Neuromonitoring in Cervical Spine Surgery: When Is a Signal Drop Clinically Significant?

• Published in: Asian spine journal Vol. 15; no. 3; pp. 317 - 323
• Main Authors: Decruz, Joshua, Kaliya-Perumal, Arun-Kumar, Wong, Kevin Ho-Yin, Kumar, Dinesh Shree, Yang, Eugene Weiren, Oh, Jacob Yoong-Leong
• Format: Journal Article
• Language: English
• Published: Seoul Korean Society of Spine Surgery 01.06.2021; Korean Spine Society; 대한척추외과학회
• Subjects: Anesthesia; Back surgery; Bone surgery; Central nervous system diseases; cervical vertebrae; Clinical significance; Clinical Study; Electrodes; electrophysiological phenomena; false positive reactions; intraoperative complications; Medical records; Motor evoked potentials; Neurological diseases; Paralysis; Patients; Risk factors; Somatosensory evoked potentials; Spinal cord; spine; Spine (cervical); Surgeons; 정형외과학; United States > US
• ISSN: 1976-1902; 1976-7846
• DOI: 10.31616/asj.2020.0074

Study Design: Retrospective cohort study.Purpose: To identify the clinical significance of different patterns of intraoperative neuromonitoring (IONM) signal alerts.Overview of Literature: IONM is a long-established valuable adjunct to complex spine surgeries. IONM for cervical spine surgery is in the form of somatosensory evoked potential (SSEP) and motor evoked potential (MEP). The efficacy of both modalities (individually or in combination) to detect clinically significant neurological compromise is constantly being debated and requires conclusive suggestions.Methods: Clinical and neuromonitoring data of 207 consecutive adult patients who underwent cervical spine surgeries at multiple surgical centers using bimodal IONM were analyzed. Signal changes were divided into three groups. Group 0 had transient signal changes in either MEPs or SSEPs, group 1 had sustained unimodal changes, and group 2 had sustained changes in both MEPs and SSEPs. The incidences of true neurological deficits in each group were recorded.Results: A total of 25% (52/207) had IONM signal alerts. Out of these signal drops, 96% (50/52) were considered to be false positives. Groups 0 and 1 had no incidence of neurological deficits, while group 2 had a 29% (2/7) rate of true neurological deficits. The sensitivities of both MEP and SSEP were 100%. SSEP had a specificity of 96.6%, while MEP had a lower specificity at 76.6%. C5 palsy rate was 6%, and there was no correlation with IONM signal alerts (p=0.73).Conclusions: This study shows that we can better predict its clinical significance by dividing IONM signal drops into three groups. A sustained, bimodal (MEP and SSEP) signal drop had the highest risk of true neurological deficits and warrants a high level of caution. There were no clear risk factors for false-positive alerts but there was a trend toward patients with cervical myelopathy.