INTRODUCTION

Recurrent inferior laryngeal nerve is essential when supplying intrinsic muscle of the larynx, except the cricoarytenoid one. This nerve is also responsible for supplying the larynx area which is inferior to the vocal folds. Recurrent denomination is due to its anatomical disposition, as it is a loop of the vagus nerve, going through the subclavian artery at the right side in inferior way and through the aortic arch at the left side.

For being an essential structure to laryngeal function and for its close relation with thyroid gland, the identification and preservation of the recurrent laryngeal nerve are important steps on thyroidectomy and parathyroidectomy. Its injury and then vocal fold palsy is one of the complications of these surgeries, causing dysphonia and even respiratory deficiency soon after surgery, when injury is bilateral (2,3,4). Videolaryngoestroboscopy exams can be used after surgery in order to evaluate mobility of vocal folds, confirming or not the integrity of the nerve structure (4).

Non-recurrent inferior laryngeal nerve is a rare anatomical variation associated to anatomical irregularities of the subclavian arteries. In some individuals, the right subclavian artery is retroesophageal due to embryological origin alterations, what explains the absence of recurrence of the nerve in this side.

According to many authors, its presence is estimated at 1%, and the chances of an injury is greater during surgery when involving cervical area due to either unfamiliarity from surgeon of this variation or technical difficulty to recognize and preserve the nerve in these cases (4,6,7,8).

We reported, in this study, detection of the non-recurrent inferior laryngeal nerve to the right during comprehensive thyroidectomy and discussed the need of its identification and preservation during cervicotomy, when recurrent or not.


CASE REPORT

JRB, female, 44, white, searched Serviço de Otorrinolaringologia do Hospital Universitário São Francisco - Bragança Paulista - SP (ENT Service) with a diagnosis of nontoxic multinodular goiter, according to fine needle aspiration punction (FNA) performed at another service. Patient reported sensation of cervical compression and casual dyspnea for four months.

During physical examination enlarged thyroid was touched due to node lesions of 6 x 5cm in left thyroid lobe and of 4 x 4 in right thyroid lobe. Such node injuries presented elastic fiber consistency, flat surfaces and well-defined limits. Thyroid hormones as well as anti-thyroperoxidase and anti-thyroglobulin antibodies were normal. Comprehensive thyroidectomy was recommended.

Surgery procedure went normal, therefore, during dissection for identifying right inferior laryngeal nerve it was detected that this was not recurrent, emerging straight from vagus nerve to larynx (Picture 1).

Picture 1. Right vagus nerve (VN) appears anteriorly to carotid artery and perpendicularly ejecting, i.e. with no recurrence, the inferior laryngeal nerve (ILN), which runs straight to larynx.

Surgical specimen (Picture 2) was sent to histopathological exam, and diagnosed as chronic lymphocyte thyroiditis. At the moment, patient is asymptomatic, making use of thyroid hormone and has normal exams.

Picture 2. Surgical specimen from complete thyroidectomy.

DISCUSSION

Non-recurrent inferior laryngeal nerve occurs more often to the right (0.2 to 4%) and more rarely to the left (0.07%) (4). Henry et al (8), when analyzing 3791 cervicotomies, confirmed that predominance. In this series, authors observed 17 cases of non-recurrent nerve (0.54%) in 3098 cervictomies to the right and 2 cases (0.07%) in 2846 to the left.

Subclavian artery irregularities seem to be always present, and it is the direct cause of a non-recurrent inferior laryngeal nerve. Due to embryogenic alterations, the right subclavian artery can be retro esophageal, preventing, then, that the nerve is recurrent. The same situation is not observed to the left, as recurrence occurs to aortic arch in inferior way. Only during dextrocardia we can see a non-recurrent inferior left laryngeal nerve, what explains a lower number of cases to this side (5,9).

The absence of recurrence in its course increases the chance of an injury on the inferior laryngeal nerve during thyroidectomy and other types of surgeries which achieve cervical area (6,10).

According to Sparta et al (7), only the systematic identification of the inferior laryngeal nerve assures surgeons of the absence of injury. Thus, we understand the need of an anatomic knowledge and possible variations to perform cervictomies with a lower risk of injuries to this structure.

