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

Management of Pediatric Bilateral Vocal Fold Paralysis: A State-of-the-Art Review of Etiologies, Diagnosis, and Treatments

OBJECTIVE

This paper reviews the current literature about epidemiology, etiologies, diagnosis, and management of pediatric bilateral vocal fold paralysis (PBVFP).

METHODS

According to PRISMA statements, a narrative review of the current literature was conducted through the PubMed, Scopus, and Cochrane Library databases about the epidemiology, etiologies, diagnosis, and management of PBVFP.

RESULTS

PBVCP is the second most common congenital laryngeal anomaly in the pediatric population, accounting for 10% to 20% of pediatric laryngeal conditions. PBVCP is related to idiopathic (42.2%), congenital (19.7%), and neurological (16.9%) conditions. A tracheotomy is required in 60% of cases regarding stridor and dyspnea, which are the most prevalent symptoms. The diagnosis is based on the etiological features, clinical presentation, laryngoscopic findings, and objective examinations. Laryngeal electromyography may be used to support the diagnosis in difficult cases, but its reliability depends on the practitioner's experience. The primary differential diagnosis is posterior glottis stenosis, which needs to be excluded regarding therapeutic and management differences with PBVCP. Transient surgical procedures consist of tracheotomy or laterofixation of the vocal fold. Current permanent procedures include uni- or bilateral partial arytenoidectomy, posterior transverse cordotomy, cricoid splits, and laryngeal selective reinnervation. There is no evidence of the superiority of some procedures over others.

CONCLUSIONS

PBVCP is the second most common laryngeal disorder in the pediatric population. Diagnosis is based on etiological and clinical findings and may require the use of laryngeal electromyography. Therapeutic management may involve several transient or permanent surgical procedures that are associated with overall subjective improvements in symptoms, laryngeal findings, and low complication rates.

Management of Bilateral Vocal Fold Paralysis: A Systematic Review

OBJECTIVE

To review the current literature about epidemiology, etiologies and surgical management of bilateral vocal fold paralysis (BVFP).

DATA SOURCES

PubMED, Scopus, and Cochrane Library.

REVIEW METHODS

A systematic review of the literature on epidemiology, etiologies, and management of adult patients with BVFP was conducted through preferred reporting items for systematic reviews and meta-analyses statements by 2 investigators.

RESULTS

Of the 360 identified papers, 245 were screened, and of these 55 were considered for review. The majority (76.6%) of BVFP cases are iatrogenic. BVFP requires immediate tracheotomy in 36.2% of cases. Laterofixation of the vocal fold was described in 9 studies and is a cost-effective alternative procedure to tracheotomy while awaiting potential recovery. Unilateral and bilateral posterior transverse cordotomy outcomes were reported in 9 and 7 studies, respectively. Both approaches are associated with a 95.1% decannulation rate, adequate airway volume, but voice quality worsening. Unilateral/bilateral partial arytenoidectomy data were described in 4 studies, which reported lower decannulation rate (83%) and better voice quality outcome than cordotomy. Revision rates and complications vary across studies, with complications mainly involving edema, granuloma, fibrosis, and scarring. Selective posterior cricoarytenoid reinnervation is being performed by more surgeons and should be a promising addition to the BVFP surgical armamentarium.

CONCLUSION

Depending on techniques, the management of BVFP may be associated with several degrees of airway improvements while worsened or unchanged voice quality. The heterogeneity between studies, the lack of large-cohort controlled randomized studies and the confusion with posterior glottic stenosis limit the draw of clear conclusion about the superiority of some techniques over others.

Systematic review and meta-analysis of laryngeal reinnervation techniques in adults with unilateral and bilateral vocal fold palsies

OBJECTIVE

To evaluate the outcomes of reinnervation techniques for the treatment of adult unilateral vocal fold paralysis and bilateral vocal fold paralysis.

METHODS

A literature review was conducted in the Embase and Medline databases in English, with no limitations on the publication date. The outcome parameters of interest included visual, subjective perceptual, acoustic, aerodynamic analysis and electromyography. A meta-analysis with a random-effects model and inverse variance was calculated.

