Facial nerve preservation following gamma knife radiosurgery for vestibular schwannomas in neurofibromatosis type 2: a systematic review and meta-analysis of 552 tumors.

Facial nerve injury is a known possible complication in patients undergoing gamma knife radiosurgery (GKRS) for vestibular schwannoma (VS) in neurofibromatosis 2 (NF2). However there exists considerable heterogeneity in reported outcomes. Here we perform a systematic review of the literature and meta-analysis to evaluate the rate of facial nerve preservation across studies and to help identify predictive factors associated with facial nerve neuropathy in patients undergoing GKRS for NF2-associated VS. A systematic review was conducted on PubMed to assess all studies related to facial nerve preservation following GKRS for VS in patients with NF2 until November 2024. Meta-analysis was performed using SPSS version 20 (IBM Corp.). A total of 10 studies with 552 tumors and 405 patients were included in the analysis. The mean age of patients was 32 years. The mean tumor volume ranged from 1.5 cm3 to 15 cm3 and the mean median marginal dose of radiation used was 12.6 Gy. Facial nerve function was preserved after GKRS for 502/552 tumors (91%, 95% CI 83%—98%, p < 0.001) over mean durations ranging from 26.6 to 91.2 months. Mean Median Marginal dose had a significant moderate correlation with facial nerve preservation rates (r = -0.71, p = 0.01). GKRS has demonstrated superior facial nerve preservation rates in comparison to microsurgical resection as per historical data, affirming its accurate role in maintaining facial function. Although a dose of < 13 Gy could achieve higher preservation rates, larger future studies are warranted to identify the cut off for marginal doses and direct comparative studies between surgical and GKRS cohorts.