Long-term results of Gamma-knife stereotactic radiosurgery for vestibular schwannomas in patients with type 2 neurofibromatosis.

INTRODUCTION: The aim of this study was to analyze the long-term results of Gamma-knife radiosurgery treatment of vestibular schwannomas in type 2 neurofibromatosis patients.

MATERIALS AND METHODS: A cohort of 129 treatments for vestibular schwannomas in 103 patients was selected from a prospectively-maintained clinical database. Tumor control was assessed by volumetric analysis of the tumor at the last follow-up. Any need of a further procedure such as microsurgical removal or second treatment was regarded as a failure of tumor control. Hearing function was assessed based on Gardner-Robertson classification. Progression-free survival and functional hearing preservation rates were estimated using the Kaplan-Meier method.

RESULTS: The median age at treatment was 34 years with no gender predominance. The median tumor volume was 1.5cm3 . At a median clinical follow-up of 5.9 years, five patients had died, four underwent a second radiosurgical procedure and eight underwent microsurgical resection. Progression-free survival was 88 and 75% respectively at 5 and 10 years. Hearing was considered serviceable in 70 ears and remained functional in 28 ears. Kaplan-Meier estimates for 5 and 10 years functional hearing was 47 and 34%, respectively. Three patients developed new facial nerve palsy after radiosurgery at 15 days, 6 and 19 months respectively and only one partially recovered. Five patients complained of a subjective instability worsening. Four cases developed trigeminal neuropathy. No predictive factors were found to be statistically correlated with a better hearing outcome or an improved tumor growth control.

CONCLUSION: Results prove less satisfying than in sporadic unilateral schwannomas. However, the lower rate of mortality and morbidity compared with microsurgical resection may support a proactive role of Gamma-knife in this pathology.