MAGNETIC STIMULATION STUDY IN PATIENTS WITH MYOTONIC-DYSTROPHY

To further define motor nervous system alterations in myotonic dystrop hy (MD), motor potentials to transcranial and cervical magnetic stimul ation (MEPs) were recorded from the right abductor pollicis brevis mus cle in 10 patients with MD and in 10 healthy controls. Cortical and ce rvical latencies, central motor conduction time (CMCT), stimulus thres hold intensity and cortical MEP amplitudes expressed both as absolute Values and as %M were analysed. MEP cervical latency, absolute or rela tive amplitude and excitability threshold did not significantly differ in patients and controls. The mean cortical motor latency and CMCT we re significantly prolonged in MD patients with respect to normal subje cts. Moreover, CMCTs were found to be significantly related to stimulu s threshold intensity (P = 0.03) and only marginally related to absolu te cortical amplitude (P = 0.06). These findings are indicative of a c entral motor delay, also related to decreased excitability of motor ne urons, in patients with MD. No correlations were found between individ ual neurophysiological parameters and age, duration of disease and cli nical impairment. Our results suggest that magnetic stimulation studie s can detect subclinical dysfunctions of the central motor system in M D patients, as one of the multisystemic manifestations of the disease, rather independent of the primitive muscle damage. (C) 1997 Elsevier Science Ireland Ltd.