Genetic and Rare Diseases Information Center (GARD)


Other names people use for this condition
  • MYMY1
  • Spontaneous occlusion of the circle of Willis
  • Moyamoya disease
  • MYMY

Moyamoya disease 1
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Moyamoya disease is a rare condition in which the walls of the internal carotid arteries - which supply blood to important areas of the brain - become thickened.  The thickened arteries slow blood flow to the brain and increase the likelihood of blood clot formation, both of which can lead to strokes and transient ischemic attacks (TIA).  A tangle of tiny blood vessels form at the base of the brain that are possibly trying to supply oxygen to the areas of the brain that were once served by the narrowed arteries.  These tiny blood vessels - seen on an cerebral angiogram - look like a "puff of smoke"; or in Japanese, a "moyamoya".   The arteries in this tangle are fragile and can break and bleed into the brain, causing hemorrhages.    There are several types of revascularization surgery that can restore blood flow to the brain by opening narrowed blood vessels or by bypassing blocked arteries.  Many individuals are stroke free after surgery.  Prompt diagnosis and management is crucial to improve the long term outcome.  About 15% of patients with Moyamoya disease have a familial form. 


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