Diagnosis: Serotonin syndrome (serotonin toxicity).

Explanation: This patient is on two serotonergic agents: sertraline (SSRI, inhibits serotonin reuptake) + tramadol (also inhibits serotonin reuptake + weak opioid). The combination creates excess serotonergic activity.

Hunter Serotonin Toxicity Criteria (validated, preferred over Sternbach):
In the presence of a serotonergic agent, requires ONE of: (1) Spontaneous clonus (present — bilateral LE clonus). This single finding with a serotonergic agent satisfies the criteria. Additionally: inducible clonus + diaphoresis (present), hyperreflexia + tremor (hyperreflexia present). Criteria clearly met.

Why NOT NMS: (1) Rapid onset (SS develops within hours). (2) Clonus + hyperreflexia (NMS has rigidity WITHOUT clonus). (3) No lead-pipe rigidity. (4) Serotonergic agents, not dopamine antagonists. (5) CK only mildly elevated (NMS typically >1000–10,000). (6) Dilated pupils (serotonergic effect). (7) No exposure to antipsychotics.

Treatment:
1. Stop ALL serotonergic agents (sertraline AND tramadol)
2. Cyproheptadine 12 mg PO/NG loading, then 2–4 mg q2h until improvement (5-HT_2A antagonist — specific treatment for SS). Maximum 32 mg/day
3. IV benzodiazepines (lorazepam 1–2 mg) for agitation and myoclonus
4. Active cooling if temp >41°C (cooling blankets, ice packs). Antipyretics (acetaminophen) are NOT effective because this is not a centrally-mediated fever
5. IV fluids for rhabdomyolysis prevention and tachycardia
6. Avoid: physical restraints (increase muscle activity → worsen hyperthermia), dantrolene (not effective in SS), additional serotonergic drugs
7. Expected recovery: within 24–72 hours after stopping serotonergic agents. Most resolve within 24h with treatment

12.4 Acute Neuromuscular Emergencies & Time-Critical Syndromes

12.4.1 Acute Respiratory Failure in Neuromuscular Disease

Respiratory failure is the leading cause of death in neuromuscular diseases. Anticipating and monitoring respiratory compromise is a fundamental neurological skill, especially for GBS, MG crisis, ALS, and DMD.

Neuromuscular Respiratory Failure — The “20-30-40 Rule”

Parameter	Critical Threshold	Action
FVC (Forced Vital Capacity)	<20 mL/kg (or <1 L absolute)	Consider elective intubation. Do NOT wait for respiratory distress — intubate before emergency
MIP/NIF (Maximum Inspiratory Pressure)	<−30 cmH₂O (less negative = weaker)	Borderline; watch closely. <−20 cmH₂O = very high risk
MEP (Maximum Expiratory Pressure)	<40 cmH₂O	Poor cough = secretion retention risk = pneumonia. <40 = airway clearance device or intubation
Trend	Serial measurements q4–8h; downward trend	Rate of decline matters more than absolute value. Halving of FVC in 24h = urgent intubation

Danger signs: Paradoxical breathing (abdominal paradox — in-drawing on inspiration = diaphragm failure), inability to count to 20 in one breath, orthopnea (worse supine = diaphragm weakness), SaO₂ desaturation (late sign), rising PaCO₂ (very late, impending arrest). Do NOT rely on SpO₂ alone — O₂ saturation can remain normal until moments before arrest in pure hypoventilation.

