What is moyamoya syndrome?

Moyamoya syndrome is a disorder that causes certain arteries in the brain to constrict (tighten or shrink) and thicken. The arteries affected are called internal carotid arteries. They help carry blood to the brain. The constricted blood vessels can put a person at a higher risk for a stroke (when blood supply to the brain is interrupted by a blockage or blood flow issue).

Moyamoya syndrome is 3 times more common in people with Down syndrome than people without Down syndrome. Doctors do not know why people with Down syndrome have a higher risk of developing moyamoya syndrome.

Rev. 7/2019. Created by Jonathan Santoro, MD. MassGeneral Hospital for Children and Massachusetts General Hospital do not endorse any of the brands listed on this webpage. This webpage is intended to provide health information so that you can be better informed. It is not a substitute for medical advice and should not be used to treatment of any medical conditions.