Continuous Intraoperative Neuromonitoring Research Articles

Continuous intraoperative neuromonitoring of the facial nerve predicts postoperative facial palsy in parotid surgery: a prospective study.

Facial palsy (FP) is the most significant complication of parotidectomy. Currently, the use of intermittent intraoperative neuromonitoring (iIONM) in parotid surgery facilitates nerve detection, which is paramount to nerve protection. Continuous IONM (cIONM), as applied in thyroid surgery, enables real-time information on electrophysiological nerve status through continuous nerve stimulation, thereby allowing consequent amplitude analysis. To date, the application of cIONM in parotid surgery has not been noted in literature. We performed parotidectomies with anterograde facial nerve visualization using cIONM in 32 consecutive patients in a prospective study (German Register of clinical studies-DRKS 00011051) during the period October 2016 to January 2020. After the facial trunk had been exposed, an atraumatic stimulation electrode was placed and the nerve was stimulated at 3Hz, at a low threshold (0.62 ± 0.06mA), for the entire duration of the preparation. Selected electrophysiological parameters were collected and compared to postoperative facial nerve function, measured by the House-Brackmann grading system. In the post hoc analysis, a significant correlation between a drop in amplitude (< 50% of the "baseline" amplitude) and postoperative FP was recorded (p = 0.001). True positive prediction of FP was noted in 14 out of 16 patients and true negative in 10 out of 16. The sensitivity was 87.5% (AUC 0.75), with a high negative predictive value of 83.3%. cIONM has significant value in predicting postoperative FP in parotidectomy. Future development of an acoustic/optic warning system in IONM devices could prevent nerve injury in real time.

갑상선 수술중 신경모니터링의 최근 연구

Thyroid surgery is associated with a risk of injury to the recurrent laryngeal nerve(RLN), the external branch of the superior laryngeal nerve(EBSLN), and voice changes. Intraoperative neuromonitoring(IONM) has already gained universal reliability to help in nerve identification, safe nerve dissection, and prediction of postoperative vocal cord function. IONM techniques have evolved over the past decade into intermittent IONM(I-IONM) and continuous IONM(C-IONM) modes of application. Research in the field of IONM continues, exploring new techniques and approaches to further enhance the safety and efficacy of thyroid surgery. In this article, the role of IONM and its recent studies will be reviewed.

Cerebral emboli detection and autonomous neuromonitoring using robotic transcranial Doppler with artificial intelligence for transcatheter aortic valve replacement with and without embolic protection devices: a pilot study

BackgroundPeriprocedural ischemic stroke remains a serious complication in patients undergoing transcatheter aortic valve replacement (TAVR). We used a novel robotic transcranial Doppler (TCD) system equipped with artificial intelligence (AI) for...

Continuous intraoperative neuromonitoring of the recurrent laryngeal nerve during lung operations.

The recurrent laryngeal nerve (RLN), especially on the left side, is particularly vulnerable during lung operations. Therefore, continuous intraoperative neuromonitoring (cIONM) would be desirable. With the use of a double-lumen tube (DLT) for single-lung ventilation, there is some uncertainty where the recording electrode should be positioned. The aim of this study was to assess the feasibility of this technique and to predict the ideal position of a single recording electrode. Patients scheduled to undergo left thoracotomy due to pulmonary pathologies, two adhesive electrodes were affixed consecutively above the proximal cuff of the DLT prior to intubation for a precise location of the recording from the vocal cords. Following thoracotomy, the vagus nerve alongside the aortic arch was exposed. A continuous stimulation probe (Saxophone® electrode, Dr. Langer Medical, Waldkirch, Germany) was placed around the nerve. The signals of the respective electrode were recorded and analyzed with regard to previously defined limits of positive signaling. Strong signals with an amplitude of at least 165 µV were recorded in 18 of 20 patients. In these patients 100% of the signals were recorded via the distally located electrode. An additional signal was recorded via the proximal electrode in four patients. cIONM was found to be a safe and reproducible technique. The described technique enables the use of cIONM of the RLN throughout the entire course of the surgical procedure.

