A 35-year-old man develops inability to elevate the right arm above shoulder level and a drooping right shoulder contour two weeks after an excision biopsy of a right posterior triangle lymph node. Which nerve was injured?
- A Dorsal scapular nerve
- B Long thoracic nerve
- C Spinal part of the accessory nerve ✓
- D Suprascapular nerve
Correct answer: C. Spinal part of the accessory nerve
Explanation
The spinal accessory nerve crosses the posterior triangle of the neck lying superficially on the levator scapulae, embedded in lymphatic tissue, making it vulnerable during lymph node biopsy. Injury denervates the trapezius, producing shoulder droop, lateral scapular winging, and impaired abduction beyond 90 degrees because the trapezius assists serratus anterior in scapular rotation. The long thoracic nerve lies deeper on serratus anterior and causes medial scapular winging.
Reference: Gray's Anatomy for Students, 4th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.