Osseous and Vascular Course Anomalies in Nontraumatic Vertebral Artery Dissection: A Per-Vessel Case-Control Study

BACKGROUND: Vertebral artery (VA) dissection (VAD) is a common cause of stroke in young and middle-aged adults. Although many cases are idiopathic, we hypothesized that overlooked osseous and vascular course anomalies (hereafter, structural anomalies) may be associated with VAD. In this study, we investigated the prevalence of these structural anomalies in patients with nontraumatic VAD using per-vessel analysis. METHODS: In this retrospective single-center case-control study, we analyzed structural anomalies in 13 consecutive patients (26 vessels) diagnosed with nontraumatic VAD at our institution between January 2022 and December 2025. For comparison, all eligible control patients during the same period whose computed tomography angiography field of view fully included the cervical region required to assess high-entry VA were included (50 patients, 100 vessels). The anatomic relationship between the VA and adjacent cervical osseous structures was evaluated using 3-dimensional computed tomography angiography. Primary end points were arcuate foramen presence, high-entry VA, and craniovertebral junction malformation with persistent first intersegmental artery. Images were independently evaluated by 2 neurosurgeons. RESULTS: Structural anomalies were identified in 76.9% (20/26) of the vessels in the VAD group, compared with 11.0% (11/100) in the control group ( P =1.21 × 10 −10 ; odds ratio, 25.75 [95% CI, 7.99–96.9]). At the patient level, structural anomalies were present on the ipsilateral side in 12 out of 13 patients (92.3%) and on the contralateral side in 8 out of 13 (61.5%); this paired difference did not reach statistical significance (exact McNemar test, P =0.219). The arcuate foramen (50.0%) and high-entry VA (19.2%) were the most common sites in the VAD group. Interrater reliability was excellent (raw agreement, 99.0%; κ=0.95 [95% CI, 0.86–1.00]). CONCLUSIONS: The findings support the possibility that some VADs traditionally considered idiopathic may be associated with mechanically mediated injury within a broader spectrum related to the concept of bony stroke.