Primary Nonselective Laryngeal Reinnervation in Iatrogenic Acute Recurrent Laryngeal Nerve Injury: Case Series and Literature Review.

Treating an acutely injured recurrent laryngeal nerve by primary nonselective laryngeal reinnervation (LR) during thyroidectomy is encouraged to minimize postoperative morbidity. Performing a concurrent transoral temporary injection laryngoplasty (IL) may improve the patient's voice while waiting for the effect of successful reinnervation. Chronological multidimensional voice outcomes (qualitative and quantitative) and combination of the primary nonselective LR with concurrent transoral IL were not explicitly demonstrated in previous cases that published the literature. In this study, the authors presented the multidimensional voice parameters of 3 patients undergoing primary nonselective LR with concurrent IL during thyroidectomy. The parameters were measured at different time points (2 weeks and 1, 3, 6, and 12 months) following the surgery. Laryngeal electromyography was done at 1 to 2 months and 12 months postsurgery. The results showed that the voices, qualitatively and quantitatively, were within normal range at within 3 months postintervention. The parameters were slightly beyond the normal limit at 3 months and returned to normal at 6 months postintervention and beyond. The LEMG depicted evidence of successful reinnervation in which the motor unit was normal comparable to the opposite normal vocal fold.

The Importance of Mapping Vagus and Laryngeal Nerves Monitoring During Thyroid Surgery.

OBJECTIVE: To determine the location of thyroid-related nerves by nerve monitoring and demonstrate the usefulness of Nerve Integrity Monitor in thyroid surgery. STUDY DESIGN: Descriptive study. PLACE AND DURATION OF STUDY: Department of General Surgery, University of Health Sciences, Istanbul Training and Research Hospital, Turkey, from February 2017 to January 2020. METHODOLOGY: Patients, who underwent thyroid surgery, were evaluated for age, gender, preoperative diagnosis, type of surgery, histopathological result, postoperative hoarseness, and postoperative vocal cord examinations. The vagus nerve, recurrent laryngeal nerve (RLN), and superior laryngeal nerve (SLN) were mapped by nerve monitoring. RESULTS: A total of 328 patients were included in this study. On both sides, the vagus nerve was most often located in the posterior of the internal carotid artery and internal jugular vein and less frequently anterior to this vein. A total of 303 right RLNs and 305 left RLNs were verified. The SLN was visualised or motor activity was verified by nerve monitoring on the right side in 181 patients and on the left side in 179 patients. The SLN's location was classified most frequently as type I and least frequently as type IIb on the right and left sides. CONCLUSION: The reported variations, the experience of the surgeon, and these anatomical markers cannot be adequate in preventing nerve injuries. Furthermore, the variations can be identified more clearly peroperatively with the use of nerve monitoring. KEY WORDS: Laryngeal nerves, Nerve mapping, Nerve monitoring, Nervus vagus, Thyroid surgery, Zuckerkandl tubercles.

Intra-operative nerve monitoring and recurrent laryngeal nerve injury during thyroid surgery: a network meta-analysis of prospective studies.

PURPOSE: Recurrent laryngeal nerve (RLN) injury is a feared complication of thyroid surgery occurring in 1-5% of cases. The present approaches to RLN preservation include RLN visualization with no nerve monitoring (No-NM), intermittent intra-operative nerve monitoring (I-IONM) and continuous intra-operative nerve monitoring (C-IONM). There is ambiguity as to which of these strategies should be the preferred method of RLN preservation. METHODS: A systematic review of the PubMed, Embase and the Cochrane Collaboration databases was undertaken with network meta-analysis (NMA) performed according to the PRISMA and Cochrane Collaboration guidelines. A Bayesian NMA was conducted using R packages netmeta with outcomes expressed as odds ratios (ORs) with 95% credible intervals (CrI). Only prospective studies were included. RESULTS: Eighteen studies met inclusion criteria, including 22,080 patients and 40,642 nerves at risk (NAR). Overall, 23,364 NARs (57.5%) underwent I-IONM, 17,176 (42.3%) No-NM and 98 (0.2%) underwent C-IONM. There were no significant differences between groups regarding the incidence of permanent RLN injury following thyroid surgery (I-IONM vs.No-NM, OR 0.84, 95% CrI 0.55-1.19; C-IONM vs. No-NM, OR 0.44, 95% CrI 0.02-5.00). Pooled analysis showed that IONM (I-IONM or C-IONM) demonstrated a protective effect versus No-NM in reducing the incidence of transient RLN injury (OR 0.75, 95% CI 0.59-0.97, p = 0.03). CONCLUSIONS: IONM strategies did not significantly reduce the incidence of permanent RLN injury following thyroid surgery. However, the small number of C-IONM NARs limits conclusions that may be drawn. Further well-designed prospective studies will be required to definitively assess the utility of C-IONM.

