Randomized Controlled Trial of Visualization Versus Neuromonitoring of the External Branch of the Superior Laryngeal Nerve During Thyroidectomy.

Phonation changes following thyroidectomy have been reported in many investigations. They are considered to be multifactorial in origin and can be a consequence of laryngeal nerve injury or other events during thyroidectomy including arytenoids trauma after endotracheal intubation, cricothyroid dysfunction, strap muscle malfunction or lesion of the perithyroidal neural plexus, laryngotracheal fixation with impairment of vertical movement and psychological reaction to the operation. Injury to the external branch of the superior laryngeal nerve (EBSLN) can occur during the dissection and clamping of the superior thyroid vessels and the prevalence of this complication has been reported from 0.5% to 58%. This injury causes a complete paralysis of the cricothyroid muscle which results in lowered fundamental frequency of the voice and worsened voice performance in producing high-frequency sounds. Intraoperative nerve monitoring (IONM) has gained widespread acceptance as an adjunct to the gold standard of visual nerve identification and this technique can be used to identify both the recurrent laryngeal nerve (RLN) and the EBSLN. However, it remains unclear if there is any IONM added-value to the clinical outcome of thyroidectomy in terms of preserved individual voice performance. This study was designed to test that hypothesis.