Specific Neuromuscular Emergencies

Condition	Emergency Features	Management
Myasthenic Crisis	Rapid worsening of bulbar/respiratory weakness requiring ventilatory support. Precipitants: infection (most common), medications (aminoglycosides, fluoroquinolones, beta-blockers, Mg), surgery, pregnancy, tapering immunosuppression. FVC <1 L = intubate	Hold cholinesterase inhibitors (pyridostigmine) during crisis (worsens secretions). PLEX ×5 exchanges over 10–14 days (faster onset, preferred) OR IVIg 2 g/kg over 2–5 days (equivalent efficacy). High-dose IV methylprednisolone 1 g × 3–5 days as bridge. Treat precipitant. (See Section 5 for full MG management)
GBS with respiratory failure	25–30% of GBS require mechanical ventilation. Brighton criteria for diagnosis. Autonomic instability: labile BP, bradycardia (may need pacemaker), ileus, urinary retention. Bilateral facial palsy + bulbar weakness = high intubation risk	Serial FVC (20-30-40 rule). Elective intubation when FVC trending toward <20 mL/kg. IVIG 0.4 g/kg × 5 days OR PLEX (5 exchanges over 2 weeks) — equivalent, but IVIG more convenient. Avoid succinylcholine for RSI (hyperkalemia from upregulated nicotinic receptors). DVT prophylaxis, pain management (often severe neuropathic pain), autonomic monitoring
Botulism	Descending paralysis starting with bulbar signs (ptosis, diplopia, dysarthria, dysphagia). Dilated FIXED pupils (distinguishes from MG). Dry mouth, constipation (anticholinergic autonomic). Respiratory failure. Foodborne, wound, infant, iatrogenic	Equine heptavalent botulinum antitoxin (CDC release) — give ASAP (halts disease progression; doesn’t reverse paralysis). Wound debridement + antibiotics (wound botulism). Supportive: mechanical ventilation (weeks to months). Avoid aminoglycosides (worsen NMJ blockade). Infant botulism: BabyBIG (human-derived BIG-IV)
Acute flaccid paralysis differential	GBS, botulism, polio/AFM, transverse myelitis, severe hypokalemia, hypermagnesemia, organophosphate poisoning	EMG/NCS for GBS vs NMJ vs anterior horn. Lumbar puncture (albumino-cytological dissociation in GBS). Stool culture/PCR for botulism/enterovirus. Spinal MRI for myelopathy. Electrolytes (K, Mg)

12.4.2 Subarachnoid Hemorrhage (SAH) — Neurocritical Care

SAH Management — Time-Critical Interventions

Phase	Complication	Management
Immediate (0–72h)	Rebleeding (highest risk first 24h; 4–14% within 24h untreated). Risk: SBP >160, large aneurysm, poor Hunt-Hess grade	BP control SBP <160 until aneurysm secured. Secure aneurysm ASAP: endovascular coiling (preferred, ISAT trial: coiling superior to clipping for suitable aneurysms, lower morbidity/mortality at 1 year) vs neurosurgical clipping. IV tranexamic acid (if >3h delay to aneurysm treatment, reduces early rebleeding risk — not recommended routinely). Avoid anticoagulants/antiplatelets until secured
Hydrocephalus	Acute obstructive hydrocephalus (blood in ventricles; 15–20% of SAH) or communicating hydrocephalus	External ventricular drain (EVD) if hydrocephalus + impaired consciousness. Weaning EVD: gradual (over days) vs immediate clamping. Shunt insertion for persistent communicating hydrocephalus (10–15%)
Vasospasm & DCI (Days 3–14)	Delayed cerebral ischemia (DCI): most feared complication, peak day 5–10. Angiographic vasospasm in 70%; symptomatic DCI in 30%. Worse with poor-grade SAH, large subarachnoid blood, cigarette smoking	1. Nimodipine 60 mg PO q4h × 21 days (α-1 and L-type calcium channel blocker; prevents DCI though not angiographic vasospasm; level A evidence; ONLY calcium channel blocker proven to improve neurological outcome in SAH). 2. Euvolemia (avoid hypovolemia; "Triple H" therapy abandoned for euvolemia + induced hypertension only if DCI). 3. TCD monitoring (daily/q12h): MCA velocities >120 cm/s = vasospasm; >200 cm/s = severe. 4. Induced hypertension (SBP 160–200) for symptomatic DCI. 5. Endovascular rescue (intra-arterial verapamil, balloon angioplasty) for refractory DCI
Electrolyte disturbances	Hyponatremia (most common electrolyte complication): SIADH (euvolemic) vs cerebral salt wasting (hypovolemic — distinguish by volume status!). Hyponatremia worsens cerebral edema and seizure threshold	SIADH: fluid restriction. Cerebral salt wasting (CSW): volume replacement + salt supplementation. CSW is more common than SIADH in SAH. Hypertonic saline may be needed. Avoid aggressive fluid restriction in SAH (risk of vasospasm/DCI)
Cardiac complications	ECG changes (T-wave inversions, QTc prolongation, ST changes — 50–100% of SAH). Neurogenic stunned myocardium (Takotsubo-like, apical ballooning pattern). Troponin elevation in 30%	Cardiac monitoring in ICU. Echo (TTE/TEE) for cardiac function. Arrhythmias: treat if hemodynamically significant. Avoid QTc-prolonging drugs. Neurogenic cardiomyopathy usually reversible over days to weeks
Grading scales	Clinical severity: Hunt-Hess scale (I–V; grade I: asymptomatic or minimal headache; grade V: deep coma, decerebrate posturing). CT blood burden: Fisher grade (modified Fisher: grade I–IV based on subarachnoid blood thickness and IVH) — predicts vasospasm risk	Higher Hunt-Hess and Fisher grade = higher vasospasm/DCI risk = more intensive monitoring

