The arterial supply to the lower two-thirds of the spinal cord comes primarily from which artery?

• A. Anterior spinal artery
• B. Posterior spinal artery
• C. Intercostal artery
• D. Arteria radicularis magna

Answer: (D)

The main idea is how the spinal cord is fed from both longitudinal arteries and their reinforcing segmental feeders. The anterior spinal artery runs along the front of the cord and supplies the anterior two-thirds, while the posterior spinal arteries supply the posterior one-third. To reach the lower cord, the circulation relies heavily on segmental radicular arteries that reinforce the anterior spinal artery. Among these, the artery of Adamkiewicz (arteria radicularis magna) is the largest and serves as the major feeder to the lower thoracic and lumbar segments. It typically enters from a left posterior intercostal artery around T9 to L2 and then significantly boosts perfusion to the lower two-thirds of the spinal cord via the anterior spinal artery.

So, the artery of Adamkiewicz is the best answer because it is the principal supplier to the distal cord, ensuring the lower two-thirds receive adequate blood flow. The anterior spinal artery provides the front two-thirds in general, but the prominent distal support comes from this great radicular artery; the posterior spinal arteries govern the back one-third, and intercostal arteries are sources for these segmental feeders rather than direct, primary supply to the lower cord.