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Moyamoya Disease

Moyamoya disease is a rare, progressive cerebrovascular disorder where typically the internal carotid artery becomes smaller and blocked over time. The name “moyamoya” describes in Japanese the look of the abnormal tiny vessels formed to compensate for the blockage.

It was first described in Japan in the 1960s and has since been found in individuals in the United States, Europe, Australia and Africa. The disease affects children and can also occur in adults.

What Causes Moyamoya Disease?

Moyamoya disease is caused by gradually blocked large arteries at the base of the brain in an area called the circle of Willis.

It may tend to run in families, so researchers think that some moyamoya disease is the result of inherited genetic abnormalities. Studies that look for the abnormal gene(s) may help reveal the pathophysiology that causes the disorder. This discussion would be explored in Pediatric Neurovascular clinic with our genetics counsellors and neurovascular team.

In addition, moyamoya is associated with sickle cell disease as well as neurofibromatosis. Moyamoya can also occur after radiation treatments to the brain for other conditions.

What Are the Symptoms of Moyamoya Disease?

In children, the first symptom of moyamoya disease is often stroke, or recurrent transient ischemic attacks (TIA, commonly referred to as “mini-strokes”), frequently accompanied by muscular weakness or paralysis affecting one side of the body, or seizures.

Adults most often experience a hemorrhagic stroke due to recurring hemorrhage from the affected brain vessels.

How Is Moyamoya Disease Treated?

Medical treatment is typically started in the form of daily aspirin therapy to try to decrease the risk of stroke. The treatment that most effectively decreases the risk of stroke from moyamoya is surgery.

There are several types of revascularization surgery that can restore blood flow to the brain by providing new collateral blood supply either directly or indirectly. Direct blood supply can be provided by anastomosing a scalp artery to a cerebral branch (STA-MCA). Indirect techniques can involve placing dura and the superficial temporal artery (STA) on the brain surface which then grows new connections to the brain. Children usually respond well to revascularization surgery. The majority of individuals have no further strokes or related problems after surgery.

What Are the Long-term Effects of Moyamoya Disease?

Individuals with this disorder may have disturbed consciousness, speech deficits (usually aphasia), sensory and cognitive impairments, involuntary movements and vision problems.