# Anomalous Origin of the Right Vertebral Artery
###### Abstract  
An anomalous origin of the right vertebral artery (VA) is a rare anomaly that is much rarer than that of the left VA. It can be divided into a few patterns, including aortic origin, right carotid or brachiocephalic arterial origin, and duplicated origin. In embryological development, the VA is made up of a longitudinal anastomosis between cervical segments. The mechanism of the anomalous origin of the right VA can be explained by the persistence of the cervical segmental artery and the regression point of the 4 th right aortic arch. Although the anomaly is usually found incidentally on imaging modalities, it can be a potential cause of complication during surgical and interventional procedures. However, there are a lot of reports about the radiomics of the anomaly. Therefore, we discuss the potential relationship between the anomalous origin of the right VA and radiomics. As the take-home message, understanding several patterns of anomalous origin of the right VA with their embryology and imaging findings is important for surgical and endovascular interventions to avoid intraprocedural complications. vertebral artery; embryology; anomalous origin; subclavian artery; cerebral artery; vascular surgery; endovascular treatment; anatomy +
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origin of the internal carotid artery, and the cranial part of the dorsal aorta beyond the 3 rd arch become the primitive internal carotid artery. The 4 th left arch forms the distal main part of the adult aortic arch. The dorsal aorta gives off the paired segmental arteries from the cervical to the sacral region to supply the developing somites and spinal cord [4]. At the 7-mm stage (day 32), seven cervical segmental arteries (CSAs) appear, originating from each of the paired dorsal aortas accompanying segmental cervical nerves 2-8. According to a study by [PERSON] et al. on the development of the subclavian artery in the rat embryo, a few arterial trunks of the forelembs (primary subclavian artery) arise from the lateral surface of the dorsal aorta at the 6 th-10 th segmental levels to form a vascular network (Figure 1a) [5]. The primary subclavian arteries anastomose with neighboring segmental arteries, and then the origins of those segmental arteries regress. One of the primary subclavian arteries at the level of the 7 th segment becomes thicker, and the others regress. Then, the anastomosis between the primary subclavian artery and the 7 th CSA forms the proximal part of the future vertebral artery. The paired dorsal aorta begins to fuse at the midline to form a single dorsal aorta. The level of fusion of the dorsal aorta transitionally reaches the most cranial point near the third CSA level but shifts down to the origin of the level of the 7 th CSA. The caudal part of the right dorsal aorta (just before its confluence with the left dorsal aorta) regresses, and the right subclavian artery (RSCA) is formed by the remnant part of the right dorsal aorta and the primary subclavian artery. The left subclavian artery is formed by the left primary subclavian artery at the 7 th CSA level. At the 7-mm stage, the primitive VA appears, and its development is usually complete by the 14- to 17-mm stage [4; 5; 6]. At the 10- to 12-mm stage, the postcostal longitudinal anastomosis develops between the CSAs (developing bilaterally from the 1 st to the 7 th CSAs) and becomes the VA [7]. At the 14- to 17-mm stage, the aortic origins of the first 6 CSAs regress, and the 7 th CSA becomes the branches of the SCA. This developmental process results in a normal pattern of development of the VA from the SCA (Figure 1b). As a result of normal development of the arterial system, the right vertebral artery (RVA) usually arises from the right subclavian artery (RSCA) as its first branch at the upper part, just proximal to the origin of the thyrocervical trunk. The RVA enters the transverse foramen of the 6 th cervical spine and runs upward into the posterior fossa through the foramen magnnum.