A herniated nucleus pulposus at the L3-L4 disc typically causes numbness and weakness in which distribution?

A herniated nucleus pulposus at the L3-L4 disc typically causes numbness and weakness in which distribution?

• A. Numbness in the back of the calf and dorsiflexor weakness
• B. Numbness in the anteromedial thigh and knee and quadriceps weakness
• C. Numbness and weakness in the thigh, legs, feet and/or perineum
• D. Numbness in the back of the calf and atrophy of gastrocnemius and soleus

Answer: (B)

Discs in the lumbar spine affect the nerve root that runs at that level. An herniation between L3 and L4 most commonly impinges the traversing L4 nerve root. The L4 root provides sensation to the anteromedial thigh and knee area and mainly controls knee extension via the quadriceps. So numbness described on the anteromedial thigh/knee together with weakness of the quadriceps fits an L4 radiculopathy from an L3-L4 disc herniation. The other patterns point to different roots: posterior calf numbness with calf atrophy suggests S1 (plantarflexion issues), and widespread thigh/leg/foot/perineal symptoms imply multi-root involvement or cauda equina.

Discs in the lumbar spine affect the nerve root that runs at that level. An herniation between L3 and L4 most commonly impinges the traversing L4 nerve root. The L4 root provides sensation to the anteromedial thigh and knee area and mainly controls knee extension via the quadriceps. So numbness described on the anteromedial thigh/knee together with weakness of the quadriceps fits an L4 radiculopathy from an L3-L4 disc herniation. The other patterns point to different roots: posterior calf numbness with calf atrophy suggests S1 (plantarflexion issues), and widespread thigh/leg/foot/perineal symptoms imply multi-root involvement or cauda equina.