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Moyamoya Disease

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What is moyamoya disease?

Moyamoya disease is a rare disorder in which the internal carotid arteries – blood vessels that carry oxygen-rich blood to the brain – narrow over time. If left untreated, the vessels can become blocked and cause a stroke or recurring "mini-strokes" called transient ischemic attacks (TIAs). In adults, moyamoya can cause hemorrhagic strokes (bleeding in the brain).

The disease was first described in Japan and gets its name, which translates to "puff of smoke," from its appearance on imaging exams. To compensate for the blocked vessels, the body creates networks of small blood vessels, which resemble puffs of smoke when viewed on an angiogram. These new blood vessels are fragile and therefore susceptible to bulging or breaking open.

Moyamoya disease typically affects children, teenagers and young adults, although it can also occur in older adults.

Causes and risk factors for moyamoya disease

The cause of moyamoya disease is unknown, but the condition can run in families and genetics are thought to play a role. Worldwide, moyamoya disease occurs more frequently in children of Japanese and Korean descent. Females are more likely to have it than males.

Children with certain disorders – such as Down syndrome, neurofibromatosis, tuberous sclerosis complex and sickle cell disease – are also affected more frequently. In these cases (when the patient also has an associated disorder), the condition is called moyamoya syndrome.

Symptoms of moyamoya disease

Symptoms of moyamoya include:

  • Strokes
  • Recurrent transient ischemic attacks (TIAs)
  • Muscle weakness or paralysis that affects one side of the body, also known as hemiparesis
  • Seizures
  • Speech problems
  • Sensory and cognitive impairments
  • Involuntary movements
  • Vision problems

Diagnosis of moyamoya disease

Your child will have a thorough physical exam with a pediatric neurologist. If moyamoya is suspected, the doctor will recommend a cerebral angiogram, which shows how blood is flowing through the brain. The doctor will look for the narrowed arteries and new, small blood vessels that characterize moyamoya.

Treatment of moyamoya disease

Although there's no cure for moyamoya disease, there are treatment options. Children who experience strokes and recurrent TIAs can take aspirin and other medications to reduce the risk of future events. There are also several types of surgery used to treat moyamoya by creating a bypass for the blocked areas.

Our pediatric neurosurgeons offer two procedures for moyamoya:

  • Indirect bypass, or encephaloduroarteriosynangiosis (EDAS) bypass. The pediatric neurosurgeon uses an artery that normally carries blood to the scalp to reestablish blood flow to the brain. After making a small hole in the skull, the surgeon lays the artery on the surface of the brain. Over time, this artery sprouts branches that deliver blood to the brain.
  • Direct bypass, or extracranial-intracranial (EC-IC) bypass. As with indirect bypass, the neurosurgeon uses a blood vessel that supplies the scalp. Instead of laying it on top of the brain, however, the surgeon directly connects it to one of the brain's existing blood vessels. This procedure is more invasive than indirect bypass, but it restores blood flow immediately.

UCSF Benioff Children's Hospitals medical specialists have reviewed this information. It is for educational purposes only and is not intended to replace the advice of your child's doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your child's provider.

Where to get care (1)

Cerebrovascular & Stroke Program

Cerebrovascular & Stroke Program

1825 Fourth St., Fifth Floor, 5A
San Francisco, CA 94158

Awards & recognition

  • One of the nation's best in neurology & neurosurgery

  • in NIH funding among U.S. neurology programs

  • Ranked among the nation's best in 10 specialties

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