Identification of valid anatomical landmarks to locate and protect recurrent laryngeal nerve during thyroid surgery: a cadaveric study.

PURPOSE: Recurrent laryngeal nerve (RLN) is the most critical structure in terms of intricacy. Anatomic variations of the nerve may further make thyroid surgery cumbersome. The present study was undertaken to provide comprehensive knowledge about the soundness of commonly used anatomical landmarks such as Berry's ligament (BL), tracheo-esophageal groove (TEG), inferior thyroid artery (ITA), and the midpoint of the posterior border of the thyroid gland in the identification of the nerve intraoperatively. METHODS: Thirty adult cadavers were dissected to identify the RLN in the neck and to locate it in relation to the aforementioned anatomical landmarks. RESULTS: The RLN/BL relationship: RLN was most often located superficial to the BL (88.3%), followed by deep to the BL in 8.4%, and piercing the BL in 3.3% of cases, respectively. The RLN/TEG relationship: the RLN was located inside the TEG in most cases (71.7%), followed by RLN lying outside the TEG in 28.3%. Outside the groove, it was most commonly found lateral to the TEG (64.7%). RLN/ITA relationship: the nerve was passing deep to the artery in most of the cases (65%), followed by superficial (30%) and rarely (5%) in-between the branches. RLN/ midpoint posterior border of thyroid relationship: In 57 (95%) cases, RLN was coursing in the area posterior to the midpoint of the posterior border of the gland with an average distance of 4.95 ± 2.23 mm ranging between 2.21 and 12.1 mm. CONCLUSIONS: Both the BL and TEG are potentially crucial for safeguarding RLN. Although in results, BL turns out to be more consistent than TEG, we propose the utilization of both these anatomical landmarks together for complication-free neck surgeries. Furthermore, the midpoint of the posterior border of the thyroid turns out to be the single most consistent landmark for identifying RLN during partial thyroidectomy.

Anatomy and motor function of extra-laryngeal branching patterns of the recurrent laryngeal nerve; an electrophysiological study of 1001 nerves at risk.

INTRODUCTION: Safe thyroid surgery depends on a deep knowledge of human neck anatomy, including the recurrent laryngeal nerve (RLN). Anatomic variations such as extra-laryngeal terminal branching (ETB) are common. PATIENTS AND METHODS: We studied the ETB pattern of 1001 RLNs at risk in 596 patients. We identified and exposed the location of division points on the cervical part of bifid RLN. The function of nerve branches was assessed through intraoperative nerve monitoring (IONM). RESULTS: Bifid RLNs was identified in 39.6% of patients. The nerve-based prevalence of ETB was 28.5%. The prevalence of ETB for the right and left RLN was 21.8% and 35.5%, respectively (p < 0.001). The location of the division point was found in the middle, distal, and proximal segments in 48.8%, 33.3%, and 18% of bifid RLNs, respectively. Electrophysiological monitoring revealed motor functions in all anterior and in 7% of posterior branches. The rate of injury was 0.4%, and 1.1% in single trunk and bifid nerves, respectively (p = 0.360), and 3.9% in nerves with proximal branching (p = 0.084). CONCLUSIONS: The ETB prevalence is high and showing division points in different cervical segments of the RLN. All anterior branches and some posterior branches contain motor fibers. Knowledge and awareness of these anatomic and functional variations are mandatory for every thyroid surgeon to avoid misidentification and misinterpretation of human RLN anatomy.

Varied Recurrent Laryngeal Nerve Course Is Associated with Increased Risk of Nerve Dysfunction During Thyroidectomy: Results of the Surgical Anatomy of the Recurrent Laryngeal Nerve in Thyroid Surgery Study, an International Multicenter Prospective Anatomic and Electrophysiologic Study of 1000 Monitored Nerves at Risk from the International Neural Monitoring Study Group.

