Moyamoya disease is a progressive disease that affects the blood vessels in the brain. It is characterized by the narrowing and/or closing of the main arteries to the brain (usually the carotid arteries) just as they enter the skull. The brain attempts to overcome this narrowing and subsequent reduction in blood flow by enlarging other smaller blood vessels, a process called forming “collaterals.” In patients with Moyamoya disease, the enlargement of some of the usually small vessels at the base of the brain (called lenticulostriate arteries) leads to a pattern on an angiogram that somewhat resembles a “puff of smoke.” Moyamoya disease is most common in the Asian population, and the term moyamoya comes from the Japanese word for “puff-of-smoke”.
Patients with Moyamoya disease are prone to strokes and brain hemorrhages. Patients may come to medical attention either as children or adults, and symptoms may vary widely. Medical treatments are often ineffective, and surgery is frequently required. The goal of surgery is to provide more blood flow in order to decrease the future risk of stroke. Several procedures or combinations of procedures may be tried. Some of the most common include an encephalo-duro-arterio-synangiosis (EDAS), an intracranial to extracranial (EC-IC) bypass, and an encephalo-myo-synangiosis (EMS). An EDAS involves placing an unaffected scalp artery directly on the brain and allowing connections (collaterals) to develop between the artery and the existing brain arteries, thus improving blood flow to the brain. An EMS uses muscle from the side of the head (temporalis muscle), which has a good blood supply, to accomplish the same purpose. An EC-IC bypass creates a direct connection between a scalp artery and a brain (intracranial) artery.
The Neurovascular Surgery Service uses a multidisciplinary approach to the treatment of patients with Moyamoya disease, involving adult and pediatric neurosurgeons, stroke-neurologists, and neuroradiologists.