Safety Parameters of Quantum Molecular Resonance Devices During Thyroid Surgery: Porcine Model Using Continuous Neuromonitoring.

Objectives: Quantum molecular resonance (QMR) devices have been applied as energy-based devices in many head and neck surgeries; however, research on their use in thyroid surgery is lacking. This study aimed to investigate the safety parameters of QMR devices during thyroidectomy when dissection was adjacent to the recurrent laryngeal nerve (RLN). Methods: This study included eight piglets with 16 RLNs, and real-time electromyography (EMG) signals were obtained from continuous intraoperative neuromonitoring (C-IONM). QMR bipolar scissor (BS) and monopolar unit (MU) were tested for safety parameters. In the activation study, QMR devices were activated at varying distances from the RLN. In the cooling study, QMR devices were cooled for varying time intervals, with or without muscle touch maneuver (MTM) before contacting with the RLN. Results: In the activation study, no adverse EMG change occurred when QMR BS and MU were activated at distances of 2 mm or longer from the RLNs. In the cooling study, no adverse EMG change occurred when QMR BS and MU were cooled in 2-second intervals or immediately after MTM. Conclusion: QMR devices should be carefully used when performing RLN dissection during thyroid surgery. According to the activation and cooling safety parameters in this study, surgeons can avoid RLN injury by following standard procedures when using QMR devices.

Intraoperative Neuromonitoring: Evaluating the Role of Continuous IONM and IONM Techniques for Emerging Surgical and Percutaneous Procedures.

Intraoperative nerve monitoring (IONM) is a tool used during thyroid surgery to assist in the identification of the recurrent laryngeal nerve (RLN). Multiple IONM systems that exist for thyroidectomy require intubation with an endotracheal tube. Given that one of the advantages of thermal ablation procedures, such as radiofrequency ablation, is that they can be done safely without the use of general anesthesia, nerve monitoring systems that utilize cutaneous surface electrodes have been developed, though are not widely available in the United States. This article will review the use of IONM for RFA including the cutaneous surface electrode system.

Recurrent Laryngeal Nerve Injury in Thermal Ablation of Thyroid Nodules-Risk Factors and Cause Analysis.

CONTEXT: Recurrent laryngeal nerve (RLN) injury is a complication of thermal thyroid nodule treatment. OBJECTIVE: We investigated the influencing factors of RLN injury in patients who underwent thermal ablation of thyroid nodules. METHODS: The data of 1004 patients (252 male, 752 female; median age 44 years) who underwent thermal thyroid nodule ablation were retrospectively reviewed. Patients were divided into benign cystic, benign solid, and papillary thyroid cancer (PTC) groups. The parameters related to RLN injury were analyzed, including the largest diameter, location of the nodules, and shortest distance of the nodule to thyroid capsule and tracheoesophageal groove (TEG). Univariate and multivariate analyses were performed to select risk factors for RLN injury. RESULTS: The RLN injury rate was higher in PTC (6.3%) than in benign cystic (1.2%, P = 0.019) and solid nodules (2.9%, P = 0.018). PTC subgroup analysis showed that the RLN injury rate was higher in T1b (10.7%) and T2 (28.6%) PTC than in T1a PTC (5.0%, P < 0.05). In the PTC group, TEG distance, anterior capsule distance, median capsule distance, posterior capsule distance, and maximum nodule diameter were risk factors for RLN injury. The logistic regression fitting of the nomogram showed high prediction efficiency (C-Index 0.876). The main cause of RLN injury was insufficient medial isolating fluid (MIF). The safety thicknesses of MIF for benign cystic, benign solid, and PTC nodules were 3.1 mm, 3.7 mm, and 3.9 mm, respectively. CONCLUSION: Several risk factors for RLN injury should be considered before thermal ablation of thyroid nodules. The RLN injury rate could be predicted with the nomogram.

