Branches Of Recurrent Laryngeal Nerve Research Articles

A prospective observational study on the anatomical variations of recurrent laryngeal nerve and its application in the prevention of injury during thyroid surgery in a tertiary care centre

BackgroundThyroid gland is the largest and most vascular structure among the endocrine glands. The recurrent laryngeal nerve and the superior laryngeal nerve are closely related to the thyroid gland; these nerves control voice and are vital in breathing. Anatomical preservation of the recurrent laryngeal nerve (RLN) is the gold standard in thyroid surgery. Visual identification of RLN has decreased the rates of permanent RLN palsy during thyroid and parathyroid operations. Prior knowledge about the branching patterns will help in predicting and preventing injury to the nerve during thyroid surgery.Aim and objectivesThe aim of the study is to observe the terminal branching pattern of recurrent laryngeal nerve before its entry into the larynx.MethodsAn observational study with 50 participants who fulfilled the inclusion and exclusion criteria were enrolled in the study. After a complete evaluation and pre-anaesthetic checkup, the patients were operated and intraoperative findings of RLN branching were recorded and compared for the study.ResultsIn our study, out of the 50 patients who underwent thyroid surgery during the course of the study, right-sided RLN branching was demonstrated in 25 patients (21 right hemithyroidectomy and 4 total thyroidectomy). Ten patients had RLN bifurcation, 7 had trifurcation, 5 had numerous branches, and 3 with no branching pattern were noted. Similarly, out of 29 patients (25 left hemithyroidectomy and 4 total thyroidectomy) in whom left-sided RLN branching was studied, bifurcation was seen in 10 patients, trifurcation in 12 patients, and multiple branching was observed in 7.ConclusionThe anatomical variations seen in RLN may increase the risk of vocal cord palsy due to its injury. Anatomical variations are categorized according to the original direction of the RLN and the number of terminal branches in the larynx. This classification aids in the identification and preservation of its branches, hence facilitating a safer thyroidectomy.

The relation of recurrent laryngeal nerve to inferior thyroid artery and extralaryngeal nerve branching may increase the risk of vocal cord paralysis in thyroidectomy

PurposeThe anatomical variations of the recurrent laryngeal nerve (RLN) are common during thyroidectomy. We aimed to evaluate the risk of RLN paralysis in case of its anatomical variations, retrospectively.MethodsThe patients with primary thyroidectomy between January 2016 and December 2019 were enrolled. The effect of age, gender, surgical intervention, neuromonitorisation type, central neck dissection, postoperative diagnosis, neck side, extralaryngeal branching, non-RLN, relation of RLN to inferior thyroid artery (ITA), grade of Zuckerkandl tubercle on vocal cord paralysis (VCP) were investigated.ResultsThis study enrolled 1070 neck sides. The extralaryngeal branching rate was 35.5%. 45.9% of RLNs were anterior and 44.5% were posterior to the ITA, and 9.6% were crossing between the branches of the ITA. The rate of total VCP was 4.8% (transient:4.5%, permanent: 0.3%). The rates of total and transient VCP were significantly higher in extralaryngeal branching nerves compared to nonbranching nerves (6.8% vs. 3.6%, p = 0.018; 6.8% vs. 3.2%, p = 0.006, respectively). Total VCP rates were 7.2%, 2.5%, and 2.9% in case of the RLN crossing anterior, posterior and between the branches of ITA, respectively (p = 0.003). The difference was also significant regarding the transient VCP rates (p = 0.004). Anterior crossing pattern increased the total and transient VCP rates 2.8 and 2.9 times, respectively.ConclusionRLN crossing ITA anteriorly and RLN branching are frequent anatomical variations increasing the risk of VCP in thyroidectomy that cannot be predicted preoperatively. This study is the first one reporting that the relationship between RLN and ITA increased the risk of VCP.

En bloc resection of total thyroid and bilateral central compartment lymph nodes via a gasless transoral approach in papillary thyroid carcinoma.

