Disability in multiple sclerosis. The role of transcranial magnetic stimulation.

Transcranial magnetic stimulation (TMS) was used to measure intensity threshold, conduction of the central motor pathways (CMCT) and amplitude of the motor evoked potentials (MEPs) in 50 patients with definite form of multiple sclerosis (MS), 31 females and 19 males, aged 15 to 58 years (mean 31.9 +/- 9.8). Abnormalities in at least one parameter after TMS have been found in 76% of the cases. Interside CMCT asymmetries increased the diagnostic yield to 86% of the patients. Three MS individuals with normal clinical examination have prolonged CMCT (silent lesions). There was significant correlation between CMCT and evolution of the disease, and with the degree of pyramidal signs. CMCT correlated with cerebral motor pathway, pons, and cervical cord lesions in MRI study. TMS is an easy and reliable method to quantify pyramidal and cerebellar dysfunction in MS and monitoring the evolution of the disease.