Supramaximal neurostimulation with laryngeal palpation to predict postoperative vocal fold mobility

Value of Neurostimulation Plus Laryngeal Palpation to Predict Postoperative Vocal Fold Motility

BACKGROUND

The aim of this study was to evaluate the reliability of intraoperative neuromonitoring through recurrent laryngeal nerve stimulation and simultaneous laryngeal palpation (NSLP) in predicting postoperative vocal cord palsy and in providing useful information in the decision to perform a staged surgery in initially planned total thyroidectomy.

MATERIALS AND METHODS

A retrospective review was performed involving 552 patients for whom a total thyroidectomy was planned. In all patients, preoperative and postoperative laryngoscopy was performed. The incidence of vocal cord palsy was calculated on 1104 nerves at risk.

RESULTS

Sensitivity and specificity of NSLP were 0.9411 and 0.9925 respectively. The positive predictive value was 0.7804, the negative predictive value was 0.9981, the false positive rate was 0.8%. In 41 patients (7.4%) the initial surgical strategy was changed into a staged procedure. Nine patients (21.9%) were false positive, 32 patients (78.1%) were true positive. Finally, a two-stage thyroidectomy was performed in 27 of 41 patients.

CONCLUSIONS

High sensitivity and specificity confirm the validity of NSLP in predicting postoperative vocal cord palsy and in driving a possible staged thyroidectomy, both in benign thyroid disease and in differentiated thyroid carcinoma.

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.

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.

Neuromuscular blockade management for intraoperative neural monitoring

This article reviews the literature on development of neuromuscular blockade management in thyroid surgery with intraoperative neural monitoring (IONM) in the past decade. Neuromuscular blockade management includes the choice of neuromuscular blocking agents (NMBAs) and reversal of neuromuscular blockade by sugammadex. A series of animal study and clinical trials showed NMBAs effect on IONM in thyroid surgery. We summarized five NMBA regimens for IONM: (a) relaxant-free regimen, (b) depolarizing NMBA-succinylcholine, (c) titration of nondepolarizing NMBA, and (d) rocuronium combined with sugammadex. The proper management of neuromuscular blockade during IONM has greatly developed over the past decade. The misuse of NMBAs is associated with false IONM interpretations to surgeons. A detailed understanding of NMBAs and neuromuscular blockade management by sugammadex may optimize IONM quality in patients receiving monitored thyroid surgery.

Recurrent laryngeal nerve injury assessment by intraoperative laryngeal ultrasonography: a prospective diagnostic test accuracy study

Introduction

Recurrent laryngeal nerve injury is one of the major complications related to thyroid surgery. Intraoperative recurrent laryngeal nerve functional status monitoring is becoming a standard part of thyroid surgery. However, the current methods for intraoperative nerve functional status assessment are associated with a demand for specialized devices and increased costs.

Aim

To assess the validity of a new method – intraoperative laryngeal ultrasonography – for prediction of recurrent laryngeal nerve injury.

Material and methods

This prospective diagnostic test accuracy study included 112 patients undergoing thyroid surgery in Vilnius University Hospital Santaros Clinics. Neurostimulation combined with laryngeal ultrasonography and laryngeal palpation was performed intraoperatively to evaluate recurrent laryngeal nerve functional status. Recurrent laryngeal nerve injury was confirmed by laryngoscopy, which was performed on the first postoperative day and considered to be the gold standard method.

Results

Data on 112 consecutive patients and 200 nerves at risk were collected. The temporary vocal cord palsy rate was 5.4% per patient and 3% per nerve at risk. No permanent palsy or bilateral injury cases were registered in the study cohort. Laryngeal ultrasound sensitivity counted per nerve at risk was 83.3%, specificity 97.2%, accuracy 96.4%, positive predictive value 62.5% and negative predictive value 99%.

Conclusions

Laryngeal ultrasonography is a feasible new technique for accurate intraoperative recurrent laryngeal nerve injury evaluation.

Some posterior branches of extralaryngeal recurrent laryngeal nerves have motor fibers

OBJECTIVES/HYPOTHESIS

Anatomical variations of the recurrent laryngeal nerve (RLN), such as extralaryngeal branching, are a well-known risk factor for RLN injury during thyroid surgery. This study aimed to analyze the surgical anatomy and to investigate the existence of posterior branch motor fibers of extralaryngeal RLNs.

STUDY DESIGN

Prospective consecutive observational study.

METHODS

This was a prospective cohort study of 366 patients between January 2014 and February 2016. Operative data included the type of operation, incidence of nerve bifurcation, the distances among anatomical landmarks. The motor fibers were evaluated using neurostimulation with laryngeal palpation.

RESULTS

A total of 667 RLNs at risk were analyzed in this study, and of these 103 (14.5%) nerves were bifurcated or trifurcated before the laryngeal entry point (LEP). More extralaryngeal branched RLNs were observed on the right side than on the left (17.5% vs. 13.3%, P = .294). The mean distance of the LEP point of division was longer on the left side (16.2 ± 6.7 mm) than on the right (14.7 ± 5.9 mm, P = .132). All branched RLNs had a palpable laryngeal twitch when stimulating anterior branches. When stimulating posterior branches, 28.2%(29/103) of branched RLNs showed palpable laryngeal twitch. Overall incidence of posterior motor branch in total RLNs was 4.3% (29/667).

CONCLUSIONS

The motor fibers of the RLN are all located in the anterior branch, whereas some posterior branches have motor function. Identification of all of the branches of the RLN may be mandatory to decrease the risk of postoperative nerve injury.

LEVEL OF EVIDENCE

4. Laryngoscope, 127:2678-2685, 2017.