The current study presents a preliminary exploration of en bloc resection via a gasless transoral approach in papillary thyroid carcinoma. This study aimed to summarize and explore the efficacy and safety of en bloc resection of total thyroid and bilateral central compartment lymph nodes via a gasless transoral approach in patients with papillary thyroid carcinoma. This study was conducted between January 2021 and December 2021. It involved 30 patients with bilateral papillary thyroid carcinoma who had undergone en bloc resection of the total thyroid and bilateral central compartment lymph nodes via a gasless transoral approach using a three-trocar and four-instrument technique at The First Affiliated Hospital of the University of Science and Technology of China. The key steps and difficulties of the operation were summarized, and the clinicopathological characteristics and surgical complications of patients were analyzed. All operations were successful without conversion to open surgery. The pathological diagnosis was bilateral papillary thyroid carcinoma. The mean maximum tumor diameter was 0.85 ± 0.51cm (range 0.3-2.5 cm). There was no case of gross capsular invasion. The mean number of harvested central compartment lymph nodes was 11.36 ± 5.36. Central compartment lymph node metastases were found in 16 patients (53.3%) with a mean of 1.53 ± 2.39. On the other hand, lymphocytic thyroiditis was observed in 12 cases (40%), and microscopic capsular invasion was observed in five cases (16.6%). All patients had normal parathyroid hormone levels after the operation. However, one patient developed hoarseness after the operation due to injury of the recurrent laryngeal nerve branch, but there was no numbness of the mandible and lower lip or infection of the oral incision. The study revealed that the three-trocar and four-instrument technique can be used in the en bloc resection of total thyroid and bilateral central compartment lymph nodes via a gasless transoral approach without disconnecting the thyroid isthmus. As a result, the operation is considered effective and safe. Therefore, this technique may be a better surgical method for patients with bilateral thyroid cancer and cosmetic needs.

An Exposition on Surgical Experiences in Identification, Exposure, and Injuries of Recurrent Laryngeal Nerve (RLN) During Thyroid Operations: Gleanings, Narrative, and the Reflections.

Identifying and preserving the recurrent laryngeal nerve (RLN) is of paramount importance during thyroid surgeries. Iatrogenic injuries to RLN (RLNI) are considered one of the most serious and feared complications of thyroidectomies. Surgically, there are four routes/approaches (lateral, inferior, superior, and medial) for localizing and identifying the RLN. This study aims to estimate the incidence of RLNI in the context of various approaches taken intra-operatively for nerve localization and identification. This retrospective analytical study included 54 cases of thyroidectomies operated for various benign and malignant thyroid disorders in a tertiary care center from January 2018 to December 2020. Intraoperative search, identification, and dissection of the nerve were done with superior, inferior, medial, and lateral approaches. The chi-square test and exact test were used to analyze the data and p-value < 0.05 was considered significant. Pre- and post-operative recurrent laryngeal nerve evaluation was done with 90 degrees Hopkins laryngoscope. Overall in this series, the incidence of post-thyroidectomy RLNI was 3.7% and 3.7% for permanent and temporary nerve insults, respectively. Non-recurrent RLN on the right side was identified in one case and extra-laryngeal branching of RLN was identified in two cases. There was no statistically significant difference (p = 0.929) between the different approaches taken and the incidence of RLNI. The type of surgery and pathology also expressed no statistically significant relevance with the incidence of RLNI (p = 0.463 and p = 0.277, respectively). Adoption of a particular surgical approach to localize and identify RLN during thyroid surgery carries no statistically significant difference between RLNI and approaches taken. Meticulous handling and dissection of the tissue in the correct surgical plane are crucial determinants in preventing RLNIs.

갑상선 절제술 중 발견된 단일 신경 가지처럼 보였던 반회후두신경 분지 증례 1예

The recurrent laryngeal nerve (RLN) is an important structure that requires careful attention to be preserved during thyroidectomy. Because injury of this nerve results in vocal cord paralysis, which can lead to voice change, aspiration and even pneumonia. RLN often has branches which is vulnerable to nerve injury during surgery. RLN branch usually occurs close to the cricothyroid joint, or close to the junction between the nerve and the inferior thyroid artery. However, if the RLN branch is located lower than inferior thyroid artery, the risk of nerve damage could be increased. We report this rare anatomic variation of RLN case with a review of the literature.

