Binary 5-Aminolevulinic Acid Classification Integrated With Simpson Grading in Meningioma Surgery: A Single-Center Retrospective Series of 265 Cases.

Abstract

Strategies to improve extent of resection (EOR) in meningioma surgery have evolved since Simpson grading. While 5-aminolevulinic acid (5-ALA) fluorescence-guided surgery is standard in malignant gliomas, its systematic integration into meningioma Simpson grading remains undefined. We aimed to characterize intraoperative fluorescence patterns in a large single-center series and evaluate a simple, binary 5-ALA classification to complement the Simpson grade. We retrospectively analyzed 265 meningiomas (244 patients, 2018-2025) with 5-ALA fluorescence-guided surgery. Intraoperative fluorescence was dichotomized. For 5-ALA-positive tumors, the resection cavity was classified as "5-ALA tumor-free" or "5-ALA residual mass" (visible nodular fluorescence, including dura presenting as a mass). Surrounding structures were classified as "tissue-free" or "residual fluorescent tissue" (visible fluorescence on macroscopically normal tissue). Associations with 5-ALA status, Simpson grade, MRI-based EOR, World Health Organization grade, location, and recurrence were assessed. Overall, 254 of 265 meningiomas (95.8%) were 5-ALA-positive. The tumor bed was 5-ALA tumor-free in 216 of 254 cases (85.0%) and showed residual fluorescent mass in 38 of 254 cases (15.0%). Residual fluorescent tissue in surrounding structures was observed in 157 of 254 tumors (61.8%), predominantly in convexity, parasagittal/falx, and posterior fossa/tentorial locations. 5-ALA residual mass was independent of World Health Organization grade but strongly associated with Simpson grade (7.5% of Simpson I-II vs 80.8% of Simpson III-IV resections) and MRI-based EOR (7.0% of MRI-complete vs 81.5% of MRI-incomplete resections, both P < .0001). Nineteen recurrences were observed. These observations suggest a simple, binary 5-ALA classification (residual fluorescent mass and residual tissue fluorescence) can be incorporated as a descriptive adjunct to the Simpson grade. It provides a structured intraoperative EOR description suitable for routine documentation and future prospective validation.