Developmental anatomy of the distal vertebral artery in relationship to variants of the posterior and lateral spinal arterial systems.

BACKGROUND AND PURPOSE A certain number of anatomic variants involving the distal vertebral artery (VA) are explained by variations in size and connection of the lateral spinal artery (LSA). This study examined the possible role of another branch of the VA, the posterior spinal artery (PSA), in the development of similar vascular variations. MATERIALS AND METHODS Four types of variations in the distal VA, including the C1 and C2 origins of the posterior inferior cerebellar artery (PICA), the duplication of the distal VA, and the aberrant course of the distal VA, are illustrated by 9 angiographic observations. RESULTS For each type of VA variant listed above, examples resulting from variations in size and connection of the LSA and PSA could be matched. CONCLUSION Variation in size and connection of the PSA is at the origin of a set of anatomic variations of the distal VA similar, but not identical, to the vascular variants linked to the LSA.