Variable anatomic configuration of the posterior spinal arteries in humans

Posterior spinal arteries (PSAs) arise from the vertebral (VA) or posterior inferior cerebellar (PICA) artery. We identified variations in their origins and their anastomosis with the first posterior radiculomedullary branches in human spinal cords. Spinal cords from male and female cadavers (n = 30) were injected with colored latex through the vertebral, ascending cervical, costocervical trunk and segmental arteries. Specimens were fixed in formalin and the spinal arteries were dissected under a surgical microscope. PSAs arise from the PICA and from the atlantoaxial (V3) or intracranial (V4) segments of the VA. Their origins can be at V3 between the axis and the transverse processes of the atlas (V3i) or between the processes and the occipital bone (V3s). Half of our specimens exhibited a symmetrical and half an asymmetrical origin of the PSAs. A symmetrical origin from V4 was the most common configuration, identified in 30% of specimens. There was a symmetrical origin from either segment of V3 or PICA in 10%. Asymmetrical configurations were observed from V4/V3 (23.7%), V3/PICA (16.7%), V4/PICA (6.7%) and V3i/V3s (3.3%). PSAs are supplied by the posterior radiculomedullary arteries along the spinal cord. The first of these anastomoses could be located at any level between C4 and T8, though most commonly at C6-C7 or T3-T4. PSAs can originate from either the VA or the PICA in a symmetrical or asymmetrical configuration. Variations in the origin and level of the first posterior radiculomedullary anastomosis could affect surgical approaches, endovascular procedures, and the posterior spinal cord's susceptibility to ischemia. Clin. Anat. 31:1137-1143, 2018. © 2018 Wiley Periodicals, Inc.