Vertebral Artery Hypoplasia

Curved reformat of the normal-caliber right vertebral artery showing all 4 segments of the artery. 

Curved reformat of the left vertebral artery shows diffuse, small caliber of the artery.

Facts:

• Operational definitions are either 1) asymmetrical ratio of or greater than 1:1.7, or 2) discrepancy of greater than 2 mm diameter
• Prevalence 2%-6% of population (from autopsy and angiographic series)

Clinical Relevance

• Posterior circulation ischemia: hypoplasia leads to reduction of posterior circulation blood flow velocity therefore has a negative role in occlusion of major cerebral arteries
• Migraine with aura and vestibular neuronitis: hypoplasia is believed to be associated with regional hypo perfusion and complex neurovascular consequences

Reference:

Chuang YM, Chan L, Wu HM, et al. The clinical relevance of vertebral artery hypoplasia. Acta Neurol Taiwan 2012;21:1-7.