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Vertebral artery

Paired vertebral arteries provide blood supply for the upper part of the spinal cord, brainstem, cerebellum, and posterior part of the brain. Each artery originates from the first part of the subclavian artery, it then courses superiorly along the sides of the neck, merging with its companion at the pons level to form the single, midline basilar artery. 

Basilar and internal carotid arteries give off multiple communicating branches which anastomose with each other at the base of the brain, forming the hexagonal vascular network called the circle of Willis. The circle of Willis connects the anterior and posterior brain circulations. This reflects the importance of the vertebral artery for the human organism.

Key facts about the vertebral artery
Segments Preforaminal (from subclavian artery to transverse foramen of C6)
Foraminal (through the transverse foramina of C6 to C2)
Extradural (from the transverse foramen of axis to the vertebral canal)
Intradural (from the vertebral canal to the inferior border of pons)
Branches Anterior spinal, posterior spinal, posterior inferior cerebellar, meningeal, medullary, basilar arteries
Clinical relation Stroke

This article will discuss the anatomy, segments and branches of the vertebral artery, as well as most frequent, life-threatening clinical condition related to it.

Contents
  1. Segments
    1. Preforaminal segment
    2. Foraminal segment
    3. Extradural (atlantic) segment
    4. Intradural (intracranial) part
  2. Branches
  3. Clinical relations
    1. Stroke
  4. Sources
+ Show all

Segments

There are four segments of the vertebral artery, following its way through the neck; preforaminal, foraminal, extradural (atlantic), and intradural (intracranial) parts.

Preforaminal segment

The vertebral artery originates from the first part of the subclavian artery, then extends superiorly and posteriorly, passing between the longus colli and the anterior scalene muscles. 

Anterior to it are the vertebral and internal jugular veins, while posteriorly, there are the transverse process of C7 vertebra, the sympathetic trunk, and the superior cervical ganglion.

Foraminal segment

After passing between the longus colli and anterior scalene muscles, the vertebral artery runs superiorly through the transverse foramina of the C6 to C2 vertebrae. It pursues an almost vertical course as far as the transverse process of the axis (C2). 

While passing through the transverse foramina, the vertebral artery is located anterior to the trunks of the cervical spinal nerves. Also, it is surrounded by the venous plexus, which form the vertebral vein at the lower part of the neck.

Extradural (atlantic) segment

This segment begins after the artery passes through the transverse foramen of the axis (C2) where it is subdivided into two parts; vertical and horizontal:

  • Vertical part courses superiorly, crossing the root of the C2 spinal nerve and entering the transverse foramen of the atlas (C1). 
  • After passing through the transverse foramen of atlas, the horizontal part begins. The artery curves medially and posteriorly, passing behind the superior articular process of the atlas and reaches the groove on the upper surface of the posterior arch of the atlas. From there, it passes under the posterior atlantooccipital membrane and enters the vertebral canal. The horizontal part is contained in the occipital triangle. 

Learn more about the triangles of the neck, including the occipital triangle here.

Intradural (intracranial) part

After entering the vertebral canal, the vertebral artery pierces the dura mater and courses superiorly over the anterior surface of the medulla oblongata. At the lower border of the pons, it merges with the opposite vertebral artery and forms the basilar artery. The basilar artery ascends along the ventral surface of the pons in its basilar groove within the pontine cistern. The vessel terminates as it bifurcates into two posterior cerebral arteries.

Branches

Along its course, the vertebral artery gives rise to the following branches:

  • Anterior spinal artery from its intradural segment. This artery originates from two smaller vessels from each vertebral artery which unite around the intradural segment. The anterior spinal artery then passes through the foramen magnum and descends along the anterior aspect of the spinal cord, supplying its anterior portion.
  • May give off the posterior spinal artery; although this vessel usually arises from the posterior inferior cerebellar artery.
  • Posterior inferior cerebellar artery originates from each vertebral arteries’ intracranial segment and supplies the cerebellum.
  • Meningeal branches from its intracranial part near the foramen magnum, for supplying the meninges.
  • Medullary arteries from its intracranial part that supply the medulla oblongata.

The terminating branch of the vertebral artery is the basilar artery. The basilar artery contributes to the circle of Willis. It terminates by bifurcating into two posterior cerebral arteries. Each of these gives off the posterior communicating artery, which anastomoses with the middle cerebral artery, a branch of the internal carotid artery. This is how the communication between vertebral and internal carotid arteries is established.

Test your knowledge on the arteries of the vertebral column with this quiz.

Learn more about basilar artery and circle of Willis with these learning materials.

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