The effect of strap muscle transection on voice and swallowing changes after thyroidectomy in patients without laryngeal nerve injury.

INTRODUCTION: Voice and swallowing symptoms are frequently reported after thyroidectomy even without laryngeal nerve injury. We aimed to evaluate the effect of strap muscle transection on voice and swallowing outcome after thyroidectomy. METHODS: Group 1 (G1) consisted of 17 patients who had their strap muscles transected during thyroidectomy and group 2 (G2) consisted of 17 patients who had their strap muscles preserved during thyroidectomy. None of the patients had laryngeal nerve injury. Voice impairment scores (VIS) and swallowing impairment scores (SIS) were obtained preoperatively and at 1 week and 1, 3 and 6 months postoperatively. Pre- and postoperative vocal cord examinations were performed for all patients. The external branch of the superior laryngeal nerve (EBSLN) was evaluated by intraoperative cricothyroid muscle electromyography. RESULTS: There was no significant difference in VIS and SIS between the two groups. At postoperative week 1, the VIS and SIS for each group were above preoperative values (G1: p = 0.005 and p = 0.035; G2: p = 0.031, p = 0.346, for VIS and SIS respectively). The VIS and SIS scores at 6 months postoperatively were significantly lower than those of the first week postoperatively (G1: p = 0.04 and p = 0.001; G2: p = 0.022 and p = 0.034 respectively) and similar to preoperative values (G1: p = 0.924 and p = 0.086; G2: p = 0.822 and p = 0.187 respectively). CONCLUSION: Although voice and swallowing complaints increased in the early postoperative period even without recurrent laryngeal nerve and EBSLN injuries, these symptoms are not related with the strap muscle transection.

Investigation of potential neuropharmacological activity of neostigmine-glycopyrrolate for intraoperative neural monitoring in thyroid surgery.

Intraoperative neuromonitoring (IONM) is frequently used in thyroid surgery to reduce recurrent laryngeal nerve injury. The use of neuromuscular blockade agent to facilitate tracheal intubation, is a common cause of IONM failure. We performed a retrospective analysis to assess the efficacy of neostigmine-glycopyrrolate as a neuromuscular blockade reversal agent for IONM during thyroid surgery. Rocuronium (0.6 mg/kg) was administered for muscle relaxation. Neostigmine (2 mg) and glycopyrrolate (0.4 mg) were administered immediately after intubation. Cricothyroid muscle-twitch response upon external branch of superior laryngeal nerve stimulation and electromyography amplitudes of vagal and recurrent laryngeal nerves before (V1, R1) and after thyroid resection (V2, R2) were recorded. Fifty patients (23 males, 27 females) were included in the analysis. The diagnoses comprised 43 papillary thyroid carcinomas and seven benign diseases. The mean time between rocuronium injection and neostigmine-glycopyrrolate injection was 5.1 ± 1.2 min, and the mean time from neostigmine-glycopyrrolate injection to successful cricothyroid muscle twitching upon external branch of superior laryngeal nerve stimulation was 21.0 ± 4.5 min. All patients had V1 and R1 amplitudes of more than 500 µV each, with mean V1 and R1 amplitudes of 985.3 ± 471.6 µV and 1177.2 ± 572.7 µV, respectively. Neostigmine-glycopyrrolate was effectively used as a neuromuscular blockade reversal agent for IONM in thyroid surgeries without a significant increase in bucking events. Administration of neostigmine-glycopyrrolate immediately after intubation can be recommended for successful NMB reversal to facilitate IONM during thyroid surgery.

Training Courses in Laryngeal Nerve Monitoring in Thyroid and Parathyroid Surgery- The INMSG Consensus Statement.

