A dysphagia model with denervation of the pharyngeal constrictor muscles in guinea pigs: functional evaluation of swallowing.

Introduction: Swallowing impairment is a crucial issue that can lead to aspiration, pneumonia, and malnutrition. Animal models are useful to reveal pathophysiology and to facilitate development of new treatments for dysphagia caused by many diseases. The present study aimed to develop a new dysphagia model with reduced pharyngeal constriction during pharyngeal swallowing. Methods: We analyzed the dynamics of pharyngeal swallowing over time with the pharyngeal branches of the vagus nerve (Ph-X) bilaterally or unilaterally transected, using videofluoroscopic assessment of swallowing in guinea pigs. We also evaluated the detailed anatomy of the pharyngeal constrictor muscles after the denervation. Results: Videofluoroscopic examination of swallowing showed a significant increase in the pharyngeal area during swallowing after bilateral and unilateral sectioning of the Ph-X. The videofluoroscopy also showed significantly higher pharyngeal transit duration for bilateral and unilateral section groups. The thyropharyngeal muscle on the sectioned side was significantly thinner than that on the intact side. In contrast, the thickness of the cricopharyngeal muscles on the sectioned and intact sides were not significantly different. The mean thickness of the bilateral thyropharyngeal muscles showed a linear correlation to the pharyngeal area and pharyngeal transit duration. Discussion: Data obtained in this study suggest that denervation of the Ph-X could influence the strength of pharyngeal contraction during pharyngeal swallowing in relation to thickness of the pharyngeal constrictor muscles, resulting in a decrease in bolus speed. This experimental model may provide essential information (1) for the development of treatments for pharyngeal dysphagia and (2) on the mechanisms related to the recovery process, reinnervation, and nerve regeneration following injury and swallowing impairment possibly caused by medullary stroke, neuromuscular disease, or surgical damage from head and neck cancer.

Transient Receptor Potential Ankyrin 1 Channel Alters Transforming Growth Factor Beta 1/Smad Signaling in Rat Vocal Fold Fibroblasts.

OBJECTIVES: Vocal fold scar remains a therapeutic challenge. Vocal fold fibroblasts (VFFs) secrete extracellular matrix (ECM), and transforming growth factor-beta 1 (TGF-ß1)-mediated fibroblast to myofibroblast differentiation is central to the development of fibrosis. The transient receptor potential (TRP) channel superfamily is a group of nonselective cation channels, and activation of TRP ankyrin 1 (TRPA1) channel has been shown to have antifibrotic effects through TGF-ß1/Smad signaling in various organs. This study aimed to elucidate expression of TRPA1 and the impact of TRPA1 activation on TGF-ß1/Smad signaling in VFFs. METHODS: Vocal folds were dissected from 10-week-old, male Sprague-Dawley rats and primary VFFs were established. TRPA1 was examined in VFFs and lamina propria via immunostaining. VFFs were treated with allyl isothiocyanate (AITC, TRP channel agonist, 10-5 M) ± TGF-ß1 (10 ng/ml) ± A-967079 (selective TRPA1 channel antagonist, 5.0 × 10-7 M) for 4 or 24 h. Trpa1, Smad3, Smad7, Col1a1, Acta2, and Has1 mRNA expression were quantified via qPCR. RESULTS: TRPA1 was expressed in cultured VFFs and the lamina propria. TGF-ß1 administration significantly increased Trpa1 compared to control. AITC alone did not alter Smad3, Smad7, Acta2, or ECM related genes. However, the combination of AITC and TGF-ß1 significantly increased Smad3 and decreased Smad7 and Acta2 compared to TGF-ß1 alone; A-967079 significantly reduced this response. CONCLUSIONS: VFFs expressed TRPA1, and the activation of TRPA1 regulated TGF-ß1/Smad signaling in VFFs. These findings provide preliminary insights into potential anti-fibrotic mechanisms of TRPA1 activation through TGF-ß1/Smad signaling in VFFs. LEVEL OF EVIDENCE: NA Laryngoscope, 2024.

Sustained Effects of Capsaicin Infusion into the Oropharynx on Swallowing in Perfused Rats.

