Changes in vocal fold gene expression and histology after injection augmentation in a recurrent laryngeal nerve injury model

OBJECTIVE

To investigate changes in neuroregenerative pathways with vocal fold denervation in response to vocal fold augmentation.

METHODS

Eighteen Yorkshire crossbreed swine underwent left recurrent laryngeal nerve transection, followed by observation or augmentation with carboxymethylcellulose or calcium hydroxyapatite at two weeks. Polymerase chain reaction expression of genes regulating muscle growth (MyoD1, MyoG and FoxO1) and atrophy (FBXO32) were analysed at 4 and 12 weeks post-injection. Thyroarytenoid neuromuscular junction density was quantified using immunohistochemistry.

RESULTS

Denervated vocal folds demonstrated reduced expression of MyoD1, MyoG, FoxO1 and FBXO32, but overexpression after augmentation. Healthy vocal folds showed increased early and late MyoD1, MyoG, FoxO1 and FBXO32 expression in all animals. Neuromuscular junction density had a slower decline in augmented compared to untreated denervated vocal folds, and was significantly reduced in healthy vocal folds contralateral to augmentation.

CONCLUSION

Injection augmentation may slow neuromuscular degeneration pathways in denervated vocal folds and reduce compensatory remodelling in contralateral healthy vocal folds.

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.

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.

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.

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.

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 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 for management of aspiration in a subset of children

Pediatric aspiration is a multifactorial process that is often complex to manage. Recurrent laryngeal nerve (RLN) injury can cause glottic insufficiency and aspiration. We describe three cases of unilateral vocal fold paralysis resulting in aspiration and the successful use of the RLN reinnervation for its treatment. The theory for utilizing the reinnervation procedure is that when glottic closure improves and a less breathy vocalization occurs, then the larynx is better equipped to protect the lower airway and avoid aspiration. Our cases demonstrate stronger voice and improved swallow function, with normalization of modified barium swallow evaluation, at approximately 6-months post reinnervation.

Ansa to recurrent laryngeal neurorrhaphy in the setting of laryngeal nerve sacrifice: a cadaveric study to evaluate a reconstructive option

OBJECTIVE

In certain cases, the recurrent laryngeal nerve (RLN) has to be sacrificed. This often results in an inadequate length of residual RLN to be used in a reinnervation procedure. We investigated the length of the distal stump of the RLN from the inferior border of the inferior pharyngeal constrictor muscle (IPCM), where it is frequently compromised, to its entrance into the larynx. Our objective was to determine whether this residual nerve stock was sufficient for margin clearance and neurorrhaphy.

STUDY DESIGN

Cadaveric study

METHODS

Recurrent laryngeal nerves were identified in fresh frozen cadavers. The IPCM was divided, revealing the distal stump of the RLN, which was measured.

RESULTS

Dissection was performed in 20 cadavers (40 nerves). The average length of the right RLN and the left RLN from the IPCM until it entered the larynx was 15mm and 14mm, respectively. All residual RLN remnants were of sufficient length for neurorrhaphy.

CONCLUSION

Concomitant RLN reinnervation procedures in the setting of nerve sacrifice are not well described. A barrier to reinnervation in this setting may be insufficient residual nerve length for a neurorrhaphy. Often, when the RLN is sacrificed intraoperatively either iatrogenically or due to tumor invasion, it is close to the cricoarytenoid joint, at the inferior border of the IPCM. This study demonstrates that by splitting the IPCM, sufficient length can be obtained for neurorrhaphy.

The free neural grafting for recurrent nerve laceration Experimental study in rabbit

AIM

The most dreaded complication of thyroidectomy is recurrent laryngeal nerve damage, which is most of the time hardly irreversible. In our experimental study we researched the use of free nerve grafts in the treatment of laryngeal nerve damage in rabbit.

MATERIAL AND METHODS

There were three groups in our study. In the first group, the recurrent laryngeal nerve was severed and then a free nerve graft was interposed between the phrenic nerve and distal end of recurrent laryngeal nerve. In the second group, a defect in the continuity of the laryngeal nerve was created. The two ends of the nerve were joined together later by an interposed free nerve graft. In the third group, only a defect in the recurrent nerve was created without any attempt at uniting the ends together so that these latter subjects could be assigned as control group. In the evaluation process we performed laryngeal endoscopy, laryngeal EMG and histopathologic examination.

