Does a "fundal Fluid Cap" Predict Successful Hearing Preservation in Vestibular Schwannoma Resections Via the Middle Cranial Fossa Approach?

Objective: To determine the association between radiographic cerebrospinal fluid (CSF) cap in the lateral internal auditory canal (IAC) and likelihood of successful hearing preservation in middle cranial fossa (MCF) vestibular schwannoma (VS) surgery. Study Design: Retrospective chart review. Setting: Academic tertiary referral center. Patients: One hundred thirty-eight consecutive patients (mean age/standard deviation, SD, 50/11 yr) who underwent MCF VS resection. Interventions: MCF VS excision. Main Outcome Measures: Size of fundal fluid cap on preoperative magnetic resonance imaging (MRI), pre- and postoperative pure-tone average (PTA), and word recognition score (WRS). Results: Mean tumor and fundal fluid sizes were 9.7 mm (SD, 3.9 mm) and 2.8 mm (SD, 1.7 mm), respectively. On bivariate analysis, fundal fluid size was associated with larger tumor size (p = 0.005) but not changes in postoperative PTA (p = 0.45) or WRS (p = 0.17). When fundal fluid size was stratified as none (<1 mm), small (≥1 mm and <4 mm), and large (≥4 mm), no significant differences were seen in rates of hearing preservation. Using multivariate linear regression models adjusting for patient age, sex, tumor nerve of origin, neurofibromatosis type II status, and preoperative PTA and WRS, superior vestibular nerve tumor origin but not increasing fundal fluid size was associated with preserved postoperative PTA or WRS. Conclusions: Presence or size of CSF fluid cap may not be a reliable prognostic indicator for hearing preservation in MCF VS resection, with important implications for patient counseling.