Pitfalls of Intraoperative Neuromonitoring for Predicting Postoperative Recurrent Laryngeal Nerve Function during Thyroidectomy

Utilizing Surgeon-Performed Intraoperative Translaryngeal Ultrasound for Verifying Vocal Fold Function: A Troubleshooting Approach for Intraoperative Neuromonitoring in Neck Surgery

INTRODUCTION

We investigated transcutaneous laryngeal ultrasonography (TLUS) for assessing vocal fold (VF) mobility during thyroid and parathyroid surgeries, emphasizing its precision and utility in signal loss scenarios.

METHODS

Between October 2020 and January 2023, we performed TLUS, Doppler sonography, laryngeal twitch response (LTR) palpation, and electromyography (EMG) to monitor recurrent laryngeal nerve function during neck surgeries. Postoperatively, the VF activity was verified using fiberoptic video laryngoscopy (FL). Concordance with FL was categorized based on VF activity.

RESULTS

Of the 443 VF evaluations, no instances of permanent bilateral paralysis were noted. Temporary unilateral palsy was found in 3.38% and permanent in 0.45%. TLUS displayed 97.8% agreement with EMG and was diagnostically superior (99.7% vs 98.2%) and more affordable ($68 vs $300) compared to analogous operative durations.

CONCLUSION

TLUS rivals EMG in terms of intraoperative neuromonitoring accuracy and outperforms LTR. Being cost-effective, TLUS can effectively address signal loss situations, thereby averting additional surgeries.

Clinical validation of NerveTrend versus conventional i-IONM mode of NIM Vital in prevention of recurrent laryngeal nerve events during bilateral thyroid surgery: A randomized controlled trial

BACKGROUND

The aim of this study was to test the hypothesis that use of NerveTrend™ mode of intermittent neuromonitoring (i-IONM) during thyroidectomy may identify and prevent impending recurrent laryngeal nerve (RLN) injury.

METHODS

A randomized clinical trial. The primary outcome was prevalence of RLN injury on postoperative day 1. In NerveTrend™ group the i-IONM stimulator was used for trending of amplitude and latency changes from initial vagal electromyographic baseline to tailor surgical strategy.

RESULTS

Some 264 patients were randomized into the intervention versus the control group, 132 patients each. RLN injury was found on postoperative day 1 in 5/264 (1.89%) nerves at risk (NAR) versus 12/258 (4.65%) NAR whereas staged thyroidectomy was used in 0/132 (0.00%) versus 6/132 (4.54%) patients (p = 0.067 and p = 0.029, respectively).

CONCLUSION

The use of NerveTrend™ mode resulted in tendency towards reduced RLN injury on postoperative day 1 and significant decrease of need for a staged thyroidectomy.

Comparison of EMG amplitudes recorded by ipsilateral and contralateral electrodes placement during using trans-thyroid cartilage recording method in thyroid surgery

Objectives

The feasibility and reliability of trans-thyroid cartilage EMG recording method (TCERM) during intraoperative monitoring (IONM) of the recurrent laryngeal nerve (RLN) in thyroid surgery have been established. This study compared two different recording electrode placements on the ipsi-lateral and contra-lateral lamina of the thyroid cartilage (TC).

Methods

Fifty consecutive patients undergoing total thyroidectomy with 100 RLNs at risk were enrolled. Two paired subdermal needle electrodes were inserted into the subperichondrium of the bilateral TC lamina to record electromyography (EMG) signals. The channel leads from the TC electrodes were connected to the patient interface with two different modes. In A-mode, the electrode leads were placed ipsi-laterally, and channel 1 monitored the left RLN and channel 2 monitored the right RLN respectively. In B-mode, the electrode leads were placed contra-laterally, and channels 1 and 2 simultaneously monitored the same side of the RLN. The amplitudes of four EMG signals (V1-R1-R2-V2) recorded by A-mode and B-mode were compared.

Results

All EMG amplitudes of V1-R1-R2-V2 signals recorded with B-mode were all above 500μV and significantly higher than those with A-mode (p<0.001). No false loss of signal, electrode dislodgement, or needle-related complications were noted during IONM. Postoperatively, all patients had symmetrical vocal cord movement. Lower EMG amplitudes were observed in older and male patients. Histopathology and laterality showed no significant differences in EMG amplitude.

Conclusion

During using TCERM in thyroid surgery, the recording electrodes should be placed contra-laterally on the TC lamina. This approach ensures high and stable EMG signals, which are important for high-quality IONM of the RLN.

The impact of intraoperative neural monitoring during papillary thyroid cancer surgery on completeness of thyroidectomy and thyroglobulin response: a propensity-score matched study

BACKGROUND

Intraoperative neural monitoring (IONM) has been utilized for a variety of thyroid pathologies, including papillary thyroid carcinoma (PTC). Remnant thyroid tissue following total thyroidectomy (TT) in patients with PTC is associated with increased recurrence. The aim of this study is to investigate whether the use of IONM in PTC surgery has an impact on the completeness of thyroidectomy.

METHODS

Retrospectively, patients with preoperative diagnosis of PTC, who underwent TT in a tertiary center were reviewed. They were grouped based on the IONM usage, and 1:1 propensity-score match was performed. Primary outcome was the completeness of thyroidectomy, determined by measuring postoperative stimulated thyroglobulin levels (sTg).

RESULTS

Among 274 clinically node-negative PTC patients who underwent TT and ipsilateral prophylactic central lymph-node dissection, a total of 170 patients (85:85) were matched. Postoperative sTg levels were significantly lower in the IONM group (1 ng/dL vs. 0.4 ng/dL; p < 0.01) with higher percentage of the patients with sTg levels <1 ng/ml (50.6% vs. 69.4%; p = 0.01). More patients in the no-IONM group received RAI ablation with significantly higher doses (mean mci: 120 vs. 102; p = 0.02).

CONCLUSION

The use of IONM during thyroidectomy provides improvement in the completeness of thyroidectomy and reduction in postoperative sTg levels which can be used as a guide by clinicians to avoid RAI ablation in selected PTC patients and to adjust low ablative doses in patients who are scheduled for remnant ablation.

The TOFr of 0.75 to 0.85 is the optimal timing for IONM during thyroid surgery: a prospective observational cohort study

BACKGROUD

Recurrent laryngeal nerve (RLN) injury is one of the serious complications of thyroid tumour surgery, surgical treatment of thyroid cancer requires careful consideration of the RLN and its impact on glottis function. There has been no unified standard for precise neuromuscular block monitoring to guide the monitoring of RLN in thyroid surgery. This study aimed to investigate the correlation between Train-of-four stabilization ratio (TOFr) and neural signal values of intraoperative neurophysiological monitoring (INOM) during thyroid operation, and further to determine the optimal timing for INOM during thyroid operation.

METHODS

Patients scheduled for thyroid tumour resection with INOM and RLN monitoring from April 2018 to July 2018 in our center were recruited. Electromyography (EMG) signals and corresponding TOFr were collected. All nerve stimulation data were included in group VR. Vagus nerve stimulation data were included in Subgroup V. RLN stimulation data were included in Subgroup R. The timing of recording was as follows: Vagus nerve EMG amplitude after opening the lateral space between the thyroid and carotid sheath and before the initiation of thyroid dissection, RLN EMG amplitude at first recognition, RLN EMG amplitude after complete thyroid dissection (Repeat three times), and Vagus nerve EMG amplitude after resection of the thyroid (Repeat three times). Correlation analysis of continuous variables was described by a scatter diagram. Pearson correlation analysis or Spearman correlation analysis was used for the two groups of variables.

RESULTS

Finally, 134 vagus nerve signals and 143 RLN signals were analysed after matching with TOFr. The EMG amplitude in the VR group and subgroups after nerve stimulation was positively correlated with TOFr (p < 0.05). In the VR, V and R group, the incidence of EMG ≥ 500 µV in the 0.75 < TOFr ≤ 0.85 interval was significantly higher than the 0 < TOFr ≤ 0.75 interval (P = 0.002, P = 0.013 and P = 0.029), and has no statistical difference compared to 0.85 < TOFr ≤ 0.95 interval (P > 0.05).

