Recurrent laryngeal nerve injury in video-assisted thyroidectomy: lessons learned from neuromonitoring

Standardized Intraoperative Neuromonitoring Procedure is Feasible in Transoral Endoscopic Thyroidectomy

BACKGROUND

Intraoperative neuromonitoring in thyroid surgeries has become popular, but the standardized manner of intraoperative neuromonitoring during transoral endoscopic thyroidectomy vestibular approach (TOETVA) is not well established. This study evaluated the feasibility of using a standardized intraoperative neuromonitoring method for TOETVA.

METHODS

Medical records of consecutive patients who underwent TOETVA with intraoperative neuromonitoring were retrospectively reviewed. Patients were positioned before intubation to prevent tube migration, then intubated using video laryngoscopy. The electromyography amplitudes of the vagal nerves and the recurrent laryngeal nerves were checked before (V1, R1) and after (V2, R2) thyroid resection. V1 and V2 signals were evaluated using a long ball tip stimulator with a stimulus current of 3 mA. R1 and R2 signals were obtained using the stimulus current of 1 to 3 mA.

RESULTS

Forty-two patients (3 males and 39 females) were included. Lobectomy was performed in 40 patients (95.2%) and total thyroidectomy in 2 (4.8%). Pathologic diagnoses were 30 papillary thyroid carcinomas, 2 follicular thyroid carcinomas, and 9 benign diseases. Conversion to open surgery occurred in 1 patient due to bleeding. Thus, 43 nerves at risk in 41 patients were analyzed. V1 and R1 signals were detected from all nerves. The mean V1 and R1 amplitudes were 738.7±391.4 μV and 804.4±347.5 μV, respectively, and 38 (88.3%) and 39 (90.7%) nerves had R1 and V1 amplitudes of more than 500 μV. There were 2 cases (4.6%) of transient recurrent laryngeal nerve injury. R2 and V2 signals were detected in the 41 remaining nerves. The mean R2 and V2 amplitudes were 917.2±505.2 μV and 715.7±356.2 μV, respectively, and 36 (87.8%) and 32 (78.0%) nerves had respective R2 and V2 amplitudes of more than 500 μV.

CONCLUSIONS

Intraoperative neuromonitoring could be performed in a standardized manner in TOETVA, and the quality of intraoperative neuromonitoring was excellent. Further studies are needed to verify the feasibility of the current approach.

Surgical Significance of Berry’s Posterolateral Ligament and Frequency of Recurrent Laryngeal Nerve Injury into the Last 2 cm of Its Caudal Extralaryngeal Part(P1) during Thyroidectomy

Background and Objectives: Recurrent laryngeal nerve injury is one of the major complications of thyroidectomy, with the lateral thyroid ligament (Berry’s ligament) being the most frequent site of nerve injury. Neuromonitoring during thyroidectomy revealed three possible anatomical regions of the recurrent laryngeal nerve P1, P2, and P3. P1 represents the recurrent laryngeal nerve’s caudal extralaryngeal part and is primarily associated with Berry’s ligament. The aim of this systematic review is to identify the anatomical region with the highest risk of injury of the recurrent laryngeal nerve (detected via neuromonitoring) during thyroidectomy and to demonstrate the significance of Berry’s ligament as an anatomical structure for the perioperative recognition and protection of the nerve. Materials and Methods: This study conducts a systematic review of the literature and adheres to all PRISMA system criteria as well as recommendations for systematic anatomical reviews. Three search engines (PubMed, Scopus, Cochrane) were used, and 18 out of 464 studies from 2003–2018 were finally included in this meta-analysis. All statistical data analyses were performed via SPSS 25 and Microsoft Office XL software. Results: 9191 nerves at risk were identified. In 75% of cases, the recurrent laryngeal nerve is located superficially to the ligament. In 71% of reported cases, the injury occurred in the P1 area, while the P3 zone (below the location where the nerve crosses the inferior thyroid artery) had the lowest risk of injury. Data from P1, P2, and P3 do not present significant heterogeneity. Conclusions: Berry’s ligament constitutes a reliable anatomical structure for recognizing and preserving recurrent laryngeal nerves. P1 is the anatomical area with the greatest risk of recurrent laryngeal nerve damage during thyroidectomy, compared to P2 and P3.

Improving Voice Outcomes after Thyroid Surgery and Ultrasound-Guided Ablation Procedures

The field of endocrine surgery has expanded from the traditional open neck approach to include remote access techniques as well as minimally invasive approaches for benign and malignant thyroid nodules. In experienced hands and with careful patient selection, each approach is considered safe, however complications can and do exist. Post-operative dysphonia can have serious consequences to the patient by affecting quality of life and ability to function at work and in daily life. Given the significance of post-procedural dysphonia, we review the surgical and non-surgical techniques for minimizing and treating recurrent laryngeal nerve injury that can be utilized with the traditional open neck approach, remote access thyroidectomy, or minimally invasive thermal ablation.

Importance of Intraoperative Neuromonitoring Parameters in Predicting Temporary Recurrent Laryngeal Nerve Palsy Following Thyroid Surgery for Malignancy

Recurrent laryngeal nerve (RLN) palsy is one of the feared complications following thyroid surgery. Intraoperative neuromonitoring (IONM) has been used as an adjunct to reduce this complication. In the present study, we attempted to evaluate the IONM parameters such as latency, current requirement, and baseline amplitude that could predict temporary RLN palsy along with factors that could influence these parameters during thyroid surgery. This was a retrospective study of patients who underwent hemi, total, or completion thyroidectomy for cancer at our institute between June 1, 2017 to May 31, 2019 in whom IONM was used during surgery. The study consisted of 84 consecutive patients with 138 nerves at risk. The RLN palsy rate in our study was 5% (n = 7). Patients with low baseline amplitude and/or requiring higher current to maintain normal baseline amplitude were often associated with temporary RLN palsy. In the multivariate analysis, age > 40 years (p = 0.001, OR = 4.14) influenced the baseline EMG amplitude the most. The intraoperative current management was influenced by advanced pT stage (p = 0.001, OR = 2.87), and structural nerve injury (p = 0.001, OR = 3.15). Patients with low baseline amplitude and/or requiring higher current to maintain normal baseline amplitude were often associated with temporary RLN palsy. Factors such as age, pT stage, and structural nerve injury influenced the IONM stimulation and recording parameters.

Safety Parameters of Quantum Molecular Resonance Devices During Thyroid Surgery: Porcine Model Using Continuous Neuromonitoring

OBJECTIVES

Quantum molecular resonance (QMR) devices have been applied as energy-based devices in many head and neck surgeries; however, research on their use in thyroid surgery is lacking. This study aimed to investigate the safety parameters of QMR devices during thyroidectomy when dissection was adjacent to the recurrent laryngeal nerve (RLN).