Utility of the continuous intraoperative neuromonitoring in the prevention of the recurrent laryngeal nerve paralysis during thyroid surgery. A prospective observational study

BackgroundThe continuous intraoperative neuromonitoring (C-IONM) of the recurrent laryngeal nerve (RLN) could help reducing the incidence of nerve paralysis after thyroid surgery, in comparison with the mere anatomical visualization of the RLN. The objective is to assess the efficacy and utility of C-IONM as a predictive test for recurrent laryngeal nerve paralysis after thyroidectomy. MethodsA prospective observational study was performed in 248 patients who underwent thyroid surgery where C-IONM was applied, between September 2018 and December 2019, in a high-volume center. A previous and later laryngoscopy was performed, which allowed to evaluate the reliability of the C-IONM as a predictive test for recurrent paralysis. Sensitivity (SE), specificity (SP), positive predictive value (PPV), negative predictive value (NPV) were studied. ResultsA total number of 171 thyroidectomies, 62 hemithyroidectomies, 15 totalization thyroidectomies and 27 thyroidectomy with cervical dissections were performed. Postoperative laryngoscopy was altered in 40 patients (16.12%). The SE, SP, PPV and NPV values ​​were 65%, 94.7%, 70.2% and 93.4% respectively. ConclusionsC-IONM is a safe technique that provides real-time information about anatomical and functional integrity of the RLN and can improve the results of thyroid surgery.

Safety of continuous intraoperative vagus nerve neuromonitoring during thyroid surgery.

Continuous intraoperative neuromonitoring has successfully demonstrated to predict impending damage to the recurrent laryngeal nerve, by detecting changes in electromyographic recordings. Despite the apparent benefits associated with continuous intraoperative neuromonitoring, its safety is still a debate. The aim of this study was to investigate the electrophysiological impact of continuous intraoperative neuromonitoring on the vagus nerve. In this prospective study, the amplitude of the electromyographic wave of the vagus nerve-recurrent laryngeal nerve axis was measured both proximally and distally to the stimulation electrode placed upon the vagus nerve. Electromyographic signal amplitudes were collected at three distinct events during the operation: during the dissection of the vagus nerve, before application of the continuous stimulation electrode onto the vagus nerve and after its removal. In total, 169 vagus nerves were analysed, among 108 included patients undergoing continuous intraoperative neuromonitoring-enhanced endocrine neck surgeries. Electrode application resulted in a significant overall decrease in measured proximo-distal amplitudes of -10.94 µV (95 per cent c.i. -17.06 to -4.82 µV) (P < 0.005), corresponding to a mean(s.d.) decrease of -1.4(5.4) per cent. Before the removal of the electrode, the measured proximo-distal difference in amplitudes was -18.58 µV (95 per cent c.i. -28.31 to -8.86 µV) (P < 0.005), corresponding to a mean(s.d.) decrease of -2.50(9.59) per cent. Seven nerves suffered a loss of amplitude greater than 20 per cent of the baseline measurement. In addition to supporting claims that continuous intraoperative neuromonitoring exposes the vagus nerve to injury, this study shows a mild electrophysiological impact of continuous intraoperative neuromonitoring electrode placement on the vagus nerve-recurrent laryngeal nerve axis. However, the small observed differences are negligible and were not associated with a clinically relevant outcome, making continuous intraoperative neuromonitoring a safe adjunct in selected thyroid surgeries.

Continuous vagal intraoperative neuromonitoring during video-assisted thoracoscopic surgery for left lung cancer: its efficacy in preventing permanent vocal cord paralysis.

