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The hereditary ataxias are a group of neurological disorders (ataxias) of varying degrees of rarity that are inherited, in contrast to a related group of neurological disorders that are acquired through accidents, injuries, or other external agents. The hereditary ataxias are characterized by degenerative changes in the brain and spinal cord that lead to an awkward, uncoordinated walk (gait) accompanied often by poor eye-hand coordination and abnormal speech (dysarthria). Hereditary ataxia in one or another of its forms may present at almost any time between infancy and adulthood.
The classification of hereditary ataxias is complex with several schools of thought vying for recognition. This report follows the classification presented by Dr. Thomas D. Bird and the University of Washington’s GeneReviews.
This classification is based on the pattern of inheritance or mode of genetic transmission of the disorder: i.e., autosomal dominant, autosomal recessive and X-linked. The autosomal dominant ataxias, also called the spinocerebellar ataxias, are usually identified as SCA1 through SCA37. Also included are several “episodic ataxias”, as well as a very rare disorder known as DRPLA (dentato-rubro-pallido-luysian atrophy). This report deals with the autosomal dominant hereditary ataxias. There are fewer autosomal recessive hereditary ataxias than autosomal dominant hereditary ataxias, and X-linked forms of ataxia are very rare.
At one time, all autosomal dominant ataxias were called Marie’s ataxia and all autosomal recessive ataxias were called Friedreich’s ataxia. This is no longer appropriate because there is now much more accurate information about these diseases.