Recovery of spinal cord conduction after surgical decompression for cervical spondylotic myelopathy: serial somatosensory evoked potential studies.

Abstract

We tested the utility of scalp-recorded median and tibial somatosensory evoked potentials (SEPs) as a measure of delineating the time course of postoperative recovery from cervical spondylotic myelopathy. We evaluated serial median and tibial SEP studies for 20 hands and 22 feet in 13 cervical spondylotic myelopathy patients during the first 6 mo postoperatively or longer. Serial sensory assessment of the hands and feet served to evaluate clinical correlation with the SEPs. The studies distinguished three recovery patterns of the SEPs based on the time course of the latencies of the N20 component for the median SEP and the P40 component for the tibial SEP. The latency started to decrease by 0.5 msec or more within 2 wk (seven hands and eight feet) or later than 2 wk (six hands and eight feet) postoperatively, or the change did not reach 0.5 msec (seven hands and six feet). In the late recovery group, the SEP improvement began as late as 10 wk postoperatively. Sensory recovery correlated with the SEP change in every group. An early onset of the SEP recovery predicts a favorable clinical course. The SEP may begin to improve later, and once it occurs, progressive return of function will follow.