A patient with advanced carpal tunnel syndrome has marked thenar wasting yet sensation over the central palm and thenar eminence remains completely normal. What explains this sparing?

• A The palmar digital branches arise proximal to the flexor retinaculum
• B Thenar eminence skin is innervated by the radial nerve in most individuals
• C The recurrent motor branch carries all sensory fibres from the thenar skin
• D The palmar cutaneous branch of the median nerve passes superficial to the flexor retinaculum ✓

Explanation

The palmar cutaneous branch of the median nerve leaves the main trunk proximal to the wrist, pierces the antebrachial fascia, and crosses the carpal tunnel superficial to the flexor retinaculum. It therefore escapes compression within the tunnel while the digital branches and recurrent motor branch are trapped inside. This anatomical fact also localises more proximal median nerve lesions, where thenar skin sensation IS affected alongside motor loss.

Reference: Moore's Clinically Oriented Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.