Moyamoya Disease

Moyamoya disease is a rare cerebrovascular disorder in which certain arteries at the base of the brain become progressively constricted, blocking blood flow through narrowing and blood clots. To compensate, the brain grows a network of small, fragile collateral vessels around the blockages, vessels that are themselves prone to bleeding, aneurysm, and further clotting. On conventional angiography this collateral network has a hazy, cloud-like appearance, which is why the disease takes its name from the Japanese word moyamoya, meaning puff of smoke.