Blood Vessels of the Spinal Cord
The spinal cord is supplied with blood from two sources, the vertebral arteries and the segmental arteries (intercostal arteries and lumbar arteries).
Vertebral arteries (A1).Before they unite,they give off two thin posterior spinal arter-ies that form a network of small arteriesalong the posterior surface of the spinal cord. At the level of the pyramidal decussa-tion, two additional branches of the verte-bral arteries join to form the anterior spinalartery (AD2) which runs along the anteriorsurface of the spinal cord at the entrance to the anterior sulcus.
Segmental arteries (C3).Their posteriorbranches (C4) and the vertebral arteries give off spinal branches (C5) which enter through the intervertebral foramina and divide at the spinal roots into dorsal and ventral branches to supply the spinal roots and the spinal meninges. Of the 31 spinal arteries, only 8 to 10 extend to the spinal cord and contribute to its blood supply. The levels at which the radicular arteries approach the spinal cord vary, and so do the sizes of the vessels. The largest vessel approaches the spinal cord at the level of the lumbar en-largement between T12 and L3 (large radicu-lar artery) (A6).
The anterior spinal artery is widest at the level of the cervical and lumbar enlargements. Its diameter is much reduced in the mid-thoracic region of the spinal cord. As this re-gion is also the border area between two supplying radicular arteries, this segment of the spinal cord is especially at risk in case of circulatory problems (A, arrow). Depending on the variation of the radicular arteries, this may also apply to other segments of the spinal cord.
The anterior spinal artery gives off numer-ous small arteries into the anterior sulcus, the sulcocommissural arteries (D7). In the cer-vical and thoracic spinal cords, they turn al-ternately to the left and right halves of the spinal cord; in the lumbar and sacral spinal cords, they divide into two branches. In ad-dition, anastomoses arise between the ante-rior and posterior spinal arteries, so that the spinal cord is surrounded by a vascular ring (vasocorona) (D8) from where vessels radiate into the white matter. Injection of tracers revealed that the gray matter is much more vascularized than the white matter (D).
Areas of blood supply (E).The anterior spi-nal artery supplies the anterior horns, the bases of the posterior horns, and the largest part of the anterior lateral funiculi (E9). The posterior funiculi and the remaining parts of the posterior horns are supplied by the posterior spinal arteries (E10). The marginalzone of the anterior lateral funiculus is sup-plied by the plexus of the vasocorona (E11).
The spinal veins (B) form a network in which one anterior spinal vein and two pos-terior spinal veins stand out. The efferentveins run along the spinal roots and open into the epidural venous plexus (see vol. 2). The spinal veins lack valves prior to their penetration through the dura.