Three weeks after modified radical mastectomy with complete axillary clearance, a patient complains of persistent numbness over the medial aspect of her right upper arm and axilla. Which nerve was most likely injured?
- A Intercostobrachial nerve ✓
- B Thoracodorsal nerve
- C Medial pectoral nerve
- D Long thoracic nerve
Correct answer: A. Intercostobrachial nerve
Explanation
The intercostobrachial nerve is the lateral cutaneous branch of the second intercostal nerve and crosses the axilla to supply sensation over the medial upper arm and axillary floor. It traverses the operative field during axillary dissection, and division produces the characteristic numbness described. Injury to the thoracodorsal nerve weakens latissimus dorsi adduction, the long thoracic nerve causes serratus anterior weakness with winging of the scapula, and pectoral nerve injury affects pectoralis function, none of which alter cutaneous sensation in this distribution.
Reference: Gray's Anatomy for Students, 4th ed.
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Written and medically reviewed by the StethoPrep medical team.