Examining AVM Rupture Risk After SRS Related to Venous Outflow Stenosis

Introduction/Purpose Arteriovenous malformations (AVMs) treated with stereotactic radiosurgery (SRS) undergo vascular remodeling during the latency period before obliteration. While radiation‐induced complications are well documented, detailed angiographic characterization of venous remodeling remains uncommon. This case uniquely illustrates the dynamic nature of AVM hemodynamic remodeling within the venous system post‐SRS and provides valuable insights into the pathophysiology of changes during the latency period. More importantly, it underscores the necessity for recharacterization of routine angiographic assessment of venous drainage patterns in post‐SRS patients to allow for appropriate interval monitoring. Materials/Methods A 50‐year‐old man with a right superior frontal AVM previously treated with single‐fraction SRS in 2024 presented in 2025 with acute left hemiparesis and severe headache. Computed tomography (CT), CT angiography (CTA), and emergent digital subtraction angiography (DSA) were obtained to evaluate the hemorrhage and define the post‐treatment vascular architecture. Results Initial CT/CTA revealed a small subarachnoid hemorrhage and a 1.7 cm residual nidus. DSA demonstrated marked post‐SRS angioarchitectural changes. Arterial supply from middle cerebral artery (MCA) branches had regressed, leaving residual feeders from the anterior cerebral artery (ACA). Superselective ACA angiography confirmed persistent high‐flow feeders but also revealed en passage vessels, rendering embolization unsafe. Venous drainage demonstrated dramatic remodeling, consolidating into a single cortical outflow channel with severe stenosis. Compensatory contralateral drainage was recruited through the vein of Trolard and vein of Labbe. No nidal or flow‐related aneurysms were identified. In light of unfavorable venous anatomy and risk of morbidity, embolization was deferred. The patient was managed conservatively with strict blood pressure control and close multidisciplinary follow‐up. Conclusion This case highlights a unique and striking example of radiation‐induced venous hemodynamic remodeling, characterized by severe outflow stenosis and recruitment of a contralateral venous drainage pathway. These changes created hemodynamic instability that culminated in AVM rupture during the SRS latency period. Although radiation‐induced complications are well recognized, detailed angiographic visualization of such venous remodeling is rarely documented. The contrast between initially “stable” AVM features and subsequent venous instability underscores the limitation of relying solely on nidus size or arterial supply for follow‐up. Instead, these findings argue for a re‐evaluation of standard surveillance protocols, with greater emphasis on venous outflow assessment. Advanced imaging techniques that capture flow dynamics, such as 4D flow MRI, may provide valuable insights during the latency phase and allow earlier recognition of evolving risk.