IMG-08. Peritumoral edema volume in meningiomas directly correlates with tumor-cortex plane dissection:A prospective analysis of 100 consecutive patients

BACKGROUND Peritumoral edema plays a crucial role in the surgical dissection of meningiomas, influencing the tumor-cortex interface and affecting surgical and neurological outcome. While advanced MRI sequences have been used to assess tumor consistency and vascularity, no imaging modality has reliably predicted the tumor adherence to the pial surface. This study evaluates edema volume as a predictor for the difficulty level of the dissection. METHODS A prospective analysis was conducted on 100 consecutive patients undergoing meningioma resection. Tumor boundary assessments included perfusion-weighted imaging, time-of-flight (TOF), and other MRI metrics. Dissection planes were classified as subpial, mixed, or extrapial. Statistical analyses included Mann-Whitney U and ROC curve analyses to determine edema’s predictive value for surgical resection feasibility. RESULTS Edema volume emerged as the first and only imaging measure to reliably predict the complexity of surgical cleavage plane (p = 0.006). Patients with lower edema volumes were more likely to have an extrapial dissection plane, while increased edema correlated with a mixed or subpial infiltration. ROC analyses demonstrated significant edema-based thresholds for tumor margin predictability, with an AUC of 0.800 (sensitivity = 100%, specificity = 55% > 121.5). Perfusion-based measures (AUC = 0.769) and vascularity assessments (AUC = 0.789) provided insight into tumor consistency but failed to correlate with the actual surgical plane. The three different dissection grades showed significant differences in edema volumes, with extrapial cases having the least edema and subpial cases showing the highest values (p < 0.01). MRI sequences assessing tumor consistency and vascularity did not correlate with the tumor-cortex boundary, confirming the unique predictive value of edema volume. CONCLUSIONS Edema volume is a key factor in determining the difficulty grade of tumor-cortex dissection and is the first imaging parameter identified to predict the tightness of the surgical cleavage plane.