Hereditary ataxias

There are many causes of hereditary ataxia, These can be grouped into categ ories of autosomal recessive, autosomal dominant, and X-linked, Molecularly , many of them are due to trinucleotide repeat expansions. In Friedreich at axia, the trinucleotide repeat expansions lead to a "loss of function." In the dominant ataxias, the expanded repeats lead to a "gain of function," mo st likely through accumulation of intranuclear (and less commonly cytoplasm ic) polyglutamine inclusions. Channelopathies can also lead to ataxia, espe cially episodic ataxia, Although phenotypic characteristics are an aid to t he clinician, a definitive diagnosis is usually made only through genotypic or molecular studies. Genetic counseling is necessary for the testing of s ymptomatic and asymptomatic individuals. No effective treatment is yet avai lable for most ataxic syndromes, except for ataxia with isolated vitamin E deficiency and the episodic ataxias.