The Final-to-Baseline Amplitude Reduction Ratio of Intraoperative Motor Evoked Potentials Predicts Early Neurological Deficits Following Intradural Extramedullary Tumor Resection

Objective: To evaluate the predictive value of the final-to-baseline amplitude reduction ratio (FBR) of motor evoked potentials (MEP) and somatosensory evoked potentials (SEP) for early postoperative neurological deficits (PNDs) following intradural extramedullary (IDEM) tumor resection, and to explore a candidate prognostic cutoff for intraoperative neurophysiological monitoring (IONM).Methods: A total of 123 consecutive patients who underwent IDEM tumor resection with multimodal IONM were retrospectively analyzed. Early PND was defined as ≥1-grade increase in the modified McCormick scale at 1 month postoperatively. MEP and SEP FBRs were calculated and analyzed using multivariable logistic regression and receiver operating characteristic (ROC) curve analysis.Results: Early PND occurred in 26.02% (32 of 123) of patients. Multivariable regression identified MEP FBR as the sole independent predictor of early PND (odds ratio, 1.064; 95% confidence interval, 1.040–1.088; p<0.001). ROC analysis demonstrated excellent predictive performance with an area under the curve of 0.922 (p<0.001) and an optimal cutoff value of 61.84%. MEP FBR showed a significant graded association with PND severity (p<0.001).Conclusion: Our findings suggest MEP FBR may serve as a promising predictor of early postoperative neurological deficit among patients undergoing IDEM tumor resection. A multimodal IONM strategy centered on MEP monitoring, with SEP as a supplement appears reasonable for IDEM tumor resection. A 60% reduction in MEP amplitude may represent an exploratory prognostic cutoff warranting prospective validation.