CASE REPORT


https://doi.org/10.5005/jp-journals-10001-1556
International Journal of Head and Neck Surgery
Volume 14 | Issue 4 | Year 2023

Nonrecurrent Laryngeal Nerve in Total Thyroidectomy: Two Case Reports and Literature Review


Lily V Mejía1, Luisa F Hernández Bello2, Julián Gómez-Herrera3

1–3Department of Head and Neck, Clínical Nueva El Lago Bogotá, Oncólogos del Occidente Armenia, Colombia

Corresponding Author: Luisa Fernanda Hernández Bello, Department of Head and Neck, Clínical Nueva El Lago Bogotá, Oncólogos del Occidente Armenia, Colombia, Phone: +57 3007121790, e-mail: dr.hermed@gmail.com

Received: 14 May 2023; Accepted: 31 July 2023; Published on: 16 January 2024

ABSTRACT

Introduction: The non-recurrent laryngeal nerve (NRLN) is an indulgent and unusual entity, because of the low prevalence and knowledge; the diagnosis may be difficult. When injured it may lead to functional alterations such as vocal cords paralysis and airway obstruction, awareness of this diagnosis is definitive to avoid its damage surgical interventions.Presentation of cases: In our two patients a total thyroidectomy was performed because of a benign pathology. during the intervention a laryngeal nerve without a recurrent pathway was found and documented their origin directly from the vagus nerve.Discussion: The diagnosis of NRLN is usually incidental during a surgical procedure. That is the reason why it can be easily damaged in different ways (transection, electrothermal etc). NRLN is documented in the right side in higher percentage, and it is directly related to a vascular malformation known as lusoria artery.

Conclusion: The anatomy knowledge has a determining factor in the surgical outcomes. In this way the iatrogenic damage can be minimized and consequences due to the damage of the RLN can be prevented.

How to cite this article: Mejía LV, Hernández Bello LF, Gómez-Herrera J. Nonrecurrent Laryngeal Nerve in Total Thyroidectomy: Two Case Reports and Literature Review. Int J Head Neck Surg 2023;14(4):66–67.

Source of support: Nil

Conflict of interest: None

Patient consent statement: A written informed consent was obtained from the patient for publication of this article.

Keywords: Case report, Recurrent laryngeal nerve, Recurrent laryngeal nerve injury, Thyroidectomy

INTRODUCTION

There are different known variants of the recurrent laryngeal nerve (RLN): Extralaryngeal branches, laryngeal nerves deformed by the thyroid goiter, and the nonrecurrent laryngeal nerve (NRLN).1 The NRLN is an infrequent anatomical variant whose incidence is 0.3–1.6% on the right side and 0.04% on the left side.2 The first case of the left variant was reported in Berlin in 1935 in a cadaveric dissection.3 This is mainly due to an embryological vascular disorder. The absence of the brachiocephalic trunk characterizes the right-side anomaly associated with an aberrant subclavian artery, often called a lusory artery. This was described by Bayford in 1789.4 The left side associates with the presence of situs inversus.5 Two cases were reported in which, during the surgical act, NRLN was documented, which can be a challenge in the surgical approach.

CASE DESCRIPTION

Case 1

A 54-year-old female patient with a thyroid nodule antecedent of approximately 2 cm. It was studied with a fine needle aspiration cytology (FNAC), which reported a IVth category in the Bethesda system. Because of this and its growth in the last year, a total thyroidectomy was performed in April 2022. The documentation of an NRLN on the right side was one of the main finds during surgery (Fig. 1).

Fig. 1: Case 1—right NRLN

Case 2

A 46-year-old female patient with symptomatic thyroid goiter (swallowing disorder) was taken for a total thyroidectomy in January 2022.

As pathological history, it presents psoriasis in medical management. During the surgical act, a right NRLN was documented (Fig. 2).

Fig. 2: Case 2—right NRLN

DISCUSSION

The RLN usually emerges in the mediastinum from the vagus nerve (Le et al.); they ascend through the tracheoesophageal grooves to the larynx after making a loop in the aortic arch on the left side and in the subclavian artery on the right side.6

During embryological development, the sixth branchial arch originates from its ventral part, the pulmonary arteries, and from its dorsal part, the RLN. The fourth branchial arch originates the subclavian artery and the aortic trunk. In some cases, the fourth branchial arch on the right side fades out, causing the subclavian artery to originate from the dorsal part of the aortic arch, leading the nerve to not have a recurrent path and join directly to the cricothyroid membrane.3

The right aberrant subclavian artery is the most common vascular malformation of the aortic arch, which is present in 0.2–13.3% of the general population and is usually associated with a right NRLN.7 When this anomaly is present, the subclavian artery, in 80% of the cases, rides behind the esophagus, 15% through the esophagus, and 5% in front of the trachea (best known as the lusory artery).6

Once the NRLN anatomical variant is recognized, it can be classified under “Tonioto´s and Hong’s” model. There are three recognized types: type I, where the nerve accompanies the vessels of the superior thyroid pedicle; type II, with a parallel path to the inferior thyroid artery (ITA); type IIA, which runs above the trunk of the ITA; type IIB that runs through or below the ITA trunk; and lastly, type III, which does a loop or a V-shaped tour below the ITA,8 as illustrated in Figure 3.

