Arterial blood supply to the spinal cord
Before the vertebral arteries unite to form the main artery, they branch out to the very top of the cervical spinal cord and give rise to one anterior and two posterior spinal arteries. The anterior and posterior spinal arteries are arteries that lie longitudinally along the spinal cord and give anastomoses. The anterior and posterior spinal arteries receive arterial blood at different levels and distribute it among the spinal cord's arteries.
The anterior spinal artery (arteria spinalis anterior) runs in the form of a single continuous vascular trunk along the anterior surface (in the median groove, fissure) of the spinal cord down to the terminal cone. It then makes a loop towards the back of the lumbar spinal cord and connects to the posterior spinal arteries (arteriae spinales posterior).
The posterior spinal arteries descend in the posterolateral grooves of the spinal cord near the exit of the posterior roots. The posterior spinal arteries are not continuous individual vessels, but anastomosed chains of small arteries in which arterial blood can circulate in opposite directions. Occasionally, the posterior inferior cerebellar arteries provide arterial blood through branches to the posterior spinal arteries.
In addition to inflows from the basin of the vertebral arteries, the anterior and posterior spinal arteries receive blood from:
- radicular arteries extending from one or both vertebral arteries in the neck
- thyrocostocervical trunk of the subclavian artery segmental intercostal and lumbar arteries (below the level of the Th3 vertebral body)
Since the birth of a person, each segment of the spinal cord has its pair of radicular arteries supplying it. Later, only 5-8 radicular arteries remain, going along with the anterior roots to the anterior spinal artery, and 4-8 arteries, going together with the posterior roots to the posterior spinal arteries, at unequal intervals. The anterior radicular arteries are larger than the posterior ones. The largest among the radicular arteries is called the large radicular artery or Adamkevich's artery (arteria radicularis magna). The large radicular artery (Adamkevich's artery) usually accompanies the right or left L2 nerve root on its way to the anterior spinal artery. Segmental spinal arteries that atrophy after a period of initial human development do not completely disappear. They supply blood to the nerve roots, spinal nodes, and the dura mater.
1. - vertebral artery, 2. - anterior radicular artery C4-C5, 3. - anterior radicular artery C6-C8, 4. - costo-cervical trunk, 5. - shield-neck trunk, 6. - common carotid artery, 7. - brachiocephalic trunk, 8. - aorta, 9. - anterior vertebral artery, 10. - posterior intercostal artery Th4-Th6, 11. - large radicular artery (Adamkiewicz), 12. - posterior intercostal artery the Th9-L1 artery.
The anterior spinal artery gives off at small intervals sulcocomissurales and circumflexae branches. Approximately 200 sulcocommissural branches pass horizontally through the anterior median fissure (fissura mediana anterior) of the spinal cord, fan out in front of the anterior commissure (commissura alba) on both sides, and supply almost all of the gray matter and the surrounding rim of white matter, including some of the anterior pillars. The enveloping branches give anastomoses with the same branches from the posterior spinal arteries, forming a vascular crown (vasocorona). Its anterior branches supply the anterolateral and lateral cords of the spinal cord, including most of the lateral pyramidal tracts. The main nerve structures supplied by the posterior spinal arteries are the posterior cords and the apex of the posterior horns of the spinal cord.
Spinal cord venous drainage
The capillaries of the spinal cord, which in the gray matter form groups corresponding to the columns of neurons, donate blood to the veins of the spinal cord. Most of these veins run radially towards the periphery of the spinal cord. The veins located closer to the center of the spinal cord first spread along and run parallel to the central canal, before leaving the spinal cord deep in its anterior or posterior median sulcus. On the surface of the spinal cord, the veins form plexuses that deliver blood to the looping longitudinal collector veins, the anterior and posterior spinal veins. The posterior cerebrospinal collector vein is larger and increases in size towards the lower part of the spinal cord. From the spinal collector veins, blood flows through the central and posterior radicular veins (there can be from 5 to 11 on each side of the spinal cord) into the internal vertebral venous plexus (plexus venosus vertebralis internus).
