TITLE:
Superior Laryngeal Nerve Preservation in Open Thyroid Surgery: Focus on the External Branch
AUTHORS:
Lei Tang, Chuanchang Yin
KEYWORDS:
Thyroidectomy, Open Thyroid Surgery, External Branch of the Superior Laryngeal Nerve, Cricothyroid Muscle, Intraoperative Neuromonitoring, Voice Outcomes
JOURNAL NAME:
Journal of Biosciences and Medicines,
Vol.14 No.11,
October
30,
2026
ABSTRACT: Loss of upper register, projection, or vocal endurance after thyroidectomy can be missed when both vocal folds move normally. Injury to the external branch of the superior laryngeal nerve (EBSLN) is one possible cause. This narrative review examines the anatomy that matters during open thyroidectomy, dissection of the superior pole, intraoperative neural monitoring (IONM), and the investigation of postoperative voice symptoms. The EBSLN lies close to the superior thyroid vessels and is the superior laryngeal branch most likely to be encountered during routine thyroidectomy. The internal branch takes a higher course and presents a different clinical problem. Cernea and Friedman classifications are helpful for anticipating exposure, although neither can define the nerve’s position in an individual operative field. Safe dissection still depends on seeing the structures around the upper pole, avoiding sustained traction, and controlling small vascular branches close to the capsule. Energy devices require the same attention. Stimulation can help locate the nerve and document conduction, but a cricothyroid twitch and an endotracheal electromyographic waveform should be interpreted separately. Randomized studies generally report better identification with IONM. Findings for voice are less uniform, in part because the studies used different endpoints and follow-up periods. An intraoperative loss of signal is therefore not equivalent to a permanent clinical deficit. Routine use of IONM depends on local equipment and experience; it is particularly useful when the nerve is displaced, hidden, or difficult to separate from the superior pedicle. When postoperative symptoms persist, evaluation should include other neural, structural, and intubation-related causes. Preservation is best judged from the preoperative voice, the operative record, and subsequent functional assessment.