Effect of intraoperative neuromonitoring changes and post-operative neurological deficits on long-term survival in patients with high-grade gliomas: A retrospective analysis

High-grade glioma (HGG) resection requires balancing maximal tumor removal with preservation of neurological function. While intraoperative neurophysiological monitoring (IONM) and post-operative neurological deficits (PDs) have each been associated with functional outcomes, their role in predicting long-term survival remains unclear. This study investigates whether significant IONM changes and PDs are independently associated with survival following HGG surgery. We retrospectively analyzed 224 patients who underwent HGG resection with multimodal IONM at a single institution between 2019 and 2023. Patients were stratified into four groups based on the presence or absence of significant IONM changes and PDs. Kaplan–Meier survival curves and Cox proportional hazards models were used to evaluate associations with 24-month survival. Models were adjusted for age, gender, preoperative Karnofsky Performance Status (KPS), and baseline neurological deficits. Patients with IONM changes only had the highest 24-month mortality rate (72.7%), followed by those with both IONM changes and PDs (55.9%). Kaplan–Meier analysis showed significantly worse survival in the IONM-only group compared to those with neither exposure (p = 0.004). Adjusted Cox regression confirmed that IONM changes alone were independently associated with increased mortality (HR 3.94, 95% CI 1.69–9.21). Tumor characteristics including tumor size, location, and eloquence were comparable across groups. Significant IONM changes during HGG surgery are associated with decreased long-term survival, even in the absence of post-operative deficits. These findings suggest that IONM changes may serve as early intraoperative prognostic markers, providing additional value beyond functional preservation in guiding surgical decisions and post-operative counseling.