Moyamoya disease is the name for a condition caused by blocked arteries at the base of the brain. The term roughly translates from Japanese as, "puff of smoke," denoting the smoke-like appearance of the blood vessels seen on an angiogram of the brain (an x-ray image taken with radio-opaque dye). These vessels form because the body tries to create new pathways around the blockage to get blood to the brain.

Moyamoya is a fairly rare condition. Researchers estimate it affects less than one out of every million Americans. Incidence is higher in women and in people of Japanese descent. The condition is typically diagnosed in two different age groups - children and adults in their 30s and 40s.

Children with Moyamoya may experience seizures, headaches, dizziness, muscle weakness or paralysis on one side of the body and sensory impairments. These symptoms occur because the narrowed vessels can't supply enough oxygenated blood to the brain. Adults, on the other hand, are more likely to have brain hemorrhages, causing repeated mini-strokes (TIAs, or transient ischemic attacks), numbness and tingling on one or both sides of the body, speech disturbances and sudden vision problems. Researchers estimate risk of stroke in adults with Moyamoya is as high as 10 percent/year.

Treating Moyamoya

David Newell, M.D., a Neurosurgeon and Executive Director of the Swedish Neuroscience Institute, performs a procedure, called a superficial temporal artery to middle cerebral artery (STA-MCA) bypass (also referred to as an extracranial-intracranial bypass) to re-route the flow of blood to the brain. Surgeons locate the superficial temporal artery (STA, a vessel in the scalp that branches off from the external carotid artery in the neck) and cut one end of the vessel free. Next, the open end is brought up to meet the middle cerebral artery (MCA, a vessel on the surface of the brain that branches off from the internal carotid artery). A cut is made into the wall of the middle cerebral artery. Then using very tiny sutures, the free end of the STA is sewn onto the MCA. When the procedure is finished, blood flows around the blockage at the base of the brain, directly into the areas where it is needed.

After the surgery, most patients are relieved of their symptoms and can freely participate in most activities. The only restriction patients face is a requirement to wear a helmet during contact sports to reduce the risk of potential hemorrhage from a head injury.

Newell says the STA-MCA bypass is a technically challenging procedure. Surgeons must use microscopic-sized suture thread and need the highest-powered setting on the surgical microscope to visualize the vessels and make a secure connection between the vessels.

For general information on Moyamoya:

National Institute of Neurological Disorders and Stroke