123 The Incidence of Infratentorial Arterial Venous Malformation-Associated Aneurysms: An Institutional Case Series and Systematic Literature Review

INTRODUCTION: Arteriovenous malformation (AVM)-associated aneurysms represent a high-risk feature predisposing them to rupture. Cerebrovascular embryology suggests differing origins between supratentorial and infratentorial vascular territories, and it is therefore plausible given their disparate derivations, differences exist in the prevalence of AVM-associated aneurysms. While infratentorial AVMs have been previously associated with related aneurysms, the existing data is outdated and biased. METHODS: Patients were identified from our institutional AVM registry, which includes all patients with an intracranial AVM diagnosis since 2000, regardless of treatment. Records were reviewed for clinical details, AVM characteristics, nidus location (supratentorial or infratentorial), and presence of associated aneurysms, which included flow-related and intranidal aneurysms. Statistical comparisons were made using Fisher’s exact or Wilcoxon rank sum tests where appropriate. Multivariable logistic regression analysis determined independent predictors of AVM-associated aneurysms. As a secondary analysis, a systematic literature review following Preferred Reporting Items for Systematic Reviews and Meta-analyses criteria was performed, where studies documenting the incidence of AVM-associated aneurysms stratified by anatomic location were of interest. RESULTS: From 2000-2024, 706 patients with 720 AVMs were identified, of which 152 (21.1%) were infratentorial. Intracranial hemorrhage was the most common AVM presentation (42.1%). The incidence of associated aneurysms was greater in infratentorial AVMs compared to supratentorial cases (45.4% vs. 20.1%; p< .0001). Multivariable logistic regression demonstrated that infratentorial nidus location was the singular predictor of an associated aneurysm, OR 2.9 (CI: 1.94–4.28). Systematic literature review identified eight studies satisfying inclusion criteria. Aggregate analysis indicated that infratentorial AVMs were more likely to harbor and associated aneurysm (OR 1.7) and present as ruptured (OR 3.9), p<.0001. CONCLUSIONS: In our modern patient series and review, infratentorial nidus position was a significant predictor of an associated aneurysm and hemorrhagic presentation.