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The unique material of 188 cases of heredoataxias from 118 families was used for the genetic analysis of this disease group. The painstaking mathematical evaluation referring to 3,111 members of the affected families is based on the excellent analysis of the clinical conditions. Of the five groups into which the material is divided, group I (Friedreich's spinal ataxia [hereditary sclerosis, spinal form] ) and group III (Marie's cerebellar ataxia [cerebellar hereditary sclerosis]) show the most uniform symptomatology and course of the disease. Group IV contains congenital mild fragmentary forms (forme fruste), which do not show any particular tendency to progression. In group I-A and group II less well defined atypical and mixed forms are described.
Prolonged observation over several decades enabled the author to draw definite conclusions about the course of heredoataxias. Progressive mental deterioration, both in Friedreich's spinal ataxia and in Marie's cerebellar ataxia, is noteworthy in the terminal state.