Nerve compressed in carpal tunnel syndrome?

• A. Ulnar nerve
• B. Radial nerve
• C. Median nerve
• D. Axillary nerve

Answer: (C)

Compression of the median nerve as it passes through the carpal tunnel beneath the flexor retinaculum is what causes carpal tunnel syndrome. Inside the tunnel are the flexor tendons of the forearm and the median nerve; pressure here impairs sensation in the lateral three and a half digits and weakens the thenar muscles, leading to trouble with thumb opposition and possible thenar eminence wasting if advanced. The ulnar nerve doesn't run through the carpal tunnel (it travels in Guyon's canal and supplies the medial one and a half digits and most intrinsic hand muscles), the radial nerve is in the forearm and wrist but not in the carpal tunnel, and the axillary nerve supplies the shoulder region, not the wrist.