After excision of a posterior triangle lymph node biopsy, a patient has drooping of the shoulder, inability to shrug against resistance, and lateral displacement of the scapula on forward elevation of the arm. Which nerve was injured?

• A Spinal accessory nerve ✓
• B Dorsal scapular nerve
• C Greater auricular nerve
• D Suprascapular nerve

Explanation

Lymph node biopsy in the posterior triangle is the classic cause of iatrogenic spinal accessory nerve injury. Paralysis of trapezius produces shoulder drop, loss of shrugging power, and a characteristic lateral or outward winging of the scapula on arm elevation, distinct from the medial winging of serratus anterior palsy. The dorsal scapular nerve supplies rhomboids and would cause medial scapular displacement without affecting shrugging.

Reference: Gray's Anatomy, 42nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.