Outcomes in Pediatric Thyroidectomy: Results From a Multinational, Multi-institutional Database.

OBJECTIVE: Traditionally, data regarding thyroidectomy were extracted from billing databases, but information may be missed. In this study, a multi-institutional pediatric thyroidectomy database was used to evaluate recurrent laryngeal nerve (RLN) injury and hypoparathyroidism. STUDY DESIGN: Retrospective multi-institutional cohort study. SETTING: Tertiary care pediatric hospital systems throughout North America. METHODS: Data were individually collected for thyroidectomies, then entered into a centralized database and analyzed using univariate and multivariable regression models. RESULTS: In total, 1025 thyroidectomies from 10 institutions were included. Average age was 13.9 years, and 77.8% were female. Average hospital stay was 1.9 nights and 13.5% of patients spent at least 1 night in the pediatric intensive care unit. The most frequent pathology was papillary thyroid carcinoma (42%), followed by Graves' disease (20.1%) and follicular adenoma (18.2%). Overall, 1.1% of patients experienced RLN injury (0.8% permanent), and 7.2% experienced hypoparathyroidism (3.3% permanent). Lower institutional volume (odds ratio [OR], 3.57; 95% CI, 1.72-7.14) and concurrent hypoparathyroidism (OR, 3.51; 95% CI, 1.64-7.53) correlated with RLN injury on multivariable analysis. Graves' disease (OR, 2.27; 95% CI, 1.35-3.80), Hashimoto's thyroiditis (OR, 4.67; 95% CI, 2.39-9.09), central neck dissection (OR, 3.60; 95% CI, 2.36-5.49), and total vs partial thyroidectomy (OR, 7.14; 95% CI, 4.55-11.11) correlated with hypoparathyroidism. CONCLUSION: These data present thyroidectomy information and complications pertinent to surgeons, along with preoperative risk factor assessment. Multivariable analysis showed institutional volume and hypoparathyroidism associated with RLN injury, while hypoparathyroidism associated with surgical indication, central neck dissection, and extent of surgery. Low complication rates support the safety of thyroidectomy in pediatric tertiary care centers.

A novel method to reconstruct right recurrent laryngeal nerve by transforming into nonrecurrent laryngeal nerve: The end-to-free vagal laryngeal branch end anastomosis.

The objective of this study is to demonstrate a novel method for the reconstruction of right recurrent laryngeal nerve (RLN) by transforming into nonrecurrent RLN: the end-to-free vagal laryngeal branch end anastomosis. Here we report a case of locally advanced thyroid carcinoma. The patient underwent radical thyroid surgery with inevitably partial RLN resection and immediate right RLN reconstruction at our institution. With the guidance of intraoperative neuromonitoring (IOMN), we completed a novel end-to-free vagal laryngeal branch end anastomosis. The whole procedure was deliberately monitored by IOMN. Surgeons can procure adequate free nerve for tension-free anastomosis by transforming the right RLN into nonrecurrent nerve. Follow-up laryngoscope showed improved adductory movement of the right arytenoid. The end-to-free vagal end anastomosis is an effective way to reconstruct segmental nerve resection of right RLN. Its long-term postoperative result needs to be further warranted.

Clinical Experience of Use of Percutaneous Continuous Nervemonitoring in Robotic Bilateral Axillo-Breast Thyroid Surgery.

Introduction and Objective: There is a need for a simplified technique for C-IONM in robotic surgery. The primary aim of this study was to describe our clinical experience with the use of percutaneous C-IONM in robotic bilateral axillary thyroid surgery. Methods: This study prospectively enrolled 304 consecutive patients who underwent robotic thyroidectomy via the bilateral axillo-breast approach and standardized C-IONM via percutaneous probe stimulation. Results: 323 RLNs were analyzed. C-IONM with percutaneous probes was feasible in all cases. During this study, we did not record any cases of probe displacement, and no additional robotic maneuvers were required. The average stimulation intensity was 2 mA. There were no adverse local or systemic C-IONM side effects. The mean time required for probe positioning was 3 minutes. The EMG amplitude signal of 48 RLNs decreased significantly, < 50% from the original V1 signal. In these cases, the surgical procedure was modified. Conclusion: The proposed percutaneous C-IONM provides a simplification of the continuous monitoring procedure for robotics. The advantage of percutaneous C-IONM is that it does not require additional trocar space, repeated instrument changes, and unmodified cosmesis. To our knowledge, this is the first study on the application of percutaneous C-IONM in robotic thyroid surgery.