RESULTS

The systematic Preferred Reporting Items for Systematic Reviews and Meta-Analyses approach resulted in 27 studies, totalling 803 patients (747 unilateral cases and 56 bilateral cases). Thyroid cancer and/or surgery had caused unilateral vocal fold paralysis in 74.8 per cent of cases and bilateral vocal fold paralysis in 69.6 per cent of cases. Statistically significant improvements in patients were observed for voice, deglutition and decannulation (bilateral vocal fold paralysis). Meta-analysis of 10 reinnervation techniques was calculated for the maximum phonation time of 184 patients.

CONCLUSION

Reinnervation was shown to improve voice, swallowing and decannulation, but studies lacked control groups, limiting generalisability. Larger studies with controls are needed.

Bilateral selective laryngeal reinnervation in patients with bilateral vocal cord palsy

Objective

Bilateral selective reinnervation of the larynx aims to restore both vocal cord tone and abductor movements in patients with bilateral vocal cord palsy.

Methods

Four females and one male treated by bilateral selective reinnervation of the larynx were included in the present study. In all cases, both posterior cricoarytenoid muscles were reinnervated using the C3 right phrenic nerve root through the great auricular nerve graft, while adductor muscle tone was bilaterally restored using the thyrohyoid branches of the hypoglossal nerve through transverse cervical nerve grafts.

Results

After a minimum follow-up of 48 months, all patients were successfully tracheostomy free and had recovered normal swallowing. At laryngoscopy, the first patient recovered a left unilateral partial abductor movement, the second had complete bilateral abductor movements, the third did not show improvements of abductor movements, but symptomatology was improved, the fourth recovered partial bilateral abductor movements and the fifth case did not show improvements and needed posterior cordotomy.

Conclusions

Bilateral selective laryngeal reinnervation, although a complex surgical procedure, offers a more physiologic recovery in the treatment of bilateral vocal fold paralysis. Selection criteria still needs to be precisely defined to avoid unexpected failures.

Surgical Treatment Applied to Bilateral Vocal Fold Paralysis in Adults: Systematic Review

INTRODUCTION

Bilateral vocal fold paralysis is a condition accounting for great mortality and significant worsening in patients' quality of life. Treatment applied to these patients seek balance among breathing, airway protection and voice quality.

AIM

Critically and systematically reviewing the current literature on the topic in order to set the best technique to restore breathing comfort, without the need of tracheostomy, in patients with bilateral vocal fold paralysis. Furthermore, it seeks the surgical type technique accounting for the best breathing rate and for the smallest changes in voice parameters.

MATERIALS AND METHODS

Preferred Reporting Items for Systematic Reviews and Meta-Analyses method methodology and population, interventions, comparatives, outcomes and study design criteria were used as systematic search in the biggest databases and in the grey literature. The following meshes were used for the search: surgical interventions, surgical treatment, bilateral vocal cord paralysis, bilateral vocal fold paralysis, tracheostomy, decannulation, voice, and dysphonia. The selected studies should have followed the randomized clinical-trial type or be longitudinal observational controlled prospective studies (cohort studies).

RESULTS

In total, 3,548 articles were found. After duplicate studies were removed from the selection, the inclusion and exclusion criteria were applied and 06 articles were selected for qualitative analysis.

CONCLUSIONS

The assessed surgical procedures showed good cost-benefit to treat bilateral vocal fold paralysis, either because they improved the breathing function in most patients and allowed decannulation in patients with tracheostomy, or because they accounted for small changes to both voice parameters or deglutition. However, none of the described techniques has shown respiratory and functional outcomes better than those recorded for the other ones. The decision on what surgery to perform still must be made based on the judgement of an experienced surgeon.

Longitudinal Vocal Outcomes and Voice-Related Quality of Life After Selective Bilateral Laryngeal Reinnervation: A Case Study

PURPOSE

Bilateral vocal fold paralysis (BVFP) is a severe disorder that can result in respiratory, swallowing, and voice-related problems. Most surgical treatments do not restore laryngeal function and often need to compromise voice quality to preserve respiratory function. Laryngeal reinnervation (LR) may offer a solution to this problem, but literature on longitudinal outcomes of this procedure is scarce. This study aims to report the longitudinal vocal outcomes of BVFP after LR and subsequent voice therapy.

METHOD

The case of a 23-year-old man with BVFP after a traumatic dissection of both recurrent laryngeal nerves is described. Selective bilateral LR of both adductors and abductors was performed 5 months after the onset of BVFP. Voice therapy was provided after the LR procedure. Multidimensional voice assessments, including acoustic, perceptual, and patient-reported outcome measures (PROMs), were conducted 2, 5, 6.5, 8, and 31 months after LR.

