Loss of pronation of the hand suggests a lesion of which nerve?

The loss of pronation of the hand is primarily associated with a lesion of the median nerve. The median nerve innervates several muscles involved in forearm pronation, most notably the pronator teres and pronator quadratus. These muscles work together to rotate the forearm, turning the palm downward (pronation).

When the median nerve is compromised, these muscles can become weakened or paralyzed, resulting in an inability to perform pronation effectively. Symptoms might include difficulty with tasks that require this motion, such as turning a doorknob or using utensils.

In contrast, the other nerves mentioned do not primarily control the pronation movement. The radial nerve is mainly responsible for wrist and finger extension, the ulnar nerve primarily affects hand grip and fine motor control in the fingers, and the musculocutaneous nerve innervates muscles that flex the elbow and do not play a significant role in forearm pronation. Hence, a lesion in the median nerve is a clear cause of loss of pronation of the hand.