[The nosology of cerebellar ataxias].

The group of cerebellar ataxias in adults represents a collection of very heterogeneous causes, pathogeneses, morphological changes and - as far as the hereditary types are concerned - heredity. Different modes of inheritance (dominant or recessive) signify different aetiologies to the geneticist. However, genetic heterogeneity is often associated with similarities of the phenotypes concerned. A decisive descriptive differentiation is that between a) degenerative changes of the cerebellum and the pertaining paths and b) cerebellar ataxias with associated non-neural changes. Meanwhile consensus has been reached regarding the gross anatomical classification of cerebellar ataxias into a) olivopontocerebellar atrophies ("cerebellopetal") b) primary cerebellar parenchymatrophies ("cerebellofugal"). A more reliable classification of the monogenic types will become possible in the near future with the help of the genetic marker of the HLA haplotypes. A comprehensive classification of non-hereditary and hereditary cerebellar ataxias based on clinical, pathologico-anatomical and genetic parameters is presented and summarized in Table 4.