METHODS

This study included eight piglets with 16 RLNs, and real-time electromyography (EMG) signals were obtained from continuous intraoperative neuromonitoring (C-IONM). QMR bipolar scissor (BS) and monopolar unit (MU) were tested for safety parameters. In the activation study, QMR devices were activated at varying distances from the RLN. In the cooling study, QMR devices were cooled for varying time intervals, with or without muscle touch maneuver (MTM) before contacting with the RLN.

RESULTS

In the activation study, no adverse EMG change occurred when QMR BS and MU were activated at distances of 2 mm or longer from the RLNs. In the cooling study, no adverse EMG change occurred when QMR BS and MU were cooled in 2-second intervals or immediately after MTM.

CONCLUSION

QMR devices should be carefully used when performing RLN dissection during thyroid surgery. According to the activation and cooling safety parameters in this study, surgeons can avoid RLN injury by following standard procedures when using QMR devices.

Clarifying optimal outcome measures in intermittent and continuous laryngeal neuromonitoring

BACKGROUND

Intraoperative neuromonitoring (IONM) techniques have evolved over the past decade into intermittent IONM (I-IONM) and continuous IONM (C-IONM) modes of application. Despite many prior publications on both types of IONM, there remains uncertainty about what outcomes should be measured for each form of IONM. The primary objective of this paper is to define categories of benefit for I-IONM/C-IONM and to clarify and standardize their reporting outcomes.

METHODS

Expert review consensus statement utilizing modified Delphi methodology.

RESULTS

I-IONM provides diagnosis, classification, and prevention of nerve injury through accurate and early nerve identification. C-IONM provides real-time information on nerve functional integrity and thus may prevent some types of nerve injury but cannot assist in nerve localization. Sudden mechanisms of nerve injury cannot be predicted or prevented by either technique.

CONCLUSIONS

I-IONM and C-IONM are complementary techniques. Future studies evaluating the utility of IONM should focus on outcomes that are appropriate to the type of IONM being utilized.

Improving Voice Outcomes After Thyroid Surgery - Review of Safety Parameters for Using Energy-Based Devices Near the Recurrent Laryngeal Nerve

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.

Efficacy of Intraoperative Recurrent Laryngeal Nerve Monitoring During Thoracoscopic Esophagectomy for Esophageal Cancer: A Systematic Review and Meta-Analysis

Background: Recurrent laryngeal nerve paralysis (RLNP), a severe complication of mini-invasive esophagectomy, usually occurs during lymphadenectomy adjacent to recurrent laryngeal nerve. This systematic review and meta-analysis aimed to evaluate the efficacy of intraoperative nerve monitoring (IONM) in reducing RLNP incidence during mini-invasive esophagectomy. Methods: Systematic literature search of PubMed, EMBASE, EBSCO, Web of Knowledge, and Cochrane Library until June 4, 2021 was performed using the terms "(nerve monitoring) OR neuromonitoring OR neural monitoring OR recurrent laryngeal nerve AND (esophagectomy OR esophageal)." Primary outcome was postoperative RLNP incidence. Secondary outcomes were sensitivity, specificity, and positive and negative predictive values for IONM; complications after esophagectomy; number of dissected lymph nodes; operation time; and length of hospital stay. Results: Among 2,330 studies, five studies comprising 509 patients were eligible for final analysis. The RLNP incidence was significantly lower (odds ratio [OR] 0.33, 95% confidence interval [CI] 0.12-0.88, p < 0.05), the number of dissected mediastinal lymph nodes was significantly higher (mean difference 4.30, 95%CI 2.75-5.85, p < 0.001), and the rate of hoarseness was significantly lower (OR 0.14, 95%CI 0.03-0.63, p = 0.01) in the IONM group than in the non-IONM group. The rates of aspiration (OR 0.31, 95%CI 0.06-1.64, p = 0.17), pneumonia (OR 1.08, 95%CI 0.70-1.67, p = 0.71), and operation time (mean difference 7.68, 95%CI -23.60-38.95, p = 0.63) were not significantly different between the two groups. The mean sensitivity, specificity, and positive and negative predictive values for IONM were 53.2% (0-66.7%), 93.7% (54.8-100%), 71.4% (0-100%), and 87.1% (68.0-96.6%), respectively. Conclusion: IONM was a feasible and effective approach to minimize RLNP, improve lymphadenectomy, and reduce hoarseness after thoracoscopic esophagectomy for esophageal cancer, although IONM did not provide significant benefit in reducing aspiration, pneumonia, operation time, and length of hospital stay.

Application of patch stimulator for intraoperative neuromonitoring during thyroid surgery: maximizing surgeon's convenience

Background

Intraoperative neuromonitoring (IONM) is frequently used in thyroid surgery to reduce recurrent laryngeal nerve (RLN) injury by providing the surgeon with real-time feedback on nerve stimulation during dissection. We applied a disposable adhesive patch electrode to a dissecting instrument to transfer electrical stimulation to the dissecting instrument for IONM during thyroid surgery. This study aimed to evaluate the feasibility of using the patch stimulator approach for IONM during thyroid surgery.

Methods

We reviewed the medical records of patients who underwent thyroidectomy using both conventional stimulator and adhesive patch stimulator for IONM. The electromyography (EMG) amplitudes of the vagal and the RLNs before (V1, R1) and after thyroid resection (V2, R2) were alternatively checked with each type of stimulator at the same location of each nerve.

Results

Fifteen consecutive patients (4 males, 11 females) were included in this analysis, and a total of 38 nerves (19 vagus nerves and 19 RLNs) were evaluated. No statistically significant differences were seen in the mean amplitudes evoked by the patch stimulator and the conventional probe stimulator for the V1 signal (825.5±394.6 vs. 821.8±360.9 µV, P=0.954), R1 signal (1,044.8±471.2 vs. 1,039.2±507.4 µV, P=0.898), R2 signal (1,037.8±495.0 vs. 938.2±415.8 µV, P=0.948), or V2 signal (812.5±391.9 vs. 787.3±355.7 µV, P=0.975).

Conclusions

The patch stimulator was safely and effectively used for IONM during thyroid surgery and provided similar nerve monitoring responses as the conventional stimulator. This approach may be used to enhance the surgeon's convenience during thyroid surgery.

