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The spinocerebellar ataxias are a group of conditions characterised by an adult-onset degeneration of nerve cells in the cerebellum of the brain resulting in neurological disturbances such as impaired muscle coordination, tremors, involuntary movements and affected speech. Each condition within the group, however, also has a distinct list of associated clinical features. The differences in clinical presentation are related to the different genetic basis of each condition. A number of different faulty genes located on different chromosomes have been identified. Faulty copies of these genes involve an increase in the number of repeated sequences within the genetic code in some forms of the condition, so that the gene does not work properly. The inheritance pattern in families is described as autosomal dominant in many forms of the condition. Inheritance may also follow an autosomal recessive pattern in some cases. For some of the spinocerebellar ataxias, genetic testing before symptoms appear (presymptomatic testing or predictive testing) is available. This is generally recommended in consultation with a multidisciplinary healthcare team and may include a clinical geneticist and genetic counsellor. |