What specific nerve involvement is indicated by numbness over the deltoid in an anterior shoulder dislocation?

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

Answer: (B)

Numbness over the deltoid region following an anterior shoulder dislocation is indicative of axillary nerve involvement. The axillary nerve innervates the deltoid and teres minor muscles and provides sensation to the skin overlying the deltoid muscle. When the shoulder is dislocated anteriorly, the axillary nerve can become stretched or injured, leading to sensory loss in its distribution area. This is particularly relevant because the deltoid muscle plays a crucial role in shoulder abduction and overall shoulder mechanics.

The musculocutaneous nerve primarily affects sensation in the lateral forearm and is involved in flexing the elbow. The radial nerve is responsible for extending the elbow and providing sensation to the posterior arm and forearm but does not typically cause numbness in the deltoid region. The median nerve, known for its role in hand function and sensation, also does not contribute to sensation over the shoulder area. Thus, the symptom of numbness localized to the deltoid region strongly points towards the involvement of the axillary nerve.