Anatomical, Functional, and Dynamic Evidences Obtained by Intraoperative Neuromonitoring Improving the Standards of Thyroidectomy

The use of intraoperative neuromonitoring (IONM) is getting more common in thyroidectomy. The data obtained by the usage of IONM regarding the laryngeal nerves’ anatomy and function have provided important contributions for improving the standards of the thyroidectomy. These evidences obtained through IONM increase the rate of detection and visual identification of recurrent laryngeal nerve (RLN) as well as the detection rate of extralaryngeal branches which are the most common anatomic variations of RLN. IONM helps early identification and preservation of the non-recurrent laryngeal nerve. Crucial knowledge has been acquired regarding the complex innervation pattern of the larynx. Extralaryngeal branches of the RLN may contribute to the motor innervation of the cricothyroid muscle (CTM). Anterior branch of the extralaryngeal branching RLN has always motor function and gives motor branches both to the abductor and adductor muscles. In addition, up to 18% of posterior branches may have adductor and/or abductor motor fibers. In 70–80% of cases, external branch of superior laryngeal nerve (EBSLN) provides motor innervation to the anterior 1/3 of the thyroarytenoid muscle which is the main adductor of the vocal cord through the human communicating nerve. Furthermore, approximately 1/3 of the cases, EBSLN may contribute to the innervation of posterior cricoarytenoid muscle which is the main abductor of ipsilateral vocal cord. RLN and/or EBSLN together with pharyngeal plexus usually contribute to the motor innervation of cricopharyngeal muscle that is the main component of upper esophageal sphincter. Traction trauma is the most common reason of RLN injuries and constitutes of 67–93% of cases. More than 50% of EBSLN injuries are caused by nerve transection. A specific point of injury on RLN can be detected in Type 1 (segmental) injury, however, Type 2 (global) injury is the loss of signal (LOS) throughout ipsilateral vagus-RLN axis and there is no electrophysiologically detectable point of injury. Vocal cord paralysis (VCP) develops in 70–80% of cases when LOS persists or incomplete recovery of signal occurs after waiting for 20 min. In case of complete recovery of signal, VCP is not expected. VCP is temporary in patients with incomplete recovery of signal and permanent VCP is not anticipated. Visual changes may be seen in only 15% of RLN injuries, on the other hand, IONM detects 100% of RLN injuries. IONM can prevent bilateral VCP. Continuous IONM (C-IONM) is a method in which functional integrity of vagus-RLN axis is evaluated in real time and C-IONM is superior to intermittent IONM (I-IONM). During upper pole dissection, IONM makes significant contributions to the visual and functional identification of EBSLN. Routine use of IONM may minimalize the risk of nerve injury. Reduction of amplitude more than 50% on CTM is related with poor voice outcome.

Comparison of stimulating dissector and intermittent stimulating probe for the identification of recurrent laryngeal nerve in reoperative setting

PURPOSE

Recurrent laryngeal nerve (RLN) paralysis is one of the most devastating complications after thyroidectomy. Thyroid reoperation is a great challenge for surgeons due to anatomical distortion and fibrosis and associated with a higher risk of RLN injury. In this study, we aimed to compare stimulating dissector (SD) with intermittent stimulating probe (ISP) in thyroid reoperations. This study is the first one which compares the impact of different nerve stimulating devices in thyroid reoperations.

METHODS

Included in this randomized prospective study were patients who had a bilateral subtotal thyroidectomy and would undergo a completion thyroidectomy due to a diagnosis of thyroid papillary cancer between January 2015 and January 2017. Patients were divided into two groups as SD group and ISP group. Age, sex, nerve amplitudes, latencies, the first identification time of RLN and complications were compared in both groups.

RESULTS

A total of 32 patients, 16 in both groups, were included in the study. The demographics, nerve signal amplitudes and latencies were similar in both groups (p > 0.05). The mean RLN identification time in the SD group was 17.4 ± 4.3 min, which was significantly shorter than those in the ISP group (mean 21.3 ± 3.9) (p = 0.014).

CONCLUSION

The first identification of RLN in the thyroid reoperations was faster with the use of SD than with the use of the ISP. Since the electromyographic amplitudes of RLN and vagus nerve with using SD were similar to the bipolar ISP, SD can be used safely for thyroid reoperations.

Intraoperative neuromonitoring during prone thoracoscopic esophagectomy for esophageal cancer reduces the incidence of recurrent laryngeal nerve palsy: a single-center study

The incidence of recurrent laryngeal nerve palsy (RLNP) following minimally invasive esophagectomy has yet to be satisfactorily reduced. Use of intraoperative neuromonitoring (IONM), specifically of the RLN, during thyroidectomy has been reported to reduce the incidence of RLN injury. We now apply IONM during curative prone thoracoscopic esophagectomy, and we conducted a retrospective study to evaluate the feasibility and efficacy of intermittent monitoring of the RLN during the surgery. The study involved 32 consecutive patients who underwent esophagectomy with radical lymph node dissection for esophageal cancer. The patients were of two groups: an IONM group (n = 17) and a non-IONM group (n = 15). We chiefly strip around the esophagus preserving the membranous structure, which contains the tracheoesophageal artery, lymph nodes, and RLN. In the IONM group patients, we stimulated the RLN and measured the electromyography (EMG) amplitude after dissection, at the dissection starting point and dissection end point on both sides. For the purpose of the study, we compared outcomes between the two groups of patients. IONM was carried out successfully in all 17 patients in the IONM group. The incidence of RLNP was significantly reduced in this group. We found that both RLNs can be identified by mean of IONM easily, immediately, and safely and that the EMG amplitude attenuation rate is particularly useful for predicting RLNP.

Training in intraoperative neuromonitoring of recurrent laryngeal nerves reduces the risk of their injury during thyroid surgery

INTRODUCTION

Even though incidence of recurrent laryngeal nerve palsy (RLNP) is low, it affects importantly the quality of life of patients and remains one of main medicolegal litigation problems in surgery. Intraoperative neuromonitoring (IONM) has become widely accepted tool helping in recurrent laryngeal nerve identification, however no clear association of IONM with RLNP rate has been demonstrated. The aim of our study was to assess whether training in IONM influences rates of RNLP after thyroid surgery as an independent factor.

MATERIAL AND METHODS

We analysed retrospectively 1235 patients who underwent thyroidectomy at the 1st Department of General and Endocrine Surgery, Medical University of Bialystok. Possible risk factors for RLNP were evaluated: application or not of IONM, the extent of surgery or thyroid pathology in correlation with surgeons' experience in IONM (trained or untrained).

RESULTS

There were 2351 nerves at risk (NAR) and 39 RNLP were diagnosed after thyroid surgery (1.66%). Surgeons trained in IONM performed 52.2% of all operations (1200 NAR) with 7 RLNP (0.58%), whereas not-trained had 32 RLNP for 1151 NAR (2.8%; p < 0.001). After 182 thyroidectomies (357 NAR) guided by IONM (14.7%) 3 RLNP were observed (0.84%) vs. 36 palsies per 1994 NAR without IONM (1.81%; p = 0.189). The highest danger of RLNP was reported after reoperations and the lowest after subtotal thyroidectomies. We found no association between thyroid pathology and RLNP rate.

CONCLUSIONS

According to our study training in IONM decreases chances of RLNP especially during total or near total thyroidectomy.

