Functional recurrent laryngeal nerve regeneration using a silicon tube containing a collagen gel in a rat model.

In this study, we examined the effect of differing gap lengths on regeneration of transected recurrent laryngeal nerves using silicon tubes containing type I collagen gel and the ability of this regeneration to result in restoration of vocal fold movements in rats. We simulated nerve gaps in Sprague-Dawley rats by transecting the left recurrent laryngeal nerves and bridged the nerve stumps using silicon tubes containing type 1 collagen gel. Three experimental groups, in which the gap lengths between the stumps were 1, 3, or 5 mm, were compared with a control group in which the nerve was transected but was not bridged. After surgery, we observed vocal fold movements over time with a laryngoscope. At week 15, we assessed the extent of nerve regeneration in the tube, histologically and electrophysiologically. We also assessed the degree of atrophy of the thyroarytenoid muscle (T/U ratio). Restoration of vocal fold movements was observed in 9 rats in the 1-mm group, in 6 rats in the 3-mm group, and in 3 rats in the 5-mm group. However, in most rats, restoration was temporary, with only one rat demonstrating continued vocal fold movements at week 15. In electromyograph, evoked potentials were observed in rats in the 1-mm and 3-mm groups. Regenerated tissue in the tube was thickest in the 1-mm group, followed by the 3-mm and 5-mm groups. The regenerated tissue showed the presence of myelinated and unmyelinated nerve fibers. In assessment of thyroarytenoid muscle atrophy, the T/U ratio was highest in the 1-mm group, followed by the 3-mm and 5-mm groups. We successfully regenerated the nerves and produced a rat model of recurrent laryngeal nerve regeneration that demonstrated temporary recovery of vocal fold movements. This rat model could be useful for assessing novel treatments developing in the future.

Association of Vessel-Sealant Devices vs Conventional Hemostasis With Postoperative Neck Hematoma After Thyroid Operations.

Importance: Vessel-sealant devices (VSDs) have been popularized for use in thyroid operations; however, the association of their use with postoperative neck hematoma, a rare but potentially fatal complication, has not been well studied. Objective: To examine the association of VSDs vs conventional hemostasis (CH) in thyroid operations with the development of neck hematoma. Design, Setting, and Participants: This retrospective cohort study evaluated 10 903 patients in the Thyroid Procedure-Targeted Database of the National Surgical Quality Improvement Program from January 1, 2016, to December 31, 2017. One-to-one nearest-neighbor propensity score matching was conducted to adjust for differences in baseline covariates, including demographics, comorbidities, indications for thyroid procedure (goiter, Graves disease, malignant and benign thyroid nodule), and several other thyroid-specific characteristics, between the VSD and CH groups. Main Outcomes and Measures: The primary outcome was postoperative hematoma requiring intervention with open evacuation, return to the operating room, tracheostomy, additional observation, or extended length of stay. Secondary outcomes include recurrent laryngeal nerve injury, operative duration, and hospital length of stay. Results: One-to-one propensity score matching yielded 6522 patients (mean [SD] age, 52 [15] years; 8544 [78.4%] female) with 3261 in each exposure group such that distribution of observed baseline covariates was not different between groups of the same propensity score. Within the matched cohort, CH was associated with higher odds of neck hematoma compared with VSD (odds ratio, 2.33; 95% CI, 1.55-3.49; P < .001), with 34 (1.0%) hematomas in the VSD group and 78 (2.4%) in the CH group. On the basis of this analysis, the number needed to treat with a VSD to prevent 1 postoperative hematoma was 74. Secondary outcomes included longer length of hospital stay (incidence rate ratio, 1.29; 95% CI, 1.23-1.36; P < .001]) in the CH group compared with the VSD group but no difference in the odds of recurrent laryngeal nerve injury (odds ratio, 0.90; 95% CI, 0.73-1.11; P = .32) or operative duration (incidence rate ratio, 0.99; 95% CI, 0.96-1.01; P = .24). Conclusions and Relevance: Use of VSDs during thyroid operations was associated with reduced odds of neck hematoma compared with CH techniques without increasing odds of nerve injury. The results suggest that postoperative neck hematoma rates after thyroid surgery may differ based on the hemostasis technique and that these differences should be considered when developing strategies for quality improvement of postoperative outcomes.

