Selective reinnervation of the abductor and adductor muscles of the canine larynx after recurrent nerve paralysis

Management Options for Bilateral Vocal Fold Impairment: Scoping Review to Assess the Potential of Soft Robotics Solutions

OBJECTIVES

This scoping review aims to comprehensively assess current surgical interventions for bilateral vocal fold paralysis (BVFP), addressing the heterogeneity in treatment outcomes. Additionally, it explores the potential role of soft robotics as an innovative approach to improve outcomes in BVFP management.

METHODS

This scoping review systematically examines literature from MEDLINE, Embase, and Scopus databases. Inclusion criteria encompass studies related to BVFP management with measurable subjective or objective outcomes. Studies with populations solely under the age of 18 were excluded. Four reviewers independently screened 2263 studies, resulting in the selection of 125 papers for data extraction. Information included study characteristics, interventions, and outcomes. Data synthesis involved both quantitative and qualitative analyses.

RESULTS

The review identified 145 surgical interventions grouped into seven types: tracheostomy, cordectomy, arytenoidectomy, lateralization, combined procedures and others. Outcome measures fit into the following categories: "objective voice," "subjective voice," "aerodynamics," "dyspnea," "decannulation," "swallow," and "quality of life." Positive outcomes were predominant across all interventions, with arytenoidectomy and cordectomy showing relatively lower rates of successful objective and subjective voice outcomes. This could be the result of prioritizing improved airway status. Soft robotics is hypothesized as a potential solution to the limitation of current interventions sacrificing voice for breathing.

CONCLUSIONS

The main aim of current surgical interventions for BVFP is expanding glottic aperture. Yet achieving optimal outcomes remains elusive due to complex airflow dynamics and potential impacts on phonatory function and swallowing. The current review underscores the need for a more nuanced, personalized approach, considering individual anatomical and physiological variations. Soft robotics emerges as a promising avenue to address this variability. However, challenges such as implantation procedures, long-term care, and patient education require careful consideration. Collaboration between medical professionals, engineers, and robotics specialists is essential for translating these principles into practical solutions.

Long-term stimulation by implanted pacemaker enables non-atrophic treatment of bilateral vocal fold paresis in a human-like animal model

A wide variety of treatments have been developed to improve respiratory function and quality of life in patients with bilateral vocal fold paresis (BVFP). One experimental method is the electrical activation of the posterior cricoarytenoid (PCA) muscle with a laryngeal pacemaker (LP) to open the vocal folds. We used an ovine (sheep) model of unilateral VFP to study the long-term effects of functional electrical stimulation on the PCA muscles. The left recurrent laryngeal nerve was cryo-damaged in all animals and an LP was implanted except for the controls. After a reinnervation phase of six months, animals were pooled into groups that received either no treatment, implantation of an LP only, or implantation of an LP and six months of stimulation with different duty cycles. Automated image analysis of fluorescently stained PCA cross-sections was performed to assess relevant muscle characteristics. We observed a fast-to-slow fibre type shift in response to nerve damage and stimulation, but no complete conversion to a slow-twitch-muscle. Fibre size, proportion of hybrid fibres, and intramuscular collagen content were not substantially altered by the stimulation. These results demonstrate that 30 Hz burst stimulation with duty cycles of 40% and 70% did not induce PCA atrophy or fibrosis. Thus, long-term stimulation with an LP is a promising approach for treating BVFP in humans without compromising muscle conditions.

Laryngeal graft after total laryngectomy in humans: A SWiM analysis

Evaluation of the results of laryngeal transplantation (LT) in humans. Analysis of 3 bibliographic databases with the keywords "larynx, transplantation, autograft". In total, 626 abstracts were read and 25 articles selected. The main objective was to analyze the characteristics of laryngeal transplant patients. The accessory objectives comprised analysis of operative technique, immunosuppressive treatment and results. Four articles were selected for analysis. Two patients were transplanted after total laryngectomy for laryngeal carcinoma and 2 after laryngeal trauma. Three of the 4 patients had true transplantation with arterial, venous and neural microanastomosis. Two patients were decannulated and the tracheostomy tube was maintained in the other 2. Three of the 4 patients had good-quality phonation and could feed without a gastric tube. One patient died of carcinoma progression and 1 patient had to be explanted 14 years after transplantation. The number of LTs reported is too small for scientific determination of the place of this intervention in laryngology. The published results could, at first sight, suggest that the future of LT is uncertain. However, several elements, also suggest that otolaryngologists should continue to take an interest in this technique.

Active and Passive Bioimplants for Vocal Fold Paralysis

Vocal fold paralysis is one of the diseases that particularly affect quality of life. While unilateral paralysis leads to glottis closure insufficiency and hoarseness, bilateral paralysis compromises respiration and limits the exercise tolerance. Bioimplants have been used to treat persistent paralysis for over 100 years. The spectrum ranges from autologous tissue transfer and resorbable or permanent injection materials to composite thyroplasty implants and active electrical implants for neurostimulation of the larynx. If bioimplants are used in accordance with the recommendations, the quality of life of affected patients can be significantly improved today.

Bilateral Selective Laryngeal Reinnervation for Bilateral Vocal Fold Paralysis in Children

Importance

Bilateral vocal fold paralysis (BVFP) in pediatric patients is a challenging entity with multiple causes. Traditional approaches to managing BVFP include tracheostomy, arytenoidectomy, suture lateralization, cordotomy, and posterior cricoid enlargement. These interventions are used to create a stable airway but risk compromising voice quality.

Objectives

To assess the use of bilateral selective laryngeal reinnervation (SLR) surgery to manage BVFP and restore dynamic function to the larynx in pediatric patients.

Design, Setting, and Participants

In this case series performed at 2 tertiary care academic institutions, 8 pediatric patients underwent bilateral SLR to treat BVFP (5 patients with iatrogenic BVFP and 3 with congenital BVFP) from November 2004 to August 2018 with follow-up for at least 1.5 years.

