During a right hemithyroidectomy, the surgeon identifies the right external laryngeal nerve (EBSLN). Which structure is at risk if the nerve is not identified during ligation of the superior thyroid vessels?

• A Inferior pharyngeal constrictor muscle
• B Cricothyroid muscle ✓
• C Posterior cricoarytenoid muscle
• D Thyroarytenoid muscle

Explanation

The external branch of the superior laryngeal nerve (EBSLN) innervates the cricothyroid muscle, which is the only external laryngeal muscle and functions to tense the vocal cord, raising voice pitch. Injury causes subtle voice changes — inability to hit high notes — which may not be detectable by routine laryngoscopy. The posterior cricoarytenoid is the sole vocal cord abductor, innervated by the recurrent laryngeal nerve. Thyroarytenoid and inferior pharyngeal constrictor have different innervation. The EBSLN runs close to the superior thyroid artery and should be identified before vessel ligation.

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

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Written and medically reviewed by the StethoPrep medical team.