A 30-year-old sustains an injury to the median nerve at the wrist (carpal tunnel level). Which muscle is NOT affected in a pure median nerve lesion at the wrist (as opposed to the elbow)?

• A Abductor pollicis brevis
• B Opponens pollicis
• C Flexor pollicis longus ✓
• D First and second lumbricals

Explanation

Flexor pollicis longus (FPL) is innervated by the anterior interosseous nerve (AIN), a branch of the median nerve that arises in the forearm before the carpal tunnel. Therefore, FPL is spared in a pure median nerve lesion at the wrist (distal to the origin of AIN). The thenar muscles (APB, opponens pollicis, flexor pollicis brevis superficial head) and first/second lumbricals are innervated by the recurrent motor branch and digital branches of the median nerve arising distal to or within the carpal tunnel and would be affected. FPL palsy suggests a more proximal (elbow/forearm) median nerve injury or AIN syndrome specifically.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.