Vertebral artery

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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.

Summary

origin: branches off the 1^st part of the subclavian artery
course: ascends posterior to the internal carotid artery in the transverse foramina of the cervical vertebrae
branches
- numerous small branches
- radicular/spinal branches
- posterior inferior cerebellar artery (PICA)
termination: combines with the contralateral vertebral artery to form the basilar artery
key relationships: posterior to the internal carotid artery; ascends anterior to the roots of the hypoglossal nerve (CN XII)

Gross anatomy

Origin

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).

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, extradural or extraspinal): from C2 to the dura
V4 (intradural or intracranial): 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 spinal nerves 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 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 (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~~posteriorly 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

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 4^th ventricle
penetrating branches: portion of the medulla, olives, inferior cerebellar peduncle

Variant anatomy

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%

Related pathology

vertebral artery thrombosis
vertebral artery dissection
rotational occlusion of the vertebral artery (Bowhunter syndrome)

-</ul><h6>V2 (foraminal)</h6><p>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.</p><h6>V3 (atlantic, extradural or extraspinal)</h6><p>V3 emerges from the transverse process of C2 (<a href="/articles/axis-c2">axis</a>), and sweeps laterally to pass through the transverse foramen of C1 (<a href="/articles/atlas-c1">atlas</a>). From here it passes around the posterior border of the lateral mass of C1 and below the inferior border of the <a href="/articles/posterior-atlanto-occipital-membrane-1">posterior atlanto-occipital membrane</a> lateral to the cervico-medullary junction. Passing superomedially it pierces the <a href="/articles/spinal-dura-mater">spinal dura</a> and <a href="/articles/spinal-arachnoid-mater">arachnoid</a> 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 <a href="/articles/atlanto-axial-articulation">atlanto-axial joints</a>.</p><h6>V4 (intradural or intracranial)</h6><p>V4 ascends anterior to the roots of the <a href="/articles/hypoglossal-nerve">hypoglossal nerve (CN XII)</a> and joins its contralateral counterpart at the lower border of the <a href="/articles/pons">pons </a>to form the <a href="/articles/basilar-artery">basilar artery</a>.</p><h5>Branches</h5><p>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 <a href="/articles/eca">ECA</a>.</p><p>Spinal branches, pass into the <a href="/articles/spinal-canal">spinal canal</a> via the <a href="/articles/intervertebral-foramen-1">intervertebral foramina</a> 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.</p><p>The <a href="/articles/posterior-inferior-cerebellar-artery">posterior inferior cerebellar artery</a> (PICA) is the largest branch of the vertebral artery and is one of three main arteries supplying the cerebellum.</p><p>Other branches include:</p><ul>
+</ul><h6>V2 (foraminal)</h6><p>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.</p><h6>V3 (atlantic, extradural or extraspinal)</h6><p>V3 emerges from the transverse process of C2 (<a href="/articles/axis-c2">axis</a>) and sweeps laterally to pass through the transverse foramen of C1 (<a href="/articles/atlas-c1">atlas</a>). From here it passes around the posterior border of the lateral mass of C1 and below the inferior border of the <a href="/articles/posterior-atlanto-occipital-membrane-1">posterior atlanto-occipital membrane</a> lateral to the cervico-medullary junction. Passing superomedially it pierces the <a href="/articles/spinal-dura-mater">spinal dura</a> and <a href="/articles/spinal-arachnoid-mater">arachnoid</a> 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 <a href="/articles/atlanto-axial-articulation">atlanto-axial joints</a>.</p><h6>V4 (intradural or intracranial)</h6><p>V4 ascends anterior to the roots of the <a href="/articles/hypoglossal-nerve">hypoglossal nerve (CN XII)</a> and joins its contralateral counterpart at the lower border of the <a href="/articles/pons">pons </a>to form the <a href="/articles/basilar-artery">basilar artery</a>.</p><h5>Branches</h5><p>Numerous muscular branches are given off as the artery ascends, with relatively large ones passing posteriorly from V3 to supply the occipital triangle. They can anastomose with occipital branches of the <a href="/articles/eca">ECA</a>.</p><p>Spinal branches, pass into the <a href="/articles/spinal-canal">spinal canal</a> via the <a href="/articles/intervertebral-foramen-1">intervertebral foramina</a> 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.</p><p>The <a href="/articles/posterior-inferior-cerebellar-artery">posterior inferior cerebellar artery</a> (PICA) is the largest branch of the vertebral artery and is one of three main arteries supplying the cerebellum.</p><p>Other branches include:</p><ul>

References changed:

1. Ranganatha. The Course of the V1 Segment of the Vertebral Artery. Annals of Indian Academy of Neurology. 2006;9(4):223. <a href="https://doi.org/10.4103/0972-2327.29204">doi:10.4103/0972-2327.29204</a>
8. Alexander M. McKinney. Atlas of Normal Imaging Variations of the Brain, Skull, and Craniocervical Vasculature. (2017) ISBN: 9783319397900 - <a href="http://books.google.com/books?vid=ISBN9783319397900">Google Books</a>
1. Ranganatha Sastry V, Manjunath KY. The course of the V1 segment of the vertebral artery. Ann Indian Acad Neurol 2006;9:223-6
8. McKinney A.M. (2017) Cervical Carotid and Vertebral Arterial Variants. In: Atlas of Normal Imaging Variations of the Brain, Skull, and Craniocervical Vasculature. Springer, Cham

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