Intraoperative neural monitoring (IONM) is now an integral aspect of thyroid surgery in many centers. Interest in IONM and the number of institutions that perform monitored thyroidectomies have increased throughout the world in recent years. For surgeons considering the introduction of IONM in their practice, specific training in IONM devices and procedures can substantially shorten the learning curve. The International Neural Monitoring Study Group (INMSG) has been at the forefront of IONM technology and procedural adoption since the introduction of neural monitoring in thyroid and parathyroid surgery. The purpose of this document is to define the INMSG consensus on essential elements of IONM training courses. Specifically, this document describes the minimum training required for teaching practical application of IONM and consensus views on key issues that must be addressed for the safe and reliable introduction of IONM in surgical practice. The intent of this publication is to provide societies, course directors, teaching institutions, and national organizations with a practical reference for developing IONM training programs. With these guidelines, IONM will be implemented optimally, to the ultimate benefit of the thyroid and parathyroid surgical patients.

Simple technique to preserve the external branch of the superior laryngeal nerve during thyroidectomy: Clinical practicability of an attachable nerve stimulator.

OBJECTIVE: This study aimed to demonstrate the usefulness of an attachable magnetic nerve stimulator for preservation of the external branch of the superior laryngeal nerve (EBSLN) during thyroidectomy. METHODS: We retrospectively analyzed 120 female patients, of which 60 underwent thyroidectomy with an attachable magnetic nerve stimulator (magnetic group) and the remaining 60 underwent thyroidectomy with a conventional method without EBSLN identification (control group). For both groups, objective and subjective voice parameters were investigated on the day before surgery and at 2 weeks and 2 months after surgery. RESULTS: In the magnetic group, a magnetic nerve stimulator was used to ligate only the site without cricothyroid muscle (CTM) twitching, and thyroid surgery was successfully performed without damage to the EBSLN. In the control group, objective voice parameters, including fundamental frequency, voice range profile (VRP), highest VRP (VRP-H), and maximal phonation time, and the subjective thyroidectomy-related voice questionnaire score were significantly decreased at 2 months after surgery compared to preoperative values. Compared to the control group, the magnetic group did not show a significant decrease in the objective VRP and VRP-H at 2 months after surgery. CONCLUSION: The use of metallic surgical instruments with an attachable magnetic nerve stimulator may provide surgeons with real-time feedback on CTM twitching feedback and EBSLN status. Compared to direct EBSLN identification during thyroidectomy, this is a simple, easy, and noninvasive method for EBSLN preservation that is useful, especially for less-experienced surgeons.

Neural Monitoring of the External Branch of the Superior Laryngeal Nerve During Transoral Thyroidectomy.

OBJECTIVES/HYPOTHESIS: There is no study regarding intraoperative neural monitoring (IONM) of the external branch of the superior laryngeal nerve (EBSLN) during transoral thyroidectomy. The objective of this study was to evaluate the feasibility and success rate of electrical identification of the EBSLN during transoral robotic or endoscopic thyroidectomy. STUDY DESIGN: Case series study. METHODS: We studied a cohort of 76 patients (87 nerves at risk, (NARs)) who underwent transoral robotic or endoscopic thyroidectomy and simultaneous intermittent IONM between July 2017 and May 2019. We performed the standard IONM procedure plus routine neural monitoring of the EBSLN. IONM and surgical outcome data were prospectively collected. RESULTS: Sixty-one patients underwent the robotic procedure, and 15 patients underwent the endoscopic procedure. Thirty-seven external branches of the superior laryngeal nerves at risk (42.5%) were electrically identified using electromyography signals (31 NARs, 35.6%) or cricothyroid muscle twitches (6 NARs, 6.9%). The mean pre-(S1) and post-dissection (S2) amplitudes of the EBSLN were 372 ± 147 and 351 ± 159 µV, respectively. The identification rates were not different between the robotic and endoscopic procedures. In comparing the early 20 NARs (18 patients) and the later 67 NARs (58 patients), the identification rate was higher in the later cases, although the difference was not statistically significant (25.0% vs. 47.8%, P = .079). CONCLUSION: IONM of the EBSLN is feasible and useful in identifying and preserving the nerve during transoral thyroidectomy, although the identification rate of the nerve is relatively low. LEVEL OF EVIDENCE: 4 Laryngoscope, 131:E671-E676, 2021.

Surgical management of the compromised recurrent laryngeal nerve in thyroid cancer.

