A 22-year-old man receives a stab wound just inferior to the clavicle. He has marked weakness of elbow flexion and forearm supination, an absent biceps jerk reflex, and numbness along the lateral aspect of the forearm. The thumb and fingers are unaffected. Which nerve has been injured?

• A Median nerve
• B Musculocutaneous nerve ✓
• C Radial nerve
• D Lateral root of the median nerve

Explanation

The musculocutaneous nerve pierces coracobrachialis and supplies biceps brachii and brachialis before continuing as the lateral cutaneous nerve of forearm. A lesion therefore produces weak elbow flexion and supination, an absent biceps reflex, and anaesthesia over the lateral forearm. The best distractor, median nerve, is excluded because median lesions spare the biceps reflex and produce sensory loss on the palmar hand and fingers, not the lateral forearm.

Reference: Moore's Clinically Oriented Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.