We investigated a treatment strategy for arteriovenous malformations (AVMs) of the brain based on results of 107 patients treated with Gamma Knife (GK) surgery between 1991 and 1995. Total obliteration was obtained in 80.5%. The obliteration rate was 82.1% in Grade 3 of Spetzler-Martin scale, 75.0% in Grade 4, 50.0% in Grade 5, and 66.7% in Grade 6. The obliteration rate of slow and low flow AVMs (moya type) within 12 months (65.5%) was significantly higher than that of rapid and/or high flow AVMs (shunt, mixed type). Six patients had bleeding 7 to 42 months after GK surgery. The annual rate of bleeding in accumulated years was 2.3%. Adverse effects appeared in 2 (1.9%) of 107 patients, and both patients had AVMs in the internal capsule. We concluded that microsurgery is recommended for AVMs operable without morbidity, and GK surgery is recommended for AVMs in functional areas, and that intravascular embolization is required for large, rapid and/or high flow AVMs, especially those with hemorrhagic risk factors.
