The treatment of arteriovenous malformations (AVMs) is complicated because of many factors including their size, location, and unacceptable deficits. When we consider gamma knife surgery (GKS), it is well known that the volume of cerebral AVM compromises the obliteration. 

     We reviewed the Large AVM cases (>20cc) in our gamma knife center.

     Between 1992 and 2007, 119 cases of large AVM have undergone GKS in our institute. We enrolled the patients followed up over 24 months, and reviewed medical records and radiological images retrospectively. We excluded the patients with incomplete chart information, and those who were lost to follow up.  Finally 81 patients were included in this study. 

     The magnetic resonance image (MRI) and digital subtraction angiography (DSA) were followed up at 2-3 years intervals and repeat GKS was considered at 3 years after previous GKS. The median age of population at the time of GKS was 30.45 years old. The median follow up duration was 123. 37 months. The mean volume of AVM nidi was 36.76 cc and mean margin dose to delivered to AVM nidi was 14.52 Gy.

     Overall obliteration rate was 43.2% and obliteration rate at 3 years was 20.0%. Fifty percents of the patients have undergone GKS once, and others twice or more times. The obliteration rate at 6 years was 62.9%. Previous procedures such as embolization, surgery, and radiation didn’t influence the obliteration rate. Annual hemorrhage rate were 0.68% a year. The complications were hemorrhage, cyst formation, seizure and radiation necrosis.

     This is a retrospective study.

     Even though the time to total obliteration is a little longer, the complication rate such as rebleeding was acceptable.  And the obliteration rate at long term follow up was not low. 

     We thought that GKS would be considered as an alternative treatment options for large AVMs.