Ataxia

Ataxia (from Greek ataxiā, meaning failure to put in order) is unsteady and clumsy motion of the limbs or trunk due to a failure of the gross coordination of muscle movements. Patients with ataxia are diagnosed and treated by neurologists.

Ataxia often occurs when parts of the nervous system that control 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. While the term ataxia is primarily used to describe this set of symptoms, it is sometimes also used to refer to a family of disorders. It is not, however, a specific diagnosis.

Most disorders that result in ataxia cause cells in the part of the brain called the cerebellum to degenerate, or atrophy. Sometimes the spinal cord is also affected. The phrases cerebellar degeneration and spinocerebellar degeneration are used to describe changes that have taken 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, in which the affected person inherits a normal gene from one parent and a faulty gene from the other parent; and autosomal recessive, in which both parents pass on a copy of the faulty gene. Among the more common inherited ataxias is Friedreich's ataxia, which is inherited in a recessive fashion. The dominantly-inherited ataxias are usually referred to as spinocerebellar ataxias (SCAs). The most common SCAs are SCA3 (or Machado-Joseph disease) and SCA2. SCAs can also occur in families with no prior history. These patients are then referred to as having a de novo mutation.

Ataxia can also be acquired. Conditions that can cause acquired ataxia include stroke, multiple sclerosis, tumors, lesions of the central nervous system or spinal cord, alcoholism, peripheral neuropathy, metabolic disorders, and vitamin deficiencies. Ataxia may indicate a Vitamin B12 deficiency.

Dysdiadochokinesia is a sign of cerebellar ataxia.

University of Minnesota researchers suggested in 2006 that Abraham Lincoln may have suffered from spinocerebellar ataxia type 5, thus accounting for his clumsy gait.

Recently, scientists at UCLA identified mutations in a voltage-gated-potassium ion channel as a cause for a dominantly-inherited ataxia, designated SCA13.

International Ataxia Awareness Day is celebrated on September 25th annually. The 8th annual event will be on September 25, 2007.