Interventions

Bilateral selective laryngeal reinnervation surgery.

Main Outcomes and Measures

Flexible laryngoscopy findings, subjective and objective measures of voice quality, subjective swallowing function, and decannulation in patients who were previously dependent on a tracheostomy tube.

Results

Participants included 6 boys and 2 girls with a median age of 9.3 (range, 2.2 to 18.0) years at the time of surgery. All 8 patients were decannulated; 6 patients had preoperative tracheostomies and 2 had perioperative tracheostomies. Voice quality, as measured using the GRBAS (grade, roughness, breathiness, asthenia, strain) scale, improved in 6 of 8 patients after reinnervation, and swallowing was not impaired in any patients. In 2 patients, GRBAS scale scores remained the same before and after surgery. Inspiratory vocal fold abduction was observed on both sides in 5 patients and on 1 side in 2 patients, with no active abduction observed in 1 patient. The follow-up period was more than 5 years in 7 of 8 patients and at least 1.5 years in all patients.

Conclusions and Relevance

Bilateral SLR appears to be a promising treatment option for children with BVFP; it is currently the only option, to our knowledge, with the potential to restore abductor and adductor vocal fold movement. In patients with complete paralysis, this procedure may provide a strategy for airway management and restoration of the dynamic function of the larynx. It could be considered as a first-line technique before endolaryngeal or airway framework procedures, which carry a risk of compromising voice quality.

A Review of Treatment of Bilateral Vocal Fold Movement Impairment

Purpose of Review

Bilateral vocal fold immobility is a challenging life-threatening problem involving multiple treatment options and nuanced clinical decision making. We aim to provide relevant background on the etiology, diagnosis, and management of bilateral vocal fold movement impairment (BVFMI).

Recent Findings

Over the last 20 years, the management of bilateral vocal fold immobility has advanced significantly with the addition of multiple endoscopic approaches as well as procedures with the goal of returning dynamic function to the larynx, among them: selective reinnervation. Chemodenervation has also demonstrated promising results as a temporizing procedure in appropriately selected patients with BVFMI.

Summary

Tracheostomy remains the mainstay of emergent treatment for airway obstruction secondary to bilateral vocal fold immobility. However, recent advances in endoscopic approaches allow for avoidance of tracheostomy in many patients. Developments in dynamic procedures with the aim of restoring laryngeal function allow for adequate airway management while maintaining voice quality and limiting aspiration risk.

Comparison of voice therapy and selective electrical stimulation of the larynx in early unilateral vocal fold paralysis after thyroid surgery: A retrospective data analysis

Objectives

The goal of the retrospective study was to investigate the 3‐month‐outcome after treatment of patients with early unilateral vocal fold paralysis (UVFP) with either standard voice therapy (VT) or selective electrical stimulation of the larynx (SES).

Design

Non‐randomised retrospective study.

Setting

1519 patients who underwent thyroid surgery between 2015 and 2018 were analysed according vocal fold mobility; UVFP patients were treated either by VT or SES.

Participants

51 UVFP patients.

Main outcome measures

51 UVFP patients have been advised regarding treatment options like either VT (group 1) or SES (group 2). The patients of group 1 (n = 26) and 2 (n = 25) were re‐assessed up to 3 months post‐operatively regarding UVFP persistence/recovery and perceptive voice sound quality. At follow‐ups, perceptual analysis of voice sound (using roughness=R/breathiness=B/hoarseness=H scale) and endoscopic laryngoscopy have been performed. Position of immobile vocal fold, shape of glottal closure and RBH parameters have been considered for statistical analyses.

Results

Restitution of UVFP with regular respiratory vocal fold mobility of both vocal folds occurred in 53.8% of group 1 (VT), and in 40.0% of group 2 (SES) after 3 months of therapy between both groups. No difference could be seen for RBH, type of glottal closure and position of ailing vocal folds in patients with persisting UVFP within both groups and between the groups.

Conclusions

The study reveals that SES can achieve similar functional outcome in early UVFP. Thus, it should be considered as an equivalent therapy alternative to VT for treatment of early UVFP patients since no significant difference in vocal outcome and glottal configuration between the two groups could be demonstrated.

Olfactory Ecto-Mesenchymal Stem Cells in Laryngeal Nerve Regeneration in Rats

Selective intralaryngeal reinnervation has been shown to be effective in experimental models. This consists of independently reinnerving the adductor and abductor of laryngeal muscles of the larynx, in order to prevent any misalignment of the axonal regrowth, improve the functional recovery and tend toward reduction of synkinesis. The surgical technique remains complex. Current research focuses on simplifying and improving this technique. Olfactory ectomesenchymal stem cells (OEMSC) represent an interesting candidate for cell therapy and could be obtained from olfactory mucosa. Recent reports suggest a neuroregenerative potential in various animal models of central and peripheral nervous systems injuries. The aim of this study was dual: to develop a simple surgical model of selective reinnervation applicable in humans and to evaluate the relevance of OEMSC-based cell therapy for improving axonal guidance. Eight Fisher syngeneic rats were used to carry out the OEMSCs culture. Thirty-four Fisher syngeneic rats were operated on, divided into three groups depending on the transplanting. For all the rats, we have performed a side to end anastomosis of the vagal nerve with the inferior laryngeal nerve by interposition of a nerve graft from the left femoral nerve. Then, the first group didn't have any injection, the second group has an injection of thrombin and the third group has an injection of one million EOMSCs. Three months after surgery, laryngeal muscle activity was evaluated by videolaryngoscopy and electromyography recordings. In order to illustrate the quality of axonal regrowth, a fluorescent tracer was injected into the right posterior crico-arytenoid muscle (PCA) to reveal the cellular bodies of the motoneurons responsible for reinnervation of the PCA in the central nervous system. In our study, no improvement was found during the videolaryngological functional evaluation or with regard to the electrical activity of the PCA muscle. The cells colabelled in retrograde tracing were numerous in all groups, reflecting abnormal axonal regeneration. The interposition of a nerve graft, as side to end anastomosis between the vagus nerve and the inferior laryngeal nerve, filled with OEMSCs, does not provide better reinnervation of a hemilarynx.