Branching Patterns of Recurrent Laryngeal Nerve in Thyroidectomy Patients

Background: Historically, the Recurrent laryngeal nerve (RLN) has been considered to branch after it enters the larynx, but numerous studies have demonstrated that it often branches before. The wide variability of this extra laryngeal branching (ELB) has significant implications for the risk of iatrogenic injury. Accurate knowledge of anatomical variations of the recurrent laryngeal nerve (RLN) provides information to prevent inadvertent intraoperative injury.Objectives: Our study aimed to assess extra laryngeal branching of recurrent laryngeal nerve to find out branching patterns of RLN and to study whether there is any correlation between right and left side branching of RLN.Materials and Methods: This was a retrospective analysis conducted on patients of Thyroid surgeries that is total and Near-total thyroidectomies. This cross-sectional study was conducted in Hayatabad Medical Complex Peshawar from 1st Jan 2014 till 31st Dec 2020, with total of 269 patients. We excluded hemi thyroidectomies and recurrent cases.Results: The prevalence of single branching RLN was found to be 29.3% with 79 out of 269 patients. The branching pattern was found not statistically significant with age and gender. Surgeons need to pay special attention to the branching pattern of RLN so as to preserve it during surgery.Conclusion: The anatomy of the RLN is highly variable, and ELB is likely to have been underreported in intraoperative studies. Because of its high likelihood, the possibility of ELB needs to be assessed in patients to prevent iatrogenic injury and long-term postoperative complications.Key Words: Total thyroidectomy, Recurrent laryngeal nerve.Extralaryngeal branching.

Surgical treatment of unilateral laryngeal paralysis by selective reinnervation in thyroid surgery

State of the problem: One of the complications in thyroid surgery is a lesion of RLN which can be bilateral with a violation of respiratory function of the larynx and unilateral, in which the first priority is a violation of vocal function of the larynx. The most effective treatment for paralysis of the larynx is the method of laryngeal reinnervation, which can be non-selective, which is usually used in unilateral laryngeal paralysis and promotes reinnervation of both abductors and laryngeal adductors. Selective reinnervation is selectively focuses on the reinnervation of individual target muscles, so it is more often used in bilateral laryngeal paralysis. But despite this, it was used in unilateral laryngeal paralysis during surgery on the thyroid gland during intentional resection of the anterior branch of RLN with partial invasion of its tumour process. Aim: evaluation of the results of surgical treatment unilateral laryngeal paralysis by the method selective reinnervation in thyroidectomy. Materials and Methods: clinical case results of patient A. 15 years old with papillary thyroid cancer and metastases to regional lymph nodes of the neck (T4aN1M0) with absence disorders of laryngeal motility before surgery were analyzed. Examination of the larynx and voice examination were performed before surgery, 2-3 days and 6,12 months after surgery. Changes of laryngoscopic images and evaluation of the Indicators: maximum pho- nation time, fundamental frequency, noise to harmonic ratio, Jitter (loc), Shimmer (loc), Voice Handicap Index-30 (VHI-30), completed version of Jacobcon B. Results: Considering extralaryngeal bifurcation of the recurrent laryngeal nerve (RLN) and invasion of the tumor into the adductive branch of RLN on the left, its dissection was performed and end-to-end neuroanastomosis was formed, completed is selective laryngeal reinnervation. In the immediate postoperative period, patients complained of voice disorders. Study of voice parameters corresponded to severe voice disorders. Partial resumption of the mobility of the larynx and voice function was after 6 months. The signs of the laryngoscopic picture and the spectral analysis of the voice corresponded to the indicators before the operation after 12 months Сonclusions 1. Primary selective reinnervation of the larynx can be used to treat unilateral laryngeal paralysis under the following conditions: extralaryngeal branching of the recurrent laryngeal nerve (bifurcation), lesion of only one of its branches, which will provide sufficient coaxiality to perform anastomosis "end-to-end" and preservation electrical integrity of another branch. 2. This method allows you to restore the motility of the denervated vocal folds and the main indicators of the voice. 3. Given only one clinical case of treatment of unilateral laryngeal paralysis by selective reinnervation, this technique needs further study and refinement.

