Overview

Moyamoya disease is a rare blood vessel (vascular) disorder in which the carotid artery in the skull becomes blocked or narrowed, reducing blood flow to your brain. Tiny blood vessels then develop at the base of the brain in an attempt to supply the brain with blood.

The condition may cause a ministroke (transient ischemic attack), stroke or bleeding in the brain. It can also affect how well your brain functions and cause cognitive and developmental delays or disability.

Moyamoya disease most commonly affects children, but adults may have the condition. Moyamoya disease is found all over the world, but it's more common in East Asian countries, especially Korea, Japan and China. This may possibly be due to certain genetic factors in those populations.