Fundal fluid cap is associated with hearing preservation in the radiosurgical treatment of vestibular schwannoma

Objective: To evaluate the relationship between fundal fluid and hearing outcomes after treatment of vestibular schwannoma (VS) with Gamma Knife radiosurgery (GKRS). Study Design: Retrospective case series. Setting: Tertiary neurotology referral center. Patients: Patients treated with GKRS for vestibular schwannoma between March 2007 and March 2017 were considered for this study. Exclusion criteria included pretreatment puretone average (PTA) >90 dB, neurofibromatosis type II, history of previous surgical resection, and follow-up less than 1 year. Main Outcome Measure(s): Hearing function was assessed both by preservation of serviceable hearing and by preservation of baseline hearing (≤20 dB change in PTA) after GKRS. Hearing preservation comparisons were made between groups of patients with and without a fundal fluid cap. Results: Patients with a fundal cap had significantly higher rates of baseline hearing preservation (≤20 dB change in PTA) according to Kaplan-Meier survival analysis of all 106 patients ( p=0.006). By the 3rd year posttreatment, 70.9% of patients with a fundal cap had maintained a ≤20 dB change in PTA, while only 43.6% of patients without a fundal fluid cap achieved this outcome ( p=0.004). Conclusions: Fundal fluid present on pretreatment magnetic resonance imaging is predictive of improved baseline hearing preservation rates in patients undergoing GKRS for vestibular schwannoma when considering all patients with PTA ≤90 dB. Fundal fluid cap presence may serve as a favorable prognostic indicator to help set hearing expectations and guide patient selection efforts.