On the spinal pathways mediating scalp-SEPs to upper and lower limb nerve stimulation: case report and discussion.

Scalp-SEPs to peroneal nerve stimulation were abnormal in a patient with an intradural meningeoma which was compressing the antero-lateral quadrant of the 1st and, partly, the 2nd cervical myelomers. In contrast, spine and scalp-SEPs were symmetrically normal during the sural, median and ulnar nerve stimulation of either side. On surgery, it was observed that the tumor had left the dorsal columns (DCs) almost unaffected. It is argued, in agreement with the bulk of experimental evidence, that in humans the scalp-SEPs to lower mixed nerve stimulation are also mediated, at the rostral cord level, by fast-propagating tracts ascending outside the DCs.