We investigated the safety and efficacy of continuous intraoperative neuromonitoring (CIONM) during video-assisted thoracoscopic lobectomy for left lung cancer in preventing recurrent laryngeal nerve injury. From August 2015 to March 2020, 22 patients with left lung cancer without CIONM (unmonitored) and 20 patients with left lung cancer with CIONM underwent thoracoscopic lobectomy with complete mediastinal lymph node dissection including 4L dissection. Clinical outcomes from these 2 groups were compared. The incidence of 4L metastasis was 7.14% (3 patients). There was no significant difference in the total number of dissected 4L lymph nodes between the 2 groups (3.23 ± 2.2 in the unmonitored group, 3.95 ± 2.0 in the CIONM group). CIONM was successful in all of the cases. There was no significant difference in the incidence of postoperative vocal cord palsy (22.7% in the unmonitored group, 20% in the CIONM group, P = 1.000). All of the 5 patients (100%) had permanent vocal cord palsy in the unmonitored group. Although statistically insignificant, 75% (3 patients) had total recovery of the vocal cord function, with only 1 patient remaining in permanent vocal cord palsy in the CIONM group. CIONM was safe and efficient. CIONM might be helpful to avoid permanent vocal cord palsy by immediately warning the surgeon about impending nerve injury, so the surgeon can stop delivering further injury to the recurrent laryngeal nerve.

Investigation of the Electrophysiological and Thermographic Safety Parameters of Surgical Energy Devices during Thyroid and Parathyroid Surgery in a Porcine Model

In thyroid and parathyroid surgery, surgical energy devices (SEDs) provide more efficient hemostasis than conventional clamp-and-tie hemostasis in areas with rich blood supply. However, when a SED is activated near the recurrent laryngeal nerve (RLN), the heat generated by the SED may injure the nerve irreversibly. To safely apply SEDs in thyroid/parathyroid surgery, this article introduces experimental porcine model studies to investigate the activation and cooling safety parameters of SEDs in standardized electrophysiological (EP) and thermographic (TG) procedures, respectively. In the EP safety parameter experiments, continuous intraoperative neuromonitoring (C-IONM) is applied to demonstrate the RLN function in real-time. The EP activation study evaluates the safe activation distance of SEDs; the EP cooling study evaluates the safe cooling time of SEDs. In the TG safety parameter experiment, a thermal imaging camera is used to record the temperature change after activating the SED. The TG activation study evaluates the lateral thermal spread distance after SED activation in a dry or humid environment and whether smoke and splashing are generated; the TG cooling study evaluates the cooling time. This will help establish the safety parameters of newly developed SEDs used in thyroid/parathyroid surgery and provide safety guidelines to avoid RLN injury and related complications.

Investigation of the Electrophysiological and Thermographic Safety Parameters of Surgical Energy Devices during Thyroid and Parathyroid Surgery in a Porcine Model.

In thyroid and parathyroid surgery, surgical energy devices (SEDs) provide more efficient hemostasis than conventional clamp-and-tie hemostasis in areas with rich blood supply. However, when a SED is activated near the recurrent laryngeal nerve (RLN), the heat generated by the SED may injure the nerve irreversibly. To safely apply SEDs in thyroid/parathyroid surgery, this article introduces experimental porcine model studies to investigate the activation and cooling safety parameters of SEDs in standardized electrophysiological (EP) and thermographic (TG) procedures, respectively. In the EP safety parameter experiments, continuous intraoperative neuromonitoring (C-IONM) is applied to demonstrate the RLN function in real-time. The EP activation study evaluates the safe activation distance of SEDs; the EP cooling study evaluates the safe cooling time of SEDs. In the TG safety parameter experiment, a thermal imaging camera is used to record the temperature change after activating the SED. The TG activation study evaluates the lateral thermal spread distance after SED activation in a dry or humid environment and whether smoke and splashing are generated; the TG cooling study evaluates the cooling time. This will help establish the safety parameters of newly developed SEDs used in thyroid/parathyroid surgery and provide safety guidelines to avoid RLN injury and related complications.

Continuous intraoperative neuromonitoring of the recurrent laryngeal nerve by eliciting the laryngeal adductor reflex (LAR-CIONM).

