[Somatosensory evoked potentials after stimulation of the posterior tibial nerve in multiple sclerosis: comparative analysis with other modalities of evoked response and magnetic resonance].
Electrophysiological tests have proved to be a valuable method in assessing multiple sclerosis (MS) patients. In the last few years, scalp recorded short latency somatosensory evoked potentials to stimulation of nerves in the "lower extremity" have been more and more extensively employed. Some studies have aimed at comparing the sensitivity of MR imaging and multimodality evoked potentials, with somewhat conflicting results. In the present study posterior tibial nerve somatosensory evoked potentials (ptnSEPs) were performed in 29 MS patients with the aim to investigate the ability in revealing spinal cord conduction abnormalities and the sensitivity towards other evoked potentials and MR in MS. ptnSEPs showed a high percentage of abnormalities which did not significantly differ from that of visual evoked potentials; moreover in conjunction with median nerve SEPs can be used to localize thoracic or lumbar cord demielinating lesions, not evidenced on MR imaging. These results confirm that ptnSEPs, although non specific and crude in terms of precise localization, are a sensitive tool in detecting lesions, even subclinical, in MS patients. Moreover in anatomic regions like spinal cord where MR imaging is not very sensitive because the lower signal-to-noise ratio, they represent the only method available for demonstrating lesions.