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Background: Neuromuscular blocking agents provide muscular relaxation for tracheal intubation and surgery. However, the degree of neuromuscular block may disturb neuromuscular transmission and lead to weak electromyography during intraoperative neuromonitoring. This study aimed to investigate a surgeon-friendly neuromuscular block degree titrated sugammadex protocol to maintain both intraoperative neuromonitoring quality and surgical relaxation during thyroid surgery., Methods: A total of 116 patients were enrolled into two groups and underwent elective thyroid surgery with intraoperative neuromonitoring. All patients followed a standardized intraoperative neuromonitoring protocol with continuous neuromuscular transmission monitoring and received 0.6 mg/kg rocuronium for tracheal intubation. Patients were allocated into two groups according to the degree of neuromuscular block when the anterior surface of the thyroid gland was exposed. The neuromuscular block degree was assessed by the train-of-four (TOF) count and ratio. Patients in group I received sugammadex 0.25 mg/kg for non-deep neuromuscular block degree (TOF count = 1~4). Patients in group II were administered sugammadex 0.5 mg/kg for deep neuromuscular block degree (TOF count = 0). The quality of the intraoperative neuromonitoring was measured using the V 1 electromyography (EMG) amplitude. An amplitude less than 500 μV and greater than 500 μV was defined as weak and satisfactory, respectively., Results: The quality of the intraoperative neuromonitoring was not different between groups I and II (satisfactory/weak: 75/1 vs. 38/2, P = 0.14). The quality of surgical relaxation was acceptable after sugammadex injection and showed no difference between groups [55/76 (72.3%) in group I vs. 33/40 (82.5%) in group II, P = 0.23]., Conclusions: This surgeon-centered sugammadex protocol guided by neuromuscular block degree (0.5 mg/kg for deep block and 0.25 mg/kg for others) showed comparably high intraoperative neuromonitoring quality and adequate surgical relaxation. The results expanded the practicality of sugammadex for precise neuromuscular block management during monitored thyroidectomy., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Lu, Hsu, Chang, Wu, Huang, Lin, Ko, Dionigi, Chai, Chiang, Kuo and Wu.)

In the past decade, the use of intraoperative neural monitoring (IONM) in thyroid and parathyroid surgery has been widely accepted by surgeons as a useful technology for improving laryngeal nerve identification and voice outcomes, facilitating neurophysiological research, educating and training surgeons, and reducing surgical complications and malpractice litigation. Informing patients about IONM is not only good practice and helpful in promoting the efficient use of IONM resources but is indispensable for effective shared decision making between the patient and surgeon. The International Neural Monitoring Study Group (INMSG) feels complete discussion of IONM in the preoperative planning and patient consent process is important in all patients undergoing thyroid and parathyroid surgery. The purpose of this publication is to evaluate the impact of IONM on the informed consent process before thyroid and parathyroid surgery and to review the current INMSG consensus on evidence-based consent. The objective of this consensus statement, which outlines general and specific considerations as well as recommended criteria for informed consent for the use of IONM, is to assist surgeons and patients in the processes of informed consent and shared decision making before thyroid and parathyroid surgery., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Wu, Huang, Randolph, Barczyński, Schneider, Chiang, Silver Karcioglu, Wojtczak, Frattini, Gualniera, Sun, Weber, Angelos, Dralle and Dionigi.)

Technological advances in thyroid surgery have rapidly increased in recent decades. Specifically, recently developed energy-based devices (EBDs) enable simultaneous dissection and sealing tissue. EBDs have many advantages in thyroid surgery, such as reduced blood loss, lower rate of post-operative hypocalcemia, and shorter operation time. However, the rate of recurrent laryngeal nerve (RLN) injury during EBD use has shown statistically inconsistent. EBDs generate high temperature that can cause iatrogenic thermal injury to the RLN by direct or indirect thermal spread. This article reviews relevant medical literatures of conventional electrocauteries and different mechanisms of current EBDs, and compares two safety parameters: safe distance and cooling time. In general, conventional electrocautery generates higher temperature and wider thermal spread range, but when applying EBDs near the RLN adequate activation distance and cooling time are still required to avoid inadvertent thermal injury. To improve voice outcomes in the quality-of-life era, surgeons should observe safety parameters and follow the standard procedures when using EBDs near the RLN in thyroid surgery., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Wang, Huang, Wu, Lin, Tseng, Liu, Lu, Chang, Chen, Chen, Dionigi, Chiang and Wang.)

Background: Alternative methods to overcome limitations of electromyogram (EMG) tube applied for intraoperative neuromonitoring (IONM) of recurrent laryngeal nerve (RLN) during thyroidectomy have been introduced. In this study, we evaluated the feasibility of adhesive skin electrodes for IONM of RLN in patients who underwent thyroidectomy., Methods: A total of 39 nerves at risk were prospectively enrolled in this study. Twenty-five patients with papillary thyroid carcinoma, 3 patients with follicular neoplasm, and 2 patients with Graves' disease underwent thyroidectomy. All patients were intubated with EMG tube, and two disposable pre-gelled surface electrodes were attached to skin at both upper margins of thyroid cartilage. We followed the standard procedure of IONM, and the latency (msec) and amplitude (μV) of each signal were recorded prospectively., Results: Intraoperative neuromonitoring using skin adhesive electrodes was successful in all nerves at risk. Amplitudes of the signals in IONM were significantly lower compared to those from EMG tube at each step of IONM, while no significant difference was identified in latency between two methods. Four nerves at risk (10.3%) showed loss of signal (<100 μV) during the steps of IONM from EMG tube, while all nerves at risk from adhesive skin electrodes showed acceptable biphasic EMG signal., Conclusion: We verified the usefulness of adhesive skin electrodes for IONM of RLN during thyroidectomy. Although lower amplitude remains the major limitation of this technique, adhesive skin electrodes may be considered an alternative method for IONM during thyroidectomy.