Glottic configuration changes and outcomes of endoscopic arytenoid abduction lateropexy

INTRODUCTION

Endoscopic arytenoid abduction lateropexy (EAAL) is an effective glottis enlarging procedure for the treatment of bilateral vocal cord palsy (BVCP). The postoperative glottic configuration changes can be evaluated by modern, high-resolution, 3D image reconstructions. Functional results are described by spirometry as well as objective and subjective phoniatric tests.

METHODS

Unilateral EAAL was performed in ten malignant thyroid gland tumor patients (eight women, two men), who had BVCP after thyroid surgery. Slicer 3D^® software was used for morphometric analysis. Pre- and postoperative peak inspiratory flow (PIF) and standard phoniatric parameters were compared.

RESULTS

The glottic gap improved significantly (+ 60%). Significant improvement of PIF was found in all cases. Phoniatric tests revealed better quality of voice and patient satisfaction. Their voices changed from a severely impaired to a socially acceptable, almost normal, quality.

CONCLUSION

The results support our clinical observations that the ideal position of the lateralization sutures is the one which provides a physiological abduction position of the arytenoid cartilage. Considering these good results, the surgical indications for minimally invasive endoscopic arytenoid lateropexy may be extended.

Dual innervation may occur in a partially denervated muscle

INTRODUCTION

With a view to simplifying surgical techniques for selective laryngeal reinnervation, we addressed the question of whether it is feasible to receive additional innervation by a partially denervated muscle using an infrahyoid muscle model.

METHODS

In 90 rats (6 groups of 15), phrenic nerve transfer was used to reinnervate the sternothyroid muscle. In some cases, residual innervation by the original nerve was present. Three months later we performed electromyographic studies, contraction strength measurements, histologic assessment, and retrograde labeling.

RESULTS

Muscles reinnervated by the phrenic nerve had a greater "dual-response" rate (in terms of nerve latency, contraction strength, and retrograde labeling) than muscles in the control groups.

DISCUSSION

The phrenic nerve can impart its inspiratory properties to an initially denervated strap muscle-even when residual innervation is present. The preservation of contractile potential confirmed the feasibility of dual innervation in a previously injured muscle. Muscle Nerve 59:108-115, 2019.

Role of reinnervation in the management of recurrent laryngeal nerve injury: current state and advances

PURPOSE OF REVIEW

To present the current state of knowledge concerning different laryngeal reinnervation procedures for unilateral and bilateral vocal palsy.

RECENT FINDINGS

Recent reports show positive outcomes on both unilateral and bilateral reinnervations. The phrenic nerve is the most commonly used donor for bilateral vocal palsy, but use of the superior laryngeal nerve has also been suggested.

SUMMARY

Reinnervation of the larynx is a complex undertaking that can be performed by ENT surgeons with skills in microsurgery. Advances in this this field represent a paradigm shift in laryngeal rehabilitation and a prerequisite for laryngeal transplantation. Advances in basic understanding of nerve regeneration and in particular the need to surgically manage competitive reinnervation make the results of laryngeal reinnervation more predictable.

Reinnervation of the diaphragm by the inferior laryngeal nerve to the phrenic nerve in ventilator-dependent tetraplegic patients with C3-5 damage

The aim of this study was to evaluate the feasibility of unilateral diaphragmatic reinnervation in humans by the inferior laryngeal nerve. This pilot study included chronically ventilated tetraplegic patients with destruction of phrenic nerve motoneurons. Five patients were included. They all had a high level of tetraplegia, with phrenic nerve motor neuron destruction. They were highly dependent on ventilation, without any possibility of weaning. They did not have other chronic pathologies, especially laryngeal disease. They all had diaphragmatic explorations to diagnose the destruction of the motoneurons of the phrenic nerves and nasoendoscopy to be sure that they did not have laryngeal or pharyngeal disease. Then, surgical anastomosis of the right phrenic nerve was performed with the inferior laryngeal nerve, by a cervical approach. A laryngeal reinnervation was performed at the same time, using the ansa hypoglossi. One patient was excluded because of a functional phrenic nerve and one patient died 6 months after the surgery of a cardiac arrest. The remaining three patients were evaluated after the anastomosis every 6 months. They did not present any swallowing or vocal alterations. In these three patients, the diaphragmatic explorations showed that there was a recovery of the diaphragmatic electromyogram of the right and left hemidiaphragms after 1 year. Two patients had surgical diaphragmatic explorations for diaphragmatic pacing 18-24 months after the reinnervation with excellent results. At 36 months, none of the patients could restore their automatic ventilation. In conclusion, this study demonstrated that diaphragmatic reinnervation by the inferior laryngeal nerve is effective, without any vocal or swallowing complications.

The evolution of laryngeal reinnervation, the current state of science and thoughts for future treatments

The treatment of unilateral vocal fold palsy (UVFP) or bilateral vocal fold palsy (BVFP) has been the subject of debate and experiment for 150 years. To date, dozens of different surgical methods have been described to reinnervate this most complex of organs, the larynx. As yet, there is no consensus on the most functionally effective method of reinnervation. However, it is a rapidly expanding area of research and remains an area of controversy. Indications for reinnervation for both UVFP and BVFP are still evolving and our understanding of the neuromuscular supply to the larynx continues to expand. What may have been considered unacceptable results from previous studies with one pathology may actually be of benefit in patients with different pathologies. This uncertainty of treatment options and potential outcomes can be confusing. In addition alternative techniques have been postulated as mainstays or adjuncts of treatment to the stalwart of reinnervation, neurorrhaphy. Determining what the correct treatment for an individual patient should be is still a gray area. With this in mind, this article reviews the evolution of laryngeal reinnervation, reviews the current state of the science, and suggests directions in which it might move in the future.

