Which nerve is most likely damaged by thyroid surgery to explain loss of sensation above the vocal folds?

• A. External branch of the recurrent laryngeal nerve
• B. Internal branch of the recurrent laryngeal nerve
• C. External branch of the superior laryngeal nerve
• D. Internal branch of the superior laryngeal nerve

Answer: (D)

The main idea is where the laryngeal sensory nerves supply the mucosa. Sensation above the vocal folds is provided by the internal branch of the superior laryngeal nerve. If this branch is injured during thyroid surgery, the person loses sensation in the laryngeal mucosa above the vocal cords (including the laryngeal vestibule and epiglottic region).

In contrast, the external branch of the superior laryngeal nerve is mainly motor to the cricothyroid muscle, so its injury would affect voice tension for pitch rather than sensation. The recurrent laryngeal nerve (and its branches) handles most intrinsic muscle innervation and provides sensation below the vocal folds, so damage there would affect areas under the vocal cords rather than above. Therefore, loss of sensation above the vocal folds points to injury of the internal branch of the superior laryngeal nerve.