During total thyroidectomy, a patient post-operatively has a hoarse voice but can still raise the pitch. Which nerve is most likely injured and what structure does it supply?

• A External laryngeal nerve; cricothyroid muscle
• B Recurrent laryngeal nerve; all intrinsic laryngeal muscles except cricothyroid ✓
• C Internal laryngeal nerve; sensation above the vocal cords
• D Superior laryngeal nerve main trunk; all laryngeal muscles

Explanation

The recurrent laryngeal nerve (RLN) supplies all intrinsic laryngeal muscles except the cricothyroid. Unilateral RLN injury causes vocal cord paralysis in the paramedian position, resulting in hoarseness. The cricothyroid muscle (supplied by the external laryngeal nerve) tenses the vocal cord to raise pitch; since this is intact, the patient can still raise pitch. If the external laryngeal nerve were injured, the patient would have a monotone voice but no gross hoarseness. The internal laryngeal nerve is purely sensory.

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

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Written and medically reviewed by the StethoPrep medical team.