Reinnervation of bilateral posterior cricoarytenoid muscles using the left phrenic nerve in patients with bilateral vocal fold paralysis

Objective

To evaluate the feasibility, effectiveness, and safety of reinnervation of the bilateral posterior cricoarytenoid (PCA) muscles using the left phrenic nerve in patients with bilateral vocal fold paralysis.

Methods

Forty-four patients with bilateral vocal fold paralysis who underwent reinnervation of the bilateral PCA muscles using the left phrenic nerve were enrolled in this study. Videostroboscopy, perceptual evaluation, acoustic analysis, maximum phonation time, pulmonary function testing, and laryngeal electromyography were performed preoperatively and postoperatively. Patients were followed-up for at least 1 year after surgery.

Results

Videostroboscopy showed that within 1 year after reinnervation, abductive movement could be observed in the left vocal folds of 87% of patients and the right vocal folds of 72% of patients. Abductive excursion on the left side was significantly larger than that on the right side (P < 0.05); most of the vocal function parameters were improved postoperatively compared with the preoperative parameters, albeit without a significant difference (P > 0.05). No patients developed immediate dyspnea after surgery, and the pulmonary function parameters recovered to normal reference value levels within 1 year. Postoperative laryngeal electromyography confirmed successful reinnervation of the bilateral PCA muscles. Eighty-seven percent of patients in this series were decannulated and did not show obvious dyspnea after physical activity. Those who were decannulated after subsequent arytenoidectomy were not included in calculating the success rate of decannulation.

Conclusions

Reinnervation of the bilateral PCA muscles using the left phrenic nerve can restore inspiratory vocal fold abduction to a physiologically satisfactory extent while preserving phonatory function at the preoperative level without evident morbidity.

Comparison of ventilation and voice outcomes between unilateral laryngeal pacing and unilateral cordotomy for the treatment of bilateral vocal fold paralysis

BACKGROUND/AIMS

Rehabilitation of the bilaterally paralyzed human larynx remains a complex clinical problem. Conventional treatment generally involves surgical enlargement of the compromised airway, but often with resultant dysphonia and risk of aspiration. In this retrospective study, we compared one such treatment, posterior cordotomy, with unilateral laryngeal pacing: reanimation of vocal fold opening by functional electrical stimulation of the posterior cricoarytenoid muscle.

METHODS

Postoperative peak inspiratory flow (PIF) values and overall voice grade ratings were compared between the two surgical groups, and pre- and postoperative PIF were compared within the pacing group.

RESULTS

There were 5 patients in the unilateral pacing group and 12 patients in the unilateral cordotomy group. Within the pacing group, postoperative PIF values were significantly improved from preoperative PIF values (p = 0.04) without a significant effect on voice (grade; p = 0.62). Within the pacing group, the mean postoperative PIF value was significantly higher than that in the cordotomy group (p = 0.05). Also, the mean postoperative overall voice grade values in the pacing group were significantly lower (better) than those of the cordotomy group (p = 0.03).

CONCLUSION

Unilateral pacing appears to be an effective treatment superior to posterior cordotomy with respect to postoperative ventilation and voice outcome measures.

Laryngotracheal transplantation: technical modifications and functional outcomes

OBJECTIVES/HYPOTHESIS

Laryngeal transplantation offers the potential for patients without a larynx to recover their voice, which is critical in our communication age. We report clinical and functional outcomes from a laryngotracheal transplant. Widespread adoption of this technique has been slowed due to the ethical concerns of life-long immunosuppression after a nonvital organ transplant. Our patient was already on immunosuppressive medication from prior kidney-pancreas transplantation, and therefore was not exposed to added long-term risk. We describe the unique technical advances, clinical course, and rehabilitation of this patient and the implications for future laryngeal transplantation.

STUDY DESIGN

Case report.

METHODS

A laryngotracheal transplantation was performed in a 51-year-old prior kidney-pancreas transplant recipient presenting with complete laryngotracheal stenosis. Surgical modifications were made in the previously described technique related to retrieval, vascular supply, and reinnervation. This resulted in a robustly vascularized organ with well-perfused long-segment tracheal transplant and early return of motor reinnervation.

RESULTS

A multidisciplinary approach resulted in a successful transplant without evidence of rejection to date. Postoperatively, the patient continues to rely on a tracheotomy but has had the return of an oral and nasal airway, vocalization, smell, and taste, all experienced for the first time in 11 years.

CONCLUSIONS

We have demonstrated that our methods may result in a successful laryngotracheal transplant. We describe the preparation, surgical technique, rehabilitation, and interventions employed in achieving optimal outcomes. This report contributes valuable information on this rarely performed composite transplant.

Laryngeal reinnervation surgery - results of a selective approach in an animal study

Laryngeal reinnervation surgery is a difficult subject due to the fact that the recurrent laryngeal nerve (RLN) is responsible for both adductor and abductor laryngeal activity. Non-selective reinnervation procedures will result in laryngeal synkinesis with restoration of tonicity. Restoration of mobility requires selective reinnervation of the adductor and abductor branches with nerves with similar activity patterns as the initial abductor and adductor branches of the RLN.

Tacrolimus enhances the recovery of normal laryngeal muscle fibre distribution after reinnervation

OBJECTIVES

To assess the recovery of various muscle fibre types in the posterior cricoarytenoid muscle after laryngeal reinnervation in the rat, and to determine the influence of tacrolimus on this process.

METHODS

Four groups of rats underwent resection and anastomosis of the left vagus nerve, and were administered either tacrolimus at a low dose or an immunosuppressive dose, or cyclosporin A at a low dose or an immunosuppressive dose. A fifth group received surgery alone, and a sixth group received neither surgery nor drug treatment (healthy group). Muscles were removed for immunohistochemical analysis 45 days after surgery.