12.4.3 Acute Bacterial Meningitis — Emergency Protocol

Step	Action	Details
1. Recognition	Classic triad: fever + headache + neck stiffness (present in <50%!). Kernig + Brudzinski signs (low sensitivity but specific). Altered consciousness. Petechial/purpuric rash = N. meningitidis — EMERGENCY	The classic triad is ABSENT in up to 50% of cases. Any 2 of 4 features (headache, fever, neck stiffness, altered consciousness) is sufficient to act. Do NOT wait for all three
2. CT before LP?	CT head first if: papilledema, focal neurological deficit, immunocompromised, new seizure, GCS <10, known CNS disease. Otherwise: LP can be done without CT if none of these risk factors	CRITICAL: Do NOT delay antibiotics for CT or LP. Draw blood cultures FIRST, then immediately start antibiotics, THEN do CT/LP. Antibiotics within 60 min of recognition. Every hour of delay increases mortality by ~5–10%
3. Antibiotics	Empiric: Ceftriaxone 2 g IV q12h (all ages; S. pneumoniae, N. meningitidis). Add ampicillin 2 g IV q4h if age >50, immunocompromised, or pregnant (Listeria coverage). Add vancomycin 15–20 mg/kg IV q8–12h (cephalosporin-resistant pneumococcus)	After CSF sent: narrow if organism identified. Penicillin allergy: meropenem + vancomycin. Duration: S. pneumoniae 10–14 days; N. meningitidis 7 days; Listeria 21 days; gram-negative (E. coli, Klebsiella) 21 days
4. Dexamethasone	Dexamethasone 0.15 mg/kg IV q6h × 4 days. Give BEFORE or WITH first antibiotic dose (no benefit if given after)	de Gans & van de Beek NEJM 2002: dexamethasone reduced unfavorable outcomes (34% vs 25%) and mortality (15% vs 7%) specifically in S. pneumoniae meningitis. Mechanism: reduces cytokine-mediated inflammation, decreases brain edema, maintains BBB. May reduce CSF antibiotic penetration — controversial for N. meningitidis but give empirically, discontinue if not S. pneumoniae
5. CSF interpretation	Bacterial: WBC >1000 (PMN predominant), protein >100, glucose <0.4 serum ratio, positive culture/Gram stain. Viral: WBC 100–1000 (lymphocytic), protein mildly elevated, glucose normal	Partially treated meningitis: culture may be negative; antigen tests (pneumococcal, meningococcal) + FilmArray meningitis/encephalitis panel can help