Evaluating intramuscular neural distribution in the cricopharyngeus muscle for injecting botulinum toxin

ObjectivesThe objective of this study was to determine the area in the cricopharyngeus muscle (CPM) where botulinum neurotoxin (BoNT) can be injected safely and effectively by evaluating neural distribution in the CPM. MethodsEleven specimens of the CPM were gathered from human cadavers. The anatomical relationship between the posterior cricoarytenoid muscle (PCAM) and the CPM was evaluated. Myelinated nerve fibers in the CPM were stained using modified Sihler's method. The CPM was classified into five zones according to the area accessible within the CPM via transcutaneous and transluminal approaches for BoNT injection as follows: i) lateral area including upper area (zone 1) and lower area (zone 2); ii) posterolateral area including upper area (zone 3) and lower area (zone 4); and iii) posterior area (zone 5). Neural distribution originating from the pharyngeal plexus and the extralaryngeal branches of recurrent laryngeal nerve (EBRLN) within each classified zone in stained specimens was determined. ResultsSix specimens (12 lateral areas, 12 posterolateral areas, and 6 posterior areas) were suitable for evaluating neural distribution within the CPM. Zone 1 was adjacent to the PCAM the most in all specimens. Nerve endings originating from the EBRLN were observed on four sides of zone 2 (33.3%, 4/12 sides) in three specimens (3/6, 50%). Neural distribution originating from the pharyngeal plexus was found on ten sides (83.3%, 10/12 sides) of zone 3 in five specimens (83.3%, 5/6 specimens) and on nine sides (75.0%, 9/12 sides) of zone 4 in five specimens (83.3%, 5/6 specimens). ConclusionThe posterolateral area (zone 3 and zone 4) is thought to be the most suitable area for alleviating the spasticity of CPM with a minimum dose of BoNT.

An Exploration of the Sympathetic Component of the Recurrent Laryngeal Nerve

INTRODUCTIONHigh interest in the recurrent laryngeal nerve (RLN) morphology has been dictated by the frequent iatrogenic injures that can result in multifaceted functional losses such as dysphagia, voice alteration, and breathing. Thus, RLN has been extensively studied on the macroscopic and histological levels. According to the literature, RLN is a mixed nerve carrying motor, sensory, and preganglionic parasympathetic fibers to the larynx and displays asymmetry in branching from the vagus nerve. Even though gross anastomoses between RLN and the cervical sympathetic trunk have been observed, the presence of sympathetic postganglionic fibers within RLN have not been addressed. The present study was conducted to determine if catecholaminergic fibers are present within the RLN using immunohistochemical analysis for tyrosine hydroxylase (TH).METHODSRLN samples were obtained from 19 formalin‐preserved adult human cadavers (male n=11, female n=8). Anastomoses with sympathetic structures were noted and documented before obtaining tissue samples for histological examination. Samples were collected one centimeter distal to the RLN branching site. All sections were prepared using Luxol fast blue staining to reveal the presence of myelinated and unmyelinated fibers and TH antibody staining was used to determine the presence of catecholaminergic fibers. Histological slides were then photographed and quantitative analysis of the images was conducted with ImageJ software by measuring of the effective surface area (ESA), TH‐positive, myelinated, and unmyelinated. We reported results as mean ± SEM.RESULTSNeural communications between right RLNs and sympathetic ganglia were observed in two whole‐body donors. No statistically significant differences in the number of the fascicles, ESA, myelinated, and unmyelinated fibers between right and left RLNs were found. TH‐positive fibers were detected bilaterally or unilaterally in 89.5% of examined donors. Bilateral absence of TH activity throughout the effective surface area was observed in two cases. TH‐positive nerve fiber area within the RLNs varied from 0% to 22.14% (Figure 1). The average of TH‐positive fibers on the right was 0.045 ± 0.011 mm2 (4.47% ± 1.1% of ESA) and 0.05 ± 0.015 mm2 (5.03±1.5% of ESA) on the left. A positive correlation between the number of unmyelinated fibers and TH‐positive component was found (P=0.022 and P=0.0026 on the right and left, respectfully). All parameters, such as fascicles, ESA, myelinated, unmyelinated, and TH‐positive fibers, occurred independently of age, gender, or conditions (p&gt;0.05).CONCLUSIONSympathetic postganglionic fibers within RLN nerve exist; however, there is a considerable difference in their number between individuals. However, the origin and functions of this component are ambiguous.SIGNIFICANCEKnowledge of the sympathetic component of RLN could assist in better understanding the physiological effects and adverse responses of vagus nerve stimulation therapy and the sequala of the RLN injury.

