Spinal and cortical somatosensory evoked potential monitoring during corrective spinal surgery with 108 patients

To reduce the incidence of neurologic complications following spinal surgery, somatosensory evoked potentials (SEPs) were monitored in 108 patients. An electrode with four in-line contacts was used to record spinal SEPs in the epidural space in 33 patients at locations both rostral and caudal to the surgical site. Cortical SEPs were successfully monitored in 107/108 patients and spinal SEPs in all 33 attempted epidurally. Spinal conduction velocities were found to range from 43.9 to 110.5 m/s depending on vertebral level and the time location of the measured peak in the response waveform. Frequency power spectra of the SEP waveforms were found to be a reliable adjunct to peak latency amplitude analysis in the time domain. Use of caudal and rostral epidural, subcortical, and cortical electrode sites were found to be the most reliable technique for the maximum patient safety.