Gamma Knife surgery for large cerebral arteriovenous malformations.

Object: Treatment of arteriovenous malformations (AVMs) is problematic due to many factors, including lesion size, lesion location, unacceptable complications, and negative outcomes. To overcome the limitation imposed by a large nidus volume, neurosurgeons have used Gamma Knife surgery (GKS) in a variety of ways, including combined with other treatment modalities, as volume-staged radiosurgery, and as repeat radiosurgery. We performed repeat radiosurgeries in patients who harbored large AVMs (> 30 cm(3)) and analyzed the AVM obliteration rates and complications.

Methods: The authors reviewed the cases of 44 patients at a single institution who underwent GKS between 1992 and 2007 for treatment of an AVM whose nidus was 30 cm(3) or larger. The mean age of the patients was 27 years (range 4.5-62.3 years), and the median duration of follow-up was 109.4 months (range 27-202 months). The mean AVM nidus volume was 48.8 cm(3) (range 30.3-109.5 cm(3)), and the mean radiation dose delivered to the margin of the nidus was 13.9 Gy (range 8.4-17.5 Gy). The authors determined complete AVM nidus obliteration based on findings on both MR images and digital subtraction angiograms. When they did not detect complete obliteration after GKS, they performed 1 or more additional GKSs separated by a minimum interval of 3 years.

Results: The overall obliteration rate following repeat GKS was 34.1%, and the estimated obliteration rate at 120 months was 41.8%. Three patients (6.8%) experienced hemorrhages after GKS, and 2 patients (4.5%) developed cysts. One patient (2.3%) experienced a newly developed seizure following GKS, and another patient (2.3%) was found to have radiation necrosis.

Conclusions: Even though complete obliteration of the large AVMs after repeat GKS took a long time, the complication rate was quite acceptable. In addition, the estimated obliteration rate at long-term follow-up was respectable. Repeat GKS should be considered as a primary treatment option for symptomatic large AVMs to overcome the limitation imposed on successful obliteration by the large volume of the nidus.