Intraoperative neurophysiological monitoring versus no monitoring in intradural extramedullary tumor surgery: a systematic review and meta-analysis of early postoperative neurological outcomes

The role of intraoperative neurophysiological monitoring (IONM) in intradural extramedullary (IDEM) tumor surgery is uncertain. While IONM is standard in intramedullary and deformity procedures, its impact on neurological outcomes in IDEM resections has not been systematically evaluated. To assess whether IONM reduces early postoperative neurological morbidity in IDEM tumor surgery. We conducted a PROSPERO-registered systematic review and meta-analysis (CRD420251119538) in accordance with PRISMA 2020. Comparative studies of IDEM resections with versus without IONM were included. Outcomes were harmonized into a binary "new neurological deficit" at discharge. Risk of bias was assessed with ROBINS-I, and certainty of evidence with GRADE. Pooled odds ratios (ORs) were calculated using a random-effects model. Four retrospective cohorts comprising 602 patients (306 with IONM, 296 without) were analyzed. In absolute terms, early postoperative neurological deficits occurred in 19/306 patients (6.2%) in the IONM group versus 45/296 patients (15.2%) in the non-IONM group. Pooled analysis showed a significant reduction in early postoperative neurological deficits with IONM compared to no IONM group (OR 0.39, 95% CI 0.20-0.75; p = 0.005; I² = 22%), corresponding to an absolute risk reduction of 9.2% (NNT ≈ 11). Sensitivity analysis revealed dependence on certain large studies. Risk of bias was moderate-to-serious, and certainty of evidence was rated low. IONM use was associated with lower odds of early postoperative neurological deficits in IDEM tumor surgery, and the effect is based on low-certainty observational evidence. These findings are hypothesis-generating and support selective rather than universal use of IONM, particularly in higher-risk cases. Prospective multicenter studies with standardized outcomes, longer follow-up, and cost-effectiveness analyses are needed to define its optimal role.