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Topic

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Right vertebral artery (atlantic part)

The atlantal part of the right vertebral artery, also known as the V3 segment, is the portion of the vertebral artery that extends from the transverse foramen of the axis (C2), curves laterally and posteriorly around the posterior arch of the atlas (C1), and enters the foramen magnum. This segment is tortuous and mobile, allowing head rotation without compromising blood flow.

It lies posterior to the lateral mass of the atlas, running in a groove on the posterior arch of C1, and is closely related to the suboccipital nerve, venous plexus, and bony structures of the atlanto-occipital region. This segment is clinically significant due to its susceptibility to compression, dissection, or injury during trauma or cervical spine surgery.

Function

  • Supplies blood to the posterior circulation of the brain, including the brainstem, cerebellum, and posterior cerebral hemispheres

  • Maintains collateral circulation with the contralateral vertebral artery

  • Allows mobility of the neck without compromising arterial flow

  • Participates in formation of the basilar artery for cerebral perfusion

Synonyms

  • Vertebral artery V3 segment

  • Atlantal vertebral artery

  • Posterior cervical segment of vertebral artery

MRI Appearance

T1-weighted images:

  • The artery appears as a flow void (hypointense tubular structure) within surrounding fat and muscle

  • The vessel wall is isointense to surrounding structures, while the lumen shows signal void due to rapid flow

  • Vessel course along the posterior arch of C1 can be traced in sagittal and axial planes

T2-weighted images:

  • The lumen remains flow void (black)

  • Perivascular structures such as veins, muscles, and bone marrow are intermediate to high signal, highlighting the artery’s path

  • T2 can demonstrate perivascular edema or aneurysmal dilation if present

STIR (Short Tau Inversion Recovery):

  • Flow void persists in normal vessels

  • Perivascular edema or inflammation appears hyperintense, useful in trauma or dissection assessment

T1 Post-Contrast (Gadolinium-enhanced):

  • The lumen enhances brightly, delineating the artery’s course

  • Useful for detecting dissection, stenosis, aneurysms, or abnormal collateral vessels

  • Outer vessel wall may enhance if there is vasculitis or inflammatory changes

CT Appearance:

  • The atlantal part is visualized as a hyperdense tubular structure with contrast on CT angiography

  • Bony landmarks, including C1 posterior arch groove, are clearly delineated

  • Non-contrast CT may not directly show the artery but allows assessment of adjacent fractures, bony compression, or canal encroachment

MRI images

Right vertebral artery (atlantic part) mri coronal image -img-00000-00000_00001

MRI images

Right vertebral artery (atlantic part) mri axial image