During a thyroidectomy, the surgeon identifies the external branch of the superior laryngeal nerve (EBSLN). Injury to this nerve would most characteristically result in which vocal change?

• A Hoarseness and breathy voice due to paralysis of all intrinsic laryngeal muscles
• B Loss of high-pitched phonation and inability to increase vocal pitch; speaking voice may appear normal ✓
• C Complete aphonia due to bilateral vocal cord paralysis
• D Whispering voice with intact cough reflex

Explanation

The EBSLN (external branch of superior laryngeal nerve) is a pure motor nerve supplying the cricothyroid muscle, the only intrinsic laryngeal muscle NOT supplied by the recurrent laryngeal nerve. Cricothyroid tenses the vocal cords, enabling high-pitched phonation. EBSLN injury (common during ligation of the superior thyroid artery) causes loss of high-pitch voice — the 'singer's nerve' injury. Conversational voice quality is often preserved, making the injury underdiagnosed. The recurrent laryngeal nerve supplies all other intrinsic laryngeal muscles; its injury causes hoarseness and respiratory stridor.

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

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Written and medically reviewed by the StethoPrep medical team.