How many segmental arterial branches arise from the aorta to supply the spinal cord?

Segmental Arterial Supply to the Spinal Cord

The spinal cord receives blood supply from 31 pairs of segmental arteries that arise from the aorta, corresponding to 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal segments.

Anatomical Organization of Spinal Cord Blood Supply

The blood supply to the spinal cord follows a complex and variable pattern that is critical to understand for procedures involving the thoracic and thoracoabdominal aorta. The key components include:

Segmental Arteries

• Arise directly from the aorta at each vertebral level 1
• Include posterior intercostal arteries (thoracic region), subcostal arteries, and lumbar arteries 1
• Total of 31 pairs corresponding to spinal cord segments:
  • 8 cervical segments
  • 12 thoracic segments
  • 5 lumbar segments
  • 5 sacral segments
  • 1 coccygeal segment

Radiculomedullary Arteries

• Only a subset of segmental arteries contribute significant blood supply to the spinal cord via radiculomedullary branches 2
• These branches travel along the nerve roots to reach the spinal cord
• The most important radiculomedullary artery is the artery of Adamkiewicz (great anterior radiculomedullary artery), which typically arises between T9 and L3, most commonly from the left side 3

Longitudinal Arterial Systems

• The anterior spinal artery runs along the anterior median fissure
• Two posterior spinal arteries run along the posterolateral sulci
• These longitudinal vessels are fed by the radiculomedullary arteries and form an anastomotic network called the vasocorona 2

Clinical Significance

Understanding the segmental arterial supply to the spinal cord is crucial for:

1. Aortic Surgery Planning: Preoperative identification of critical segmental arteries (particularly the artery of Adamkiewicz) can help reduce the risk of spinal cord ischemia during thoracic and thoracoabdominal aortic procedures 3

2. Risk Assessment: Patients with compromised collateral circulation are at higher risk for spinal cord ischemia when segmental arteries are sacrificed 4

3. Anatomical Variations: The position of segmental artery origins varies relative to vertebral levels, with upper thoracic arteries originating up to two levels caudal to their corresponding vertebrae, while lower thoracic and lumbar arteries originate closer to their corresponding levels 1

Imaging Considerations

• MRI without contrast is the first-line imaging modality for evaluating spinal cord pathology 5
• CT angiography or MR angiography may be necessary when vascular pathology is suspected 5
• Selective spinal angiography can demonstrate spinal cord blood supply even in patients with complex aortic pathology 3

Protective Strategies During Aortic Procedures

When aortic procedures risk compromising segmental arterial supply:

• Preoperative spinal angiography to identify critical vessels 3
• Targeted reimplantation of crucial intercostal/lumbar branches 3
• Cerebrospinal fluid drainage to reduce spinal cord pressure and improve perfusion 4
• Maintenance of collateral circulation through subclavian, lumbar, and hypogastric arteries 4

The risk of spinal cord ischemia increases dramatically when multiple territories supplying the spinal cord are compromised, such as when there is occlusion of the subclavian, lumbar, or hypogastric arteries in addition to coverage of intercostal arteries 4.