Immediate Intraoperative Repair of the Recurrent Laryngeal Nerve in Thyroid Surgery.

OBJECTIVES: Recurrent laryngeal nerve (RLN) injury is a recognized risk during thyroid and parathyroid surgery and can result in significant morbidity. The aim of this review paper is to consider the optimal approach to the immediate intraoperative repair of the RLN during thyroid surgery. METHODS: A PubMed literature search was performed from inception to June 2020 using the following search strategy: immediate repair or repair recurrent laryngeal nerve, repair or reinnervation recurrent laryngeal nerve and immediate neurorraphy or neurorraphy recurrent laryngeal nerve. RESULTS: Methods of immediate intraoperative repair of the RLN include direct end-to-end anastomosis, free nerve graft anastomosis, ansa cervicalis to RLN anastomosis, vagus to RLN anastomosis, and primary interposition graft. Techniques of nerve repair include micro-suturing, use of fibrin glue, and nerve grafting. Direct micro-suture is preferable when the defect can be repaired without tension. Fibrin glue has also been proposed for nerve repair but has been criticized for its toxicity, excessive slow reabsorption, and the risk of inflammatory reaction in the peripheral tissues. When the proximal stump of the RLN cannot be used, grafting could be done using transverse cervical nerve, supraclavicular nerve, vagus nerve, or ansa cervicalis. CONCLUSIONS: Current evidence is low-level; however, it suggests that when the RLN has been severed, avulsed, or sacrificed during thyroid surgery it should be repaired intraoperatively. The immediate repair has on balance more advantages than disadvantages and should be considered whenever possible. This should enable the maintenance of vocal cord tone, better and prompter voice recovery and avoidance of aspiration. Laryngoscope, 131:1429-1435, 2021.

Selective vagus-recurrent laryngeal nerve anastomosis in thyroidectomy with cancer invasion or iatrogenic transection.

PURPOSE: Immediate recurrent laryngeal nerve (RLN) reconstruction at the time of thyroid cancer extirpation can provide excellent postoperative phonatory function. This study is to present our experience with the methods of RLN reconstruction, and to evaluate the role of selective vagus to RLN anastomosis (SVR) in thyroidectomy. METHODS: Respective review of RLN reconstruction in thyroid surgery from January 2004 to October 2018 was conducted in two tertiary referral academic medical centers. Immediate RLN reconstruction was performed for primary thyroidectomy patients with intraoperative nerve tumor invasion or iatrogenic transection. Laryngofiberoscopic examination, voice evaluation of maximum phonation time, and GRBAS scale were performed preoperatively, on the second day after surgery, and monthly postoperatively for the first year. RESULTS: A total of 37 patients were enrolled. Twenty-nine RLNs were resected caused by tumor-associated trauma; the other nerves were inadvertently transected. Direct anastomosis (DA) was performed in eight patients, free nerve graft (FNG) was performed in four patients, ansa cervicalis to RLN anastomosis (ARA) was performed in eight patients, and SVR was performed in 17 patients. The mean periods from the reinnervation surgery of DA, SVR, ARA, and FNG to the phonation recovery were 46 ± 19 (days), 41 ± 29 (days), 83 ± 21 (days), and 137 ± 32 (days), respectively. There were improvements in the GRBAS scale of perceptual voice quality at 1 month for DA and SVR, 2months for ARA. CONCLUSIONS: Intraoperative SVR reinnervation demonstrated voice improvement postoperatively and might be an effective treatment for thyroidectomy-related permanent unilateral vocal cord paralysis.

Precision treatment of post pneumonectomy unilateral laryngeal paralysis due to cancer.

Aim: The aim of this study is to assess the efficacy of external laryngeal medialization acquired through a Gore-Tex implant in a 45 patients affected by unilateral vocal fold paralysis in abduction after pneumonectomy. Method: The cohort of patients was made up of 30 male (73.1%) and 11 female patients (26.9%) with an average age of 66.7 years in a range between 46 and 78 years. Results: The results were analyzed with the objective and subjective analysis of voicing and swallowing. In 95.2% of cases, voice and swallow improvement with statistically significant evidences. Conclusion: We can conclude that Gore-Tex implantation is a simple, reproducible and minimally invasive procedure for management of selected cases of vocal fold unilateral paralysis in the abductory position.

