Somatosensory evoked potentials in Charcot-Marie-Tooth disease

SEPs by median nerve stimulation have been performed in 18 adult patients (12 males and 6 females) affected by CMTD (type I, 13 patients; type II, 5 patients). All patients underwent MCV studies (median, ulnar, peroneal nerve), SCV studies (median and sural nerve), VEP, BAEP. N9 and N13 peaks were not detectable in 7/13 and 5/13 cases (HMSN type I) while cortical N19 were always recorded. Latency values of all responses were moderately or markedly delayed in all cases with HMSN type I, but proved normal or slightly delayed in HMSN type II cases. The prolonged latencies were mainly related to slowing of peripheral conduction. N9-N13 inter-peak was abnormally prolonged in 2 cases and N13-N19 in 2 other cases; both were prolonged in another case. In another 3 cases an abnormal BAEP was recorded. The few patients with abnormal CCT and BAEP probably belong to a borderline form between HMSN and hereditary ataxias.