Objectives:

Arteriovenous malformations (AVMs) are lesions characterized by an intervening vascular nidus. Management of giant AVMs is complex and relies on multimodal treatment. Stereotactic radiosurgery (SRS) has been commonly used, while predictive factors associated with the SRS outcomes have not been well explored. This study aims to evaluate the outcomes of SRS for Spetzler-Martin (SM) Grade IV–V Giant AVMs, and determine predictive factors associated with hemorrhage, and degree of nidus eradication

Methods:

We performed a retrospective cohort study of all patients with Spetzler-Martin Grade 4-5 AVM and volume > 10 cm3. Demographic, radiologic, treatment and outcome data were collected. The primary outcomes were AVM obliteration and post-treatment hemorrhage. Data were compared by Fisher’s exact test for categorical variables and by Mann-Whitney U test for continuous variables. Pearson correlations analyzed variable relationships.

Results:

We identified 28 Giant AVMs from 28 patient with SM Grade IV (28.6%) or V AVMs (71.43%). A total of 39 SRS treatments were applied, including 13 staged volume (33.3%), and 26 non-staged volume (66.7%) SRS. The median age was 17 years at first treatment and 60.71% were male. Pre-SRS embolization was performed in 50%. The median AVM volume was 15.6 cm3. Complete obliteration was achieved in 35.7% with a mean follow-up of 76.9 months. High risk features for hemorrhage were detected in 21.4%, including intra-nidal aneurysms and venous stenosis. We found association between presence of extra-nidal aneurysms and AVM obliteration (p=0.009). In addition, we found a negative correlation between post-SRS hemorrhage % reduction in AVM volume (p=0.009). There was no association of other known factors such as marginal dose, AVM pre-treatment volume or embolization with outcomes.

Conclusion(s):

In this cohort of giant AVMs treated with mixed SRS methods, we found extranidal aneurysms to be a predictive feature for AVM obliteration, and post-SRS hemorrhage to be associated with less volume reduction.