A 35-year-old woman develops winging of the scapula after a radical mastectomy. Which nerve is injured and what is the motor deficit?

• A Suprascapular nerve; inability to initiate abduction
• B Long thoracic nerve; paralysis of serratus anterior ✓
• C Thoracodorsal nerve; weakness of latissimus dorsi
• D Spinal accessory nerve; weakness of trapezius

Explanation

The long thoracic nerve (C5, C6, C7) — the nerve of Bell — supplies serratus anterior, which holds the scapula against the thoracic wall. Injury to this nerve during axillary dissection (as in mastectomy) causes paralysis of serratus anterior, resulting in medial winging of the scapula (scapula wings medially and rotates downward). Winging is most prominent when the patient pushes against a wall with outstretched arms. Spinal accessory nerve injury produces lateral (shoulder) winging through trapezius weakness.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.