Bilateral vertebral arteries arising distal to the left subclavian artery: embryological and anatomical description.

Abnormalities in the origin of vertebral arteries are relatively uncommon, but extremely rare when this abnormality happens on both sides. We present an anatomic variation in which both vertebral arteries came from the proximal descending thoracic aorta beyond the left subclavian artery with no other supra-aortic vessels accompanying the abnormality. The right vertebral artery took a retro-oesophageal course (lusoria artery), while the right and the left vertebral arteries enter the transverse foramina at the 7th cervical vertebra. From an embryological point of view, and overall controversial, this anomaly can be explained by the bilateral persistence of the 8th intersegmental artery as the origin of vertebral artery, instead of the dorsal segment of the 7th intersegmental artery being the origin, which is normally the case. The adequate identification of vertebral artery anomalies in complementary explorations is very important to avoid misdiagnosed vertebral occlusions or unexpected vertebral artery injuries during supra-aortic trunks, thyroid, and oesophagus open surgeries, among others, or even over the course of endovascular procedures.