We analyzed 68 cases with cerebral AVM 3 years after treatment. Total obliteration rates at 1, 2, and 3 years after treatment were 42.5%, 76.1%, and 82.0%, respectively. Four factors: moya type, small volume, deep location and high marginal dose were found to be correlated with total obliteration. So we scored these factors, and categorized them into a grade 0 to 6 Gamma Knife Score (GKS). The total obliteration rate was high in the low GKS group. Hemorrhage occurred in 6 cases with a yearly risk of 2.9%. These cases were relatively large and had high GKS and high Spetzler-Martin grade. Radiation injury occurred in 2 cases. Both cases had edema spreading to white matter and suffered from hemiparesis. Based on these results and our current grading system, our treatment strategy at present is as follows. AVMs with a low GKS had a high obliteration rate and seemed suitable for radiosurgery. Because total obliteration is difficult to achieve in the high grade group, aggressive surgery or endovascular surgery should be considered.