Background: The recurrent laryngeal nerve (RLN) can be injured during thyroid surgery, which can negatively affect a patient's quality of life. The impact of intraoperative anatomic variations of the RLN on nerve injury remains unclear. Objectives of this study were to (1) better understand the detailed surgical anatomic variability of the RLN with a worldwide perspective; (2) establish potential correlates between intraoperative RLN anatomy and electrophysiologic responses; and (3) use the information to minimize complications and assure accurate and safe intraoperative neuromonitoring (IONM). Methods: A large international registry database study with prospectively collected data was conducted through the International Neural Monitoring Study Group (INMSG) evaluating 1000 RLNs at risk during thyroid surgery using a specially designed online data repository. Monitored thyroid surgeries following standardized IONM guidelines were included. Cases with bulky lymphadenopathy, IONM failure, and failed RLN visualization were excluded. Systematic evaluation of the surgical anatomy of the RLN was performed using the International RLN Anatomic Classification System. In cases of loss of signal (LOS), the mechanism of neural injury was identified, and functional evaluation of the vocal cord was performed. Results: A total of 1000 nerves at risk (NARs) were evaluated from 574 patients undergoing thyroid surgery at 17 centers from 12 countries and 5 continents. A higher than expected percentage of nerves followed an abnormal intraoperative trajectory (23%). LOS was identified in 3.5% of NARs, with 34% of LOS nerves following an abnormal intraoperative trajectory. LOS was more likely in cases of abnormal nerve trajectory, fixed splayed or entrapped nerves (including at the ligament of Berry), extensive neural dissection, cases of cancer invasion, or when lateral lymph node dissection was needed. Traction injury was found to be the most common form of RLN injury and to be less recoverable than previous reports. Conclusions: Multicenter international studies enrolling diverse patient populations can help reshape our understanding of surgical anatomy during thyroid surgery. There can be significant variability in the anatomic and intraoperative characteristics of the RLN, which can impact the risk of neural injury.

Identification of the recurrent laryngeal nerve during thyroidectomy can affect the complication rate.

AIM: Identification of recurrent laryngeal nerve (RLN), performed via different techniques, decreases nerve injury during thyroidectomy. We aimed to evaluate the effect of different anatomic levels at which RLN was identified on postoperative complications. MATERIAL AND METHODS: The patients underwent total thyroidectomy or lobectomy without lymph node dissection were included. Two different surgical methods were performed: thyroidectomy identifying RLN at level of inferior thyroid artery (ITA) (Group 1); at level of Berry's ligament (Group 2). Patients were evaluated with indirect laryngoscopy on 3rd postoperative day, if nerve damage was determined, at each six months. Nerve damage and postop hypocalcemia were accepted transient up to 6th month, permanent after 6th month. Total serum calcium levels were postoperatively measured on 24th and 48th hours, and then monthly. RESULTS: Unilateral and bilateral RLN damage were detected as 4.4% and 2.2% in Group 1; and 8% and 2.67% in Group 2, respectively. The frequency of RLN damage was similar (p=0.62). Postoperative hypocalcemia was significantly higher in Group 1 (p=0.04); hypocalcemia was similar (p=0.149). One patient in Group 1, and 2 patients in Group 2 had f superior laryngeal nerve (SLN) injury. Three patients from each group showed permanent hypocalcemia. One patient in Group 1, and two in Group 2 developed permanent hoarseness. DISCUSSION: RLN injury was similar in both groups, however, temporary hypocalcemia was more frequent in patients undergone thyroidectomy with RLN identification at ITA level. CONCLUSIONS: Devascularization of parathyroid glands may be accused. Future studies are needed. KEY WORDS: Recurrent laryngeal nerve, Thyroidectomy.

Left non-recurrent inferior laryngeal nerve in a patient with right-sided aortic arch and aberrant left subclavian artery.

