The Use of Motor-Evoked Potentials in Clinical Trials in Multiple Sclerosis

Motor-evoked potentials (MEPs) can be used to assess the integrity of the descending corticospinal tract in the laboratory. Evoked potentials (EPs) have been widely used in the past for the diagnosis of multiple sclerosis (MS), but they are now becoming more useful in assessing the prognosis of the disease. Motor-evoked potentials have been included in EP scales that have demonstrated good correlations with clinical disability. Soon after the onset of MS, it is possible to detect an ongoing process of neurodegeneration and axonal loss. Axonal loss is probably responsible for the disability and disease progression that occurs in MS. Given the good correlations of EPs in detecting disease progression in MS, they have been used to monitor the effects of drugs used to treat the disease. Several clinical trials used MEPs as part of their EP evaluation, but MEPs have never been used as a measure of efficacy in clinical trials testing neuroprotective agents, although MEPs could be a very promising tool to measure neuroprotection and remyelination resulting from these drugs. To be used in multicenter clinical trials, MEP readings should be comparable between centers. Standardized multicenter EP assessment with central reading has been demonstrated to be feasible and reliable. Although MEP measurements have been correlated with clinical scores and other measures of neurodegeneration, further validation of MEP amplitude measurements is needed regarding their validity, reliability, and sensitivity before they can be routinely used in clinical drug trials in MS.