CONCLUSIONS

The EMG signals of the RLN and vagus nerve stimulation during thyroid surgery were positively correlated with TOFr. TOFr > 0.75 could reflect more than 50% of the effective nerve electrophysiological signals, 0.75 < TOFr ≤ 0.85 interval was the optimal timing for IONM during thyroid surgery.

TRIAL REGISTRATION

Chinese Clinical Trial Registry (ChiCTR1800015797) Registered on 20/04/2018. https://www.chictr.org.cn .

Surgical tips and techniques to avoid complications of thyroid surgery

Objectives

Surgery of the thyroid takes place in a body part with complicated anatomy and several vital physiologic functions. Thyroidectomy is rarely associated with mortality but can be followed by significant complications, (i.e. hypoparathyroidism, hemorrhage, upper airway obstruction, laryngeal nerve injuries and thyrotoxic storm). This review aims to indicate surgical tips and techniques to sustain a low level of complications.

Content

MEDLINE database (PubMed) platform was used as a search engine and the articles related to the topic were selected using the keywords combination "thyroid surgery and complications".

Summary and Outlook

The most common complication of total thyroidectomy with an occurrence ranging between 0.5 and 65% is hypoparathyroidism. Damage to recurrent laryngeal nerves can be temporary or permanent, unilateral or bilateral; bilateral lesion is associated with severe episodes of breathlessness. Thus, intraoperative monitoring of nerve function is essential to prevent damage. Ιn addition, hematoma formation can lead to breathing difficulties due to airway obstruction; preventive hemostasis during surgery is essential. The surgeon must have a complete anatomical understanding of not only the normal anatomy of the central visceral compartment of the neck, but also the common variations of the laryngeal nerves and parathyroid glands in order to keep the complication rate at a very low level.

An atypical bilateral trifurcation of recurrent laryngeal nerve

Background

Thyroidectomy is a frequently performed surgery for benign and malignant conditions. Nevertheless, one of the most critical complications of thyroidectomy is recurrent laryngeal nerve (RLN) injury leading to vocal cord paralysis. A thorough knowledge of the anatomical variations of RLN and ligation of the related vessels close to their distal branches is critical to avoid injury.

Case presentation

Here, we report the first case of bilateral trifurcation of recurrent laryngeal nerve (RLN) in a 40-year old woman with multinodular goitre. Total thyroidectomy was performed and RLN was preserved bilaterally. Followed by a precise dissection, fine branches were traced penetrating the larynx. We did not observe any further post-operative complications and patient was discharged with desired outcomes.

Conclusions

Anatomical variations of the RLN include—bifurcations, trifurcations, relation of RLN with inferior thyroid artery (ITA) and presence of non-recurrent laryngeal nerve. Only RLN dividing at a distance greater than 5 mm (branching point distance) before its entry into the larynx beneath the cricothyroid are said to bifurcate or trifurcate. Approximately 25% of nerves show branching [71%—unilateral and 18%—bilateral bifurcation]. Incidence of unilateral trifurcations have been noted be 0.9% and the rates of bilateral trifurcation and the divisions of the branches is yet to be ascertained. This is the first report of a bilateral trifurcation of RLN, detected in patient with multinodular goitre and hence warrants a precise analysis of variations of the RLN in patients undergoing thyroidectomy, which is critical to prevent RLN injury.

Transcutaneous Laryngeal Ultrasonography for Assessing Vocal Cord Twitch Response in Thyroid Operation during Predissection Vagus Nerve Stimulation

BACKGROUND

In this study, we aimed to report our experience with the use of intraoperative transcutaneous laryngeal ultrasonography (TLUSG) to evaluate the vocal cord twitch response during predissection vagus nerve stimulation in thyroid surgeries and examine the reliability of this technique when compared with that of laryngeal twitch palpation (LTP).

STUDY DESIGN

The prospective data collection of consecutive patients who underwent open thyroidectomy with intraoperative neuromonitoring (IONM) was reviewed retrospectively. We recorded the electromyographic activity and assessed the vocal cord twitch response on LTP, TLUSG. We compared the accessibility, sensitivity, and specificity of the techniques.

RESULTS

A total of 110 patients (38 men and 72 women) with 134 nerves at risk were enrolled. The vocal cord was assessable by TLUSG in 103 (93.6%) patients and by LTP in 64 (59.1%) patients. Two patients showed negative predissection IONM signal but positive on TLUSG and the presence of laryngeal twitch response confirmed by laryngoscopy. Fourteen patients showed positive IONM signals and presence of the vocal cord twitch response on TLUSG but not on LTP. The sensitivity and specificity were 70.21% and 100%, respectively, for LTP, and those both were 100% for TLUSG. For patients who could be assessed using both techniques, TLUSG had better accuracy than LTP (100% vs 80.33%, p = 0.0005).

CONCLUSIONS

The innovative intraoperative application of TLUSG is better for evaluating the laryngeal twitch response than LTP. This technique provides practical troubleshooting guidance for patients with no IONM signals during predissection vagus nerve stimulation.

Human Amnion/Chorion Membrane May Reduce Transient Recurrent Laryngeal Nerve Injury During Thyroid Surgery

Recurrent laryngeal nerve (RLN) damage is a significant and prevalent complication of thyroid surgery. Based on the beneficial role of a human amnion/chorion membrane (HACM) allograft in wound management and nerve regeneration, we investigated whether placement of a commercially available HACM allograft on dissected RLN could reduce the occurrence and/or duration of RLN injury during thyroidectomy. Among 67 patients undergoing thyroidectomy, 100 at-risk nerves (exposure of at least 3 cm of RLN) received intraoperative placement of HACM; 205 at-risk RLNs without HACM in 134 matched patients served as controls. Patient-reported vocal analysis, physician-assessed vocal analysis, and laryngoscopic assessment of vocal-fold dysfunction were performed before and after surgery. At 24 h after surgery, 17 patients in the control group (12.5%) had documented voice changes; these changes persisted for at least 3 weeks in seven patients (5%). Only one patient (1.5%) in the HACM group had vocal changes at 24 h after surgery, which resolved within 1 week (P < 0.01). Intraoperative placement of the HACM allograft over at-risk RLNs during thyroidectomy may reduce the incidence, severity, and/or duration of intraoperative RLN injury, which could address a significant complication of head and neck surgery. A larger prospectively designed clinical study is warranted to further investigate a possible benefit of the HACM allograft in thyroid surgery and to begin to understand the mechanisms through which a clinical benefit might be mediated.

Necessity of Routinely Testing the Proximal and Distal Ends of Exposed Recurrent Laryngeal Nerve During Monitored Thyroidectomy

OBJECTIVES

Intraoperative neuromonitoring (IONM) is a useful tool to evaluate the function of recurrent laryngeal nerve (RLN) in thyroid surgery. This study aimed to determine the necessity and value of routinely testing the proximal and distal ends of RLN.

METHODS

In total, 796 patients undergoing monitored thyroidectomies with standardized procedures were enrolled. All 1346 RLNs with visual integrity of anatomical continuity were routinely stimulated at the most proximal (R2p signal) and distal (R2d signal) ends after complete RLN dissection. The EMG amplitudes between R2p and R2d signals were compared. If the amplitude of R2p/R2d ratio reduction (RPDR) was over 10% or loss of signal (LOS) occurred, the exposed RLN was mapped to identify the injured point. Pre- and post-operative vocal cord (VC) mobility was routinely examined with video-laryngofiberscope.

RESULTS

Nerve injuries were detected in 108 (8%) RLNs, including 94 nerves with incomplete LOS (RPDR between 13%-93%) and 14 nerves with complete LOS. The nerve injuries were caused by traction in 80 nerves, dissecting trauma in 23 nerves and lateral heat spread of energy-based devices in 5 nerves. Symmetric VC mobility was found in 72 nerves with RPDR ≤50%. The occurrence of abnormal VC mobility (weak or fixed) was 14%, 67%, 100%, and 100% among the different RPDR stratifications of 51%-60%, 61%-70%, 71%-80%, and 81-93%, respectively. Of the 14 nerves with complete LOS, all showed fixed VC mobility. Permanent VC palsy occurred in 2 nerves with thermal injury.

