Polymethyl Methacrylate Augmentation is Associated with Reduced Cerebrospinal Fluid Leak After Supratentorial Craniotomy: A Retrospective Cohort Study

Purpose Cerebrospinal fluid leakage is a frequent complication following craniotomy, associated with morbidity, prolonged hospitalization, and increased healthcare costs. This study aimed to evaluate whether augmentation of craniotomy closure with polymethyl methacrylate reduces postoperative CSF leak rates compared to conventional closure techniques in supratentorial cases. Methods We performed a retrospective, single‑center cohort study including consecutive adult patients who underwent supratentorial craniotomy between January 2018 and August 2024. Beginning in September 2020, PMMA augmentation was routinely applied to fill residual interosseous gaps after bone‑flap fixation, enabling a temporal cohort comparison. The primary endpoint was CSF leakage within 12 months. Multivariate logistic regression was used to identify independent predictors while accounting for potential confounders related to patient characteristics, pathology, and surgical variables. Results A total of 186 patients were analyzed (135 PMMA; 51 no PMMA). CSF leakage occurred in 9 patients (4.8%). Leakage was less frequent in the PMMA group (2.2% vs. 11.8%, p = 0.014), corresponding to an absolute risk reduction of 9.6% and a number‑needed‑to‑treat of approximately 10. PMMA use remained independently associated with lower leak risk (OR 0.17, 95% CI 0.03–0.92, p = 0.039). No increase in wound complications, shunt procedures, or readmissions attributable to PMMA was observed. Conclusion PMMA augmentation during supratentorial craniotomy closure was associated with a reduced rate of postoperative CSF leakage without evidence of added morbidity. These findings suggest that gap‑filling augmentation may represent a useful adjunct in selected patients; however, prospective multicenter validation is warranted.