Which spinal nerve is most commonly compressed by a herniated lumbar disc?

Which spinal nerve is most commonly compressed by a herniated lumbar disc?

• A. L5
• B. L4
• C. S1
• D. L3

Answer: (A)

Lumbar disc herniation most often impinges the nerve root that lies just below the level of the disc. At the L4-L5 level, this means the L5 nerve root is the one most commonly affected. The L5 root travels to the dorsum of the foot and supplies dorsiflexion of the great toe; thus, radicular pain radiating down the leg with weakness of dorsiflexion (foot or toe extension) and sensory changes on the dorsum of the foot are typical. The other roots would be more likely affected by herniations at their respective level (for example, S1 by L5-S1 disc), so L5 is the best choice.

Lumbar disc herniation most often impinges the nerve root that lies just below the level of the disc. At the L4-L5 level, this means the L5 nerve root is the one most commonly affected. The L5 root travels to the dorsum of the foot and supplies dorsiflexion of the great toe; thus, radicular pain radiating down the leg with weakness of dorsiflexion (foot or toe extension) and sensory changes on the dorsum of the foot are typical. The other roots would be more likely affected by herniations at their respective level (for example, S1 by L5-S1 disc), so L5 is the best choice.