CONCLUSION

Routinely testing the proximal and distal ends of exposed RLN helps detect unrecognized partial nerve injury, elucidate the injury mechanism and determine injury severity. The procedure provides accurate information for evaluating RLN function after nerve dissection and should be included in the standard IONM procedure.

Recurrent Laryngeal Nerve Injury Near the Nerve Entry Point in Total Endoscopic Thyroidectomy: A Retrospective Cohort Study

Background

Recurrent laryngeal nerve injury (RLNI) still occurs in total endoscopic thyroidectomy (TET) by using intraoperative neuromonitoring (IONM). As the region where most injuries occur, more attention should be paid to RLNI near the nerve entry point (NEP) in TET.

Materials and Methods

This cohort study collected retrospectively data from 415 patients who underwent TET between February 2012 and December 2019. The functions of the recurrent laryngeal nerve (RLN) in TET were recorded by IONM. The patients with RLNI near the NEP were followed up by laryngoscopies. The demographic and clinical characteristics, the mechanisms of RLNI, and the outcomes of RLNI were recorded and analyzed.

Results

There were a total of 444 at-risk nerves in 405 patients were analyzed. The incidence of RLNI near the NEP was 7.9%. RLNs with extralaryngeal branches were more likely to be injured near the NEP (P = 0.037). The incidences of different types of RLNI, in order of frequency, were 68.8% for thermal injury (n = 22), 28.1% for traction/compression injury (n = 9), and 3.1% for transverse injury (n = 1). A total of 93.8% (n = 30) of RLNI patients had complete recovery of vocal cord activity function.

Conclusion

The extralaryngeal branch was a risk factor for RLNI near the NEP in TET. Thermal injury caused by an ultrasonic scalpel was the most common cause of RLNI near the NEP. Most RLNIs near the NEP would eventually recover.

Nerve monitoring decreases recurrent laryngeal nerve injury risk for neoplasm-related thyroidectomy

OBJECTIVE

Conflicting reports exist regarding the benefit of intraoperative neuromonitoring (INM) for patients undergoing thyroidectomy. We hypothesized that in a national sample, the risk of mild and severe RLNi is decreased for patients undergoing neoplasm-related disease (NRD) thyroidectomy with INM compared to patients without INM.

METHODS

The database was queried for patients that underwent total thyroidectomy for NRD with and without INM. A multivariable logistic regression model was used to determine the associated odds of RLNi.

RESULTS

From 6942 patients, 4269 (61.5%) had INM during thyroidectomy. Patients with INM had a similar rate of overall RLNi compared to patients without INM (5.7% vs. 6.6%, p = 0.118). After adjusting for covariates, INM was associated with decreased odds of severe-RLNi (OR 0.23, p = 0.036) but not mild-RLNi (p = 0.16).

CONCLUSION

INM is associated with a nearly 80% decreased associated odds of severe RLNi during thyroidectomy for NRD. Future prospective confirmation is needed, and if confirmed, patients undergoing thyroidectomy for NRD should have INM to reduce the risk of RLNi and its associated morbidity.

Intraoperative trans-laryngeal ultrasound (LUSG) of the vocal cord is a novel method of confirming the recurrent laryngeal nerve (RLN) integrity during thyroid and neck surgery

BACKGROUND

Eliciting a normal electromyography signal has been the usual method to confirm the functional integrity of the recurrent laryngeal nerve during intraoperative nerve monitoring. Given that oscillations of the vocal cord can be detected with trans-laryngeal ultrasound when the ipsilateral recurrent laryngeal nerve is stimulated with the endotracheal tube in situ, we aimed to compare the accuracy and cost of this novel method with the conventional electromyography method.

METHODS

Consecutive patients who underwent elective thyroid, parathyroid or neck dissection procedures were included. The NIM-Neuro 3.0 system was used. Endotracheal tube-based surface electrodes were utilized for electromyography signal recording. Standard anesthetic technique was adopted. Recurrent laryngeal nerve integrity was verified by both detection methods (laryngeal ultrasound and electromyography) independently. Vocal cord function was validated by flexible direct laryngoscopy postoperatively. For each method, concurrence with flexible direct laryngoscopy was defined as "true-positive" or "true-negative," based on the presence or absence of vocal cord paresis. Accuracy was calculated as the sum of all true positives and negatives divided by the total of nerves-at-risk. The cost of each method was calculated.

RESULTS

One hundred and four patients were eligible. Total number of nerves-at-risk was 155. Based on flexible direct laryngoscopy findings, the test sensitivity, specificity, positive predictive value, and negative predictive value of intraoperative laryngeal ultrasound were 75.0%, 99.3%, 85.7%, and 98.6%, respectively, while those of electromyography were 87.5%, 98.0%, 70.0%, and 99.3%, respectively. The prognostic accuracy in laryngeal ultrasound versus electromyography was comparable (98.1% vs 97.4%). The cost of the laryngeal ultrasound per operation was less than electromyography ($82 vs $454).

CONCLUSION

Laryngeal ultrasound has a similar detection accuracy to electromyography during intraoperative nerve monitoring. Apart from being a cheaper alternative, laryngeal ultrasound may be useful when there is unexplained loss of electromyography signals during surgery and may play a role in the intraoperative nerve monitoring troubleshooting algorithm.

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.

Assessment of Intraoperative Nerve Monitoring Parameters Associated With Facial Nerve Outcome in Parotidectomy for Benign Disease

Importance

Prior studies suggest that the use of facial nerve monitoring decreases the rate of immediate postoperative facial nerve weakness in parotid surgery, but published data are lacking on normative values for these parameters or cutoff values to prognosticate facial nerve outcomes.

Objective

To identify intraoperative facial nerve monitoring parameters associated with postoperative weakness and to evaluate cutoff values for these parameters under which normal nerve function is more likely.

Design, Setting, and Participants

This retrospective case series of 222 adult patients undergoing parotid surgery for benign disease performed with intraoperative nerve monitoring was conducted at an academic medical institution from September 13, 2004, to October 30, 2014. The data analysis was conducted from May 2018 to January 2019.

Main Outcomes and Measures

The main outcome measure was facial nerve weakness. Receiver operating characteristic curves were generated to define optimal cut point to maximize the sensitivity and specificity of the stimulation threshold, mechanical events, and spasm events associated with facial nerve weakness.

Results

Of 222 participants, 121 were women and 101 were men, with a mean (SD) age of 51 (16) years. The rate of temporary facial nerve paresis of any nerve branch was 45%, and the rate of permanent paralysis was 1.3%. The mean predissection threshold was 0.22 milliamperes (mA) (range, 0.1-0.6 mA) and the mean postdissection threshold was 0.24 mA (range, 0.08-1.0 mA). The average number of mechanical events was 9 (range, 0-66), and mean number of spontaneous spasm events was 1 (range, 0-12). Both the postdissection threshold (area under the curve [AUC], 0.69; 95% CI, 0.62-0.77) and the number of mechanical events (AUC, 0.58; 95% CI, 0.50-0.66) were associated with early postoperative facial nerve outcome. The number of spasm events was not associated with facial nerve outcome. The optimal cutoff value for the threshold was 0.25 mA, and the optimal cutoff for number of mechanical events was 8. If a threshold of greater than 0.25 mA was paired with more than 8 mechanical events, there was a 77% chance of postoperative nerve weakness. Conversely, if a threshold was 0.25 mA or less and there were 8 mechanical events or less, there was 69% chance of normal postoperative nerve function. No parameters were associated with permanent facial nerve injury.

Conclusions and Relevance

Postdissection threshold and the number of mechanical events are associated with immediate postoperative facial nerve function. Accurate prediction of facial nerve function may provide anticipatory guidance to patients and may provide surgeons with intraoperative feedback allowing adjustment in operative techniques and perioperative management.

