Prognostic factors of hearing preservation after gamma knife radiosurgery for vestibular schwannoma.

We conducted a prospective study to identify prognostic factors of hearing preservation after gamma knife radiosurgery (GKRS) for vestibular schwannoma (VS). Twenty-seven patients with unilateral VS and serviceable hearing underwent GKRS. The mean lesion diameter was 17.3mm (range 6.1-30.0mm), the median marginal dose was 12 Gy (11-15 Gy), and the mean follow-up duration was 35.7 months (9-81 months). The probabilities of hearing preservation after GKRS were calculated using the Kaplan-Meier method. Tumor growth was controlled in 26 of the 27 patients (96.3%), and rates of hearing preservation were 85.1% and 68.1% at 2 and 3 years, respectively. A normal auditory brainstem response (ABR) (p = 0.008) and Gardner-Robertson class I hearing (p = 0.012) before GKRS were found to be significant prognostic factors of a favorable outcome. Our findings suggest that a normal pre GKRS ABR strongly predicts hearing preservation after GKRS. Accordingly, we advise that ABR should be considered with other prognostic factors when GKRS is considered in patients with VS.