How common is unilateral vertebral artery hypoplasia?
Relatively common, although there is wide variation in the estimated prevalence due to the varying definition of hypoplasia and mode of assessment. For example, using a threshold of between <2 to 3 mm intraluminal diameter, the reported frequency of unilateral vertebral artery hypoplasia in healthy subjects has been reported to be between 1.9% and 27% (see reference 2).
CT angiography performed in order to evaluate for carotid artery atherosclerosis shows moderate-to-severe atherosclerotic narrowing of both carotid bulbs with evidence of ulceration. There is a second short segment severe stenosis of the right cervical segment internal carotid artery.
Incidentally, the left vertebral artery originates directly from the proximal external carotid artery. A diminutive right vertebral artery originates from the right brachiocephalic artery.