A 35-year-old with L4–L5 disc prolapse presents with weakness of ankle dorsiflexion, big toe extension, and decreased sensation over the dorsum of the foot. The nerve root compressed is:
- A L3
- B L4
- C S1
- D L5 ✓
Explanation
L5 root: supplies the extensor hallucis longus (big toe dorsiflexion — the most reliable L5 muscle), tibialis anterior (ankle dorsiflexion), and peroneal muscles; sensory over the dorsum of the foot and first web space. L4 root: supplies tibialis anterior primarily; sensory over medial aspect of leg and ankle with diminished knee jerk. S1: weakness of plantar flexion and eversion; sensory over sole/lateral foot; diminished ankle jerk. The L4–L5 disc compresses the L5 root (which exits below L5 pedicle, where it is vulnerable to L4–L5 posterolateral disc herniation). Foot drop is the hallmark of L5 root compression.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.