Epidemiology of the inherited ataxias.

Current epidemiologic studies of the inherited ataxias are limited by complex and confusing systems of nomenclature and by the lack of minimal diagnostic criteria. Despite the difficulties of comparing one study to another, most descriptive investigations provide a prevalence estimate of less than 6 cases/100,000. In isolated, inbred populations, a prevalence as high as 23 cases/100,000 has been reported. Neuroepidemiologic techniques and current knowledge concerning the epidemiology of the inherited ataxias can be applied to future studies in three broad areas--definition, classification, and etiology. Future etiologic investigations based on a goal-oriented, collaborative effort following a case-control format offer the greatest likelihood of success.