Characterization of facial nerve outcomes following radiosurgery for vestibular schwannoma: a meta-analysis.

PURPOSE: Gamma Knife radiosurgery (GKRS) is a precise and efficacious treatment modality for vestibular schwannoma (VS) with favorable cranial nerve preservation rates. This study aims to better characterize facial nerve (FN) outcomes in VS after GKRS. METHODS: A query of six medical databases was conducted following PRISMA guidelines. Eligible studies exclusively reported VS managed with single-fraction GKRS and included House-Brackmann (HB) scale assessments prior to and following GKRS. Data was analyzed using random-effects modeling, and FN preservation was defined as HB I or II at last follow-up. RESULTS: Data was analyzed from 15 articles with 3,155 patients at an mean age of 55.0 years. Mean tumor volume, radiation dose, follow-up, tumor control, and hearing preservation were 4.28 cm(3), 13.3 Gy, 59.4 months, 92.7%, and 62.6%, respectively. The pooled FN preservation rate was 92.9%. Mean preoperative tumor volume > 2.5 cm(3) and age > 60 years were significantly associated with worse preoperative FN function (p = 0.019, p = 0.023, respectively). Normal FN function (HB = 1) at last follow up was 95.8% for VS volume < 2.5 cm(3) and 89.4% with larger volumes (p < 0.001). Doses </= 13 Gy were significantly associated with superior FN preservation (96.5%) compared to higher doses (p < 0.001). Tumor control and hearing preservation were not significantly associated with FN preservation. CONCLUSION: This meta-analysis identifies tumor volume and radiation dose as prognostic factors for FN preservation. A FN preservation rate of 93% may be expected at five years after GKRS. This study provides a unique characterization of FN outcome that should be considered in the management of VS.