Moyamoya disease is a rare but very serious condition in which one or both of the internal carotid arteries (located in the front of the neck) become narrower over time. This causes blood flow to slow down, increasing a child’s risk of developing a blood clot. Tiny blood vessels form around the blocked artery as the body attempts to restore normal blood flow. The Japanese word “moyamoya” means “puff of smoke” − which is what the tiny blood vessels look like on an imaging test.
If left untreated, Moyamoya disease can cause multiple strokes leaving brief or permanent weakness or mental decline.
Moyamoya syndrome is a rare occurrence in which Moyamoya disease and another related condition are present. Some of these related conditions include Down syndrome, Alagille, PHACE, neurofibromatosis, cancer and sickle cell disease. Radiation therapy also can induce Moyamoya disease.