Beyond Nodules-Diagnostic and Treatment Options in Pediatric Voice Disorders.

Pediatric dysphonia is common; however, not all vocal fold pathology in children is due to nodules. Laryngeal stroboscopy (transoral or transnasal) often is essential for the diagnosis of other not-nodule lesions. As in adults, multidisciplinary care with a speech language pathologist helps with patient buy-in for therapy. Breathy dysphonia due to glottic incompetence may be related to vocal fold movement impairment (VFMI) or posterior glottic insufficiency. There are several medialization procedures available for children with VFMI due to recurrent laryngeal nerve injury.

Functional electrical stimulation following nerve injury in a large animal model.

INTRODUCTION: Controversy exists over the effects of functional electrical stimulation (FES) on reinnervation. We hypothesized that intramuscular FES would not delay reinnervation after recurrent laryngeal nerve (RLn) axonotmesis. METHODS: RLn cryo-injury and electrode implantation in ipsilateral posterior cricoarytenoid muscle (PCA) were performed in horses. PCA was stimulated for 20 weeks in eight animals; seven served as controls. Reinnervation was monitored through muscle response to hypercapnia, electrical stimulation and exercise. Ultimately, muscle fiber type proportions and minimum fiber diameters, and RLn axon number and degree of myelination were determined. RESULTS: Laryngeal function returned to normal in both groups within 22 weeks. FES improved muscle strength and geometry, and induced increased type I:II fiber proportion (p = 0.038) in the stimulated PCA. FES showed no deleterious effects on reinnervation. DISCUSSION: Intramuscular electrical stimulation did not delay PCA reinnervation after axonotmesis. FES can represent a supportive treatment to promote laryngeal functional recovery after RLn injury. Muscle Nerve 59:717-725, 2019.

Recurrent Laryngeal Nerve Injury and Swallowing Dysfunction in Neonatal Aortic Arch Repair.

BACKGROUND: We evaluated the incidence, clinical effect, and recovery rate of vocal cord dysfunction (VCD) and swallowing dysfunction in neonates undergoing aortic arch repair. METHODS: We retrospectively evaluated 101 neonates who underwent aortic arch reconstruction from 2008 to 2015. Direct flexible laryngoscopy was performed in 89 patients before initiation of postoperative oral feeding after Norwood (n = 63) and non-Norwood (n = 26) arch reconstruction. We defined VCD as immobility of vocal cords or their lack of coaptation and poor mobility. RESULTS: The incidence of VCD after aortic arch repair was 48% (n = 43). There was no significant difference between the VCD and non-VCD groups in postoperative length of stay, extubation failure, cardiopulmonary bypass, cross-clamp, selective cerebral perfusion time, operative death, and The Society of Thoracic Surgeons-European Association for Cardio-Thoracic Surgery (STAT) Congenital Heart Surgery Mortality Categories. Placement of gastrostomy (p = 0.03) and documented aspiration (p = 0.01) were significantly more common in VCD patients. The incidence of VCD was 41% (n = 26) after Norwood and 65% (n = 17) after non-Norwood repairs (p = 0.06). Gastrostomy was required in 44 Norwood patients vs 9 non-Norwood patients (p = 0.004). Median length of stay was similar in Norwood patients with or without VCD (p = .28) but was significantly longer in non-Norwood patients with VCD vs those without (p = 0.002). At follow-up direct flexible laryngoscopy, VCD recovery was 74% (14 of 19) in the Norwood group and 86% (12 of 14) in the non-Norwood group. CONCLUSIONS: The incidence of VCD and swallowing dysfunction in neonates undergoing aortic arch reconstruction is high. Patients with VCD have a significantly higher incidence of gastrostomy placement and aspiration. In the Norwood population, length of stay is not associated with presence or absence of VCD. More than 70% of patients in each group who had direct flexible laryngoscopy follow-up recovered vocal cord function.

Recurrent laryngeal nerve injury after thyroid and parathyroid surgery: Incidence and postoperative evolution assessment.

