A 45-year-old woman with carpal tunnel syndrome has numbness of the lateral three and a half digits, yet sensation over the central palm and thenar eminence is completely intact. What explains this sparing?

• A The lateral antebrachial cutaneous nerve takes over the palm supply
• B The thenar eminence is innervated by the recurrent motor branch, which carries sensory fibres
• C The digital branches regenerate faster than the trunk of the nerve
• D The palmar cutaneous branch of the median nerve arises proximal to the flexor retinaculum and lies superficial to it ✓

Explanation

The palmar cutaneous branch leaves the median nerve about 5 cm proximal to the wrist and crosses the retinaculum superficially, so compression inside the carpal tunnel spares the central palm and thenar skin. The recurrent branch is purely motor, which removes option B, and the lateral antebrachial nerve supplies the forearm, not the palm.

Reference: Gray's Anatomy for Students, 4th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.