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Title: Evaluation of the clinical value of intraoperative neural monitoring of the recurrent laryngeal nerves in thyroid surgery


Aims: To assess the usefulness of the neuromapping technique in intraoperative localization of the recurrent laryngeal nerve (RLN) and establishing the differential diagnosis of both the type and site of nerve lesion in case of loss of signal (LOS). To validate the diagnostic accuracy of intraoperative RLN neural monitoring in thyroid surgery.Material and methods: A prospective study was conducted in 2011 – 2013 and comprised of 500 patients qualified for total thyroidectomy with intraoperative neural monitoring of the RLNs (1000 nerves at risk). For intraoperative neural monitoring of the RLNs, the surface electromyography of the vocalis muscles was done according to guidelines formulated by the International Neural Monitoring Study Group (INMSG). The study endpoints were: percentage of the RLNs identified with the neuromapping technique prior to visual nerve identification, descriptive characteristics of the type and site of RLN lesion in case of intraoperative LOS, and diagnostic accuracy of the intraoperative neural monitoring of the RLNs using surface electromyography of vocalis muscles in thyroid surgery. All patients had pre- and postoperative vocal folds assessment during 6 months follow-up. The Receiver Operating Characteristics (ROC) was calculated for evaluation of diagnostic accuracy of intraoperative neural monitoring.Results: The application of the neuromapping technique allowed for localization of 921 (92.1%) RLNs before their visual identification. Branched RLNs were found in 245 (24.5%) cases. Among 25 patients with LOS and corresponding vocal fold paresis found in postoperativelaryngoscopy (2.5%), intraoperative RLN neural mapping allowed for identification of the segmental type of nerve injury (type I) in 11 cases and the global type of injury (type II) in 14 cases. In 3 of 11 patients with LOS found after removal of the initially dissected thyroid lobe, staged thyroidectomy was done, whereas the remaining 8 patients had one-stage limited contralateral thyroid lobe surgery to minimize the risk of bilateral vocal folds’ paresis.The prevalence of RLN injury was significantly higher for right-sided as opposed to left-sided operations (3.8% vs. 1.2%, p=0,016), odds ratio 3.34 (95% CI: 1.73 – 6.48; p<0.001) and in cases of branched versus non-branched nerves (4.9% vs. 1.7%, p=0.011), odds ratio 2.99 (95% CI: 1.33 – 6.70; p=0.008), whereas it was significantly lower for successful RLN identification with the neuromapping technique versus visual identification of the nerve, odds ratio 0.33 (95% CI: 0.12 – 0.90; p=0.030).The following diagnostic accuracy values were calculated for the criterion recommended by INMSG (V2 amplitude ≤ 100 μV): sensitivity 92.0% (95% CI: 74.0% - 99.0%), specificity 99.3% (95%CI: 98.5% – 99.7%), positive predictive value 76.7% (95% CI: 57.3% - 90.3%), and negative predictive value 99.8% (95% CI: 99.3% - 100.0%).Conclusions: Application of the neuromapping technique allows for localization of 90% of the RLNs before their visualization in the operative field. In case of LOS, the use of the neuromapping technique is helpful in differentiation of the type of nerve lesion, in clarification of the exact mechanisms leading to nerve injury, and in prognostication of regenerative potential of the nerve. Adherence to the standardized protocol recommended by INMSG allows for optimizing predictive values of intraoperative neural monitoring in prognostication of postoperative RLN function. Negative predictive value of the method equal to 99.8% allows for safe continuing of planned bilateral thyroid surgery in case of intact neural monitoring signal after unilateral thyroid lobectomy. Positive predictive value of the method equal to 76.7% makes it a rationale to stage planned total thyroidectomy in case of LOS after unilateral thyroid lobectomy in order to abolish the risk of bilateral vocal folds’ paresis.

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Level of degree:

2 - studia doktoranckie

Degree discipline:

chirurgia ; endokrynologia

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Uniwersytet Jagielloński. Collegium Medicum. Wydział Lekarski.


Marcin Barczyński

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Biblioteka Medyczna Uniwersytetu Jagiellońskiego- Collegium Medicum

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Last modified:

Jun 26, 2019

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Nov 26, 2014

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Edition name Date
ZB-121241 Jun 26, 2019


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