[Classification and diagnosis of degenerative ataxias]

The degenerative ataxias comprise a wide spectrum of neurodegenerative diseases with varying clinical characteristics and heterogeneous neuropathology. Traditionally, classification of these diseases has been based on neuropathological criteria. Recently, however, clinical and genetic classifications have gained wide acceptance. These classifications distinguish between hereditary and non-hereditary ataxias. According to their mode of inheritance, the hereditary ataxias are further subdivided into autosomal-recessive and autosomal-dominant ataxias. The non-hereditary ataxias are divided into symptomatic ataxias with an identified cause and idiopathic ataxia with unknown cause. Diagnostic criteria based on history, clinical presentation and a number of laboratory tests have been defined for each category. More extensive ancillary tests are necessary to identify or exclude symptomatic causes of ataxia. Recent molecular genetic research has led to the identification of a number of gene loci and mutations responsible for certain types of hereditary ataxia.