BACKGROUND: Stereotactic radiosurgery (SRS) is widely accepted as aminimally invasive alternative to surgery in themanagement of arteriovenous malformations (AVMs). Dilated AVM outflow veins or varices may be caused by high-flow or partial outflow obstruction, which may increase the risk of a hemorrhage before or after SRS.OBJECTIVE: To compare the obliteration and hemorrhage risks in patients with and without AVM varices (AVMv).METHODS: From our prospective database of 1012 AVM patients who underwent Gamma Knife (R) (Elekta) SRS, we identified 103 patients with AVMv, and 847 patients without varices. The median follow-up was 52 mo. Balancing variable score matching was performed to compare obliteration and hemorrhage rates between the 2 groups.RESULTS: Obliteration rates in the AVMv group were 38% at 3 yr, 65% at 4 yr, and 70% at 5 yr. Patients with an AVMv had no difference in the final obliteration rate compared to patients who did not have variceal drainage (P=.35). Actuarial hemorrhage after SRS in the matched patients with AVMv was 4.9%, 13%, and 13.7%, at 1, 3, and 5 yr, respectively. The rate of hemorrhage in the group with no varix was 2.9%, 5.4%, and 9.1% at 1, 3, and 5 yr, respectively (P = .14).CONCLUSION: The presence of AVM variceal venous drainage did not affect the obliteration rate and did not confer a higher risk of a subsequent hemorrhage both before and after SRS.