ABSTRACT
Somatosensory evoked potential(SEP) monitoring was performed intraoperatively in 28 patients with extramedullary or intramedullary tumors.Dissection of intramedullary tumor usually leads to decrease of amplitude and increase of latency in SEP. SEP reappeared at the end of operation in 2 cases of Frankel A grade extramedullary tumors whose SEP disappeared during operation with functional recovering to some degree. In 2 cases of Frankel B and C grade intramedullary tumors, the amplitude of SEP decreased by more than 40% and the latent period in SEP increased by more than 5% during operation,and the surgical procedure was paused for a while.There was slight reversible injury of nerve post operatively. In 8 of 12 cases of Frankel D and E grade intramedullary tumors, the amplitude of SEP descended nearly by 50% and elongation of latency in SEP was about 7% during surgery. SEP was reduced lightly in other 4 cases and all achieved good recovery. Intraoperative monitoring of spinal SEP and cortex SEP can reflect the change of spinal function, reduce post operative complication, and predict prognosis.