Surgical management of thyroid cancer requires careful consideration of the recurrent laryngeal nerve and its impact on glottic function. Management of the compromised recurrent laryngeal nerve is a complex task, requiring synthesis of multiple elements. The surgeon must have an appreciation for preoperative recurrent laryngeal nerve function, intraoperative anatomic and electromyographic information, disease characteristics, and relevant patient factors. Preoperative clinical evaluation including preoperative laryngoscopy and assessment of recurrent laryngeal nerve risk is essential to formulating a surgical plan and providing appropriate patient counseling. Intraoperative neuromonitoring information has significant implications for surgical management of the injured or invaded recurrent laryngeal nerve and informs strategy with respect to staging of bilateral surgery. Disease characteristics and patient-related factors, including patient preference, must be considered with intraoperative decision-making. Multidisciplinary discussion and patient communication are essential for effective management and successful surgical outcome.

Intraoperative Neurological Monitoring During Neck Dissection for Esophageal Cancer With Aberrant Subclavian Artery.

We report a case of esophageal cancer with a non-recurrent inferior laryngeal nerve associated with aberrant right subclavian artery that was treated by neck dissection using intraoperative neurological monitoring followed by thoracoscopic esophagectomy. A 76-year-old man had dysphagia. Endoscopy revealed thoracic esophageal cancer, and computed tomography revealed the presence of an aberrant right subclavian artery between the esophagus and vertebrae. We performed neck dissection followed by thoracoscopic esophagectomy. During the neck dissection, we confirmed a non-recurrent inferior laryngeal nerve through intraoperative neurological monitoring. No postoperative complications were observed, and the patient was discharged 19 days after surgery. We recommend using intraoperative neurological monitoring to avoid injury to the non-recurrent inferior laryngeal nerve associated with the aberrant right subclavian artery.

A novel approach to neurologic function sparing surgical management of vagal schwannomas: Continuous intraoperative nerve monitoring of the laryngeal adductor reflex.

BACKGROUND: Vagal schwannomas are rare, benign tumors of the head and neck. Nerve damage during surgical resection is associated with significant morbidity. A new technique of continuous intraoperative nerve monitoring (IONM) that allows for real-time intraoperative feedback has recently been used for thyroid and cervical spine surgeries but has not previously been used in vagal schwannoma surgery. METHODS: Case series of three patients who underwent vagal schwannoma excision utilizing this novel IONM technique. The recurrent laryngeal and vagus nerves were monitored via the laryngeal adductor reflex (LAR) using an electromyographic endotracheal tube. RESULTS: Three patients with suspected vagal schwannomas were treated surgically using the intracapsular enucleation approach with a combination of intermittent IONM and continuous IONM of the LAR. CONCLUSION: This combination of continuous and intermittent IONM can be used to preserve vagal laryngeal innervation and function and may represent the future standard of care for vagal schwannoma excision.

Non-Recurrent Laryngeal Nerve and Concurrent Vascular Variants: A Review.

OBJECTIVE: The purpose of this paper is to review the current data on the coexistence of non-recurrent laryngeal nerve (RLN) and vascular variations. METHODS: A systematic literature search was conducted on MEDLINE for case reports, original articles and reviews regarding the presence of non-RLN and coexisting vascular variants. RESULTS: From the literature search, 104 cases of non-RLN with confirmed vascular variants were reported. More specifically, 97.7% (n=101) of cases involved a right and 2.3% (n=3) a left non-RLN. The most common concurrent vascular variant reported with a right non-RLN was an aberrant right subclavian artery (97%; n=98). One case report (0.9%) of an intrathyroidal right common carotid artery was noted and 2 cases (1.9%) were associated with normal vascular anatomy. Furthermore, all 3 cases of a left non-RLN were associated with a right aortic arch, while 2 of them were also accompanied with situs inversus. CONCLUSIONS: The presence of vascular variations of the great vessels must prompt the surgeon to search for a non-RLN. Intraoperative neuromonitoring increases the detection rate of non-RLN. Further research is required to determine anatomic landmarks for the perioperative identification of a non-RLN, allowing its protection from potential injury.

Surgical anatomy of the external branch of the superior laryngeal nerve: a systematic review and meta-analysis.

