S168. Intraoperative neurophysiologic monitoring in spinal cord lesions: from the experimental study to the operating room

Introduction Multimodal intraoperative neurophysiologic monitoring (IONM) is considered compulsory in spine surgeries which represent a risk for the spinal cord. Nevertheless, the approach when facing an intraoperative acute spinal cord injury depends critically on the possibility of monitoring the function of the non-affected spinal cord. This is not usually possible with the standard IONM techniques if the injury is severe. In previously reported experimental studies, we have found that it is possible to monitor spinal cord segments cranial and caudal to the level of an acute spinal cord injury using epidural electrodes. Methods We present two cases of surgical correction of secondary scoliosis. Results In both cases, there was an intraoperative spinal cord injury during the instrumentation, which was detected by loss of the myogenic transcranial motor evoked potentials (TcMEPs) caudal to the intercostal thoracic muscles and loss of the lower limb somatosensory evoked potentials (SSEPs). The level of spinal cord damage was identified and confirmed by a combined use of spinal cord recorded SSEPs and D waves. Two epidural recording electrodes were placed, one cranial and one caudal to the level of the lesion. In both cases, the spinal cord SSEPs were absent above the lesion but present below. D-waves were present above the lesion and absent below. In these cases, during the remainder of the surgery, we used epidural SSEPs for monitoring of spinal cord function caudal to the lesion and D-wave for the levels cranial to the lesion. Additionally, we performed the spinal cord-to-spinal cord evoked potentials (stimulating proximally and recording distally to the lesion using the epidural electrodes), demonstrating a reproducible potential, which remained stable throughout the remainder of surgery. Conclusion Our results indicate that spinal cord monitoring using epidural electrodes in patients with acute intraoperative spinal cord lesions facilitates identification and confirmation of the level of spinal cord injury, allows the surgeon to continue with the instrumentation in those cases necessary, and can help establish a postoperative prognosis.