This respiratory illness season, wearing a mask is required in patient and resident areas at Sunnybrook. Read our visitor guidelines »

Research A-Z

Moyamoya disease

Definition

Moyamoya disease is a rare, progressive cardiovascular condition in which the walls of the carotid arteries thicken and the arteries narrow, restricting or blocking blood flow to the brain. "Moyamoya" means "puff of smoke" in Japanese; it describes the look of the tangle of tiny blood vessels that form to compensate for the blockage.