Moyamoya disease (MMD) is a rare, progressive cerebrovascular disorder caused by blocked carotid arteries at the base of the brain in an area called the basal ganglia, reducing blood flow to your brain.
Tiny blood vessels then open up at the basal ganglia in an attempt to supply the brain with blood. The word “moyamoya” means “puff of smoke” in Japanese, a term describing the appearance of this cluster of tiny blood vessels.
These tiny clusters of blood vessels cannot supply the necessary blood and oxygen to the brain, resulting in temporary or permanent brain injury.
The Ministry of Health and Welfare of Japan has defined 4 types of moyamoya disease: ischemic, hemorrhagic, epileptic, and “other.” The ischemic type has been shown to predominate in childhood, while the hemorrhagic type is more often observed in the adult population.
The highest prevalence of MMD is found in Korea and Japan, with a higher female to male ratio. Some individuals with Moyamoya disease have a close relative who is also affected; in these cases, researchers think that Moyamoya disease is the result of inherited genetic abnormalities. Studies that look for the abnormal gene(s) may help reveal the biomechanisms that cause the disorder.
Symptoms
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.
Adults may also experience these symptoms that arise from blocked arteries, but more often experience a hemorrhagic stroke due to bleeding into the brain. Other symptoms may include:
- seizures
- headaches
- disturbed consciousness
- involuntary movements
- Difficulties with speaking or understanding others (aphasia)
- vision problems
- cognitive and/or sensory impairment.
These symptoms can be triggered by exercise, crying, coughing, straining, or fever.
Causes
The exact cause of moyamoya disease is unknown. Moyamoya disease is more common in Japan, Korea, and China, but it also occurs in other parts of the world.
Researchers believe the higher concentration of moyamoya disease in these Asian countries strongly suggests the disease may have genetic causes.
Changes in the RNF213 gene have been associated with the condition. There are other gene changes involved in moyamoya disease, that remain to be found.
Moyamoya is also associated with certain conditions, such as Down syndrome, sickle cell anemia, neurofibromatosis type 1, and hyperthyroidism.
Prognosis
Moyamoya disease is progressive and without treatment can be fatal due to intracerebral hemorrhage(bleeding within the brain).
Without surgery, the majority of individuals with Moyamoya disease will experience mental decline and multiple strokes because of the progressive narrowing of arteries.
In studies with long-term follow-up of untreated patients, progressive neurologic deficits and poor outcomes were reported in 50 to 66 percent. The overall mortality rate from Moyamoya disease is about 10% in adults, and 4.3% in children.
Treatments
Treatment for Moyamoya disease does not reverse the primary disease process but protects against further strokes by improving hemispheric blood flow.
Medications may be prescribed to reduce the risk of stroke or to aid in seizure control.
Several types of surgery can restore blood flow (revascularization) to the brain by opening narrowed blood vessels or by bypassing blocked arteries.
Children usually respond better to revascularization surgery than adults. Some individuals have no further strokes or related problems after surgery.
