Anatomical variation of the origin of the left vertebral artery from the arch of aorta

Introduction The vertebral artery (VA) normally arises from the superoposterior aspect of the first part of the subclavian artery. It enters through the foramen transversarium of the 6th cervical vertebra, then passes upwards through the foramina in the transverse processes of all of the cervical vertebrae above, curves medially behind the lateral mass of the atlas and enters the cranium via the foramen magnum. At the lower pontine border, it joins its fellow to form the basilar artery, thus supplying the brainstem and the posterior part of cerebrum [1]. The segment of the artery from its origin at the subclavian artery to the foramen transversarium of the 6th cervical vertebra is called as the pretransverse or prevertebral segment [2]. The course and variability in the origin of left vertebral artery and its importance in cerebral disorders has been described clinically [3] and surgically [4]. Its importance in head and neck surgery, angiography and arterial dissection has also been mentioned in the literature [5].