Objectives/hypothesis: Intraoperative neural monitoring is a useful adjunct for the laryngeal nerve function assessment during thyroid and parathyroid surgery. Typically, monitoring is performed by measurement of electromyographic responses recorded by endotracheal tube (ETT) surface electrodes. Tube position alterations during surgery can cause displacement of the electrodes relative to the vocal cords, leading to false positive loss of signal. Numerous reports have denoted monitoring equipment-related issues, especially endotracheal tube displacement, as the dominant source of false positive error. The false positive error may result in inappropriate decisions by the surgeon. This study tests the hypothesis that anterior laryngeal electrodes (ALEs) can help reduce this error. Placement of ALEs directly onto the thyroid cartilage represent an adjunctive and possible alternative method to standard ETT surface electrodes., Study Design: Retrospective review., Methods: Fifteen consecutive patients undergoing thyroid and parathyroid surgery with intraoperative neuromonitoring using both ETT electrodes and ALEs were studied. Data collected included site of neural stimulation, laterality, and electromyographic parameters., Results: With vagal and recurrent laryngeal nerve stimulation, the ALEs recorded mean vocalis muscle waveform amplitude within 83% of that recorded with standard ETT electrodes. The latency measurements with the anterior laryngeal and endotracheal electrodes were similar, with both electrodes recording significantly longer latency for the left vagus nerve as compared to the right vagus nerve. With superior laryngeal nerve stimulation, the ALEs recorded a 800% greater mean amplitude than the ETT electrodes. The ALEs demonstrated similar sensitivity to stimulation at low current as ETT electrodes and provided stable intraoperative monitoring information., Conclusions: Compared to ETT surface electrodes, the ALEs provide similar and stable electromyographic responses with equal sensitivity for recording evoked responses during neural monitoring in thyroid and parathyroid surgery. The ALEs offer significantly more robust monitoring of the external branch of the superior laryngeal nerve. Furthermore, ALEs are contained within the operative field, are totally surgeon controlled, and are unaffected by the potential vicissitudes of ETT position during surgery., Level of Evidence: 4 Laryngoscope, 128:2910-2915, 2018., (© 2018 The American Laryngological, Rhinological and Otological Society, Inc.)

Aim: We assess the prevalence and mechanism of recurrent laryngeal nerve (RLN) injury in central neck dissection (CND) for thyroid cancer., Methods: CND with intraoperative neural monitoring was outlined in 1.273 nerves at risk (NAR). RLN lesions were stratified according to: timing (during thyroidectomy versus CND), segmental vs. diffuse injury, mechanism, severity, location, number of lymph nodes dissected and metastastatic. EMG parameters were recorded., Results: 49/1.273NAR (3,8%) documented RLN palsy. 25 nerves were injured during thyroidectomy, 8 while CND. In 16 no precise moment or mechanism of injury was identified. A disrupted point could be identified in 19/25 (76%) and 7/8 (87%) respectively for thyroidectomy and CND steps. Diffuse injury, occurred in 24% and 12,5% respectively for thyroidectomy and CND. Nerves were injured in the all cervical nerve course without any major location for incidence for CND; for thyroidectomy most nerves were injured in the last 1 cm course. Traction (36%) was the leading cause of RLN injury for thyroidectomy. For solely CND, traction, entrapment and thermal injuries were equally frequent. Permanent vs. transient injuries were respectively 8% (4/49) and 92% (n.45/49), overall. Permanent lesions were equally distributed., Conclusions: During CND, RLN palsy still occurs with routine exposure of the nerve even combined with IONM. The incidence of nerve lesions during thyroidectomy is higher than that of CND., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

A variety of electromyography (EMG) recording methods were reported during intraoperative neural monitoring (IONM) of recurrent laryngeal nerve (RLN) in thyroid surgery. This study compared two surface recording methods that were obtained by electrodes on endotracheal tube (ET) and thyroid cartilage (TC). This study analyzed 205 RLNs at risk in 110 patients undergoing monitored thyroidectomy. Each patient was intubated with an EMG ET during general anesthesia. A pair of single needle electrode was inserted obliquely into the TC lamina on each side. Standard IONM procedure was routinely followed, and EMG signals recorded by the ET and TC electrodes at each step were compared. In all nerves, evoked laryngeal EMG signals were reliably recorded by the ET and TC electrodes, and showed the same typical waveform and latency. The EMG signals recorded by the TC electrodes showed significantly higher amplitudes and stability compared to those by the ET electrodes. Both recording methods accurately detected 7 partial loss of signal (LOS) and 2 complete LOS events caused by traction stress, but only the ET electrodes falsely detected 3 LOS events caused by ET displacement during surgical manipulation. Two patients with true complete LOS experienced temporary RLN palsy postoperatively. Neither permanent RLN palsy, nor complications from ET or TC electrodes were encountered in this study. Both electrodes are effective and reliable for recording laryngeal EMG signals during monitored thyroidectomy. Compared to ET electrodes, TC electrodes obtain higher and more stable EMG signals as well as fewer false EMG results during IONM., (Copyright © 2017. Published by Elsevier Taiwan.)