Non-recurrent inferior laryngeal nerve (NRILN) is rare but one of the important anatomical variations in thyroid and parathyroid surgery. Almost all cases were observed on the right side with aberrant right subclavian artery and left NRILN have been reported in only five cases so far. Here, we reported a 38 year-old Japanese male with left NRILN accompanying adenomatous goiter. He was referred to our hospital for the surgical treatment of left thyroid goiter. Preoperative computed tomography revealed right-sided aortic arch and aberrant left subclavian artery with no signs of complete situs inversus viscerum, suggesting possible left NRLN. Left hemithyroidectomy was performed using nerve monitoring system. Intraoperatively, left recurrent laryngeal nerve was not identified along tracheoesophageal groove, but directly originated from vagal nerve and was running horizontally to larynx. Mobility of vocal cords were not impaired and postoperative course was uneventful. During thyroid surgery for the patients with right-sided aortic arch, meticulous care should be taken using nerve monitoring system to avoid nerve injury.

Two Concomitant Right Nonrecurrent Laryngeal Nerves Encountered During Thyroidectomy (Type 4 Course): Reported for the First Time.

INTRODUCTION: The recurrent laryngeal nerve gains its name because after branching from the vagus nerve, it turns superiorly (recur) around the subclavian artery on the right and around the ligamentum arteriosum on the left, the nonrecurrent nerve has a straight direct course to the larynx and doesn't follow this course. It presents mostly on the right side. The presence of this variation places the nerve at higher risk of injury during neck surgery especially thyroid operations. CASE PRESENTATION: A 45-year-old lady presented with painless thyroid enlargement for 1 year. Thyroid examination showed a 3-cm firm nodule at the right thyroid lobe with normal thyroid function tests. Right thyroid lobectomy was done and the histopathology showed a benign follicular lesion. During surgery, we discovered 2 nonrecurrent laryngeal nerves at the right side which were arising from the vagus nerve and both were entering the larynx. CONCLUSION: Failure in identification of the nerve or overlooking the possibility of the non-recurrent laryngeal nerve may result in a serious sequelae of nerve damage, ipsilateral injury may lead to permanent hoarseness and bilateral injury may result in severe dyspnea or aphonia. Currently, there are 3 types of nonrecurrent laryngeal nerve courses. Type 1 passes near to the superior thyroid vessels. Type 2 (2A) passes parallel to the inferior thyroid artery and has a transverse course above it. Type 3 (2B) passes parallel to the inferior thyroid artery and transversely between branches of or under the inferior thyroid artery, we can add to this classification type 4, which are 2 nonrecurrent laryngeal nerves (double nerves) passing above and parallel to the inferior thyroid artery.

Anatomical Variations in Recurrent Laryngeal Nerves in Thyroid Surgery.

OBJECTIVE: To study terminal bifurcation of recurrent laryngeal nerves (RLNs) with original direction to larynx entry and to decrease the risk of vocal cord paralysis in thyroid patients. METHODS: The RLNs of 294 patients (482 sides) were dissected according to the branches into the larynx, and the original direction of each RLN trunk in thyroid surgery was recorded. RESULTS: (1) About 30.9% of the RLNs gave off multiple branches into the larynx. (2) Two and 3 branches of RLNs into the larynx were found in 25.5% and 5.4% of the cases, respectively. (3) In 0.4% or 2 cases, the RLN trunk combined with the inferior branch of the vagus nerve. (4) Nonrecurrent laryngeal nerve appeared in 2 cases. (5) On the left side, 68.0%, 25.6%, and 6.4% of cases were found with 1, 2, and 3 bifurcations of RLN to larynx entry, respectively. On the right side, 69.8%, 25.8%, and 4.4% cases were identified with 1, 2, and 3 bifurcations of RLN to larynx entry, respectively. (6) The combining dissection approach was proved as successful and safe for protecting the RLN with no permanent RLN paresis. CONCLUSIONS: Because of the anatomical variation in RLNs with extralaryngeal bifurcation, it is necessary to increase the awareness of surgeons about these variations so as to protect bifurcated nerves in thyroid surgery.

Prospective anatomical study to determine the site of insertion of recurrent laryngeal nerve into the larynx.

