ataxia, lack of coordination of the voluntary muscles resulting in irregular movements of the body. Ataxia can be brought on by an injury, infection, or degenerative disease of the central nervous system, e.g., syphilis, encephalitis, brain tumor, or multiple sclerosis. The term also designates a specific type of cerebral palsy.

Inability to coordinate voluntary muscular movements. In common usage, the term describes an unsteady gait. Hereditary ataxias are usually caused by degeneration of the spinal cord, cerebellum, or other parts of the nervous system. The most common is Friedreich ataxia, which begins at ages 3–5, progressing slowly to almost complete incapacity by age 20. There is no specific therapy. Metabolic disorders, brain injuries, and toxins can cause ataxia.

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