Early Injection Laryngoplasty After Surgery: 30 Cases and Proposed Aspiration Assessment Protocol.

Vocal fold movement impairment may significantly compromise postoperative recovery and quality of life of patients following thoracic or cardiothoracic surgery or prolonged intubation. The literature is limited and there is no standard screening protocol for the optimal postoperative swallowing and aspiration evaluations. We performed retrospective review of adult patients undergoing early vocal fold (VF) injection laryngoplasty for acute postoperative Vocal fold movement impairment (<30 days) that had both pre- and postinjection speech language pathologist (SLP) performed swallowing/aspiration evaluations. Records were reviewed for demographics, clinical characteristics, procedural details, and short-term outcome measures of oral intake. In total, 30 patients were included, and had data on swallowing/aspiration studies before and after the VF injection laryngoplasty. Most of the patients were injected within 5 days following the laryngologist evaluation and within 14 days following the iatrogenic recurrent laryngeal nerve injury (23/30, 76.7%). The majority of patients were injected at the bedside by awake transcutaneous injection (22/30, 73.3%), six patients were injected in the operating room under general anesthesia, and two at the outpatient clinic. Pre- and postinjection SLP evaluations included clinical bedside assessment or instrumental evaluation. Following VF injection laryngoplasty, oral diet advancement was noted in 81.8% of the patients that were nil per os before the injection (18/22). No complications were noted. In conclusions, acute VFMI following surgery requires immediate diagnosis and therapeutic strategy to minimize postoperative complications and to overcome impairments in the voice, swallow, and cough. Otolaryngology-SLP interdisciplinary aspiration and swallowing assessment protocol is proposed based on our experience and an extensive literature review.

Morphometric Differences in the Recurrent Laryngeal Nerve in Patients with Vocal Fold Paralysis.

OBJECTIVES: Injury to the recurrent laryngeal nerve (RLN), if severe enough, can result in vocal fold paralysis. Reinnervation surgery can improve patient outcomes, but previous studies have reported a negative correlation between time since onset of paralysis and surgical outcomes. The ability of the paralyzed nerve to serve as a conduit for donor nerve fibers may be a factor in the success of reinnervation; however, changes in RLN composition after paralysis have not been well studied. Therefore, we investigated the morphometric composition of explanted RLN sections from patients who had experienced vocal fold paralysis for varying length of times. METHODS: Nine nerve sections from unilateral vocal fold paralysis (UVP) patients and seven control nerve sections were analyzed for morphometric parameters including fascicular area, fiber count, fiber density, fiber packing, mean g-ratio, and fiber diameter distribution. Nerves from UVP patients were also compared as a function of time since UVP onset. RESULTS: In comparison to control nerves, paralyzed nerves were found to have significantly lower fiber densities and fiber packing, higher mean g-ratio values, and a shift in diameter distributions toward smaller diameter fibers. With respect to paralysis duration, no significant differences were observed except in fiber diameter distributions, where those with paralysis for >2 years had distributions that were significantly shifted toward smaller diameter fibers. CONCLUSIONS: The morphometric data presented here suggest that correlations between the time since onset of vocal fold paralysis and reinnervation outcomes may be due to fiber size changes in the paralyzed nerve over time.

Comparison of primary repair and repair with polyglycolic acid coated tube in recurrent laryngeal nerve cuts (an experimental study).

BACKGROUND: Recurrent laryngeal nerve (RLN) injury is an important complication of thyroid surgery. In our study, we aimed to compare the effects of primary repair and polyglycolic acid (PGA) coated tube repair on nerve function and regeneration in RLN cuts in rats. METHODS: Twenty seven rats were used for the study. Group-1 with only nerve cuts, group-2 with primary repair, and group-3 with conduit repair. The study was planned over two-stage surgery. In the first step, nerve defect formation and nerve repair were performed in the same session. In the second step, samples were taken from the subjects for histopathological. RESULTS: Vocal cord mobility was proportionally higher in group-3 than other groups. However, there was no statistically significant difference between the groups (p < 0.239). The mean number of highest axons were detected the group-3. CONCLUSIONS: We think that PGA coated conduit can provide a more accurate orientation of nerve fibers by creating an isolated environment when compared to the primary repair. And this may be the cause of functional improvement in the nerve.

