Which sign is used to assess median nerve function?

Which sign is used to assess median nerve function?

• A. Abduction of the thumb
• B. Hyperextension of the wrist
• C. Oppose thumb to little finger
• D. OK sign with thumb and index finger

Answer: (D)

The sign you’re using to assess median nerve function is the OK sign formed with the thumb and index finger. This test specifically probes the function of two muscles: flexor pollicis longus (thumb) and flexor digitorum profundus to the index finger (index). Both are controlled by the median nerve via its anterior interosseous branch. When the median nerve (and particularly the anterior interosseous nerve) is impaired, these muscles can’t flex those finger joints adequately, so the tip-to-tip pinch cannot be formed. Instead, the person may pinch with pads or have a weak or altered pinch, indicating median nerve dysfunction. The other options test related actions but aren’t as specific to this distal median-nerve pathway: abduction of the thumb involves multiple muscles (some radial nerve, some median nerve), hyperextension of the wrist is radial nerve territory, and opposing the thumb to the little finger tests the thenar muscles (median nerve) but is not as targeted for the distal FPL and index flexors as the OK sign.

The sign you’re using to assess median nerve function is the OK sign formed with the thumb and index finger. This test specifically probes the function of two muscles: flexor pollicis longus (thumb) and flexor digitorum profundus to the index finger (index). Both are controlled by the median nerve via its anterior interosseous branch. When the median nerve (and particularly the anterior interosseous nerve) is impaired, these muscles can’t flex those finger joints adequately, so the tip-to-tip pinch cannot be formed. Instead, the person may pinch with pads or have a weak or altered pinch, indicating median nerve dysfunction.

The other options test related actions but aren’t as specific to this distal median-nerve pathway: abduction of the thumb involves multiple muscles (some radial nerve, some median nerve), hyperextension of the wrist is radial nerve territory, and opposing the thumb to the little finger tests the thenar muscles (median nerve) but is not as targeted for the distal FPL and index flexors as the OK sign.