Improved Nerve Visualization in Head and Neck Surgery Using Mueller Polarimetric Imaging: Preclinical Feasibility Study in a Swine Model

BACKGROUND AND OBJECTIVES

Meticulous dissection and identification of nerves during head and neck surgery are crucial for preventing nerve damage. At present, nerve identification relies heavily on the surgeon's knowledge of anatomy, optionally combined with intraoperative neuromonitoring. Recently, optical techniques such as Mueller polarimetric imaging (MPI) have shown potential to improve nerve identification.

STUDY DESIGN/MATERIALS AND METHODS

With institutional approval, seven 25-35 kg Yorkshire pigs underwent cervical incision in the central neck. Intraoperative images were obtained using our in-house MPI system. Birefringence maps from the MPI system were processed to quantify the values between 0 and 255 from different tissue types; an active contour model was applied to further improve nerve visualization on the corresponding color images.

RESULTS

Among the seven pigs, the vagus nerves and recurrent laryngeal nerves were successfully differentiated with a mean intensity of 130.954 ± 20.611, which was significantly different (P < 0.05) from those of arteries (78.512 ± 27.78) and other surrounding tissues (82.583 ± 35.547). There were no imaging-related complications during the procedure. © 2021 Wiley Periodicals LLC.

CONCLUSIONS

MPI is a potentially complementary intraoperative tool for nerve identification in adjacent tissues.

Comparison of a Handheld Device vs Endotracheal Tube-Based Neuromonitoring for Recurrent Laryngeal Nerve Stimulation

OBJECTIVE

To measure the effect of thyroidectomy difficulty on intraoperative neuromonitoring false loss of signal (LOS) and to compare intraoperative endotracheal tube-based neuromonitoring (ETNM) and Checkpoint palpation-based direct stimulation (pDS) signals with postoperative laryngoscopy. We hypothesized that pDS has higher a positive predictive value for postdissection confirmation of recurrent laryngeal nerve function than ETNM and that this difference is accentuated with increasing thyroidectomy difficulty.

STUDY DESIGN

Prospective single-arm cross-sectional study comparing ETNM and pDS for patients undergoing hemi-, total, or completion thyroidectomy from July 2018 to March 2020.

SETTING

Single-surgeon series at a tertiary care hospital.

METHODS

Percentage concordance and positive and negative predictive values were measured. Each thyroidectomy was assigned a validated thyroidectomy difficulty score, and recorded recurrent laryngeal nerve signals were compared with postoperative vocal fold mobility.

RESULTS

Percentage concordance was 90.09%. Positive and negative predictive values were 0.19 (95% CI, 0.09-0.31) and 1.0 for ETNM and 0.59 (95% CI, 0.35-0.82) and 1.0 for pDS. The difference in positive predictive value was significant (0.40 [95% CI, 0.33-0.47], P < .001). False LOS rates for ETNM and pDS were 13.19% versus 3.30% (9.89% [95% CI, 1.80%-18.62%], P = .0155), 44.11% versus 0% (44.11% [95% CI, 25.80%-60.54%], P < .001), and 73.33% versus 13.33% (60% [95% CI, 24.76%-78.46%], P = .001) for the second through fourth thyroidectomy difficulty score quartiles, respectively. False LOS with ETNM was linearly correlated with increasing difficulty (R² = 0.97).

CONCLUSION

ETNM was subject to high rates of postdissection false LOS that increased with thyroidectomy difficulty score. pDS is a reliable alternative that has higher positive predictive value than ETNM, particularly in more challenging cases such as those with posteriorly fixed thyroid cancers and fibrotic glands.

EVIDENCE LEVEL

2.

Comparison of Sugammadex Dose for Intraoperative Neuromonitoring in Thyroid Surgery: A Randomized Controlled Trial

OBJECTIVES/HYPOTHESIS

To compare effect of 1 and 2 mg/kg of sugammadex on the incidence of intraoperative bucking and intraoperative neuromonitoring (IONM) quality in thyroid surgery.

STUDY DESIGN

Randomized controlled trial.

METHODS

Patients qualified for thyroid surgery with IONM were eligible for this double-blind, randomized, controlled trial. After tracheal intubation with 0.6 mg/kg rocuronium, 1 or 2 mg/kg of sugammadex was administered to patients in group I or II, respectively. The quality of the IONM for the external branch of the superior laryngeal nerve (EBSLN) was evaluated (strong/intermediate/weak). The initial amplitude of electromyography for the vagus nerve (V1) and the recurrent laryngeal nerve (R1) were recorded. Intraoperative bucking movements was recorded.

RESULTS

A total of 102 patients (51 in each group) completed the study. Time from sugammadex administration to initial checking for the EBSLN was not different between group I and II (25.0 ± 7.9 vs. 25.5 ± 9.0 minutes, P = .788). There was no difference in the neuromonitoring quality for the EBSLN between group I and II (strong/intermediate/weak: 46/5/0 vs. 50/1/0, P = .205). The amplitudes of V1 (1,086.3 ± 673.3 μV vs. 1,161.8 ± 727.5 μV, P = .588) and R1 (1,328.2 ± 934.1 μV vs. 1,410.5 ± 919.6 μV, P = .655) were comparable between the groups. Patients who experienced bucking were significantly fewer in the group I than the group II (13.7% vs. 35.3%, P = .020).

CONCLUSION

A dose of 1 mg/kg sugammadex induced less bucking than 2 m/kg while providing comparable IONM quality during thyroid surgery.

LEVEL OF EVIDENCE

2 Laryngoscope, 131:2154-2159, 2021.

Application of carbon nanoparticles combined with intraoperative neuromonitoring in papillary thyroid microcarcinoma surgery

PURPOSES

To improve the lymph node dissection as well as protect parathyroid gland and recurrent laryngeal nerve, the carbon nanoparticles and intraoperative neuromonitoring were applied in papillary thyroid microcarcinoma surgery.

METHODS

Carbon nanoparticles and intraoperative neuromonitoring were used in the experimental group, whereas the control group were not. Routine pathological examination was performed.

RESULTS

The lymph nodes dissected was significantly higher in the experimental group, but the metastatic lymph nodes were not. The number of mistakenly dissected parathyroid gland and postoperative hypoparathyroidism were 3 and 13 in the experimental group respectively, significantly less than 10 and 25 in the control group. The incidences of overall, transient and persistent recurrent laryngeal nerve palsy in the experimental group were 5.5%, 5.5% and 0% respectively, whereas in the control group were 8.6%, 6.9% and 1.7%.

CONCLUSIONS

Carbon nanoparticles can improve lymph node dissection in papillary thyroid microcarcinoma surgery, and the combination of carbon nanoparticles with intraoperative neuromonitoring can reduce surgical complications and improve patient quality of life.

Influence of rocuronium on achieving optimal vagal stimulation during intraoperative nerve monitoring in thyroid surgery

BACKGROUND

In the present study we determine the feasibility of intraoperative neuromonitoring following the administration of a nondepolarizing neuromuscular blocking agent during thyroid operations, as well as the influence of rocuronium on the achievement of optimal vagal stimulation during intraoperative neuromonitoring in thyroid surgery. We further investigate whether accelerometry is a reliable approach to obtaining an ipsilateral vagus signal prior to recurrent laryngeal nerve dissection.

METHODS

Included in the study were 61 thyroidectomized patients whose demographic data, indications, type of surgery, vagus, and recurrent nerve values before and after resection were obtained. We created five groups of patients based on the twitch values recorded during ipsilateral vagus stimulation prior to the recurrent laryngeal nerve dissection: (1) <10%, (2) 11-25%, (3) 26-50%, (4) 51-75% and (5) >75%.

RESULTS

The average electromyography amplitudes of the vagus nerve prior to the determination of the recurrent laryngeal nerve for each group were 552 μV, 463 μV, 543 μV, 513 μV and 551 μV, respectively. No difference between the groups was observed in this regard (p > 0.05).

