Moyamoya Disease

Moyamoya disease is a rare condition that affects the blood vessels in your brain. It can lead to brain bleeds and strokes in affected areas of your brain. There’s no cure for moyamoya disease. Treatment typically involves managing symptoms and preventing blood clots with medications. You may also need surgical bypass to supply more arteries to your brain for adequate blood flow.


What is moyamoya disease?

Moyamoya disease affects the blood vessels in your brain. It's a cerebrovascular disease. In moyamoya disease, at least one carotid artery — and sometimes both — narrows or closes. Additionally, the front and/or middle cerebral arteries can be blocked. These key arteries deliver blood and oxygen to the front two-thirds of your brain. Over time, your brain forms new blood vessels to make up for the blood and oxygen lost from the blockage. But since these blood vessels are formed as emergency backup vessels, they're smaller and often weaker than the blocked artery. These smaller, backup arteries often can't supply enough blood to your brain. This may lead to brain bleeds and strokes in affected areas of your brain.


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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 backup vessels looked like a curled up “puff of smoke” when they injected iodine contrast into their blood vessels. That's why they used the term “moyamoya disease” to describe it.

Who gets moyamoya disease?

Moyamoya disease is rare. Although the genetic forms occur mostly in patients of Asian ancestry, healthcare providers see it more and more in patients from other ethnic backgrounds.

For reasons that scientists don’t understand, moyamoya disease is two times more common in people assigned female at birth than in people assigned male at birth.

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. But 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 moyamoya 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 burst).
  • Involuntary movements (when your body parts move without your control).
  • Problems with cognitive abilities (like learning, remembering and paying attention).
  • Problems with your 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: Your provider inserts a small tube called a catheter into an artery in your arm or leg. They then use it to inject iodine contrast dye into your bloodstream. Next, they take X-ray scans 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): In this pain-free test, your provider 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 your body and detect what the blood flow looks like in your brain.

Management and Treatment

Is there a cure for moyamoya disease?

There's 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 smaller, backup blood vessels.
  • Anticonvulsants: These medications can prevent seizures caused by moyamoya disease.
  • Anticoagulants: Anticoagulants can thin your blood to prevent blood clots. But these drugs have risks, like 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 worsen. Your healthcare provider may then consider bypass surgery 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?

There's no proven way to prevent genetic forms of moyamoya disease. But you can lower your risk of developing moyamoya syndrome by controlling vascular risk factors 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?

For most people with moyamoya disease, the condition gets worse over time. They may also experience strokes as blood vessels narrow more and more. Without treatment, moyamoya disease can lead to stroke with severe neurological deficits. However, some patients remain stable for years without symptoms. Once symptoms start to develop, your provider may suggest bypass surgery.

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 your 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 of the symptoms mentioned above. Learn how to recognize the signs of stroke, which need immediate medical attention.

Medically Reviewed

Last reviewed on 05/06/2021.

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