Objectives/hypothesis: This study investigated recurrent laryngeal nerve (RLN) real-time electromyography (EMG) data to define optimal safety parameters of the LigaSure Small Jaw (LSJ) instrument during thyroidectomy., Study Design: Prospective animal model., Methods: Dynamic EMG tracings were recorded from 32 RLNs (16 piglets) during various applications of LSJ around using continuous electrophysiologic monitoring. At varying distances from the RLN, the LSJ was activated (activation study). The LSJ was also applied to the RLN at timed intervals after activation and after a cooling maneuver through placement on the sternocleidomastoid muscle (cooling study)., Results: In the activation study, there was no adverse EMG event at 2 to 5 mm distance (16 RLNs, 96 tests). In the cooling study, there was no adverse EMG event after 2-second cooling time (16 RLNs, 96 tests) or after the LSJ cooling maneuver on the surrounding muscle before reaching the RLNs (8 RLNs, 24 tests)., Conclusion: Based on EMG functional assessment, the safe distance for LSJ activation was 2 mm. Further LSJ-RLN contact was safe if the LSJ was cooled for more than 2 seconds or cooled by touch muscle maneuver. The LSJ should be used with these distance and time parameters in mind to avoid RLN injury., Level of Evidence: N/A. Laryngoscope, 127:1724-1729, 2017., (© 2016 The American Laryngological, Rhinological and Otological Society, Inc.)

Background: The purpose of this study was to investigate the feasibility and value of using intraoperative neuromonitoring (IONM) performed via percutaneous probe stimulation during total endoscopic thyroidectomy., Methods: This study prospectively enrolled a series of 132 consecutive patients with 156 recurrent laryngeal nerves (RLNs) at risk who received total endoscopic thyroidectomy performed via bilateral breast approach using standardized IONM. The stimulation probe was introduced into the working space by percutaneous puncture. During lateral thyroid dissection, the proximal RLN was periodically stimulated to monitor adverse electromyography (EMG) changes. Preoperative and postoperative vocal cord mobility was routinely examined with laryngofiberoscopy., Results: All IONMs were successfully performed via percutaneous probe stimulation with no morbidity or scarring in the neck. Twelve nerves (7.7%) showed significant changes in EMG (amplitude reduction, 50% to 90% from baseline EMG) during the lateral thyroid dissection. Compression near the inferior thyroid artery (70%) and traction near the Berry's ligament (30%) were the most common causative mechanisms, and modification of the surgical maneuver resulted in partial recovery of the EMG changes (amplitude reduction, 10% to 80% before wound closure). Of the 12 nerves with adverse EMG changes (final amplitude reduction, 65% to 80%), 8 nerves showed temporary (3 months or less) vocal cord palsy. No cases of permanent vocal cord palsy occurred in this series., Conclusion: Percutaneous probe stimulation is a simple, effective, and safe method of performing IONM in total endoscopic thyroidectomy when the operating space is limited. © 2017 Wiley Periodicals, Inc. Head Neck 39: 1001-1007, 2017., (© 2017 Wiley Periodicals, Inc.)

Objectives: To compare electromyography (EMG) characteristics of the external branch of superior laryngeal nerve (EBSLN), recurrent laryngeal nerve (RLN), and vagus nerve (VN) evoked with different stimulation probes/dissectors during monitored thyroid surgery., Study Design: Experimental porcine model., Methods: In five piglets (10 EBSLNs/RLNs/VNs), laryngeal EMG was recorded by endotracheal tube surface electrodes with stimulation using five monopolar probes (group I), three bipolar probes (group II), and two stimulation dissectors (group III). The detectable EMG response (DER) was defined as > 100 μV and was obtained with these different probes/dissectors. Electromyography parameters, stimulus-response curve, and distance-sensitivity results were compared., Results: All stimulation probes/dissectors evoked typical EMG waveforms from the EBSLN/RLN/VN with 1 mA current. A stimulus-response curve with increasing EMG amplitude with increase in stimulating current was noted, with the maximum EMG elicited by group I/III probes/dissectors at < 1 mA and at a higher current for group II probes. All groups recorded lower evoked EMG amplitudes when the nerve was stimulated with overlying fascia or when probe/dissector to nerve distance was greater. The mean amplitude decreased by 11%/33%/13% in group I/II/III probes/dissectors when stimulating nerves covered by fascia versus nerves dissected free of overlying fascia. The rate of obtaining DER at 1- or 2-mm distance was significantly higher in group I than in group II/III probes/dissectors (P < 0.001). Latency did not change with any of the stimulation probes/dissectors or trials., Conclusion: Monopolar, bipolar probes, and newer stimulation dissectors all provided valid evoked VN/RLN/EBSLN waveforms. They have different functional sensitivity profiles and vary when stimulating with fascia and at a distance from the nerve. Selection of a stimulation probe/dissector for nerve monitoring can be based on the stimulation characteristics, the intended nerve monitoring application, and the surgeon's preference., Level of Evidence: N/A. Laryngoscope, 127:998-1005, 2017., (© 2016 The American Laryngological, Rhinological and Otological Society, Inc.)