CONCLUSION

It can be expected that as soon as the effects of neuromuscular blockers on the peripheral muscles begin to abate, it will be possible to obtain the ipsilateral vagus signal prior to recurrent laryngeal nerve dissection at the desired levels. It can be concluded from this study that accelerometry using the pollicis muscle is an unreliable tool for the interpretation of the proper electromyography signals of the vagus nerve prior to the determination of the recurrent laryngeal nerve.

Mechanisms of recurrent laryngeal nerve injury near the nerve entry point during thyroid surgery: A retrospective cohort study

BACKGROUND

The use of intraoperative neuromonitoring (IONM) for visual identification of recurrent laryngeal nerve (RLN) has decreased the rates of RLN injury (RLNI) during thyroid surgery. However, little attention has been paid to RLNI near the nerve entry point (NEP), where most injuries occur. The aim of this study was to determine the mechanism of RLNI near the NEP and to describe the recovery of nerve function.

METHODS

Patients undergoing thyroid surgery were analyzed to identify true loss of signal (LOS) by IONM. Follow-up for vocal cord palsy (VCP) was confirmed by a postoperative laryngoscopy. The risk factors for RLNI, the type of RLNI, the prevalence of VCP and the time for VCP recovery were all recorded and analyzed.

RESULTS

We analyzed 3582 at-risk nerves in 2257 surgical patients. The overall rate of RLNI near the NEP in at-risk nerves was 3.2%. RLNI was more likely to occur in nerves with extralaryngeal bifurcation (p = 0.013). The distribution of RLNI types, in order of frequency, was traction (52.6%; n = 61), compression (38.8%; n = 45), thermal (7.8%; n = 9), and nerve transection (0.9%; n = 1). Complete recovery from VCP was documented in 93.1% (n = 108) of RLNI.

CONCLUSION

Patients with a bifurcated RLN were at a higher risk of RLNI near the NEP than those without bifurcation. Traction and compression injuries occurred most frequently, but would eventually recover. Excessive stretching of the thyroid lobe played a role in RLNIs near the NEP.

Application of Novel Intraoperative Neuromonitoring System Using an Endotracheal Tube With Pressure Sensor During Thyroid Surgery: A Porcine Model Study

OBJECTIVES

The loss of signal during intraoperative neuromonitoring (IONM) using electromyography (EMG) in thyroidectomy is one of the biggest problems. We have developed a novel IONM system with an endotracheal tube (ETT) with an attached pressure sensor instead of EMG to detect laryngeal twitching. The aim of the present study was to investigate the feasibility and reliability of this novel IONM system using an ETT with pressure sensor during thyroidectomy in a porcine model.

METHODS

We developed an ETT-attached pressure sensor that uses the piezoelectric effect to measure laryngeal muscle twitching. Stimulus thresholds, amplitude, and latency of laryngeal twitching evaluated using the pressure sensor were compared to those measured using transcartilage needle EMG. The measured amplitude changes by EMG and the pressure sensor during recurrent laryngeal nerve (RLN) traction injury were compared.

RESULTS

No significant differences in stimulus threshold intensity between EMG and the pressure sensor were observed. The EMG amplitude detected at 0.3 mA, increased with increasing stimulus intensity. When the stimulus was more than 1.0 mA, the amplitude showed a plateau. In a RLN traction injury experiment, the EMG amplitude did not recover even 20 minutes after stopping RLN traction. However, the pressure sensor showed a mostly recovery.

CONCLUSION

The change in amplitude due to stimulation of the pressure sensor showed a pattern similar to EMG. Pressure sensors can be feasibly and reliably used for RLN traction injury prediction, RLN identification, and preservation through the detection of laryngeal muscle twitching. Our novel IONM system that uses an ETT with an attached pressure sensor to measure the change of surface pressure can be an alternative to EMG in the future.

THYROID SURGERY, IONM AND SUGAMMADEX SODIUM RELATIONSHIPS: BENEFITS IN SUGAMMADEX SODIUM USE FOR IONM

Background

It is important to protect recurrent laryngeal nerve (RLN) during thyroid surgery. Thus, intra- operative neuromonitoring (IONM) has got popularity. But, the half life of neuromuscular blocking agents used has a reverse correlation with reliability and effectiveness of IONM. This study aimed to research the effect of Sugammadex Sodium, a specific nemuromuscular blocking agent antagonist, on nerve conduction and IONM.

Materials and methods

Twenty patients who underwent thyroidectomy under IONM followed an enhanced NMB recovery protocol-rocuronium 0.6 mg/kg at anesthesia induction and sugammadex 2 mg/kg at the beginning of operation. To prevent laryngeal nerve injury during the surgical procedures, all patients underwent intraoperative monitoring. At the same time, the measurement of TOF-Watch acceleromyograph of the adductor pollicis muscle response to ulnar nerve stimulation was performed; recovery was defined as a train-of-four (TOF) ratio ≥ 0.9. Age, sex, recurrent laryngeal nerve transmission speeds prior to and after operation, BMI, duration of surgery, the change in nerve transmission after drug administration and complications were analyzed.

Results

The mean age and the mean BMI were 47.6±11.82 years and 28.74±3.20, respectively. The mean operation duration was 52.65±5.51 minutes. There was no difference in either right or left RLN monitoring values before and after surgery. Following the drug injection, the TOF guard measurements on the 1^st, 2^nd, 3^rd and 4^th minutes were 23.5±4.90; 69.5±6.86; 88±4.1 and 135.9±10.62, respectively.

Conclusion

Neuromuscular blocking antagonist use and monitoring nerve transmission speed with TOF-guard can provide a safer resection.

Should intraoperative nerve monitoring be used routinely in primary thyroid surgeries?

Objective:

This study presents the effects of intraoperative nerve monitoring on RLN injuries in patients who underwent primary surgery for benign thyroid pathology.

Methods:

We retrospectively evaluated the data of 273 patients who had primary thyroidectomy due to benign thyroid pathology between January 2012 and July 2017. The patients were classified into two groups. Group-1 consists of patients whose nerves were monitored. We separated the patients whose nerves were not monitored into Group-2.

Results:

There were 140 and 133 patients in Groups 1 and 2, respectively. Regarding the age, gender and surgical indication between the groups, statistically significant difference was not found (P > 0.05). In Group-1, transient paralysis developed in four patients (2.9%). The permanent paralysis developed in one patient (0.7%). In Group-2, transient paralysis developed in nine patients (6.8%). The permanent paralysis developed in four patients (3%). When the groups were evaluated, there was statistically significant difference in terms of transient and permanent paralysis (P=0.01, P =0.001, respectively).

Conclusions:

In view of the negative effects of RLN injury on the patient, we think that intraoperative nerve monitoring should be used routinely in benign thyroid surgeries.

Development of a Novel Intraoperative Neuromonitoring System Using an Accelerometer Sensor in Thyroid Surgery: A Porcine Model Study

Objectives.

The sensitivity and positive predictive value of widely used intraoperative neuromonitoring (IONM) using electromyography (EMG) of the vocalis muscle in thyroid surgery are controversial. Thus, we developed a novel IONM system with an accelerometer sensor that uses the piezoelectric effect instead of EMG to detect laryngeal twitching. The objective of this study was to evaluate the feasibility and safety of this novel IONM system during thyroid surgery in a porcine model.

Methods.

We developed an accelerometer sensor that uses the piezoelectric effect to measure laryngeal twitching in three dimensions. This novel accelerometer sensor was placed in the anterior neck skin (transcutaneous) or postcricoid area. Stimulus thresholds, amplitude, and latency of laryngeal twitching measured using the accelerometer sensor were compared to those measured through EMG of the vocalis muscle.

Results.

The amplitudes of the accelerometer sensor at the anterior neck and postcricoid area were significantly lower than those of EMG because of differences in the measurement method used to evaluate laryngeal movement. However, no significant differences in stimulus thresholds between the EMG endotracheal tube and transcutaneous or postcricoid accelerometer sensors were observed.

Conclusion.

