Hearing Outcome after Gamma Knife Stereotactic Radiosurgery in Vestibular Schwannoma Patients with Serviceable Hearing.

Cho, Jae Hoon; Paek, Sun Ha; Chung, Hyun Tai; Jeong, Sang Soon; Jung, Hee Won; Kim, Dong Gyu

Original Article

Journal of Korean Neurosurgical Society 2006;40(5): 336-341.

Jae Hoon Cho, Sun Ha Paek, Hyun Tai Chung, Sang Soon Jeong, Hee Won Jung, Dong Gyu Kim

Department of Neurosurgery, Seoul National University College of Medicine, Clinical Research Institute of Seoul National University Hospital, Seoul, Korea. gknife@plaza.snu.ac.kr

ABSTRACT

OBJECTIVE
The authors conducted a retrospective study to evaluate the preservation rates of serviceable hearing and to determine its prognostic factors after gamma knife stereotactic radiosurgery(GK SRS) in the patient with vestibular schwannomas.
METHODS
Between December 1997 and March 2005, 54 patients with a sporadic vestibular schwannoma and serviceable hearing (Gardner Robertson grade I-II) were enrolled in this study. Electronic database of medical records and radiological examinations before and after GK SRS were investigated to the last follow up. The mean marginal dose was 12.3+/-0.7Gy. The mean maximum dose delivered to the tumor center was 24.7Gy (22~30Gy). The median tumor volume was 2cc (0.1~9.1cc). The median follow-up period of magnetic resonance(MR) imaging was 31 months (6~99 months), and the mean follow-up period of audiometry was 24 months (4~70 months).
RESULTS
The tumor control rate was 100% in the patients with the follow up period more than 2 years. The trigeminal and facial nerve preservation rates were 98% and 100%, respectively. Twenty-eight (52%) of the 54 patients preserved serviceable hearing and 16 (30%) patients retained their pre-GK G-R grade level after GK SRS. In the univariate and multivariate analysis, there was no significant prognostic factor in preservation of the serviceable hearing.
CONCLUSION
The hearing preservation rate is still unsatisfactory compared with the results of other cranial nerve preservation and tumor control in the treatment of vestibular schwannoma by GK SRS. More sophisticated strategy during and after GK SRS is necessary to improve long-term hearing preservation.

Key Words: Vestibular schwannoma; Gamma knife stereotactic radiosurgery; Hearing preservation