Warning criterion to predict recurrent laryngeal nerve injury with percentage reduction of the amplitude of V2/R2d in neuromonitoring thyroidectomy

Noticeable effect of lower baseline amplitude on the predictive accuracy of intraoperative amplitude changes for postoperative vocal cord palsy: a prospective cohort study

BACKGROUND

To explore the effect of lower baseline amplitude on its predictive accuracy of postoperative vocal cord paralysis (VCP) in monitored thyroid surgery.

MATERIALS AND METHODS

Clinical and electrophysiological data were collected during thyroid surgeries performed between November and December 2021 at China-Japan Union Hospital. Univariate/multivariate regression analysis were applied to these data to examine a possible correlation. A receiver operating characteristic curve was used to evaluate predictive efficacy.

RESULTS

A total of 631 nerves-at-risk (NAR) were identified in 460 patients who were divided into two groups according to postoperative development of VCP. The VCP group included a higher percentage of NAR with V1<1000 (68.2 vs. 40.7%, respectively; P =0.014) and NAR with R1<1400 (77.3 vs. 47.0%, respectively; P =0.005) compared with the non-VCP group. Multivariate regression analysis further identified V1<1000 [odds ratio (OR)=2.688, P =0.038], R1<1400 (OR=3.484, P =0.018) as independent risk factors for postoperative temporary VCP. The receiver operating characteristic curve showed the AUC value of V signal decline for predicting VCP was 0.87. The diagnostic efficiency of R signal decline reached as high as 0.973. A multivariate logistic regression analysis identified independent risk factors for V1<1000 and these included: higher BMI (OR=1.072, P =0.013), hypertension (OR=1.816, P =0.015), smoking (OR=1.814, P =0.031), and male sex (OR=2.016, P =0.027).

CONCLUSION

In our cohort, lower baseline amplitude was an independent risk factor for developing transient postoperative VCP. It also affected the predictive efficacy of intraoperative amplitude changes on VCP. Higher BMI, hypertension, smoking, and male sex may also be closely associated with lower initial amplitude. Thus, maintaining a higher initial amplitude is critical for patient safety during thyroid surgery.

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.