A Review on Vocal Cord Palsy: Complications and Management

Vocal cord paralysis is a multifaceted problem that affects people of all ages and is initially diagnosed by various healthcare providers. It is a common condition that occurs due to the obstruction of nerve impulses from the brain to the voice box. It ranges from slight hoarseness to fatal, life-threatening complications. To get to the exact diagnosis, determining the etiology of paralysis is essential. For restoration of normal function, accurate diagnosis has proven to be helpful. Vocal cord paralysis (VCP) is a. reasonably common condition caused by a vagus nerve or its recurrent laryngeal nerve branch disease process. The nerve’s longer length causes increased vulnerability. Peripheral lesions to the vagus are responsible for 90% of VCP (Vocal cord paralysis). Etiology includes scarring due to intubation or inflammatory disorders, iatrogenic causes like surgical traumas, malignancy, CNS pathologies like stroke, CNS tumors, and systemic diseases like ALS, Guillain barre syndrome. Vocal cord paralysis can cause consequences such as a weak cough, trouble swallowing, dysphagia, stridor, hoarseness, aspiration risk, granuloma formation, airway blockage, and a lower quality of life. Various treatment modalities like tracheostomy, usage of botulinum toxin, adenoidectomy, cordotomy, reinnervation, and gene therapy are used. For this narrative review, a literature search was undertaken using "unilateral and bilateral vocal cord palsy" and "dysphagia" in the Pubmed, Medline, and Embase databases. Bilateral vocal cord paralysis is a problematic and distressing condition that affects both adults and children. Surgical procedures such as tracheostomy, adenoidectomy, cordotomy, and laryngeal reinnervation have been used to treat this condition successfully. Treatment modalities should be individualized according to the patient's clinical features and physician's expertise.

Influence of intrathoracic vagotomy on the cough reflex in the anesthetized cat

Recurrent laryngeal afferent fibers are primarily responsible for cough in response to mechanical or chemical stimulation of the upper trachea and larynx in the guinea pig. Lower airway slowly adapting receptors have been proposed to have a permissive effect on the cough reflex. We hypothesized that vagotomy below the recurrent laryngeal nerve branch would depress mechanically or chemically induced cough. In anesthetized, bilaterally thoracotomized, artificially ventilated cats, thoracic vagotomy nearly eliminated cough induced by mechanical stimulation of the intrathoracic airway, significantly depressed mechanically stimulated laryngeal cough, and eliminated capsaicin-induced cough. These results support an important role of lower airway sensory feedback in the production of tracheobronchial and laryngeal cough in the cat. Further, at least some of this feedback is due to excitation from pulmonary volume-sensitive sensory receptors.

Anatomical, Functional, and Dynamic Evidences Obtained by Intraoperative Neuromonitoring Improving the Standards of Thyroidectomy.

