Long-term Outcomes of Gamma-Knife Radiosurgery for Intracanalicular Vestibular Schwannomas

Abstract

Objective: Intracanalicular vestibular schwannomas (IVS) constitute a small percentage of all vestibular schwannomas (VS). Hearing preservation is one of the most important goals in IVS management. The aim of this study was to delineate the long-term outcomes of gamma-knife radiosurgery (GKR) for IVS regarding tumor control and hearing preser- vation. Methods: Patients with IVS who were irradiated at our Gamma-Knife Radiosurgery Center between January 2010 and January 2020 with clinical, audiometric, and radiological follow-up were included in this retrospective study. Tumor control was evaluated with magnetic res- onance imaging by tumor dimensions. Hearing status was classified according to Gardner– Robertson (GR) classification system. Results: Tumor control was achieved in 44 of 45 eligible patients by dimensional measuring (97.8%), and the remaining patient did not require further treatment (2.2%). In 29 patients who had functional hearing (GR grades I and II), only 13 patients preserved their functional hearing with a mean of 70.42 months follow-up (44.8%). A GR grade loss in hearing was correlated with a high GR grade preoperatively (Rs=0.459, p=0.002). Treatment dose was also found to be correlated with hearing loss, and higher doses resulted in worse outcomes (Rs=0.459, p=0.002). Conclusion: GKR has excellent results on tumor control on long-term follow-up in IVS. Follow-up duration over 5 years may diminish functional hearing preservation rates, and more studies are needed with long-term follow-up to clarify the actual course of hearing status after GKR in IVS.