Vertebral artery

The vertebral artery (VA) arises from the subclavian artery, ascends in the neck to supply the posterior fossa and occipital lobes as well as provides segmental vertebral and spinal column blood supply.

Summary

Gross anatomy

Origin

The origin of the VA 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

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). 

Segments

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 or extradural): from C2 to the dura
  • V4 (intradural): from the dura to their confluence to form the basilar artery
Course
V1 (preforaminal)

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.

Relations:

  • anteriorly: common carotid artery, vertebral vein, thoracic duct (left VA) and lymphatic duct (right VA)
  • posteriorly: ventral rami of C7 and C8, transverse process of C7, inferior cervical ganglion
  • anteromedially: inferior thyroid artery, middle cervical ganglion
V2 (foraminal)

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 (atlantic, extradural or extraspinal)

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 dura and arachnoid to continue as V4.

V4 (intradural or intracranial)

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.

Branches

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 vertebral 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
Supply
  • 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 medulla, olives, inferior cerebellar peduncle

Variant anatomy

  • asymmetry due to 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 
  • variable origin
    • aortic arch origin of left vertebral artery: incidence ~5% (range 3.1-8.3%)
    • may be the second (not first branch) of the subclavian artery
  • ostium may have variable orientation
    • cranial ~47%
    • posterior ~45%
    • caudal ~5%
    • anterior ~3%

Neuroanatomy
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Article Information

rID: 4858
Section: Anatomy
Synonyms or Alternate Spellings:
  • Vertebral arteries
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    Figure 1: vertebral artery
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    Case 1: vertebral arteries: 3D recon
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    Figure 2: vertebral artery
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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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    CE-MRA AP MIP
    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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