12.4.4 Time-Critical Neurological Emergencies Summary Table

Time-Critical Neurological Emergencies — Rapid Reference

Emergency	Time Window	Key Intervention	Outcome Impact
LVO ischemic stroke — tPA	<4.5h from onset	IV alteplase 0.9 mg/kg (max 90 mg); door-to-needle <60 min	NNT ~10 for independence (mRS 0–2)
LVO ischemic stroke — EVT	<24h (selected patients); ideally <6h	Mechanical thrombectomy; door-to-groin <90 min	NNT 2.6 for independence; 6% absolute mortality benefit
SAH — aneurysm securing	Within 24h (ideally same-day)	Endovascular coiling or surgical clipping; nimodipine 60 mg q4h	Rebleeding risk: 4–14% untreated first 24h
Status epilepticus — benzodiazepine	<5 min of seizure; phase 1 by 20 min	Lorazepam 0.1 mg/kg IV or IM midazolam 10 mg; second agent by 30 min	NNT 5 for terminating SE; each 10-min delay increases refractoriness by 30%
MESCC — dexamethasone	IMMEDIATE on recognition	Dexamethasone 10 mg IV bolus then 4 mg q6h; surgery within 24–48h	Ambulatory at treatment: 80% stay ambulatory vs 10% paraplegic
Bacterial meningitis — antibiotics	<60 min of recognition	Ceftriaxone + vancomycin ± ampicillin; dexamethasone BEFORE antibiotics	Each hour delay increases mortality 5–10%
Cauda equina syndrome	<24–48h (earlier = better)	Decompressive laminectomy/discectomy	CES-I early surgery: 70–90% improvement; CES-R: 30–50% bladder recovery
Herniation — osmotherapy	IMMEDIATE	HTS 23.4% 30 mL IV push; mannitol 1 g/kg IV; HOB 30°; hyperventilation bridge	Delays herniation by minutes to hours; bridge to definitive surgical decompression
Malignant hyperthermia	IMMEDIATE (intraoperative)	Stop triggering agent; dantrolene 2.5 mg/kg IV bolus; 100% O₂	Mortality: >70% without dantrolene vs <5% with
Botulism — antitoxin	ASAP (before paralysis progresses)	Heptavalent equine antitoxin (HBAT) via CDC emergency operations	Halts progression; doesn’t reverse existing paralysis
Acute SCI — MAP target	Within first 7 days	MAP ≥85–90 mmHg (vasopressors); surgical decompression <24h	Every AIS grade improvement = major functional benefit; STASCIS: 19.8% vs 8.8%
Stroke — ICH blood pressure	Within 1h of recognition	Nicardipine to SBP <140; avoid <120 (ATACH-2)	Reduces hematoma expansion; does not improve functional outcome (INTERACT2)

Clinical Pearl — The Neurological Emergency Mindset: In neurological emergencies, the key is recognizing that time = neurons. Every minute of ischemia destroys ~1.9 million neurons in stroke. Every hour of untreated meningitis deepens the inflammatory cascade. Every day of untreated SAH risks rebleeding. The most dangerous cognitive error is anchoring to a diagnosis and delaying treatment. The second most dangerous is waiting for complete evaluation before starting empirical therapy. In bacterial meningitis: start antibiotics before the LP result. In suspected herniation: give osmotherapy before CT confirms it. In status epilepticus: give benzodiazepine at the 5-minute mark, not after 10 minutes of observation. Train yourself to identify the “do-not-miss” emergency in every altered patient and act on it first.

