Visually evoked potentials in Friedreich's ataxia.

Visual evoked potentials to pattern-reversal stimulation have been recorded in 45 patients with Friedreich's ataxia. In six patients, no response could be obtained because of optic atrophy; altogether, pathological results were found in 25 patients (55%). Normal latencies were recorded in 20 patients (45%). No statistically significant connection could be drawn between the result of the VEP testing and visual acuity, age, or onset and duration of sickness, but there was a strikingly familiar accumulation of results. There is a good conformity between our results and the incidence of optic atrophy in later stages of the disease as shown by pathological-anatomical and epidemiological studies. We have demonstrated that optic nerve lesions in Friedreich's ataxia are not as rare as is frequently assumed and that the VEP is a valuable tool for detecting them. On the other hand, unfortunately, the VEP is of no help in the differential diagnosis of Friedreich's ataxia versus multiple sclerosis.