Reversible loss of somatosensory evoked potentials during anterior cervical spinal fusion

Occlusion of the carotid artery has been reported as a complication of retractor placement for anterior cervical spine surgery (1). Failure to detect this occlusion can possibly cause cerebral ischemia and consequent cortical damage. Palpation of the temporal artery pulse has been used as a means of detecting vascular occlusion, but anatomical variations and inability to locate the pulse intraoperatively can make this technique unreliable for monitoring during surgery. Somatosensory evoked potentials (SSEP) have been used during surgery on the spinal column as a means of continuously assessing cord function. For surgical procedures in the cervical region, SSEP from median or posterior tibial nerve stimulation may be used for the monitoring of operations in the high or low cervical spine, respectively. Somatosensory evoked potentials have also been used for the detection of central or brainstem ischemia (2,3). In addition, median nerve evoked responses have been used as a method of monitoring adequate cerebral perfusion during carotid endarterectomy (6). We present three case reports of patients undergoing operations for anterior cervical spinal fusion, in which changes in the SSEP signal occurred concurrently with retractor placement and returned to baseline after the retractor was repositioned.