Degenerative ataxias.

This review summarizes recent advances that have taken place in the field of inherited ataxias. There is increasing understanding of these disorders, primarily because of advances in the field of molecular genetics. Although the Friedreich's ataxia gene has not been cloned yet, there is increasing information about the precise location of this mutation. The chromosomal location for a distinct type of recessive ataxia associated with vitamin E deficiency was discovered. An adult- onset Friedreich's phenotype may result from a gene abnormality of the same locus as classic Friedreich's ataxia. Two distinct types of dominantly inherited ataxic syndromes are due to different trinucleotide repeat mutations, one on chromosome 6 (spinocerebellar ataxia type 1) and another on chromosome 12 (dentatorubropallidoluysian atrophy). The genes for Machado-Joseph disease as well as for a distinct type of dominantly inherited ataxia originally described from Cuba were mapped to chromosome 14 and chromosome 12, respectively. Advances were made in defining the imaging abnormalities seen in different types of ataxias.