Overview

The artery is divided into four segments. V1 runs from the subclavian artery up to the transverse foramen of C6. It lies behind the common carotid artery, between longus colli and the anterior scalene. V2 climbs through the transverse foramina of C6 to C2, surrounded by a venous plexus and sympathetic fibres. V3 curves backward around the lateral mass of the atlas and lies in a groove on its posterior arch, in the suboccipital triangle. V4 pierces the dura, runs up in front of the medulla and joins the opposite vertebral artery at the junction of the pons and medulla to form the basilar artery.

The two arteries are often unequal in size, and the left is more often the larger (dominant) one.

Anatomy

Course: It runs from the first part of the subclavian artery through the transverse foramina of C6 to C1, around the atlas and through the foramen magnum, to join its partner at the pontomedullary junction.
Branches: Spinal (radicular) and muscular branches in the neck, and meningeal branches. Inside the skull: the anterior spinal artery (the two vertebral contributions unite), the posterior spinal arteries (often from PICA) and the posterior inferior cerebellar artery (PICA), its largest branch.

Function

Supplies the cervical spinal cord, the medulla and the cerebellum (through PICA).
Forms the basilar artery, which supplies the brainstem, cerebellum, occipital lobes and thalami.

Clinical significance

Lateral medullary (Wallenberg) syndrome

Occlusion of the vertebral artery or PICA infarcts the lateral medulla. The result is loss of pain and temperature sensation on the same side of the face and the opposite side of the body, an ipsilateral Horner syndrome, difficulty swallowing and hoarseness (nucleus ambiguus), vertigo and ipsilateral ataxia.

Subclavian steal

A stenosis of the subclavian artery before the vertebral artery's origin can reverse flow down the vertebral artery when the arm is exercised. Blood is "stolen" from the brain, causing dizziness, together with arm claudication and a lower blood pressure in that arm.

Vertebral artery dissection

Neck trauma or chiropractic manipulation can tear the vertebral artery. This causes neck and occipital pain and, in young patients, posterior circulation stroke.

Compiled from standard anatomy and physiology references — see the Cardiovascular System sources. For education only; not medical advice.