RESULTS

An improvement of vocal capabilities and voice quality was noticed 6.5 months after LR, after 4.5 months of voice therapy, with normative values after 2.5 years. PROMs showed an improvement of voice-related quality of life, but some limitations to activities of daily living were still present. Inspiratory arytenoid abduction was not observed on laryngeal videostroboscopic findings in this patient, but tracheostomy was not required.

CONCLUSIONS

Voice therapy after LR helps establish healthy and efficient voice use without increasing compensatory hyperfunctional behavior. More research is needed to examine potential merits of voice therapy in the rehabilitation of vocal and respiratory functions after LR.

The Use of Laryngeal Electromyography to Determine Surgical Success Following Anastomosis and Implantation Reinnervation Surgeries for Vocal Fold Paralysis: A Systematic Review

BACKGROUND

The goal of this systematic review is to elucidate an evidence-based review of the benefit of laryngeal electromyography (LEMG) in determining surgical success following reanastamosis and implantation reinnervation surgery for treating vocal fold paralysis.

METHODS

We searched the following databases: PubMed, Embase and MEDLINE from inception to September 2022. Articles that included postoperative LEMG as a tool to evaluate patients after surgery for vocal fold paralysis were included.

RESULTS

A total of 203 studies were identified, 106 were read in full, and 11 that met the inclusion criteria were systematically reviewed.

CONCLUSION

The available evidence suggests that postoperative LEMG data is consistent with visual, perceptual, and acoustic analysis and therefore is a reliable tool in determining surgical success. LEMG provides both qualitative and quantitative evaluation, rather than the qualitative evaluation provided by standard methods, which yields additional parameters that more effectively and definitively characterize percent of muscle reinnervation at each stage and timeline the patient's recovery.

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.

Surgical Options for Pediatric Bilateral Vocal Cord Palsy: State of the Art

Management of pediatric bilateral vocal cord palsy (BVCP) is a controversial and challenging topic. It may represent a severe obstructive condition usually associated with respiratory distress, and, in such condition, tracheostomy has been considered the gold standard for a long time. Many surgical options have been described and used to increase the glottic space in BVCP (1), with ongoing research of less invasive techniques. The challenge and current trend in our department and in many major pediatric centers is to avoid tracheotomy through an early treatment. Many techniques introduced in the last decade reduced the number of tracheotomies and increased the decannulation rate. Furthermore, we observed a recent increase in attention to preserve the quality of the voice with new techniques, such as endoscopic arytenoid abduction lateropexy which is in our opinion an important innovation to improve glottic space with satisfactory voice results. We present a review of the literature about the evolution of the treatment options for pediatric BVCP during the years.

Exercise Induced Laryngeal Obstruction in Humans and Equines. A Comparative Review

Dynamic obstructions of the larynx are a set of disorders that occur during exercise in equines and humans. There are a number of similarities in presentation, diagnosis, pathophysiology and treatment. Both equines and humans present with exercise intolerance secondary to dyspnea. During laryngoscopy at rest, the larynx appears to function normally. Abnormalities are only revealed during laryngoscopy at exercise, seemingly triggered by increased ventilatory demands, and quickly resolve after cessation of exercise. Lower airway disease (asthma being the most prevalent condition), cardiac disease and lack of fitness are the major differentials in both species. Laryngoscopic examination during exercise should be performed from rest to peak exertion to allow for a comprehensive diagnosis, including where the airway collapse begins, and thereafter how it progresses. Dynamic disorders with most visual similarity between humans and equines are: aryepiglottic fold collapse (both species); equine dynamic laryngeal collapse (DLC) relative to some forms of human combined supraglottic/glottic collapse; and epiglottic retroversion (both species). Quantitative grading techniques, such as airway pressure measurement, that have proven effective in veterinary research are currently being piloted in human studies. Conditions that appear visually similar are treated in comparable ways. The similarities of anatomy and certain types of dynamic collapse would suggest that the equine larynx provides a good model for human upper respiratory tract obstruction during exercise. Thus, close collaboration between veterinarians and medical personal may lead to further advancements in understanding pathophysiologic processes, and enhance the development of improved diagnostic tests and treatments that will benefit both species.