The laryngeal adductor reflex (LAR) is a life-sustaining airway protective mechanism that serves to shield the lower airways from inhaled foreign bodies. Over the past half century, the LAR has been extensively investigated and its dysfunction has been linked to far-ranging pathologies, from dysphagia to sudden infant death syndrome. Over the past 6years, specific electromyographic waves in the LAR response have been used to devise a methodology for monitoring the vagus and recurrently laryngeal nerves during surgical procedures. This methodology involves continuous intraoperative neuromonitoring of the laryngeal adductor reflex and isthus termed 'LAR-CIONM'. In this review paper, the physiology of the LAR will be summarized as it relates to LAR-CIONM and the technique of LAR-CIONM will be described. Applications of this technique and published outcomes of LAR-CIONM will be highlighted.

Utility of the continuous intraoperative neuromonitoring in the prevention of the recurrent laryngeal nerve paralysis during thyroid surgery. A prospective observational study

BackgroundThe continuous intraoperative neuromonitoring (C-IONM) of the recurrent laryngeal nerve (RLN) could help reducing the incidence of nerve paralysis after thyroid surgery, in comparison with the mere anatomical visualization of the RLN. The objective is to assess the efficacy and utility of C-IONM as a predictive test for recurrent laryngeal nerve paralysis after thyroidectomy. MethodsA prospective observational study was performed in 248 patients who underwent thyroid surgery where C-IONM was applied, between September 2018 and December 2019, in a high-volume center. A previous and later laryngoscopy was performed, which allowed to evaluate the reliability of the C-IONM as a predictive test for recurrent paralysis. Sensitivity (SE), specificity (SP), positive predictive value (PPV), negative predictive value (NPV) were studied. ResultsA total number of 171 thyroidectomies, 62 hemithyroidectomies, 15 totalization thyroidectomies and 27 thyroidectomy with cervical dissections were performed. Postoperative laryngoscopy was altered in 40 patients (16.12%). The SE, SP, PPV and NPV values ​​were 65%, 94.7%, 70.2% and 93.4% respectively. ConclusionsC-IONM is a safe technique that provides real-time information about anatomical and functional integrity of the RLN and can improve the results of thyroid surgery.

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

ObjectivesQuantum 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).MethodsThis 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.ResultsIn 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.ConclusionQMR 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.

Clinical Application of Continuous Intraoperative Neuromonitoring during Thyroid Surgery

Routine visual identification of the recurrent laryngeal nerve (RLN) is the gold standard of care during thyroidectomy because it is associated with low rates of RLN palsy. Over the last two decades, intraoperative neuromonitoring (IONM), which allows for assessment of the RLN’s functional integrity during the operation, has been widely used for risk minimization in thyroid surgery as a valuable adjunct to visual nerve identification. Currently, one of the most important trends in IONM is the real-time monitoring of the vagus nerve (VN) to prevent iatrogenic injury of RLN. Continuous IONM (C-IONM) seems to be superior to intermittent IONM (I-IONM) because it enhances standardization by permanent VN stimulation and provides entire and constant RLN function monitoring during thyroidectomy procedures. In this article, we provide a comprehensive review of the C-IONM technique.

Clarifying optimal outcome measures in intermittent and continuous laryngeal neuromonitoring.

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. Expert review consensus statement utilizing modified Delphi methodology. 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. 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.

Recurrent Laryngeal Nerve Preservation Strategies in Pediatric Thyroid Oncology: Continuous vs. Intermittent Nerve Monitoring.

