A patient sustains a penetrating injury below the clavicle near the coracoid process. He has marked weakness of elbow flexion and supination, an absent biceps reflex on that side, and numbness along the lateral aspect of the forearm. The deltoid and triceps are normal. Which nerve is injured?

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

Explanation

The musculocutaneous nerve arises from the lateral cord, pierces coracobrachialis and supplies biceps brachii and brachialis before continuing as the lateral cutaneous nerve of the forearm. Paralysis of biceps and brachialis abolishes strong flexion and weakens supination, and sensory loss over the lateral forearm is characteristic. In an isolated lesion, triceps and deltoid are spared, excluding radial and axillary nerve injuries.

Reference: Snell's Clinical Neuroanatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.