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

Background/Objectives: Expanded endoscopic endonasal approaches (EEAs) 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 EEAs 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: After full-text eligibility assessment, 48 reports were retained in the extraction-status set. Three strictly adult-only exact-count reports contributed to the primary CSF leak meta-analysis, yielding a random-effects incidence of 23.0% (95% CI, 10.5–43.1%; I2 = 78.7%). A sensitivity analysis adding one mixed-age cohort yielded 23.8% (95% CI, 14.5–36.6%; I2 = 68.9%), while a broader sensitivity analysis including both mixed-age reports yielded 21.1% (95% CI, 12.2–33.8%; I2 = 69.4%). Meningitis was reported in 6/166 patients across four studies (3.6%; 95% exact CI, 1.3–7.7%), and new neurological deficit/vascular injury/stroke was reported in 4/166 patients across four studies (2.4%; 95% exact CI, 0.7–6.1%). Postoperative seizures were reported in 4/652 patients across two studies (0.6%; 95% exact CI, 0.2–1.6%). Large mixed EEA cohorts were summarized separately because adult intradural tumor subsets could not be separated. Conclusions: CSF leak was the most consistently reported complication after expanded EEAs for adult intradural skull base tumors. The strict adult-only random-effects estimate was 23.0%, but it was based on only three studies and showed substantial heterogeneity, limiting its generalizability. Meningitis, neurological/vascular events, and seizures were uncommon in the extractable data and were summarized descriptively rather than being meta-analyzed. Large mixed EEA cohorts provide important safety context but cannot substitute for standardized adult intradural, pathology-specific reporting.