Moyamoya Disease

Moyamoya disease is a type of cerebrovascular disease — a condition that affects the blood vessels in your brain. In moyamoya disease, at least one of your carotid arteries — and sometimes both — narrow or close. It also affects your front and/or middle cerebral arteries. These key arteries deliver blood and oxygen to the front two-thirds of your brain. When these blood vessels narrow, it blocks blood flow to your brain.

Over time, your brain forms new blood vessels to make up for the blood and oxygen lost from the blockage. But as these blood vessels are formed as emergency backup vessels, they’re smaller and often weaker than the blocked arteries. These smaller, backup arteries often can’t supply enough blood to your brain. This may lead to brain bleeds and stroke in the affected areas of your brain.

What does moyamoya mean?

“Moyamoya” is a Japanese word that means “puff of smoke.” Japanese doctors discovered that the smaller backup vessels looked like curled-up puffs of smoke when they did blood vessel scans called angiograms. That’s why they used the term “moyamoya disease” to describe the condition.

How rare is moyamoya disease?

Moyamoya disease is most common in Japan, where it affects about 5 in every 100,000 people. In the United States, the condition affects fewer than 5,000 people.