OBJECTIVES: Determine whether the insertion site of the recurrent laryngeal nerve (RLN) occurs at a predictable distance from the midline trachea, to help guide safe dissection during thyroid surgery. DESIGN: Prospective clinical trial. At the inferior edge of the cricoid cartilage, we measured the distance from mildline trachea to the RLN insertion site. SETTING: Single institution. PARTICIPANTS: 50 consecutive patients undergoing thyroid surgery. MAIN OUTCOME MEASURES: Distance from midline trachea to laryngeal insertion of RLN. RESULTS: The study population included 36 women and 14 men, with 72 total nerves measured. The average distance-to-midline + standard deviation (range) of the RLN was 20.7 + 2.3 (17-26) mm in women compared to 26.3 + 2.1 (22-32) mm in men. CONCLUSION: The insertion point of the RLN into the larynx at the level of inferior border of the cricoid cartilage can be reliably predicted, to facilitate early identification of the RLN during thyroid surgery.

Vision-based tracking system for augmented reality to localize recurrent laryngeal nerve during robotic thyroid surgery.

We adopted a vision-based tracking system for augmented reality (AR), and evaluated whether it helped surgeons to localize the recurrent laryngeal nerve (RLN) during robotic thyroid surgery. We constructed an AR image of the trachea, common carotid artery, and RLN using CT images. During surgery, an AR image of the trachea and common carotid artery were overlaid on the physical structures after they were exposed. The vision-based tracking system was activated so that the AR image of the RLN followed the camera movement. After identifying the RLN, the distance between the AR image of the RLN and the actual RLN was measured. Eleven RLNs (9 right, 4 left) were tested. The mean distance between the RLN AR image and the actual RLN was 1.9 ± 1.5 mm (range 0.5 to 3.7). RLN localization using AR and vision-based tracking system was successfully applied during robotic thyroidectomy. There were no cases of RLN palsy. This technique may allow surgeons to identify hidden anatomical structures during robotic surgery.

Association Between Recurrent Laryngeal Nerve Calibre and Body Figure: A Preoperative Tool to Assess Thin-Diameter Nerves in Thyroidectomy.

Inadvertent recurrent laryngeal nerve (RLN) injury is a major complication of thyroidectomy. This study aimed to investigate the association between preoperative clinical parameters and RLN size prediction. Total thyroidectomy and thyroid lobectomy data were collected between January 2014 and April 2017. Routine identification of the recurrent laryngeal nerves was performed, while intraoperative findings (nerve diameter, thyroid gland weight, intraoperative neuromonitoring (IONM) use, and signal recording) and demographic data were collected for analysis. A total of 848 patients with 1357 RLNs at risk were enrolled in this study. RLN diameter was thinner in females, those with body height <160 cm, and those with a BMI <25 (all p < 0.001). RLN diameter was directly proportional to age, body weight, height, and BMI. RLN diameter was thinner (1.71 mm vs. 1.55 mm, p = 0.039) and branched nerve incidence was higher (18.5% vs. 29.7%, p = 0.09) in the postoperative RLN injury group. Branched nerves were more frequently encountered in female patients (female vs. male: 28.8% vs. 18.7%, p = 0.004). The risk of RLN palsy in intraoperative IONM loss patients was 27 times higher compared to that in IONM normal patients (1.55% vs. 30%, p < 0.001). Thinner nerves did not yield a higher rate of IONM signal loss. Thinner nerves and higher palsy rates could be anticipated in females, younger age groups, those with shorter stature, and those with low BMI. RLN diameter was not associated with the rate of IONM signal loss.

A simple, efficient, and safe way of finding recurrent laryngeal nerve beneficial for PTC patients.

