The posterior cerebral circulation, consisting of two vertebral arteries and one basilar artery, is known as the vertebrobasilar system, contributing about 20% of the brain’s blood supply.
These arteries arise from the subclavian arteries, near the shoulders, ascend through the neck and into the skull, giving off a number of smaller arteries including the posterior inferior cerebellar artery (PICA), uniting as the singular basilar artery, which ultimately bifurcates into two posterior cerebral arteries. The vertebrobasilar system perfuses the occipital cerebral cortex, cerebellum, thalamus, midbrain, pons, and medulla. Strokes that result from occlusion of these vessels are less common than anterior or middle circulation strokes. Basilar artery occlusion is fatal in 75% and survivors usually have severe disability. Blockage of vertebral arteries or their smaller branches results in a variety of findings depending on the specific location and vessel...