A Surgical Mouse Model for Advancing Laryngeal Nerve Regeneration Strategies.

Iatrogenic recurrent laryngeal nerve (RLN) injury is a morbid complication of anterior neck surgical procedures. Existing treatments are predominantly symptomatic, ranging from behavioral therapy to a variety of surgical approaches. Though laryngeal reinnervation strategies often provide muscle tone to the paralyzed vocal fold (VF), which may improve outcomes, there is no clinical intervention that reliably restores true physiologic VF movement. Moreover, existing interventions neglect the full cascade of molecular events that affect the entire neuromuscular pathway after RLN injury, including the intrinsic laryngeal muscles, synaptic connections within the central nervous system, and laryngeal nerve anastomoses. Systematic investigations of this pathway are essential to develop better RLN regenerative strategies. Our aim was to develop a translational mouse model for this purpose, which will permit longitudinal investigations of the pathophysiology of iatrogenic RLN injury and potential therapeutic interventions. C57BL/6J mice were divided into four surgical transection groups (unilateral RLN, n = 10; bilateral RLN, n = 2; unilateral SLN, n = 10; bilateral SLN, n = 10) and a sham surgical group (n = 10). Miniaturized transoral laryngoscopy was used to assess VF mobility over time, and swallowing was assessed using serial videofluoroscopy. Histological assays were conducted 3 months post-surgery for anatomical investigation of the larynx and laryngeal nerves. Eight additional mice underwent unilateral RLN crush injury, half of which received intraoperative vagal nerve stimulation (iVNS). These 8 mice underwent weekly transoral laryngoscopy to investigate VF recovery patterns. Unilateral RLN injury resulted in chronic VF immobility but only acute dysphagia. Bilateral RLN injury caused intraoperative asphyxiation and death. VF mobility was unaffected by SLN transection (unilateral or bilateral), and dysphagia (transient) was evident only after bilateral SLN transection. The sham surgery group retained normal VF mobility and swallow function. Mice that underwent RLN crush injury and iVNS treatment demonstrated accelerated and improved VF recovery. We successfully developed a mouse model of iatrogenic RLN injury with impaired VF mobility and swallowing function that can serve as a clinically relevant platform to develop translational neuroregenerative strategies for RLN injury.

Comparative study of three types of lymphadenectomy along the left recurrent laryngeal nerve by minimally invasive esophagectomy.

BACKGROUND: The objective of this study was to compare three kinds of lymphadenectomy methods along the recurrent laryngeal nerve (RLN) and assess the safety and effectiveness of the new method. METHODS: A total of 194 patients with esophageal cancer who underwent minimally invasive esophagectomy (MIE) at our institution from May 2013 to May 2017 were analyzed retrospectively. According to the method of lymphadenectomy along the left RLN, the patients were divided into three groups: 75 cases underwent the conventional method (A group), 80 cases the skeletonized method (B group) and 39 cases the modified Bascule method (C group). The number of dissected lymph nodes and surgical outcomes were recorded and compared to identify differences among the three groups. RESULTS: The frequency of metastasis to the LRLN lymph node was 18.6% among all patients, and 12%, 20% and 28% in groups A, B and C, respectively. The number of harvested lymph nodes (total/chest/LRLN/LRLN+) in group B and group C were significantly greater than that of group A, but not significant between group B and group C. The hoarseness rate in group C was 15.4%, which was lower than the rate in group B (21.3%) and higher than the rate in group A (13.3%), but there was no statistical significance. CONCLUSIONS: The new method for lymphadenectomy along the left RLN during MIE in the semi-prone position is safe and reliable. It provides sufficient lymph node dissection along the left RLN.

Learning Curve for Using Intraoperative Neural Monitoring Technology of Thyroid Cancer.

