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Moyamoya Disease: Pathophysiology, Presentation & Revascularization Strategies

Moyamoya disease is a rare, progressive cerebrovascular disorder characterized by bilateral stenosis/occlusion of the terminal internal carotid arteries (ICAs) at the skull base, with development of fragile, dilated collateral vessels ("moyamoya" = "puff of smoke" in Japanese) at the base of the brain.

Epidemiology & Etiology

Bimodal age peaks: Children (5–10 yr) and adults (30–50 yr).
Female predominance: 1.5–2:1.
Genetics: RNF213 p.R4810K variant (strong East Asian association); BRCC3, ACTA2, GUCY1A3 in non-Asian populations. Multifactorial: genetic susceptibility + environmental triggers.
Associations: Neurofibromatosis type 1, Down syndrome, sickle cell disease, cranial radiation, thyroid disease (these are "Moyamoya syndrome").

Pathophysiology

Progressive intimal hyperplasia → luminal narrowing of supraclinoid ICAs, proximal ACA/MCA → chronic hypoperfusion → compensatory angiogenesis (moyamoya vessels) → fragile collaterals prone to thrombosis (ischemic stroke) or rupture (hemorrhagic stroke).

Clinical Presentation

Diagnostic Imaging

MRA / CTA: Gold standard non-invasive. Shows "moyamoya vessels" at basal ganglia/thalamus, ICA stenosis/occlusion.
DSA (Digital Subtraction Angiography): Definitive for surgical planning; assesses collateral flow, aneurysm detection.
Perfusion imaging (CTP/MRP/SPECT): Quantifies cerebral blood flow (CBF), cerebrovascular reserve (CVR) with acetazolamide challenge — critical for surgical candidacy.

Suzuki Staging (Angiographic)

Stage 1: Narrowing of carotid fork → Stage 6: Complete occlusion with disappearance of moyamoya vessels.

Treatment

Revascularization Surgery (Definitive)

Direct (STA-MCA bypass): Immediate flow restoration; technically demanding; preferred in adults.
Indirect (EDAS, EMS, pial synangiosis): Promotes angiogenesis over months; preferred in children (better angiogenic potential).
Combined: Often used.

Medical Management

Antiplatelets (aspirin) — primary prevention; avoid in hemorrhagic presentation.
Calcium channel blockers (for headache/vasospasm).
Strict BP control (avoid hypotension → watershed infarcts; avoid hypertension → hemorrhage).
Seizure prophylaxis if history of seizures.

Prognosis

Without surgery: 50–70% stroke recurrence. With successful revascularization: stroke risk <3–5%/yr, cognitive stabilization. Lifelong surveillance required.

Diseases - Related Articles

Population	Predominant Presentation
Children	Ischemic: TIAs (limb weakness, speech arrest), strokes, seizures, cognitive decline, involuntary movements. Often triggered by hyperventilation (crying, blowing).
Adults	Hemorrhagic: Intraventricular/subarachnoid hemorrhage from ruptured moyamoya vessels. Also ischemic events.