Approach to Vascular Conditions

History

Development of the distal vertebral artery (VA) is classically defined by the works of Congdon (1922) and Padget (1948). Contributions of the lateral spinal artery (LSA) were initially defined by Kadyi (1889) but were more recently emphasized by Lasjuanias (1985) and Siclari (2007).

Imaging Anatomy

Three main longitudinal vascular axes supply blood to the spinal cord. Two of these axes are composed of the familiar single anterior spinal artery (ASA) and the 2 posterior spinal arteries (PSAs). The ASA is formed by the junction of small vessels arising from each of the intradural VAs and then extends as a continuous vessel along the ventral spinal cord in the ventral median sulcus. The PSAs arise from the extracranial VAs or from the posteroinferior cerebellar artery (PICA) proper and course along the posterolateral surface of the cord as more of an anastomotic chain or arterial plexus than as single dominant vessels (as is seen with the ASA).

In the upper cervical spine, the LSA is a 3rd longitudinal axis, complementing the ASA and PSA. The LSA lies on the lateral aspect of the spinal cord. This vessel is located ventral to the dorsal cervical roots and runs parallel to the spinal component of the spinal accessory nerve (CNXI). The cephalad extension of the LSA ends at the intradural VA (V4) at the C1 level, or at the PICA proper. The caudal limit of the LSA extends to C4 or C5 where the LSA turns posteriorly to the spinal roots and joins the PSA.

Embryology

The embryo develops 6 pairs of aortic arches. The arches undergo selective regression (apoptosis) with the residual arches forming the adult aortic arch and great vessels. Normally, the 1st and 2nd sets of arches regress, and the 3rd arches form the proximal internal carotid arteries (ICAs). The proximal 4th arch forms the right subclavian artery. The bulk of the left 4th arch regresses to end up forming a small portion of the adult arch between the left common carotid artery origin and left subclavian artery. The 5th arches regress. The 6th arch forms the right pulmonary artery and the ductus arteriosus.