Which nerve innervates the deltoid and teres minor and provides sensory coverage over the lateral shoulder?

• A. Median nerve
• B. Ulnar nerve
• C. Axillary nerve
• D. Radial nerve

Answer: (C)

The axillary nerve is being tested for its dual role in motor and sensory supply to this region. It comes from the posterior cord of the brachial plexus (C5–C6) and innervates the deltoid and teres minor. The deltoid enables most arm abduction after the first 15 degrees, while teres minor assists in external rotation. Sensory-wise, the axillary nerve provides sensation to the skin over the lateral shoulder via the superior lateral cutaneous nerve of the arm, the area often described as the regimental badge region. The other nerves don’t cover both muscles and that lateral-shoulder sensory area: the median and ulnar nerves mainly serve the forearm and hand, and the radial nerve supplies the posterior arm/forearm and part of the hand, not the lateral shoulder.