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.

Functional identification of abductor and adductor branches for laryngeal transplantation

PURPOSE

This is a feasibility study of functional identification of the abductor and adductor recurrent laryngeal nerve branches, which could be used in the donor's larynx for functional laryngeal transplantation.

METHODS

The study was performed on swine (n = 3) and human (n = 4) models of a donor larynx. The recurrent laryngeal nerve and its branches were found. Using stimulator, abductor and adductor branches were identified, and glottis closing and opening were captured with an endoscope.

RESULTS

The result was positive if two ENT specialists noticed at least one adduction and one abduction movement in the same subject. It was obtained in three out of three swine and three out of four humans.

CONCLUSIONS

This study shows a way of reinnervation of a transplanted larynx which might result in a functional organ. It describes the first step of the procedure: functional identification of the abductor and adductor branches of the recurrent laryngeal nerve in the donor before the larynx is excised for transplantation.

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.

Selective recurrent laryngeal nerve stimulation using a penetrating electrode array in the feline model

OBJECTIVES/HYPOTHESIS

Laryngeal muscles (LMs) are controlled by the recurrent laryngeal nerve (RLN), injury of which can result in vocal fold (VF) paralysis (VFP). We aimed to introduce a bioelectric approach to selective stimulation of LMs and graded muscle contraction responses.

STUDY DESIGN

Acute experiments in cats.

METHODS

The study included six anesthetized cats. In four cats, a multichannel penetrating microelectrode array (MEA) was placed into an uninjured RLN. For RLN injury experiments, one cat received a standardized hemostat-crush injury, and one cat received a transection-reapproximation injury 4 months prior to testing. In each experiment, three LMs (thyroarytenoid, posterior cricoarytenoid, and cricothyroid muscles) were monitored with an electromyographic (EMG) nerve integrity monitoring system. Electrical current pulses were delivered to each stimulating channel individually. Elicited EMG voltage outputs were recorded for each muscle. Direct videolaryngoscopy was performed for visualization of VF movement.

RESULTS

Stimulation through individual channels led to selective activation of restricted nerve populations, resulting in selective contraction of individual LMs. Increasing current levels resulted in rising EMG voltage responses. Typically, activation of individual muscles was successfully achieved via single placement of the MEA by selection of appropriate stimulation channels. VF abduction was predominantly observed on videolaryngoscopy. Nerve histology confirmed injury in cases of RLN crush and transection experiments.

CONCLUSIONS

We demonstrated the ability of a penetrating MEA to selectively stimulate restricted fiber populations within the feline RLN and selectively elicit contractions of discrete LMs in both acute and injury-model experiments, suggesting a potential role for intraneural MEA implantation in VFP management.

LEVEL OF EVIDENCE

NA. Laryngoscope, 128:1606-1614, 2018.

Autologous thyroid cartilage graft implantation in medialization laryngoplasty: a modified approach for treating unilateral vocal fold paralysis

Medialization laryngoplasty is the standard surgical treatment for unilateral vocal fold paralysis. This study presents a modified approach in which a thyroid cartilage graft is implanted in medialization laryngoplasty. 22 patients who underwent this approach were included in the study. The results revealed that glottal incompetence and vocal performance were markedly improved following surgery, and the follow-up period ranged from 6 to 74 months (mean, 21.4 months). Acoustic analysis revealed significant improvements in the maximum phonation time (from 3.51 to 7.89 seconds, p < 0.001), F0 (from 221.7 to 171.0 Hertz, p = 0.025), and jitter (from 7.68 to 3.19, p < 0.001). Perceptual assessment revealed a significant decrease in voice grading (from 2.59 to 1.41, p < 0.001), roughness (from 1.82 to 1.23, p = 0.004), and voice breathiness (from 2.55 to 1.23, p < 0.001). None of the patients exhibited severe wound infection, tissue rejection, or other complications attributed to the surgical procedure. In conclusion, autologous thyroid cartilage implantation in medialization laryngoplasty medializes the vocal cord, minimizes the glottal gap, and improves the voice of patients with vocal fold paralysis. This procedure is characterized by simplicity, safety, and acceptable results.

