Spinal Cord

Vascular supply

• The vertebral arteries and the aorta (via 10 medullary branches) provide the primary vascularization of the spinal cord by forming a single anterior spinal artery (ASA) and two posterior spinal arteries (PSA).
  • The largest medullary branch, the great anterior artery of Adamkiewicz, arises between T9 and L2 and supplies the lumbar enlargement.
  • The ASA supplies the anterior two-thirds of the spinal cord, and the two PSAs together supply the posterior one-third.
• The upper thoracic (T1-T4) segments are in the zone between ascending and descending blood supply are thus act as a watershed vulnerable to ischemic insult by hypoperfusion/hypotension.

Nerve root anatomy

• Cervical nerve roots exit above the corresponding vertebrae and the C8 root exists above the T1 vertebrae.
• Thoracic, lumbar, and sacral nerve roots exit below their corresponding vertebral body, laterally and superiorly through the neural foramina.
  • Therefore, a herniation at the L4-L5 disc interspace will compress the L4 nerve root as it exits.
• Autonomic dysfunction can be an additional complication of spinal lesions above T6, and this is one of the leading causes of mortality in this population.
  • It presents with respiratory distress, impaired thermoregulation, lower urinary tract and GI complications, and cardiovascular dysfunction such as autonomic dysreflexia.
    • Autonomic dysreflexia is sudden episodic increases in blood pressure along with baroreceptor-mediated bradycardia in response to noxious visceral or cutaneous stimulation below the injury level.