OBJECTIVES: To examine the sustained effects of oropharyngeal capsaicin stimulation on the regulation of swallowing, we recorded the swallowing-related nerve activities during continuous infusion of capsaicin solution into the oropharynx. METHODS: In 33 in situ perfused brainstem preparation of rats, we recorded the activities of the vagus, hypoglossal, and phrenic nerves during fictive swallowing. The interburst intervals (IBIs) of the swallowing-related nerves during sequential pharyngeal swallowing (sPSW) elicited by electrical stimulation of the superior laryngeal nerve (SLN) during concurrent capsaicin stimulation of 10, 1, and 0.1 µM (n = 28) were compared with those during oropharyngeal infusion of saline (control) (n = 5). RESULTS: The IBIs during SLN-induced sPSW were reduced at 5 min after initiation of continuous infusion of 10 and 1 µM capsaicin solution. The IBIs showed significant decreases to -25.8 ± 6.9%, -25.9 ± 5.3, -18.3 ± 3.7, and -12.0 ± 1.6 at 30 min following 1 µM capsaicin stimulation at SLN stimulus conditions at 5 Hz of 1.2 times threshold, 10 Hz of 40 µA, 5 Hz of 60 µA, and 10 Hz of 60 µA, respectively. Continuous capsaicin stimulation of 0.1 µM solution did not show significant sustained effects. CONCLUSION: Pharmacological stimulation of capsaicin could provide time-dependent effects on the likelihood of swallowing, particularly subserving sustained facilitation of swallowing reflex with appropriate concentration of capsaicin. LEVEL OF EVIDENCE: NA Laryngoscope, 134:305-314, 2024.

Complementary Effect of Transcutaneous Cervical Stimulation by Interferential Current on Functional Dysphonia.

OBJECTIVES: Functional dysphonia (FD) varies in terms of vocal behavior and treatment efficacy. So-called hypofunctional dysphonia is characterized by insufficient subglottal pressure which causes a lack of driving power needed to vibrate the vocal folds leading to weak voice or aphonia in severe cases. While voice therapy is the initial treatment, some patients fail to respond to it. Interferential current (IFC) stimulation has been used as part of rehabilitation by physical therapists to reduce the progressive pain. IFC stimulation has also been developed as a laryngeal sensory stimulation device to modify the swallowing function by triggering swallowing reflex. Many researchers have shown recently in animal studies that laryngeal afferent inputs, such as vocal fold vibrations, subglottic pressure, flow rate, and vocal fold location affect vocal motor pattern and voice quality. However, IFC stimulation as a laryngeal afferent has not been verified. Herein, we assessed the effects of IFC stimulation to the neck on difficult functional dysphonia. METHODS: Six patients with refractory FD with insufficient subglottic pressure were assessed in this study. All six cases were females and two of them presented with aphonia. All cases were initially treated by voice therapy (VTx) such as flow phonation, water resistance therapy, or tube phonation for 2 months to increase subglottic pressure; however, this resulted in poor improvement in voice. We additionally performed VTx with concurrent application of IFC stimulation to the neck for 3 months, and the effects on voice were evaluated. RESULTS: VTx with IFC stimulation resulted in improved voice in all cases, demonstrating the improvement in maximum phonation time, subglottic pressure, and voice handicap index-10. CONCLUSIONS: Results from this clinical study suggest that VTx with IFC stimulation may be useful for adjusting vocal function in patients with FD caused by insufficient subglottic pressure.

Effects of Repeated Intracordal Glucocorticoid Injection on the Histology and Gene Expression of Rat Vocal Folds.

OBJECTIVES: Local injection of glucocorticoids (GCs) into the vocal folds has been used for treating the vocal fold lesions. While the positive effects on vocal fold nodules, polyps, or scarring have been clinically reported, some concern remains around the potential adverse effects such as vocal fold atrophy, and the mechanisms remain unclear. The present study examined the histology and gene expression of locally injected GC into the vocal folds in rats. METHODS: Thirteen-week-old male Sprague-Dawley rats were used in the experiments. Triamcinolone acetonide (TAA) or saline were administered repeatedly to the right vocal folds at a weekly interval, and rats were euthanized one week after the last administration for histological examination. Genetic examination was assessed hyaluronic acid (HA) metabolism at 1 or 3 days after a single TAA injection by quantitative real-time polymerase chain reaction (qRT-PCR). RESULTS: The group which underwent four TAA injections showed a significant decrease in HA in the lamina propria (LP), thickness of the LP and total cell numbers of the LP compared with the saline group. In contrast, there was no significant difference in the area of collagen accumulation and the thyroarytenoid muscle, although there was a tendency of atrophy of the muscle. After single injection of TAA, qRT-PCR showed a significant decrease in the expression of HA synthases, Has2 and Has3. CONCLUSIONS: The current animal study first demonstrates that repeated intracordal injection of GCs may lead to atrophy of vocal folds caused by decrease of deposition of HA in the LP and decrease of gene expression of Has.

