During thyroidectomy, a surgeon ligating the superior thyroid artery must identify and preserve a nerve running in close relation to the vessel. Damage to this nerve results in loss of tension of the vocal cords and a monotonous voice. The nerve in question supplies:

• A All intrinsic muscles of the larynx except the cricothyroid
• B Sensory mucosa above the vocal cords
• C Posterior cricoarytenoid muscle
• D Cricothyroid muscle only ✓

Explanation

The external branch of the superior laryngeal nerve runs with the superior thyroid artery and supplies the cricothyroid muscle, the tensor of the vocal cords. Injury causes inability to tense the cords, producing a weak, monotonous voice and easy fatigability. All other intrinsic laryngeal muscles are supplied by the recurrent laryngeal nerve, and internal laryngeal sensation above the cords travels in the internal branch, which is unrelated to the artery.

Reference: Bailey and Love's Short Practice of Surgery, 27th ed.

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Written and medically reviewed by the StethoPrep medical team.