Moyamoya Disease

Moyamoya disease is an unusual precipitant of stroke, caused by abnormal growth along the inner walls of blood vessels in the brain. The growth occurs in certain segments of vessels, creating discrete areas of narrowing that progressively limit bloodflow. Moyamoya progresses slowly, giving the oxygen-starved brain enough time to generate new blood vessels around the areas of narrowing.

When one performs an angiogram to visualize blood vessels in the brain, the newly generated blood vessels appear as a puff of smoke around the areas of narrowing. This peculiar appearance gives the disease the name moyamoya, because in Japanese this term means "puff of smoke" (moyamoya disease has a high prevalence in Japan).

Although moyamoya can occur spontaneously, it can also occur in the context of sickle cell anemia and other diseases.