Current Treatment Options for Bilateral Vocal Fold Paralysis: A State-of-the-Art Review

Vocal fold paralysis (VFP) refers to neurological causes of reduced or absent movement of one or both vocal folds. Bilateral VFP (BVFP) is characterized by inspiratory dyspnea due to narrowing of the airway at the glottic level with both vocal folds assuming a paramedian position. The primary objective of intervention for BVFP is to relieve patients’ dyspnea. Common clinical options for management include tracheostomy, arytenoidectomy and cordotomy. Other options that have been used with varying success include reinnervation techniques and botulinum toxin (Botox) injections into the vocal fold adductors. More recently, research has focused on neuromodulation, laryngeal pacing, gene therapy, and stem cell therapy. These newer approaches have the potential advantage of avoiding damage to the voicing mechanism of the larynx with an added goal of restoring some physiologic movement of the affected vocal folds. However, clinical data are scarce for these new treatment options (i.e., reinnervation and pacing), so more investigative work is needed. These areas of research are expected to provide dramatic improvements in the treatment of BVFP.

Transition of myosin heavy chain isoforms in human laryngeal abductors following denervation

The objective of this study was to investigate the myofiber subtype transition of human posterior cricoarytenoid (PCA) muscle after the injury to recurrent laryngeal nerve (RLN). PCA muscle specimens were obtained from 38 bilateral vocal fold paralysis patients underwent arytenoidectomy. According to the duration of RLN injury, all the cases were divided into five denervation groups: 6-12 months, 1-2, 2-3, 3-6, and >6 years. The normal PCA muscles from total laryngectomy patients were chosen as controls. Immunofluorescence was adopted to detect the expression level of myosin heavy chain (MHC)-I and MHC-II in PCA muscle. Quantitative real-time PCR was also used to assess the transcriptional level of MHC subtypes (MHC-I, MHC-IIa, MHC-IIb, MHC-IIx, embryonic-MHC, and peri-natal-MHC). Immunofluorescence showed that MHC-I-positive myofibers in denervation groups were much lower than control group, respectively, while MHC-II-positive myofibers were significantly higher than control group (P < 0.05). With the extension of denervation, the number of MHC-I-positive myofibers gradually decreased, while MHC-II gradually increased and peaked in 1- to 2-year group. Transcriptional level of MHC-I, MHC-IIa, and MHC-IIb in denervation groups significantly down-regulated compared with the control (P < 0.05), respectively. However, MHC-IIx, embryonic-MHC, and peri-natal-MHC significantly up-regulated in all denervation groups, and the highest level was in 1- to 2-year denervation group. Data from the present study demonstrated that the maximum transition of MHC subtypes in human PCA muscles occurred in 1-2 years after denervation, suggesting that laryngeal reinnervation before the occurrence of irreversible transition of MHC subtypes could maintain the structural integrity of laryngeal PCA muscles.

Nerve branches to the posterior cricoarytenoid muscle may complicate the laryngeal reinnervation procedure

OBJECTIVES/HYPOTHESIS

To better understand the reason for the low success rate of posterior cricoarytenoid (PCA) muscle reinnervation, we attempted to identify the communicating branches that may exist between the nerve branch to the PCA muscle and the other laryngeal adductors in addition to the interarytenoid (IA) muscle.

STUDY DESIGN

Quantitative histological assessment.

METHODS

Twenty human hemilarynges from patients with laryngeal or hypopharyngeal cancer were obtained after surgery and stained with Sihler's stain, which rendered the muscle translucent while counterstaining the neuroanatomy of the recurrent laryngeal nerve (RLN) inside the larynges.

RESULTS

The nerve supply to the PCA muscle was separated into two main branches. One upper branch supplied the horizontal compartment, and the lower branch supplied the vertical/oblique compartment. In 14 specimens, two nerve branches to the PCA muscle arose separately from the RLN. In six specimens, one single main branch arose from the RLN and immediately ramified into two secondary branches. In all specimens except one, the nerve branch to the horizontal compartment was connected to the IA muscle. However, no communicating branches were observed between the nerve to the PCA muscle and the other laryngeal adductors. No anastomosis between nerve branches to the horizontal and vertical/oblique compartments or other variations of nerve distribution were observed.

CONCLUSIONS

The communicating branches between the nerve branches to the PCA muscle and the IA muscle may be the only branch, complicating the reinnervation procedure. More investigations are needed to identify variations in the terminal branch distribution from the RLN.

LEVEL OF EVIDENCE

NA.