Simple SummaryThyroid operations in children are difficult because children have thinner nerves than adults, and there is less space for the surgeon to operate. Since it runs closely behind the thyroid capsule, the nerve innervating the vocal cords can be injured during the operation. In thyroid cancer, the thyroid gland typically needs to be removed completely, putting the nerve at greater risk of injury. This surgical risk can be reduced by monitoring the function of the nerve before it is lastingly damaged. There are two methods to achieve this: intermittent (longer intervals between pulses) and continuous (very small intervals between pulses) nerve stimulation. In this study of 258 children with suspected or confirmed thyroid cancer, nerve damage and vocal cord palsy were observed only after intermittent and not after continuous nerve stimulation. This demonstrated that continuous nerve stimulation was safer than intermittent nerve stimulation.(1) Background: Pediatric thyroidectomy is characterized by considerable space constraints, thinner nerves, a large thymus, and enlarged neck nodes, compromising surgical exposure. Given these challenges, risk-reduction surgery is of paramount importance in children, and even more so in pediatric thyroid oncology. (2) Methods: Children aged ≤18 years who underwent thyroidectomy with or without central node dissection for suspected or proven thyroid cancer were evaluated regarding suitability of intermittent vs. continuous intraoperative neuromonitoring (IONM) for prevention of postoperative vocal cord palsy. (3) Results: There were 258 children for analysis, 170 girls and 88 boys, with 486 recurrent laryngeal nerves at risk (NAR). Altogether, loss of signal occurred in 2.9% (14 NAR), resulting in six early postoperative vocal cord palsies, one of which became permanent. Loss of signal (3.5 vs. 0%), early (1.5 vs. 0%), and permanent (0.3 vs. 0%) postoperative vocal cord palsies occurred exclusively with intermittent IONM. With continuous nerve stimulation, sensitivity, specificity, positive and negative predictive values, and accuracy reached 100% for prediction of early and permanent postoperative vocal cord palsy. With intermittent nerve stimulation, sensitivity, specificity, positive and negative predictive values, and accuracy were consistently lower for prediction of early and permanent postoperative vocal cord palsy, ranging from 78.6% to 99.8%, and much lower (54.2–57.9%) for sensitivity. (4) Conclusions: Within the limitations of the study, continuous IONM, which is feasible in children ≥3 years, was superior to intermittent IONM in preventing early and permanent postoperative vocal cord palsy.

Vagus Nerve Injury during Continuous Intraoperative Neuromonitoring (cIONM) for Thyroid Surgery: Assessment of Severity

Introduction: Vocal cord palsy is one of the biggest concern in thyroid surgery especially among the professional voice user. Continuous intra-operative nerve monitoring allows real time of the nerve function during surgery that will reduce risk of injury. The procedure involve is not without complication but meticulous usage and following standard operating procedure is utmost important. This study was aimed looking at the potential morbidity of the procedure.&#x0D; Methodology: A prospective observational study was conducted on 20 patients who underwent routine thyroid surgery using c-IONM. The procedure of c-IONM follows the standard guidelines. Measurements of vagal stimulation were taken proximal(V3) and distal(V2) to APS electrode to document any injury to the vagus nerve. The blood pressure and pulse rate were also documented through-out surgery, looking at the physiological effect of the stimulation. The function of the vocal cord was assessed by pre and post-operative laryngoscopy&#x0D; Result: 18 patients with 29 nerves at risk were included as in two patients, the vagal stimulation did not achieve the acceptable amplitude (400 µV). There were drops of amplitude between V3 and V2 in 14 nerve at risks but there was clinical evidence of palsy on laryngoscopy. There were also fluctuation of mean arterial pressure and pulse rate but not significant enough to warrant intervention.&#x0D; Conclusion: The use of c-IONM during thyroidectomy do exert minimal effect on the vagus nerve and its function but not significant enough to abandoned the procedure. It is safe and able to help the surgeon to identify and preserve the nerve function especially in difficult thyroidectomy

Intraoperative Neural Monitoring for Early Vocal Cord Function Assessment After Thyroid Surgery: A Systematic Review and Meta-Analysis.

Objective This study evaluated the diagnostic accuracies of various forms of intraoperative neural monitoring (IONM) in terms of predicting vocal cord palsy after thyroidectomy. Methods Two authors independently reviewed the six databases (PubMed, the Cochrane database, Embase, the Web of Science, SCOPUS, and Google Scholar) from their dates of inception to March 2021. Intraoperative electromyographic neuromonitoring (IONM) was compared with laryngoscopic detection (the reference method). True-positive, true-negative, false-positive, and false-negative data were extracted from each study. Methodological quality was evaluated using the Quality Assessment of Diagnostic Accuracy Studies ver. 2 tool. Results Twenty-seven prospective or retrospective studies were included. The diagnostic odds ratio for IONM was 152.9623 ([95% confidence interval [75.4249; 310.2085]. The area under the summary receiver operating characteristic curve was 0.966. The sensitivity, specificity, negative predictive value, and positive predictive value were 0.8219 ([0.6862; 0.9069]), 0.9783 ([0.9659; 0.9863]), 0.9943 ([0.9880; 0.9973]), and 0.5523 ([0.4458; 0.6542]), respectively. The correlation between sensitivity and false-positive rate was 0.200, indicating the absence of heterogeneity. Subgroup analysis showed that the diagnostic accuracies of the continuous IONM was higher than those of intermittent IONM, and recent publications (> 2011) was higher than early publication (< 2010). Conclusions As the technology and knowledge of IONM have been accumulated and progressed over the past decades, the predictive value of IONM in postoperative vocal cord palsy has also improved. Moreover, the advances of continuous IONM technology could make a breakthrough in vocal cord evaluation after thyroid surgery.

