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Moyamoya is a rare disorder that causes major blood vessels leading to a child's brain to narrow. If untreated, the vessels become blocked and cause a stroke or recurring mini-strokes called transient ischemic attacks (TIA). In adults, it causes bleeding in the brain or hemorrhagic strokes.

Moyamoya, first described in Japan in the 1960s, means "puff of smoke" in Japanese, named after the abnormal appearance of new blood vessels that grow to make up for the blocked artery. Although the cause is unknown, Japanese and Korean children and those with other disorders such as Down's syndrome, neurofibromatosis and tuberous sclerosis are more frequently affected.

Several types of surgery can restore blood flow to the brain. The UCSF Pediatric Stroke and Cerebrovascular Disease Center specializes in these treatments. Without treatment, the disease can be fatal.

Signs & symptoms

Children, adolescents and young adults are typically affected by moyamoya, although the condition can occur in older adults. Symptoms include:

  • Stroke
  • Recurrent transient ischemic attacks (TIAs) or mini-strokes, in which the blood supply to the brain becomes blocked. This prevents oxygen and nutrients from reaching brain cells.
  • 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


Your child first will have a thorough physical examination. If your child’s doctor suspects moyamoya, he or she will recommend a test called a cerebral angiography.

During this procedure, an X-ray is taken to examine the brain's arteries. First, dye is injected into the arteries to make them easier to see on the X-ray. Doctors look for the narrowed artery and the growth of new, smaller arteries that develop to compensate for the blockage.


Currently, there is no cure for moyamoya. Children who suffer from strokes and recurrent transient ischemic attacks are given aspirin and other medications to reduce the risk of future attacks.

In addition, there are several types of surgery to treat moyamoya by bypassing areas of blockage. Our neurosurgeons perform two general types of surgery for moyamoya:

  • Indirect Bypass or Encephaloduroarteriosynangiosis (EDAS) Bypass — During this procedure, the neurosurgeon uses an artery that normally goes to the scalp. 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, called collaterals that feed blood to the brain.
  • Direct Bypass or External Carotid to Internal Carotid Artery (EC-IC) Bypass — During this procedure, the neurosurgeon also uses a blood vessel to the scalp. Instead of just laying it on top of the brain, the surgeon directly connects it to one of the existing blood vessels in the brain. This procedure is more invasive than the indirect bypass, but it immediately restores blood flow.

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

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