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Moyamoya Syndrome

Summary

  • Moyamoya disease (primary/idiopathic) and syndrome (secondary) represent rare cerebrovascular disorders characterised by progressive stenosis of intracranial internal carotid arteries and their proximal branches
  • Results in formation of abnormal collateral vessels at the base of the brain
  • Presents with ischaemic or haemorrhagic stroke, seizures, and cognitive decline1

Pathophysiology

  • Progressive narrowing of the internal carotid arteries and proximal cerebral arteries
  • Compensatory development of fragile, dilated collateral vessels (moyamoya vessels)
  • Exact cause unknown, but genetic factors and inflammatory processes implicated
  • Associated with various conditions, including Down syndrome, neurofibromatosis type 1, and sickle cell disease

Demographics

  • Bimodal age distribution: peaks in childhood (5-10 years) and adulthood (30-50 years)
  • Higher prevalence in East Asian populations, particularly Japan
  • Female-to-male ratio of approximately 2:1
  • Familial occurrence in 10-15% of cases

Diagnosis

  • Based on clinical presentation and imaging findings
  • Diagnostic criteria include:
    1. Stenosis or occlusion of terminal internal carotid artery and/or proximal cerebral arteries
    2. Abnormal vascular network near the stenotic lesions
    3. Bilateral involvement (can be unilateral in early stages)
  • Suzuki staging system used to classify disease progression (6 stages)

Imaging

  • Digital Subtraction Angiography (DSA):
    • Gold standard for diagnosis
    • Demonstrates stenosis/occlusion of major intracranial arteries
    • Shows characteristic "puff of smoke" appearance of collateral vessels
  • Magnetic Resonance Angiography (MRA):
    • Non-invasive alternative to DSA
    • Visualises stenosis and collateral vessels
    • May underestimate the extent of collaterals compared to DSA
  • Computed Tomography Angiography (CTA):
    • Useful for evaluating vessel stenosis and collateral formation
    • Less sensitive than DSA for detecting small collateral vessels
  • Perfusion imaging (CT or MRI):
    • Assesses cerebral blood flow and identifies areas of hypoperfusion
    • Helps in treatment planning and monitoring

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  • Patient presented with acute left sided weakness.
  • The initial MRI showed acute infarcts in the superficial and deep borderzones of the right MCA.
  • MRA showed an occlusive vasculopathy of the terminal ICAs and proximal MCAs with many basal and cortical (mainly PCA) collaterals.
  • Vessel wall imaging showed concentric enhancement of the right terminal ICA and A1 ACA.

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  • 50-year-old patient with repeated transient ischaemic attacks localising to the left cerebral hemisphere.
  • There was a severe stenosis in the left MCA and a moderate short segment stenosis in the right MCA.
  • Associated with the severe left MCA stenoses, there was concentric enhancement that persisted for at least 2 years.

Treatment

  • Antiplatelet therapy and surgical revascularisation (direct STA-MCA bypass or indirect synangiosis) for haemodynamic compromise or recurrent ischaemia

Differential diagnosis

Differential Diagnosis Distinguishing Feature
Atherosclerotic intracranial stenosis Typically affects older patients; risk factors like hypertension and hyperlipidaemia present
Vasculitis Systemic symptoms often present; irregular vessel narrowing on angiography
Fibromuscular dysplasia Typically affects renal and carotid arteries; "string of beads" appearance on angiography
Radiation-induced vasculopathy History of cranial radiation therapy

  1. Scott et al. Moyamoya disease and moyamoya syndrome. 2009. The New England journal of medicine - Open in new tab. ↩