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Moyamoya disease
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

Moyamoya disease

Moyamoya disease is a progressive disorder of the brain's blood vessels that restricts blood flow and can lead to stroke-like symptoms.

Overview

Moyamoya disease is a disorder of blood vessels in the brain, specifically the internal carotid arteries and the arteries that branch from them. These vessels, which provide oxygen-rich blood to the brain, narrow over time. Narrowing of these vessels reduces blood flow in the brain. In an attempt to compensate, new networks of small, fragile blood vessels form. These networks, visualized by a particular test called an angiogram, resemble puffs of smoke, which is how the condition got its name: "moyamoya" is an expression meaning "something hazy like a puff of smoke" in Japanese.

Moyamoya disease commonly begins either around age 5 or in a person's thirties or forties. A lack of blood supply to the brain leads to several symptoms of the disorder, including temporary stroke-like episodes (transient ischemic attacks), stroke, and seizures. In addition, the fragile blood vessels that grow can develop bulges (aneurysms), or they can break open, leading to bleeding (hemorrhage) in the brain. Affected individuals may develop recurrent headaches, involuntary jerking movements (chorea), or a decline in thinking ability. The symptoms of moyamoya disease often worsen over time if the condition is not treated.

Some people have the blood vessel changes characteristic of moyamoya disease in addition to features of another disorder, such as neurofibromatosis type 1, sickle cell disease, or Graves' disease. These individuals are said to have moyamoya syndrome.

Frequency

Moyamoya disease was first identified in Japan, where it is most prevalent, affecting about 5 in 100,000 individuals. The condition is also relatively common in other Asian populations. It is ten times less common in Europe. In the United States, Asian Americans are four times more commonly affected than whites. For unknown reasons, moyamoya disease occurs twice as often in females as in males.

Causes

The genetics of moyamoya disease are not well understood. Research suggests that the condition can be passed through families, and changes in one gene, RNF213, have been associated with the condition. Other genes that have not been identified may be involved in moyamoya disease. It is also likely that other factors (such as infection or inflammation) in combination with genetic factors play a role in the condition's development.

The RNF213 gene provides instructions for making a protein whose function is unknown. However, research suggests that the RNF213 protein is involved in the proper development of blood vessels.

Changes in the RNF213 gene involved in moyamoya disease replace single protein building blocks (amino acids) in the RNF213 protein. The effect of these changes on the function of the RNF213 protein is unknown, and researchers are unsure how the changes contribute to the narrowing of blood vessels or the characteristic blood vessel growth of moyamoya disease. For unknown reasons, people with moyamoya disease have elevated levels of proteins involved in cell and tissue growth, including the growth of blood vessels (angiogenesis). An excess of these proteins could account for the growth of new blood vessels characteristic of moyamoya disease. It is not clear if changes in the RNF213 gene are involved in the overproduction of these proteins.

Gene associated with Moyamoya disease

  • RNF213

Inheritance

Up to 15 percent of Japanese people with moyamoya disease have one or more family members with the condition, indicating that the condition can be passed through generations in families; however, the inheritance pattern is unknown. Research suggests that the condition follows an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. However, some people who have a copy of the altered gene never develop the condition, which is a situation known as reduced penetrance.

Other Names for This Condition

  • Cerebrovascular moyamoya disease
  • Moya-moya disease
  • Progressive intracranial arterial occlusion
  • Progressive intracranial occlusive arteropathy
  • Spontaneous occlusion of the Circle of Willis

Frequently Asked Questions

Early warning signs include recurrent transient ischemic attacks (brief episodes of weakness, numbness, or speech difficulty that resolve within minutes), unexplained headaches, sudden loss of vision, seizures, or involuntary movements (chorea). In infants, frequent crying with pallor or unexplained falls may be clues. Any sudden neurologic change warrants immediate medical evaluation.;How is moyamoya disease definitively diagnosed?::Diagnosis relies on imaging that visualizes the cerebral vessels. A digital subtraction angiogram (DSA) is the gold standard, showing narrowing of the internal carotid arteries and the characteristic “puff of smoke” collateral network. Non‑invasive alternatives include magnetic resonance angiography (MRA) or computed tomography angiography (CTA), which can suggest the pattern but may need confirmation with DSA.;What are the main treatment options and how successful are they?::The cornerstone of therapy is surgical revascularization to restore blood flow. Two common procedures are direct bypass (superficial temporal artery to middle cerebral artery) and indirect techniques (encephaloduroarteriosynangiosis, multiple burr holes). Studies show a 70‑90% reduction in stroke recurrence after successful surgery, especially when performed early. Medical management alone (antiplatelet agents, blood pressure control) is insufficient for long‑term protection.;How can I reduce the risk of stroke or hemorrhage in daily life after a moyamoya diagnosis?::Maintain optimal blood pressure and avoid dehydration, which can worsen cerebral perfusion. Use antiplatelet therapy only if prescribed, and avoid smoking or illicit drugs. Encourage regular, low‑impact aerobic activity as tolerated, and schedule routine follow‑up imaging to monitor vessel changes. Promptly treat infections or fever, as they can precipitate ischemic events.;
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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