Intraoperative Neuromonitoring (IONM): Is There a Role in Metastatic Spine Tumor Surgery?

STUDY DESIGN: A retrospective design. OBJECTIVE: We aim to report our experience with multimodal intraoperative neuromonitoring (IONM) in metastatic spine tumor surgery (MSTS). SUMMARY OF BACKGROUND DATA: IONM is considered as standard of care in spinal deformity surgeries. However, limited data exist about its role in MSTS. METHODS: A total of 135 patients from 2010 to 2017, who underwent MSTS with IONM at our institute, were studied retrospectively. After excluding seven with no baseline signals, 128 patients were analyzed. The data collected comprised of demographics, pre and postoperative American Spinal Injury Association (ASIA) grades and neurological status, indications for surgery, type of surgical approach. Multimodal IONM included somatosensory-evoked potentials (SSEPs), transcranial electric motor-evoked potentials (tcMEP), and free running electromyography (EMG). RESULTS: The 128 patients included 61 males and 67 females with a mean age of 61 years. One hundred sixteen underwent posterior procedures; nine anterior and three both. The frequency of preoperative ASIA Grades were A = 0, B = 0, C = 10, D = 44, and E = 74 patients. In total, 54 underwent MSTS for neurological deficit, 66 for instability pain, and 8 for intractable pain.Of 128 patients, 13 (10.2%) had significant IONM alerts, representing true positives; 114 true negatives, one false negative, and no false positives. Among the 13 true positives, four (30%) underwent minimally invasive and nine (70%) open procedures. Eight (69.2%) patients had posterior approach. Seven (53.84%) true positive alerts were during decompression, which resolved to baseline upon completion of decompression, while five (38.46%) were during instrumentation, which recovered to baseline after adjusting/downsizing the instrumentation, and one (8.3%) during lateral approach, which reversed after changing the plane of dissection. Of the seven patients without baseline, five were ASIA-A and two were ASIA-C. The sensitivity, specificity, positive, and negative predictive values were 99.1%, 100%, 100%, and 92.9%, respectively. CONCLUSION: Multimodal IONM in MSTS helped in preventing postoperative neurological deficit in 9.4% of patients. Its high sensitivity and specificity to detect intraoperative neurological events envisage its use in ASIA-grade D/E patients requiring instrumented decompression. LEVEL OF EVIDENCE: 3.