Gamma Knife Radiation Therapy for Intralabyrinthine Schwannomas

Background: Intralabyrinthine schwannoma are rare benign tumors exclusively managed to date with observation or surgical removal. We analyze results of radiosurgical treatment of these lesions. Methods: Retrospective analysis of medical data of 454 patients with vestibular schwannomas treated by Gamma Knife in our center was performed. We identify 12 patients treated for a schwannoma located partially or totally into the cochleo-vestibular structures. Ten patients with a clinical and radiological follow-up of more than 1 year were selected for further analysis. Results: Patients had hearing worsening at different stages, sometimes associated with tinnitus, imbalance or vertigo. The median duration of symptoms before treatment was 3.3 years. Anatomical location of the ILS was intravestibular, intracochlear, intravestibulocochlear, transmacular or transmodiolar (2 patients for each location). We cover 100% of the tumor volume in all patients with a mean margin dose of 11.7 Gy (range 11-12 Gy). The mean follow-up duration was 2.8 years (range 1.5-6.5 years). For 5 patients with functional hearing before treatment, 2 patients had unchanged audiological status at last follow-up, 1 patient had moderate hearing worsening, and 2 patients became cophotic (functional hearing preservation rate of 40%). Facial palsy, even partial and transient, did not occur. No patient experienced permanent worsening of tinnitus, imbalance or vertigo after irradiation. Conclusions: Gamma Knife radiation therapy seems to be a safe and effective treatment alternative to surgery for patients with intralabyrinthine schwannomas. Radiosurgery can be performed in this indication without significant morbidity with the precision of current robotized Gamma Knife.