Comparison of Recurrent Laryngeal Nerve Identification Time in the Lower Central Triangle during Thyroid Surgery Using Neurophysiological Mapping and Monitoring.

Eunhye Lee,Hyeong Won Yu,Young Jun Chai,Keunchul Lee,Kyu Eun Lee,June Young Choi,Su-Jin Kim

doi:10.3390/medicina57080748

Abstract

Background and Objectives: Preserving the recurrent laryngeal nerve (RLN) is important in thyroid surgery. However, no standardized surgical method for locating the RLN has been established. We defined a new anatomical definition termed “lower central triangle” (LCT) for consistent identification of RLN and used intraoperative nerve monitoring (IONM) to aid in identification and dissection of RLN. Materials and Methods: Patients undergone thyroidectomy were reviewed retrospectively in Seoul National University Bundang Hospital from January to September 2017. Patients with papillary thyroid carcinoma, follicular neoplasm, and Graves’ Disease were included while right side non-RLN in arteriosus lusoria, cancer invasion, pre-existing vocal cord palsy, or under the age of 18 were excluded. RLNs were tested with IONM within LCT consisting of the lower pole as the apex and the common carotid artery as the opposite side. The samples were divided into two groups, IONM and non-IONM. Results: Forty lobes in total were included, 22 in IONM group and 18 in non-IONM group. Groups were not significantly different in age, cancer proportion, and accompanying thyroiditis while sex and nodule size differed. RLN detection time was 10.43 s shorter (p < 0.001), and confirmation time was 10.67 s shorter (p = 0.09) in IONM group than in non-IONM group. Both right and left RLNs were located predominately in the middle of LCT. No transient or permanent vocal cord palsy occurred. Conclusions: While IONM is an appropriate aid for thyroidectomy, our approach using LCT to locate the RLN is a novel definition of anatomy that provides prompt identification of the RLN in thyroid surgery.

Highlights

The present study evaluates the efficacy of using IOMN to locate the recurrent laryngeal nerve (RLN) within the lower central triangle” (LCT) during thyroid surgery
Mean size of thyroid nodule was slightly bigger in the intraoperative nerve monitoring (IONM) group (2.22 cm) than in the non-IONM group (1.21 cm, p = 0.037)
The final pathology review revealed that 45.5% of the IONM group was accompanied by thyroiditis, while 38.9% of the non-IONM group was accompanied by thyroiditis (p = 0.676)

Summary

Introduction

Preserving the recurrent laryngeal nerve (RLN) is a crucial aspect of thyroid surgery. Because the RLN is associated with vocal cord movement, intraoperative injury of the RLN can result in serious and debilitating complications. Unilateral injury of the RLN could compromise quality of life, manifesting as hoarseness, or potentially in incomplete closure of the glottis and subsequent dysphagia. Bilateral RLN paralysis could be life-threatening, resulting in difficult extubation of the endotracheal tube or unavoidable tracheostomy in the worst case [1]. Most RLN injuries are transitory with or without intervention, but some remain permanent [2,3] and there are presently no available interventions to reverse the injury [4]

Methods

Results

Conclusion