ADD-ONS / ANATOMY

Blood Supply of the Spinal Cord

Created 04/03/2022, last revision 13/04/2022

The arterial system

Spinal arteries

  • spinal arteries originate primarily from the vertebral arteries and run longitudinally from the medulla of the brain stem to the medullary cone
    • VAs are the primary source of blood to the upper spinal cord
  • anterior spinal artery (ASA) runs along the anterior median fissure and gives off many branches to the median fissure (sulco-commissural and circumferential branches)   Anterior spinal artery on CTA  Anterior spinal artery on DSA
    • common trunk arising from both VAs with a predominance of one ramus over the other or with a sole unilateral ramus
    • ASA supplies the anterior 2/3 of the spinal cord
    • ASA may not be continuous (typically in the middle thoracic segment)
    • ASA communicates sporadically with the posterior spinal arteries via a pial plexus (vasocorona); at most levels and it gives off a sulcal artery that enters the anterior median fissure.
    • ischemic injury to this vessel results in dysfunction of the corticospinal, lateral spinothalamic, and autonomic intermedial pathways
  • pair of posterior spinal arteries run (one on each side of the midline) along the posterolateral sulcus and supply the posterior spinal cord horns and posterior column
    • they have numerous anastomoses and form a plexiform system (vasocorona)
  • overlap and redundancy occur between the terminal supply branches of these two systems within the parenchyma of the spinal cord itself
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Segmental medullary arteries

  • from the multiple fetal segmental arteries (fetal), only 6-14 large arteries persist in the adult age
    • they originate from the spinal branches of the ascending cervical, deep cervical, posterior intercostal, and lumbosacral arteries (from the aortic arch, thoracic and abdominal aorta)
    • they penetrate the spinal canal through the intervertebral foramina and accompany the roots
    • they are often unpaired, feeding the spinal arteries at different levels
  • segmental arteries reinforce the anterior and posterior spinal arteries providing additional vascularization of the spinal cord in lower segments (blood from the vertebral arteries can supply only the superior portion of the spinal cord, the circulation of the rest of the spinal cord depends on segmental arteries )
    • segmental medullary arteries
      • the larger vessels that, after supplying  dorsal or ventral root, anastomose with the spinal arteries   (Greathouse, 2001)
    • dorsal and ventral radicular arteries
      • most radicular arteries are small and supply only the nerve roots; they rarely reach the anterior or posterior spinal arteries (Greathouse, 2001)
  • in the cervical region, the segmental medullary arteries are usually distributed bilaterally; in the thoracic and lumbar regions, they are mainly left-sided
    • C1-Th3 segment – from VA (C1-C6), ascending cervical artery (C3-4), and deep cervical artery (C3–C7)

      • in the cervical region, the radiculomedullary artery from C4–C7 is usually the most predominant and is called the artery of cervical enlargement   (Zhang, 2021)
    • Th segment –  from posterior intercostal arteries
      • a major segmental feeder may occur in the upper thoracic spine, often at the T5 level – this has been termed the artery of von Haller
    • Th8-conus – artery of Adamkiewicz and branch from iliolumbar arteries
      • artery of Adamkiewicz is the largest of the segmental arteries (level T9-Th12 in 62%)
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  • damage to one segmental artery in a critical area (e.g., during aortic dissection) or damage to multiple segmental arteries (e.g., after aortic surgery) can lead to the spinal cord infarction
  • segmental arteries supply the vertebral bodies, meninges, and spinal cord (therefore, in spinal cord infarction, infarction can often be observed in the vertebral body as well)
  • the anterior spinal artery (ASA) region is more vulnerable to ischemia than the posterior third because it does not have as many anastomoses. On the surface of the spinal cord, the junctions of the segmental arteries with the posterior and anterior spinal arteries form a closed circulatory system (called arterial vasocorona)
  • the vulnerable areas include, in particular, the upper thoracic segments (Th1-4) and the lumbar intumescence area (especially the first lumbar segment)
    • this area is supplied by the most constant and largest segmental artery, the Adamkiewicz artery (also known as the lumbar intumescence artery)
    • Adamkiewicz artery usually enters the spinal canal in the segment Th9-L1, usually on the left side
Spinal cord infarction caused by the dissection in V4 segment of VA

The venous system

  • small intramedullary veins drain into the longitudinal tortuous venous plexus, which is formed along the entire length of the spinal cord
    • ventral sulcal veins drain the medial portion of the anterior horn, the anterior commissure, and the white matter of the anterior funiculus
    • the dorsal central veins drain the gray commissure and the white matter near the posterior median sulcus
    • the remaining areas of the cord are also drained centrifugally by peripheral radial veins    Radial veins
    • anastomotic veins connect the radial and sulcal veins
  • this plexus is formed by:
    • anterior spinal vein (collects blood from sulcal and radial veins) – usually  paired in the cervical and thoracic regions, a single vessel in the lumbar area
    • posterior spinal vein and 2 lateral longitudinal veins which run behind the nerve roots
    • venous vasocorona (connecting longitudinal trunks)
  • from both anterior and posterior veins, blood is drained via several ventral and dorsal radiculomedullary veins to the internal vertebral venous plexus (Batson plexus)
    • radiculomedullary veins exit the dura, usually with the nerve root
    • the largest radiculomedullary vein, called the great anterior radiculomedullary vein (GARV), drains the thoracolumbar cord and can be mistaken for the artery of Adamkiewicz
  • the internal vertebral plexus comprises two anterior longitudinal veins coursing on either side of the posterior longitudinal ligament and two posterior veins coursing anterior to the ligamentum flavum
  • via the intervertebral foramina, the internal vertebral plexus is connected to the external vertebral plexus (via the intervertebral veins)
    • veins around the spine are not equipped with valves, and blood can flow in different directions depending on the pressure gradient
  • the external vertebral plexus drains into the vertebral veins of the neck and the segmental veins of the trunk
    • cervical cord → vertebral, deep cervical, and jugular veins
    • thoracic cord → hemiazygos and accessory hemiazygos veins on the left, and the azygos vein on the right
    • lumbar cord → azygos and ascending lumbar veins
Spinal cord veins
Intra-spinal veins
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