Spinocerebellar Ataxias

Definition

The spinocerebellar ataxias (SCAs) are a group of inherited conditions that affect the brain and spinal cord causing progressive difficulty with coordination.

Description

The SCAs are named for the parts of the nervous system that are affected in this condition. Spino refers to the spinal cord and cerebellar refers to the cerebellum or back part of the brain. The cerebellum is the area of the brain that controls coordination. In people with SCA, the cerebellum often becomes atrophied or smaller. Symptoms of SCA usually begin in the 30s or 40s, but onset can be at any age. Onset from childhood through the 70s has been reported.

As of early 2001, at least 13 different types of SCA have been described. This group is numbered 1-14 and each is caused by mutations or changes in a different gene. Although the category of SCA9 has been reserved, there is no described condition for SCA9 and no gene has been found. Spinocerebellar ataxia has also been called olivopontocerebellar atrophy, Marie's ataxia, and cerebellar degeneration. SCA3 is sometimes called Machado-Joseph disease named after two of the first families described with this condition. All affected people in a family have the same type of SCA.

Genetic profile

Although each of the SCAs is caused by mutations in different genes, the types of mutations are the same in all of the genes that have been found. Most genes come in pairs; one member of a pair comes from a person's mother and the other one comes from their father. The genes are made up of deoxyribonucleic acid (DNA) and the DNA is made up of chemical bases that are represented by the letters C, T, G, and A. This is the DNA alphabet. The letters are put together in three letter words. The arrangement of the words are what give the gene its meaning and therefore tells the body how to grow and develop.

Content licensed from:

Author Info: Karen M. Krajewski MS, The Gale Group Inc., Gale, Detroit, Gale Encyclopedia of Genetic Disorders Part I, 2002

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