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Moyamoya Disease

What is moyamoya disease?

Moyamoya disease is a rare, progressive blood vessel (vascular) disorder where the carotid artery in your skull becomes blocked or narrowed. This reduces the blood flow to your brain and results in temporary or permanent brain injury.

The condition may cause a mini stroke (called a TIA), stroke, bulge or ballooning in a blood vessel (aneurysm) or bleeding in the brain. It can also affect how well your brain functions and cause cognitive and developmental delays or disability.

What causes moyamoya disease?

Though the cause of moyamoya disease is unknown, certain factors have been shown to increase your risk of having the condition, including:

  • Females have a slightly higher incidence of moyamoya disease.
  • Though adults can have moyamoya disease, children younger than 15 years old are most commonly affected.
  • If you have a family member with moyamoya disease, your risk of having the condition is 30 to 40 times higher than the general population — a factor that strongly suggests a genetic component to the disease and may justify screening of family members.
  • Moyamoya disease is found all over the world, but it's more common in East Asian countries, and among Asians living in western countries. This may possibly be due to certain genetic factors in those populations.
  • Moyamoya disease sometimes occurs in association with another disorder, such as sickle cell anemia, Down syndrome and neurofibromatosis type 1, among others.

What are the symptoms of moyamoya disease?

While moyamoya disease may occur at any age, symptoms most commonly occur in children between 5 and 10 years of age and in adults between 30 and 50 years of age.

The first symptom of moyamoya disease is usually stroke or recurrent mini strokes (TIAs), especially in children. Adults may also experience these symptoms but more often experience bleeding in the brain (hemorrhagic stroke) from abnormal brain vessels.

Signs and symptoms of moyamoya disease include:

  • Weakness, numbness or paralysis in your face, arm or leg, typically on one side of your body
  • Visual disturbances
  • Headache
  • Seizures
  • Cognitive decline
  • Difficulties with speaking or understanding others (aphasia)
  • Developmental delays
  • Involuntary movements

Often these symptoms can be triggered by crying, coughing, exercise, straining or fever.

How is moyamoya disease diagnosed?

In most patients, the diagnosis of moyamoya can be made from a careful assessment of an MRI and MRA.

Cerebral arteriography will confirm the diagnosis, establish the exact degree of blood vessel narrowing, demonstrate the existing blood flow patterns to various areas of the brain, and allow treatment decisions to be made; for these reasons, it is the standard diagnostic tool for this condition.

In particular, catheter angiography can help with the identification of important blood vessels called “transdural collaterals,” which are present in some cases and can markedly influence surgical planning and prognosis.

What are the treatment options for moyamoya disease?

Our neurosurgeons treat moyamoya disease using sophisticated surgical techniques, including direct and indirect revascularization procedures. Types of indirect revascularization procedures include encephalomyosynangiosis (EMS), encephaloduroarteriosynangiosis (EDAS) or a combination of both.

These operations involve the placement of vascularized structures from the scalp and/or the membranes that surround the brain onto the brain surface, which in most moyamoya patients will induce the growth of new blood vessels into the brain.

The most common direct procedure involves the direct suturing of a scalp blood vessel, the superficial temporal artery, to a middle cerebral artery branch on the brain surface.

Long-term results following surgery of either type have been quite good, with long-term prevention of strokes seen in published series of both pediatric and adult patients.

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