Tamoxifen Alters TGF-ß1/Smad Signaling in Vocal Fold Injury.

OBJECTIVES: Effective treatments for vocal fold fibrosis remain elusive. Tamoxifen (TAM) is a selective estrogen receptor modulator and was recently reported to have antifibrotic actions. We hypothesized that TAM inhibits vocal fold fibrosis via altered transforming growth factor beta 1 (TGF-ß1) signaling. Both in vitro and in vivo approaches were employed to address this hypothesis. METHODS: In vitro, vocal fold fibroblasts were treated with TAM (10-8 or 10-9 M) ± TGF-ß1 (10 ng/ml) to quantify cell proliferation. The effects of TAM on genes related to fibrosis were quantified via quantitative real-time polymerase chain reaction. In vivo, rat vocal folds were unilaterally injured, and TAM was administered by oral gavage from pre-injury day 5 to post-injury day 7. The rats were randomized into two groups: 0 mg/kg/day (sham) and 50 mg/kg/day (TAM). Histological changes were examined on day 56 to assess tissue architecture. RESULTS: TAM (10-8 M) did not affect Smad3, Smad7, Acta2, or genes related to extracellular matrix metabolism. TAM (10-8 or 10-9 M) + TGF-ß1, however, significantly increased Smad7 and Has3 expression and decreased Col1a1 and Acta2 expression compared to TGF-ß1 alone. In vivo, TAM significantly increased lamina propria area, hyaluronic acid concentration, and reduced collagen deposition compared to sham treatment. CONCLUSIONS: TAM has antifibrotic potential via the regulation of TGF-ß1/Smad signaling in vocal fold injury. These findings provide foundational data to develop innovative therapeutic options for vocal fold fibrosis. LEVEL OF EVIDENCE: NA Laryngoscope, 133:2248-2254, 2023.

Effect of pharmacological inhibition of the pontine respiratory group on swallowing interneurons in the dorsal medulla oblongata.

OBJECTIVES: To examine the role of neurons of the pontine respiratory group (PRG) overlapping with the Kölliker-Fuse nucleus in the regulation of swallowing, we compared the activity of swallowing motor activities and interneuron discharge in the dorsal swallowing group in the medulla before and after pharmacological inhibition of the PRG. METHODS: In 23 in situ perfused brainstem preparation of rats, we recorded the activities of the vagus (VNA), hypoglossal (HNA), and phrenic nerves (PNA), and swallowing interneurons of the dorsal medulla during fictive swallowing elicited by electrical stimulation of the superior laryngeal nerve or oral water injection. Subsequently, respiratory- and swallow-related motor activities and single unit cell discharge were assessed before and after local microinjection of the GABA-receptor agonist muscimol into the area of PRG ipsilateral to the recording sites of swallowing interneurons. RESULTS: After muscimol injection, the amplitude and duration of swallow-related VNA bursts decreased to 71.3 ± 2.84 and 68.1 ± 2.76 % during electrically induced swallowing and VNA interburst intervals during repetitive swallowing decreased. Similar effects were observed for swallowing-related HNA. The swallowing motor activity was similarly qualitatively altered during physiologically induced swallowing. All 23 neurons were changed in either discharge duration or frequency after PRG inhibition, however, the general discharge patterns in relation to the motor output remained unchanged. CONCLUSION: Descending synaptic inputs from PRG provide control of the primary laryngeal sensory gate and synaptic activity of the PRG partially determine medullary cell and cranial motor nerve activities that govern the pharyngeal stage of swallowing.

Effects of Voice Therapy for Dysphonia due to Tension Imbalance in Unilateral Vocal Fold Paralysis and Paresis.

