Relationship of a "Fundal Fluid Cap" and Vestibular Schwannoma Volume: Analysis of Preoperative Radiographic Findings and Outcomes

Objective: To evaluate the relationship between radiographic fundal fluid cap in the lateral internal auditory canal, preoperative clinical characteristics, and postoperative outcomes in patients with vestibular schwannoma who underwent microsurgical excision. Study Design: Retrospective chart review. Setting: Academic tertiary referral center. Patients: Thirty-six consecutive patients (mean age 49.4 yr [range 29-74]) who underwent microsurgical vestibular schwannoma excision. Interventions: Microsurgical excision. Main Outcome Measures: Linear fundal fluid size and tumor size calculated using volumetric analysis were measured on preoperative magnetic resonance imaging, and correlated to hearing status and postoperative facial nerve function. Results: Mean fundal fluid size was 2.18 mm (range 0-7.32). Mean tumor volume was 5.58 cm³ (range, 0.210-40.3 cm³). Short- and long-term postoperative House-Brackmann scores were 2.4 and 1.4, respectively. Fundal fluid size was associated with tumor volume (r_s = 0.488, p = 0.003) but not preoperative hearing status (p = 0.333). The presence of fundal fluid and larger tumor volumes were statistically associated with poorer short-term and long-term postoperative facial nerve function (p < 0.05). Conclusions: Radiographic fundal fluid size is correlated to tumor volume.