Moyamoya disease is an acquired abnormality of the carotid arteries, blood vessels that supply the front part of the brain.
The carotid arteries constrict down to a tiny size that is inadequate to maintain blood flow to the brain, or they can become completely occluded. To attempt to compensate for the lack of blood flow from the carotids, new small arteries grow in an abnormal pattern along the base of the brain. The new arteries are quite small on angiography (a blood vessel xray study), and appear similar to a "puff of smoke," which is what the term moyamoya means in Japanese. Momamoya disease was first described in Japan.
Children with moyamoya disease can develop stroke-like symptoms. To minimize loss of neurological function, surgery is recommended for some children. The goal of the surgery is to use blood vessels from the scalp (the superficial temporal arteries) to establish new blood flow for the brain. This procedure is called pial synangiosis, and can be effective in brain revascularization.