Moyamoya Disease - Causes and Symptoms of Moyamoya Disease

By: Corwin Brown

Recognised in Japan in the 1960s, this is a progressive occlusive cerebral arteritis affecting the distal internal carotid arteries near the Circle of Willis. Moyamoya is Japanese for "puff of smoke" and describes the appearance of the resultant network of abnormal small collateral vessels seen on angiography. There is a familial form which links to a gene on chromosome 17q25 - though the exact underlying cause remains unknown.

Moyamoya Disease is a rare disorder of uncertain cause that leads to irreversible blockage of the main blood vessels to the brain as they enter into the skull. This blockage tends to cause strokes or seizures. The process of blockage (vascular occlusion) once it begins tends to continue despite any known medical management unless treated with surgery.

Causes of Moyamoya Disease
The cause of moyamoya disease is not known. However, researchers suspect there may be a genetic link because of its high rate of incidence in certain Japanese families.

Researchers suspect a genetic link because of the 9 percent incidence of the disease found in certain Japanese families. A gene for familial moyamoya disease has been located on chromosome 17q25 and further study of the gene may reveal the cause of the disorder.

The cause of moyamoya disease is unknown. Possible explanations for the disorder include injuries to the brain, infection, multifactorial inheritance, genetic factors, or other causes. For example, moyamoya disease has been associated with meningitis, radiation therapy to the skull in children, and genetic conditions such as Down syndrome, neurofibromatosis, and sickle cell anemia.

Approximately 10% of cases of Moyamoya syndrome are due to a genetic cause and are termed primary Moyamoya syndrome. Secondary Moyamoya syndrome refers to cases in which the syndrome is a consequence or result of another underlying disorder. In secondary Moyamoya syndrome, when it is not a result of a genetic cause, it is important for the physician to determine the root underlying cause.

Symptoms of Moyamoya Disease
The initial symptoms of moyamoya disease are somewhat different in children and adults. In children, there is ischemia due to stenosis and occlusion of the circle of Willis, a ring of arteries at the base of the brain.

Children also often experience temporary weakness in one or more of their extremities during strenuous physical activity or when crying. Adults can also present with brain hemorrhage causing neurologic symptoms in addition to nonhemorrhagic strokes, TIA's and headaches.

The symptoms and clinical course vary widely and depend upon the location and severity of the hemorrhage or damage. Thus signs and symptoms may range from asymptomatic to transient events to severe neurologic deficits.

Intracranial hemorrhage is the most common symptom. Ischemic symptoms such as those found in children may also occur.

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.

Other signs and symptoms that occur in both children and adults include headaches, altered consciousness, speech difficulties, vision problems, involuntary movements, mental retardation, psychiatric problems and difficulty with sensory and cognitive functions. Paralysis can also occur in the feet, legs or upper extremities. Most suffer from progressive cognitive deterioration and will eventually die due to intracerebral hemorrhage.

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