A 24-year-old man sustains a deep laceration just below the left coracoid process. He has marked weakness of elbow flexion, an absent biceps tendon reflex, and numbness over the lateral aspect of the forearm down to the wrist. Shoulder abduction is normal and sensation over the thumb is intact. Which nerve is injured?
- A Median nerve
- B Axillary nerve
- C Musculocutaneous nerve ✓
- D Radial nerve
Correct answer: C. Musculocutaneous nerve
Explanation
The musculocutaneous nerve pierces coracobrachialis and supplies biceps, brachialis and coracobrachialis before continuing as the lateral cutaneous nerve of the forearm. Injury therefore produces weak elbow flexion, loss of the biceps jerk and sensory loss confined to the lateral forearm. The best distractor, the median nerve, carries sensation from the thumb and lateral palm but never supplies biceps or the skin of the forearm.
Reference: Snell's Clinical Anatomy by Regions, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.