Vertebral Artery¶

Definition¶

The vertebral arteries are paired vessels that ascend through the transverse foramina of the cervical vertebrae to supply the posterior circulation of the brain and the cervical spinal cord. They are the first and largest branches of the subclavian arteries.

Anatomy¶

Course¶

The vertebral artery is divided into four segments:

• V1 (pre-foraminal) — from its origin at the subclavian artery to the transverse foramen of C6; ascends between the longus colli and anterior scalene muscles
• V2 (foraminal/transverse) — ascends through the transverse foramina from C6 to C2; surrounded by a venous plexus and sympathetic nerve fibers
• V3 (atlantic/extradural) — exits the C1 transverse foramen, curves posteromedially around the lateral mass of the atlas in a groove on the posterior arch, then pierces the posterior atlanto-occipital membrane to enter the vertebral canal
• V4 (intradural/intracranial) — pierces the dura and arachnoid, ascends anterior to the medulla, and joins the contralateral vertebral artery to form the basilar artery at the pontomedullary junction

Key Anatomic Points¶

• The vertebral artery typically enters the transverse foramen at C6, though variants entering at C5, C4, or C7 occur in ~5–10% of individuals
• The V3 segment is the most mobile and vulnerable to injury during cervical manipulation or surgery
• The vertebral arteries are frequently asymmetric — the left is dominant in approximately 50%, the right in 25%, and codominant in 25%
• Branches include the anterior and posterior spinal arteries, posterior inferior cerebellar artery (PICA), and meningeal branches

Imaging Findings¶

Radiography¶

• Vertebral arteries are not visible on plain films
• The transverse foramina may be asymmetric, suggesting vertebral artery dominance

CT¶

• CTA (CT Angiography) is the standard rapid evaluation for vertebral artery pathology
• Demonstrates arterial course, caliber, stenosis, dissection, and anomalous entry level
• Dissection: intimal flap, mural hematoma (crescentic mural thickening), vessel narrowing or occlusion
• Bony CT may show unilateral transverse foramen enlargement in arteriovenous fistulas

MRI/MRA¶

Key Points¶

• The vertebral artery has four segments (V1–V4) and typically enters the transverse foramen at C6
• Vertebral arteries are commonly asymmetric; left dominance is most frequent
• The V3 segment at C1–C2 is most vulnerable to injury during manipulation and surgery
• CTA is the first-line imaging for suspected vertebral artery injury or dissection
• MRI with fat-saturated T1 shows the mural hematoma of dissection as a crescentic bright signal
• Vertebral artery dissection is an important cause of posterior circulation stroke in young adults

References¶

1. Piccinin MA, Munakomi S. Neuroanatomy, Vertebrobasilar System. StatPearls. NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/sites/books/NBK540995/
2. Gailloud P. The segmentation of the vertebral artery: an ambiguous anatomical concept. Interv Neuroradiol. 2022;28(6):765-772. https://pmc.ncbi.nlm.nih.gov/articles/PMC9706265/
3. Bajzer CT. Vertebral artery. In: Guide to Peripheral and Cerebrovascular Intervention. NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK27430/
4. Ergun O, Gunes Tatar I, Birgi E, Hekimoglu B. Evaluation of vertebral artery dominance, hypoplasia and variations in the origin: angiographic study in 254 patients. Folia Morphol (Warsz). 2016;75(1):33-37. https://pubmed.ncbi.nlm.nih.gov/26365867/
5. Radiopaedia — Vertebral artery hypoplasia. https://radiopaedia.org/articles/vertebral-artery-hypoplasia
6. Radiopaedia — Vertebral artery. https://radiopaedia.org/articles/vertebral-artery

Related Articles¶

• Cervical Vertebrae (C1-C7)
• Atlas (C1) and Axis (C2)
• Spinal Arterial Supply
• Craniocervical Junction