Investigation on EMG Profiles of the Superior Laryngeal Nerve in a In Vivo Porcine Model

Abstract

Background: The electromyographic (EMG) profiles of external branch of the superior laryngeal nerve (EBSLN) have been defined and the optimal intensity of the stimulation of EBSLN in an in vivo porcine model has been explored. Materials: EMG was simultaneously registered by the surface of endotracheal tube and needle electrodes by applying a monopolar stimulation probe in 12 piglets (22 EBSLNs). Vagal nerve (VN), RLN and EBSLN were excited to record the EMG tracings and cricothyroid muscle twitch (CTM). VN, RLN and EBSLN were stimulated from 0.1 to 1.0 mA. Cmin and Cmax have been defined as the minimum and maximal stimulation to evoke an EMG response. Results: The stimulation resulted in a dose-response curve. Cmin were 0.19 mA (0.04–0.4), 0.19 mA (0.08–0.3) and 0.21 mA (0.1-0.4) for EBSLN, RLN and VN (p > 0.05) respectively. Cmax were 0.6 mA along with an amplitude value of 396 ± 330 μV, 0.5 mA including 1058 ± 382 μV, 0.8 mA coupled with 870 ± 382 μV, equally for EBSLN, RLN and VN (p > 0.05) respectively. No asymmetry of amplitude responses each side for EBSLN, RLN and VN (p = 0.317, p = 0.203 and p = 0.468, respectively) was noted. The amplitudes of EBSLN were significantly lower than RLNs and VN (42% of RLN and 50% of VN amplitude rates). Also, CTM twitch was always detectable with the stimulation of EBSLN. Conclusions: Cmin and Cmax of EBSLN were comparable to RLN and VN standards. The amplitude stimulus-response curves of RLN, VN and EBSLN were highly variable. It has been suggested to apply a stimulation of 1.0 mA and a visual appreciation of CTM twitch for the identification of EBSLN.

Keywords:

• neural monitoring
• superior laryngeal nerve
• external branch of superior laryngeal nerve
• electrophysiological characteristics
• thyroid
• surgery
• porcine model

Declaration of interest

All authors have no conflict of interest to disclose, and no other funding or financial relationship with the surgical industry.

Ethical approval

The study protocol was approved by the Institutional Animal Care and Use Committee of the Laboratory Animal Center of Jilin University (China).

Informed consent

Informed consent not required for this study.

Availability of data and materials

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Level of evidence

N/A

AUTHORS CONTRIBUTIONS

Conception and design of study: Sui Hun, Gianlorenzo Dionigi.

Administrative support of study: Zhao Yishen, Li Changlin, Liu Xiaoli, Zhou Le, Zhang Daqi, Xin Jingwei, Wang Tie, Li Shijie.

Collection and assembly of data: Zhao Yishen.

Analysis and interpretation of data: All Authors.

Preparation of manuscript: All Authors.

Final approval of manuscript: All Authors.