Stereotactic radiosurgery of skull base meningiomas.

Between April 1992 and February 1996, 97 patients with skull base meningiomas were treated at our department. The age of these patients ranged from 10 to 80 years. The male/female ratio was 1/2. Fifty-three of these patients had primary open surgery for partial removal or recurrent growth and subsequent radiosurgical treatment. Radiosurgery was performed as a primary treatment in 44 patients. The mean tumor volume was 13.7 cm3 (range: 0.8-82 cm3). These tumor volumes could be covered by mean isodose volumes of 45% (range: 20-70%) and were treated by a mean dose of 13.8 Gy (range: 7-25 Gy) at the tumor border. Six patients underwent radiosurgery with a staged treatment protocol with 4.6-6 months interval. In 78 patients, a total of 102 follow-up scans were available. The remaining 19 patients have not been included in the post-radiosurgical evaluation since the observation time was either too short or the patients were lost for follow-up. The mean interval between gamma knife treatment and last follow-up scan was 18.5 months, with a range from 6 to 46 months. Follow-up imaging (CT, MRI or both) revealed a decreased volume of the tumor in 31 cases (40%). In 44 cases (56%), tumor progression was stopped, and in 3 cases (4%) increased tumor volumes could be observed. In 8 cases marked central tumor necrosis was seen. Neurological follow-up examinations in 76 patients showed a stable neurological status in 71%, ameliorated status in 24% and worsening in 5% of the patients.