Why recurrent laryngeal nerve

There was bilateral agreement in Some conditions can cause recurrent laryngeal nerve RLN palsy 15,34,41, Some procedures that may result in injury to the RLN are: thyroidectomies, parathyroidectomies, excision of Zenker's diverticulum, esophagectomies, tracheoplasties, neck dissections, correction of a patent ductus arteriosum, mediastinoscopy, and others 11,31, Thyroidectomy is the surgery in which this injury occurs most frequently.

According to Titche 42 , thyroidectomy accounts for This injury occurs more frequently when a branch of the ITA is inadvertently sectioned. Although some authors 30,33 defend the display of the RLN only in specific situations, most agree that the routine display of the RLN is essential for its protection 4,14,18,21,22,24,25,28,31,36,37,39, Lahey 24 , performing the routine display of the RLN in cases, obtained a reduction in the incidence of injury from 1.

The same author in a subsequent work, systematically visualized the nerve, in more than thyroidectomies with no injury However, excessive manipulation and dissection must be avoided so the nerve is brought under visual control without risk of compromising its vascularization. To this end, the ITA functions as a fixed reference point for the location of the r. The knowledge of the relationship between the RLN and the ITA is also important for the exteriorization of the thyroid lobe 12, Freschi 14 considered 8 possible relationships between these two structures.

Most authors, beyond the classic anatomy textbooks, recognize 3 types of relationships between the RLN and the ITA, as follows ,7,8,10,12,13,15,19,20,26,29,32,36,37,41,45 :. Simon 36 , after the dissection of 86 nerves in 43 corpses, affirmed that the usual relationship is the one in which the RLN establishes by passing posteriorly the ITA.

The anterior orientation of the nerve in relation to the artery was occasional, while its position between the arterial branches was a rare finding. Lahey 24 , based on surgical findings, had a similar opinion. Analyzing 17 studies which reported this relationship, when considering the both sides as a set, 16 showed that the RLN is more frequently located posterior to the ITA, between Considering right and left sides separately, differences appear.

On the left, in 15 analyzed works, 14 showed the predominance of the posterior position of the nerve in relation to the artery ,8,12,19,20,26,32,36,37,39, On the right, the variation is larger.

In 5, the RLN passed posterior to the ITA in most cases, and in only 2 studies was it placed anterior to the artery with higher frequency ,8,12,,26,32,36,37,39, Flament et al. In the sample presented here, we found similar results to those of the French author: the RLN lay between the branches of the ITA in Reed 32 in the U. Sturniolo 39 in Italy, found the same relationship on both the sides in The same author found a different relationship between the two sides In the sample presented here, only in The most frequent combinations in our study were: the RLN between the branches of the ITA on the right and on the left Hirata 19 in Japan, found a significant difference in the percentile distribution of the 3 types of relationships of the RLN with the ITA between the two sides.

He did not find a significant difference between males and females. This author found that the difference between the two sides could be attributed to the difference in the anatomical course of the RLN on the right and on the left.

In the present sample, the results of this analysis are similar to the ones of the Japanese author. The difference between the two sides right and left of the orientation of the RLN in relationship to the ITA was significant. Among us, Costa et al. The factors that determine these observed differences in the anatomical variations of the RLN are still not established. Pereira 30 and Lages 23 in independent works, when reporting cases of non-recurrent laryngeal nerve, in vivo and in a corpse respectively, emphasized that the racial factor should receive greater attention.

Both findings had occurred in crossbred female individuals, according to the authors. Steinberg et al. In a small percentage, one of these branches was also subdivided. There was no such thing as a constant relationship between these two structures. It would be interesting to analyze the influence of racial differences on the relationship between the RLN and the ITA, based on works of different nationalities ,7,8,12,13,19,20,26,32,36,38,45 Table 4 , that were done primarily in populations with well-defined racial features.

In those studies, which were carried out on embalmed corpses, these racial features are frequently lost. This fact, as well as the great racial miscegenation found among us, were the reasons why this analysis was not carried out in the present sample. But even those works where data were obtained from corpses during autopsy, or in surgical cases, there is no information permitting a racial characterization of the samples and a rigorous evaluation of the data from this standpoint.

The idea that the RLN is more frequently posterior to the ITA, and moreover, expecting this relationship to repeat on both sides, gives the surgeon a false sense of security. If the nerve lies anterior to, or between the branches of the ITA, the withdrawal of the thyroid gland from its stream bed results in the withdrawal of the nerve, with injury being more likely than when the nerve is posterior to the i. Gray's anatomy: the anatomical basis of clinical practice.