OBJECTIVES: Medialization procedures, such as type I thyroplasty, arytenoid adduction, and vocal fold injection, are popular treatments for dysphonia due to unilateral vocal fold paralysis (UVFP). However, dysphonia occasionally persists after medialization procedures owing to tension imbalance. This tension imbalance causes diplophonia, asymmetry and aperiodic vibrational flutter in travelling wave motion. Currently, there is no established treatment for tension imbalance. We herein report two cases with residual dysphonia due to tension imbalance following medialization for chronic UVFP, and another case presenting with dysphonia due to tension imbalance following chronic unilateral vocal fold paresis. METHODS: Three patients underwent voice therapy using flow phonation to facilitate increased airflow management in speech as well as forward oral resonance by focusing on balanced airflow. Phonatory outcomes were evaluated using stroboscopic findings, aerodynamic and acoustic measures, as well as self-rating. RESULTS: Aerodynamic assessments, acoustic findings and self-ratings improved in all three cases after voice therapy. Stroboscopic findings prior to voice therapy showed asymmetric vibration with glottic gap, which was improved after voice therapy. Fundamental frequency (F0) also increased post-therapy. CONCLUSIONS: In a previous canine study, it was shown that enhanced breath support with expiratory airflow resulted in increased F0, suggesting that enhanced breath support could increase vocal fold tension. The increased F0 achieved in the present cases following voice therapy may increase vocal fold tension with breath support. Thus, voice therapy using flow phonation may be effective for supporting vocal fold tension and improving dysphonia due to tension imbalance following UVFP and paresis.

Firing characteristics of swallowing interneurons in the dorsal medulla during physiologically induced swallowing in perfused brainstem preparation in rats.

Oropharyngeal swallowing is centrally mediated by a swallowing central pattern generator (Sw-CPG) in the medulla oblongata. The activity of the Sw-CPG depends on the sensory inputs determined by physical and chemical bolus properties. Here we investigate the sensory-motor integration during swallowing arising from different sensory sources. To do so we electrically stimulated the superior laryngeal nerve and we triggered swallowing with oral injections of distilled water or capsaicin solution and extracellularly recorded from swallowing interneurons in arterially perfused brainstem preparations of rats. We recorded the activities of 40 neurons, while monitoring the motor activities of the phrenic, vagal and hypoglossal nerves. Eighteen neurons responded to electrical stimulation of the ipsilateral superior laryngeal nerve, and 6 neurons were excited by oral fluid injection, while 16 non-respiratory neurons did not receive afferent inputs to either electrical or physiological stimuli. The cellular activities displayed by swallowing interneurons during electrical and physiological stimulation of pharyngeal and laryngeal afferent input reveal complex adaptations of the timing of firing patterns and frequencies. The modulation of neuronal activity is likely to contribute to the coordination of efficient bolus transfer during the pharyngeal stage of swallowing.

The Effects of Amniotic Membrane Transplantation on Vocal Fold Regeneration.

OBJECTIVES/HYPOTHESIS: Vocal fold (VF) scar and sulcus cause severe vocal problems, but optimal methods have not been established. Total replacement of the mucosa is required particularly for cases in which the whole lamina propria is occupied by severe fibrosis and vibratory function is totally lost. The amniotic membrane (AM) has been proven to have regenerative potential, as it contains stem cells and growth factors. The current study investigated the biocompatibility and effects of AM for regeneration of the VF mucosa. STUDY DESIGN: In vitro and in vivo studies. METHODS: Vocal fold fibroblasts (VFFs) from 13 Sprague-Dawley rats were seeded on AM and subjected to histology and immunohistochemistry, and gene expressions in the VFFs on AM were examined in in vitro study. Twelve New Zealand White rabbits were used in in vivo study. VFs were stripped down and were reconstructed with AM. The regenerative effects were examined 3 months later by histological examination. RESULTS: In vitro study indicated VFFs survived on AM and stained positively for Ki67, vimentin, and fibronectin. Gene expressions of Has1, Has2, and Hgf were significantly increased in the VFFs on AM compared with the other groups. The in vivo study indicated AM-transplanted VFs showed a significantly higher density of hyaluronic acid and lower density of collagen compared with sham VFs. CONCLUSIONS: The current preliminary study suggests biocompatibility and possible regenerative effects of AM for VFs. LEVEL OF EVIDENCE: NA Laryngoscope, 132:2017-2025, 2022.