BACKGROUND: More surgeons have known the importance of parathyroid grand and recurrent laryngeal nerve protection in the surgery, but there is still plenty of scope to improve the surgical techniques. This study aims at investigating whether the improved method of finding recurrent laryngeal nerve (RLN) can protect parathyroid grand and RLN. METHODS: One hundred fifty-eight patients were enrolled and divided randomly into the test and control group according to different methods of finding RLN in the surgery. In the experimental group the author could quickly find the laryngeal recurrent nerve in the lower part of the neck and separate along the surface of the recurrent laryngeal nerve to the point where the recurrent laryngeal nerve gets into the larynx close to the thyroid gland named lateral approach, while in the control group the author severed the middle and lower thyroid vein and raised the lower thyroid pole to look for the RLN near the trachea by the blunt separation. RESULTS: The author identified 152 and 159 parathyroid glands in the test and control group, respectively and there were a lower ratio of auto-transplantation and less operative time in the test group compared with that in the control group. The author also found that the parathyroid hormone level (1 day and 2 months) in the test group was higher than that in the control group. There were no differences in metastatic LN and recurrent laryngeal nerve palsy in the 2 groups. CONCLUSION: The improved method of finding RLN is a simple, efficient and safe way, and easy to implement.

Right- Versus Left-sided Exposures of the Recurrent Laryngeal Nerve and Considerations of Cervical Spinal Surgical Corridor: A Fresh-Cadaveric Surgical Anatomy of RLN Pertinent to Spine.

STUDY DESIGN: Cadaveric study on fresh unprocessed, nonpreserved, undyed specimens which have not previously been reported. OBJECTIVE: We aimed to perform surgically relevant exposures of the anterior cervical spine with particular attention to observing the potential vulnerabilities of the RLN on right and left. SUMMARY OF BACKGROUND DATA: Vulnerability of the RLN in the anterior cervical spine approach on the right versus left is the subject of ongoing debate. Although most cadaveric studies focus on course variations, structural relations of RLN, they have been done in preserved (fixed) cadavers without relevance to the needs of spinal exposure. METHODS: Twelve fresh undyed cadavers had extensive layer by layer dissections by 2 surgeons (one with extensive experience as anatomy dissector). Both sides were explored for vulnerability during cervical spinal procedures. Each dissection was carried out in a phased approach and deliberately explored beyond what can be afforded in live surgery to allow the reader to conceptualize a better view of the structures. RESULTS: In all specimens, we consistently demonstrated that the right surgical corridor involved manipulation of the nerve and its branches especially below C5 to achieve optimum midline access: in the right corridor, the RLN is on its oblique course to the tracheoesophageal groove. On the left, RLN is already in the tracheoesophageal groove and out of the surgical field involving minimal direct mobilization of the nerve. CONCLUSION: RLN surgical anatomy photographed here is novel in using fresh unprocessed cadaveric specimens which has previously not been reported.Right surgical corridor, below C5, involves retraction/manipulation of RLN for achieving optimum spinal midline access, highlighting potential surgical vulnerability of right RLN. LEVEL OF EVIDENCE: 3.

Anatomía quirúrgica de las glándulas tiroides y paratiroides / Surgycal anatomy of the thyroid and parathyroid glands

Nuestro objetivo es lograr un relato de los detalles anatómicos que ayude al cirujano a conseguir intervenciones seguras, se elude el estilo de las anatomías descriptivas o topográficas tratando de producir una anatomía verdaderamente quirúrgica. Para ello se mencionan las fascias, estructuras capsulares y ligamentos que envuelven a la tiroides. Se hace hincapié en la vascularización, principalmente en lo referente a la arteria tiroidea inferior, fundamental para la localización del nervio recurrente. También en lo relacionado con el conjunto del drenaje venoso, que con su complicada distribución dificulta notablemente la disección. Relatamos minuciosamente las variantes anatómicas y las anomalías que afectan a la estructura de la región, su conocimiento es fundamental ante la posibilidad de que el cirujano encuentre en sus operaciones alguna de ellas. Describimos el aspecto, las relaciones y lo referente a la localización de las glándulas paratiroides, detalles necesarios para evitar su resección inopinada en las tiroidectomías y para el reconocimiento de la glándula patológica en el hiperparatiroidismo