1. - arachnoid, 2. - dura mater, 3. - posterior external vertebral venous plexus, 4. - posterior spinal vein, 5. - posterior central vein, 6. - posterolateral spinal veins, 7. - sulcocommissural vein, 8. - sulcus vein, 9. - periosteum , 10. - anterior and posterior radicular veins, 11. - anterior internal spinal venous plexus, 12. - intervertebral vein, 13. - vertebral veins, 14. - anterior external spinal venous plexus, 15. - basal-vertebral vein, 16. - anterior spinal vein.
The internal vertebral venous plexus, surrounded by loose connective and adipose tissue, is located in the subdural space and is analogous to the venous sinuses of the dura mater of the brain. This venous plexus communicates through the foramen magnum with these sinuses at the base of the skull. The outflow of venous blood also occurs through the intervertebral veins through the intervertebral foramen. Through the intervertebral veins, blood enters the external venous vertebral plexus (plexus venosus vertebralis externus). This plexus, among others, supplies venous blood to the azygos vein, which connects the superior and inferior vena cava to the right of the spine.
Syndromes caused by spinal vessels lesions
The anterior and posterior spinal arteries are usually not susceptible to atherosclerosis. The anterior and posterior spinal arteries can be affected by arteritis or embolism. Most often, spinal cord infarction in patients occurs as a result of ischemia with existing blockages (occlusions) of distant arteries. Aortic thrombosis or dissection causes spinal infarction by blocking (occluding) the radicular arteries and stopping direct arterial blood flow to the anterior and posterior spinal arteries. A heart attack usually develops in the area of adjacent blood supply to the thoracic spinal cord between the large spinal branch of the aorta, the Adamkevich artery from below, and the anterior spinal artery from above.
Causes of ischemia and spinal cord stroke:
- stenosis of the orifice of the segmental artery
- compression of the segmental artery or its branches by an anterior, lateral, or posterior herniated disc
- diaphragm pedicle syndrome
Spinal cord infarctioncan occur with systemic arteritis, immune reactions with serum sickness, and after intravascular administration of a contrast agent. With intravascular contrast, a harbinger of spinal cord infarction is severe back pain that occurs in the patient during the administration of contrast.
Spinal cord infarction, caused by microscopic fragments of a herniated intervertebral disc, the contents of which is the nucleus pulposus, can develop in a patient after a minor injury, often received during sports. At the same time, patients note acute local pain, alternating with rapidly onset paraplegia and the syndrome of transverse spinal cord injury, which develops within a few minutes to an hour. In small intramedullary vessels and often inside the bone marrow of the adjacent vertebral body, the pulp tissue is found. The path of its penetration from the disc material into the bone marrow and from there into the spinal cord remains unclear. This condition should be suspected in young people with transverse spinal cord injury syndromes as a result of an accident.
Blockage (occlusion) of the anterior spinal artery
Clinical manifestations of lesions of the anterior spinal artery usually appear in a patient suddenly, in the form of apoplexy. In some patients, the symptoms of blockage (occlusion) of the anterior spinal artery increase within 1-3 days, which makes it difficult to make an accurate diagnosis. A sudden, usually due to a blood clot, blockage (occlusion) of the cervical part of the anterior spinal artery causes a sensitivity disorder in the form of paresthesia and severe pain in the patient. Following the disorder of sensitivity, the patient develops flaccid paralysis of the muscles of the arms (peripheral type) and spastic paraparesis of the leg muscles (central type) due to the involvement of the pyramidal tracts of the spinal cord.
Also, there is a violation of the function of the bladder and rectum (function of the pelvic organs) and a decrease in pain and temperature sensitivity at the segmental level of blockage of the anterior spinal artery. In this case, the patient usually retains proprioceptive and tactile sensitivity. Lack of perspiration (anhidrosis) on the paralyzed part of the body can lead to an increase in body temperature, especially at high ambient temperatures, which simulates the patient's picture of infection.
Blockage (occlusion) of the posterior spinal artery
Blockage (occlusion) of one or both posterior spinal arteries in patients in clinical practice is extremely rare. The resulting focus of spinal cord infarction involves the posterior tracts and horns of the spinal cord, as well as partially the lateral pyramidal tracts. Below the level of spinal cord infarction, the patient has sensitivity disorders of the type of anesthesia and analgesia, spastic muscle paresis, and reflex disorders.