Multimodal Intraoperative Neurophysiological Monitoring in Spinal Cord Surgery

Intraoperative neurophysiological monitoring (IONM) monitors the functional integrity of critical neural structures by electrophysiological methods during surgery. Multimodality combines different neurophysiological methods to maximize diagnostic efficacy and provide a safety margin to improve the outcomes of spinal surgery. Our aim was to share our intraoperative monitoring experiences with patients who underwent surgery because of spinal cord pathologies between September 2013 and January 2015.

We had twenty-six cases. Location of the lesions, surgery, neurological findings, and electrophysiological findings intraoperatively and postoperatively were documented.

The combination of motor evoked potential (MEP), somatosensorial evoked potential (SSEP), free-run and trigger electromyography (EMG) were performed according to lesion localization. MEPs plus SSEPs were run in 23 patients and MEPs with triggered EMG were performed in 4 patients. In only one patient, optimal recording could not be elicited because of technical problems. MEP and SSEP changes were recorded in 12 and 3 patients respectively. Postoperative neurological deficits were observed in 2 patients. Deficits were transient in one case and permanent in the other. While baseline MEP responses were either absent or low amplitude ( < 50 microvolt) in 7 patients, following resection they were either visible or increased in amplitude. Surgery was ended in one patient with C7-T2 intramedullary tumour after the right distal MEP response disappeared.

Multimodal IONM is an important method to monitor the neural structures under risk in spine surgery and to keep the surgery within safety limits, especially for intramedullary spinal cord lesion surgery.