Characterization of neurophysiologic alerts during anterior cervical spine surgery

Study Design. A retrospective review of neurophysiologic alerts during anterior cervical surgery. Objectives. To examine incidence and types of neurophysiologic alerts and their correlation with new postoperative neurologic deficits after anterior cervical discectomy or corpectomy procedures. Summary of Background Data. Although multimodality neurophysiologic monitoring has been shown to predict iatrogenic neurologic injuries in scoliosis surgeries, their role in degenerative or trauma-related anterior cervical spine surgery is still unclear. Materials and Methods. We retrospectively reviewed 1,445 patients who underwent anterior cervical discectomy or corpectomy and arthrodesis with neurophysiologic monitoring that included transcranial electrical motor-evoked potentials (tceMEP), somatosensory-evoked potentials (SSEP), and spontaneous electromyography (EMG). Intraoperative alerts were analyzed for type, perceived cause, actions taken to reverse or minimize the possible spinal cord injury, and any new postoperative neurologic deficits. Results. There were 267 (18.4%) procedures that had either minor (spontaneous, sustained EMG) or major (tce-MEP/SSEP amplitude reduction) alerts. Patients who underwent corpectomies had 28% increased risk of having a major neurophysiologic alert compared with those who had discectomies. Diagnosis of cervical spondylotic myelopathy or trauma increased the risk of having a major neurophysiologic alert 30% and 76%, respectively, compared with cervical radiculopathy. Eight surgeries were aborted due to persistent tceMEP/SSEP amplitude loss, but none resulted in new postoperative neurologic deficits. Two patients had halo-vest applied due to early termination of surgery. One of these patients ultimately could not receive definitive surgical stabilization. Discussion and Conclusion. Diagnosis of cervical spondylotic myelopathy or trauma and cervical corpectomy procedures increase the risk for having major intraoperative alerts. In case of persistent tceMEP/SSEP amplitude loss, consider delaying potentially harmful interventions, such as premature termination of the procedure or methylprednisolone infusion, until a new neurologic deficit is verified with an awake-clinical examination.