Hearing Preservation Following Gamma Knife Radiosurgery of Vestibular Schwannomas

Abstract

Between January 1998 and March 2000, 28 patients with unilateral vestibular schwannomas received stereotactic gamma knife radiosurgery (GKR) at the Chiba Cardiovascular Center. Patients' age ranged from 29 to 81 years (medians=59). 15 patients underwent prior surgical resection. Median follow-up period was 13.3 months (range: 3-30 months). Tumor volume was measured by Gamma Plan using MRI. Tumor volume ranged from 257 to 10100mm³. The pure-tone auiometry and speech discrimination test were performed before GKR. Post-GKR, tumor volume measurement and audiometric testing were undertaken every 3 months in a year, then every 6 months. 17 of 28 patients have lost their hearing before GKR by tumor itself or prior surgery, and none of them was improved after GKR. In one patient, who had serviceable hearing before GKR, lost his hearing at 6 months. In two patients, hearing was gradually deteriorating in spite of the reduction of tumor volume. Hearing improvement occurred in 2 patients at 3 to 6 months. Preservation of some measurable hearing was obtained in 10 of 11 patients (90.9%), however, serviceable hearing was preserved in 3 of 5 patients (60%). The change of tumor volume did not correlate to hearing change.