RESULTS

There was no difference in the proportion of types 1, 2a and 2b muscle fibres, comparing the immunosuppressive tacrolimus group and the healthy group, whereas there were fewer type 1 fibres in the group receiving surgery alone, compared with the healthy group (7 vs 12.1 per cent, respectively; p = 0.0303).

CONCLUSION

Tacrolimus enhanced the recovery of normal laryngeal muscle fibres after reinnervation in the rat, indicating a possible role in laryngeal transplantation.

Co-transplantation of olfactory ensheathing cells from mucosa and bulb origin enhances functional recovery after peripheral nerve lesion

Olfactory ensheathing cells (OECs) represent an interesting candidate for cell therapy and could be obtained from olfactory mucosa (OM-OECs) or olfactory bulbs (OB-OECs). Recent reports suggest that, depending on their origin, OECs display different functional properties. We show here the complementary and additive effects of co-transplanting OM-OECs and OB-OECs after lesion of a peripheral nerve. For this, a selective motor denervation of the laryngeal muscles was performed by a section/anastomosis of the recurrent laryngeal nerve (RLN). Two months after surgery, recovery of the laryngeal movements and synkinesis phenonema were analyzed by videolaryngoscopy. To complete these assessments, measure of latency and potential duration were determined by electrophysiological recordings and myelinated nerve fiber profiles were defined based on toluidine blue staining. To explain some of the mechanisms involved, tracking of GFP positive OECs was performed. It appears that transplantation of OM-OECs or OB-OECs displayed opposite abilities to improve functional recovery. Indeed, OM-OECs increased recuperation of laryngeal muscles activities without appropriate functional recovery. In contrast, OB-OECs induced some functional recovery by enhancing axonal regrowth. Importantly, co-transplantation of OM-OECs and OB-OECs supported a major functional recovery, with reduction of synkinesis phenomena. This study is the first which clearly demonstrates the complementary and additive properties of OECs obtained from olfactory mucosa and olfactory bulb to improve functional recovery after transplantation in a nerve lesion model.

Arytenoid Abduction: Indications and Limitations

Objectives

I report further experience with arytenoid abduction (AAb), a procedure that enlarges the glottis by external rotation of the arytenoid cartilage and thus moves the vocal process laterally and rostrally, but does not preclude adduction for phonation. Therefore, AAb has the potential to preserve voice in patients with bilateral abductor laryngeal paralysis.

Methods

I performed a retrospective review of AAb in 11 patients with bilateral laryngeal paralysis and 3 patients with other neurologic causes of glottal airway compromise, ie, adductor breathing dystonia, frequent laryngospasm, and progressive laryngeal breathing dysfunction.

Results

Seven of the 11 patients with bilateral paralysis had dramatic airway improvement. One patient required a tracheotomy after AAb, and 3 patients with an existing tracheotomy could not be decannulated. Arytenoid abduction relieved airway obstruction in the patient with recurrent laryngospasm and in the child with progressive laryngeal breathing dysfunction, but the patient with adductor breathing dystonia has persistent stridor. The factors associated with a poor airway outcome included prolonged tracheotomy, electromyographic evidence of inspiratory activity of adductor muscles, chronic obstructive pulmonary disease, sleep apnea, and prior cordotomy or arytenoidectomy.

Conclusions

Arytenoid abduction is most effective in patients with bilateral laryngeal paralysis of less than 1 year's duration who do not have unfavorable laryngeal adductor activity.

Arytenoid Abduction: Indications and Limitations

Objectives

I report further experience with arytenoid abduction (AAb), a procedure that enlarges the glottis by external rotation of the arytenoid cartilage and thus moves the vocal process laterally and rostrally, but does not preclude adduction for phonation. Therefore, AAb has the potential to preserve voice in patients with bilateral abductor laryngeal paralysis.

Methods

I performed a retrospective review of AAb in 11 patients with bilateral laryngeal paralysis and 3 patients with other neurologic causes of glottal airway compromise, ie, adductor breathing dystonia, frequent laryngospasm, and progressive laryngeal breathing dysfunction.

Results

Seven of the 11 patients with bilateral paralysis had dramatic airway improvement. One patient required a tracheotomy after AAb, and 3 patients with an existing tracheotomy could not be decannulated. Arytenoid abduction relieved airway obstruction in the patient with recurrent laryngospasm and in the child with progressive laryngeal breathing dysfunction, but the patient with adductor breathing dystonia has persistent stridor. The factors associated with a poor airway outcome included prolonged tracheotomy, electromyographic evidence of inspiratory activity of adductor muscles, chronic obstructive pulmonary disease, sleep apnea, and prior cordotomy or arytenoidectomy.

Conclusions

Arytenoid abduction is most effective in patients with bilateral laryngeal paralysis of less than 1 year's duration who do not have unfavorable laryngeal adductor activity.

Neurotrophin expression of laryngeal muscles in response to recurrent laryngeal nerve transection

OBJECTIVE/HYPOTHESIS

The recurrent laryngeal nerve (RLN) commonly regenerates after injury; however, functional motion is rarely recovered. Animal experiments have documented aberrant reinnervation after nerve transection, with motor axons reaching inappropriate muscles. More recently, experimental results suggest that lack of vocal fold motion after RLN injury is due to preferential reinnervation of adductor muscles, with inadequate reinnervation of the posterior cricoarytenoid muscle (PCA), the only abductor muscle of the larynx. Information on factors that could influence the receptiveness of these muscles to reinnervation could be useful in developing new therapeutic strategies. It is hypothesized that the thyroarytenoid muscle (TA) and the PCA differ in expression of neurotrophins in response to denervation.

STUDY DESIGN

Laboratory experiment.

METHODS

Rats were sacrificed at 3 days, 6 weeks, or 4 months after unilateral RLN injury measure expression of brain-derived nerve growth factor (BDNF), nerve growth factor (NGF), and neurotrophin 4 (NT-4) in the TA and PCA muscles, using immunohistochemistry. We also assessed nerve regeneration.