The use of intraoperative neuromonitoring (IONM) is getting more common in thyroidectomy. The data obtained by the usage of IONM regarding the laryngeal nerves’ anatomy and function have provided important contributions for improving the standards of the thyroidectomy. These evidences obtained through IONM increase the rate of detection and visual identification of recurrent laryngeal nerve (RLN) as well as the detection rate of extralaryngeal branches which are the most common anatomic variations of RLN. IONM helps early identification and preservation of the non-recurrent laryngeal nerve. Crucial knowledge has been acquired regarding the complex innervation pattern of the larynx. Extralaryngeal branches of the RLN may contribute to the motor innervation of the cricothyroid muscle (CTM). Anterior branch of the extralaryngeal branching RLN has always motor function and gives motor branches both to the abductor and adductor muscles. In addition, up to 18% of posterior branches may have adductor and/or abductor motor fibers. In 70–80% of cases, external branch of superior laryngeal nerve (EBSLN) provides motor innervation to the anterior 1/3 of the thyroarytenoid muscle which is the main adductor of the vocal cord through the human communicating nerve. Furthermore, approximately 1/3 of the cases, EBSLN may contribute to the innervation of posterior cricoarytenoid muscle which is the main abductor of ipsilateral vocal cord. RLN and/or EBSLN together with pharyngeal plexus usually contribute to the motor innervation of cricopharyngeal muscle that is the main component of upper esophageal sphincter. Traction trauma is the most common reason of RLN injuries and constitutes of 67–93% of cases. More than 50% of EBSLN injuries are caused by nerve transection. A specific point of injury on RLN can be detected in Type 1 (segmental) injury, however, Type 2 (global) injury is the loss of signal (LOS) throughout ipsilateral vagus-RLN axis and there is no electrophysiologically detectable point of injury. Vocal cord paralysis (VCP) develops in 70–80% of cases when LOS persists or incomplete recovery of signal occurs after waiting for 20 min. In case of complete recovery of signal, VCP is not expected. VCP is temporary in patients with incomplete recovery of signal and permanent VCP is not anticipated. Visual changes may be seen in only 15% of RLN injuries, on the other hand, IONM detects 100% of RLN injuries. IONM can prevent bilateral VCP. Continuous IONM (C-IONM) is a method in which functional integrity of vagus-RLN axis is evaluated in real time and C-IONM is superior to intermittent IONM (I-IONM). During upper pole dissection, IONM makes significant contributions to the visual and functional identification of EBSLN. Routine use of IONM may minimalize the risk of nerve injury. Reduction of amplitude more than 50% on CTM is related with poor voice outcome.

The Most Common Anatomical Variation of Recurrent Laryngeal Nerve: Extralaryngeal Branching.

Objective:Extralaryngeal branching of recurrent laryngeal nerve (RLN) is frequent. In various studies, detection rate of extralaryngeal nerve branching was increased by intraoperative neuromonitorization (IONM). Our aim was evaluation of the relationship between the features of extralaryngeal branching of RLN and other anatomic variations in thyroidectomy patients under the guidance of IONM.Methods:Patients underwent thyroidectomy using IONM between January 2016 and December 2019 and whose RLNs were fully explored till the nerve’s entry point to the larynx, were enrolled to the study. Extralaryngeal branching of RLN was accepted as branching of the nerve at a ≥5 mm distance from its laryngeal entry point and having its all branches entering the larynx. Entrapment of RLN at the region of ligament of Berry (BL) by a vascular structure or posterior BL and relationship between RLN and inferior thyroid artery (ITA) was evaluated.Results:Out of 696 patients meeting the inclusion criteria, 1127 neck sides (536F and 160M) were evaluated. Mean age was 49.1±13.4 (range; 18–89). Nerve branching ratio was 35.3% and was higher in females than males (38.2%vs.25.8%, p<0.0001, respectively). Extralaryngeal branching of RLN was detected in 398 (35.3%) out of 1127 nerves. A total of 368 (92.5%) RLNs had two, 27 (6.8%) nerves had three, and 3 (0.7%) had multiple branches. RLN crossed anterior to and between branches of ITA more frequently in branching nerves than non-branching nerves (47.7 vs. 44.4% and 12.8% vs. 7.6%, respectively) but crossed posterior to ITA less frequently in branching nerves (38.5% vs. 48%, respectively, p=0.001). Entrapment of RLN at the region of BL was higher in branched nerves (25.9% vs. 17.5%, respectively, p=0.001). Entrapment of RLN wasmore frequent at the right side than left side both in branching (31.5% vs.19.4%, respectively, p=0.008) and non-branching nerves (20.6% vs. 14.4%, respectively).Conclusion:Extralaryngeal branching of RLN is not rare and mostly divided into two branches. Branching ratio is higher in females than males. In branching nerves, rate of crossing anterior to and between branches of ITA was higher, in non-branching nerves, rate of crossing posterior to ITA was higher. In branching nerves, possibility of entrapment of RLN at the region of BL was higher. Both in branching and non-branching nerves, entrapment of RLN at the region of BL was higher at the right side. Extralaryngeal branching, relationship between RLN and ITA, and entrapment of RLN at the region of BL are frequently seen and variable anatomic variations and cannot be foreseen preoperatively. Most of the extralaryngeal branches and their relationship with other variations can be detected by finding RLN at the level of ITA and following RLN until its entry point to the larynx.

