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Moyamoya disease
Moyamoya is progressive narrowing of the terminal internal carotid artery and its first branches with a network of fine "puff of smoke" vessels — in children it presents with ischaemic events triggered by crying or hyperventilation, and in adults often with haemorrhage; treatment is revascularisation surgery.
Why it matters in the exam
The exam asks about the associations of "moyamoya syndrome" (when there is an underlying disease): Down syndrome, NF1, sickle cell disease, previous cranial irradiation, Graves disease and Williams syndrome. The primary form is linked to the RNF213 gene, is commoner in East Asia, and has two age peaks — childhood and the fourth decade. Diagnosis is usually by angiography (the gold standard), which shows terminal carotid narrowing and collaterals; Suzuki grades progression in six stages. On MRI the "ivy sign" may be seen — increased FLAIR signal in the sulci from slow flow in pial vessels.
The physiological danger is reduced cerebral blood flow: hyperventilation lowers carbon dioxide and causes vasoconstriction — so crying in a child or blowing into a wind instrument triggers an ischaemic event, and under anaesthesia hypocapnia and hypotension are avoided. Surgical treatment: direct bypass — connecting the superficial temporal artery to a middle cerebral artery branch (STA-MCA) — suits mainly adults; indirect bypass — laying vascular-rich tissue on the brain (EDAS, EMS, pial synangiosis) — suits mainly children, in whom new vessels form easily. The JAM trial showed that direct bypass reduces rebleeding in adults with haemorrhagic moyamoya. Aspirin is usually given to prevent ischaemic events. After surgery it is important to maintain fluids, normal blood pressure and normocapnia, because the perioperative period carries a high stroke risk, and the improvement in flow appears only after weeks to months.
Key points
- Narrowing of the terminal internal carotid with "puff of smoke" collaterals.
- Children — ischaemia on crying; adults — haemorrhage.
- Associations: Down, NF1, sickle cell, irradiation, Graves.
- Children — indirect bypass; adults — direct STA-MCA.
- Avoid hypocapnia under anaesthesia.
Summary table
| Aspect | Children | Adults | Note |
|---|---|---|---|
| Presentation | TIA and ischaemic stroke, triggered by crying | Intracerebral or intraventricular haemorrhage | Two age peaks |
| Preferred bypass | Indirect (EDAS, pial synangiosis) | Direct STA-MCA | JAM: less rebleeding |
| Associations | Down, NF1, sickle cell, irradiation | Graves, atherosclerosis | Moyamoya syndrome |
| Anaesthesia | Avoid hypocapnia | Maintain blood pressure | Low carbon dioxide constricts vessels |
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Sources
- AHA/ASA Scientific Statement: Moyamoya disease and moyamoya syndrome, 2008 — Diagnosis and revascularisation
- Japanese guidelines for the management of moyamoya disease, 2021 — Diagnostic criteria and surgical indications
- Japan Adult Moyamoya (JAM) trial, 2014 — Direct bypass for haemorrhagic moyamoya
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.