A 40-year-old woman presents with carpal tunnel syndrome. Which specific nerve compression causes thenar muscle wasting and loss of sensation over the thumb, index, middle finger, and radial half of the ring finger?

• A Median nerve ✓
• B Ulnar nerve
• C Superficial branch of radial nerve
• D Lateral cutaneous nerve of forearm

Explanation

The median nerve passes through the carpal tunnel (beneath the flexor retinaculum) and divides into the recurrent branch (motor, supplying LOAF muscles: lateral two lumbricals, opponens pollicis, abductor pollicis brevis, flexor pollicis brevis) and digital branches (sensory to thumb, index, middle, and radial half of ring finger). Carpal tunnel syndrome causes thenar wasting and the classic sensory distribution. The ulnar nerve enters the hand through Guyon's canal and supplies hypothenar muscles and ulnar 1.5 digits. Sensory loss does NOT include the thenar eminence in carpal tunnel (palmar cutaneous branch is proximal to carpal tunnel).

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.