Clinical observation of end-to-end neuroanastomosis in the treatment of complete injury of the unilateral recurrent laryngeal nerve.

Complete injury of the recurrent laryngeal nerve (RLN) is a serious complication of thyroid surgery. Increasingly researches focus on the voice recovery of patients with RLN injury. This paper studied the effect of immediate end-to-end neuroanastomosis after complete injury of the unilateral RLN during thyroid surgery on postoperative vocal function. Thirteen patients who underwent end-to-end neuroanastomosis for the treatment of complete injury of the unilateral RLN caused by thyroid surgery in Hunan Provincial People's Hospital between October 2009 and January 2020 were selected. The basic information, cause of RLN injury, postoperative voice recovery, recovery time, and subjective assessment of voice by auditory perception results (Grade, Roughness, Breathiness, Asthenia, and Strain, the GRBAS score) of the patients were recorded. Among the 13 cases with RLN injury, the cause of RLN injury in 10 cases was transection by sharp instruments, and the voice was recovered one day after the operation. The cause of RLN injury in one case was suture of the RLN branch, and the voice was recovered one day after the operation. The cause of RLN injury in two cases was thermal injury, and the times for voice recovery after end-to-end neuroanastomosis were 3 and 4 months. The patients with a GRBAS score of 0 or 1 recovered their voice one day after the operation. The GRBAS score reached 1 in the two thermal injury cases, with voice recovery at 3 and 4 months after surgery. By 6 months, the voice recovery rate of the patients was 100%. After complete injury of the unilateral RLN, immediate end-to-end anastomosis of the RLN can maximally preserve the postoperative vocal function of patients.

Use of intraoperative neural monitoring for prognostication of recovery of vocal mobility and reduction of permanent vocal paralysis after thyroidectomy.

The benefits of intraoperative neural monitoring (IONM) of recurrent laryngeal nerve (RLN) on post-thyroidectomy vocal cord palsy (VCP) rates are contentious. We wished to study impact of IONM on permanent VCP after thyroidectomy. Retrospective review of prospective series of 1011 (1539 nerves-at-risk) patients undergoing thyroidectomy without (418, group 1) and with (583, group 2) IONM. There were three recognized nerve injuries in group 1, vs one in group 2 (P = .3). There were no differences in overall VCP rates. However, patients in group 2 with immediate postoperative VCP had higher likelihood of full recovery than patients in group 1 (55 of 56 vs 23 of 29 patients, P = .01), and lower incidence of total permanent VCP (2 of 917 vs 9 of 647 patients, P = .01). Among patients with immediate postoperative VCP after thyroidectomy, IONM is associated with a higher likelihood of regaining normal vocal function. This may be related to better identification of RLN branching in IONM cases.

Anatomical Variations in Recurrent Laryngeal Nerves in Thyroid Surgery.

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. 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. (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. 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.

A Cadaveric Study of Occurrence of Extralaryngeal Branches of the Recurrent Laryngeal Nerve with Reference to its Importance in Thyroid Surgery

Introduction&#x0D; Recurrent Laryngeal Nerve Palsy (RLNP) is the most common complication of thyroid surgery. Patients complain of hoarseness of voice and sometimes variable amount of respiratory distress due to palsy of recurrent laryngeal nerve (RLN), extra laryngeal branches of which are often ligated along with Inferior Thyroid Artery (ITA) during thyroidectomy. So prevalence and variable pattern of extra laryngeal nerve branches (ELNB) of RLN should be known to the thyroid surgeon to avoid post operative complications.&#x0D; Materials and Methods &#x0D; Dissection was carried on the neck of properly embalmed 25 adult cadavers including both sexes in the dissection hall to study extra laryngeal nerve branches (ELNB) of 50 RLN specimens.&#x0D; Results&#x0D; Out of 50 RLN, 13 nerves (26%) have ELNBs. Only in 4 cadavers (16%) they are bilateral. In 9 cases RLN branches were surrounding either single trunk of ITA or branches of the artery. In rest of the 4 cases ELNBs were passing entirely either in front or behind the ITA&#x0D; Conclusion&#x0D; The gold standard for preservation of the RLN during thyroid surgery is still visual anatomical identification. Proper dissection and anatomical identification of the RLN and all its branches is very important prior to the clamping of the ITA and all its branches.