PURPOSE: To provide a comprehensive evidence-based assessment of the anatomical characteristics of the external branch of the superior laryngeal nerve (EBSLN). MATERIALS AND METHODS: A thorough systematic search was performed on the major electronic databases PubMed, EMBASE, Cochrane library, and ScienceDirect to identify eligible studies. Data were extracted and pooled into a meta-analysis. The primary outcomes were the EBSLN identification rate (total number of EBSLN identified divided by the total number of dissected hemilarynges) and the prevalence of various EBSLN types. RESULTS: A total of 56 studies (n = 13,444 hemilarynges) were included. The overall pooled EBSLN identification rate was 89.24% (95% CI 85.49-92.49). This rate was higher for cadaveric (95.00%; 95% CI 89.73-99.35) compared to that reported in intraoperative studies (86.99%; 95% CI 82.37-91.01). Significantly higher identification rates were reported for studies in which intraoperative nerve monitoring was used (95.90%; 95% CI 94.30-97.25) compared to those which only relied on direct visual identification of the EBSLN (76.56%; 95% CI 69.34-83.08). Overall, Cernea type IIa (nerves crossing the superior thyroid artery less than 1 cm above the upper edge of the superior thyroid pole) and Friedman type 1 (nerves running their entire course superficial to the inferior pharyngeal constrictor) were the most prevalent (41.84%; 95% CI 33.28-48.08 and 50%; 95% CI 29.90-65.62, respectively). The combined prevalence of Cernea IIa and IIb (nerves crossing the superior thyroid artery below the upper edge of the superior thyroid pole) was higher in intraoperative studies compared to that in cadaveric studies (64.3% vs 49.4%). The EBSLN coursed medial to the superior thyroid artery in 70.98% (95% CI 55.14-84.68) of all cases. CONCLUSION: The use of intraoperative nerve monitoring improves EBSLN identification rates. In light of the highly variable anatomical patterns displayed by the EBSLN, thorough pre-operative knowledge of its anatomy can be crucial in minimizing incidences of its iatrogenic injury.

Intraoperative Neural Monitoring in Endoscopic Thyroidectomy Via Bilateral Areola Approach.

OBJECTIVE: The aim of this report was dual: (a) to describe the step by step standardized intraoperative neural monitoring (IONM) procedure for recurrent laryngeal nerve (RLN) and external branch of the superior laryngeal nerve focusing on percutaneous IONM method, and (b) evaluation and outcomes of intermittent IONM in 237 endoscopic thyroidectomy via bilateral areolar approach cases. MATERIALS AND METHODS: A 10-mm curved incision is made along the margin of the right areola at the 2 to 4 o'clock position for the 30-degree endoscope. Bilaterally 5-mm incisions are required on the edges of the areola at the 11 to 12 o'clock positions as accessory operating ports. Ball-tip, monopolar, single-use, standard stimulating probe with a 10-cm handle and 9-cm shaft is adopted percutaneously for IONM. As reference, on the dominant thyroid lesion side, a 0.5-cm circle is drawn with the center at the intersection of a line 2-cm lateral to the anterior median line and a line 2-cm above the line connecting the bilateral clavicular heads. After ensuring with ultrasonography that no vessels are within the puncture passage, the skin is pierced with an 18-G syringe needle. After withdrawing the needle, the probe is carefully inserted through the tract. IONM is performed according to standards of equipment set up, anesthesia, tube positioning verification tests, and electromyography determinations. RESULTS: A total of 277 nerves at risk were favorably monitored with percutaneous probe stimulation. RLN, vagus nerve, and external branch of the superior laryngeal nerve were successfully determined. There were no instances of IONM malfunction, equipment displacement, or interference with the other endoscopic instruments. IONM probe insertion incision determined no scarring or morbidity in the neck. The incidence of RLN monolateral temporary palsy was 6%. CONCLUSIONS: Standardized monitoring in endoscopic thyroidectomy via bilateral areolar approach is feasible. IONM was implemented by means of percutaneous stimulating probe.

International consensus (ICON) on comprehensive management of the laryngeal nerves risks during thyroid surgery.

