During examination, a patient is asked to grip a sheet of paper between the thumb and index finger. As the examiner pulls the paper away, the patient forcibly flexes the interphalangeal joint of the thumb to hold on. This sign localises a lesion to which nerve?

• A Anterior interosseous nerve
• B Posterior interosseous nerve
• C Recurrent branch of the median nerve
• D Ulnar nerve ✓

Explanation

This is Froment's sign. Paralysis of adductor pollicis (ulnar nerve) removes true thumb adduction, so the patient recruits flexor pollicis longus, supplied by the median nerve, producing visible flexion at the thumb interphalangeal joint. The anterior interosseous nerve is a distractor because it supplies flexor pollicis longus, but an AIN lesion would abolish this compensatory movement rather than reveal it.

Reference: Moore's Clinically Oriented Anatomy, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.