Normal and Abnormal Development of Left Vertebral Artery and its Implications in Cervical Region Surgery.

Anomalies occur in branches arising from the aortic arch (AA) in approximately 3-5% of cadaveric cases (Lazaridis et al. 2018; Natsis et al. 2021), and these atypical branches remain a point of discussion in cervical neck surgery. Here, we describe a 73-year-old Caucasian female who died of renal failure following a complicated urinary tract infection whose left vertebral artery (VA) originated from the AA between the left common carotid and subclavian arteries. The preforaminal part of the left VA was 3.5 mm in diameter and entered the C5 transverse foramen while the right VA arising from the right subclavian artery was 4.2 mm in diameter and entered the C5 transverse foramen normally. Embryologically, the VAs are formed during weeks 4 through 8 by development of longitudinal anastomoses linking the cervical intersegmental arteries (ISA). The ISA regresses except the seventh, which becomes the proximal subclavian artery, the point of origin of the adult VA. Persons with left VAs that arise from the AA may be asymptomatic; however, secondary dilatation of the right VA may be implicated in the development of cerebrovascular disorders and atherosclerotic changes due to increased blood flow. Additionally, the recognition of the anomalous origin and anatomical positioning of a left VA is important when considering an anterior approach for cervical spine surgery (Tardieu et al. 2017) and other head-neck procedures when soft structures such as arteries, veins and muscles are retracted to reach the cervical spine.