Traction Injury of Recurrent Laryngeal Nerve During Thyroidectomy

BACKGROUND

Loss of the neuromonitoring signal (LOS) during thyroidectomy signifies recurrent laryngeal nerve (RLN) injury, which is one of the common complications, especially by traction injury. Transient intraoperative LOS means spontaneous recovery of nerve function during surgery or within 6-month post-surgery. Few articles discuss intraoperative recovery time and transient LOS, and there is no consensus on the risk factors for RLN traction injury and its recovery course; thus, we wanted to determine the maximum intraoperative recovery time.

MATERIALS AND METHODS

This retrospective study included patients who had undergone thyroidectomies at Tainan National Cheng Kung University Hospital between January 2015 and August 2018. A total of 775 patients (with 1000 nerves at risk) who underwent intermittent intraoperative neuromonitoring during thyroidectomy were included in this study. The LOS nerves were divided into 4 groups based on the LOS subtype and the intraoperative status of the recovery. The postoperative vocal cord function was determined by thyroid ultrasound and/or laryngoscope. All the patients would be followed up postoperatively in 2-3 days, 1 week, 2 weeks, and 4-6 weeks.

RESULTS

LOS occurred in 67 of 775 (8.6%) patients and in 70 of 1000 nerves at risk (7.0%). There were 2 in 70 nerves (2.9%) with LOS type 1 (segmental nerve traction injury) with intraoperative recovery (Group 1), 5 (7.1%) with LOS type 1 without intraoperative recovery (Group 2), 47 (67.1%) with LOS type 2 (global injury) with intraoperative recovery (Group 3), and 16 (22.8%) with LOS type 2 without intraoperative recovery (Group 4). All LOS type 1 (segmental nerve injury) nerves had pathologic lesions near the RLN or vagus nerve, but none had invaded the nerves (p < 0.05). The resolving time intraoperatively in the 2 patients in Group 1 was 5 min and 10 min, respectively. The resolving time intraoperatively in Group 3 was 1-20 min, and the average time was 4.8 min. In Group 2, 3 injured nerves recovered within 6 weeks postoperatively, and 2 nerves in 12 weeks. In Group 4, all the 16 injured nerves recovered within 6 weeks postoperatively.

CONCLUSION

Applying intermittent intraoperative neuromonitoring during thyroidectomy, traction recurrent laryngeal nerve injury still happened in 7.0%. 70% of the injured nerves recovered the function intraoperatively after releasing the traction, and the longest duration of recovery is 20 min.

Recurrent Laryngeal Nerve Morbidity: Lessons from Endoscopic via Bilateral Areola and Open Thyroidectomy Technique

BACKGROUND AND AIM

Elucidating the mechanism of recurrent laryngeal nerve (RLN) injuries through intraoperative electromyographic (EMG) and laryngeal examination approaches may deepen our knowledge regarding its prevention strategies. To date, no studies have been reported on the mechanism of RLN injury caused by endoscopic thyroidectomy via bilateral areola approach (ETBAA).

METHODS

Both intraoperative EMG profiles and postoperative laryngeal examination were used to investigate the mechanisms of RLN injury and compare the safety aspects between ETBAA and open thyroidectomy approach (OTA).

RESULTS

This study examined 1420 nerves at risk. The mean follow-up period was 17 ± 4 (range 6-48) months. The incidence of vocal cord paralysis was 4.1% (59/1420). The number of cases with decreased EMG signals and vocal cord palsy was higher in ETBAA group than in OTA group (P < 0.05). The left RLNs in ETBAA group were at higher risk compared to the right nerves.

CONCLUSIONS

The results of the current study indicate that ETBAA exhibits higher risk of RLN injury. The topic includes a video.

Recurrent laryngeal nerve management in transoral endoscopic thyroidectomy

INTRODUCTION

The mechanism of recurrent laryngeal nerve (RLN) injury was investigated during a TransOral Endoscopic Thyroidectomy Vestibular Approach (TOETVA).

METHODS

The function of 185 nerves at risk (NAR) was recorded with intermitted intraoperative neural monitoring (I-IONM). The RLN electromyography (EMG) was delineated during: (a) a pre-dissection vagal nerve stimulation; (b) a RLN stimulation at initial visualization; (c) at nerve dissection; and (d) at the final verification of the entire RLN route. The location, genesis, segmental or diffuse and the outcomes of RLN injuries were catalogued.

RESULTS

Twelve nerves (6.4%) lost the EMG signal and the incidences of temporary and permanent RLN dysfunction were 5.9% and 0.5%. A disrupted point (type 1 injury) could be identified in 7/12 nerves (58%). Five (42%) nerve injuries were classified as global (type 2). Of the seven type 1 injuries, 3 lesions occurred at the RLN laryngeal entry point during the nerve identification. Four type 1 injuries were at the distal 1 cm of the RLN course and during the early nerve dissection. No proximal (>2 cm) injuries occurred. The mechanisms of the injuries were thermal (58%) during the energy-based device use at the ligament of Berry dissection or at the dividing small branches of the inferior thyroid artery. Two (16%) traction injuries occurred during the early nerve dissection. In 2 cases we could not elucidate the mechanism of RLN injury (16%) and 1 injury (8%) was caused by the connective tissue constricting band of. The thermal RLN lesions had longer recovery times.

CONCLUSIONS

The RLN palsy occurs in TOETVA, even when combined with an endoscopic magnification, IONM, early nerve identification, cranial to caudal dissection and top-down view. The thermal RLN injury was the most frequent cause and all injuries occurred at the distal RLN course.

Drainage Collection After Endoscopic-Assisted Transaxillary Dual-Plane Augmentation Mammaplasty Using Cold or Electrosurgical Separation of Interpectoral Space

BACKGROUND

Endoscopic transaxillary augmentation mammaplasty breast augmentation offers several advantages over other augmentation methods. Nonetheless, this procedure is fraught with some problems, including greater surgical trauma due to the longer separation area. We hypothesized that cold separation of the interpectoral space could reduce surgical injury in comparison to the electrosurgical method. This study aimed to compare the outcomes of endoscopic-assisted transaxillary augmentation mammaplasty using cold separation versus electrosurgical separation of the interpectoral space.

METHODS

In this prospective clinical trial, cold and electrosurgical separation of the interpectoral space were achieved using a separation shovel and monopolar electrotome, respectively. A total of 20 patients who visited our department in Beijing, China, for primary breast augmentation surgeries from October 1, 2017, and May 31, 2018, were included. The primary outcome was total postoperative drainage volume. The secondary outcomes were operative time, daily drainage volume, daily pain as assessed using the visual analogue scale (VAS), and reoperation rate. Quantitative data were compared using independent-samples t test. Chi-square test was used to compare 2 classified indexes.

RESULTS

The total drainage volume was significantly lower in the cold separation group than in the electrosurgical separation group (170.45 ± 75.40 mL vs 281.05 ± 148.43 mL; P = .005). The VAS score on the first postoperative day was significantly lower in the cold separation group than in the electrosurgical separation group (6.45 ± 1.93 vs 7.55 ± 1.43; P = .048). Two (20%) reoperations owing to postoperative pain or implant stiffness were performed in the electrosurgical separation group.

