Head and Neck Anatomical Structures · USMLE Step 1

A patient is unable to shrug the shoulder after neck surgery. Which muscle has lost its innervation?

  1. Levator scapulae
  2. Trapezius
  3. Sternocleidomastoid
  4. Rhomboid major
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Correct answer: Trapezius

The trapezius is innervated by the spinal accessory nerve (CN XI). Its injury causes shoulder droop and impaired shrugging.

Difficulty: Medium Question 5 of 20

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