ISBN: 4. Gross, C. Galen and the squealing pig. The Neuroscientist Baltimore, Md. Harris, P. ISBN: Related articles: Anatomy: Head and neck. Promoted articles advertising. Loading more images Close Please Note: You can also scroll through stacks with your mouse wheel or the keyboard arrow keys. Loading Stack - 0 images remaining. By System:. Patient Cases. Objectives To analyze the frequency of extralaryngeal branching ELB of the recurrent laryngeal nerve RLN in a consecutive series of patients undergoing thyroidectomy by the same group of surgeons during an extended period and to compare our findings with the data available in the literature.

Patients From March 1, , to September 30, , patients underwent thyroidectomy. Of these, patients had surgical information about at least 1 RLN. A total of patients underwent bilateral operations. During the last 5 years of the study, intraoperative laryngeal nerve monitoring was performed in selected patients using a commercially available system.

Results A total of RLNs Among patients in whom intraoperative laryngeal nerve monitoring was used, the anterior branches usually exhibited more electrophysiologic activity. Conclusions Extralaryngeal branching was found in In recent patients with intraoperative laryngeal nerve monitoring, electrophysiologic activity was observed in the branches, particularly the anteriorly situated ones.

Recognition of this frequent anatomical configuration and meticulous preservation of all branches are of paramount importance to decrease postoperative morbidity associated with thyroidectomy. The recurrent laryngeal nerve RLN is the main motor nerve of all intrinsic laryngeal muscles except for the cricothyroid muscle. After leaving the superior mediastinum, the RLN courses toward the larynx on the tracheoesophageal groove, keeping a close anatomical relationship with the thyroid gland, as well as with the parathyroid glands and branches of the inferior thyroid artery.

Immediately after crossing the Berry ligament, the RLN enters the larynx. Because of its peculiar anatomical relationships, the RLN is vulnerable during operations involving the thyroid gland especially in the Berry ligament, Zuckerkandl tubercle, tracheoesophageal groove, and inferior and superior thyroid poles and during dissections of level VI lymph nodes.

Several anatomical variations of the RLN may be found, further increasing the jeopardy for inadvertent injury. These include a variable relationship with the branches of the inferior thyroid artery, the nonrecurrent inferior laryngeal nerve, and extralaryngeal branching ELB.

The relationship between the RLN and the branches of the inferior thyroid artery is inconsistent. The most dangerous anatomical variation associated with complication risk during thyroidectomy is the nonrecurrent inferior laryngeal nerve. In , Stedman was the first author to describe this anomaly.

In this disorder, there is no traction on the inferior laryngeal nerve, which then exits the vagus nerve directly toward the larynx. Conversely, the embryologic vascular anomaly on the left side absence of the ductus arteriosus is incompatible with survival of the fetus. Therefore, this variation is only found on the right side unless the patient has situs inversus totalis.

In , Henry et al 4 reported 33 cases of nonrecurrent inferior laryngeal nerves, 2 of which were located on the left side in patients with complete visceral inversion. The largest series in the literature to date was published by the same group 15 years later, 5 comprising nonrecurrent inferior laryngeal nerves that were observed during thyroidectomies and carotid endarterectomies.

Within the larynx, individual branches correspond to the intrinsic laryngeal muscles. However, this division may occur before the RLN enters the larynx near the Berry ligament or the inferior thyroid artery, increasing the possibility of iatrogenic damage to 1 or more of these branches. Moreover, its injury usually causes permanent paralysis of the corresponding intrinsic laryngeal muscle.

Authors have reported it in most of their patients undergoing thyroidectomy. In , Gregg 6 published a meta-analysis of the literature that included RLNs, Katz 7 described RLNs, In a subsequent publication by the same group that included RLNs, Katz and Nemiroff 8 reported They dissected 49 cadavers, including 96 sides of the neck.

The objectives of this study were to analyze the frequency of ELB of the RLN in a consecutive series of patients undergoing thyroidectomy by the same group of surgeons during an extended period and to compare our findings with the data available in the literature. This was a retrospective medical record study of a consecutive case series of patients who underwent thyroidectomy from March 1, , to September 30, , by the same surgical team C.

A total of patients underwent bilateral thyroidectomies. Using a template to document the findings, we recorded demographic data, surgical extent and pathologic findings, and information regarding ELB of the RLN including the number of branches when available.

No statistical method was applied, because no population was compared within the study. This study received institutional review board approval. There were female patients Most patients Information regarding RLNs was obtained. Among these, RLNs The number of branches was documented in RLNs During the last 5 years of the study, intraoperative laryngeal nerve monitoring was used in patients.

Of these, patients had information about at least 1 RLN. Among RLNs, The anterior branches usually exhibited more electrophysiologic activity on stimulation. Although not the main focus of this study, 14 nonrecurrent laryngeal nerves were found, all on the right side. Thyroidectomy was considered a very dangerous operation until the end of the 19th century because of unacceptable morbidity and mortality. Samuel Gross, perhaps the most respected surgeon of that time, made the following statement in Can the thyroid gland when in the state of enlargement be removed with a reasonable hope of saving the patient?

Experience emphatically answers, no!