Fig. 3: Nonrecurrent laryngeal nerve (NRLN) schematic

Avisse’s model also classifies the nerve by its path; type I, which enters the larynx through the upper thyroid border and type II, which runs close to the ITA and enters the larynx upwards and horizontally (IIA above the ITA and IIB below, giving the illusion of recurrence).9 This leads to type I of NRLN being easily confused by an STA branch and type II with ITA branches.1

The diagnosis of this entity is generally given during the surgical act,2 however, the systematic search for any vascular anomalies using a Doppler ultrasound could be beneficial during the preoperative.7 The combination of a thorax X-ray and ultrasound,9 the complementary use of computed tomography, and/or magnetic resonance imaging (considered the gold standard).7

Neuromonitoring can be used during thyroidectomy, making the correct differentiation of the motor roots possible,7 and suspect the presence of an NRLN in the absence of a positive signal during the vagus nerve stimulation.2 In this way, injuries that come from manipulation, transection, clamping, stretching, electro-thermal damage, ligation, or ischemia can then be prevented.1 In the presence of any damage, it should be repaired immediately by microvascular anastomosis.10

CONCLUSION

In both cases, female patients were taken to surgery for thyroid nodules and in whom the presence of a right NRLN was documented as an incidental intraoperative finding, evidenced in Figures 1 and 2 without any postoperative injury or alteration.

For thyroid gland surgery, knowledge of the anatomy of the anterior and lateral regions of the neck is key in order to identify, preserve, and avoid bilateral RLN injuries during surgery and, with this, prevent complications caused by its injury such as postoperative dysphonia, paralysis and/or paresis of the vocal folds.

To avoid NRLN injuries, the surgeon must be able to recognize the different anatomical variants of the RLN, as well as the NRLN classifications. Although imaging and neuromonitoring are technological advances that can help the procedure, correct dissection and knowledge of the anatomical variants is the main method to reduce the risk of injuring these nerves.

REFERENCES

1. Chiang FY, Lu IC, Chen HC, et al. Anatomical variations of recurrent laryngeal nerve during thyroid surgery: how to identify and handle the variations with intraoperative neuromonitoring. Kaohsiung J Med Sci 2010;26(11):575–583. DOI: 10.1016/S1607-551X(10)70089-9

2. Asencio L, Osorio I, York E, et al. El nervio laríngeo no recurrente una variación anatómica a tener en cuenta en la cirugía tiroidea. Cirugía Española 2017;95:277

3. Page C, Monet P, Peltier J, et al. Non-recurrent laryngeal nerve related to thyroid surgery: report of three cases. J Laryngol Otol 2008;122(7):757–761. DOI: 10.1017/S0022215107008389

4. Yetisir F, Salman AE, Çiftçi B, et al. Efficacy of ultrasonography in identification of non-recurrent laryngeal nerve. Int J Surg 2012;10(9):506–509. DOI: 10.1016/j.ijsu.2012.07.006

5. Anand A, Nebhani D, Yadav SK, et al. Right-sided non-recurrent laryngeal nerve without any vascular anomaly: an anatomical trap. ANZ J Surg 2021;91(7-8):1635. DOI: 10.1111/ans.16891

6. Le QV, Ngo DQ, Ngo QX. Non-recurrent laryngeal nerve in thyroid surgery: a report of case series in Vietnam and literature review. Int J Surg Case Rep 2018;50:56–59. DOI: 10.1016/j.ijscr.2018.07.017

7. Pardal-Refoyo JL. Comments on the finding of right non recurrent laryngeal nerve during thyroidectomy. Acta Otorrinolaringol Esp (Engl Ed) 2017;68(6):375–376. DOI: 10.1016/j.otorri.2017.02.010

8. Dolezel R, Jarosek J, Hana L, et al. Clinical relevance and surgical anatomy of non-recurrent laryngeal nerve: 7 year experience. Surg Radiol Anat 2015;37(4):321–325. DOI: 10.1007/s00276-014-1369-4

9. Gong RX, Luo SH, Gong YP, et al. Prediction of nonrecurrent laryngeal nerve before thyroid surgery–experience with 1825 cases. J Surg Res 2014;189(1):75–80. DOI: 10.1016/j.jss.2014.02.010

10. Sadiq Z, Cheng L, Parker G, et al. Nonrecurrent laryngeal nerve in thyroid surgery - an important lesson. Brit J Oral Maxillofac Surg 2011;49:189.

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