We investigated the learning curve for using intraoperative neural monitoring technology in thyroid cancer, with a view to reducing recurrent laryngeal nerve injury complications. Radical or combined radical surgery for thyroid cancer was performed in 82 patients with thyroid cancer and 147 recurrent laryngeal nerves were dissected. Intraoperative neural monitoring technology was applied and the "four-step method" used to monitor recurrent laryngeal nerve function. When the intraoperative signal was attenuated by more than 50%, recurrent laryngeal nerve injury was diagnosed, and the point and causes of injury were determined. The time required to identify the recurrent laryngeal nerve was 0.5-2 min and the injury rate was 2.7%; injuries were diagnosed intraoperatively. Injury most commonly occurred at or close to the point of entry of the nerve into the larynx and was caused by stretching, tumor adhesion, heat, and clamping. The groups are divided in chronological order; a learning curve for using intraoperative neural monitoring technology in thyroid cancer surgery was generated based on the time to identify the recurrent laryngeal nerve and the number of cases with nerve injury. The time to identify the recurrent laryngeal nerve and the number of injury cases decreased markedly with increasing patient numbers. There is a clear learning curve in applying intraoperative neural monitoring technology to thyroid cancer surgery; appropriate use of such technology aids in the protection of the recurrent laryngeal nerve.

A retrospective cohort study of racing performance in Quarter Horses undergoing prosthetic laryngoplasty for treatment of recurrent laryngeal neuropathy.

OBJECTIVE To determine effects of prosthetic laryngoplasty on return to racing, performance index, and career longevity in racing Quarter Horses with recurrent laryngeal neuropathy (RLN) and to evaluate performance variables for horses with RLN undergoing prosthetic laryngoplasty, compared with a control horse population. DESIGN Multicenter, retrospective cohort study. ANIMALS 162 racing Quarter Horses with RLN treated with prosthetic laryngoplasty (case horses) and 324 racing Quarter Horse without RLN (control horses). PROCEDURES Medical and race records of case and control horses examined at 5 referral centers between January 2000 and December 2015 were reviewed retrospectively. Two control horses were matched with each case horse. Return to racing, earnings, number of racing starts, performance index, and career longevity were evaluated. RESULTS The odds of returning to racing did not differ significantly between case and control horses but decreased with increasing age. Neither racing starts nor career longevity were affected by prosthetic laryngoplasty or by RLN grade. In fact, horses undergoing laryngoplasty for treatment of RLN and horses with the lowest RLN grade before surgery had higher performance indices after the surgery, compared with indices for control horses. CONCLUSIONS AND CLINICAL RELEVANCE The faster speeds and shorter distances raced with Quarter Horses could alter how RLN impacts respiratory variables and performance in Quarter Horses, compared with other racehorse breeds. Further study is needed to understand the impacts of RLN and surgical treatments for RLN in racing Quarter Horses.

Recurrent Laryngeal Nerve Reinnervation in Rats Posttransection: Neurotrophic Factor Expression over Time.

OBJECTIVE: Recurrent laryngeal nerve (RLN) injury causes vocal fold paralysis from which functional recovery is typically absent due to nonselective reinnervation. This study investigates expression of axon guidance cues and their modulators relative to the chronology of reinnervation by examining the expression of glial-derived neurotrophic factor (GDNF), netrin 1, and laminin 111 (LAMA1) in nonpooled laryngeal muscles. This study is the first to describe the post-RLN injury expression pattern of LAMA1, a target of particular interest as it has been shown to switch netrin 1-mediated growth cone attraction to repulsion. STUDY DESIGN: Animal experiment (rat model). SETTING: Basic science laboratory. METHODS: The right RLNs of 64 female Sprague-Dawley rats were transected, with sacrifice at 1, 3, 7, 21, 28, and 56 days postinjury (DPI). Single-animal messenger RNA was isolated from the ipsilateral posterior cricoarytenoid (PCA), lateral thyroarytenoid (LTA), and medial thyroarytenoid (MTA) for quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis. Immunostaining for LAMA1 expression was performed in the same muscles. RESULTS: LAMA1 was elevated in the PCA at 3 to 56 DPI, LTA at 7 DPI, and MTA at 14 and 28 DPI. This correlates with the chronology of laryngeal reinnervation. Using a new protocol, single-animal muscle qRT-PCR possible and expression results for GDNF and netrin 1 were similar to previous pooled investigations. CONCLUSION: Reliable qRT-PCR is possible with single rat laryngeal muscles. The expression of netrin 1 and LAMA1 is chronologically coordinated with muscle innervation in the LTA and MTA. This suggests that LAMA1 may influence netrin 1 to repel axons and delay LTA and MTA reinnervation.