Vascular Supply to the Spinal Cord

EXTRASPINAL SYSTEM (EXTRAMEDULLARY ARTERIES)

The anterior spinal artery arises from the anastomosis of two branches from the intracranial vertebral arteries. It travels in the anterior sulcus of the spinal cord and extends from the level of the olivary nucleus to the conus medullaris. It supplies the ventral surface of the medulla and the anterior two thirds of the spinal cord. The artery is continuous in the upper cervical region. However, in the segments inferior to the upper cervical region, it consists of anatomosing branches from the anterior radicular arteries.

The two posterior spinal arteries most commonly arise from the vertebral arteries. However, in some instances, they arise from PICA. There are contributions from numerous

Figure 22-6 Lateral vertebral. 1, V-3 segment of the vertebral artery. 2, V-4 segment of the vertebral artery. 3, Posterior meningeal artery. 4, Posterior inferior cerebellar artery. 5, Basilar artery. 6, Anterior inferior cerebellar artery. 7, Superior cerebellar artery. 8, Posterior cerebral artery (Courtesy of Karen S. Caldemeyer, M.D.)

posterior radicular arteries that form an anastomotic network on the posterior surface of the spinal cord. y These arteries supply the posterior one third of the spinal cord. The anterior and posterior spinal arteries join in an anastomotic loop at the conus medullaris. y

The different regions of the spinal cord receive an unevenly distributed blood supply. The upper cervicothoracic region between C1 and T2 is richly vascularized by the anterior spinal artery in the most superior segments, and radicular arteries in the lower cervical and upper thoracic segments. The artery of the cervical enlargement is the most important of these radicular arteries. There are a number of radiculomedullary arteries that feed the posterior spinal arteries. The intermediate or midthoracic portion of the cord between T3 and T8 is poorly vascularized by intercostal arteries. There is a single radiculomedullary artery between T6 and T8. There are a limited number of segmental feeders to the posterior spinal arteries. In the lower or thoracolumbosacral region, there is again a rich vascular supply through the radiculomedullary branches of the intercostal and lumbar arteries. One important artery is the great anterior radicular artery of Adamkiewicz (artery of the lumbar enlargement). There are numerous posterior radicular arteries at this level. An understanding of these variations is important in spinal cord vascular syndromes, particularly with hypoperfusion of the spinal cord due to hypotension.

INTRASPINAL SYSTEM (INTRAMEDULLARY ARTERIES)

Branches of the anterior and posterior spinal arteries form a vascular plexus or peripheral vasocorona that encircles the cord. There are also sulcal arteries arising from the anterior spinal system that travel in the anterior median fissure of the cord and then branch and penetrate the cord. There are fewer sulcal arteries in the midthoracic region, which may contribute to the susceptibility of this region to ischemia. The branches of this plexus supply a major portion of the white matter and the dorsal horns of the gray matter. The arterial supply of the gray matter is richer than that of the white matter. The gray matter, except the dorsal horns, is supplied by the largest branches of the anterior spinal artery called the sulcocommissural arteries. The dorsal horns and the funiculi are supplied by paired posterior spinal arteries, posterior medullary feeders, and perforating pial branches.

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