The diagnosis of this anatomical variation is rarely performed before surgery and only a CT from thorax showing a retro esophageal subclavian artery will make us suspect of its occurrence. Detection of an anomalous nerve usually occurs during surgery and incidentally (4,10).

In this case, we observed, during surgery, a non-recurrent inferior laryngeal nerve to the right during a comprehensive thyroidectomy. Despite such difficulty, the nerve was correctly identified and preserved, as it is usual at our service.

So, we wish to aware surgeons who perform on cervical area, especially in thyroidectomies, of the importance of the inferior laryngeal nerve exposure, avoiding its incidental injury.


CONCLUSION

Inferior laryngeal nerve injury is an implication of thyroid gland and parathyroid surgeries and the risk of this occurrence enlarges when the nerve is non-recurrent. Though, only its dissection and identification assure surgeon of that such structure was totally preserved.


REFERENCES

1. Moore KL: O Pescoço. In: Moore KL. Anatomia Orientada Para a Clínica. 3ª ed. Rio de Janeiro: Guanabara Koogan; 1994, p.710-73.

2. Steffen N, Herter NT, Martha VF. Tireoidectomias. In: Campos CAH, Costa HOO. Tratado de Otorrinolaringologia Vol 5. 1ª ed. São Paulo: Roca; 2003, p.557-77.

3. Gleischman S, Uyeda RY, Dunkelman D, Catz B, Karlan MS: A safe technique for thyroidectomy with complete nerve dissection and parathyroid preservation. Head Neck Surg, 1984, 6(6):1014-9.

4. Leite WP, Castro Júnior FM, Ferreira LAA, Holanda ME, Fernandes E, Silva V, Farias JF, Lima SB, Surimã WS, Mesquita Neto JWB, Santos BGR, Muniz VV, Figueiredo LL. Nervo laríngeo inferior não-recorrente: relato de 3 casos e revisão da literatura. Anais do 10ª Congresso Brasileiro de Cirurgia de Cabeça e Pescoço; 2005 Set 3 - 6; Salvador, Brasil.

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6. Arantes A, Gusmão S, Rubinstein F, Oliveira R: Anatomia microcirúrgica do nervo laríngeo recorrente: aplicações no acesso cirúrgico anterior à coluna cervical. Arq Neuro- Psiquiatr,2004, 62(3):22-6.

7. Sparta C, Cossu ML, Fais E, Palermo M, Cossu F, Ruggiu M, Noya G: Non-recurrent inferior laryngeal nerve: anatomy, frequency and surgical considerations. Minerva Chir, 2004, 59(6):555-61.

8. Henry JF, Audiffrit J, Plan M: The nonrecurrent inferior laryngeal nerve: A propos of 19 cases including 2 on the left side. J Chir (Paris), 1985, 122(6-7):391-7.

9. Pisanu A, Pili S, Uccheddu A: Non-recurrent inferior laryngeal nerv. Chir Ital, 2002, 54(1):7-14.

10. Abboud B, Aouad R: Non-recurrent inferior laryngeal nerve in thyroid surgery: report of three cases and review of the literature. J Laryngol Otol, 2004, 118(2):139-42.










1. Resident Doctor at Serviço de Otorrinolaringologia do Hospital Universitário São Francisco (ENT Service).
2. Master Student at Hospital do Servidor Público Estadual - SP - (Assistant Doctor at Serviço de Otorrinolaringologia do Hospital Universitário São Francisco and Hospital do Servidor Público Estadual.
3. Resident Doctor at Serviço de Otorrinolaringologia do Hospital Universitário São Francisco.

Study done at Hospital Universitário São Francisco - Bragança Paulista.
João Alcides Miranda
Address:Rua Bias Fortes, 438, Centro, Boa Esperança - MG, CEP 37170-000, phone (11) 9111-5881, e-mail jamiranda78@hotmail.com

This article was submitted to SGP - Sistema de Gestão de Publicações (Publication Management System) from RAIO on April 7, 2006 and was approved on April 17, 2006 21:49:50.