12.5 Neurotoxicology & Acute CNS Infections in Emergency

12.5.1 Drug-Induced Encephalopathy — Key Toxidromes

Neurotoxicology Syndromes — Diagnosis & Antidotes

Toxidrome	Agents	Clinical Features	Antidote/Treatment
Opioid toxidrome	Morphine, heroin, oxycodone, fentanyl, methadone, tramadol	Miosis + respiratory depression + altered consciousness (triad). Bradycardia, hypotension. Pulmonary edema (heroin). Seizures (tramadol, meperidine — normeperidine accumulation)	Naloxone 0.4–2 mg IV/IM/IN (repeat q2–3 min; titrate to respiratory drive NOT full reversal). Infusion for long-acting opioids. Caution: precipitation of acute withdrawal (seizures, pulmonary edema). Fentanyl analogs (carfentanil): may require >10 mg total naloxone
Anticholinergic toxidrome	Atropine, scopolamine, diphenhydramine (Benadryl), TCAs, antipsychotics, jimsonweed, deadly nightshade	“Mad as a hatter, blind as a bat, hot as a hare, red as a beet, dry as a bone”: confusion/psychosis, mydriasis (fixed dilated pupils), hyperthermia, flushing, anhidrosis. Tachycardia, urinary retention, ileus. Seizures, coma in severe cases	Physostigmine 1–2 mg IV slow push (AChE inhibitor; crosses BBB). For agitation/delirium when benzodiazepines inadequate. Contraindicated if TCA overdose (cardiac toxicity: physostigmine can cause bradycardia/asystole). ECG first! Benzodiazepines for agitation. Cooling for hyperthermia. Foley for urinary retention
Cholinergic toxidrome (SLUDGE/DUMBBELS)	Organophosphates (insecticides, nerve agents), carbamates, pilocarpine, physostigmine, neostigmine	SLUDGE: Salivation, Lacrimation, Urination, Defecation, GI distress, Emesis. PLUS: bronchospasm/bronchorrhea (most deadly), miosis, bradycardia. Nicotinic effects: muscle fasciculations → weakness → flaccid paralysis, tachycardia, hypertension. KILLER-Bs: Bronchospasm, Bronchorrhea, Bradycardia	Atropine (antimuscarinic): large doses needed (2 mg IV q5–10 min until secretions dry; may need >100 mg). Pralidoxime (2-PAM) 1–2 g IV over 15–30 min (reactivates AChE before “aging” — must give within 24–48h, especially for nerve agents). Benzodiazepines for organophosphate-induced seizures (not phenytoin — ineffective for cholinergic seizures). Decontamination critical (remove clothing, wash skin)
Sympathomimetic toxidrome	Cocaine, amphetamines, MDMA, methamphetamine, PCP, ephedrine	Tachycardia, hypertension, hyperthermia, diaphoresis, mydriasis. Agitation, psychosis, seizures. Stroke (ischemic or hemorrhagic from vasospasm/hypertension). Rhabdomyolysis. MDMA: hyponatremia (SIADH + water intake)	Benzodiazepines (first-line for agitation, hypertension, seizures). Avoid beta-blockers (unopposed alpha → severe hypertension). Phentolamine or nitroprusside for severe hypertension. Cooling for hyperthermia. IV fluids. MDMA-induced hyponatremia: hypertonic saline if severe/symptomatic
Tricyclic antidepressant (TCA) overdose	Amitriptyline, imipramine, clomipramine, nortriptyline	Anticholinergic features + QRS widening (>100 ms = cardiac toxicity risk) + hypotension + seizures. Prolonged QTc → TdP. Altered consciousness. Anticholinergic delirium. QRS >160 ms = ventricular arrhythmia risk	Sodium bicarbonate 1–2 mEq/kg IV bolus (alkalinizes serum: reduces TCa binding to Na channel; targets serum pH 7.45–7.55). Indicated: QRS >100 ms, ventricular arrhythmia, hypotension. Avoid physostigmine (cardiac risk). Avoid flumazenil. Lipid emulsion therapy for refractory cases. Intubate early (rapid deterioration)
Lithium toxicity	Acute overdose vs chronic toxicity (different clinical pictures)	Acute: GI dominant (N/V/D), then delayed neurological. Chronic: neurological dominant (tremor → ataxia → confusion → coma → seizures). SILENT syndrome: Syndrome of Irreversible Lithium-Effectuated NeuroToxicity. EEG: diffuse slowing, triphasic waves	Stop lithium. IV normal saline (maintain adequate renal clearance). Hemodialysis for: Li >4 mEq/L any context, or >2.5 mEq/L with symptoms, or renal failure, or persistent/deteriorating neurotoxicity (Li distributes into CNS, rebounds after HD — may need multiple sessions). Whole-bowel irrigation for acute ingestion
Alcohol withdrawal & Wernicke	Alcohol withdrawal: CNS disinhibition after ethanol cessation. Wernicke: thiamine (B1) deficiency	Alcohol withdrawal: tremor (6–8h) → seizures (12–24h, usually brief tonic-clonic) → delirium tremens (48–72h): confusion + tremor + autonomic instability (fever, diaphoresis, tachycardia). Wernicke encephalopathy (classic triad): oculomotor abnormalities (horizontal nystagmus, CN VI palsy, conjugate gaze palsy) + ataxia + confusion/altered consciousness. MRI: bilateral symmetric FLAIR/DWI signal in mammillary bodies, periaqueductal gray, medial thalami	Alcohol withdrawal: Benzodiazepines (CIWA-Ar protocol; lorazepam preferred in liver disease). Phenobarbital for refractory DT or benzo-resistant withdrawal. Propofol or dexmedetomidine adjuncts for severe DTs. Wernicke: IV thiamine 500 mg TID × 2–3 days (NEVER give dextrose before thiamine — can precipitate acute Wernicke by depleting remaining thiamine). Glucose and thiamine together is acceptable. Treat Wernicke aggressively to prevent permanent Korsakoff syndrome (anterograde amnesia)