Recurrent laryngeal nerve (RLN) injury is a feared complication after thyroid and parathyroid surgery. It induces important postoperative morbidity. The present study aimed to assess the incidence of transient/permanent postoperative RLN injuries after thyroid and parathyroid surgery in the present cohort, to observe the timing of recovery, and to identify risk factors for permanent RLN injury after thyroidectomy.All consecutive patients operated on at our institution for thyroid and parathyroid pathologies from 2005 to 2013 were reviewed for vocal cord paresis. Vocal cord paresis was defined based on postoperative fiberoptic laryngoscopy. Demographics, intraoperative details, and postoperative outcomes were collected. Treatment types were assessed, and recovery times collected. Patients with vocal cord paresis on preoperative fiberoptic laryngoscopy were excluded from the analysis.The cohort included 451 thyroidectomies (756 nerves at risk) and 197 parathyroidectomies (276 nerves at risk). There were 63 postoperative vocal cord pareses after thyroidectomy and 13 after parathyroidectomy. Sixty-nine were transient (10.6%) and 7 permanent (1.1%). The main performed treatment was speech therapy in 51% (39/76) of the patients. Median recovery time after transient injuries was 8 weeks. In the group with vocal cord paresis, risk factors for permanent injuries after thyroidectomy were previous thyroidectomy and intraoperative RLN injury on univariate analysis. On multivariate analysis, only intraoperative RLN injury remained significant.Most of the patients with transient postoperative RLN injury recovered normal vocal cord mobility within 6 months. The most common performed treatment was in this cohort speech therapy. Permanent RLN injuries remained rare (1.1%).

Management of unilateral recurrent laryngeal nerve injury after thyroid surgery: A review.

BACKGROUND: Recurrent laryngeal nerve (RLN) damage because of thyroid and parathyroid surgery has been recognized for over a century. Injury rates have been slowly decreasing in this period while effective treatment strategies have been increasing. METHODS: Recent literature was evaluated on the topics of anatomy, pathophysiology, avoidance, and conservative and surgical treatment of RLN injury. Data for this literature review were identified by PubMed and references from relevant articles using the search terms "thyroid," "laryngeal nerve," and "injury." Only articles published in English between 1990 and 2015 were included. RESULTS: Advances in technique and equipment have made injury less likely. The evidence and role for neuromonitoring is discussed. Treatment strategies may include speech therapy, vocal cord augmentation using injection, laryngeal framework surgery techniques (including laryngoplasty and arytenoid adduction), and reinnervation. CONCLUSION: Injury rates in specialist centers are very low. Good to excellent results may be obtained in most cases.

Reversing Age Related Changes of the Laryngeal Muscles by Chronic Electrostimulation of the Recurrent Laryngeal Nerve.

Age related atrophy of the laryngeal muscles -mainly the thyroarytenoid muscle (TAM)- leads to a glottal gap and consequently to a hoarse and dysphonic voice that significantly affects quality of life. The aim of our study was to reverse this atrophy by inducing muscular hypertrophy by unilateral functional electrical stimulation (FES) of the recurrent laryngeal nerve (RLN) in a large animal model using aged sheep (n = 5). Suitable stimulation parameters were determined by fatiguing experiments of the thyroarytenoid muscle in an acute trial. For the chronic trial an electrode was placed around the right RLN and stimulation was delivered once daily for 29 days. We chose a very conservative stimulation pattern, total stimulation time was two minutes per day, or 0.14% of total time. Overall, the mean muscle fiber diameter of the stimulated right TAM was significantly larger than the non-stimulated left TAM (30µm±1.1µm vs. 28µm±1.1 µm, p<0.001). There was no significant shift in fiber type distribution as judged by immunohistochemistry. The changes of fiber diameter could not be observed in the posterior cricoarytenoid muscle (PCAM). FES is a possible new treatment option for reversing the effects of age related laryngeal muscle atrophy.

External Branch of the Superior Laryngeal Nerve Mediated Glottic Closing Force in the Porcine Model.