Purpose: The vagus nerve (VN) has essential regulatory roles in the gastric acid secretion and gastrin release. Continuous intraoperative neuromonitoring (CIONM) via VN stimulation is a promising technique in thyroid surgery because it potentially avoids injury to the recurrent laryngeal nerve. However, no studies have investigated changes in gastric acid secretion and gastrin release during CIONM., Method: This prospective study of 58 thyroid surgery patients compared gastric acid and serum gastrin at five time points: (1) before skin incision, (2) after baseline calibration of CIONM probe, (3) +20 min from baseline, (4) before probe removal, and (5) after extubation. Patients were excluded if they had any history of using tobacco, acid suppression medications, or drugs that affect gastric motility. Patients were also excluded if they had any history of gastroesophageal reflux symptoms, gastroesophageal reflux disease, peptic ulcer disease, helicobacter pylori infection, or chronic kidney disease., Results: Non significant differences in mean gastric pH values were observed at all time points, i.e., (1) before skin incision (2.2 ± 0.2; p = 0.50), (2) after baseline calibration of CIONM probe (2.0 ± 0.8; p = 0.62), (3) +20 min from baseline (2.5 ± 0.5; p = 0.24), (4) before probe removal (2.9 ± 0.9; p = 0.52), and (5) after extubation (2.6 ± 1.0; p = 0.60). Comparisons of pH monitoring parameters revealed no significant differences in age, gender, side of CIONM (left vs. right), sequence of CIONM, or duration of CIONM. Gastrin values were normal in sequential determinations and did not significantly differ at any time points., Conclusions: CIONM performed via VN stimulation during total thyroidectomy in healthy patients does not influence gastrin secretion and gastric pH.

The objective is to compare the consequences of routine visualization (RV) and the application of intermitted (I-IONM), standardized (S-IONM), and continuous monitoring (C-IONM) of recurrent laryngeal nerve (RLN) management. RV includes that 698 RLNs managed solely with visual identification. In a second period 777, RLNs were handled by the I-IONM. The third period 768 RLNs monitoring was performed according to the standards. C-IONM via VN stimulation included 626 RLNs. The following issues were analyzed and compared per each period study: RLN identification rate, branching detection, assessment of NRLN, intraoperative recognizable nerve damage, stage thyroidectomy rate, transient or definitive lesions, bilateral nerve palsy, and recovery time. Significance for nerve identification rate was achieved (p = 0.03) when the statistical analysis was applied between RV vs. S-IONM and C-IONM. Extralaryngeal bifurcation was identified in 21, 44, 43, and 46 of RLN dissected, respectively, per period (p = 0.005). The incidence of paralysis in identified and unidentified RLN was 3.8 % (107/2806) and 82 % (52/63), respectively. Rates of temporary/permanent RLNP were 16.7/1.7, 5/1.1, 4.5/1, and 3.1/0 % per period study, respectively (p = 0.07). Recognizable intraoperatively nerve damage was, respectively, 15, 45, 100, and 100 % for period study (p = 0.03). The recovery of injured nerves was significantly faster in C-IONM group. S-IONM and C-IONM cumulate 40-stage procedures. The standardized technique, guidelines adherences, and C-IONM allowed to (1) increase RLN identification; (2) reduce the severity of injuries in terms of (a) reset bilateral RLNP, (b) faster recovery time, and, ((c) lower definitive RLNP; (3) gather detection of branching and NRLN; (4) recognize nerve stress; and (5) cumulate stage procedures.)

Objectives/hypothesis: Intraoperative neuromonitoring identifies recurrent laryngeal nerve (RLN) injury and gives prognostic information regarding postoperative glottic function. Loss of the neuromonitoring signal (LOS) signifies segmental type 1 or global type 2 RLN injury. This study aimed at identifying risk factors for RLN injury and determining vocal fold (VF) function initially and 6 months after definitive LOS., Study Design: Prospective study encompassing 21 hospitals from 13 countries., Methods: Included in this study were patients with persistent intraoperative LOS., Results: At first postoperative laryngoscopy, early VF palsy was present in 94 of all 115 patients with LOS (81.7%): in 53 of 56 patients (94.6%) with type 1 injury and 41 of 59 patients (69.5%) with type 2 injury. In LOS type 1, women outnumbered men >5-fold. Traction produced LOS type 1 in 38 of 56 patients (67.9%) and LOS type 2 in 54 of 59 patients (91.5%). Course of the RLN posterior and/or anterior to the inferior thyroid artery, extralaryngeal branching, or tuberculum of Zuckerkandl did not increase VF palsy rates. Permanent VF palsy rates were also lower (P = .661) after LOS type 2 than after LOS type 1: 6.8% (four of 59 patients) versus 10.7% (six of 56 patients). Intraoperative administration of steroids did not diminish postoperative VF palsy rates., Conclusions: LOS type 1 entails more severe nerve damage than LOS type 2, affecting women disproportionately. Both LOS types, being primarily associated with traction injury, are unaffected by variant neck anatomy in expert hands and unresponsive to steroids., Level of Evidence: 2b Laryngoscope, 126:1260-1266, 2016., (© 2015 The American Laryngological, Rhinological and Otological Society, Inc.)

