What Is Moyamoya Disease?

Medically Reviewed by Neha Pathak, MD on December 29, 2022
4 min read

Moyamoya disease is a rare disease in which a blockage to the carotid artery in your head reduces how much blood can get to your brain. As a result, your body creates tiny blood vessels (called collaterals) in a desperate attempt to try to get blood to your brain. You may have strokes, ministrokes, or bleeding in the brain. It can also affect how your brain works. Moyamoya disease mostly affects children, though adults can get it, too.

In addition to strokes, ministrokes, and brain bleeding, moyamoya disease can impair your brain function. It can lead to disability as well as cognitive and developmental delays.

Though the collateral blood vessels may help in the short term, they eventually stop working. Without treatment, moyamoya disease can be fatal -- but there are ways to treat it.

Moyamoya disease was first discovered in Japan. Though anyone can get it, it’s more common in Asian countries compared to countries in North America or Europe. That may be due to genetic traits in populations in Asia. Still, only about 10% of cases in Asian people are from a genetic link. (This suggests there are other causes.)

The term “moyamoya” in Japanese means “puff of smoke.” It refers to how the collateral vessels look when they form.


Scientists aren’t quite sure. These factors may increase your chances of developing moyamoya disease:

Genetics. Some people with it may have a family member who is affected. Researchers have identified genetic mutations that are linked to the disease.

Existing health. People with other ailments likeneurofibromatosis type 1, sickle cell disease, Down syndrome, Graves disease, atherosclerosis, and radiation vasculopathy may be more likely to get it.

Sex. Females have higher chances of getting moyamoya disease.

Age. Moyamoya disease can occur at any age. It’s most common in kids between 5 and 15 years old. Adults can get it, too, but that’s less common. Those who do have moyamoya disease are often diagnosed between 30 and 50 years old.

There’s some research into earlier detection methods. A recently discovered urinary panel may be helpful in young people.


It’s important to know that the symptoms may vary depending on your age.

Symptoms can start gradually or suddenly. They may improve over time. They can persist.

Doctors often diagnose moyamoya disease in children after they have a stroke or ministrokes (those are also called recurring transient ischemic attacks). Adults often have a hemorrhagic stroke due to bleeding into the brain.

In addition to strokes, moyamoya disease symptoms can include:

  • Vision problems
  • Headaches
  • Interruptions in consciousness
  • Seizures
  • Involuntary movements
  • Cognitive and/or sensory impairment
  • Weakness, numbness, or paralysis -- usually on one side of your body
  • Difficulty speaking or understanding verbal communication
  • Aneurysm

In some cases, children with moyamoya disease will have a brain hemorrhage, which means bleeding in the brain.

Signs of a brain hemorrhage in kids can include:

  • Vision changes
  • Severe headache
  • Vomiting
  • Nausea
  • Fatigue and lethargy
  • Numbness in part of the body

A neurologist can diagnose moyamoya disease. They may use any of the following tests do to do:

Electroencephalogram (EEG). Your health care professional attaches electrodes on your scalp, then the machine looks at electrical activity on your brain. It’s noninvasive.

Transcranial Doppler ultrasound. This painless scan uses an ultrasound wand to give the doctor images of your head and neck, so they can see blood flowing in vessels.

Computerized tomography (CT). Your doctor injects a dye into a blood vessel to better view them, then takes multiple X-rays to form an in-depth image of your brain. It can help them see any blood vessel abnormalities.

Magnetic resonance imaging (MRI). Your doctor can use this machine with or without injecting dye into your body. The magnets and radio waves create an image of your brain and look at how much blood is moving through your vessels. (This lets them see how much blood your brain is getting, which is important to assess the severity moyamoya disease.)

Positron emission tomography (PET) or single-photon emission computerized tomography (SPECT). Your doctor injects a small amount of radioactive material into your body and you lie on a table that passes through a scanner. This lets them see your brain activity and measure blood flow.

Cerebral angiogram. Your doctor inserts a thin tube into a blood vessel in your groin area, then guides it up to your brain. Then they inject dye so they can use X-rays to see blood vessels.

Moyamoya disease treatmentcan involve taking medicines to lower your risk of stroke. You may get blood thinners, anti-seizure medications, or calcium channel blockers to lower your risk for stroke or manage seizures.

Revascularization surgery is also an option for some people. Surgeons can use a variety of techniques to restore blood flow. Kids may respond better to that than adults. In some cases, surgery can stop strokes from occurring.

Moyamoya disease often gets worse over time. But there are treatments that can help.


While it can cause permanent brain damage, some people can find relief from symptoms or stop strokes. You can treat moyamoya disease, though outcomes will vary depending on the person and the treatment used.

Because stroke can be the first symptom of moyamoya disease, it’s vital to know how to spot a potential stroke -- and to get emergency care if you suspect it. Timing is crucial. A person may be able to avoid long-term damage the sooner they get care.

Here’s how to tell if someone may be having a stroke:

  • One side of their face droops when they smile
  • Trouble raising both arms
  • Slurred speech
  • Confusion
  • Headache
  • Trouble seeing or walking