CONCLUSIONS

Cold separation is more conducive to reducing drainage, relieving postoperative pain, and causing less damage than the electrosurgical method in endoscopic-assisted transaxillary dual-plane augmentation mammaplasty.

Resection of a Superior Mediastinal Mature Teratoma Using Intraoperative Neural Monitoring

A 33-year-old woman presented with a right cervical mass. Contrast computed tomography showed a multilocular tumor with a clear border and heterogeneous contents including fat and calcification. The tumor was located adjacent to the vagus and recurrent nerves. To avoid injury of these nerves, we resected the tumor through a median sternotomy and right cervical lateral incision. Intraoperative neural monitoring was performed using an NIM TriVantage EMG tube (Medtronic, Minneapolis, MN). After the surgery, no neuropathy such as hoarseness was recognized. Pathological diagnosis showed a benign mature teratoma. Intraoperative neural monitoring is useful for superior mediastinal surgery around the vagus and recurrent nerves.

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.

Development of a Novel Intraoperative Neuromonitoring System Using a Surface Pressure Sensor to Detect Muscle Movement: A Rabbit Model Study

OBJECTIVES

False-negative or false-positive responses in intraoperative neuromonitoring (IONM) using electromyography (EMG) in thyroid surgery pose a challenge. Therefore, we developed a novel IONM system that uses a surface pressure sensor instead of EMG to detect muscle twitching. This study aimed to investigate the feasibility and safety of a new IONM system using a piezo-electric surface pressure sensor in an experimental animal model.

METHODS

We developed the surface pressure sensor by modifying a commercial piezo-electric sensor. We evaluated the stimulus thresholds to detect muscle movement, as well as the amplitude and latency of the EMG and surface pressure sensor in six sciatic nerves of three rabbits, according to the stimulus intensity.

RESULTS

The surface pressure sensor detected the muscle movements in response to a 0.1 mA stimulation of all six sciatic nerves. There were no differences in the thresholds of stimulus intensity between the surface pressure sensor and EMG recordings to detect muscle movements.

CONCLUSION

It is possible to measure the change in surface pressure by using a piezo-electric surface pressure sensor instead of EMG to detect muscle movement induced by nerve stimulation. The application of IONM using a piezo-electric surface pressure sensor during surgery is noninvasive, safe, and feasible. Measuring muscle twitching to identify the state of the nerves using the novel IONM system can be an alternative to recording of EMG responses.

Comparison of 3-dimensional and 2-dimensional endoscopic thyroid lobectomy via the trans-thoracoareolar approach

Objectives:

To evaluate retrospectively the safety, efficacy, and feasibility of 3-dimensional (3D) endoscopic thyroid lobectomy via a trans-thoracoareolar approach in comparison with the 2-dimensional (2D) approach.

Methods:

We performed a retrospective and cross-sectional analysis of the data of 100 patients who underwent endoscopic thyroid lobectomy via the trans-thoracoareolar approach between January 2014 and November 2016. The patients were classified: into 2 equal groups depending on whether the 3D or 2D endoscopic approach was employed. The 2 groups were compared for various intraoperative and postoperative parameters.

Results:

The values of total operative time, lobectomy time, suture time, and intraoperative blood loss in the 3D endoscopy group were significantly less than those in the 2D endoscopy group. Additionally, the incidence rates of complications in the 3D endoscopy group were significantly less than those in the 2D endoscopy group. However, the groups were similar with regard to the incidence of transient hypocalcemia, subcutaneous congestion, subcutaneous effusion, and cough; postoperative drainage volume; extubation time; postoperative hospitalization time; and total hospitalization expenses.

Conclusions:

Three-dimensional endoscopic thyroid lobectomy required less operative time and entailed a low risk of injury to adjacent structures, without causing any increase in the rate of postoperative complications, indicating that the 3D endoscopic technique was superior to 2D endoscopy.

A comparison study of the transoral and bilateral axillo-breast approaches in robotic thyroidectomy

OBJECTIVES

Transoral robotic thyroidectomy (TORT) is a new remote access approach to avoid cervical incision. The purpose of this study is to compare two approaches used to avoid cervical incision: transoral approach and bilateral axillo-breast approach (BABA) in robotic thyroidectomy.

METHODS

A total of 90 patients were enrolled prospectively between September 2016 and April 2017. The BABA group had 43 and the TORT group had 47 patients, respectively. Parameters including clinicopathologic data, operative time, complications, laboratory data, hospital stay, postoperative pain, and cosmetic satisfaction were analyzed.

RESULTS

Complications were not different among the two groups. The operative time of TORT was longer than BABA until 15 cases of TORT were completed, but there was no difference after that. The Visual Analogue Scale score in TORT was lower than BABA in all the periods. TORT showed a higher cosmetic satisfaction after surgery. There was no infection or permanent mental nerve hypoesthesia in TORT.

CONCLUSION

Our study showed that TORT had less postoperative pain and a greater cosmetic satisfaction than the BABA. There were no significant differences in the postoperative surgical results between the two groups. TORT was comparable to the BABA in outcome with higher cosmetic satisfaction and less pain.

Development of a Novel Detachable Magnetic Nerve Stimulator for Intraoperative Neuromonitoring

BACKGROUND

Recurrent laryngeal nerve (RLN) palsy is a serious complication of thyroid surgery. During intraoperative neuromonitoring (IONM) of the RLN in thyroid surgery, repeated shifting between surgical instruments and the nerve stimulator is cumbersome and time-consuming. Therefore, we developed a simple detachable magnetic nerve stimulator that may be connected to all metallic surgical instruments. This study aimed to investigate the feasibility and efficacy of this detachable magnetic nerve stimulator for IONM in a porcine model and humans.

METHODS

Eight RLNs in four pigs and thirteen in nine patients that underwent thyroidectomy were examined. We developed a detachable nerve stimulator that combined surgical instruments with the nerve-stimulating probe. We evaluated the electromyography (EMG) amplitudes of the RLNs in pigs and patients using conventional nerve probes and surgical instruments with the novel detachable magnetic nerve stimulator attached.

RESULTS

The EMG amplitudes of the eight RLNs in pigs and thirteen in patients were analyzed. The detachable magnetic nerve stimulator was feasible and safe. There was no significant difference in the EMG amplitude between instruments (P = 0.423 in animals, P = 0.446 in humans).

CONCLUSIONS

The application of stimulating dissection using a detachable magnetic nerve stimulator during thyroidectomy with IONM is simple, convenient, and effective. It provides surgeons with real-time feedback of the EMG response during intermittent IONM. We propose that this novel device could be an essential guide for most surgeons, especially for less experienced head and neck surgeons.