OBJECTIVES: Based on our laboratory's newly confirmed motor pathway for glottic closure, we measured the glottic closing force (GCF) during isolated stimulation of the external branch of the superior laryngeal nerve (eSLN) in the porcine model. Glottic closure is 1 of the primary mechanisms for prevention of aspiration during deglutition. METHODS: The recurrent laryngeal nerve (RLN) and eSLN were identified bilaterally in 4 porcine necks. Subsequently, GCF was measured with a pressure transducer as the distal ends of individual nerves were stimulated in 4 animals. The RLN mediated GCF was measured first, followed by isolated eSLN mediated GCF, followed by transection of the RLN and repeat measurement of the eSLN GCF. Ultimately, the cricothyroid (CT) muscle attachment was released and the GCF measured. RESULTS: The GCF during isolated eSLN stimulation before and after RLN transection is approximately 89% of the RLN mediated GCF in each animal. The GCF after CT release is approximately 84% of the RLN perceived GCF. Transection of the RLN did not alter the eSLN observed GCF. CONCLUSIONS: The GCF obtained during isolated eSLN stimulation is adequate for delivery of an appropriate laryngeal protective response and may be considered a target motor nerve for augmenting GCF in selected rehab settings.

Effects of Functional Electrical Stimulation on Denervated Laryngeal Muscle in a Large Animal Model.

Bilateral vocal fold paralysis (BVCP) is a life-threatening condition that follows injury to the Recurrent Laryngeal nerve (RLn) and denervation of the intrinsic laryngeal musculature. Functional electrical stimulation (FES) enables restoration and control of a wide variety of motor functions impaired by lower motor neuron lesions. Here we evaluate the effects of FES on the sole arytenoid abductor, the posterior cricoarytenoid (PCA) muscle in a large animal model of RLn injury. Ten horses were instrumented with two quadripolar intramuscular electrodes in the left PCA muscle. Following a 12-week denervation period, the PCA was stimulated using a once-daily training session for 8 weeks in seven animals. Three animals were used as unstimulated controls. Denervation produced a significant increase in rheobase (P < 0.001). Electrical stimulation produced a 30% increase in fiber diameter in comparison with the unstimulated control group (33.9 ± 2.6 µm FES+, 23.6 ± 4.2 µm FES-, P = 0.04). A trend toward a decrease in the proportion of type 1 (slow) fibers and an increase in type 2a (fast) fibers was also observed. Despite these changes, improvement in PCA function at rest was not observed. These data suggest that electrical stimulation using a relatively conservative set of stimulation parameters can reverse the muscle fiber atrophy produced by complete denervation while avoiding a shift to a slow (type 1) fiber type.

[Vocal cord paralysis--analysis of a cohort of 400 patients]. / Stimmlippenparesen--Untersuchungen an einem Kollektiv von 400 Patienten.

Vocal cord paralysis has diverse etiologies. In the present study, vocal chord paralysis caused by surgery/trauma was present in more than two thirds of the cases, followed by primary malignancy-associated paralysis. Thyroidectomy was the most common cause in bilateral paresis, especially if performed in recurrent or malignant disease. Voice therapy was promising in pa-tients with unilateral paresis and hoarseness as main symptom. Persistent dysphonia due to insufficiency of the glottic closure led to an operative glottis restricting procedure in only 6% of cases. In almost half the patients with dyspnea as the main symp-tom of bilateral vocal cord paresis, temporary tracheotomy or surgical glottis widening procedures had to be performed. The group of idiopathic and traumatic paresis patients showed the best spontaneous recovery within the first 12 months in comparison to primary malignancy-associated paralysis, which showed no recovery of the recurrens nerve.

Electrical stimulation and testosterone enhance recovery from recurrent laryngeal nerve crush.

