The Japanese Society for Spine Surgery and Related Research published a prospective multicenter spinal intraoperative monitoring (IOM) study conducted across 18 institutions with 959 patients undergoing surgery for deformity correction, ossification of the posterior longitudinal ligament, or tumor resection between 2010-2012. Standardized transcranial motor evoked potential (TcMEP) monitoring was undertaken for all cases under total intravenous anesthesia. A 70% reduction in TcMEP amplitude was pre-set as the threshold for significance (designated as the ‘alarm point’). The monitoring protocol yielded high sensitivity and negative predictive value (95% and 99.7%, respectively) and a specificity of 91% and positive predictive value of 32.8% were noted. Although a relatively higher proportion of false-positive cases at the 70% threshold was noted, only 2 false-negatives occurred during the prospective evaluation (both involving intramedullary tumor resections). The 70% TcMEP threshold value likely represents the most valid intraoperative measure of associated neurological worsening.
Journal of Neurosurgery