[Cortical SEP of early and intermediate latency following stimulation of the median and tibial nerves in disseminated encephalomyelitis--relation to findings in cerebral nuclear magnetic resonance tomography].

Cortical somatosensory evoked potentials following median and tibial nerve stimulation were compared with the findings in nuclear magnetic resonance imaging in 23 patients with multiple sclerosis, 11 of whom presented with their first disease manifestation. Pathological SEP's were found in 55 percent of patients presenting with first manifestation and in 83 percent of those with a longer duration of illness. Except for one patient with spinal cord involvement only, in whom no cerebral lesions were seen, all patients showed periventricular lesions in NMR. Between 1 and 16 (4.7 +/- 3.5) non-periventricular isolated lesions were found per patient. Cortical SEP's are affected differently by lesions within the thalamocortical system: Plaques within the internal capsule may result in SEP-changes as seen in other causes of damage to this region. However, lesions in this strategic area may also remain clinically and electrophysiologically silent. Nevertheless, the size of the lesion seen in NMR is not relevant, as observed in one case of an extensive plaque within the centrum semiovale. Correlations between the lesions near the parietal cortex or within the parietal white matter and SEP-component alterations of intermediate latency (N55, N75) remained insignificant.