Complications Spectrum Following Expanded Endoscopic Endonasal Surgery for Intradural Skull Base Tumors: A Systematic Review and Meta-Analysis

Background/Objectives: Expanded endoscopic endonasal approaches (EEA) provide direct ventral access to adult intradural skull base tumors; however, postoperative complications are variably defined and reported in the literature. This review aimed to synthesize the overall spectrum of adult intradural EEA complications and distinguish pathology-specific evidence from large mixed EEA complication cohorts. Methods: A PRISMA 2020 systematic review and meta-analysis searched PubMed/MEDLINE, Embase, and Web of Science from database inception through July 2026. Eligible studies included adults or adult-separable subgroups undergoing expanded EEA for intradural skull base tumors. The primary outcomes were CSF leak, meningitis or intracranial infection, new neurological deficit or vascular injury/stroke, hydrocephalus, mortality, and postoperative seizures. Pathology-specific adult intradural series with exact counts were quantitatively synthesized when appropriate, and large mixed EEA cohorts were summarized separately when the eligible subgroup was not separable. Results: The full-text screening set included 48 reports. Five exact-count reports, including one mixed-age contextual report, contributed to the CSF leak meta-analysis and yielded a random-effects incidence of 21.1% (95% CI, 12.2%-33.8%; I² = 69.4%). Excluding the mixed-age reports yielded 23.8% (95% CI, 14.5%-36.6%). Meningitis was reported in 6/166 patients (3.6%; 95% exact CI, 1.3%-7.7%), and new neurological deficit/vascular injury/stroke in 4/166 (2.4%; 95% exact CI, 0.7%-6.1%); these rare outcomes were summarized descriptively without continuity correction. Postoperative seizures were reported in 4/652 patients (0.6%) in two studies. Large mixed EEA cohorts have reported CSF leak rates of 1.6%-15.9% but these were not pooled because adult intradural tumor subsets were not separable. Conclusion: CSF leak was the most consistently reported complication after expanded EEA for adult intradural skull base tumors; however, its incidence varied substantially across pathologies and centers. Meningitis, neurological/vascular events, and seizures were uncommon in the extractable data and were better interpreted descriptively than as precise pooled rates. Large mixed EEA cohorts provide important safety context but cannot substitute standardized adult intradural, pathology-specific reporting.