Results for a Series of 697 Arteriovenous Malformations Treated by Gamma Knife: Influence of Angiographic Features on the Obliteration Rate

BACKGROUND: Stereotactic radiosurgery (RS) is an effective tool in treating brain arteriovenous malformations (AVMs). Careful study of AVM angiographic characteristics may improve results. OBJECTIVE: To report the long-term outcomes of Gamma Knife RS (GKRS) in brain AVMs, focusing on how the angioarchitectural and hemodynamic parameters of AVMs affect the post-RS results. METHODS: This was a retrospective, longitudinal study of 697 consecutive GKRS treatments of brain AVMs in 662 patients performed at a single center between 1993 and 2005. The mean age of the patients was 37 years; the median AVM volume was 3.6 cm(3); and the mean follow-up was 11 years. Forty-five percent of patients presented with intracranial hemorrhage; 44% underwent embolization; and 7% had multiple RSs. AVM characteristics in the RS-planning angiograms were analyzed, and their relationship to the post-RS obliteration rate was determined by univariate and multivariate analyses. RESULTS: The obliteration rate after a single RS was 69.3%; after multiple RS, it was 75%. Positive predictors of obliteration included compact nidus (odds ratio = 3.16; 95% confidence interval, 1.92-5.22), undilated feeders (odds ratio = 0.36; 95% confidence interval, 0.23-0.57), smaller AVM volume (odds ratio = 0.95; 95% confidence interval, 0.92-0.99), and higher marginal dose (odds ratio = 1.16; 95% confidence interval, 1.061.27). Improvement or clinical stability was observed in 89.3% of patients; postprocedural bleeding was noted in 6.1%; and clinical worsening attributable to RS was seen in 3.8%. The annual risk of hemorrhage in the 4 years after RS was 1.2%. CONCLUSION: GKRS yielded a good long-term clinical outcome in most patients. Certain angiographic features of brain AVMs such as a well-defined nidus and undilated feeder arteries contribute to AVM occlusion by RS. GKRS can be regarded as the treatment of choice for AVMs <6 cm(3), even after bleeding.