Branch formation, distal

Additional common sites for atherosclerotic occlusion include the origin of the vertebral artery, the distal vertebral and vertebrobasilar junction, the midbasilar artery, and the proximal PCA. Unlike ICA disease, severe atherosclerotic stenosis in the distal intracranial vertebral and basilar arteries can cause stroke via thrombotic occlusion of local branches as well as artery-to-artery embolus to the top of the basilar artery or the PCA(s). Low flow in the basilar artery can lead to thrombus formation with occlusion of one brainstem penetrator vessel after another. Basilar thrombosis is not rare and is fatal because brainstem function is completely dependent on this vascular supply [20, 23]. 

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