A clawhand appearance is primarily caused by damage to which nerve?

The clawhand appearance is primarily associated with damage to the ulnar nerve. This condition occurs due to weakness or paralysis of the intrinsic muscles of the hand, particularly those responsible for controlling the fingers. The ulnar nerve innervates specific muscles that facilitate the movement and positioning of the fingers, including the interossei and the hypothenar muscles. When the ulnar nerve is injured, the person may experience an inability to properly extend the distal phalanges of the fourth and fifth fingers, resulting in them curling into a claw-like position.

The other nerves mentioned do not typically lead to a clawhand appearance. For instance, damage to the median nerve is more commonly associated with conditions like carpal tunnel syndrome and can lead to different hand deformities, such as ape hand, where there is difficulty in opposition of the thumb. Radial nerve injury primarily results in wrist drop, affecting wrist extension. Musculocutaneous nerve injury tends to affect the biceps and forearm flexion, not the intrinsic muscles of the hand. Therefore, it is the impairment of the ulnar nerve that most directly leads to the characteristic clawhand presentation.