OBJECTIVE: This study investigated the effects of a combinatorial treatment, consisting of a brief period of nerve electrical stimulation (ES) and systemic supraphysiologic testosterone, on functional recovery following a crush of the recurrent laryngeal nerve (RLN). STUDY DESIGN: Prospective, controlled animal study. METHODS: After a crush of the left RLN, adult male Sprague-Dawley rats were divided into four treatment groups: 1) no treatment, 2) ES, 3) testosterone propionate (TP), and 4) ES + TP. Each group was subdivided into 1, 2, 3, or 4 weeks post-operative survival time points. Groups had an n of 4- 9. Recovery of vocal fold mobility (VFM) was assessed. RESULTS: Brief ES of the proximal nerve alone or in combination with TP accelerated the initiation of functional recovery. TP administration by itself also produced increased VFM scores compared to controls, but there were no statistical differences between the ES-treated and TP-treated animals. Treatment with brief ES alone was sufficient to decrease the time required to recover complete VFM. Animals with complete VFM were seen in treatment groups as early as 1 week following injury; in the untreated group, this was not observed until at least 3 weeks post-injury, translating into a 66% decrease in time to complete recovery. CONCLUSIONS: Brief ES, alone or in combination with TP, promise to be effective therapeutic interventions for promoting regeneration following RLN injury.

Development of a nerve conduction technique for the recurrent laryngeal nerve.

OBJECTIVES/HYPOTHESIS: To develop a reliable and safe laryngeal nerve conduction technique and to obtain consistent parameters as normal reference values. STUDY DESIGN: A prospective single-arm study. METHODS: A nerve conduction test was performed on the contralateral normal side in 42 patients with unilateral vocal fold palsy. The recording was performed in the intact thyroarytenoid muscle using a monopolar needle. The electrical stimulation using a 37-mm monopolar needle was applied 3 cm below the lower margin of the cricoid cartilage, just lateral to the trachea and medial to the carotid artery, and its intensity was gradually increased until the amplitude of the electrical response reached the maximum level. The latency of the evoked muscle response was acquired at the first evoked waveform deflection from the baseline. RESULTS: The average latency of the recurrent laryngeal nerves was 1.98 ± 0.26 ms. The latencies showed normal distribution according to the quantile-quantile plot and Kolmogorov-Smirnov test (P = .098). There was no significant difference in latencies between the right and left recurrent laryngeal nerves. Anthropometric factors including height and weight did not show any correlation with the latencies. CONCLUSIONS: We developed a reliable and safe laryngeal nerve conduction technique and obtained normal reference values for the recurrent laryngeal nerve conduction study. This laryngeal nerve conduction study can be an additional tool for detecting recurrent laryngeal nerve injury if it is performed in combination with the conventional laryngeal electromyography. LEVEL OF EVIDENCE: 4.

Intravenous mesenchymal stem cell therapy after recurrent laryngeal nerve injury: a preliminary study.

OBJECTIVES/HYPOTHESIS: Intravenous administration of mesenchymal stem cells (MSCs) has been recently shown to enhance functional recovery after stroke and spinal cord injury. The therapeutic properties of MSCs are attributed to their secretion of a variety of potent antiinflammatory and neurotrophic factors. We hypothesize that intravenous administration of MSCs after recurrent laryngeal nerve (RLN) injury in the rat may enhance functional recovery. STUDY DESIGN: Animal Research. METHODS: Twelve 250-gram Sprague-Dawley rats underwent a controlled crush injury to the left RLN. After confirming postoperative vocal fold immobility, each rat was intravenously infused with either green fluorescent protein-expressing MSCs or control media in a randomized and blinded fashion. Videolaryngoscopy was performed weekly. The laryngoscopy video recordings were reviewed and rated by a fellowship-trained laryngologist who remained blinded to the intervention using a 0 to 3 scale. RESULTS: At 1 week postinjury, the MSC-infused group showed a trend for higher average functional recovery scores compared to the control group (2.2 vs 1.3), but it did not reach statistical significance (P value of 0.06). By 2 weeks, however, both groups exhibited complete return of function. CONCLUSIONS: These pilot data indicate that with complete nerve transection by crush injury of the RLN in rat, there is complete recovery of vocal fold mobility at 2 weeks. At 1 week postinjury, animals receiving intravenous infusion of MSCs showed a trend for greater functional recovery, suggesting a potential beneficial effect of MSCs; however, this did not reach statistical significance. Therefore, no definite conclusions can be drawn from these data and further study is required. LEVEL OF EVIDENCE: N/A.

Types and timing of therapy for vocal fold paresis/paralysis after thyroidectomy: a systematic review and meta-analysis.

