In a high median nerve lesion at the elbow (anterior interosseous nerve involvement), which specific grip is lost and which test assesses this?

• A Power grip (ulnar intrinsics) is lost; assessed by Froment's sign
• B Pinch grip between index and thumb is impaired (cannot make OK sign); flexor pollicis longus and FDP to index finger are paralyzed ✓
• C Precision grip for ring and little fingers is lost; Wartenberg's sign is positive
• D Thumb opposition (opponens pollicis) is lost; assessed by pen test

Explanation

The anterior interosseous nerve (AIN), a purely motor branch of the median nerve arising 5–8 cm below the medial epicondyle, innervates flexor pollicis longus (FPL), flexor digitorum profundus to index and middle fingers (FDP I/II), and pronator quadratus. AIN palsy produces inability to flex the distal phalanges of index finger and thumb — the patient cannot make an OK sign (pincer/pinch), instead hyperextending the distal phalanges ('AIN sign'). Froment's sign (adductor pollicis) and Wartenberg's sign are ulnar nerve tests. Opponens pollicis is a recurrent median nerve motor branch (at wrist level).

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.