Moyamoya disease is a rare disorder caused by the narrowing of the carotid arteries feeding the brain. This disease reduces the blood flow in the arteries that bring blood from the carotid artery to the brain. These arteries are MCA and ACA. Posterior cerebral arteries that receive blood from the Vertebero Basilar artery remain intact. Moyamoya disease is more common in Japan, Korea and China. Researchers believe that the higher prevalence of this disease in these Asian countries is due to the existence of a genetic factor; But the main cause of this disease is still not known.