Surgical outcomes and functional morbidity after retrosigmoid/retrocondylar and midline suboccipital approaches for foramen magnum meningiomas: a single-arm meta-analysis

Abstract Foramen magnum meningiomas (FMMs) are surgically challenging due to their proximity to the cervicomedullary junction, lower cranial nerves, and vertebrobasilar circulation. Although far-lateral transcondylar approaches are commonly used for ventral lesions, less extensive posterior/posterolateral corridors are increasingly employed. We performed a single-arm meta-analysis to quantify oncologic control and functional morbidity following retrosigmoid/retrocondylar and midline suboccipital approaches for FMMs. A PRISMA-guided systematic review was conducted using PubMed/MEDLINE, Embase, Scopus, and Web of Science from inception through July 2025 (last search 31 July 2025). Eligible studies were original clinical case series with ≥ 5 patients (all eligible series proved retrospective) reporting FMM resection via posterior midline suboccipital or lateral/posterolateral suboccipital corridors, including retrosigmoid/retrocondylar approaches with limited condyle drilling ≤ 1/3 when performed. Studies with nonseparable outcomes from more extensive transcondylar/far-lateral approaches were excluded. Pooled proportions were calculated using a random-effects model with Freeman–Tukey transformation and reported with 95% confidence intervals. Seven retrospective case series from 1997 to 2019 contributing 133 eligible patients were included; one series was restricted to its 34 intradural cases operated through eligible corridors. Weighted mean age was 54.4 years, 75.2% (100/133) were female, and sample-size-weighted mean follow-up was 58 months. Retrosigmoid/retrocondylar corridors were used in 74/133 patients (55.6%) and midline suboccipital craniectomy in 59/133 (44.4%), often with C1 laminectomy. Dedicated retrosigmoid/retrocondylar series included predominantly anterior/anterolateral tumors, whereas midline series included mixed attachments. Formal approach-specific comparisons were limited by heterogeneous reporting. When performed, condyle drilling was generally limited to the posterior one-third; no postoperative craniocervical instability or fusion was reported. Pooled gross total resection was 91% (95% CI: 84–96%; 119/133 patients, 7 studies), recurrence was rare (3/133, 2.3%; pooled 1%, 95% CI: 0–4%), and long-term functional independence was 83% (95% CI: 71–93%; 60/74 patients, 5 studies). New cranial nerve deficits, transient or permanent, occurred in 21% (95% CI: 13–30%; 22/99 patients, 6 studies), cerebrospinal fluid leak in 12% (95% CI: 6–20%; 13/99, 6 studies), and perioperative mortality in 3% (95% CI: 0–9%; 7/133, 7 studies), with two additional late deaths from aspiration pneumonia during follow-up. Taken together, retrosigmoid/retrocondylar and midline suboccipital approaches for FMMs achieve high resection rates, low recurrence, and favorable long-term function, often without extensive condylectomy. These pooled estimates represent a combined figure across two anatomically distinct corridors applied to topographically different tumors (retrosigmoid/retrocondylar routes predominantly for anterior/anterolateral lesions and midline suboccipital exposure predominantly for posterior/posterolateral lesions), and do not imply that the approaches are interchangeable. Cranial nerve morbidity, cerebrospinal fluid leak, and perioperative mortality remain important considerations.