[Electrophysiologic studies (auditory and somatosensory evoked potentials) in Friedreich's ataxia]

Auditory and somatosensory evoked potentials were recorded from 10 patients suffering from Friedreich's ataxia. All patients were subjected to audiological tests and EMG-ENG study. Acoustic evoked potentials recordings included brainstem acoustic evoked potentials and long latency components. Peripheral and central components of somatosensory evoked potentials were obtained by stimulating the median nerve at the wrist and elbow. Various abnormalities of the cortical components were observed in all patients for both acoustic and somatosensory evoked potentials. Analysis of brainstem acoustic evoked potentials and of the early components of somatosensory evoked potentials showed a different incidence of abnormalities. The main feature of brainstem acoustic evoked potential changes was the frequent absence of one or more waves; the greatest abnormalities occurred in patients whose disease was of long duration. Long latency components (N85) were significantly prolonged in all but one patient. There was often an absence or reduction of early somatosensory evoked potentials with normal or near normal latencies, even though cortical responses were markedly prolonged. The sensory conduction velocity between stimulation sites at wrist and elbow was normal in all patients. Clinically brainstem acoustic evoked potentials may prove to be a reliable means of monitoring the progression of the disease, while long latency components and somatosensory evoked potentials could be used as complementary procedures in early diagnosis.