Introduction: The outcomes stereotactic radiosurgery (SRS) for intracranial arteriovenous malformations (AVM) with patent intranidal and prenidal AVM-associated arterial aneurysms (AAA) are poorly understood, since many AAAs are embolized prior to nidal intervention. The aim of this retrospective cohort study is to analyze the SRS outcomes for AVMs with AAAs.

Methods: We evaluated an institutional database of AVMs treated with Gamma Knife SRS from 1989 to 2013. AVMs with patent AAAs at the time of SRS were selected for analysis. AAAs were classified as intranidal (type I) or prenidal (type II).

Results: The study cohort comprised 51 AVMs, including 23 with type I (45%) and 28 with type II (55%) AAAs. The actuarial obliteration rates of AVMs with type I AAAs at 3, 5, and 10 years were 32%, 45%, and 76%, respectively. The actuarial obliteration rates of AVMs with type II AAAs at 3, 5, and 10 years were 25%, 58%, and 66%, respectively. The actuarial obliteration rates were not significantly different between AVMs with type I vs. type II AAAs (P=0.442). All AVMs with type I AAAs which obliterated after SRS also had complete AAA occlusion. Of the 28 AVMs with type II AAAs, angiographic follow-up was available in 18 (64%). The actuarial rates of type II AAA occlusion after SRS at 3, 5, and 10 years were 46%, 77%, and 95%, respectively. The type II AAA occlusion rate was significantly higher in obliterated AVMs (P=0.002).

Conclusions: Since AVMs with AAAs remain at risk for hemorrhage until both the AVM nidus and AAA are completely obliterated, long-term angiographic follow-up is crucial after SRS. The majority of type II AAAs will occlude following nidal intervention with SRS, occurring with a greater probability in the setting of AVM obliteration.

Patient Care: Since AVMs with AAAs have been found to have an elevated risk of hemorrhage, targeted embolization of AAAs is commonly employed prior to treatment of the AVM nidus with SRS. Thus, the SRS outcomes of AVMs with patent AAAs are poorly documented in the literature. Our retrospective analysis provides detailed data regarding the outcomes after SRS for AVMs with patent intranidal and prenidal AAAs, with regard to both nidal obliteration and AAA occlusion. These findings show that appropriately selected AVMs with AAAs can be successfully treated with SRS alone, thereby obviating the potential morbidity associated with neoadjuvant embolization.

Learning Objectives: By the conclusion of this session, participants should be able to 1) Describe the importance of SRS in the management of AVMs with intranidal and prenidal AAAs, 2) Discuss, in small groups the outcomes after SRS for AVMs with AAAs, with respect to nidal obliteration and AAA occlusion, and 3) Identify an effective treatment for AVMs with intranidal and prenidal AAAs.

References: 1. Ding D, Xu Z, Starke RM, et al. Radiosurgery for Cerebral Arteriovenous Malformations with Associated Arterial Aneurysms. World Neurosurg. Mar 2016;87:77-90.