[Evoked motor potentials in the diagnosis of multiple sclerosis]

The authors examined evoked motor potentials (MEP) of the upper extremities in a group of 43 patients with multiple sclerosis using transcranial cortical and spinal stimulation. As abnormal they rated a prolongation of the motor conduction time by more than 3 sigma above the mean value recorded in the control group or when the response could not be evoked. The central motor conduction time between the cortex and cervical spine was abnormal in 76.7% of patients. The authors did not find a correlation between the severity of the paresis and the degree of electrophysiological abnormality. In frust and mild pareses the sensitivity was 80%. The frequency of abnormalities correlated with the degree of the diagnostic certainty. In patients with a probable diagnosis (according to Poser) abnormalities were present in 41.6%, when the diagnosis was certain, in 90.3%. In prolongation of the time of central motor conduction among all abnormalities 65.1% were due to prolonged motor conduction and in 27.9% the response could not be evoked. MEP examination is a sensitive technique for the detection of clinical and subclinical lesions and as to its sensitivity it is better than visual EP.