Ataxia occurs when the parts of the nervous system controlling movement are damaged. People with ataxia experience a failure of muscle control in their arms and legs, resulting in a lack of balance and coordination or a disturbance of gait.
Most disorders that result in ataxia cause cells in the cerebellum of the brain to degenerate, or atrophy. Sometimes, the spine is also affected. The phrases cerebellar degeneration and spinocerebellar degeneration describe the changes that take place in a person's nervous system; neither term constitutes a specific diagnosis. Cerebellar and spinocerebellar degeneration have many different causes. The age of onset of the resulting ataxia varies depending on the underlying cause of the degeneration.
Many ataxias are hereditary and are classified by chromosomal location and pattern of inheritance.
Autosomal dominant is a form of the disease in which the affected person inherits a normal gene from one parent and a faulty gene from the other parent.
Autosomal recessive is that form of the disease in which both parents pass on a copy of the faulty gene to the offspring. Among the more common inherited ataxias are Friedreich's ataxia and Machado-Joseph disease. Sporadic ataxias can also occur in families with no prior history.
Ataxia can also be acquired. Conditions that can cause acquired ataxia include stroke, multiple sclerosis, tumors, alcoholism, peripheral neuropathy, metabolic disorders, and vitamin deficiencies.
This answer is based on source information from the National Institute of Neurological Disorders and Stroke.