Efficacy of Intraoperative Neural Monitoring (IONM) in Thyroid Surgery: the Learning Curve

Min Kyu Kwak; Song Jae Lee; Chang Myeon Song; Yong Bae Ji; Kyung Tae

doi:10.11106/ijt.2018.11.2.130

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Kwak, Lee, Song, Ji, and Tae: Efficacy of Intraoperative Neural Monitoring (IONM) in Thyroid Surgery: the Learning Curve

Original Article

International Journal of Thyroidology 2018; 11(2): 130-136.

Published online: 30 November 2018

DOI: https://doi.org/10.11106/ijt.2018.11.2.130

Efficacy of Intraoperative Neural Monitoring (IONM) in Thyroid Surgery: the Learning Curve

Min Kyu Kwak, Song Jae Lee, Chang Myeon Song, Yong Bae Ji, Kyung Tae

Department of Otorhinolaryngology-Head and Neck Surgery, Hanyang University College of Medicine, Seoul, Korea.

Correspondence: Kyung Tae, MD, PhD, Department of Otorhinolaryngology-Head and Neck Surgery, Hanyang University College of Medicine, 222-1 Wangsimni-ro, Seongdong-gu, Seoul 04763, Korea. Tel: 82-2-2290-8585, Fax: 82-2-2293-3335, kytae@hanyang.ac.kr

Received 15 October 2018 Revised 29 October 2018 Accepted 29 October 2018

The Korean Thyroid Association

(open-access):

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background and Objectives

Intraoperative neural monitoring (IONM) of recurrent laryngeal nerve (RLN) in thyroid surgery has been employed worldwide to identify and preserve the nerve as an adjunct to visual identification. The aims of this study was to evaluate the efficacy of IONM and difficulties in the learning curve.

Materials and Methods

We studied 63 patients who underwent thyroidectomy with IONM during last 2 years. The standard IONM procedure was performed using NIM 3.0 or C2 Nerve Monitoring System. Patients were divided into two chronological groups based on the success rate of IONM (33 cases in the early period and 30 cases in the late period), and the outcomes were compared between the two groups.

Results

Of 63 patients, 32 underwent total thyroidectomy and 31 thyroid lobectomy. Failure of IONM occurred in 9 cases: 8 cases in the early period and 1 case in the late period. Loss of signal occurred in 8 nerves of 82 nerves at risk. The positive predictive value increased from 16.7% in the early period to 50% in the late period. The mean amplitude of the late period was higher than that of the early period (p<0.001).

Conclusion

IONM in thyroid surgery is effective to preserve the RLN and to predict postoperative nerve function. However, failure of IONM and high false positive rate can occur in the learning curve, and the learning curve was about 30 cases based on the results of this study.

Keywords: Thyroidectomy, Intraoperative neural monitoring, Recurrent laryngeal nerve, Vocal cord paralysis

Figures and Tables

Fig. 1

Failure rate of intraoperative neural monitoring in the early and late periods.

Table 1

Characteristics of patients (n=63)

BMI: body mass index, N: number

Table 2

Correlation of postoperative vocal cord paralysis and loss of signal in intraoperative neural monitoring according to the period

LOS: loss of signal, VCP: vocal cord paralysis

Table 3

Validation of the performance of intraoperative neural monitoring for predicting postoperative recurrent laryngeal nerve function according to the period

NPV: negative predictive value, PPV: positive predictive value

Table 4

Mean electromyographic amplitude according to the period

NAR: nerve at risk

Table 5

Mean electromyographic amplitude according to neuromonitoring devices

C2: C2 Nerve Monitoring System (Inomed, Teningen, Germany), NAR: nerve at risk, NIM 3.0: NIM 3.0 Nerve Monitoring System (Medtronic Xomed, Jacksonville, FL, USA)

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