A thyroid surgeon performing a total thyroidectomy must preserve the external branch of the superior laryngeal nerve. Injury to this nerve would most likely cause:

• A Hoarseness and inability to abduct the vocal cord
• B Loss of sensation below the vocal folds
• C Dysphagia due to pharyngeal muscle paralysis
• D Loss of pitch control and inability to produce high-pitched sounds ✓

Explanation

The external branch of the superior laryngeal nerve (EBSLN) supplies the cricothyroid muscle, which is the sole tensor of the vocal cord and is responsible for increasing pitch. Injury to the EBSLN results in inability to tense the vocal cord, causing loss of high-pitched phonation — particularly evident in singers (hence called the 'nerve of the opera singer'). The internal branch carries sensory fibers above the vocal folds. Hoarseness from abductor paralysis is caused by injury to the recurrent laryngeal nerve, not the EBSLN.

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

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Written and medically reviewed by the StethoPrep medical team.