Which vertebral artery is typically dominant?

Vertebral Artery Dominance

The left vertebral artery is typically dominant in most individuals, with left vertebral dominance occurring in approximately 36.1% of people compared to right vertebral dominance in 25.3%. 1

Anatomical Considerations

The vertebral arteries are critical components of the posterior circulation that supply blood to the brainstem, cerebellum, and posterior cerebral hemispheres. These arteries demonstrate significant anatomical variation:

• Vertebral arteries typically arise from the subclavian arteries, but in approximately 5% of individuals, the left vertebral artery arises directly from the aortic arch 2
• The vertebral arteries are divided into four segments (V1-V4), with the first three being extracranial 2
• Anatomical variations are more common in the vertebral circulation than in the carotid circulation 2

Vertebral Artery Dominance Patterns

Research demonstrates consistent patterns regarding vertebral artery dominance:

• Left vertebral artery dominance (36.1%) is more common than right vertebral artery dominance (25.3%) 1
• The average diameter of vertebral arteries has been measured as 3.21 ± 0.7 mm on the right and 3.16 ± 0.7 mm on the left in some studies 3
• Other studies have found the mean diameter of the left VA (3.41 ± 0.54 mm) to be larger than the right VA (3.14 ± 0.35 mm) 4
• Flow volume measurements also support left dominance, with mean flow volume of 151.45 ± 57.26 mL/min in the left VA compared to 119.21 ± 44.98 mL/min in the right VA 4

Clinical Significance

Vertebral artery dominance has important clinical implications:

• Vertebral dominance and basilar bending are risk factors for brainstem infarction and transient ischemic attacks (TIAs) 5
• In patients requiring aortic repair involving the vertebral artery origin, revascularization is particularly important in patients with a dominant left vertebral artery 2
• The American Heart Association/American College of Cardiology guidelines note that revascularization of the vertebral artery is reasonable in patients undergoing thoracic aortic repair to reduce the risk of vertebrobasilar insufficiency, spinal cord ischemia, and stroke 2

Diagnostic Considerations

When evaluating vertebral artery dominance:

• CTA and contrast-enhanced MRA have higher sensitivity (94%) and specificity (95%) than ultrasonography (sensitivity 70%) for detecting vertebral artery abnormalities 2, 6
• Catheter-based angiography may be required for definitive assessment before revascularization for patients with symptomatic posterior cerebral ischemia 2

Important Caveats

• Vertebral artery hypoplasia occurs in approximately 7.94% of vessels 1
• There is no significant relationship between hand dominance (cerebral hemisphere dominance) and vertebral artery dominance 4
• The right vertebral dominance tends to coincide with left basilar bending, while left vertebral dominance tends to coincide with right basilar bending 5

Understanding vertebral artery dominance is crucial for clinical decision-making, particularly in neurosurgical planning and in patients requiring aortic or vertebral artery interventions.