What is the anatomy of vertebral and basilar arteries relative to vertebrobasilar stroke?

Updated: Aug 09, 2021
  • Author: Vladimir Kaye, MD; Chief Editor: Stephen Kishner, MD, MHA  more...
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The vertebral arteries arise from the subclavian arteries, and as they course cephalad in the neck, they pass through the costotransverse foramina of C6 to C2. They enter the skull through the foramen magnum and merge at the pontomedullary junction to form the basilar artery. Each vertebral artery usually gives off the posterior inferior cerebellar artery (PICA). At the top of the pons, the basilar artery divides into 2 posterior cerebral arteries (PCAs).

Proximal to its bifurcation into the terminal branches (PCAs), the basilar artery gives off the superior cerebellar arteries that supply the lateral aspect of the pons and midbrain, as well as the superior surface of the cerebellum. The cerebellum is supplied by long circumferential arteries, the PICA, and the anterior inferior and superior cerebellar arteries from the basilar artery.

The medulla is perfused by the PICA and by direct, smaller branches from the vertebral arteries. The pons is perfused by small, penetrating branches from the basilar artery and its major branches. Penetrating arteries from the PCAs perfuse the midbrain and thalamus, and the occipital cortex is perfused by the PCAs.

At the base of the brain, the carotid and basilar systems join to form a circle of large, communicating arteries known as the circle of Willis. Because of this arrangement of collateral vessels, even when one of the main arteries is occluded, adequate perfusion of the brain still may be possible. [3]

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