For an L3/4 disc herniation, which nerve root is most likely to be affected?

• A. L3
• B. L4
• C. L5
• D. S1

Answer: (B)

In cases of an L3/4 disc herniation, the most likely affected nerve root is the L4 nerve root. This is because the anatomy of the lumbar spine dictates that herniation of the intervertebral disc at this level typically results in pressure on the descending nerve root of the exiting spinal nerve.

The L3/4 disc herniation predominantly affects the L4 nerve root as it exits just above the L4/5 foramen. The herniation can protrude posteriorly or posterolaterally, which can encroach upon the L4 nerve root and cause symptoms such as pain, numbness, or weakness along the L4 sensory and motor distribution. This distribution includes the anterolateral thigh and parts of the knee, as well as weakness in knee extension due to the involvement of the quadriceps muscle.

This understanding of nerve root mechanics and their anatomical relationship in the lumbar region is essential for accurately diagnosing and managing lumbar disc pathologies.