Accelerometer sensors located at the anterior neck or postcricoid area were able to identify laryngeal twitching. The stimulus intensity measured with these sensors was equivalent to that from conventional vocalis EMG. Our novel IONM system with an accelerometer sensor that checks changes in surface acceleration can be an alternative to EMG of the vocalis muscle for IONM in the future.

Methodological Quality of Systematic Reviews of Intraoperative Neuromonitoring in Thyroidectomy: A Systematic Review

Importance

Systematic reviews and meta-analyses are considered the best evidence for clinical decision making. Many reviews of intraoperative neuromonitoring (IONM) in thyroidectomy have conflicting results, owing in large part to methodological quality.

Objective

To assess the methodological quality and the causes of heterogeneous results of systematic reviews that compare routine IONM vs visual identification of the recurrent laryngeal nerve (RLN) in patients undergoing thyroidectomy.

Data Sources

A systematic search was performed of MEDLINE (PubMed), Embase, the Cochrane Library, LILACS (Literatura Latino Americana e do Caribe em Ciências da Saúde), Web of Science, and Google from January 1, 1968, through June 30, 2018. Data were analyzed from July 17 to November 30, 2018.

Study Selection

Studies that mentioned performance of a systematic review/meta-analysis during the search period.

Data Extraction and Synthesis

Data including study characteristics, type of patients, numbers of nerves at risk, and temporary and definitive RLN paralysis by group were extracted. Data about methodological characteristics, type of statistical analysis and summary estimator, endorsement of systematic review/meta-analysis guidelines, heterogeneity, publication bias, funding, conflict of interest, and statistical analysis were also recorded. The methodological quality was measured with the AMSTAR2 (A Measurement Tool to Assess Systematic Reviews) tool by 2 independent evaluators.

Main Outcomes and Measures

Methodological quality.

Results

The search identified 13 systematic reviews that included patients who underwent open or minimally invasive thyroidectomy, second operations, and a mixture of low- and high-risk procedures. The mean compliance with the AMSTAR2 overall criteria was 53% (range, 11%-83%); with critical criteria, 71% (range, 50%-94%). The percentage of nerves at risk from RCTs was 4.8%. The mean (SD) crude rate of definitive RLN paralysis was 0.81% (0.22%; median, 0.75% [range, 0.53%-1.30%]) in the monitoring group and 1.14% (0.56%; median, 0.96% [range, 0.57%-2.56%]) in the control group.

Conclusions and Relevance

A substantial number of systematic reviews of IONM in thyroidectomy have conflicting results, but their mean methodological quality is critically low. Design of a systematic review should comply with methodological standards and recommendations to offer relevant and practical information for decision making.

Vagal schwannomas of the head and neck: A comprehensive review and a novel approach to preserving vocal cord innervation and function

BACKGROUND

Schwannomas, benign tumors arising from neurolemmocytes, are the most common type of peripheral nerve tumors. Extracranial schwannomas are most often found in the parapharyngeal space, commonly involving the vagus nerve to cervical sympathetic trunk. Vagal schwannomas present several unique clinical and therapeutic challenges.

METHODS

A comprehensive literature review was conducted on 197 articles reporting 235 cases of cervical vagal schwannomas. Presenting symptoms, treatment approach, and postoperative outcomes were recorded and analyzed.

RESULTS

Vagal schwannomas commonly present as asymptomatic neck masses. When they become symptomatic, surgical resection is the standard of care. Gross total resection is associated with higher postoperative morbidity compared to subtotal resection. Initial reports using intraoperative nerve monitoring have shown improved nerve preservation. Recurrence rates are low.

CONCLUSION

The combination of intermittent nerve mapping with novel continuous vagal nerve monitoring techniques may reduce postoperative morbidity and could represent the future standard of care for vagal schwannoma treatment.

Usefulness of intraoperative nerve monitoring in esophageal cancer surgery in predicting recurrent laryngeal nerve palsy and its severity

BACKGROUND

Recurrent laryngeal nerve (RLN) palsy is a critical postoperative complication in esophageal cancer surgery. However, intraoperative prediction of its occurrence and severity is difficult. In this prospective study, we evaluated the usefulness of intraoperative nerve monitoring (IONM) in predicting RLN palsy and its severity.

METHODS

Twenty patients who underwent subtotal esophagectomy with 3-field lymph node dissection were enrolled. Intraoperative electromyography (EMG) amplitudes of the vocal cords were measured by IONM at RLN and vagus nerve (VN) stimulation. Comparison was made between the vocal cords with RLN palsy and those without palsy and additionally between the vocal cords with transient RLN palsy and those with persistent palsy.

RESULTS

Among 40 vocal cords in 20 patients, 26 were intact and 14 were paralyzed. Seven had transient, six had permanent palsy. The mean EMG amplitude of intact vocal cords was significantly larger than that of paralyzed ones at VN (506 ± 498 µV vs. 258 ± 226 µV, p = 0.022) and RLN stimulation (642 ± 530 µV vs. 400 ± 308 µV, p = 0.038). The cut-off value for postoperative palsy were 419 µV [positive predictive value (PPV): 48.0%, negative predictive value (NPV): 84.6%] at VN and 673 µV (PPV: 44.8%, NPV: 90.9%) at RLN stimulation. The mean EMG amplitude of persistently paralyzed vocal cords tended to be small, compared with that of recovered ones at both VN (168 ± 173 µV vs. 336 ± 266 µV, p = 0.11) and RLN (244 ± 223 µV vs. 536 ± 344 µV, p = 0.051) stimulation.

CONCLUSION

The absolute EMG amplitude of IONM might be helpful to predict the occurrence and severity of RLN palsy after esophageal surgery although the predictive value is low.

Transcranial motor-evoked potentials of laryngeal muscles for intraoperative neuromonitoring of the vagus nerve during thyroid surgery

PURPOSE

The aim of this study was to elucidate normative features of vagal motor-evoked potentials (MEPs) induced by transcranial electrical stimulation (TES) and to determine the influence of functional decline of the recurrent laryngeal nerve (RLN) on vagal MEPs during thyroid surgery.

METHODS

A total of 54 patients undergoing elective thyroid surgery under general anesthesia were enrolled in this study. Vagal MEPs induced by TES were measured from the vocal cord using one of two types of electrodes (wire type or wide and flat type) mounted on an endotracheal tube. We investigated the effects of stimulation intensity and train pulse number on vagal MEP amplitude, the time course of vagal MEP amplitude during surgery, and the effects of functional decline of the RLN on vagal MEPs.

RESULTS

The success rate of vagal MEP monitoring with wide- and flat-type electrodes was significantly higher than that with wire-type electrodes. Reliable vagal MEPs were obtained at a stimulation intensity of approximately 300 V with 3 or more pulses in 91% of the patients without preoperative RLN palsy (RLNP), and the amplitude was augmented with increasing stimulation intensity and train pulse number. Vagal MEP amplitude decreased during thyroid surgery and then partially recovered at the end of surgery. Vagal MEP amplitude recorded from the electrode ipsilateral to preoperative RLNP was significantly lower than that on the contralateral intact side.

CONCLUSION

Vagal MEPs induced by TES can be obtained with a high success rate during thyroid surgery and would reflect functional status of the RLN.

Routine Intraoperative Neuromonitoring of the Recurrent Laryngeal Nerve to Facilitate Complete Resection and Ensure Safety in Thyroid Cancer Surgery

Routine use of intraoperative neuromonitoring (IONM) in thyroid cancer surgery is controversial. We aimed to investigate whether it improves the completeness of thyroidectomy and ensures safety. This retrospective study included 380 thyroid cancer patients who underwent thyroidectomy, by one surgeon, between July 2006 and November 2015. Patients were grouped according to the surgeon's adaptation of IONM, as follows: none (period 1; n = 92), early (period 2; n = 141), and late (period 3; n = 147). The operative time and rates of vocal cord palsy were determined. Surgical completeness was assessed by technetium-99m imaging of the thyroid remnant and serum thyroglobulin measurement before ablation. The rate of recurrent laryngeal nerve (RLN) palsy showed a decreasing trend over time. No permanent RLN palsies occurred in nerves not invaded by tumor after routine IONM was introduced. Technetium-99m uptake (periods 1–3, 0.62 vs 0.32 vs 0.20; P < 0.01) and thyroglobulin levels (periods 1 and 2, 37.93 vs 8.98 ng/mL, respectively; P = 0.034; period 3, 9.10 ng/mL) progressively decreased. The mean thyroglobulin level dropped significantly after introduction of routine IONM. We conclude that routine IONM during thyroid cancer surgery improves surgical completeness and might prevent permanent RLN palsy over time.

