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Vertebral artery

The vertebral artery (VA) is a major cervical vessel that arises from the subclavian artery and ascends through the neck to supply the posterior circulation of the brain, including the brainstem, cerebellum, and occipital lobes. It is divided into four anatomical segments—V1 (pre-foraminal), V2 (foraminal), V3 (atlantic), and V4 (intracranial)—each with distinct relationships to bones, muscles, and neural structures.

Its long, protected course through the transverse foramina of the cervical spine and its curvature around the atlas make it essential but also susceptible to injury in trauma, hyperextension, rotation, or degenerative disease.

Synonyms

  • VA

  • Vertebral trunk

  • Posterior cervical artery

Origin, Course, and Termination

Origin:

  • Arises from the posterosuperior aspect of the subclavian artery (usually first part).

Course (Segments):

  • V1 (Pre-foraminal): From origin to entry into C6 transverse foramen.

  • V2 (Foraminal): Ascends through transverse foramina of C6–C2.

  • V3 (Atlantic/Extracranial): Exits C2, curves around posterior arch of C1, enters dura.

  • V4 (Intracranial): Pierces dura, ascends to pontomedullary junction to join opposite VA forming basilar artery.

Termination:

  • Joins the opposite vertebral artery to form the basilar artery.

Relations

  • V1: Adjacent to scalene muscles, longus colli, cervical sympathetic chain.

  • V2: Surrounded by transverse foramina, vertebral venous plexus, cervical nerve roots.

  • V3: In groove on posterior arch of atlas; close to suboccipital triangle muscles.

  • V4: Near medulla, cerebellar arteries, and lower cranial nerves.

Function

  • Supplies posterior circulation: brainstem, cerebellum, occipital lobes.

  • Provides important spinal branches to cervical spine and cord.

  • Contributes to vertebrobasilar anastomotic systems.

Clinical Significance

  • Dissection risk due to long course and rotational stresses.

  • Compression from osteophytes or foraminal narrowing in cervical spondylosis.

  • Trauma sensitivity in high-speed injuries or chiropractic manipulation.

  • Atherosclerosis commonly affects V4 segment.

  • Critical in posterior circulation stroke evaluation.

MRI Appearance

T1-weighted images

  • Normal lumen: Appears as a dark flow void due to rapid flowing blood.

  • Wall: Thin, low-signal margin when visible.

  • Perivascular fat: Bright, outlining the artery in the neck.

  • Vertebral foramina: Seen as low-signal cortical bone surrounding the vessel.

T2-weighted images

  • Lumen: Persistent flow void (dark).

  • Vessel wall: Low signal; surrounding soft tissues are brighter.

  • Foraminal segment (V2): Seen in contrast to the high-signal vertebral venous plexus around it.

  • Intracranial V4: Flow void within bright CSF background.

STIR

  • Normal artery: Dark flow void, sharply demarcated.

  • Surrounding fat: Efficiently suppressed, enhancing vessel conspicuity.

  • Adjacent muscle: Intermediate-to-dark signal providing contrast.

T1 FAT-SAT POST-CONTRAST

  • Lumen: Bright homogeneous intraluminal enhancement.

  • Wall: Thin rim may enhance slightly depending on resolution.

  • Neck segments: Surrounding fat suppressed, improving vessel clarity.

  • Intracranial segment: Enhances vividly against suppressed CSF spaces.

CT Appearance

Non-Contrast CT

  • Lumen: Soft-tissue density; flow not directly visualized.

  • Wall: May show calcification in older patients.

  • Bony relations:

    • Clear course through transverse foramina

    • C1 groove well visualized in V3 segment

  • Utility: Detects bone abnormalities, fractures, foraminal stenosis.

Post-Contrast CT

  • Artery: Bright tubular enhancement along its entire course.

MRI image

Vertebral artery MRI AXIAL

CT image

Vertebral artery (cervical part) CT axial image-img-00000-00000

CT image

Vertebral artery CT CORONAL