Central motor conduction in degenerative ataxic disorders: a magnetic stimulation study.

Central motor conduction to small hand muscles was measured using magnetic stimulation of the motor cortex and electrical stimulation of proximal motor roots in 11 patients with Friedreich's ataxia, 10 patients with early onset cerebellar ataxia with retained tendon reflexes (EOCA) and 13 patients with late onset degenerative cerebellar disease (LOCD). Central motor conduction was abnormal in 91% with Friedreich's ataxia, 70% with EOCA and 38% with LOCD. Central motor conduction abnormalities were not specific to individual disorders but were more severe and were related to disease duration in Friedreich's ataxia and EOCA.