Investigation of corticospinal dysfunction in multiple sclerosis and motoneuron diseases using motor evoked potentials

INTRODUCTION: The introduction of motor evoked potentials (MEP) into neurological practice has been very useful in the study of motor disorders, especially in patients with motor neurone diseases (MND) and multiple sclerosis (MS). MATERIAL AND METHODS: Forty patients with MS, twenty with MND and sixty-four apparently normal control were studied, to evaluate the use of MEP in such patients. Bilateral recordings were made from the abductor pollicis brevis and tibialis anterior. The variables studied were: cortical latency, radicular latency, central conduction time, motor excitation threshold coefficients of amplitude, duration and number of phases. RESULTS: There were significant differences in most variables when the control group and the patients were compared, and also between the two subgroups of patients (Wilk's lambda = 0.4197; p < 0.05). CA analysis significantly increased the sensitivity of the study (90.4%) with respect to analysis of latencies and central conduction times (70.4%). When analysis of the coefficients of duration and of phases was included, specificity increased by approximately 30% in both groups of patients. CONCLUSIONS: The great sensitivity of MEP as a neurophysiological diagnostic tool in investigation of corticospinal bundle lesions was demonstrated.