A 40-year-old man who returns home late from a party falls asleep in a chair and awakens with weakness and numbness in his right hand. Examination reveals moderate weakness of the brachioradialis muscle and an inability to extend the wrist and fingers. Deltoid, biceps, and triceps strength are normal. There is sensory loss to pinprick over the dorsal right hand. The lesion is in which of the following nerves?

A. right median nerve at the antecubital fossa

B. right median nerve at the carpal tunnel

C. right radial nerve at the axilla

D. right radial nerve at the humerus

E. right ulnar nerve at the elbow

D. right radial nerve at the humerus

Explanation:

This man's symptoms indicate that he injured the muscles provided by the radial nerve. The radial nerve is the most important terminal branch of the brachial plexus, being responsible for the sensory innervation of the hand and motor of the arm and forearm.

A traumatic injury to the radial nerve is often caused by humeral fractures, as the nerve and bone are in close anatomical contact. Since, the 40-year-old man had weakness and numbness in his right hand, his examination revealed moderate weakness of the brachioradialis muscle and an inability to extend the wrist and fingers. We can conclude that the man has a right radial nerve injury in the humerus.