Central motor conduction differs between acute relapsing-remitting and chronic progressive multiple sclerosis

Objective: To characterize central motor conduction in relation to the clinical deficits and to the disease duration in 90 patients with acute relapsing-remitting MS (RR-MS) and in 51 patients with chronic primary or secondary progressive MS (P-MS). Methods: The triple stimulation technique (TST) was used to quantity the central motor conduction failure (expressed by the TST amplitude ratio) and conventional motor evoked potentials (MEPs) were used to measure the central motor conduction time (CMCT). Results: The TST amplitude ratio was reduced in presence of a clinical motor deficit (p = 0.02 for RR-NIS, p < 0.01 for P-MS), but did not significantly differ in RR-MS and P-MS (p > 0.05) when patients with similar clinical motor deficit were compared. The CMCT was not related to the clinical motor deficit in both RR-MS and P-MS. However, the CMCT was markedly prolonged in P-MS, when patients with similar clinical motor deficit and with similar disease duration were compared (p < 0.01). The differences were not attributable to differential involvement of the spinal cord, which was similar in RR-NIS and P-MS. Conclusions: Our results disclose differences between the central motor conduction in RR-NIS and P-MS that are not related to disease severity, spinal cord involvement or disease duration. (C) 2003 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.