Moyamoya disease
Moyamoya disease is a cerebral vasculopathy in which large intracranial arteries become stenotic or occluded and irregular networks of perforating collateral vessels form in the lenticulostriate and thalamoperforating territory, causing ischemic stroke and, in the third and fourth decades, intracerebral hemorrhage. It is confirmed by MRA, CTA, or catheter angiography, and sickle cell disease is its best-recognized association.
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What this article covers
- Overview
Definition: moyamoya disease is a cerebral vasculopathy in which large intracranial arteries become stenotic or occluded and irregular networks of perforating collateral vessels develop near the…
- Epidemiology
Sickle cell disease is the best-recognized setting: about 30% of patients with Hb SS, Hb SC, or sickle-beta-plus thalassemia have silent or symptomatic strokes, and in addition to thrombotic stroke some patients develop moyamoya.
- Risk factors
Sickle cell disease with a severe phenotype: Hb SS and sickle-beta-zero thalassemia carry the highest stroke risk, with high transcranial Doppler velocities marking the patients at greatest risk.
- Pathophysiology
Progressive large-artery narrowing: in sickle cell disease, repeated vaso-occlusion produces intimal proliferation and stenosis of the large intracranial arteries.
- Clinical features
Ischemic stroke or TIA: sudden focal weakness, hemiparesis, aphasia, seizures, or altered mental status in a child or young adult, often without hypertension, diabetes, or smoking.
- Differential diagnosis
Intracranial atherosclerotic stenosis: older patients with hypertension, diabetes, dyslipidemia, or smoking, with plaque at the intracranial carotid, middle cerebral, or vertebrobasilar arteries and no perforating collateral network.
- Diagnosis
Established by vascular imaging: the diagnosis is confirmed when MRA, CTA, or catheter angiography shows stenosis or occlusion of the large intracranial arteries together with irregular networks of…
- Management
First, separate ischemia from hemorrhage with noncontrast CT, because the two presentations are treated in opposite directions.
- Complications
Recurrent ischemic stroke: progressive stenosis leaves downstream brain vulnerable, and recurrence is high without transfusion in sickle cell disease.
- Prognosis
Recurrence is modifiable in sickle cell disease: monthly transfusion after a first stroke reduces subsequent stroke by about 50%.
- Prevention
Screen children with severe sickle cell disease: transcranial Doppler ultrasound annually beginning at age 2 in Hb SS and sickle-beta-zero thalassemia; a high velocity mandates chronic transfusion.
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