RESULTS

NGF was significantly diminished in the denervated TA muscle at 3 days after injury and increased at 6 weeks. BDNF expression was unchanged in the TA, but was diminished in both PCA muscles at 3 days and 6 weeks, returning to near-normal levels at 4 months after injury. Robust nerve regeneration of distal RLN was present at 4 months.

CONCLUSIONS

Results suggest that the TA and PCA muscles respond differently to denervation.

Defining phonosurgery: a proposal for classification and nomenclature by the Phonosurgery Committee of the European Laryngological Society (ELS)

The term phonosurgery (PS) refers to any operation designed primarily for the improvement or restoration of voice. It is defined by the intended operative goal, which pertains to quality of life rather than its preservation, and informed consent needs to account for this emphasis. Since the aim is improvement or maintenance of vocal function, it is essential to document voice accurately pre-operatively. As important as the surgery itself is a team approach to perioperative care and rehabilitation. Although not a new concept, the PS portfolio of operations continues to grow rapidly, making this one of the most dynamic field in Laryngology. However, this has also led to confusion regarding terminology and classification, with the result that it is presently difficult to compare results between institutions. The aim of this paper is to establish a practical classification system for PS and to thereby establish a common language for reporting results. We propose four groups of operation: vocal fold surgery (VFS), laryngeal framework surgery (LFS), neuromuscular surgery (NHS) and reconstructive surgery (RCS) (for either partial or total laryngeal replacement).

Laryngeal Sensation Recovery by Reinnervation in Rabbits

OBJECTIVES/HYPOTHESIS

To assess the possibilities of restoring laryngeal sensation in an animal model by way of the internal branch of the superior laryngeal nerve (ibSLN) bilateral section and anastomosis to itself or to transposition nerves (i.e., lingual, glossopharyngeal, and great auricular nerves).

STUDY DESIGN

Prospective study using New Zealand rabbits.

METHODS

Six groups of rabbits were operated on and evaluated: healthy controls (n = 6); section without reinnervation (denervated group, n = 7); section and reinnervation with ibSLN (SLN-SLN group, n = 9); and section and anastomosis with the lingual nerve (lingual group, n = 7), the glossopharyngeal nerve (glossopharyngeal group, n = 6), and the great auricular nerve (GA group, n = 7). After 9 months, recovery of a laryngeal closure reflex was assessed by stimulation of the epiglottis and nerve anastomosis.

RESULTS

Laryngeal sensation was restored in 14.3% in the denervated group, 66.6% in the SLN-SLN group, 71.4% in the lingual group, 100% in the GA group (P < .001), 50% in glossopharyngeal group. Some anastomoses were severed. When anastomosis was intact, a laryngeal closure reflex was observed in 91.7% of the rabbits of the SLN-SLN group (P < .001), 80% in the lingual group (P < .001), 100% in the GA group (P < .05) and 100% of the glossopharyngeal group.

CONCLUSIONS

Rehabilitation of supraglottic laryngeal sensation is feasible by way of anastomosis of the ibSLN to itself, but also to the lingual, glossopharyngeal, and great auricular nerves. These results suggest that this type of procedure may be useful in humans to prevent aspiration and subsequent pneumonia as related to lesions of the laryngeal reflex pathway. It could also be considered one stage toward the functional rehabilitation of a transplanted larynx.

Effect of neurotrophin-3 on reinnervation of the larynx using the phrenic nerve transfer technique

Current techniques for reinnervation of the larynx following recurrent laryngeal nerve (RLN) injury are limited by synkinesis, which prevents functional recovery. Treatment with neurotrophins (NT) may enhance nerve regeneration and encourage more accurate reinnervation. This study presents the results of using the phrenic nerve transfer method, combined with NT-3 treatment, to selectively reinnervate the posterior cricoarytenoid (PCA) abductor muscle in a pig nerve injury model. RLN transection altered the phenotype and morphology of laryngeal muscles. In both the PCA and thyroarytenoid (TA) adductor muscle, fast type myosin heavy chain (MyHC) protein was decreased while slow type MyHC was increased. These changes were accompanied with a significant reduction in muscle fibre diameter. Following nerve repair there was a progressive normalization of MyHC phenotype and increased muscle fibre diameter in the PCA but not the TA muscle. This correlated with enhanced abductor function indicating the phrenic nerve accurately reinnervated the PCA muscle. Treatment with NT-3 significantly enhanced phrenic nerve regeneration but led to only a small increase in the number of reinnervated PCA muscle fibres and minimal effect on abductor muscle phenotype and morphology. Therefore, work exploring other growth factors, either alone or in combination with NT-3, is required.

Diaphragmatic effects of selective resection of the upper phrenic nerve root in dogs

The aim of this study was to evaluate the effects on the diaphragm of upper phrenic nerve root resections in dogs. During laryngeal reinnervation, selective resections of the upper phrenic nerve root (C5) were performed unilaterally (right side, n=7; Group A) and bilaterally (n=6; Group B) and compared to non denervated animals (n=5). After 8 months, a diaphragmatic evaluation was performed: X-ray, EMG, transdiaphragmatic pressure (Pdi) after ipsi- and bilateral tetanic stimulation of the phrenic nerves and a bilateral histological study of five hemidiaphragmatic regions. EMG alterations were significantly more severe in Group B than in Group A, for the left (p<0.05) and right hemidiaphragms (p<0.01). No differences in the X-rays were noted between the three groups. The Pdi of the three groups after occlusion and phrenic nerve stimulations (unilateral and bilateral) were not statistically different. Histological data demonstrated that there were no differences in fibre irregularity, predominant fibre type or fibrosis between the three groups. Macroscopic and microscopic atrophy, which was mainly present on the anterior regions of the hemidiaphragms, was significantly higher in Group B than in Group A and undenervated dogs (p<0.05). In conclusion, resection of the upper phrenic nerve root of one phrenic nerve (right side) have limited effect on the diaphragm in dogs. However, resection of the upper phrenic nerve root on both sides resulted in a significant effect on the EMGs and histology of the entire diaphragm without any significant consequences on transdiaphragmatic pressure.

