Basilar artery

The basilar artery is a major artery of the posterior cerebral circulation and provides an important blood supply to the brainstem and cerebellum. It is formed by the union of the right and left vertebral arteries at approximately the pontomedullary junction. From its origin, it ascends in the midline within the basilar groove on the ventral surface of the pons, lying in the prepontine cistern. At the upper border of the pons, it terminates by bifurcating into the right and left posterior cerebral arteries (PCAs).

Branches

As it ascends along the pons, the basilar artery gives rise to several important branches:

• Numerous pontine arteries arise directly from it and may be broadly divided into paramedian perforating and circumferential branches (a.k.a. medial and lateral pontine arteries, respectively). These penetrate or pass around the pons to supply its deep and superficial structures.

• The anterior inferior cerebellar artery (AICA) usually arises from the lower part of the basilar artery and supplies the anterior-inferior cerebellum and portions of the lateral caudal pons.

• The labyrinthine artery, which supplies the inner ear, most commonly arises from AICA but may occasionally arise directly from the basilar artery.

• More superiorly, the basilar artery gives rise to the superior cerebellar arteries (SCAs), usually immediately before its terminal bifurcation. The SCA passes around the upper brainstem and predominantly supplies the superior surface of the cerebellum, with branches also contributing to the rostral pons and adjacent midbrain.

• Finally, the basilar artery divides into the posterior cerebral arteries, which supply the occipital lobes, including the visual cortex, as well as inferomedial temporal regions and, through their deep branches, portions of the thalamus and midbrain.

The basilar artery and its branches therefore provide a major arterial supply to the pons, cerebellum and parts of the midbrain, while its terminal PCAs continue the posterior circulation to the cerebral hemispheres and deep cerebral structures.