[Clinical and electrophysiological findings in various hereditary sensory neuropathies].

An electrophysiological study, comprehensive of peripheral sensory and motor conduction velocity (SCV, MCV), motor cortical stimulation (CS), median nerve somatosensory evoked potentials (SSEPs), brainstem evoked potentials (BAEPs) and sural nerve biopsy, was performed on 100 hereditary ataxia patients: 48 with Friedreich's ataxia (FA), 18 with Early Onset Cerebellar Ataxia (EOCA) and 34 with Autosomal Dominant Cerebellar Ataxia (ADCA). An early "peripheral" and "central" sensory impairment was observed in FA probably due to axonal loss and not related to disease severity or duration. On the contrary, BAEP and CS findings suggested a progressive involvement of the auditory and motor pathways. The presence of a non progressive sensory neuropathy allowed a distinction of EOCA patients in two groups: with and without peripheral neuropathy. The clinical and genetic heterogeneity was confirmed by the variability of evoked potential results. The ADCA patients showed the mildest degree of electrophysiologic abnormalities with an involvement of the peripheral pathways, both sensory and motor, more frequent than the central ones.