Gamma knife radiosurgery of skull base meningiomas

Background The standart surgical treatment of meningiomas is total resectio n of the tumour. The complete removal of skull base meningiomas can be diff icult because of the proximity of cranial nerves. Stereotactic radiosurgery (SRS) is an effective therapy, either for adjuvant treatment in case of su btotal or partial tumour resection, or as solitary treatment in asymptomati c meningiomas. Method. Between September 1992 and October 1995, SRS using the Leksell Gamm a Knife was performed on 46 patients (f:m = 35: 15), ranging in age from 35 to 81 years, with skull base meningiomas at the Neurosurgical Department o f the University of Vienna. According to the indication of gamma knife radi osurgery (GKRS) the patients (n = 46) were devided into two subgroups. Grou p I (combined procedure: subtotal resection followed by GKRS as a planned p rocedure or because of a recurrent meningioma), group II (GKRS as the prima ry treatment). Histological examination of tumour tissue was available for 31 patients (67%) after surgery covering 25 benign (81%) and 6 malignant (1 9%) meningioma subtypes. Findings. The overall tumour control rate after a mean follow-up period of 48 months (ranging from 36 to 76 months) was 96% (97.5% in benign and 53% i n malignant meningiomas). Group I displayed a 96.7% tumour control rate, fo llowed by group TI with 93.3% respectively. Neurological follow-up showed a n improvement in 33%, stable clinical course in 58% and a persistant deteri oration of clinical symtoms in 9%. Remarkable neurological improvement afte r GKRS was observed in group II (47%), whereas in group I (26%) the amelior ation of symptoms was less pronounced. Interpretation. GKRS in meningiomas is a safe and effective treatment. A go od tumour control and low morbidity rate was achieved in both groups (I, II ) of our series, either as a primary or adjunctive therapeutic approach. Th e planned combination of microsurgery and GKRS extends the therapeutic spec trum in the treatment of meningiomas. Reduction of tumour volume, increasin g the distance to the optical pathways and the knowledge of the actual grow ing tendency by histological evaluation of the tumour minimises the risk of morbidity and local regrowth. Small and sharply demarcated tumours are in general ideal candidates for single high dose-GKRS, even after failed surge ry and radiation therapy, and in special cases also in larger tumour sizes with an adapted/reduced margine dose.