Objectives/hypothesis: The use of neuromuscular blocking agent may effect intraoperative neuromonitoring (IONM) during thyroid surgery. An enhanced neuromuscular-blockade (NMB) recovery protocol was investigated in a porcine model and subsequently clinically applied during human thyroid neural monitoring surgery., Study Design: Prospective animal and retrospective clinical study., Methods: In the animal experiment, 12 piglets were injected with rocuronium 0.6 mg/kg and randomly allocated to receive normal saline, sugammadex 2 mg/kg, or sugammadex 4 mg/kg to compare the recovery of laryngeal electromyography (EMG). In a subsequent clinical application study, 50 patients who underwent thyroidectomy with IONM followed an enhanced NMB recovery protocol-rocuronium 0.6 mg/kg at anesthesia induction and sugammadex 2 mg/kg at the operation start. The train-of-four (TOF) ratio was used for continuous quantitative monitoring of neuromuscular transmission., Results: In our porcine model, it took 49 ± 15, 13.2 ± 5.6, and 4.2 ± 1.5 minutes for the 80% recovery of laryngeal EMG after injection of saline, sugammadex 2 mg/kg, and sugammadex 4 mg/kg, respectively. In subsequent clinical human application, the TOF ratio recovered from 0 to >0.9 within 5 minutes after administration of sugammadex 2 mg/kg at the operation start. All patients had positive and high EMG amplitude at the early stage of the operation, and intubation was without difficulty in 96% of patients., Conclusions: Both porcine modeling and clinical human application demonstrated that sugammadex 2 mg/kg allows effective and rapid restoration of neuromuscular function suppressed by rocuronium. Implementation of this enhanced NMB recovery protocol assures optimal conditions for tracheal intubation as well as IONM in thyroid surgery., Level of Evidence: NA., (© 2016 The American Laryngological, Rhinological and Otological Society, Inc.)

Background: Recurrent laryngeal nerve (RLN) palsy is the most serious complication after thyroidectomy. However, little is known about the degree of traction injury that causes loss of signal. The purpose of this study was to evaluate traction injuries in the swine RLN using continuous intraoperative neuromonitoring (IONM) and determine the traction power that results in loss of signal., Methods: Thirteen swine underwent traction injury to the RLNs with continuous IONM, and stress-strain curves were determined for 8 nerves using the universal material testing machine in an ex vivo model., Results: Traction injury at a mean power of 2.83 MPa caused loss of signal. The mean physiologic limit strain and tensile strength of the swine RLNs were found to be 15.0% and 4.9 MPa, respectively. Histological analysis showed no abnormal structural findings., Conclusion: Traction injury of swine RLNs causes loss of signal at a power of 2.83 MPa. However, all injured nerves recovered within 7 days with no observed structural damage., (© 2015 Wiley Periodicals, Inc.)

Objectives/hypothesis: During intraoperative neuromonitoring (IONM) of recurrent laryngeal nerve (RLN) in thyroid surgery, the need for frequent shifting between the dissecting instruments and stimulating probe is troublesome and time-consuming. Therefore, use of these two instruments in combination would be a noticeable future direction. This study aimed to investigate the feasibility and safety of using stimulating dissecting instruments (SDIs) that combine the function of surgical dissection and nerve stimulation during IONM., Study Design: Prospective outcomes research., Methods: One hundred consecutive patients with 168 RLNs at risk were enrolled. We developed prototypes of SDIs and applied them to early detect adverse EMG changes during the risky phase of RLN dissection. In the case of substantial EMG change (amplitude decrease > 50%) during dissection, the surgical maneuver was paused and thyroid traction was released immediately., Results: The application of SDIs was feasible in all cases and did not result in any morbidity. Nineteen RLNs were detected with substantial EMG change that was caused by traction stress during dissection with SDIs and that featured progressive gradual EMG recovery after releasing thyroid traction. After thyroid resection, 10 RLNs had a weak point of nerve conduction detected at region of Berry's ligament, but only one nerve with 79% amplitude reduction developed postoperative temporary vocal palsy., Conclusion: The application of SDIs is a simple and effective way to monitor the nerve's function instantly during the risky phase of RLN injury in thyroid surgery. It provides surgeons with real-time feedback of EMG response and can be applied as a tool for the early detection of adverse EMG change caused by traction distress., Level of Evidence: 4., (© 2015 The American Laryngological, Rhinological and Otological Society, Inc.)

Objectives/hypothesis: The Harmonic Focus (HF) is one of the most popular energy-based devices. The aim of this study was to provide recurrent laryngeal nerve (RLN) functional data that define the safety parameters of the HF during thyroidectomy., Study Design: Prospective porcine model using continuous electrophysiologic monitoring., Methods: Ten piglets were used. At varying distances from the RLN, the HF was activated (activation study). The HF was also applied directly on the RLN after activation on sternocleidomastoid muscle for 10 seconds with different cooling times (cooling study)., Results: In the activation study, there was no adverse electromyography (EMG) event at more than 1 mm distance. In the cooling study, there was no adverse EMG event after a 10-second cooling period. When the HF was cooled on the sternocleidomastoid muscle, there was no adverse EMG event after 2 seconds cooling time., Conclusions: The safe distance of the HF was 1 mm, and it should be cooled for more than 10 seconds or 2 seconds after cooling on muscle. The HF should be used in a standardized manner to avoid RLN injury., Level of Evidence: NA., (© 2015 The American Laryngological, Rhinological and Otological Society, Inc.)

Background: Vagal nerve stimulation (VNS) has been recommended as a routine procedure during intraoperative neuromonitoring (IONM) of the recurrent laryngeal nerve (RLN). However, many surgeons have been discouraged from performing VNS because of the need for opening the carotid sheath. The purpose of this study was to investigate the feasibility and reliability of VNS without carotid sheath dissection., Methods: Two hundred twenty patients with 376 nerves at risk were enrolled in this study. VNS without nerve exposure during IONM was applied by simply pressing a ball-tip stimulator on the space between the carotid artery and jugular vein., Results: VNS without nerve exposure was feasible in all cases and did not result in any morbidity. All VNS signals were successfully obtained within 30 minutes of the start of the operation and all showed a clear and reliable laryngeal electromyography (EMG) response that was similar to that from the conventional method in which nerve exposure for VNS is applied., Conclusions: VNS without dissecting the carotid sheath is feasible and reliable, rendering it a simple, safe, and surgeon-friendly procedure during IONM., (Copyright © 2013 Wiley Periodicals, Inc.)