Tensile strength analysis of automatic periodic stimulation for continuous intraoperative neural monitoring in a piglet model

Continuous intraoperative neural monitoring (C-IONM) during thyroid surgery is a useful tool for preventing recurrent laryngeal nerve (RLN) injury. The present study aims to analyze the tensile strength tolerance of C-IONM electrodes on the vagal nerve (VN). A C-IONM wire was enclosed in a hand-held tensile testing system. The probe displacement on the VN was continuously monitored by positioning a second probe far-up/proximally in a piglet model, and an automatic periodic stimulation (APS) accessory was used. The 3-mm and 2-mm APS accessory has a mean tensile strength of 20.6 ± 10 N (range, 14.6–24.4 N) and 11.25 ± 8 N (range, 8.4–15.6 N), respectively (P = 0.002). There was no difference between bilateral VNs. The mean amplitude before and during electrode displacement was 1.835 ± 102 μV and 1.795 ± 169 μV, respectively (P = 0.45). The mean percentage of amplitude decrease on the electromyography (EMG) was 6.9 ± 2.5%, and the mean percentage of latency increase was 1.9 ± 1.5%. No significant amplitude reduction or loss of signal (LOS) was observed after > 50 probe dislocations. C-IONM probe dislocation does not cause any LOS or significant EMG alterations on the VN.

Neuromonitoring of the Recurrent Laryngeal Nerve Reduces the Rate of Bilateral Vocal Cord Dysfunction in Planned Bilateral Thyroid Procedures.

Purpose: Bilateral vocal cord dysfunction (bVCD) is a rare but feared complication of thyroid surgery. This long term retrospective study determined the effect of intraoperative neuromonitoring (IONM) of the recurrent laryngeal nerve (RLN) during thyroid surgeries with regard to the rate of bVCD and evaluated the frequency as well as the outcome of staged operations. Methods: Retrospective analysis of prospectively documented data (2000–2019) of a tertiary referral centers’ database. IONM started in 2000 and, since 2010, discontinuation of surgery was encouraged in planned bilateral surgeries to prevent bVCD, if non-transient loss of signal (ntLOS) occurred on the first side. Datasets of the most recent 40-month-period were assessed in detail to determine the clinical outcome of unilateral ntLOS in planned bilateral thyroid procedures. Results: Of 22,573 patients, 65 had bVCD (0.288%). The rate of bVCD decreased from 0.44 prior to 2010 to 0.09% after 2010 (p < 0.001, Chi2). Case reviews of the most recent 40 months period identified ntLOS in 113/3115 patients (3.6%, 2.2% NAR), of which 40 ntLOS were recorded during a planned bilateral procedure (n = 952, 2.1% NAR). Of 21 ntLOS occurring on the first side of the bilateral procedure, 15 procedures were stopped, subtotal contralateral resections were performed, and thyroidectomy was continued in 3 patients respectively, with the use of continuous vagal IONM. Eighteen cases of VCD were documented postop, and all but one patient had a full recovery. Seven patients had staged resections after 1 to 18 months (median 4) after the first procedure. Conclusion: IONM facilitates reduced postoperative bVCD rates. IONM is, therefore, recommendable in planned bilateral procedures. The rate of non-complete bilateral surgery after intraoperative non-transient LOS was 2%.

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.