The laryngeal monitoring of the inferior and superior laryngeal nerves, and the vagus nerve, has advanced for last years, in practice of thyroid and parathyroid surgery. Different methods are used, using direct or indirect laryngeal stimulation and also intermittent or continuous nerve registration. At present time, various recommendations of it in the world use are reported, and availability of the tool used remains a limit in some countries. The aim of this Icon during Ifos 2017 was to share knowledge about laryngeal intraoperative nerve monitoring (LIONM) procedures and to evaluate current practices used to improve the quality of thyroid and parathyroid surgery. Benefits of LIONM were discussed with three experts (Pr G. Randolph from Boston, Pr Henning Dralle from Halle in Germany, Pr Hoon Yub KIM from Seoul). All of them have been actively involved in the development and use of laryngeal nerve monitoring during thyroid and parathyroid surgery.

Intraoperative Monitoring of External Branch of the Superior Laryngeal Nerve: Functional Identification, Motor Integrity, and its Role on Vocal Cord Function.

PURPOSE: Beside recurrent laryngeal nerve (RLN), protection of the external branch of the superior laryngeal nerve (EBSLN) is required for complication-free thyroid surgery. This study investigates the contribution of intraoperative neuromonitoring (IONM) to identification and motor integrity of the EBSLN. METHODS: This prospective study was performed on 245 EBSLNs in 147 patients with thyroid surgery. The rate of visual identification, contribution of IONM to functional localization, the rate and levels of recordable waveform amplitude from vocal cord (VC) movement were determined during surgery. RESULTS: 164 (66.9%) EBSLNs were visually identified and additional 74 branches were functionally identified by IONM. Additional identification rate of IONM was 30.2%. Seven (2.9%) EBSLNs could not be identified during surgery. Cricothyroid muscle (CTM) twitch established functional integrity in 97.1% of EBSLNs. Electrophysiological stimulation of 151 (63.4%) EBSLNs created waveform amplitude >100 µV that mean amplitude level was calculated as 186 µV, and an amplitude >300 µV was recorded in 19 of 151 (12.6%) EBSLNs. CONCLUSIONS: In addition to visual identification, surgeons can functionally localize the EBSLN with the assistance of IONM that CTM twitch is a reliable evience for functional integrity of the EBSLN. In the majority of patients, stimulation of the EBSLN creates recordable waveform amplitude thus the EBSLN appears to be a second source of motor innervations for intrinsic laryngeal muscles.

Assessment and management of cervico-mediastinal goiter.

Cervico-mediastinal goiter is a particular entity from the point of view of thyroid surgery. Its volume, hardness and intrathoracic extension require the surgeon to adapt technique and perform a painstaking preoperative work-up, so as to draw up fully-fledged plan. CT is now indispensable, to anticipate risks and determine whether sternotomy is needed. Surgery seems to induce more postoperative complications than in conventional surgery, although they can be reduced by retrograde dissection of the inferior laryngeal nerve and downward dissection of the posterior side of the lobe to optimize control of adjacent structures. This surgery requires optimal teamwork between all of the specialties involved in patient management: medical, radiological, anesthesiological and surgical.

Neuromonitorización intraoperatoria en cirugía laringotraqueal / Intraoperative nerve monitoring in laryngotracheal surgery

La cirugía laringotraqueal conlleva un riesgo inherente de lesión de los nervios laríngeos recurrentes (NLR). Estas complicaciones incluyen desde una disfonía menor hasta una parálisis bilateral de ambas cuerdas vocales. La neuromonitorización intraoperatoria de los NLR se desarrolló en el campo de la cirugía tiroidea con la finalidad de preservar la función de los nervios y de las cuerdas vocales. Sin embargo, la cirugía traqueal precisa una intubación intracampo de la tráquea distal, lo que limita el uso de la neuromonitorización mediante los tubos endotraqueales convencionales con electrodos de superficie. Expuesto este reto, presentamos un método alternativo para la neuromonitorización intraoperatoria de los NLR durante la cirugía laringotraqueal mediante la inserción de electrodos en la musculatura intralaríngea a través de una punción bilateral del cartílago tiroides (AU)