Standardization of the intraoperative neuromonitoring (IONM) technique is an essential aspect of modern monitored thyroid surgery. The standardized technique involves vagal nerve stimulation. VN stimulation is useful for technical problem solving, detecting non-recurrent laryngeal nerve (non-RLN), recognizing any recurrent laryngeal nerve (RLN) lesions, and precisely predicting RLN postoperative function. Herein, we present technical notes for the VN identification to achieve the critical view of safety of the VN stimulation with or without dissection.

Purpose: The nonrecurrent laryngeal nerve (NRLN) is a rare anatomical variant but associated with high risk of nerve injury during thyroid and parathyroid operations. Therefore, intraoperative detection and verification of NRLN are necessary., Method: A total of 390 consecutive patients who underwent thyroid and parathyroid operations (310 RLNs dissected on the right side and 293 nerves on the left side) were enrolled. Electrically evoked electromyography was recorded from the vocalis muscles via an endotracheal tube with glottis surface recording electrodes. At an early stage of operation, vagal nerve was routinely stimulated at the level of inferior thyroid pole to ensure normal path of RLN. If there is a negative response from lower position but positive response from upper vagal stimulation, it indicates the occurrence of a NRLN, and we localize its separation point and path., Results: Four right NRLNs (1.3%) without preoperative recognition were successfully detected at an early stage of operation. Three patients were operated on for thyroid disease, one for parathyroid adenoma and all were associated with right aberrant subclavian artery. All NRLNs were localized and identified precisely with intraoperative neuromonitoring. Functional integrity of all nerves was confirmed by the intraoperative neuromonitoring and postoperative laryngeal examination., Conclusions: Vagal stimulation at the early stage of operation is a simple, useful, and reliable procedure to detect and identify the NRLN., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Purpose: Extensive dissection of recurrent laryngeal nerve (RLN) is inevitable in some complicated thyroid operations. The study aimed to determine whether extensive dissection of RLN increases the risk of nerve injury., Method: Three hundred thirty-one patients (506 nerves at risk) who underwent thyroid operations with intraoperative neuromonitoring were included. The study chiefly focused on the 101 RLNs on which extensive nerve dissection from the thoracic inlet to the entry of larynx was performed and for which the nerve exposure was longer than 5 cm. Electromyographic (EMG) signals were obtained from the RLN and vagus nerve before and after complete RLN dissection, and these were defined as R(1), V(1) and R(2), V(2) signals, respectively. The RLN palsy rates and the change of EMG signals were evaluated and analyzed., Results: Among 101 nerves with extensive dissection, 13 nerves were due to the operation for recurrent goiter; 41 nerves, for large goiter with substernal extension; and 47 nerves, for thyroid cancer with paratracheal nodal metastasis. No permanent palsy occurred, but 2 nerves experienced loss of EMG signal after complete RLN dissection from a large recurrent goiter and developed temporary palsy. The palsy rates were 2% (2/101) in the extensive dissection group and 2.5% (10/405) in the nonextensive dissection group (P = .77). Among 99 nerves with normal vocal function after operation, none experienced weakened signal after complete RLN dissection, and the mean amplitudes of R(2) and V(2) signals were not significantly different from those of R(1) and V(1) signals (R(2) vs R(1); 1038 vs 1030 μV; P = .74; V(2) vs V(1); 824 vs 816 μV; P = .75)., Conclusions: The results of this study suggest that careful surgical dissection is well tolerated by the RLN., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Background: The goal of this study was to explore an ideal application of rocuronium to enable adequate muscle relaxation for intubation without significantly affecting the evoked potentials measured by intraoperative neuromonitoring during thyroid surgery., Methods: A total of 80 patients were randomized to receive 1 (group 1, n = 40) or 2 (group 2, n = 40) effective doses (ED(95)) of rocuronium to facilitate electromyographic (EMG) endotracheal tube insertion. Evoked potentials were obtained every 5 minutes by stimulating the vagus nerve between the time period of 30 and 70 minutes after administration of rocuronium. The magnitude of evoked potentials at each time point and the tracheal intubating conditions were compared between groups. Accelerometry (twitch [% TW]) was used to monitor the quantitative degree of neuromuscular transmission at the adductor pollicis muscle., Results: At 30 minutes after administration of rocuronium, the rate of positive EMG response was 100% (40/40) in group 1 and 53% (21/40) in group 2 (P < .001). Positive EMG signals were obtained for all patients in group 2 until 55 minutes after administration of rocuronium. The mean amplitude detected from the time point of 30 to 60 minutes was greater in group 1 than in group 2 (P < .01). The time to tracheal intubation was 208 ± 59 seconds in group 1 and 114 ± 26 seconds in group 2 (P < .001). The overall intubating conditions were better in group 2 than in group 1 patients (P < .001)., Conclusion: A total of 1 ED(95) of rocuronium (0.3 mg/kg) is an optimal dose for intraoperative neuromonitoring during thyroid surgery. Positive and high EMG signals were obtained in all patients at an early stage of operation, and satisfactory intubating conditions were achieved in most patients., (Copyright © 2011 Mosby, Inc. All rights reserved.)