OBJECTIVES: To perform a systematic literature review to evaluate the type and timing of therapy for vocal fold paresis/paralysis after thyroidectomy and develop a primary decision-making pathway. STUDY DESIGN: Meta-analysis. METHODS: Four databases and one journal were searched using the key words of "thyroidectomy," "vocal cord paresis/paralysis," and "therapy." Study quality was evaluated using the Cochrane Collaboration's risk of bias tools. Data regarding type and timing of therapy were extracted from 39 articles. Odds ratios (ORs), relative risk (RR), 95% confidence interval, and heterogeneity were recorded. Logistic regression analysis was performed to determine the relationships between timing and OR/RR. RESULTS: Among the 13 studies investigating unilateral paresis/paralysis, five focused on early therapy (0-6 months). In these studies, the OR for clinical heterogeneity was significantly higher after neurolysis than after injection laryngoplasty and voice training (Q = 17.002, I(2) = 78%, P = 0.000), and the RR for heterogeneity was significantly higher after injection laryngoplasty at ≥12 months than <12 months (Q = 9.984, I(2) = 89.9%, P = 0.002). In the 26 studies that investigated bilateral paresis/paralysis, the OR for heterogeneity was significantly higher for bilateral posterior cordectomy than for endolaryngeal laterofixation (Q = 3.510, I(2) = 71.5%, P = 0.061) and laser arytenoidectomy with posterior cordectomy (Q = 2.90, I(2) = 65.6%, P = 0.088). CONCLUSIONS: For unilateral vocal fold paresis/paralysis after thyroidectomy, we recommend absorbable mass injection laryngoplasty, voice training, and neurolysis during the first 12 months but laryngeal reinnervation after 12 months. For bilateral vocal fold paresis/paralysis, we recommend early laterofixation and combined laser arytenoidectomy with posterior cordectomy after 12 months.

[Unilateral laryngeal nerve paralysis in the adult: Epidemiology, symptoms, physiopathology and treatment]. / Paralysies laryngées unilatérales de l'adulte : épidémiologie, symptomatologie, physiopathologie et traitement.

In France, the main causes for unilateral laryngeal nerve paralysis in the adult patient are surgery and malignant tumors. Most of unilateral laryngeal nerve paralysis following thyroid surgery will recover within the first six postoperative months. At the time of unilateral laryngeal nerve paralysis, swallowing impairment and dyspnea occur in around 30% and 5% of cases, respectively. In the face of a unilateral laryngeal nerve paralysis occurring without a history of trauma of surgery, the main paraclinical examination to perform is a computed laryngeal nerve examination analyzing the whole length of the nerve involved. Speech therapy efficiency is related to the degree of severity of the symptoms related to unilateral laryngeal nerve paralysis. In the vast majority of cases, laryngeal medialization approaches improve dysphonia and swallowing impairment related to unilateral laryngeal paralysis, but not dyspnea.

Functional regeneration of recurrent laryngeal nerve injury during thyroid surgery using an asymmetrically porous nerve guide conduit in an animal model.

BACKGROUND: Vocal cord paralysis (VCP) caused by recurrent laryngeal nerve (RLN) damage during thyroidectomy commonly results in serious medico-legal problems. The purpose of this study was to evaluate the usefulness of an asymmetrically porous polycaprolactone (PCL)/Pluronic F127 nerve guide conduit (NGC) for functional regeneration in a RLN injury animal model. METHODS: A biodegradable, asymmetrically porous PCL/F127 NGC with selective permeability was fabricated for use in this study. A 10-mm segment of left RLN was resected in 28 New Zealand white rabbits, and then an asymmetrically porous NGC or a nonporous silicone tube was interposed between both stumps and securely fixed. Vocal cord mobility was endoscopically evaluated at one, four, and eight weeks postoperatively. Nerve growth through NGCs was assessed by toluidine blue staining, and thyroarytenoid (TA) muscle atrophy was evaluated by hematoxylin and eosin staining. Immunohistochemical stainings for acetylcholinesterase (AchE), anti-neurofilament (NF), and anti-S100 protein were also conducted, and transmission electron microscopy (TEM) was used to evaluate functional nerve regeneration. RESULTS: At eight weeks postoperatively, endoscopic evaluations showed significantly better recovery from VCP in the asymmetrically porous PCL/F127 NGC group (6 of 10 rabbits) than in the silicone tube group (1 of 10 rabbits). Continued nerve growth on the damaged nerve endings was observed with time in the asymmetrically porous PCL/F127 NGC-interposed RLNs. TA muscle dimensions and AchE expressions in TA muscle were significantly greater in the asymmetrically porous PCL/F127 NGC group than in the silicone tube group. Furthermore, immunohistochemical staining revealed the expression of NF and S100 protein in the regenerated nerves in the asymmetrically porous PCL/F127 NGC group at eight weeks postoperatively, and at this time, TEM imaging showed myelinated axons in the regenerated RLNs. CONCLUSION: The study shows that asymmetrically porous PCL/F127 NGC provides a favorable environment for RLN regeneration and that it has therapeutic potential for the regeneration of RLN damage.