Staged Thyroidectomy: A Single Institution Perspective

Background

The increasing use of intraoperative neuromonitoring (IONM) in thyroid surgery has revealed the need to develop new strategies for cases in which a loss of signal (LOS) occurs on the first side of a planned total thyroidectomy.

Objectives

This study reviews the experience of the authors in using IONM for planned total thyroidectomy after LOS on the first thyroid lobe. The aims were to estimate the incidence of LOS on the first side of resection and to compare intraoperative strategies applied after this event.

Materials and Methods

Intermittent IONM was performed with stimulation of both the vagal nerve and the recurrent laryngeal nerve (RLN) (V1, R1, R2, V2). Patients underwent pre- and postoperative laryngoscopy. Before surgery, patients were informed that staged thyroidectomy might be required.

Results

This study analyzed 803 consecutive thyroid procedures. Of these, V2 LOS (<100 mcV) occurred after first lobe exeresis in 23 (2.8%) procedures. The surgical procedure was stopped in 20 cases (ie, staged thyroidectomy was performed). In three cases with malignancy and severe comorbidity (ASA score 3-4), total bilateral thyroidectomy was performed as planned. No cases of bilateral RLN palsy occurred. Postoperative laryngoscopy confirmed RLN palsy in 21 of the 23 cases. All true positive patients received speech therapy. Patients who had false positive LOS (n = 2) or malignancy (n = 8) and patients who were symptomatic (n = 7) received completion thyroidectomy within 6 months. One patient received radioactive iodine therapy for hyperthyroidism. Two patients received follow up.

Conclusions

Neuromonitoring changes the surgical decision-making process in a multidisciplinary manner. A shared decision-making process involving the patient, anesthesiologist, and endocrinologist is suggested. In the case of intraoperative LOS on the first-operated side in a planned total thyroidectomy, the thyroid surgeon essentially has three options for surgery on the contralateral side: 1) Perform staged thyroidectomy. This option is recommended in bilateral goiter, Graves' disease, or low-risk thyroid carcinoma (differentiated or medullary thyroid carcinoma). The aim is to avoid bilateral vocal cord palsy. Two-stage completion surgery is delayed until recovery of ipsilateral nerve function. 2) Perform subtotal resection on the contralateral side ventrally to the RLN plane at a safe distance from the nerve. The aim is to avoid further disease recurrence and revision surgery. 3) Perform total thyroidectomy as planned for advanced thyroid carcinoma (including undifferentiated thyroid carcinoma). The aim is to improve disease control through radioactive iodine therapy, radiation therapy, or target therapy immediately after surgery.

Level of Evidence

4.

Surgical management of the recurrent laryngeal nerve in thyroidectomy: American Head and Neck Society Consensus Statement

"I have noticed in operations of this kind, which I have seen performed by others upon the living, and in a number of excisions, which I have myself performed on the dead body, that most of the difficulty in the separation of the tumor has occurred in the region of these ligaments…. This difficulty, I believe, to be a very frequent source of that accident, which so commonly occurs in removal of goiter, I mean division of the recurrent laryngeal nerve." Sir James Berry (1887).

Laryngeal nerve morbidity in 1.273 central node dissections for thyroid cancer

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.

MIVAT: the last 2 years experience, tips and techniques after more than 10 years

BACKGROUND

Minimally invasive video-assisted thyroidectomy (MIVAT) has been introduced into clinical practice by Miccoli in the late 1990s (Miccoli et al., Am J Surg 181(6):567-570, 2001) and it has become a widespread technique used and welcomed worldwide. In this paper, we present our experience of the last 2 years; we also describe tips and techniques derived from over 460 cases performed in the last 10 years by the same surgical team with the same single operator.

METHODS

In the last 10 years, we did about 460 MIVAT procedures. In the last 2 years, we performed MIVAT on 156 consecutive patients at Sant'Andrea University Hospital of Rome "Sapienza" University. of 156 cases performed, we were able to monitor the follow-up in 110 patients.

RESULTS

On 110 cases, the mean surgical time was 74 ± 7.2 min. In our data, we reported: transitory hypoparathyroidism 11 (10%), definitive hypoparathyroidism 4 (3.60%) (this value is inclusive of patients treated with central neck dissection. The value referred only to MIVAT is 1.05%), 2 (1.81%) transitory monolateral nerve palsy, 16 (14.50%) transitory, and 1 (0.9%) definitive nerve palsy. 4 (3.60%) cases of transitory dysphagia and 0 (0%) cases of definitive dysphagia (Table 4). We also had 1 (0.9%) case of surgical scar infection, 0 (0%) postoperative bleeding, and 2 (1.81%) cases of subcutaneous surgical adhesion. Cosmetic results were: 0 (0%) insufficient, 0 (0%) sufficient, 6 (6.30%) passable, 17 (15.50%) good. and 86 (78.20%) excellent. Conversion rate 0 (0%).

CONCLUSION

MIVAT is a good and safe technique, with similar short-term outcomes and similar costs compared to traditional total thyroidectomy. We hope that the tips and techniques reported in this paper as well as the advices in the use of instruments in MIVAT and open surgery will be useful to improve the skills of young surgeons and make thyroid surgery less invasive.

Comparison of the safety of electrotome, Harmonic scalpel, and LigaSure for management of thyroid surgery

BACKGROUND

Energy-based surgical devices, including electrotome, the Harmonic scalpel, and LigaSure, have been widely applied in thyroid surgery, although a comparison of their safety and efficacy has not been reported yet. In this study, we investigated the feasibility of using hemostatic energy-based surgical devices during thyroid surgery in a canine model.

METHODS

Twenty-four beagle dogs were randomly divided into the following groups: electrotome (30 kW), electrotome (15 kW), the Harmonic scalpel (output level 3), and LigaSure (middle gear). The hemostatic devices were applied on the thyroid surface for 3 seconds and then near the recurrent laryngeal nerve (RLN; distance of 5 mm, 3 mm, or 1 mm) for 3 seconds. Evoked electromyography (EMG) amplitudes were recorded by intraoperative neuromonitoring (IONM). Acute microstructural morphological damage to thyroid tissues and the RLN were evaluated immediately after the procedure by light and electron microscopy.

RESULTS

Electrotome caused a significant decrease in evoked EMG amplitudes when applied at a vertical distance of 1 mm from the RLN, both at 30 kW (1046 ± 404.3 μV vs 153 ± 245.5 μV; p < .001) and 15 kW (1197 ± 589.2 μV vs 986.3 ± 797.3 μV; p = .037), compared with those evoked under normal conditions. Furthermore, distinct acute microstructural morphological changes of the RLNs were observed by light and electron microscopy. However, no significant functional or histological changes were induced by the electrotome at a vertical distance of 5 mm or 3 mm from the RLN. The Harmonic scalpel and LigaSure induced neither marked changes in evoked EMG amplitudes when applied at vertical distances of 5 mm, 3 mm, or 1 mm (all p > .05) nor microstructural morphological changes in the RLNs. The electrotome (15 kW) caused more serious thermal damage to thyroid tissues than that caused by either the Harmonic scalpel or LigaSure (thermal damaged depth: 0.951 ± 0.061 vs 0.756 ± 0.074, p < .001; 0.951 ± 0.061 vs 0.724 ± 0.116, p < .001). Nevertheless, there were no differences between the Harmonic scalpel and LigaSure groups (p = .435).

