Although injury to the RLN results in hoarseness (unilateral injury) or airway obstruction (bilateral injury), injury to the superior laryngeal nerve (SLN) results in a more subtle injury, affecting the ability to:A. Speak loudly or sing high notes
The external branch of the superior laryngeal nerve (SLN) lies on the inferior pharyngeal constrictor muscle and descends alongside the superior thyroid vessels before innervating the cricothyroid muscle. Therefore the superior pole vessels should not be ligated en masse, but should be individually divided low on the thyroid gland. Injury to the SLN leads to inability to tense the ipsilateral vocal cord, and impairs the ability to "hit high notes" while singing, or projecting the voice loudly.