Moyamoya Disease


What is moyamoya disease?

Moyamoya disease affects the blood vessels in the brain, making it a cerebrovascular disease. It happens when at least one carotid artery — and sometimes both — narrows or closes. Additionally, the anterior and/or middle cerebral arteries can be blocked also. These key arteries deliver blood and oxygen to the front 2/3rd of the brain. When these arteries get blocked over time, certain chemicals are released within the brain which tell the brain to form new blood vessels to make up for the blood and oxygen that was lost from the blockage. However, since these blood vessels are formed as emergency back-up vessels, they are smaller and often weaker than the artery that blocked. Therefore, these smaller back-up arteries are more fragile and are often insufficient to supply enough blood to the brain. This may lead to brain bleeds and strokes in affected areas of the brain.

What does the name moyamoya mean?

“Moyamoya” is a Japanese word that means “puff of smoke.” Japanese doctors discovered that when they did blood vessel scans called angiograms in operating rooms on these patients, the smaller, formed back-up vessels looked like a curled up “puff of smoke” when iodine contrast was injected into their blood vessels. Therefore, they used the term “moyamoya disease” to describe it.

Who gets moyamoya disease?

Moyamoya disease is rare, and although the genetic forms occur mostly in patients of Asian ancestry, it is now being seen more and more in patients from other ethnic background including Caucasians, Hispanics and African Americans.

For reasons that scientists don’t understand, moyamoya disease is two times more common in females than in males.

There are two age ranges when moyamoya occurs more often: around 5 to 10 years old and between 30 and 50 years old. But it can happen at any age.

Symptoms and Causes

What causes moyamoya disease?

The exact cause of moyamoya disease remains unknown. However, there appear to be genetic and acquired forms. Researchers are still exploring genes that could possibly get passed down from parents.

Sometimes moyamoya disease occurs with other conditions and is called moymoya syndrome or phenomenon. Examples of these other conditions include:

What are the symptoms of moyamoya disease?

The first sign of moyamoya disease is often stroke or repeated transient ischemic attacks (TIAs). Providers call these “mini-strokes.” Other symptoms may include:

  • Brain hemorrhage (bleeding).
  • Headaches.
  • Developmental delays.
  • Aneurysm (bulging or ballooning of a blood vessel, which can break).
  • Involuntary movements (when your body parts move without your control).
  • Problems with cognitive abilities (such as learning, remembering and paying attention).
  • Problems with the senses (sight, hearing, smell, touch, taste).
  • Seizures.

Diagnosis and Tests

How is moyamoya disease diagnosed?

If a healthcare provider suspects moyamoya disease, you may need the following tests:

  • Cerebral arteriography: A small tube called a catheter gets inserted in an artery in your arm or leg. Iodine contrast dye is then injected into your bloodstream. X-ray scans are then taken of the dye in your blood vessels. This technique can reveal how much your blood vessels have narrowed and map blood flow patterns.
  • Magnetic resonance angiography (MRA): This pain-free test uses a magnetic field, radio waves and a computer to look inside your blood vessels for any unusual features.
  • Magnetic resonance imaging (MRI): MRI uses similar technology to take pictures inside the body and detect what the blood flow looks like in your brain.

Management and Treatment

Is there a cure for moyamoya disease?

There is no cure for moyamoya disease, but it's treatable.

What are the treatments for moyamoya disease?

If you’re diagnosed with moyamoya disease, your healthcare provider may suggest certain medications:

  • Aspirin: Aspirin can help prevent blood clots in the small blood vessels that were formed as back-up.
  • Anticonvulsants: These medications can prevent seizures caused by moyamoya disease.
  • Anticoagulants: Anticoagulants can thin the blood to prevent blood clots. But these drugs have risks, such as possible bleeding that’s difficult to stop. They’re only prescribed in certain cases.
  • Calcium channel blockers: Calcium channel blockers can lessen headaches from moyamoya disease. But these drugs can also lower blood pressure, potentially increasing stroke risk. They’re only used in certain cases.

Medications can’t stop blood vessels from narrowing, so moyamoya disease may continue to grow worse. Your healthcare provider may then consider surgery in the form of a bypass that:

  • Bypasses blocked arteries by using normal scalp arteries as donor arteries.
  • Diverts blood flow (changes its direction) to the affected areas
  • Opens narrow blood vessels.


Can I prevent moyamoya disease?

In cases of genetic forms of moyamoya disease, nothing definitive has been proven to prevent moyamoya disease. However, moyamoya syndrome can be prevented by vascular risk factor control and reducing your risk of atherosclerosis.

You may be able to relieve symptoms and avoid complications from moyamoya disease if you make sure you take your medications exactly as directed.

Outlook / Prognosis

What is the outlook for people with moyamoya disease?

Most people with moyamoya disease worsen over time. They may also experience strokes as blood vessels narrow more and more. Without treatment, it can lead to stroke with severe neurological deficits. However, some patients are able to remain stable for years without symptoms. Once symptoms start to develop, your provider may suggest that a bypass surgery is needed.

Living With

When should I get emergency medical help if I have moyamoya disease?

Get immediate medical attention if you experience any signs of a stroke.

The American Stroke Association uses the acronym F.A.S.T. to help people remember how to react:

  • Face droop: Does one side of your face feel numb? If you try to smile, does one side of your face droop?
  • Arm weakness: Can you raise both arms? Does one arm drift lower?
  • Speech: Is your speech slurred or slow? Can you repeat a simple phrase?
  • Time: For any signs of stroke, call 911 or get emergency medical help immediately. Time is critical.

Other symptoms of stroke include sudden:

  • Confusion.
  • Numbness on one side of the body
  • Trouble seeing.
  • Trouble walking.
  • Severe headache.

A note from Cleveland Clinic

Moyamoya disease is a rare condition that can lead to ischemic strokes and brain bleeds. Talk to your healthcare provider if you’re having any recurring of the symptoms mentioned above. Learn how to recognize the signs of stroke, which need immediate medical attention.

Last reviewed by a Cleveland Clinic medical professional on 05/06/2021.


  • American Stroke Association. Stroke Symptoms. ( Accessed 5/11/2021.
  • National Institute of Neurological Disorders and Stroke. Moyamoya Disease Information Page. ( Accessed 5/11/2021.
  • National Organization for Rare Disorders. Moyamoya Disease. ( Accessed 5/11/2021.
  • U.S. National Library of Medicine. Moyamoya Disease. ( Accessed 5/11/2021.

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy