During axillary lymph node dissection for breast cancer, the surgeon identifies and preserves a nerve that runs along the chest wall to innervate the serratus anterior muscle. Injury to this nerve results in:

• A Horner's syndrome
• B Numbness over the medial arm
• C Weakness of shoulder abduction
• D Winging of the scapula ✓

Explanation

The long thoracic nerve innervates the serratus anterior muscle. Its injury during axillary dissection causes medial winging of the scapula, especially noticeable when the patient pushes against a wall. Intercostobrachial nerve injury causes medial arm numbness. Axillary nerve injury affects shoulder abduction. Sympathetic chain injury causes Horner's syndrome.

Reference: Gray's Anatomy, 42nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.