Gamma knife radiosurgery for acoustic neuromas performed by a neurotologist: Early experiences and outcomes

Objective: To assess early outcomes after Gamma knife radiosurgery of acoustic neuromas and other skull base tumors. Background: Gamma knife radiosurgery is one of the available methods to treat acoustic neuromas, in addition to microsurgical resection. Neuro-otologists have long been associated with microsurgical resection of these tumors; however, the application of Gamma knife radiosurgery to the treatment of these tumors by neuro-otologists has not been previously described. Setting: Acoustic Neuroma and Skull Base Surgery Program / Tertiary Referral Center. Study Design/Patients/Intervention: Prospective clinical study of all patients treated by the senior author and our gamma knife team beginning in June 2000. Main Outcome Measures: Preoperative MRI, audiometry, vestibular testing and facial nerve electromyography were completed. At six-month intervals postoperatively, audiometry, caloric testing and MRI were performed to determine thresholds and speech discrimination ability, vestibular function, and the size of the tumor. Results: From June 2000 until March 2004, 38 patients were treated, and these included 33 acoustic neuromas, two meningiomas, one glomus jugulare tumor, and two facial neuromas. Greater than 36 month follow-up was available in 7 patients, > 24 months in 24, > 12 months in 31, and > 6 months in 34 patients. Statistically significant reduction in tumor size was seen over time, and tumor control was achieved in all but two patients. Various patterns of changes in auditory function, both in threshold and speech discrimination were observed in either positive or negative directions. Conclusions: Preliminary experience with Gamma knife radiosurgery indicates that this treatment method represents another option for neuro-otologists to use in managing patients with skull base tumors.