Reinnervation of laryngeal muscles: a study of changes in myosin heavy chain expression

Direct repair of the recurrent laryngeal nerve (RLN) results in synkinesis and compromised laryngeal function. We have therefore developed a pig model to investigate whether anastomosis of the phrenic nerve with the abductor branch of the RLN leads to specific reinnervation of abductor muscles. Expression of myosin heavy chain protein (MyHC), a marker of appropriate reinnervation, was determined in the posterior cricoarytenoid (PCA) abductor and thyroarytenoid (TA) adductor muscles following nerve injury and repair. The denervated PCA muscle exhibited decreased levels of the fast-type MyHC isoforms IIA and IIB, and increased slow-type MyHC expression. Similarly, there was a fall in type IIB levels in the denervated TA muscle but increases in both IIA and slow MyHC. Four months after repair, the MyHC expression in the PCA was near normal, suggesting that our model reduces the risk of synkinesis and ensures the accurate muscle reinnervation required for full functional recovery.

Laryngeal transplantation in 2005: a review

There is no good surgical, medical or prosthetic solution to the problems faced by those with a larynx whose function is irreversibly damaged by tumor or trauma. Over the past 10 years, the pace of research designed to establish laryngeal transplantation as a therapeutic option for these persons has increased steadily. The biggest milestone in this field was the world's first true laryngeal transplant performed in Cleveland, Ohio in 1998. The recipient's graft continues to function well, in many respects, even after 7 years. However, it has also highlighted the remaining barriers to full-scale clinical trials. Stimulated by these observations, several groups have accumulated data which point to answers to some of the outstanding questions surrounding functional reinnervation and immunomodulation. This review seeks to outline the progress achieved in this field by 2005 and to point the way forward for laryngeal transplantation research in the 21st century.

Laryngeal abductor muscle reinnervation in a pig model

OBJECTIVE

To develop a large animal model for studies of laryngeal abductor reinnervation.

MATERIAL AND METHODS

Six minipigs underwent unilateral anastomosis of the phrenic nerve-abductor branch of the recurrent laryngeal nerve (RLN). Polyhydroxybutyrate (PHB) conduits were used for repair. At each of 30, 60 and 120 days, 2 animals underwent video laryngeal endoscopy (VLE) and were then killed. VLE was also performed in the 120-day pair at 60 days. Nerve-conduit-nerve-muscle samples were fixed for light and immunofluorescence (pan-neurofilaments, S-100) microscopy. Laryngeal muscles were harvested (myosin heavy chain analysis).

RESULTS

VLE showed recovery of abductor function in 1 animal at 60 days and in 1 at 120 days. Haematoxylin-eosin staining demonstrated a complex inflammatory response. Eosinophil recruitment was observed. Stepwise regeneration and reorganization of the distal nerve between 30 and 120 days was observed with pan-NF staining. The mean minimum diameter in the reinnervated posterior crico-arytenoids tended to increase for up to 120 days.

CONCLUSIONS

Anastomosis of the phrenic nerve-abductor branch of the RLN with a PHB conduit in a pig can result in functional and histological recovery within 2-4 months and appears to at least sustain abductor muscle fibre morphology. Recovery occurs despite a complex inflammatory response, which may be an essential part of healing rather than inhibitory.

Intrinsic muscles and distribution of the recurrent laryngeal nerve in the pig larynx

To use the pig larynx in studies of laryngeal reinnervation, it is essential to have a clear understanding of its anatomy. We aimed to define the macroscopic anatomy of the intrinsic muscles and the course of the recurrent laryngeal nerve (RLN) in the pig larynx. Twelve large white pig larynges were used. Five larynges were preserved in formalin, then dissected to study the anatomy of the intrinsic muscles. Seven larynges were stained using the modified Sihler's staining technique, which results in nerves being stained dark purple while the remainder of the larynx is rendered translucent. The intrinsic muscles of the pig larynx were similar to those in the human. The RLN gives off a branch that enters the posterior cricoarytenoid muscle (PCA) on its deep surface and supplies the entire muscle, although the branching pattern of the nerve within the muscle varies considerably. These results facilitate detailed reinnervation studies in the pig laryngeal transplant model.

Laryngeal reinnervation

Laryngeal reinnervation refers to any of a number of surgical procedures intended to restore neural connections to the larynx, which have usually been lost from some type of trauma (eg, surgical). The nerve function(s) to be restored may be those of the recurrent laryngeal nerve or its subdivisions, those of the superior laryngeal nerve, or both, and they may be motor or sensory. Several different donor nerves are available and have been described. The technique used may be direct end-to-end anastomosis (neurorrhaphy), direct implantation of a nerve ending into a muscle, the nerve-muscle pedicle technique, or muscle-nerve-muscle methods. These nerves and techniques may be combined in many ways. A number of new techniques have been reported in animal studies; however, the animal studies do not always predict the results of analogous surgeries in human patients. The historical and current perspectives on these techniques are discussed in this article.

Experimental reinnervation of a strap muscle with a few roots of the phrenic nerve in rabbits

In order to compare application of the roots of the phrenic nerve to the ansa hypoglossi for laryngeal muscle neurotization, 1 or more roots from the phrenic nerve were implanted into the right sternothyroid (RST) muscle of rabbits (n = 36). Controls were intact animals (in which RST innervation is provided by the ansa; n = 6) and denervated ones (n = 6). At 66 +/- 2 days (mean +/- SE) after neurotization, during quiet breathing, inspiratory electromyographic activity and isometric contraction force were observed in all reinnervated RST muscles (n = 24). During maximal inspiratory effort, electromyographic activity and force increased. In animals reinnervated by the C4 root alone, forces (46.22 +/- 7.8 g) were significantly higher than in intact animals (10.83 +/- 5.0 g). Retrograde labeling proved the phrenic origin of the neurotization. Electromyography of the diaphragm was recorded. We conclude that in rabbits, neurotization of a strap muscle by 1 or 2 roots of the phrenic nerve allows inspiratory contraction, even during quiet breathing. Such inspiratory activity is not observed in sternothyroid muscles of intact animals innervated by the ansa hypoglossi.

