Motor evoked potentials by magnetic stimulation in hereditary and sporadic ataxia.

We report the study of motor evoked potentials by magnetic stimulation in 26 subjects with hereditary or sporadic ataxia. The subjects included 15 cases of late onset cerebellar ataxia (12 classified as olivopontocerebellar atrophy (OPCA), 3 as spinocerebellar atrophy (SCA)) and 11 cases of early onset cerebellar ataxia (4 Friedreich's ataxia (FA) and 7 unclassifiable in Friedreich's ataxia (NFA)). All subjects with FA and SCA had delayed central motor conduction times, more accentuated in corticospinal tracts directed to lumbar motoneurons. A similar but less marked slowing was observed in about half of the subjects with OPCA and NFA. In the last two groups the anomalies are more frequent in hereditary than in sporadic forms.