Laryngotracheal surgery has an inherent risk of injury to the recurrent laryngeal nerves (RLN). These complications go from minor dysphonia to even bilateral vocal cord paralysis. The intraoperative neuromonitoring of the RLN was developed in the field of thyroid surgery, in order to preserve nerve and vocal cord function. However, tracheal surgery requires in-field intubation of the distal trachea, which limits the use of nerve monitoring using conventional endotracheal tube with surface electrodes. Given these challenges, we present an alternative method for nerve monitoring during laryngotracheal surgery through the insertion of electrodes within the endolaryngeal musculature by bilateral puncture (AU)

The Identification, Preservation and Classification of the External Branch of the Superior Laryngeal Nerve in Thyroidectomy.

BACKGROUND: Avoiding injury to the external branch of the superior laryngeal nerve is one of the major challenges during thyroid operation. The aim of this study was to propose a practical classification of the external branch of the superior laryngeal nerve. METHODS: A retrospective study of total thyroidectomy was performed. Totally 240 patients were included, with 480 external branches of the superior laryngeal nerves explored by intraoperative neuromonitoring. The classification of the external branch of the superior laryngeal nerve was determined by the distance between the upper edge of the superior thyroid pole and the lowest point of the nerve when the thyroid lobe was retracted in the lateral and inferior direction. Multinomial logistic regression analysis was run to predict the type of the nerve from several variables. RESULTS: The identification rate of the external branch of the superior laryngeal nerve was 98.54% (473 of 480 nerves). Higher ratio of longitudinal size of the thyroid lobe to ipsilateral neck length increased the likelihood of that both the type 2 and 3 nerve with respect to type 1 nerve, with OR 2.72, 95% CI = 1.21-6.12 and OR 5.30, 95% CI = 2.09-13.44, respectively. (1a) The nerve whose lowest point (entry into the muscle) was located more than 1 cm above the horizontal plane passing the upper border of superior thyroid pole. (1b) The nerve whose lowest point (the point right above the superior thyroid pole) was located more than 1 cm above the plane. (2a) The nerve whose lowest point (entry into the muscle) was located within 1 cm above the plane. (2b) The nerve whose lowest point (the point right above the superior thyroid pole) was located within 1 cm above the plane. (3a) The nerve whose lowest point (entry into the muscle) was located below the plane. (3b) The nerve whose lowest point (the point right below the superior thyroid pole) was located anterior to the gland. (3c) The nerve whose lowest point (the point right below the superior thyroid pole) was located posterior to the gland. CONCLUSIONS: Identification rate of the external branch of the superior laryngeal nerve by intraoperative neuromonitoring was significantly high. Understanding the new practical classification of the nerve allows for better identification and function preservation of this nerve during thyroidectomy.

Anatomic Characteristics, Identification, and Protection of the Nonrecurrent Laryngeal Nerve during Thyroidectomy.

Objective We aimed to investigate the anatomical features and variation pattern of the nonrecurrent laryngeal nerve (NRLN), summarize the methods for identifying the NRLN before and during thyroidectomy, and share experiences regarding preventing and treating its injury. Study Design Retrospective case data analysis. Setting First Affiliated Hospital of Harbin Medical University. Subjects and Methods Between January 2002 and May 2016, 7392 patients underwent thyroidectomy in our hospital. Of them, 28 patients with NRLN were identified, and their clinical data were retrospectively analyzed. Results This study included 7392 patients in which the recurrent laryngeal nerves (RLNs) were routinely identified during surgery. The presence of NRLN was intraoperatively confirmed in 28 patients. All the NRLNs were located on the right side and its overall incidence was 0.37%. Five of the NRLNs were classified as type I, 19 as type IIa, and 4 as type IIb. Of the 28 cases, 4 NRLNs were injured during surgery, in which primary end-to-end anastomosis or local seal with corticosteroid injection was performed as a remedy. In the 4 patients with NRLN injury, 2 presented with postoperative hoarseness that indicated vocal cord paralysis confirmed by laryngoscope; the other 2 patients' voices had no significant changes. Conclusion The NRLN, which is rare in clinical practice and predominantly right-sided, is anatomically more complex and variant at a higher risk of surgical injury. The key factors to accurately identify NRLN and to effectively prevent its injury include careful interpretation of auxiliary examination results before surgery, raising awareness of its presence, meticulous dissection, and routine exposure of the RLN during surgery.