The aim of this article is describe the anatomical details that helps the surgeon to achieve safe surgeries, the style of descriptive or topographic anatomies is avoided trying to produce a truly surgical anatomy. For this, fascias, capsular structures and ligaments that surround the thyroid gland are mentioned. Emphasis is placed on vascularization, mainly in relation to the inferior thyroid artery, essential for the location of the recurrent nerve. Also in relation to the whole of the venous drainage, which with its complicated distribution makes dissection remarkably difficult. We carefully describe the anatomical variants and the anomalies that affect the structures of the region, their knowledge is fundamental to the possibility that the surgeons finds in their surgeries. We describe the appearance, the relationships and the reference to the location of the parathyroid glans. Neccesary details to avoid their inopinate resection in thyroidectomies and for the recognition of the pathological gland in the hyperparathyroidism

The Tubercle of Zuckerkandl is Associated with Increased Rates of Transient Postoperative Hypocalcemia and Recurrent Laryngeal Nerve Palsy After Total Thyroidectomy.

The current concept of complete resection of thyroid parenchyma shifted the practice from subtotal thyroidectomy to total thyroidectomy for a wide range of benign and malignant thyroid affliction and brought the tubercle of Zuckerkandl once again into attention. This embryological remnant has been shown to have a constant relationship with the recurrent laryngeal nerve and the superior parathyroid gland and may be used as a landmark for safe dissection. In order to assess if the presence of the tubercle of Zukerkandl has an impact on the most important complications of thyroid surgery, we have prospectively studied 128 patients diagnosed with nodular goiter who underwent total thyroidectomy. Grade 0 or the absence of the tubercle of Zuckerkandl, according to Pellizo et al, was noted in 42 cases (32.8%). During surgery, we identified 38 grade 1 tubercles (29.7%), 31 grade 2 tubercles (24.2%) and 16 grade 3 tubercles (12.5%). Out of 11 bilateral tubercles, 4 were measured as grade 3.Of all 47 patients with grade 2 and 3 tubercles, 18 (38.3%) developed transient postoperative hypocalcemia (p 0.0001, r=0.47) and 10 (21.3%) transient postoperative nerve palsy (p=0.004, r=0.25). All patients fully recovered during follow-up. The tubercle of Zuckerkandl, when present and of significant macroscopic size is associated with increased rates of transient postoperative hypocalcemia and recurrent laryngeal nerve palsy.

Can the Zuckerkandl tubercle assist in the location of the inferior laryngeal nerve during thyroidectomies? / O tubérculo de Zuckerkandl pode auxiliar na localização do nervo laríngeo inferior durante tireoidectomias?

OBJECTIVE: to evaluate whether the lateral projection of the thyroid gland, called Zuckerkandl's tubercle (ZT), can assist the surgeon in identifying the inferior laryngeal nerve during conventional open thyroidectomy. METHODS: we conducted a prospective study with 51 patients submitted to thyroidectomy, with a total of 100 resected thyroid lobes, and observed the presence or absence of ZT in sufficient dimensions to be identified without image magnification, its base and height, its location in the gland, and its anatomical relationship with the inferior laryngeal nerve. RESULTS: ZT was present in 68 of the 100 thyroid lobes analyzed (68%). The mean base was 6.7mm on the right side and 7.1mm on the left side, and the average height was 5.7mm on the right side and 6.1mm on the left side. In most of the lobes studied, the tubercle had a minimum height of 5mm (55.9%), with no significant difference between the right and left lobes of the thyroid gland. During surgery, 100% of the identified ZTs were anterior to the inferior laryngeal nerve, just below the nerve entry in the larynx. CONCLUSION: the ZT is a quite frequent entity and large enough to serve as an intraoperative anatomical reference for the inferior laryngeal nerve, next to its entry in the larynx, along with other anatomical references.

