Long-term results of Gamma Knife surgery for arteriovenous malformations: 10- to 15-year follow up in patients treated with lower doses.

OBJECT: Several adverse effects such as brain edema, necrosis, arterial stenosis, hemorrhage after obliteration, and delayed cyst formation have been reported as early and late complications of Gamma Knife surgery (GKS) for arteriovenous malformations (AVMs). These adverse effects seem to be decreased in a lower-dose treatment regimen compared with the classic higher margin doses of 25 Gy because the radiation insult to the surrounding tissue is minimized. Long-term results of lower-dose GKS for AVMs are presented.
METHODS: One hundred fourteen patients with AVMs were treated with lower-dose GKS (< or = 20-Gy margin dose). There were 68 male and 46 female patients, aged 10 to 68 years (mean 35.4 years). The evaluation of AVM nidi and dose planning were performed using both angiography and MR imaging in all cases to exclude the surrounding brain tissue. The mean margin dose was 19.5 Gy. Total angiographically documented obliteration was achieved in 65 (85.5%) of 76 patients. Eleven patients underwent a second treatment, including staged treatment for large AVMs; total AVM obliteration has been achieved in six of them to date. Of 38 patients in whom no follow-up examination could be performed, 19 of them were healthy and 10 were lost from follow up. Nine patients experienced bleeding during the latency period, and four of them suffered lethal hemorrhage. Symptomatic early complications were extensive brain edema after repeated GKS in one patient and an adverse effect on the internal capsule in one. Delayed cyst formation was found in one patient as a late complication 10 years after treatment. No treatment-related death has been noted to date.
CONCLUSIONS: Lower-dose GKS is an effective and safe treatment for patients with AVMs and may decrease long-term adverse effects to the surrounding brain.