The incidence of vocal fold motion impairment after primary thyroid and parathyroid surgery for a single high-volume academic surgeon determined by pre- and immediate post-operative fiberoptic laryngoscopy

BACKGROUND

Vocal fold motion impairment (VFMI) is a well-recognized complication of thyroid and parathyroid surgery. Preoperative counseling requires a thorough understanding of the incidence, risk factors, and value of early diagnosis of postoperative VFMI. Our objective is to describe the incidence of and risk factors for VFMI for a single high-volume academic surgeon, and to assess the utility of immediate postoperative fiberoptic laryngoscopy (FOL) in early diagnosis of VFMI.

METHODS

Retrospective cohort study of patients undergoing primary thyroid and parathyroid procedures by a single high-volume surgeon at an academic tertiary care center. All patients underwent preoperative and immediate postoperative FOL. The primary outcome was incidence of VFMI, either temporary (<1 year) or permanent (1 year or more). The unit of analysis was number of recurrent laryngeal nerves (RLN) at risk. Risk factors for VFMI were analyzed using logistic regression, reporting unadjusted and adjusted odds ratios (OR and aOR) and 95% confidence intervals (CI).

RESULTS

The study population comprised 1547 patients undergoing 1580 procedures for a total of 2527 nerves at risk, excluding the 27 nerves found to have motion impairment on preoperative FOL. Sixty-seven new incidents of VFMI were identified on postoperative FOL, with an additional six new incidents detected after voice complaints prompted FOL upon follow-up. Thus, the incidence of postoperative VFMI was 2.9% of RLNs at risk (73 of 2527). The sensitivity and negative predictive value of immediate postoperative FOL were 92% and 99.8% respectively. Permanent VFMI occurred in 9 cases (0.4%), 3 of which were from intentional RLN transection for malignancy. Odds of VFMI were significantly lower after parathyroidectomy (aOR = 0.1, 95%CI = 0.01-0.8 compared with hemithryoidectomy) and higher with central neck dissection (aOR = 2.4, 95CI = 1.0-5.9). Among cases of malignancy, odds of VFMI increased significantly with increasing T-stage (adjusted p_trend<0.001).

CONCLUSION

VFMI is rare and usually temporary after primary thyroid and parathyroid procedures, with increased risk associated with larger primary malignancies and the inclusion of central neck dissection. Immediate postoperative FOL is useful for early detection of VFMI that may allow for clear definition of temporary and permanent immobility rehabilitation especially if there is evidence to support early intervention.

Evaluating the introduction of intraoperative neuromonitoring of the recurrent laryngeal nerve in thyroid and parathyroid surgery

INTRODUCTION

Paresis of the recurrent laryngeal nerve (RLN) is a complication of thyroid surgery. Neuromonitoring as is gaining acceptance among surgeons. The aim of the study was to assess the number of technical problems in the initial phase of intraoperative neuromonitoring (IONM) use and the specificity, sensitivity, positive predictive value and negative predictive value of neuromonitoring. The number of cases of postoperative paresis (transient and permanent) was assessed.

MATERIAL AND METHODS

The prospective analysis included 101 thyroid operations with IONM (190 RLNs at risk of injury) in the period from January to April, 2012. Demographic data, rate of RLN identification, sensitivity, specificity and predictive value of the method, the duration of the procedurę and the percentage of RLN paresis were considered.

RESULTS

The RLN was identified in 92% of the cases. Technical problems were observed in 12.98%, of which 61% were due to incorrect positioning of the endotracheal tube electrodes in relation to the vocal cords. The sensitivity, specificity, negative and positive predictive value and the accuracy of the method were respectively 71%, 98%, 62.5%, 98.9% and 97%. Early nerve injury occurred in 3.7% of the cases; 2.6% were temporary paresis and 1.1% permanent.

CONCLUSIONS

During the initial stages of implementing IONM we experienced technical problems that required correction in every tenth patient. The positive predictive value was relatively low; nevertheless, good results in terms of the rate of accurate identification of the RLN as well as the low rate of RLN paresis support the use of this method.

Real-time, label-free, intraoperative visualization of peripheral nerves and micro-vasculatures using multimodal optical imaging techniques

Accurate, real-time identification and display of critical anatomic structures, such as the nerve and vasculature structures, are critical for reducing complications and improving surgical outcomes. Human vision is frequently limited in clearly distinguishing and contrasting these structures. We present a novel imaging system, which enables noninvasive visualization of critical anatomic structures during surgical dissection. Peripheral nerves are visualized by a snapshot polarimetry that calculates the anisotropic optical properties. Vascular structures, both venous and arterial, are identified and monitored in real-time using a near-infrared laser-speckle-contrast imaging. We evaluate the system by performing in vivo animal studies with qualitative comparison by contrast-agent-aided fluorescence imaging.

Intraoperative neuromonitoring in thyroid surgery: Is the two-staged thyroidectomy justified?

BACKGROUND

The aim of this study was to evaluate the diagnostic accuracy of intraoperative neuromonitoring (IONM) in predicting postoperative nerve function during thyroid surgery and its consequent ability to assist the surgeon in intraoperative decision making.

MATERIALS AND METHODS

A total of 2365 consecutive patients were submitted to thyroidectomy by the same surgical team. Group A included 1356 patients (2712 nerves at risk) in whom IONM was utilized, and Group B included 1009 patients (2018 nerves at risk) in whom IONM was not utilized.

RESULTS

In Group A, loss of signal (LOS) was observed in 37 patients; there were 29 true positive, 1317 true negative, 8 false positive, and 2 false negative cases. Accuracy was 99.3%, positive predictive value was 78.4%, negative predictive value was 99.8%, sensitivity was 93.6%, and specificity was 99.4%. A total of 29 (2.1%) cases of unilateral paralysis were observed, 23 (1.7%) of which were transient and 6 (0.4%) of which were permanent. Bilateral palsy was observed in two (0.1%) cases requiring a tracheostomy. In Group A, 31 (2.3%) injuries were observed, 25 (1.8%) of which were transient and 6 (0.4%) of which were permanent. In Group B, 26 (2.6%) unilateral paralysis cases were observed, 20 (2%) of which were transient and 6 (0.6%) of which were permanent; bilateral palsy was observed in 2 (0.2%) cases. In Group B, 28 (2.8%) injuries were observed, 21 (2.1%) of which were transient and 7 (0.7%) of which were permanent. Differences between the two groups were not statistically significant.

CONCLUSIONS

Our results show that IONM has a very high sensitivity and negative predictive value, but also good specificity and positive predictive value. For these reasons, in selected patients with LOS, the surgical strategy should be reconsidered. However, patients need to be informed preoperatively about potential strategy changes during the planned bilateral surgery. Future larger and multicenter studies are needed to confirm the benefits of this therapeutic strategy.

Intraoperative nerve monitoring reduces recurrent laryngeal nerve injury in geriatric patients undergoing thyroid surgery

OBJECTIVE

This research was aimed to investigate whether the intraoperative nerve monitoring (IONM) can reduce the incidence of recurrent laryngeal nerve (RLN) injury in geriatric patients undergoing thyroid surgery.

METHODS

This retrospective cohort study included 522 geriatric patients undergoing thyroid surgery between January 2013 and June 2016 in the Sun Yat-sen Memorial Hospital. Patients with IONM during the surgery (n = 340) were compared with patients without IONM (n = 212). RLN injury was verified by direct or indirect laryngoscope and relative factors for injury would be retrospectively analyzed.

