Electrophysiologic identification and monitoring of the external branch of superior laryngeal nerve during thyroidectomy.

OBJECTIVE: The aim of the study is to examine the correlation between weight, gender, and race with external branch of superior laryngeal nerve (EBSLN) visualization. Furthermore, we compared normative EBSLN neural-monitoring values to those of the recurrent laryngeal nerve (RLN).

STUDY DESIGN: Retrospective study.

SETTING: North American tertiary academic hospital.

SUBJECTS AND METHODS: A retrospective, institutional review board-approved review was carried out on patients undergoing thyroid surgery by a single surgeon over 3.5 years. Preoperative and postoperative laryngoscopy was done on all patients in accordance with recently published American Academy of Otolaryngology voice optimization at thyroidectomy guidelines, and patients' clinical and operative relevant data were collected.

RESULTS: A total of 447 nerves were at risk in 371 thyroidectomy patients. Of these nerves at risk, 237 (53.02%) were visualized and stimulated. The average amplitude and latency for the EBSLN were significantly lower when compared to the amplitude and the latency of RLN stimulation (P < 0.0001, P < 0.0001, respectively). There was no gender or racial disparity. Out of our study population, the EBSLN was identified in 64.56% in nonobese patients, whereas it was only 40.00% in obese patients (P < 0.001). Additionally, of the 56 patients in whom the EBSLN was visualized on one side and who further underwent bilateral neck exploration, 41 (73%) had visualization of the nerve on the contralateral side as well.

CONCLUSION: EBSLN is less likely to be visualized in obese patients; however, there was no gender or racial disparity. Stimulation of EBSLN was felt to be a useful adjunct during superior pole dissection to assure the nerve integrity.

LEVEL OF EVIDENCE: 4.