Recurrent laryngeal nerve regeneration through a silicone tube produces reinnervation without vocal fold mobility in rats.

OBJECTIVES: We established an animal model of recurrent laryngeal nerve reinnervation with persistent vocal fold immobility following recurrent laryngeal nerve injury. METHODS: In 36 rats, the left recurrent laryngeal nerve was transected and the stumps were abutted in a silicone tube with a 1-mm interspace, facilitating regeneration. The mobility of the vocal folds was examined endoscopically 5, 10, and 15 weeks later. Electromyography of the thyroarytenoid muscle was performed. Reinnervation was assessed by means of a quantitative immunohistologic evaluation with anti-neurofilament antibody in the nerve both proximal and distal to the silicone tube. The atrophy of the thyroarytenoid muscle was assessed histologically. RESULTS: We observed that all animals had a fixed left vocal fold throughout the study. The average neurofilament expression in the nerve both distal and proximal to the silicone tube, the muscle area, and the amplitude of the compound muscle action potential recorded from the thyroarytenoid muscle on the treated side increased significantly (p < 0.05) over time, demonstrating regeneration through the silicone tube. CONCLUSIONS: Recurrent laryngeal nerve regeneration through a silicone tube produced reinnervation without vocal fold mobility in rats. The efficacy of new laryngeal reinnervation treatments can be assessed with this model.

Neurotrophic factor-secreting autologous muscle stem cell therapy for the treatment of laryngeal denervation injury.

OBJECTIVES/HYPOTHESIS: To determine if the spontaneous reinnervation that characteristically ensues after recurrent laryngeal nerve (RLN) injury could be selectively promoted and directed to certain laryngeal muscles with the use of neurotrophic factor (NF)-secreting muscle stem cell (MSC) vectors while antagonistic reinnervation is inhibited with vincristine (VNC). STUDY DESIGN: Basic science investigation involving primary cell cultures, gene cloning/transfer, and animal experiments. METHODS: MSC survival assays were used to test multiple individual NFs in vitro. Motoneuron outgrowth assays assessed the trophic effects of identified NF on cranial nerve X (CNX)-derived motoneurons in vitro. Therapeutic NF was cloned into a lentiviral vector, and MSCs were transduced to secrete NF. Sixty rats underwent left RLN transection injury, and at 3 weeks received injections of either MSCs (n = 24), MSCs secreting NF (n = 24), or saline (n = 12) into the left thyroarytenoid muscle complex; half of the animals in the MSC groups simultaneously received left posterior cricoarytenoid injections of VNC, whereas half of the animals received saline. RESULTS: Ciliary neurotrophic factor (CNTF) had the greatest survival-promoting effect on MSCs in culture. The addition of CNTF (50 ng/mL) to CNX motoneuron cultures resulted in enhanced neurite outgrowth and branching. In the animal model, the injected MSCs fused with the denervated myofibers, immunohistochemistry demonstrated enhanced reinnervation based on motor endplate to nerve contact, and reverse transcriptase-polymerase chain reaction confirmed stable CNTF expression at longest follow-up (4 months) in the CNTF-secreting MSC treated groups. CONCLUSIONS: MSC therapy may have a future role in selectively promoting and directing laryngeal reinnervation after RLN injury.