Vertebral Artery Blood Supply Regions
The vertebral arteries supply the posterior circulation of the brain, including the brainstem (medulla, pons), cerebellum, posterior cerebral hemispheres, and portions of the spinal cord.
Primary Vascular Territories
The vertebral arteries provide blood flow to distinct anatomical regions through their branches and the vertebrobasilar system 1:
Intracranial Branches (V4 Segment)
The fourth segment branches are the most clinically significant and include 1:
- Anterior and posterior spinal arteries - supply the spinal cord
- Posterior inferior cerebellar artery (PICA) - the largest branch, supplying the lateral medulla and inferior cerebellum
- Posterior meningeal artery - supplies the dura
- Small medullary perforating branches - supply the medulla oblongata
Regional Distribution Patterns
Medullary supply is organized into distinct zones 2:
- Medial medulla: Supplied by perforating arteries from the anterior spinal artery (averaging 6.7 vessels)
- Anterolateral medulla: Supplied by anterolateral arteries from the anterior spinal artery and perforators
- Lateral medulla: Supplied by lateral arteries from the vertebral artery and PICA (averaging 2.2 vessels, 0.31mm diameter)
- Dorsal medulla: Supplied by dorsal arteries from PICA and posterior spinal artery
Cerebellar perfusion is predominantly ipsilateral, with relatively little mixing in the vertebrobasilar system 3. The left and right vertebral arteries contribute unequally to posterior circulation, creating asymmetric perfusion patterns.
Clinical Significance
Symptom Patterns from Vertebrobasilar Insufficiency
When vertebral artery occlusive disease occurs, expect these specific symptoms 1:
- Dizziness and vertigo
- Diplopia (double vision)
- Perioral numbness
- Blurred vision
- Tinnitus
- Ataxia (coordination problems)
- Bilateral sensory deficits
- Syncope
Stroke Distribution
Vertebral artery atherosclerosis causes approximately 20% of posterior circulation strokes 1. Lateral medullary infarctions are most common (72.8% of medullary strokes) 2, reflecting the vulnerability of the lateral medullary territory supplied by PICA and vertebral artery branches.
Important Anatomical Considerations
The vertebral arteries join to form the basilar artery at or near the pontomedullary junction (within 7mm in most cases) 4. The anterior spinal artery typically originates 6.5-8.5mm proximal to the vertebrobasilar junction 4.
Critical pitfall: The complex, asymmetric distribution pattern means that unilateral vertebral artery disease may cause symptoms if it affects the dominant vessel, even when the contralateral vertebral artery is patent 1. The vertebral arteries show less uniform perfusion compared to the internal carotid system, creating a "mosaic" pattern of blood distribution 5.
The spinal cord receives continuous blood supply through an uninterrupted anterior spinal artery pathway connecting the vertebral arteries superiorly with the arteria radicularis magna (arising from lumbar arteries in 70.5% of cases) 6.