Circle of Willis
  • A cerebrovascular disease characterized by progressive stenosis/occlusion of the arteries around the Circle of Willis.
  • The narrowing or blockage stimulates angiogenesis to provide collateral circulation to the brain.
  • On angiography, these small blood vessels give off a "puff of smoke" appearance (also known as "MoyaMoya" in Japanese).
  • The disease is found more commonly in Asian countries and was first descried in Japanese literature in 1957.
  • There is mounting evidence there is a genetic cause of the disease.

Clinical Features

  • The developed collateral circulation is prone to bleeding, aneurysm, thrombosis exhibiting: focal neurological deficits, TIA, epilepsy, and bowel/bladder incontinence.
  • Children predominately exhibit ischemic stroke.
  • Approximately 2/3rd of children exhibit Electroencephalography (EEG) abnormalities: high voltage slow waves that occur during hyperventilation.
  • Can be associated with atherosclerosis, meningitis, vasculitis, autoimmune diseases, hematological conditions, brain tumors, and chromosomal abnormalities

Differential Diagnosis


T1-weighted MR image of moyamoya disease. Flow void in the basal ganglia is indicated by the arrow.
Left: MIP reconstructed MR angiography of a 11-year-old girl with moyamoya disease. Right: healthy patient, for comparison.
  • Head CT and/or brain MRI are important studies to visualize infarctions and brain hemorrhages.
  • CT can show dilation of the sulci accompanies by focal ventricular enlargement.
  • MRI has higher sensitivity for detecting ischemic regions.
  • Magnetic Resonance Angiographic studies can demonstrate occlusions within the circle of Willis and better visualize the collateral vasculature. It is preferred over CTA in most institutions.


  • Symptomatic treatment: decrease elevated ICP, improve cerebral blood flow, control active seizures, pain control , supplemental O2
  • Avoid hypotension, hypervolemia, hypernatremia, hypocarbia
  • Ventricular drainage if there is hemorrhage
  • Minimize crying/hyperventilation a decreased PaCO2 can worsen ischemia by vasoconstriction
  • Antithrombotic and thrombolytic surgery has not been systematically analyzed for Moyamoya disease


  • Admit

See Also

External Links