Is intraoperative neural monitoring necessary for exploration of the superior laryngeal nerve?

BACKGROUND: We aimed to evaluate the contribution of intraoperative neuromonitoring to the visual and functional identification of the external branch of the superior laryngeal nerve and the effect on postoperative voice changes. METHODS: The prospective data of 221 patients (183 women, 38 men) who underwent thyroid operation with intraoperative neuromonitoring for exploration of the external branch of the superior laryngeal nerve were evaluated retrospectively. The surface endotracheal tube-based Medtronic NIM3 (Medtronic, Jacksonville, FL) intraoperative neuromonitoring device was used. The function of the external branch of the superior laryngeal nerve was evaluated by cricothyroid muscle twitch. Additionally, the contribution of the external branch of the superior laryngeal nerve to vocal cord adduction was evaluated using electromyographic records. RESULTS: A total of 374 (95.2%) of 393 external branch of the superior laryngeal nerves were identified; 145 (36.9%) external branch of the superior laryngeal nerves were identified visually before being stimulated with a probe, and 130 (33.1%) external branch of the superior laryngeal nerves were identified visually after being identified with a probe. Although 99 (25.2%) external branch of the superior laryngeal nerves were identified with a probe, they were not visualized. Intraoperative neuromonitoring provided meaningful contributions to visual (P = .001) and functional (P = .001) identification of the external branch of the superior laryngeal nerve. Positive electromyographic responses were recorded from 257 external branch of the superior laryngeal nerves (68.7%). After the patients with recurrent laryngeal nerve palsy were excluded, voice changes were detected in 6 (3.3%) of 184 patients with identified external branch of the superior laryngeal nerves and 3 (20%) of 15 patients in whom at least 1 external branch of the superior laryngeal nerve could not be identified with intraoperative neuromonitoring. CONCLUSION: Intraoperative neuromonitoring provided an important contribution to the visual and functional identification of the external branch of the superior laryngeal nerve. Intraoperative neuromonitoring is a helpful adjunct for identifying the external branch of the superior laryngeal nerve.

Contribution of intraoperative neural monitoring to preservation of the external branch of the superior laryngeal nerve: a randomized prospective clinical trial.

PURPOSE: The purpose of this study was to evaluate the effect of intraoperative neuromonitoring (IONM) on the injury rate of the external branch of the superior laryngeal nerve (EBSLN) during thyroidectomy. METHODS: A total of 133 consenting patients (98 female, 35 male; mean age, 45.6 ± 11.7 years) undergoing thyroidectomy were randomly assigned to 2 groups. In group 1 (n = 65 patients, 105 nerves), superior thyroid pole dissection was performed with no attempt to identify the EBSLN; in group 2 (n = 68 patients, 106 nerves), IONM was used to identify the EBSLN during surgery. EBSLN function was evaluated by intraoperative electromyography of the cricothyroid muscle. The EBSLN Voice Impairment Index-5 (VII-5) was conducted preoperatively and at 1, 3, and 6 months postoperatively. The primary outcome was the prevalence of EBSLN injury. The secondary outcomes were the identification rate of the EBSLN using IONM and changes in postoperative voice performance. RESULTS: EBSLN injury was detected in eight (12.3%) patients and nine (8.6%) nerves in group 1 and in one (1.5%) patient and one (0.9%) nerve in group 2 (patients, p = 0.015; nerves, p = 0.010). IONM contributed significantly to visual (p < 0.001) and functional (p < 0.001) nerve identification in group 2. The VII-5 indicated more voice changes in group 1 than 2 at 1, 3, and 6 months postoperatively (p = 0.012, p = 0.015, and p = 0.02, respectively). CONCLUSION: IONM contributes to visual and functional identification of the EBSLN and decreases the rate of EBSLN injury during superior pole dissection. Routine use of IONM to identify the EBSLN will minimize the risk of injury during thyroidectomy.