Following a displaced fracture of the surgical neck of the humerus, a patient cannot abduct the shoulder and reports numbness over the lower lateral part of the deltoid region. Which cutaneous nerve carries this sensory deficit?

• A Upper lateral cutaneous nerve of the arm
• B Inferior lateral cutaneous nerve of the arm
• C Superior lateral cutaneous nerve of the arm ✓
• D Intercostobrachial nerve

Explanation

The axillary nerve winds around the surgical neck in the quadrangular space with the posterior circumflex humeral artery. Its terminal cutaneous branch, the superior lateral cutaneous nerve of the arm, supplies skin over the lower lateral deltoid, giving the classic regimental badge area of anaesthesia. The inferior lateral cutaneous nerve of the arm comes from the radial nerve, and the intercostobrachial nerve (T2) supplies the medial upper arm, so neither fits this distribution.

Reference: Gray's Anatomy for Students, 4th ed.

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