Early and definite identification of the recurrent laryngeal nerve (RLN) is an important step to avoid inadvertent nerve injury during complicated thyroid operations. This study aimed to determine the feasibility of routine use of intraoperative neuromonitoring (IONM) to localize and identify the RLN at an early stage of thyroid surgery. This prospective study enrolled 220 consecutive patients (333 RLNs at risk) who underwent thyroid operations with application of IONM. The RLN was localized and identified routinely with a nerve stimulator after opening the space between the thyroid and carotid sheath. The success rates of early RLN localization and identification were evaluated. The current for localization and the amplitude of evoked laryngeal electromyographic signals were also recorded and analyzed. All RLNs, including 87 (26%) nerves that were regarded as difficult to identify, were successfully localized and identified. The stimulation level for RLN localization was 2mA in 315 nerves (95%) and 3mA in the other 18 nerves (5%). The signal obtained from RLN localization (amplitude = 932 ±436μV) showed a clear and reliable laryngeal electromyographic response that was similar to that from direct vagus (amplitude=811±389μV) or RLN stimulation (amplitude=1132±472μV). The palsy rate was 0.6% and no permanent palsy occurred. RLN injury is rare if the nerve is definitely identified early in the thyroid operation. The conclusion of this study is that IONM is a reliable tool for early RLN localization and identification, even in complicated thyroid operations., (Copyright © 2010 Elsevier. Published by Elsevier B.V. All rights reserved.)

Recurrent laryngeal nerve (RLN) palsy is the most common and serious complication after thyroid surgery. Visual identification of the RLN during thyroid surgery has been shown to be associated with lower rates of palsy, and although it has been recommended as the gold standard for RLN treatment, it does not guarantee success against postoperative vocal cord paralysis. Anatomical variations of the RLN, such as extra-laryngeal branches, distorted RLN, intertwining between branches of the RLN and inferior thyroid artery, and non-recurrent laryngeal nerve, can be a potential cause of nerve injury due to visual misidentification. Therefore, intraoperative verification of functional and anatomical RLN integrity is a prerequisite for a safe thyroid operation. In this article, we review the literature and demonstrate how to identify and handle the anatomical variations of the RLN with the application of intraoperative neuromonitoring in the form of high resolution photography, which can be informative for thyroid surgeons. Anatomical variations of the RLN cannot be predicted preoperatively and might be associated with higher rates of RLN injury. The RLN injury caused by visual misidentification can be rare if the nerve is definitely identified early with intraoperative neuromonitoring., (Copyright © 2010 Elsevier. Published by Elsevier B.V. All rights reserved.)

Background: Standardisation of the intraoperative neuromonitoring (IONM) technique is a fundamental aspect in monitored thyroid surgery. Vagal nerve (VN) stimulation is essential for problem solving, recognition of any inferior laryngeal nerve (ILN) lesions and prediction of ILN post-operative function. Issues that have been overlooked in the literature, particularly in terms of prospective approaches, are the topographic relationship of the VN with the carotid and jugular vessels as well as the neurophysiology of the VN and ILN that have been studied, with a prospective approach, in patients with various thyroid diseases., Methods: Cooperation with the Human Morphology Department resulted in the completion of a dedicated anatomy report, with the clear objective of providing a detailed anatomic and neurophysiologic description of the VN (n = 263)., Results: VN identification and stimulation was feasible in all cases and did not result in increased morbidity or operative time. Most VNs lay on the posterior region of the carotid ship (73%), i.e. the P position in accordance with our model. Mean amplitudes of EMG signals obtained from VN stimulation were 750 ± 279 μV, lower than those obtained with direct INL stimulation (1,086 ± 349 μV)., Conclusion: A better understanding of the variability in the VN may be useful not only to minimise complications but also to guarantee an accurate IONM.

Objective: The objective of this study was to find a nondepolarizing muscle relaxant to replace succinylcholine during thyroid surgery with intraoperative neuromonitoring (IONM) because succinylcholine can cause severe adverse effects., Design: Prospective study of 232 patients undergoing thyroidectomies., Setting: A tertiary medical centre., Methods: One hundred thirty-one patients received 0.5 mg/kg rocuronium (group R) and 101 patients received 0.5 mg/kg atracurium (group A) to facilitate electromyographic (EMG) endotracheal tube insertion. EMG signals were obtained from the vagus nerve before and after dissection of the recurrent laryngeal nerve and were defined as the V1 and the V2 signal, respectively. Accelerometry (twitch [% TW]) was used to monitor the quantitative degree of neuromuscular transmission at the adductor pollicis muscle., Main Outcome Measures: The amplitude (muV) of the V1 and V2 signals and the correlated degree of neuromuscular transmission (% TW)., Results: V1 and V2 signals were obtained from all patients successfully. The % TW at the V1 signal was significantly lower than that at the V2 signal in group R and group A. The mean recovery time from complete neuromuscular blockade to the initial twitch was 43.9 +/- 11 minutes. Only in the subgroup in which the correlated TW was 0% while eliciting the V1 signal were the amplitudes of the V1 signals significantly lower than those of the V2 signal in both groups., Conclusions: A single dose (0.5 mg/kg) of rocuronium and atracurium was feasible for IONM during thyroid surgery. This study showed that 44 minutes after administration of these two muscle relaxants is adequate for eliciting an EMG signal from the vagus nerve.

