Visual, auditory and somatosensory pathway involvement in hereditary cerebellar ataxia, Friedreich's ataxia and familial spastic paraplegia.

Pattern-reversal visual, auditory and somatosensory evoked potentials were recorded from 11 patients with hereditary cerebellar ataxia, 13 with familial spastic paraplegia and 7 with Friedreich's ataxia. In all the 31 patients the conduction velocity along the median and tibial nerves to the level of the spinal cord was normal. Five of the 7 patients with Friedreich's ataxia had reduced sural nerve sensory potentials. There was electrophysiological evidence of malfunction along one or several pathways within the CNS in 8 of the 11 patients with cerebellar ataxia, 4 of the 13 with familial spastic paraplegia, and in all 7 cases of Friedreich's ataxia. The increase in latency of visual, auditory and somatosensory evoked cortical potentials is attributed to nerve fibre loss in the central pathways with associated slowing of conduction.