Article Figures & Data
Figures
- Fig 1.
DSA images in a 53-year-old man who was examined for a subarachnoid hemorrhage.
A, Aortic arch, left anterior oblique view. On this early arterial-phase image, both carotid axes and both subclavian arteries are well opacified with the contrast agent. The LVA (L) and RVA (R) arise bilaterally from the aortic arch and are opacified, with some delay, when compared with the other supra-aortic trunks. Note that the origin of both VAs is located between the left common carotid and left subclavian arteries (arrows).
B, Aortic arch, left anterior oblique view. This later arterial-phase image shows complete opacification of the VAs and allows better appreciation of their proximal segments.
C, Right internal carotid artery, lateral view. This angiogram shows a small saccular aneurysm located at the A2-A3 junction of the right anterior cerebral artery (arrow). Note the presence of a large right posterior communicating artery and retrograde filling of the distal basilar artery, with opacification of the right superior cerebellar artery (arrowhead). A similar filling pattern was observed on the left side.
- Fig 2.
Schematic representation of the embryologic mechanisms underlying anatomic variants of the VA origin.
Top left, Normal embryologic development. The aortic sac (AS) is connected with the left and right dorsal aortas (DA) via the aortic arches. The first (I), second (II), third (III), and fourth (IV) aortic arches are illustrated. The segment of the DA located between the third and fourth aortic arches is called the ductus caroticus (DC). The left neural axis (LNA) and right neural axis (RNA), which later become the VAs, result from the formation of longitudinal connections linking the intersegmental arteries (only the sixth and seventh intersegmental arteries are depicted here). The ventral pharyngeal artery (VPA) arises from the third aortic arch. It later constitutes the external carotid artery trunk.
Top middle, Normal anatomy in adults. Bilateral regression of the DC separates the common carotid arteries from the subclavian artery on the right side and from the aortic arch on the left side. The LVA and RVA arise from the ipsilateral subclavian arteries (SCA), which are derived from the seventh intersegmental arteries. The AS has evolved into the innominate artery (I) and aortic arch (AA). On each side, the third aortic arch and the distal dorsal aorta constitute the carotid axis, which is divided into the common and internal carotid arteries by the origin of the external carotid artery from the third arch.
Top right, Double origin of the LVA. If both the sixth and seventh intersegmental arteries persist, the LVA has a double origin from the left subclavian artery and aortic arch. A similar mechanism on the right side usually results in a double origin of the RVA from the right subclavian artery.
Bottom left, Aortic origin of the LVA. If the sixth intersegmental artery persists instead of the seventh, the LVA has a single origin from the aortic arch, between the left common and subclavian arteries.
Bottom middle, Aortic origin of the RVA (aberrant RVA). This variant involves the persistence of the proximal right dorsal aorta, which links the RVA to the thoracic aorta distal to the left subclavian artery. If the right fourth aortic arch involutes as well, the right subclavian artery stays connected to the descending thoracic aorta (aberrant right subclavian artery or arteria lusoria).
Bottom right, Bilateral arch origin of the VAs (reported case). The LVA arises from the arch because of the persistence of the sixth intersegmental artery instead of the seventh. The RVA arises from the arch proximal to the left subclavian artery by means of an hypothetic mechanism that involves the initial origin from the descending thoracic aorta distal to the left subclavian artery (as in bottom middle), which is followed by proximal migration of the RVA origin between the left common carotid and subclavian arteries.
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