Variant of Left Vertebral Artery Origin and Transverse Foramina Entry

Background: Variations in the origin, course, and transverse foramina entry of the left vertebral artery(LVA) are well documented in literature. The LVA usually originates from the left subclavian artery and courses through the neck to enter at the C6 transverse foramina. While variants of the LVA are not known to cause pathological problems, knowledge of the common variants is of great use to diagnostic radiologists, interventional radiologists, and cardiologists. Case Information: During routine dissection of a 67 year-old white female cadaver, a variant left vertebral artery was discovered. This variant was found to branch off the arch of the aorta between the left common carotid and left subclavian artery, instead of its typical origin from the left subclavian artery. Additionally, we noted that the LVA entered at the transverse foramina of the C4 vertebrae instead of its usual entry point at C6. Although a complete medical history was unable to be obtained, no other significant arterial variants were noted. However, the cadaver did possess extensive right lower extremity varicose veins, which we suspect are unrelated. The cause of death was noted to be metastatic pancreatic cancer. Conclusions: This study serves to add to the expanding body of knowledge surrounding anatomical variations of the vertebral artery including its origins and transverse foramina entry point locations. The left vertebral artery originating from the aortic arch occurs in approximately 6% of the population, but these variations are not recognized to cause problems for those individuals, assuming there is no hypertrophy or atrophy of the arterial wall. The transverse foramina entry point in this cadaver was noted to be C4, higher than the normal C6 entry point. Komiyama et al. found an incidence of dissection of 1.7% for vertebral arteries arising from the aortic arch, as opposed to .9% in the general population for those with the appropriated normal anatomy. While the exact reason has yet to be elucidated, it is hypothesized that this is due to the association of vertebral arteries off the aortic arch traveling farther in the neck to C3 and C4, thus predisposing individuals to increased stress on the vasculature allowing for dissection. For these reasons diagnostic radiologists, interventional radiologists, and cardiologists should be acutely aware of the common variants to improve diagnosis, treatment, and reduce potential complications.