A patient with AIN syndrome may exhibit what specific inability?

• A. Inability to abduct the thumb
• B. Inability to make an OK sign
• C. Inability to extend the wrist
• D. Inability to flex the fingers

Answer: (B)

The scenario describes Anterior Interosseous Nerve (AIN) syndrome, which primarily affects the motor function of the anterior interosseous nerve, a branch of the median nerve. This nerve innervates specific muscles in the forearm, particularly the flexor pollicis longus (which flexes the thumb), the flexor digitorum profundus to the index and middle fingers, and the pronator quadratus.

The specific inability associated with AIN syndrome is the inability to make an OK sign. This action requires the coordination of the flexor pollicis longus and the flexor digitorum profundus to create the "O" shape with the thumb and index finger. When there is weakness or paralysis in these muscles due to AIN dysfunction, the patient cannot form this position, resulting in a characteristic inability to make the OK sign.

The other options describe movements that are not primary functions of the muscles innervated by the AIN. While an inability to abduct the thumb may be related to issues with other nerves (such as the ulnar or radial nerves), and inability to extend the wrist primarily involves the radial nerve, issues with flexing the fingers can also involve other muscular or neurological factors outside of the A