Functional identification of abductor and adductor branches for laryngeal transplantation.

This is a feasibility study of functional identification of the abductor and adductor recurrent laryngeal nerve branches, which could be used in the donor's larynx for functional laryngeal transplantation. The study was performed on swine (n = 3) and human (n = 4) models of a donor larynx. The recurrent laryngeal nerve and its branches were found. Using stimulator, abductor and adductor branches were identified, and glottis closing and opening were captured with an endoscope. The result was positive if two ENT specialists noticed at least one adduction and one abduction movement in the same subject. It was obtained in three out of three swine and three out of four humans. This study shows a way of reinnervation of a transplanted larynx which might result in a functional organ. It describes the first step of the procedure: functional identification of the abductor and adductor branches of the recurrent laryngeal nerve in the donor before the larynx is excised for transplantation.

Modification of the Surgical Strategy for the Dissection of the Recurrent Laryngeal Nerve Using Continuous Intraoperative Nerve Monitoring.

The aim of this study was to describe first experiences and changes in management using continuous intraoperative neuromonitoring (C-IONM) in thyroid and parathyroid surgery. Retrospective analysis of patients who underwent surgery with C-IONM since 2012. Surgical maneuvers were modified when electrophysiologic events occurred. Patients with persistent loss of signal (LOS) underwent postoperative laryngoscopy. One hundred and one patients (of 1586 neck surgeries) were included and 19 had events: In 13 these were temporary (resolved before end of surgery) and led to intraoperative modifications in surgical approach; in all cases traction was released, and in 8, recurrent laryngeal nerve (RLN) approach was changed [superior approach (2), inferior approach (2), both (4)]. Six patients had persistent LOS (5.9%, present at end of procedure), with RLN palsy (RLNP) on postoperative day 1: In three, LOS occurred at electrode placement on the vagus nerve, leading to distal placement of the electrode allowing ipsilateral dissection under continuous monitoring; all three had complete recovery at 6months. In the three other patients, LOS occurred on the RLN: one probable thermal, one traction lesion and one accidental section of the anterior RLN branch. The RLN recovered within 6months in two patients, and in the third, RLNP persisted after 6months (1/101=1%). C-IONM provides real-time evaluation of the RLN function, allowing for adaptation of surgical maneuvers to prevent RLNP. It seems particularly useful in difficult cases like redo neck surgery, invasive thyroid cancer and intrathoracic or large goiter. Care should be given at electrode placement on the vagus nerve.

Extralaryngeal division of the recurrent laryngeal nerve: A common and asymmetric anatomical variant.

Recognition of extralaryngeal branching of the recurrent laryngeal nerve is crucial because prevention of vocal cord paralysis requires preservation of all branches of the recurrent laryngeal nerve. We assessed the prevalence of extralaryngeal branching of the recurrent laryngeal nerve and the median branching distance from the point of bifurcation to the entry point of the nerve into the larynx. Prospective operative data on recurrent laryngeal nerve branching were collected from 94 patients who underwent thyroid or parathyroid surgery between September 2011 and May 2012. A total of 161 recurrent laryngeal nerves were examined (82 right, 79 left). Overall, 77 (47.8%) of 161 recurrent laryngeal nerves were bifurcated before entering the larynx. There were 36 (43.9%) branching nerves on the right and 41 (51.9%) branching nerves on the left, and there was no significant difference between the sides in terms of branching (p=0.471). Among 67 patients who underwent bilateral exploration, 28.4% were found to have bilateral branching, 40.3% had unilateral branching, and the remaining 31.3% had no branching. The median branching distance was 15 mm (5-60mm). Extralaryngeal division of recurrent laryngeal nerve is a common and asymmetric anatomical variant. These variations can be easily recognized if the recurrent laryngeal nerve is identified at the level of the inferior thyroid artery and then dissected totally to the entry point of the larynx. Inadvertent division of a branch may lead to vocal cord palsy postoperatively, even when the surgeon believes the integrity of the nerve has been preserved.