OBJETIVO: avaliar se a projeção lateral da glândula tireoide, chamada tubérculo de Zuckerkandl (TZ), pode auxiliar o cirurgião na identificação do nervo laríngeo inferior durante a tireoidectomia convencional aberta. MÉTODOS: estudo prospectivo de 51 pacientes submetidos à tireoidectomia, com um total de 100 lobos tireoidianos ressecados, e observação da presença ou não do TZ em dimensões suficientes para ser identificado sem magnificação de imagem, suas dimensões de base e altura, sua localização na glândula e sua relação anatômica com o nervo laríngeo inferior. RESULTADOS: o TZ estava presente em 68 dos 100 lobos de tireoide analisados (68%). A dimensão média da base foi 6,7mm no lado direito e 7,1mm no lado esquerdo, e a altura média foi 5,7mm no lado direito e 6,1mm no lado esquerdo. Na maioria dos lobos estudados, o tubérculo tinha altura mínima de 5mm (55,9%) sem diferença significativa entre o lobo direito e esquerdo da glândula tireoide. Durante a cirurgia, 100% dos TZ identificados estavam anteriores ao nervo laríngeo inferior, imediatamente abaixo da entrada do nervo na laringe. CONCLUSÃO: o TZ é bastante frequente e em dimensões suficientes para ser usado como referência anatômica na localização intraoperatória do nervo laríngeo inferior, próximo à sua entrada na laringe, junto com as demais referências anatômicas.

[The inferior laryngeal nerve: anatomical and surgical considerations about 60 thyroidectomy]. / Le nerf laryngé inférieur: considérations anatomiques et chirurgicales à propos de 60 thyroïdectomies.

Thyroid surgery requires a thorough knowledge of cervical anatomy and anatomical variations, in particular of the lower laryngeal nerve, in order to avoid iatrogenic lesions. The objective of our study was to analyze the relationships of the lower laryngeal nerve, the existence of branches of nerve division and a subjective appreciation of the size of the nerve. This is a prospective study of 1 year including 60 patients who underwent thyroidectomy. Sixty patients underwent surgery on the thyroid gland between February 2014 and January 2015 by the same principal operator (10 men and 50 women). The average age of our patients was 51 years. For men were performed 6 total thyroidectomies, 2 left lobo-isthmectomies and 2 right lobo-isthmectomies. For women were performed 33 total thyroidectomies, 8 left lobo-isthmectomies and 9 right lobo-isthmectomies. On the right, the nerve was superficial relative to the artery in 71.6% of cases; it was divided in 33.3% of cases and was abnormally thin in 16.6% of cases. On the left, the nerve was deep in relation to the artery in 83.3% of cases; it was divided in 15% of cases and was abnormally thin in 11.6% of cases. Knowledge of the anatomical variations of the lower laryngeal nerve is essential in thyroid surgery, the risk is particularly important on the right side given the sometimes very small caliber and the existence of branches of division more frequent than on the left side.

Non-Recurrent Right Laryngeal Nerve: a Rare Anatomic Variation Encountered During a Total Thyroidectomy.

The non-recurrent laryngeal nerve (nRLN) is a rare anatomic variation that every head and neck surgeon must be aware of, in order to avoid intraoperative injury which leads to postoperative morbidity. We are reporting a case of a nRLN in a 47 year old female patient with medullary thyroid carcinoma who was surgically treated with total thyroidectomy and lymph node dissection. Both two inferior laryngeal nerves were identified, fully exposed and preserved along their cervical courses. However, we found that the right inferior laryngeal nerve was non-recurrent and directly arised from the cervical vagal trunk, entered the larynx after a short transverse course and parallel to the inferior thyroid artery. The safety of thyroid operations is dependent on high index of suspicion, meticulous identification and dissection of laryngeal nerves either recurrent or non-recurrent. This leads to minimum risk of iatrogenic damage of the nerves. Complete knowledge of the anatomy of these neural structures, including all their anatomic variations is of paramount importance.

Anatomical variation in the right non-recurrent laryngeal nerve reported from studies using pre-operative arterial imaging.

