Abstract DP061: Hidden in Plain Sight: Dynamic DSA Reveals a Spectrum of Vertebral Artery Compression in Posterior Circulation Stroke – A Community Hospital Case Series

Background: Posterior circulation strokes without findings on conventional non-dynamic vascular imaging (CTA or MRA) are often presumed cardioembolic or hypercoagulable. This may lead to under-recognition of dynamic vascular pathologies such as Bow Hunter’s Syndrome (BHS)—a spectrum of vertebrobasilar insufficiency from subtle compression to occlusion—that can precipitate recurrent strokes. Our prior investigation suggested that vertebral artery pseudoaneurysm may serve as an indicator of BHS and a prompt for dynamic vascular imaging. Over the course of one year, we encountered three such cases at a community hospital, highlighting the diagnostic utility of dynamic digital subtraction angiography (DSA). Methods: We retrospectively reviewed patients with posterior circulation infarcts and inconclusive workups, including negative CTA, hypercoagulable testing, and cardioembolic evaluation, with no findings to explain the stroke pattern. Results: Case 1: A 41-year-old man with bilateral cerebellar and thalamic infarcts. Dynamic DSA revealed a left V3 pseudoaneurysm with partial compression during head rotation, without occlusion (Figure 1) Case 2: A 45-year-old man with recurrent bilateral cerebellar infarcts and severe dizziness. Imaging showed a hypoplastic, occluded left vertebral artery; dynamic DSA demonstrated kinking of the dominant right vertebral artery with rightward head turn, reproducing his dizziness. (Figure 2) Case 3: A 61-year-old woman with a history of recurrent posterior circulation strokes over three months, despite maximal medical therapy with dual antiplatelet therapy, statin, and closure of a large PFO. Dynamic DSA identified a right V2 pseudoaneurysm abutting a cervical osteophyte, with progressive narrowing culminating in complete occlusion at 60° contralateral head rotation and collateral reconstitution. (Figure 3) Conclusions: The identification of three cases within a single year at a 455-bed community hospital highlights that BHS may be more common than currently appreciated and often remains underdiagnosed. These cases demonstrate a continuum of vascular compromise, from partial compression to complete dynamic occlusion with pseudoaneurysm formation, causing recurrent posterior circulation strokes even when conventional workups are negative. Our findings suggest that vertebral artery pseudoaneurysm on conventional imaging may serve as a valuable marker of underlying BHS, warranting dynamic vascular evaluation.