A lumbar disc herniation at the L4-L5 level typically compresses which nerve root, producing weakness of which movement?

• A L5 root; weakness of great toe and foot dorsiflexion ✓
• B L4 root; weakness of knee extension
• C S1 root; weakness of ankle plantarflexion
• D L3 root; loss of knee jerk

Explanation

At the L4-L5 disc level, the posterolateral herniation compresses the L5 nerve root, which exits below L5 vertebra. L5 root supplies tibialis anterior (foot dorsiflexion and inversion), extensor hallucis longus (great toe extension), and extensor digitorum. L4-L5 disc herniation characteristically produces L5 root symptoms: foot drop, weakness of great toe extension, and sensory loss over the dorsum of the foot and medial leg. S1 compression results from L5-S1 disc herniation.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.