Cervical anatomy of phrenic nerve roots in the rabbit. European Group for Research on the Larynx

The cervical anatomy of the different nerve contributions that constitute the phrenic nerve (phrenic nerve roots and accessory phrenic nerve) were studied in rabbits. In 55 dissections, 6 main root arrangement types were observed. The roots that issued from the fourth and fifth cervical nerves (C4 and C5 roots) were constant. The C4 root was either short or long. The C6 root was at times absent, or sometimes double. An accessory phrenic nerve was present in 43% of the right and 28% of the left dissections. The distribution of the phrenic nerve roots often displayed left-right asymmetry. We conclude that a better knowledge of the cervical anatomy of the phrenic nerve is useful both in physiological studies involving diaphragm denervation and in experimental laryngeal reinnervation.

Ansa cervicalis nerve: review of the topographic anatomy and morphology

In recent years, there has been a proliferation of techniques utilizing the ansa cervicalis nerve to reinnervate the paralyzed larynx. The anatomic course and morphology of the ansa cervicalis are complicated by the variable course and location along the great vessels of the neck, as well as the significant differences observed in the arrangement of its contributing roots and regional branching patterns. Herein, we review the surgical anatomic course of ansa cervicalis and its innervation of the muscles of the neck, and develop specific recommendations with respect to the use of this nerve in laryngeal reinnervation.

Physiologic Motion after Laryngeal Nerve Reinnervation: A New Method

In this study a new method of reinnervation for unilateral recurrent laryngeal nerve paralysis was performed in canines, producing physiologic vocal fold motion in each of a small series of animals. During the procedure the left anterior division of the recurrent laryngeal nerve was reinnervated with axons from the thyroarytenoid branch of the contralateral recurrent laryngeal nerve. The posterior branch of the left recurrent laryngeal nerve was divided and sutured to the ansa cervicalis to maintain tone in the posterior cricoarytenoid muscle. In all four animals, the right distal vocalis stump was reinnervated with an ansa cervicalis nerve branch. After 3 months physiologic vocal fold motion and electromyographic activity could be demonstrated during mechanical stimulation of the supraglottis (adduction) and during tracheostomy obstruction (abduction). Acoustic data revealed improvement of jitter, shimmer, signal-to-noise ratio, and vocal efficiency in reinnervated animals compared with paralyzed canines before treatment, although the results lacked statistical significance. This approach to the rehabilitation of unilateral vocal fold paralysis is discussed. (Otolaryngol Head Neck Surg 1997;116:466–74.)

Experimental study on reinnervation of vocal cord adductors with the ansa cervicalis

The purpose of this study was to reestablish the adduction of the paralyzed vocal cord through reinnervation of the adductor muscles for unilateral vocal cord paralysis. In nine dogs, the adductor branch of the recurrent laryngeal nerve was anastomosed to the main branch of the ansa cervicalis. Six months later, various techniques of observation showed that seven of nine cases had excellent to good adduction during whining. Adduction was caused by reinnervation of the adductor muscles from the ansa cervicalis as demonstrated by laryngeal spontaneous and evoked electromyography, contraction tension, and various histologic findings. Therefore, the new technique could be a good treatment of unilateral vocal cord paralysis.

Recurrent nerve/ansa cervicalis nerve anastomosis: a treatment alternative in unilateral recurrent nerve paralysis

Sectioning of the right recurrent nerve was done in 5 mongrel dogs under general anaesthesia. The distal stump was anastomosed with the ansa cervicalis nerve branch to the sternothyroid muscle. Three to 5 months later the vocal cord movements during light and very light anaesthesia were videorecorded. Under light anaesthesia contraction and medial bulging of the reinnervated right vocal cord occurred in 4 of the dogs. Under very light anaesthesia there was also some adduction of the right vocal cord in these 4 dogs. The right recurrent nerve was then sectioned proximally to the anastomosis and stimulated electrically. In all 5 dogs we observed that electrical stimulation produced a strong adduction of the right vocal cord. Histochemistry of the right vocal and posterior cricoarytenoid muscles showed that reinnervation had taken place. The study indicates that in cases of unilateral vocal cord paralysis an anastomosis between the ansa cervalalis and the recurrent nerve will result in improved phonatory function of the affected vocal cord.

A functional evaluation of ansa cervicalis nerve transfer for unilateral vocal cord paralysis: future directions for laryngeal reinnervation

There are a variety of methods for treating unilateral vocal cord paralysis, but to date there are few objective studies that evaluate the functional results of nerve transfer from the ansa cervicalis. Six dogs underwent unilateral recurrent laryngeal nerve section with immediate reanastamosis to the sternothyroid branch of the ansa cervicalis. After 5 to 6 months, measurements of vocal efficiency and acoustic parameters, videolaryngoscopy, videostroboscopy, and evoked electromyography were performed. Identical measurements were made in eight control dogs during normal electrically induced phonation and a simulated unilateral recurrent laryngeal nerve paralysis. Histologic analysis of both vocalis muscles, recurrent laryngeal nerves, ansa cervicalis, and the ansa-recurrent laryngeal nerve anastamosis site was performed. Evidence of reinnervation was found in all of the animals that underwent nerve transfer. The vocal efficiency and acoustic quality after ansa cervicalis nerve transfer were dependent on the degree of electrical stimulation from the transferred nerve to the reinnervated cord during phonation. In the absence of electrical stimulation to the nerve transfer, physiologic vocal cord motion could not be elicited from the reinnervated cord.