CONCLUSION

LigaSure and the Harmonic scalpel might be safer than electrotome when used in thyroid operations. LigaSure generates less heat than the Harmonic scalpel and electrotome. © 2017 Wiley Periodicals, Inc. Head Neck 39: 1078-1085, 2017.

Severity of Recurrent Laryngeal Nerve Injuries in Thyroid Surgery

BACKGROUND

Few studies in the literature have reported recovery data for different types of recurrent laryngeal nerve injuries (RLNIs). This study is the first attempt to classify RLNIs and rank them by severity.

METHODS

This prospective clinical study analyzed 281 RLNIs in which a true loss of signal was identified by intraoperative neuromonitoring (IONM), and vocal cord palsy (VCP) was confirmed by a postoperative laryngoscope. For each injury type, the prevalence of VCP, the time of VCP recovery, and physical changes on nerves were analyzed. Additionally, different RLNI types were experimentally induced in a porcine model to compare morphological change.

RESULTS

The overall VCP rate in at-risk patients/nerves was 8.9/4.6 %, respectively. The distribution of RLNI types, in order of frequency, was traction (71 %), thermal (17 %), compression (4.2 %), clamping (3.4 %), ligature entrapment (1.6 %), suction (1.4 %), and nerve transection (1.4 %). Complete recovery from VCP was documented in 91 % of RLNIs. Recovery time was significantly faster in the traction group compared to the other groups (p < 0.001). The rates of temporary and permanent VCP were 98.6 and 1.4 % for traction lesion, 72 and 28 % for thermal injury, 100 and 0 % for compression injury, 50 and 50 % for clamping injury, 100 and 0 % for ligature entrapment, 100 and 0 % for suction injury, and 0 and 100 % for nerve transection, respectively. Physical changes were noted in 14 % of RLNIs in which 56 % of VCP was permanent. However, among the remaining 86 % IONM-detectable RLNIs without physical changes, only 1.2 % of VCP was permanent. A porcine model of traction lesion showed only distorted outer nerve structure, whereas the thermal lesion showed severe damage in the inner endoneurium.

CONCLUSIONS

Different RNLIs induce different morphological alterations and have different recovery outcomes. Permanent VCP is rare in lesions that are visually undetectable but detectable by IONM. By enabling early detection of RLNI and prediction of outcome, IONM can help clinicians plan intra- and postoperative treatment.

Continuous Intraoperative Neuromonitoring Study Using Pigs for the Prevention of Mechanical Recurrent Laryngeal Nerve Injury in Esophageal Surgery

PURPOSES

During esophageal surgery, clamping injury and injury associated with the use of energy devices are common mechanisms underlying intraoperative recurrent laryngeal nerve (RLN) damage. Recently, intraoperative neuromonitoring (IONM) has been applied to prevent RLN injury. This study was aimed at investigating the changes in the EMG signals associated with clamping injury of the RLN caused by picking up of the nerve with tweezers in domestic pigs.

METHODS

Six domestic pigs (12 RLNs) underwent continuous IONM (CIONM) by our original automated periodic vagal nerve stimulation method.

RESULTS

Our system can be used safely and accurately. The signals showed a decrease of the amplitude when the RLN was picked up and closed slowly by the double-action Maryland with jaw covers. If the clamp was released before the signal amplitude decreased to 50% of the baseline, the signal showed gradual recovery to the baseline in 12 ± 3 minutes.

CONCLUSION

Although there were limitations in our study using domestic pig, including the small sample size, our results are expected to contribute to a decrease in the incidence of RLN damage during esophageal surgery.

Impact of routine recurrent laryngeal nerve monitoring in prone esophagectomy with mediastinal lymph node dissection

BACKGROUND

The problem of recurrent laryngeal nerve (RLN) paralysis (RLNP) after radical esophagectomy remains unresolved. Several studies have confirmed that intraoperative nerve monitoring (IONM) of the RLN during thyroid surgery substantially decreases the incidence of RLN damage. This study tried to determine the feasibility and effectiveness of IONM of the RLN during thoracoscopic esophagectomy in the prone position for esophageal cancer.

METHODS

All 108 patients who underwent prone esophagectomy at Tohoku University Hospital between July 2012 and March 2015 were included in this study. We divided patients into two groups: a control group (No-Monitoring group, surgery without IONM; n = 54) and a study group (Monitoring group, surgery with IONM; n = 54). In Monitoring group, neural stimulation was performed for both RLNs before and after dissection in the thoracic procedure, then for RLNs and vagus nerves (VNs) in the cervical procedure. The feasibility of IONM in Monitoring group and early surgical outcomes were retrospectively compared with those in No-Monitoring group.

RESULTS

IONM could be performed for 47 cases (87.0%) in Monitoring group. Reasons for discontinuation were use of muscle relaxants (3 patients), change in thoracotomy procedure (2 patients), past rib bone fracture (1 patient), and allergic shock by transfusion (1 patient). Right RLNPs were identified postoperatively in 4 patients, and left RLNPs in 23 patients. IONM sensitivities were 92.7 and 88.0% for the right and left VNs, respectively. Incidences of postoperative RLNP, aspiration, and primary pneumonia did not differ significantly between groups.

CONCLUSIONS

This study confirmed the feasibility and safety of IONM of the RLN for thoracoscopic esophagectomy in the prone position. No significant differences in postoperative outcomes were seen between esophagectomy with and without IONM.

Intraoperative neural monitoring in thyroid surgery: lessons learned from animal studies

Recurrent laryngeal nerve (RLN) injury remains a significant morbidity associated with thyroid and parathyroid surgery. In the past decade, surgeons have increasingly used intraoperative neural monitoring (IONM) as an adjunct technique for localizing and identifying the RLN, detecting RLN injury, and predicting the outcome of vocal cord function. In recent years, many animal studies have investigated common pitfalls and new applications of IONM. For example, the use of IONM technology in animal models has proven valuable in studies of the electrophysiology of RLN injury. The advent of animal studies has substantially improved understanding of IONM technology. Lessons learned from animal studies have immediate clinical applications in establishing reliable strategies for preventing intraoperative RLN injury. This article gives an overview of the research progress on IONM-relevant animal models.

Safety of LigaSure in recurrent laryngeal nerve dissection-porcine model using continuous monitoring

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.