The right non-recurrent (inferior) laryngeal nerve (NRLN) is a rare anatomical variant associated with an arterial anomaly, the aberrant right subclavian artery (ARSA), that is detectable by pre-operative imaging (POI) using computed tomography and/or ultrasound. Most surgical studies have utilized two major types, NRLNs arising near the upper pole of the thyroid gland (type 1), vs. at a lower level (type 2) but with two subtypes defined by relationships to the inferior thyroid artery (ITA). This review found 8 English language surgical studies using POI that reported at least 1 NRLN and had anatomical information; of the 88 right NRLNs, 69.3% were classified as type 2 and 30.7% as type 1. Meta-analysis yielded a weighted proportion of 74.0% for type 2, but with substantial heterogeneity. For a subgroup of 5 POI studies with information on subtypes, 22 (59.5%) of 37 type 2 nerves were type 2a (i.e., running at or above the ITA). Similarly, a separate review of large surgical series without POI found that 60.4% of all 91 type 2 NRLNs were type 2a. The study findings should be relevant to the increasing numbers of anterior neck surgeries including bilateral thyroidectomies. A need was identified for studies on inter-observer reliability (agreement) among surgeons on NRLN types, and on injury rates (and related symptoms) by the type of NRLN.

Diverse Anatomical Configuration Of Recurrent Laryngeal Nerve In Relation To Inferior Thyroid Artery, An Experience With 51 Thyroidectomies.

BACKGROUND: Objective of the study is to elaborate the anatomical variants of recurrent laryngeal nerve in relation to inferior thyroid artery, encountered during thyroidectomy operation. It is descriptive, case series, conducted at the Department of Ear Nose & Throat, Combined Military Hospital, Abbottabad. The study was conducted from January 2016 to September 2017. METHODS: Fifty-one patients underwent extra-capsular thyroidectomy in general anaesthesia. The dissection was carried out in a standard way in all patients. Recurrent laryngeal nerves were identified and exposed in every patient, and their anatomical relations were recorded in database. RESULTS: Recurrent laryngeal nerve was seen over riding the ramification of inferior thyroid artery in majority of left sided dissected specimen, however on the right side the principal nerve was found to be ascending through the branches of inferior thyroid artery.. CONCLUSIONS: Iatrogenic vocal cord paralysis has sinister implication on quality of life of the patient undergoing thyroidectomy. Anatomic variants of recurrent laryngeal nerve are well known and frequent. The disastrous outcome of inadvertent recurrent laryngeal nerve trauma can be adequately prevented by thoroughly knowing its anatomical variants, and intra-operatively identifying and exposing the principal nerves.

Selective laryngeal reinnervation: can rerouting of the thyrohyoid nerve simplify the procedure by avoiding the use of a nerve graft?

PURPOSE: The objective of this study was to record the descriptive and metric anatomical characteristics of the thyrohyoid nerve with the aim of rerouting it in a selective laryngeal reinnervation procedure. METHODS: An anatomical study was performed on ten formalin-embalmed cadavers. The origin of the thyrohyoid nerve and the superior root of the ansa cervicalis, the location of the thyrohyoid nerve ending in the thyrohyoid muscle, and the recurrent laryngeal nerve were established. Then, a rerouting of the thyrohyoid nerve was performed. We measured the length of thyrohyoid nerve, the distance between the thyrohyoid nerve ending and the recurrent laryngeal nerve at the horizontal level of the cricothyroid joint before and after the rerouting, and the distance between the origin of the thyrohyoid nerve and the superior root of the ansa cervicalis. RESULTS: The thyrohyoid nerve was identified on both sides in all the cases. The average length of the thyrohyoid nerve was 27 mm. The end of the thyrohyoid nerve was found in 100% of the cases at the upper outer quarter of the thyrohyoid muscle. After the rerouting, an average reduction of 30% of the distance between the end of the thyroid nerve and the recurrent laryngeal nerve at the horizontal level of the cricothyroid joint was measured. CONCLUSION: The rerouting of the thyrohyoid nerve provided a reduction in the length of the nerve graft in laryngeal reinnervation. Moreover, the constancy of the thyrohyoid nerve and its characteristics make it a valuable anatomical base for laryngeal reinnervation and laryngeal innervated allotransplantation.