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Moyamoya Disease: The "Puff of Smoke" Cerebrovascular Disorder

Moyamoya disease (MMD) is a rare, progressive cerebrovasculopathy characterized by bilateral stenosis/occlusion of the terminal internal carotid arteries (ICAs) and the proximal anterior (ACA) and middle (MCA) cerebral arteries. The name, Japanese for "puff of smoke," describes the angiographic appearance of the fragile, dilated collateral vessels (moyamoya vessels) that form to compensate for the occlusion. It is a leading cause of stroke in children and young adults in East Asia.

Epidemiology & Risk Profile

  • Geography: Highest prevalence in Japan, Korea, China (1:10,000 to 1:100,000). Lower but rising recognition globally.
  • Sex: Female predominance (1.5-2:1).
  • Age Distribution: Bimodal peaks: Children (5-10 yrs) and Adults (30-50 yrs).
  • Genetics: RNF213 c.14576G>A (p.R4810K) variant — major susceptibility locus in East Asians (95% of familial, 73% sporadic). Other genes: BRCC3, ACTA2, GUCY1A3. Familial ~10-15%.
  • Associations: Neurofibromatosis type 1, Down syndrome, sickle cell disease, thyroid disease, cranial radiation — "Moyamoya Syndrome" (secondary).

Clinical Phenotypes

PresentationPediatric (Ischemic)Adult (Hemorrhagic + Ischemic)
MechanismHypoperfusion → TIA/strokeFragile collaterals rupture → ICH (50%); also ischemia
SymptomsTransient hemiparesis, speech arrest, seizures, cognitive decline, headache, "crying-induced" hyperventilation attacksSudden severe headache (ICH), focal deficits, SAH, cognitive decline
TriggerHyperventilation (crying, blowing, wind instrument), fever, exerciseValsalva, BP surge, anticoagulation

Diagnostic Imaging: The Golden Standard

  1. MRA (MR Angiography): Non-invasive screening. Shows "ivy sign" (leptomeningeal collaterals).
  2. CTA: Excellent bony detail, faster.
  3. Digital Subtraction Angiography (DSA): Gold standard. Defines Suzuki Stages (1-6): narrowing → initiation of collaterals → intensification → peak → reduction → disappearance of main trunks. Essential for surgical planning.
  4. Perfusion Imaging (CTP/MRP/ASL/SPECT): Quantifies hemodynamic compromise (Tmax, MTT, CBF) — guides surgical candidacy.

Treatment: Revascularization is Disease-Modifying

Surgical (Definitive)

  • Direct Bypass (STA-MCA): Superficial temporal artery → middle cerebral artery. Immediate flow. Technically demanding in small children (<3-5 kg vessels). Preferred for adults/older children.
  • Indirect Bypass (EDAS, EMS, Pial Synangiosis): Vascularized tissue (temporal muscle, dura, galea) placed on brain surface → angiogenesis over 3-6 months. Better for young children, small vessels. Often combined.
  • Combined (Direct + Indirect): Increasingly standard for hemodynamic reserve.

Medical (Adjunctive)

  • Antiplatelet (Aspirin) — lifelong, reduces TIA/stroke risk.
  • Strict BP control (avoid hypotension → watershed infarcts; avoid hypertension → hemorrhage).
  • Calcium channel blockers (vasospasm prophylaxis).
  • Seizure management (ASMs).

Prognosis & Surveillance

  • With Surgery: 5-yr stroke-free survival >90% (pediatric), 80-85% (adult). Hemorrhage risk reduced but not eliminated.
  • Without Surgery: High recurrent stroke/ICH risk. Natural history: progressive.
  • Lifelong Follow-Up: Annual MRA/MRI/perfusion. Monitor collaterals, graft patency, new stenosis.

Moyamoya is a surgical disease. Early diagnosis by a cerebrovascular neurosurgeon at a high-volume center changes the trajectory from inevitable decline to stabilized, productive life.

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