Gamma Knife Radiosurgery as Primary Treatment for Large Vestibular Schwannomas: Clinical Results at Long-Term Follow-Up in a Series of 59 Patients

Background Gamma Knife radiosurgery (GKRS) represents a well-accepted treatment for small-medium vestibular schwannomas (VS); however, its application in larger VS is still controversial. Methods Among the 523 patients treated at our institution for VS between 2001 and 2010, we included 59 patients with a VS larger than 25 mm, treated by GKRS as primary treatment, not affected by neurofibromatosis type 2, and with a clinical follow-up of at least 36 months. Five patients underwent ventriculoperitoneal shunt placement before radiosurgery. Clinical follow-up (mean, 79.4 months) was obtained in all patients. Patients’ age ranged from 24 to 85 years (mean, 63.8 years). Mean tumor volume was 5.98 cm³ (maximum, 14.3 cm³) and median marginal dose was 13 Gy. A statistical analysis was performed to correlate clinical outcome with tumor radiologic features, dose-planning parameters, and patients’ characteristics. Results Tumor control was achieved in 98.3% of cases. At last follow-up, 86.4% of VS showed volume reduction. Recorded complications were 3 cases (5.1%) of new permanent facial nerve deficit, 4 cases (6.8%) of new or worsened trigeminal impairment, and 10 new cases (18.5%) of hydrocephalus requiring ventriculoperitoneal shunt. Larger tumor size was significantly associated with a subsequent ventricular enlargement. Overall, functional hearing preservation rate was 31.3% (66.7% among patients with Gardner-Robertson I). Conclusions Surgical resection remains the primary approach for large VS with symptomatic brainstem compression. GKRS can be considered a safe and effective option in particular in patients who are not good candidates for surgery.