Which nerve is associated with carpal tunnel syndrome?

• A. Median nerve of the wrist
• B. Radius
• C. Ulnar nerve of the wrist
• D. Head of the ulna

Answer: (A)

Carpal tunnel syndrome occurs when the median nerve is compressed as it travels through the carpal tunnel at the wrist, under the flexor retinaculum. The tunnel is formed by the carpal bones and the transverse carpal ligament, and the median nerve carries sensation from the thumb, index, middle, and half of the ring finger plus motor control to most of the thenar muscles. This explains the classic symptoms of numbness, tingling, and sometimes weakness in those fingers and in the hand, especially at night. The other options are not involved in the carpal tunnel: the radius and head of the ulna are forearm bones, and the ulnar nerve at the wrist goes through Guyon’s canal, not the carpal tunnel, leading to different patterns of sensation and weakness.