Fundal Fluid CAP is Associated with Short-Term Hearing Preservation in the Radiosurgical Treatment of Vestibular Schwannoma

Objective: The aim is to study the association between the fluid fundal cap and hearing preservation after gamma knife radiosurgical (GKRS) treatment of vestibular schwannoma (VS).

Study Design: Retrospective chart review.

Setting: Tertiary referral center.

Patients: Patients treated with GKRS for VS between March 2007 and March 2017. The diagnosis of VS was based on the clinical presentation and the typical radiological tumor appearance. Exclusion criteria included pretreatment PTA above 90 dB, neurofibromatosis type II, and follow-up less than 1 year.

Intervention(s): Therapeutic.

Main Outcome Measure(s): AAO-HNS guidelines for reporting hearing results in patients pre-GKRS and post-GKRS for VS were followed, including patient stratification into AAO-HNS Classes A-D. Pure-tone average (PTA) was calculated using thresholds at 0.5, 1, 2, and 3 kHz.

Results: Of the 137 patients included in the study, 47 had class A hearing, 37 had class B hearing,19 had class C hearing, and 34 had class D hearing. Within each class the 1-, 2-, and 3-year hearing preservation rates were as follows: 75, 58, and 52% among class A; 75, 61, and 30% among class B; 89, 75, and 60% among class C; and 82, 66, and 61% among class D. Analysis revealed the presence of a fundal cap is associated with short-term hearing preservation according to Kaplan–Meier method with log-rank testing. However, [Fig. 1] reveals the long-term mean change in PTA did not differ between patients with and without a fundal fluid cap on pretreatment MRI.

Conclusion: The presence of a fundal fluid cap on pretreatment MRI is predictive of short-term hearing preservation in patients undergoing Gamma Knife radiosurgery for vestibular schwannoma.

Fig. 1 Kaplan–Meier actuarial curves showing maintenance of serviceable hearing (n = 65) (A) and hearing preservation (n = 104) (B) according to fundal cap presence.