What Clinicians Should Consider to Determine a More Beneficial Treatment Strategy for Small to Medium Sized Vestibular Schwannoma With Serviceable Hearing: A Single Surgeon's Long-term Outcome of Microsurgery and Gamma Knife Radiosurgery
Authors: Han Moon-Soo , Jung Shin , Lim Sa-Hoe , Kim In-Young , Moon Kyung-Sub , Jung Tae-Young , Jang Woo-Youl 
Published: June 2020

Objective:
The number of small to medium sized vestibular schwannoma (VS) patients presenting with serviceable hearing has steadily increased. There are various treatment strategies for small to medium sized VS, including microsurgery (MS), gamma knife radiosurgery (GKS), and serial observations using magnetic resonance imaging. In this study, we presented the long-term outcomes of patients with small to medium sized VS with serviceable hearing. We also evaluated the potential prognostic factors for hearing preservation and discussed appropriate treatment strategies.

Methods:
A retrospective review of 504 cases of all VS patients who underwent MS or GKS between 1993 and July 2019 was conducted. Surgical resection was performed on 267 patients using the retro-sigmoid approach and 55 (20.6%) of them were small to medium sized VS. GKS was performed on 237 patients and 175 (73.8%) of them were small to medium sized VS. Small to medium sized VS was defined as less than 25 mm in the greatest dimension. After applying the inclusion and exclusion criteria, 51 patients with small to medium sized VS with serviceable hearing were enrolled in this study and underwent either MS (n = 21) or GKS (n = 30). To define the clinical characteristics of the patients, clinical data at the time of treatment, age, sex, presenting symptoms, tumor location type, preoperative hearing status, posttreatment related complications, recurrence, and hearing loss progression-free survival data were collected.

Results:
In the MS group, the hearing preservation rate was 71.4% and the tumor control rate was 100%. In the GKS group, the tumor control rate was 93.3% and two patients experienced recurrence at a median interval of 41.5 months. Kaplan–Meier curves showed that the hearing progression-free survival rates at 1-, 3-, and 5-years following GKS were 80, 66.7, and 53.3%, respectively. The MS group had a higher hearing preservation rate at 5 years (71.4 versus 53.3%), but the difference did not reach statistical significance (p = 0.173). Hearing preservation was statistically significant when the preoperative hearing status was class A in the GKS group (p = 0.016), but it was not statistically significant in the MS group (p = 0.777). In the MS group, medial type VS had a higher hearing preservation rate (80%) than the lateral fundal extended type VS (63.6%), and this difference was almost close to statistical significance (p = 0.058). The GKS group had a higher occurrence of postoperative tinnitus (23.3%) than the MS group (9.5%).

Conclusion:
MS was more suitable for patients who are younger, have good physical status, good preoperative hearing status including AAO-HNS class B, and medial type VS. GKS was more suitable for patients who are elderly, have poor physical status, preoperative AAO-HNS class A hearing.