It then curves superiorly passing immediately lateral to the lateral mass of C2 and the lateral C1/2 articulation before it passes through the transverse foramen of C1 ( atlas). V3 ascends from the curved transverse foramen of C2 ( axis) and sweeps laterally over the transverse process. It then turns superolaterally through the inverted L-shaped transverse foramen of C2. Here it is accompanied by the vertebral veins and the sympathetic nerves. V2 ascends through the transverse foramina of the cervical vertebrae, normally C6-C3. Posteriorly: ventral rami of spinal nerves C7 and C8, transverse process of C7, inferior cervical ganglionĪnteromedially: inferior thyroid artery, middle cervical ganglion 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.Īnteriorly: common carotid artery, vertebral vein, thoracic duct (left VA), and lymphatic duct (right VA) from the dura at the lateral edge of the posterior atlanto-occipital membrane to their confluence on the medulla to form the basilar arteryĪlso known as the extraosseous segment, V1 arises from the first part of the subclavian artery. Starts from C2, where the artery loops and turns lateral to ascend into the transverse foramen V3: atlantic, extradural or extraspinal segment from the transverse foramen of C6 to the transverse foramen of C2 The vertebral artery is typically divided into 4 segments: Rarely, the right vertebral artery can have an aberrant origin distal to the left subclavian see vertebral arteria lusoria.
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 VA is normally 3-5 mm in diameter and the ostium is the most common site of stenosis. The origin of the vertebral arteries is usually from the posterior superior part of the subclavian arteries bilaterally, although the origin can be variable:Īortic arch: 6% of cases, most on the left Key relationships: posterior to the internal carotid artery ascends anterior to the roots of the hypoglossal nerve (CN XII) Termination: combines with the contralateral vertebral artery to form the basilar artery Posterior inferior cerebellar artery (PICA) Origin: branches of the 1 st part of the subclavian arteryĬourse: ascends posterior to the internal carotid artery in the transverse foramina of the cervical vertebrae
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