Anatomy knowledge matters. Here is an acute completed PCA infarct
Angio — look at transition in vertebral artery caliber. Why?
Selective vert injection
What is this? Answer is knowledge of anatomy. There is a variant of proximal “duplicated” vert — where direct aortic origin vert and “classic” subclavian origin vert origins co-exist, usually fusing somewhere in the lower cervical segment into a single vessel. Below is a different case of this anatomical disposition. See Vertebral Artery page for much more on this, including key to the arrows
This is not just anatomical satisfaction — it establishes stroke etiology as artery-to-artery embolism due to dissection. Mystery solved
Cranial view of PCA occlusion
MIP coronal CTA — image on left shows nicely the dissected segment of the direct origin vert