RESULTS

The use of IONM group showed significant reduction in both total and transient RLN injury incidence, when compared with that in control group (1.76 versus 4.72%, p = .01 and 1.32 versus 3.67%, p = .03, respectively). However, the permanent RLN injury incidence did not show difference between the two groups (p = .3).

CONCLUSIONS

Our finding showed the use of IONM resulted in significantly reduction in RLN injury incidence. The technology of IONM is safe and convenient to detect, track and monitor the complete function of RLN and to provide the guidance for the surgeons during the thyroid surgery in geriatric patients, who are at high risk of RLN injury.

Measuring Decision-Making During Thyroidectomy: Validity Evidence for a Web-Based Assessment Tool

BACKGROUND

Errors in judgment during thyroidectomy can lead to recurrent laryngeal nerve injury and other complications. Despite the strong link between patient outcomes and intraoperative decision-making, methods to evaluate these complex skills are lacking. The purpose of this study was to develop objective metrics to evaluate advanced cognitive skills during thyroidectomy and to obtain validity evidence for them.

METHODS

An interactive online learning platform was developed ( www.thinklikeasurgeon.com ). Trainees and surgeons from four institutions completed a 33-item assessment, developed based on a cognitive task analysis and expert Delphi consensus. Sixteen items required subjects to make annotations on still frames of thyroidectomy videos, and accuracy scores were calculated based on an algorithm derived from experts' responses ("visual concordance test," VCT). Seven items were short answer (SA), requiring users to type their answers, and scores were automatically calculated based on their similarity to a pre-populated repertoire of correct responses. Test-retest reliability, internal consistency, and correlation of scores with self-reported experience and training level (novice, intermediate, expert) were calculated.

RESULTS

Twenty-eight subjects (10 endocrine surgeons and otolaryngologists, 18 trainees) participated. There was high test-retest reliability (intraclass correlation coefficient = 0.96; n = 10) and internal consistency (Cronbach's α = 0.93). The assessment demonstrated significant differences between novices, intermediates, and experts in total score (p < 0.01), VCT score (p < 0.01) and SA score (p < 0.01). There was high correlation between total case number and total score (ρ = 0.95, p < 0.01), between total case number and VCT score (ρ = 0.93, p < 0.01), and between total case number and SA score (ρ = 0.83, p < 0.01).

CONCLUSION

This study describes the development of novel metrics and provides validity evidence for an interactive Web-based platform to objectively assess decision-making during thyroidectomy.

Two-stage thyroidectomy in the era of intraoperative neuromonitoring

Background

The use of intraoperative neuromonitoring (IONM) provides surgeons with real time information about recurrent laryngeal nerves (RLN) functional integrity. Hence, allowing them to modify the initially scheduled bilateral procedure, to a two-stage thyroidectomy in cases of loss of signal (LOS) on the first side of resection resulting in minimization of bilateral RLN injury. The purpose of our study was to present our results since the implementation of the above mentioned process in both malignant and benign thyroid disease.

Methods

We conducted a retrospective, observational cohort study of prospectively collected data from all patients who underwent a scheduled total thyroidectomy with or without neck dissection in our Department over the last 4 years [2013-2016]. From the 1,138 patients who received surgical treatment during that period, 284 were excluded since they did not meet the criteria. Exclusion criteria involved previous neck operation, parathyroid surgery, pre-existing vocal cord palsy (VCP) and unilateral surgery. A total of 854 patients were eligible for our study. All patients were subjected to pre- and postoperative indirect laryngoscopy by the same experienced ENT specialist team and all the surgeries were performed by the same experienced team. The whole procedure followed the International Neural Monitoring Study Group's (INMSG) Guideline Statement.

Results

We experienced 70 cases (70/854, 8.2%) with postoperative VCP. Two of them (0.23%) had permanent VCP and the rest of those patients (7.97%) experienced transient VCP. Twenty-three (2.7%) patients were candidates for staged thyroidectomy after LOS on the first side of resection, including ten patients with papillary or medullary thyroid carcinoma and one with toxic multinodular goiter (MNG). Of those patients, 22 incidents of VCP (95.7%) have recovered within two months and one of them persisted for more than six months (permanent VCP). We did not experience any permanent bilateral RLN palsy after the implementation of the staged procedure.

Conclusions

Staged thyroidectomy seems a very attractive and promising procedure for both patient and surgeon, since it nearly eliminates one of the most fearful complications in thyroid surgery. We suggest staged thyroidectomy in all cases with first side of resection signal loss, even in malignancies, since the benefits are much more than the disabilities in a patient's morbidity and quality of life.

Impact of EMG Changes in Continuous Vagal Nerve Monitoring in High-Risk Endocrine Neck Surgery

Background

Continuous vagal intraoperative neuromonitoring (CIONM) of the recurrent laryngeal nerve (RLN) may reduce the risk of RLN lesions during high-risk endocrine neck surgery such as operation for large goiter potentially requiring transsternal surgery, advanced thyroid cancer, and recurrence.

Methods

Fifty-five consecutive patients (41 female, median age 61 years, 87 nerves at risk) underwent high-risk endocrine neck surgery. CIONM was performed using the commercially available NIM-Response 3.0 nerve monitoring system with automatic periodic stimulation (APS) and matching endotracheal tube electrodes (Medtronic Inc.). All CIONM events (decreased amplitude/increased latency) were recorded.

Results

APS malfunction occurred on three sides (3 %). A total of 138 CIONM events were registered on 61 sides. Of 138, 47 (34 %) events were assessed as imminent (13 events) or potentially imminent (34 events) lesions, whereas 91 (66 %) were classified as artifacts. Loss of signal was observed in seven patients. Actions to restore the CIONM baseline were undertaken in 58/138 (42 %) events with a median 60 s required per action. Four RLN palsies (3 transient, 1 permanent) occurred: one in case of CIONM malfunction, two sudden without any significant previous CIONM event, and one without any CIONM event. The APS vagus electrode led to temporary damage to the vagus nerve in two patients.

Conclusions

CIONM may prevent RLN palsies by timely recognition of imminent nerve lesions. In high-risk endocrine neck surgery, CIONM may, however, be limited in its utility by system malfunction, direct harm to the vagus nerve, and particularly, inability to indicate RLN lesions ahead in time.

Comparative analysis between a bipolar vessel sealing and cutting device and the tie and suture technique in thyroidectomy: A randomized clinical trial

BACKGROUND

Advanced bipolar and ultrasonic devices have shown significant reduction in the surgical time of thyroid operations. This randomized, controlled trial assessed if operative time and other relevant outcomes are different for thyroidectomies performed either with a second-generation advanced bipolar device or traditional tie and suture technique.

METHODS

Forty-one patients were randomized into 2 groups (advanced bipolar device and traditional tie and suture). Secondary end points included estimated blood loss, postoperative hemorrhage or hematoma requiring operative reintervention, recurrent laryngeal nerve injury, hypoparathyroidism, pain intensity, number of ligatures, analgesia usage, and loss of signal during recurrent laryngeal nerve monitoring.

RESULTS

Preoperative characteristics were similar between both groups. Mean operative time in the advanced bipolar device group was reduced by 32.5 minutes compared with the traditional tie and suture group (P = .006). Intraoperative blood loss was similar in both groups. Four patients presented postoperative vocal cord dysmotility, 3 in the traditional tie and suture group and 1 in the advanced bipolar device group (P = ns). Two of these 4 patients also had a >50% amplitude decrease during continuous intraoperative neuromonitoring, 1 in each group. Pain intensity, 12 hours after operation, was significantly greater in the traditional tie and suture group (P = .015), even though pain medication requirements during the initial 24 hours after operation were similar between groups (P = .97). There were no cases of postoperative hemorrhage or hematoma requiring reintervention. Postoperative, symptomatic hypocalcemia occurred in 6 patients, 4 in the traditional tie and suture, and 2 in the advanced bipolar device group. One of them developed permanent hypocalcemia.

CONCLUSION

The use of an advanced bipolar device in thyroid operation reduces operative time by >30 minutes, with a similar postoperative outcome profile when compared with the traditional tie and suture technique.