The purpose of this study is to determine if people with moyamoya disease who have insufficient blood flow are at a higher risk for stroke.

Moyamoya disease is a rare medical disorder that affects the blood vessels (pipes that transport blood) in the brain. In Moyamoya disease, the large blood vessels in the middle of the brain close down over time. The cause of this disorder is unknown. In order to compensate for this narrowing, the body grows new small blood vessels around the blockage. These small branches grow larger (and may be more numerous) to give the disorder its name. "Moyamoya" is the Japanese term for "puff of smoke" and is used to describe the hazy appearance of these small blood vessels on an angiogram.

Treatment for moyamoya is difficult because so little is known about the disease. Some people never have a stroke while others may have several. It is likely that the strokes are due to insufficient blood flow to the brain. There are surgical procedures that may improve blood flow to the brain, however, these procedures may cause complications and may not always improve the blood flow.

The main purpose of this study is to determine if people with moyamoya disease who have insufficient blood flow are at a higher risk for stroke. In this study researchers will learn more about the risks and potential benefits of surgical treatment. This information will help decide if there are people at higher risk for stroke who might benefit from surgery or if there are those at a lower risk who might not benefit.

In this study, participants will undergo baseline clinical and laboratory evaluation. Measurements of blood flow to the brain and oxygen use will be obtained using by positron emission tomography (PET). Participants will be followed for up to 5 years. PET studies will be conducted one and three years after enrollment to determine if blood flow improves over time. Participants treated with surgery (at the discretion of their treating physicians) will also be followed for perioperative complications, improvement in blood flow, and long term risk of stroke.

Inclusion Criteria:

• Adult > 18 years of age
• Capable of informed consent
• Clinical: Both asymptomatic and symptomatic patients will be included.
• Anatomic: Unilateral or bilateral imaging findings consistent with moyamoya collaterals (Suzuki stages 3 and 4) on digital subtraction, computed tomographic, or magnetic resonance angiography (after Suzuki and Kodama, 1983)

Exclusion Criteria:

• Any other disease that might be responsible for the vasculopathy, including atherosclerosis, neurofibromatosis, meningitis, sickle cell disease, skull base radiation therapy.
• Pregnancy: All women of child-bearing potential will be tested for pregnancy on the day of the enrollment and throughout the course of the study.
• Surgery: Prior open or endovascular revascularization procedures, unless there have been ischemic symptoms since surgery and angiographic evidence that the procedure was not successful

Persons with moyamoya disease will be recruited without restriction in regards to gender, race, age, and socioeconomic status. At Washington University, persons will be identified and recruited from the Neurosurgery service, the Stroke service of the Department of Neurology, and the Interventional Neuroradiology service.

We have invited several established stroke investigators at large tertiary care facilities in the Midwest to form a cooperative study group. All these investigators have large-volume clinical practices and see several people with moya moya disease each year.