RESULTS

On the 21. day of trial, in the first and second group vocal cord movements were detected on the laryngoscopy along with regeneration waves on EMG. In the third group there was no vocal cord movements on the side where a neural damage was created intentionally. On EMG there was degeneration waves as opposed to regeneration waves seen in the first and second groups. Histopathologic findings were similar.

CONCLUSIONS

Recurrrent laryngeal nerve paralysis is an unwanted complication because it causes permenant sequela. Studies which intend to find a cure for this complication are increasing in number. We aim to find new approaches to cure patients suffering from this devastating complication as well. In our exprerimental study, vocal cord movements were reproduced without causing diaphragmatic paralysis. We believe the results of our study promise to relieve the suffering of patients. The results are encouraging.

KEY WORDS

Muscle, Rat model, Reinnervation, Surgery.

Long-term efficacy of primary intraoperative recurrent laryngeal nerve reinnervation in the management of thyroidectomy-related unilateral vocal fold paralysis

CONCLUSION

Primary intraoperative recurrent laryngeal nerve (RLN) reinnervation techniques demonstrated significant voice improvement at 24 months postoperatively and could be an effective alternative treatment for thyroidectomy-related permanent unilateral vocal fold paralysis (VFP).

OBJECTIVES

To assess the long-term efficacy of intraoperative RLN reinnervation techniques in the management of thyroidectomy-related unilateral VFP.

METHODS

A prospective study was conducted from January 2008 to June 2012 at Soonchunhyang University Bucheon Hospital. Nineteen patients who underwent RLN reinnervation with either direct reinnervation (neurorrhaphy) or ansa cervicalis to RLN (ansa-RLN) anastomosis and completed subjective and objective voice measurement over a 1-year follow-up period were included in this study.

RESULTS

The causes of VFP were cancer involving the RLN (68.4%, 13/19) and iatrogenic nerve transection (31.5%, 6/19). Reinnervation techniques were direct neurorrhaphy (63.2%, 12/19) and ansa-RLN anastomosis (36.8%, 7/19). Subjective parameters such as the Voice Handicap Index (VHI), posterior glottic closure, and mucosal wave demonstrated significant improvement 6 months postoperatively, and the majority of parameters remained stable up to 24 months (p < 0.05). Objective parameters, such as maximum phonation time (MPT), jitter, shimmer, and the harmonics-to-noise ration (HNR), demonstrated significant improvement at 12 months and most remained stable at 24 months (p < 0.05).

[Nerve exploration and decompression for traumatic recurrent laryngeal nerve injuries induced by thyroid gland surgery]

OBJECTIVE

To show the findings of recurrent laryngeal nerve injury exploration and find out therapeutic effects, indications and timing of nerve decompression for traumatic recurrent laryngeal nerve injury induced by thyroid gland surgery.

METHODS

In this study there were 87 patients with recurrent laryngeal nerve injury, including 65 for nerve exploration and 22 for nonsurgical treatment. During nerve exploration, the types, severity of laryngeal nerve injuries and laryngeal muscular mass were studied. Nerve decompression was performed in these 14 patients whose compressing sutures or compression due to cicatricial hypertrophy were received nerve decompression.

RESULTS

Injuries caused by thyroid gland operations mostly are of suture ligation (43%) and nerve severance (48%); simple scar compression was found only in 6 cases (9%). Atrophy of the laryngeal muscles was not very serious in patients with a course less than 6 months. In 10 patients with a course less than three months, nerve decompression restored normal functional abductor and abductor motion of the vocal cord in 9 patients and had no effects in one. Although functional motion of vocal cord was not seen in one case with a course less than 3 months and 4 cases between 3 and 5 months, the mass and tension of the reinnervated vocal cord became much the same as the contralateral normal vocal cord, thus resuming symmetric vibration of the vocal cords and physiological phonation. Although nonsurgical treatment improved severe hoarseness, it didn't restore normal functional motion of the vocal cord and normal voice.

CONCLUSIONS

Nerve exploration showed a primary rule for recurrent laryngeal nerve injury induced by thyroid gland surgery. Early and mid-stage recurrent laryngeal nerve exploration and decompression may restore normal motion of the glottis, and it suggested laryngeal delayed reinnervation may help patients with a course more than 6 months.