Staged radiosurgical treatment for large benign cerebral lesions

Object. Large brain lesions are considered unamenable to gamma knife treatm ent because of possible adverse effects. The proximity of eloquent brain to a target location, including some arteriovenous malformations (AVMs), stil l poses a challenge to the neurosurgeon. Because meningiomas and AVMs often show a slower absent growth rate, partial radiosurgical treatment in cases with risk of unacceptable surgery-related morbidity is an alternative. The authors evaluated the results of staged treatment. Methods. Since April 1992, 12 patients suffering from large benign tumors ( meningiomas) and seven with AVMs considered inoperable underwent gamma knif e radiosurgery in staged procedures. All patients with tumors underwent pri mary open surgery for partial removal of recurrent growth and subsequent ra diosurgical treatment. Four men and eight women ranging in age from 26 to 7 3 years harbored tumors that ranged in volume from 19 to 90 cm(3). Marginal dose ranged from 10 to 25 Gy prescribed in the 30 to 50% isodose. The time interval between the radiosurgical treatments varied from 1 to 8 months. F ollow up ranged from 5 and 89 months. Three female and four male patients ( age range 10-48 years) had undergone previous AVM embolization and were tre ated with margin doses of 18 to 22 Gy in the 40 to 50% isodose. The volume range of these AVMs was 11 to 25 cm(3). The time interval between radiosurg ical treatments ranged from 5 to 36 months. The mean follow up was 22.6 mon ths. Neurological follow-up examinations showed clinical improvement in 11 patie nts (58%), whereas five (26%) remained unchanged. Among tumor patients no d eterioration or further tumor growth was observed. Tumor necrosis demonstra ted noticed in five patients (26%). One patient with an AVM suffered from s eizures and hemiparesis. Follow-up magnetic resonance imaging of the residu al nidus disclosed no rebleeding. Conclusions. For selected patients with large benign lesions staged gamma k nife radiosurgery could be an alternative, as evidenced by the authors' ser ies in which there was no mortality and low incidence morbidity.