What is Ataxia?
The word “ataxia”, comes from the Greek word, “a taxis” meaning “without order or incoordination”. The word ataxia means without coordination. People with ataxia have problems with coordination because parts of the nervous system that control movement and balance are affected. Ataxia may affect the fingers, hands, arms, legs, body, speech, and eye movements. The word ataxia is often used to describe a symptom of incoordination which can be associated with infections, injuries, other diseases, or degenerative changes in the central nervous system. Ataxia is also used to denote a group of specific degenerative diseases of the nervous system called the hereditary and sporadic ataxias which are the National Ataxia Foundation’s primary emphases.
Diagnosis is based on a person’s medical history, family history, and a complete neurological evaluation including an MRI scan of the brain. Various blood tests may be performed to rule out other possible disorders which may present similar symptoms. Genetic blood tests are now available for some types of hereditary ataxia to confirm a diagnosis or as a predictive test to determine if someone has inherited an ataxia gene known to affect other family members.
The hereditary ataxias are genetic, which means they are caused by a defect in a certain gene that is present from the start of a person’s life. All of us have genes that have little mistakes or variations but most of these do not cause disease, they are called mutations. The hereditary ataxias can be divided into those that are dominantly inherited and those that are recessively inherited.
Autosomal recessive inherited diseases also affect males and females equally but it takes a “double dose” of the ataxia gene to result in disease symptoms. Both parents must be carriers of the disease gene and each must pass on the ataxia gene to their child for the double dose that is needed to produce symptoms of the recessive disease. Each child of parents who are carriers of a recessive disease has a 25% chance of inheriting two ataxia genes so will develop the disease, a 50% chance of inheriting just one of the ataxia genes and, therefore, be a carrier and a 25% chance of inheriting no ataxia gene and be completely free of ataxia. Because a single recessive ataxia gene does not cause symptoms, it can be passed on in a family for generations without being recognized. Therefore, there is often no “family history” of ataxia if the disease is inherited as a recessive gene.