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

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

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

Injury to the external branch of the superior laryngeal nerve (EBSLN) during thyroidectomy results in lowered fundamental frequency of the voice and worsened voice performance in producing high-frequency sounds. It remains unclear if use of intraoperative nerve monitoring (IONM) can improve clinical outcome of thyroidectomy in terms of preserved individual voice performance. This study was designed to test that hypothesis.

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.

External branch of the superior laryngeal nerve,, Recurrent laryngeal nerve,, Intraoperative neuromonitoring,, Thyroid surgery

Electrical stimulation of the nerve: 1 mA, 4 Hz with surface electromyography of the vocalis muscles.

Anatomical variability of the external branch of the superior laryngeal nerve according to Cernea classification.

The voice assessment included pre- and postoperative videostrobolaryngoscopy and analysis of maximum phonation time (MPT), voice level (VL), fundamental frequency (Fo), and voice quality rating on GRBAS scale.

Inclusion Criteria: thyroid pathology qualified for first-time bilateral neck surgery in a female patient with small to moderate sized goiter (below 100 ml in volume). Exclusion Criteria: male gender, previous neck surgery, unilateral thyroid pathology eligible for unilateral lobectomy, goiter volume above 100 ml, preoperatively diagnosed RLN palsy, abnormal preoperative voice assessment on GRBAS scale, pregnancy or lactation, age below 18 years, high-risk patients ASA 4 grade (American Society of Anesthesiology), inability to comply with the scheduled follow-up protocol.

Jagiellonian University, College of Medicine, Department of Endocrine Surgery, 3rd Chair of General Surgery

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