Anatomical Variations of Vertebrobasilar Artery are Closely Related to the Occurrence of Vertebral Artery Dissection-An MR Angiography Study

Goal: Intracranial arterial dissection is a major cause of ischemic stroke and subarachnoid hemorrhage in relatively young patients. We assessed the hypothesis that the tortuosity of the vertebrobasilar artery is associated with the occurrence of vertebral artery (VA) dissection, using MR angiography (MRA). Materials and Methods: This study enrolled 43 patients with VA dissection, and 63 age- and sex-matched healthy subjects were used as the controls. MRA was employed to evaluate the presence of dominant VA and the lateral shift of vertebrobasilar junction in both groups. The VA diameters were considered different when the difference was greater than .3 mm. These anatomical variations were divided into 3 types: Type 1 (vertebrobasilar junction within 2 mm from the midline), Type 2 (>2 mm-lateral shift of vertebrobasilar junction to the ipsilateral side of the dominant VA), and Type 3 (>2 mm-lateral shift of vertebrobasilar junction to the contralateral side of the dominant VA). Findings: The presence of dominant VA and the lateral shift of vertebrobasilar junction were more prevalent in patients with VA dissection than in the controls (OR: 3.46, P = .013, and OR: 4.51, P = .001, respectively). The lateral shift of vertebrobasilar junction was classified into Type 1 (n = 6), Type 2 (n = 13), and Type 3 (n = 17) among patients with VA dissection, while into Type 1 (n = 20), Type 2 (n = 8), and Type 3 (n = 7) among the controls. Type 3 predominance was observed in patients with VA dissection (P = .02). Conclusions: Anatomical variations of the vertebrobasilar artery may play an important role in the occurrence of VA dissection.