Up and down the spinal cord: intraoperative monitoring of sensory and motor spinal cord pathways.

Monitoring of spinal cord function during certain orthopedic and neurosurgical procedures is done to reduce the likelihood of neurologic complications. This article is based on intraoperative experiences gained at Duke University Medical Center since 1978. Both ascending sensory (up) and descending motor (down) data can be evaluated to assist in improved patient outcomes. Refinements in technique and better understanding of the neural generators of evoked potentials obligate the components to have improved sensitivity and specificity of spinal intraoperative monitoring. An additional improvement has been the intraoperative use of motor evoked potentials. This discussion deals with a description of specific responses obtained following lower-limb mixed nerve stimulation in terms of neural generation, influences of rate and intensity, and anesthetic effects. The techniques and advantages of bipolar epidural recording and stimulation are discussed. Motor tract stimulation via the same epidural electrodes used for recording of sensory components is described. Case reports are presented to emphasize major points.