Moyamoya disease

Related Subjects: |Subarachnoid Haemorrhage |Haemorrhagic stroke

🌫️ Moyamoya disease is a progressive, non-inflammatory vasculopathy affecting the intracranial internal carotid arteries (ICA), middle cerebral arteries (MCA), and anterior cerebral arteries (ACA). It causes both ischaemic and haemorrhagic stroke. On angiography, a hazy network of collateral vessels forms, resembling "moyamoya" — the Japanese word for smoke drifting in the air. First described in 1957, the name was popularised by Jiro Suzuki in 1965 and later codified [Suzuki J, 1983].

📖 About

• Described in Japan in 1957 as “hypoplasia of the bilateral ICAs”; renamed “Moyamoya” in 1965.
• 🧮 Incidence: ~10/100,000 in Japan; ~1/1,000,000 in the USA.
• Involves progressive ICA occlusion and development of fragile collateral vessels.
• Increased basic fibroblast growth factor has been implicated in pathogenesis.
• Can be sporadic or familial, leading to both ischaemic and haemorrhagic stroke.

🧬 Genetics

• Most common in Japanese, Chinese, and Korean populations (10x more frequent than in Europeans).
• Familial clustering: linked to variants on chromosome 17 (e.g., RNF213 gene).
• Seen worldwide, including non-Asian cohorts.

⚙️ Aetiology & Pathophysiology

• Affects the distal ICA, MCA, and ACA stems.
• Results in extensive collateralisation via lenticulostriate, thalamic, and transdural anastomoses.
• Non-inflammatory; pathology shows intimal hyperplasia with lumen narrowing.
• Fragile collaterals predispose to haemorrhage.
• Similar angiographic patterns (“Moyamoya syndrome”) may occur with atherosclerosis, diabetes, or sickle cell disease.

🤝 Associations

• Haematological: Sickle cell disease, β-thalassaemia, hereditary spherocytosis, Fanconi anaemia.
• Neurological/genetic: Neurofibromatosis type 1.
• Metabolic/immune: Homocystinuria, antiphospholipid syndrome, Grave’s disease, SLE.

🩺 Clinical Presentation

• Common in children/young adults, but may present at any age.
• ⛔ Ischaemic events: recurrent hemiplegia, TIAs, cognitive impairment, silent infarcts.
• ⚡ Seizures and movement disorders (chorea, dystonia) may occur.
• 💥 Haemorrhage: intraparenchymal or intraventricular bleed from fragile collaterals.

🔍 Investigations

• 🧪 Bloods: Usually normal; confirms non-inflammatory nature.
• 🖼️ CT: Cortical/subcortical infarcts, volume loss, haemorrhage.
• 🧲 MRI/MRA: Gold standard → ICA narrowing + “puff of smoke” collaterals. FLAIR: “Ivy sign” from slow cortical flow. GRE: Detects microhaemorrhages in basal ganglia/thalamus.
• 📡 Transcranial Doppler: Non-invasive assessment of stenosis/hemodynamics.
• ⚡ EEG: In children → “re-build-up phenomenon” after hyperventilation.
• 🩻 Perfusion imaging: Identifies hypoperfused territories at risk of infarct.

📊 Suzuki Angiographic Stages

• 1️⃣ Early ICA stenosis.
• 2️⃣ Development of Moyamoya collaterals at brain base.
• 3️⃣ Progressive ICA occlusion; ↑ collateral vessels, ↓ MCA/ACA flow.
• 4️⃣ Circle of Willis + PCA occlusion; extracranial–intracranial collateralisation.
• 5️⃣ Fewer Moyamoya vessels; major arteries absent.
• 6️⃣ Disappearance of Moyamoya collaterals; brain perfused only by ECA branches.

⚖️ Management

• Best managed in specialist neurosurgical centres.
• 📉 Medical therapy: Limited role. BP optimisation crucial. Antiplatelets are sometimes used in children but avoided in adults due to haemorrhage risk.
• 🧑‍⚕️ Surgical revascularisation: - Direct bypass: STA–MCA anastomosis. - Indirect: Encephaloduroarteriosynangiosis (EDAS), burr holes, encephalomyosynangiosis (EMS). Recent studies show direct bypass reduces haemorrhagic risk most effectively.
• 💊 Aspirin often used in children; usually stopped in adults due to bleed risk.
• 📉 Most common cause of death: haemorrhage from fragile collaterals.

📖 Further Reading

• Moyamoya Disease and Syndrome — NEJM, 2009
• Treatment and Outcomes in Moyamoya — J Stroke, 2016
• EEG findings in childhood Moyamoya — Neurosurg Rev, 1992
• MRI vs CT perfusion in Moyamoya — Sichuan Univ J Med, 2018
• Multiple burr hole surgery — Acta Neurochir, 2018

💡 Exam Pearl: Moyamoya = young patient + recurrent TIAs/strokes + angiogram “puff of smoke.” Think early referral for surgical revascularisation to prevent ischaemia and haemorrhage.