12.5.2 Viral Encephalitis — Emergency Approach

Pathogen	Key Features	Diagnosis	Treatment
HSV encephalitis	Most common sporadic fatal encephalitis. Temporal lobe predilection (fever + personality/behavioral change + focal seizures). MRI: unilateral or bilateral temporal/insular T2 hyperintensity. CSF: lymphocytic pleocytosis, elevated protein, HSV PCR (sensitivity 96%, specificity 99%)	CSF HSV-1/2 PCR. MRI brain (temporal + insular changes). EEG: temporal periodic lateralized epileptiform discharges (PLEDs/LPDs)	IV acyclovir 10 mg/kg q8h × 14–21 days. Start EMPIRICALLY if clinical + imaging suspicion (do not wait for PCR). Steroid adjunct controversial (consider if vasculitis or severe edema). Without treatment: mortality 70%; with acyclovir: mortality ~15%
Anti-NMDA receptor encephalitis	Most common autoimmune encephalitis. Young women, ovarian teratoma (50% of cases in young women). Stages: prodrome (fever, headache) → psychiatric phase (psychosis, behavioral change — often initially admitted to psychiatry) → unresponsive/catatonic phase → hyperkinetic phase (orofacial dyskinesias, abnormal movements) → autonomic instability. CSF: lymphocytic pleocytosis. Anti-NMDAR IgG in serum/CSF	Serum AND CSF anti-NMDAR antibodies (CSF more sensitive). MRI often normal (FLAIR changes in 30–50%). EEG: “extreme delta brush” (pathognomonic). Screen for teratoma (pelvic MRI/US in women, CT chest for others)	1st-line: IV methylprednisolone 1 g × 5 days + IVIg 2 g/kg. Teratoma removal (if found — dramatically improves outcomes). 2nd-line (refractory): rituximab (anti-CD20) ± cyclophosphamide. Up to 80% improve with aggressive immunotherapy. Relapses in 12–25%
Arboviral encephalitis	West Nile virus (WNV): flavivirus; Culex mosquito; poliomyelitis-like acute flaccid paralysis (anterior horn); DWI lesions in deep gray matter (substantia nigra, basal ganglia, thalami). Eastern equine encephalitis (EEE): severe (mortality 30–75%); periventricular T2 changes. Japanese encephalitis (JE): most common cause of viral encephalitis worldwide; thalamic T2 signal; vaccine-preventable	Serum and CSF IgM antibodies (primary diagnostic). PCR less sensitive in CSF	No specific antiviral; supportive care. IVIg (WNV: possible benefit). JE vaccine (prevention)

