Analysis of Multimodal Intraoperative Monitoring During Intramedullary Spinal Ependymoma Surgery

Objective To evaluate the validity of intraoperative somatosensory-evoked potential (SSEP) and motor-evoked potential (MEP) monitoring according to 2 different warning criteria during 6 months from intramedullary spinal ependymoma surgery. Methods Twenty-six patients who underwent intramedullary spinal ependymoma surgery with intraoperative monitoring from January 2010 to June 2017 were retrospectively analyzed. We examined the sensitivity, specificity, positive predictable value, negative predictable value, and diagnostic odds ratio of SSEP and MEP monitoring for each extremity according to 2 warning criteria: 50% decline and all-or-none. The postoperative motor deficit was evaluated using the Medical Research Council scale. The postoperative neurologic deficit was followed up during 6 months. Results Eighty-six extremities were evaluated. The success rates of SSEP and MEP monitoring were 84.9% and 83.7%, respectively. Indeterminate cases were 1 in SSEP and 6 in MEP. All-or-none criterion in SSEP and MEP monitoring showed greater specificity, positive predictable value, and diagnostic odds ratio than 50% decline criterion during 6 months. The validity of SSEP was high in the upper extremity, whereas that of MEP was high in the lower extremity. During the follow-up, 37 of 38 extremities (97.4%) and 18 of 29 extremities (62.1%) showed improvement in sensory and motor deficit, respectively. Seven indeterminate cases also showed good clinical outcomes. Conclusions Many false-positive and false-negative results of SSEP and MEP monitoring occurred during the immediate postoperative period. All-or-none criterion was more beneficial for assessing postoperative neurologic status than 50% decline criterion. This trend was maintained until 6 months after surgery.