Vertebral artery

The vertebral arteries (VA) are paired arteries, each arising from the respective subclavian artery and ascending in the neck to supply the posterior fossa and occipital lobes, as well as provide segmental vertebral and spinal column blood supply.

The origin of the vertebral arteries is usually from the posterior superior part of the subclavian arteries bilaterally, although the origin can be variable:

  • brachiocephalic artery (on the right)
  • aortic arch: 6% of cases, most on the left

The VA is normally 3-5 mm in diameter and the ostium is the most common site of stenosis. 

When the origin is from the arch, then it is common for the artery to enter the foramen transversarium at a level higher than normal (C5 instead of C6). 

The vertebral artery is typically divided into 4 segments:

  • V1 (preforaminal): origin to transverse foramen of C6
  • V2 (foraminal): from the transverse foramen of C6 to the transverse foramen of C2
  • V3 (atlantic, extradural or extraspinal): from C2 to the dura
  • V4 (intradural or intracranial): from the dura to their confluence to form the basilar artery

Also known as the extraosseous segment, V1 arises from the first part of the subclavian artery. It angles posteriorly between longus colli medially and scalenus anterior laterally, through the colliscalene triangle, and behind the common carotid artery to enter the transverse foramen of C6.


V2 ascends through the transverse foramina of the cervical vertebrae, normally C6-C3. Here it is accompanied by vertebral veins and sympathetic nerves. It then turns superolaterally through the inverted L-shaped transverse foramen of C2.

V3 emerges from the transverse process of C2 (axis), and sweeps laterally to pass through the transverse foramen of C1 (atlas). From here it passes around the posterior border of the lateral mass of C1 and below the inferior border of the posterior atlanto-occipital membrane lateral to the cervico-medullary junction. Passing superomedially it pierces the spinal dura and arachnoid to continue as V4. This tortuosity provides length and freedom for the vessel to stretch, straighten and bend during rotation of the head, which occurs at the atlanto-axial joints.

V4 ascends anterior to the roots of the hypoglossal nerve (CN XII) and joins its contralateral counterpart at the lower border of the pons to form the basilar artery.

Numerous muscular branches are given off as the artery ascends, with relatively large ones passing posterior from V3 to supply the occipital triangle. They can anastomose with occipital branches of the ECA.

Spinal branches, pass into the spinal canal via the intervertebral foramina and contribute to supply not only of the vertebral bodies and extradural content of the canal but also of the dura and spinal cord, reinforcing the anterior and posterior spinal arteries.

The posterior inferior cerebellar artery (PICA) is the largest branch of the vertebral artery and is one of three main arteries supplying the cerebellum.

Other branches include:

  • V1: segmental cervical muscular and spinal branches
  • V2: anterior meningeal artery, muscular and spinal branches
  • V3: posterior meningeal artery
  • V4: anterior and posterior spinal arteries (ASA and PSA), perforating branches to medulla, posterior inferior cerebellar artery
  • ASA: upper cervical spinal cord, inferior medulla
  • PSA: dorsal spinal cord to conus medullaris
  • PICA: lateral medulla, tonsil, inferior vermis/cerebellum, choroid plexus of 4th ventricle
  • penetrating branches: portion of the medulla, olives, inferior cerebellar peduncle
  • asymmetry due to vertebral arterial hypoplasia, absence or termination into PICA of one of the vertebral arteries is very common
    • left dominant ~45% (range 42-50%)
    • right dominant ~30% (range 25-32%)
    • co-dominant ~25% (range 25-26%)
  • complete or partial vertebral artery duplication
  • vertebral artery fenestration (predisposes to aneurysms)
  • variable origin
    • single left aberrant origin (86%), single right aberrant (12%), bilateral aberrant origin (3%) 8
    • aortic arch origin of left vertebral artery: incidence ~5% (range 3.1-8.3%)
    • second (not first) branch of subclavian artery
    • external carotid artery (rare) 8, 9 - see case 14
    • common carotid artery (rare) 9 - see case 15
    • internal carotid artery (rare) 9
  • ostium may have variable orientation
    • cranial ~47%
    • posterior ~45%
    • caudal ~5%
    • anterior ~3%
Anatomy: Brain
Anatomy: Spine
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Article information

rID: 4858
Section: Anatomy
Synonyms or Alternate Spellings:
  • Vertebral arteries

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Cases and figures

  • Figure 1: vertebral artery
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  • Figure 2: vertebral artery
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  • Figure 3: normal COW anatomy
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  • Case 1: vertebral arteries: 3D recon
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  • Case 2: aortic origin
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  • Case 3
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  • Case 4: V4 segments uniting to form basilar artery
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  • Case 5: fenestration
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  • Case 6: aortic arch origin of left VA
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    Case 7: tortourous course of vertebral arteries
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  • Case 8: hypoplastic VA terminating into PICA
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  • Case 9: hypoplastic VA
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  • Case 10: 3D VR
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  • Case 11: partial duplication
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  • Case 12: hypoplastic vertebral terminating into PICA
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  • Case 13: variant origin course of the left vertebral artery
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  • Case 14: ECA origin
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  • Case 15: CCA origin
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