Clinical Pearl — The “Treat First, Diagnose Later” Principle in Encephalitis: When a patient presents with acute encephalitis (fever + confusion + seizures), immediately start empirical IV acyclovir (covers HSV and VZV), empirical ceftriaxone + vancomycin + dexamethasone (covers bacterial meningitis), and consider empirical ampicillin (covers Listeria in elderly/immunocompromised). Then obtain LP, MRI, and serological workup. The risk of treating empirically and it not being needed is vastly outweighed by the risk of delaying treatment. HSV encephalitis without acyclovir has 70% mortality; started within 48h it drops to 15%. This is one situation in neurology where the diagnostic workup must run parallel to, not precede, treatment.

12.6 References & Key Guidelines

Key References & Guidelines

ICP & Herniation

Carney N et al. Guidelines for the management of severe traumatic brain injury, 4th edition. Neurosurgery 2017;80(1):6–15. [BTF 4th Ed 2016]
Andrews PJ et al. Hypothermia for intracranial hypertension after traumatic brain injury (Eurotherm3235). N Engl J Med 2015;373(25):2403–2412.
Hutchinson PJ et al. Trial of decompressive craniectomy for traumatic intracranial hypertension (RESCUEicp). N Engl J Med 2016;375(12):1119–1130.
Jüttler E et al. Hemicraniectomy in older patients with extensive middle-cerebral-artery stroke (DESTINY II). N Engl J Med 2014;370(12):1091–1100.
Vahedi K et al. Early decompressive surgery in malignant infarction of the middle cerebral artery: a pooled analysis of three randomised controlled trials. Lancet Neurol 2007;6(3):215–222.

Brain Death & Prognostication

Wijdicks EF et al. Evidence-based guideline update: determining brain death in adults. Neurology 2010;74(23):1911–1918. [AAN 2010 Brain Death]
Greer DM et al. Determination of brain death/death by neurologic criteria: the World Brain Death Project. JAMA 2020;324(11):1078–1097.
Sandroni C et al. Neuroprognostication after cardiac arrest. Intensive Care Med 2022;48(10):1513–1523. [ERC/ESICM 2021 Guidelines Update]

SAH & Hypertensive Emergencies

Molyneux AJ et al. International subarachnoid aneurysm trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients. Lancet 2002;360(9342):1267–1274.
Anderson CS et al. Rapid blood-pressure lowering in patients with acute intracerebral hemorrhage (INTERACT2). N Engl J Med 2013;368(25):2355–2365.
Qureshi AI et al. Intensive blood-pressure lowering in patients with acute cerebral hemorrhage (ATACH-2). N Engl J Med 2016;375(11):1033–1043.

Meningitis & Encephalitis

de Gans J, van de Beek D. Dexamethasone in adults with bacterial meningitis. N Engl J Med 2002;347(20):1549–1556.
Tunkel AR et al. Practice guidelines for the management of bacterial meningitis. Clin Infect Dis 2004;39(9):1267–1284. [IDSA Guidelines]
Dalmau J et al. Anti-NMDA-receptor encephalitis: case series and analysis of the effects of antibodies. Lancet Neurol 2008;7(12):1091–1098.

NMS & Serotonin Syndrome

Boyer EW, Shannon M. The serotonin syndrome. N Engl J Med 2005;352(11):1112–1120.
Strawn JR et al. Neuroleptic malignant syndrome. Am J Psychiatry 2007;164(6):870–876.