If the AP diameter of the concave arrangement in the wrist is diminished, which nerve is impinged upon?

If the AP diameter of the concave arrangement in the wrist is diminished, which nerve is impinged upon?

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

Answer: (B)

The median nerve is the correct answer because it runs through the carpal tunnel along with the flexor tendons in the wrist. The carpal tunnel is formed by the carpal bones and a ligament that arches over the top, and it has limited space. If there is a reduction in the anteroposterior (AP) diameter of this tunnel—often due to conditions such as swelling, inflammation, or structural abnormalities—compression of the median nerve can occur.

This compression is commonly associated with conditions like carpal tunnel syndrome, where patients experience symptoms such as pain, numbness, or tingling in the thumb, index, middle, and part of the ring finger. Thus, a diminished AP diameter directly correlates with increased pressure on the median nerve, leading to its impingement.

In contrast, the ulnar nerve, while it does run through the wrist, primarily travels through a different anatomical corridor and is generally affected by other conditions such as compression at the elbow or in the ulnar tunnel in the wrist. The radial and musculocutaneous nerves are not typically impinged by changes in the wrist structure, as they do not pass through the carpal tunnel or have direct anatomical connections to the wrist.