A young man receives a stab wound to the anterior compartment of the right arm. On examination, elbow flexion is markedly weak, the biceps tendon reflex is absent, and there is numbness along the lateral aspect of the forearm. Which nerve has been injured?

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

Explanation

The musculocutaneous nerve pierces coracobrachialis and supplies biceps brachii, brachialis and coracobrachialis before continuing as the lateral cutaneous nerve of the forearm. Injury therefore causes weak elbow flexion and supination, an absent biceps jerk, and sensory loss over the lateral forearm. The radial nerve kills this distractor because it supplies brachioradialis and the extensor compartment, so its loss produces wrist drop and lateral forearm sensation would be preserved.

Reference: Snell's Clinical Anatomy by Regions, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.