Robotic trans-axillary and retro-auricular thyroid surgery

Remote access approaches for thyroid surgery using surgical incisions placed outside the neck, including the axillary, chest and the retro-auricular region have gained interest due to the social stigmatization of young females with a visible neck scar. These novel approaches have been reported to be safe and feasible approaches for thyroid surgery in a select group of patients. Herein, we will discuss different aspects of the current robotic approaches.

Traction injury of the recurrent laryngeal nerve: Results of continuous intraoperative neuromonitoring in a swine model

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.

Electrophysiologic monitoring correlates of recurrent laryngeal nerve heat thermal injury in a porcine model

OBJECTIVES/HYPOTHESIS

Thermal injury to the recurrent laryngeal nerve (RLN) may not be visually apparent and may go unrecognized intraoperatively. This study aimed to investigate the heat thermal tolerance of RLN and evaluate the electrophysiologic correlates of electromyographic (EMG) signal change during an acute RLN heat damage.

STUDY DESIGN

Prospective porcine model with continuous intraoperative neuromonitoring (CIONM).

METHODS

Ten pigs (20 RLNs) undergoing CIONM had their EMG tracings recorded and correlated with heated normal saline (NS) irrigation of varying temperature and duration.

RESULTS

In the initial pilot study, the EMG was without change during incremental heated NS irrigation (40/45/50/55 °C for 60 seconds), but adverse EMG combined events (CE) (amplitude decrease with a concordant latency increase) occurred and degraded to loss of signal (LOS) (by 17.5 ± 1.3 seconds) when the temperature was elevated to 60 °C (n = 4). Another 16 RLNs were evaluated to further compare the EMG pattern after various degrees of thermal stress (60/70 °C for 30/20 seconds). Electromyographic recordings showed CEs and LOS in all RLNs, and only six of eight RLNs with 60 °C exposure showed slight EMG amplitude recovery (16%-35%) after 20 minutes. None of the injured nerve segments were visually apparent, but all were detectable by IONM.

CONCLUSION

Sixty degrees Celsius is a critical temperature to cause RLN thermal injury. Continuous intraoperative neuromonitoring can be used as a tool for the early detection of acute thermal stress and may guide use of energy-based devices during thyroid procedures.

LEVEL OF EVIDENCE

N/A.

Loss of signal in recurrent nerve neuromonitoring: causes and management

During recurrent laryngeal nerve (RLN) neuromonitoring in thyroid surgery, laryngeal electromyography (EMG) amplitude may be correlated with the number of muscle fibers participating in the polarization and these might be correlated with the function of RLN. If RLN is severely injured during the operation, most nerve fibers do not transmit nerve impulse and substantial decrease of EMG amplitude or loss of signal (LOS) will occur. True LOS at the end of an operation often indicates a postoperative fixed vocal cord, and the surgeon should consider the optimal contralateral surgery timing in patients with planned bilateral thyroid operation to avoid the disaster of bilateral vocal cord palsy. However, LOS recovery and false LOS may occur and may lead to an unnecessary 2(nd) operation. Therefore, a reliable modality for intraoperative LOS evaluation and management would afford the surgeon real-time information that could help guide surgical procedure and planning. The updated causes, algorithm, and management of LOS during RLN neuromonitoring are reviewed and summarized.

Recurrent laryngeal nerve monitoring during thoracoscopic esophagectomy

INTRODUCTION

There have been several reports on the feasibility and curability of thoracoscopic esophagectomy, which may reduce injury to the thoracic cage and decrease the invasiveness of surgery. Although the recurrent laryngeal nerve (RLN) is identified and kept intact during operations, RLN palsy sometimes occurs. Currently, surgical aides, including intraoperative neurological monitoring, are being utilized to avoid RLN injury during thyroid surgery. This system is utilized during thoracoscopic esophagectomy in the prone position.

PATIENTS AND METHODS

Seven consecutive patients (six men, one woman; age range 62-74 years; mean 68 years) were included. Patients underwent general anesthesia and were intubated using the NIM TriVantage™ electromyography (EMG) tube. One-lung ventilation was performed with an endobronchial blocker. Thoracoscopic esophagectomy was performed in the prone position. The nerve stimulator was calibrated to 0.5 mA, and after the RLN was visually identified it was subsequently stimulated, which also confirmed normal machine functioning. In some situations, in the absence of a response, stimuli were increased to 1.0 mA and then 2.0 mA.

RESULTS

Intraoperatively, all seven patients had their nerve signals monitored. In one case, a nerve signal disappeared after complete lymph node dissection along the left RLN. This system could identify the site of injury, and the thoracoscopic magnified view allowed the disrupted point to be located precisely. When we checked VTR after surgery, the source of injury was one point tension of the nerve pulled by fiber during lymph node dissection.

CONCLUSIONS

Intraoperative RLN monitoring during thoracoscopic esophagectomy in the prone position, with one-lung ventilation performed using the TriVantage™ EMG tube and a bronchial blocker, is technically feasible, easy, and reliable.

Intraoperative neuromonitoring for the early detection and prevention of RLN traction injury in thyroid surgery: a porcine model

BACKGROUND

Operative traction of the thyroid lobe is a necessary component of thyroid surgery. This surgical maneuver can cause traction injury of the recurrent laryngeal nerve (RLN), and this complication has been reported to be the most common mechanism of nerve injury. The goal of this study was to investigate the electromyographic (EMG) signal pattern during an acute RLN traction injury and establish reliable strategies to prevent the injury using intraoperative neuromonitoring (IONM).

METHODS

Fifteen piglets (30 RLNs) underwent IONM via automated periodic vagal nerve stimulation and had their EMG tracings recorded and correlated with various models of nerve injury.

RESULTS

In the pilot study, a progressive, partial EMG loss was observed under RLN tractions with different tension (n = 8). The changes in amplitudes were more marked and consistent than were the changes in latency. The EMG gradually gained partial recovery after the traction was relieved. Among the nerves injured with electrothermal (n = 4), clamping (n = 1), and transection (n = 1) models, the EMG showed immediate partial or complete loss, and no gradual EMG recovery was observed. Another 16 RLNs were used to investigate the potential of EMG recovery after different extents of RLN traction. We noted the EMG showed nearly full recovery if the traction stress was relieved before the loss of signal (LOS), but the recovery was worse if prolonged or repeated traction was applied. The mean restored amplitudes after the traction was relieved before, during, and after the LOS were 98 ± 3% (n = 6), 36 ± 4% (n = 4), and 15 ± 2% (n = 6), respectively.

CONCLUSION

RLN traction injury showed graded, partial EMG changes; early release of the traction before the EMG has degraded to LOS offers a good chance of EMG recovery. IONM can be used as a tool for the early detection of adverse EMG changes that may alert surgeons to correct certain maneuvers immediately to prevent irreversible nerve injury during the thyroid operation.