Objective:

To describe a rare case of rapid, radiation-induced venous remodeling following stereotactic radiosurgery (SRS) for a cerebral arteriovenous malformation (AVM), resulting in rupture within the latency period. 

Background:

AVMs are congenital cerebrovascular anomalies associated with an annual hemorrhage risk of 2–4% if untreated. SRS is a well-established treatment for select AVMs, achieving nidus obliteration over 1–3 years through radiation-induced vascular changes. During this latency period, hemorrhage risk persists. While radiation-induced changes are recognized complications, their specific impact on venous hemodynamics - particularly in terms of drainage remodeling remains poorly characterized. 

Design/Methods:

n/a

Results:

A 50-year-old man with a right superior frontal AVM underwent single-fraction SRS. Several months later, he presented with acute left hemiparesis and severe headache. CT/CTA showed a small subarachnoid hemorrhage with residual nidus. Emergent diagnostic angiogram revealed profound post-SRS venous remodeling: arterial inflow from MCA feeders had regressed but residual supply from ACA branches persisted. Venous outflow was markedly altered, leading into a single cortical vein with severe stenosis and, notably, recruitment of a novel contralateral drainage pathway via the left vein of Trolard and vein of Labbe into the left sigmoid sinus. No nidal or flow-related aneurysms were identified. Due to unfavorable angioarchitecture with en passage feeders, embolization was deferred, and the patient was managed conservatively with interval monitoring.

Conclusions:

This case highlights a unique mechanism of post-SRS AVM rupture: rapid venous outflow stenosis coupled with recruitment of a contralateral drainage pathway, producing severe intranidal hemodynamic stress. While AVM “stability” is often assessed by nidus size or arterial supply, this case highlights the inadequacy of morphology alone in predicting risk. Recognition of radiation-induced venous remodeling argues for incorporating venous assessment and dynamic flow-sensitive imaging into post-SRS surveillance, as such changes may herald hemodynamic instability and predispose to rupture despite apparent arterial regression.