Basilar artery

At a glance

English

Basilar artery

Latin (TA2)

Arteria basilaris

System

Artery

Region

Head

Side

Single, on the midline

About the basilar artery

The basilar artery is a single, unpaired vessel at the base of the brain. It forms where the right and left vertebral arteries meet, at the lower border of the pons where it joins the medulla oblongata. Together the vertebral and basilar arteries make up the vertebrobasilar system, which supplies the posterior part of the brain and links with the internal carotid supply through the arterial circle at the base of the brain (circle of Willis).

The artery runs upwards in the shallow basilar groove on the front of the pons, lying on the clivus of the skull behind it, with the abducens nerves near its lower end. Its calibre varies widely, from about 1.5 to over 6 mm. At the upper border of the pons, where the pons meets the midbrain, it divides into the two posterior cerebral arteries, close to the oculomotor nerves, which pass between the posterior cerebral and superior cerebellar arteries.

Its branches, from below upwards, are the paired anterior inferior cerebellar arteries; the labyrinthine (internal auditory) arteries, which more often come from the anterior inferior cerebellar arteries; many small pontine arteries that pierce the pons; and the superior cerebellar arteries just below the terminal division. Through these and its terminal branches it supplies the pons, parts of the midbrain, the cerebellum, the inner ear and, via the posterior cerebral arteries, the occipital lobes, much of the thalamus and the undersurface of the temporal lobes.

Because so much of the brainstem depends on one vessel, blockage of the basilar artery is serious. A clot here can damage the front of the pons, cutting the motor pathways to the body and face while sparing consciousness and some eye movements, a state called locked-in syndrome. Smaller branch occlusions cause crossed signs, with cranial nerve palsies on one side and weakness on the other. Aneurysms commonly form at its tip, where it divides, and its pulsation can occasionally compress nearby cranial nerves.

Course and supply

Arises from

Formed by union of the right and left vertebral arteries at the lower border of the pons.

Ends in

Divides at the upper border of the pons into the right and left posterior cerebral arteries.

Supplies

Supplies the pons, upper brainstem, cerebellum and inner ear, and through the posterior cerebral arteries the occipital lobes, thalamus and inferior temporal lobes.