Arteries of Spinal Cord

The radicular arteries arise from the lateral spinal arteries, which traverse the intervertebral foramina at each vertebral segment. Regardless of their origin, the many small radicular arteries pass medially to supply the anterior and posterior nerve roots. Most do not reach the spinal cord. However, some of the larger arteries reach the dura mater, where they give off small meningeal branches and then divide into ascending and descending branches to form the spinal arteries. The larger radicular arteries, which supply both the nerve roots and the spinal cord, are called radiculomedullary arteries to distinguish them from those radicular arteries that supply only the nerve roots.

The anterior spinal artery lies within the pia and runs the entire length of the spinal cord in the midline. It usually originates in the upper cervical region at the junction of the two anterior spinal branches that arise from the intracranial portion of the vertebral artery. Six to ten feeders—the anterior radiculomedullary arteries—contribute to it throughout its length, branching upward and downward. Occasionally, in the thoracic region, the anterior spinal artery narrows to such a degree that it is discontinuous. Blood from the anterior spinal artery is distributed to the anterior two thirds of the substance of the spinal cord via central (or sulcocommissural) branches and penetrating branches from the pial plexus.

The cervical and first two thoracic segments of the spinal cord are supplied by radiculomedullary arteries that arise from branches of the subclavian artery. Variability is common, and the branches may arise from either the right or the left (often alternately) to join the anterior spinal artery at an angle of 60 degrees to 80 degrees. Not uncommonly, one anterior radiculomedullary branch arises from the vertebral artery and accompanies the C3 nerve root, one branch arises from one of the branches of the costocervical trunk (often the deep cervical artery) and accompanies the C6 root, and one branch arises from the superior intercostal artery and accompanies the C8 root.

The midthoracic region of the spinal cord (T3 to T7) usually receives only one radiculomedullary artery, which accompanies the T4 or T5 nerve root. Consequently, this section of the cord is characterized by its poor blood supply, and the anterior spinal artery may not be continuous at this level.

The thoracolumbosacral part of the spinal cord (T8 to the conus medullaris) derives its main arterial supply from the artery of Adamkiewicz, which arises from a left intercostal (or lumbar) artery in 80% of individuals. In 85% of instances, it reaches the cord with a nerve root between T9 and L2; in the 15% of cases in which it reaches the cord between T5 and T8, it is supplemented by a radiculomedullary artery (the artery of the conus medullaris) arising more inferiorly. The artery of Adamkiewicz has a large anterior and a smaller posterior branch. On reaching the anterior aspect of the spinal cord, the anterior branch ascends a short distance and then makes a hairpin turn to give off a small ascending branch and a larger descending branch, which drops to the level of the conus medullaris, where it forms an anastomotic circle with the terminal branches of the two posterior spinal arteries.

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