Background: The lack of standardized procedures of intraoperative neuromonitoring (IONM) during thyroid operations may lead to highly variable results, and many of these results can cause misleading information and, conversely, increase the risk of recurrent laryngeal nerve (RLN) injury. Therefore, standardization of IONM procedures is necessary., Methods: A total of 289 patients (435 nerves at risk) who underwent thyroidectomy by the same surgeon were enrolled in this study. Each patient was intubated with EMG endotracheal tube by the same anesthesiologist. Standardized IONM procedures were applied in each patient. The procedures include preoperative and postoperative video-recording of vocal cord movement, ensuring the correct position of electrodes after the neck was placed at full extension, vagal stimulation and registration of EMG signals before and after RLN dissection, and photographic documentation of the exposed RLN., Results: Five patients encountered dysfunction of IONM, which was caused by malposition of electrodes and the problem was detected at once. One patient with non-RLN was detected at the earlier stage of operation. Eighteen nerves experienced loss of EMG signals during thyroid dissection, and the causes of nerve injuries were well elucidated with the application of our standardized IONM procedures., Conclusions: The standardized IONM procedures are useful and helpful not only to eliminate false IONM results, but also to elucidate the mechanism of RLN injury. After ascertaining the surgical pitfalls and improving the surgical techniques, the palsy rate was significantly reduced in this study.

Background: A short-acting depolarizing neuromuscular blocking agent (NMBA), succinylcholine, has been utilized for thyroid operations with intraoperative neuromonitoring (IONM). Because of its potential to cause serious side effects, this prospective study tried to determine the feasibility of IONM after administration of a nondepolarizing NMBA during thyroid operations., Methods: Complete IONM data for 179 patients who had normal cord mobility were investigated: 90 patients received an induction dose of rocuronium (group R) and 89 received atracurium (group A). Electromyography signals were obtained from the vagus nerve before and after resection of the thyroid lobe and were defined as V(1) and V(2) signals, respectively. Accelerometry (percent twitch) was used to monitor the quantitative degree of neuromuscular blockade., Results: V(1) and V(2) signals were obtained successfully in all patients. The percent twitch at the V(1) signal was significantly lower than that at the V(2) signal in both groups (39% +/- 20% vs. 69% +/- 26% in group R; 35% +/- 28% vs. 56% +/- 35 % in group A; both p < 0.01). However, the magnitude of the V(1) and V(2) signals did not differ significantly in either in group (473.8 +/- 290.8 microV vs. 528 +/- 316.2 microV in group R; 584.8 +/- 394.3 microV vs. 637.8 +/- 458.2 microV in group A; both p > 0.05)., Conclusions: A single dose of either rocuronium or atracurium was feasible for IONM during thyroid surgery and provided adequate muscle relaxation for tracheal intubation.

Background: Malpositioning of the endotracheal surface electrodes can result in dysfunction of intraoperative neuromonitoring (IONM) and increase the risk of recurrent laryngeal nerve injury. The purpose of this study was to investigate the optimal depth of the nerve integrity monitor (NIM) EMG endotracheal tube., Methods: We enrolled 105 adult patients undergoing elective thyroidectomy. Each Medtronic Xomed NIM EMG endotracheal tube was placed with the middle of the exposed electrodes well in contact with the true vocal cords under direct laryngoscopy. Function of IONM was documented and the insertion depth was measured and analyzed., Results: Ninety-nine (94.3%) patients had successful IONM with the initial endotracheal tube position. Six (5.7%) patients needed further tube depth adjustment under fiberoptic bronchoscopy. All patients were finally had successful IONM. The optimal mean depth was 20.6 +/- 0.97 cm in men and 19.6 +/- 1.0 cm in women (p < 0.01). There was the trend that taller subjects had a deeper tube depth (p < 0.05)., Conclusion: We concluded that the mean depth of the NIM EMG tube would be a useful reference value for detecting the malposition of electrodes and adjusting the depth of tube during the operation.

Background: Identification of recurrent laryngeal nerve (RLN) has decreased the rates of permanent RLN palsy during thyroid operations; however, unexpected RLN palsy still occurs, even though the visual integrity was assured and most nerve injuries were not recognized intraoperatively. The aim of this study is to determine the causes of RLN palsy and to identify potentially reversible causes of RLN injury during the operation with the application of intraoperative neuromonitoring (IONM)., Methods: One hundred and thirteen patients with 173 nerves at risk were enrolled in this study. All operations were performed by the same surgeon. The 4-step procedure of IONM was designed to obtain electromagnetic (EMG) signals from the vagus nerve and RLN before and after resection of thyroid lobe., Results: Sixteen nerves had loss of EMG signals after thyroid dissection, and the causes of nerve injuries were well elucidated with the application of IONM. One nerve injury was caused by inadvertent transection, which led to permanent RLN palsy. Among the remaining 15 nerves, 1 injury was caused by a constricting band of connective tissue, which was detected precisely and released intraoperatively, 2 by inadvertent clamping of the nerve, and 12 by apparent overstretching at the region of Berry's ligament. (Five nerves regained signals before closing the wound, but 1 showed impaired cord movement. Another 7 nerves did not regain signals before closing the wound, and all developed temporary RLN palsy.), Conclusions: Our 4-step procedure of IONM is useful and helpful in elucidating the potential operative pitfalls during dissection near the RLN. Although the rates of RLN palsy were not decreased in this study, the use of neuromonitoring provided instructive information for future operations by ascertaining where and how the RLN has been injured.