Anti-inflammatory and Antioxidant Effects of Japanese Herbal Medicine Kyoseihatekigan on Vocal Fold Wound Healing.

OBJECTIVES: The Japanese herbal medicine kyoseihatekigan (KHG) has been used to alleviate the symptoms of croaky voice and globus hystericus, and each of its components has anti-inflammatory and antioxidant effects. However, the mechanisms underlying these beneficial actions of KHG on the vocal folds remain largely unknown. We examined the effects of KHG on rat vocal fold wound healing and assessed its anti-inflammatory and antioxidant properties. STUDY DESIGN: Animal model. METHODS: The vocal folds of Sprague-Dawley rats were unilaterally injured under endoscopy. Rats were divided into three groups based on KHG dosing from pre injury day 4 to post injury day 3: 0 mg/kg/day (sham group), 500 mg/kg/day (1% KHG group) and 1000 mg/kg/day (2% KHG group). Histologic changes were examined to assess the degree of inflammation and oxidative stress at day 3, and fibrosis at day 56. In addition, gene expression related to pro-inflammatory cytokines and transforming growth factor-beta1 (TGF-ß1) signaling was examined by quantitative real-time polymerase chain reaction (qPCR). RESULTS: Histologic analysis showed that the 1% and 2% KHG treatments significantly decreased cell infiltration and the 4-hydroxy-2-nonenalx-immunopositive area, and increased hyaluronic acid at day 3. Both KHG treatments significantly decreased fibrosis at day 56. qPCR revealed that mRNA of interleukin-1ß and cyclooxygenase-2 were significantly suppressed at day 1 and TGF-ß1 mRNA was significantly downregulated at day 5 in both KHG groups. CONCLUSIONS: The current findings suggest that KHG has anti-inflammatory and antioxidant effects in the early phase of vocal fold wound healing, which can lead to better wound healing with less scar formation.

Physiological Effects of Voice Therapy for Aged Vocal Fold Atrophy Revealed by EMG Study.

OBJECTIVES: Age-related voice changes are characterized as breathy, weak and strained, and a deterioration in vocal function in the elderly has been putatively linked to a reduced intensity of speech. They contribute to undesirable voice changes known as presbyphonia. These changes are caused by histological alterations in the lamina propria of the vocal fold mucosa and atrophy of the thyroarytenoid muscle, as well as by decreased respiratory support. There are several clinical studies on presbylarynx dysphonia showing the effectiveness of voice therapy. However, physiological changes of the presbylarynx following voice therapy have not been verified. The purpose of this prospective study was to demonstrate the clinical effectiveness of voice therapy for rehabilitating presbylarynx dysphonia, using vocal function assessments and thyroarytenoid muscular activity detection on laryngeal electromyography (LEMG). METHODS: 10 patients who were diagnosed with aged vocal fold atrophy from ages 60 to 87 years (mean age: 72 years) underwent approximately 12 weeks of voice therapy, mainly using forward-focused voice and vocal resistance training. Stroboscopic examination, aerodynamic assessment, acoustic analysis, Voice Handicap Index (VHI)-10, and LEMG were performed pre- and post-voice therapy. Vocal fold vibratory amplitude (VFVA) was measured by image analysis from the stroboscopic examinations. Turns analysis during steady phonation on LEMG was also assessed. RESULTS: Maximum phonation time, subglottic pressure, jitter, shimmer, VFVA, and VHI-10 significantly improved after voice therapy. The number of turns per second on LEMG also significantly increased. CONCLUSION: Our data suggest that voice therapy may improve vocal function and thyroarytenoid muscle activity in patients with aged vocal fold atrophy.

Thymidylate synthase locus LOH in combination with genotype has prognostic and predictive significance in colorectal cancer.

The aim of the current study was to investigate the prognostic and predictive significance of polymorphisms in the thymidylate synthase (TS) gene, alongside the loss of heterozygocity (LOH) at this gene locus in patients with colorectal cancer. Genotyping was carried out for a variable number tandem repeat (VNTR) polymorphism in the TS 5'-untranslated region, a G/C single nucleotide polymorphism (SNP) located within this VNTR, and for TS LOH status in 246 colorectal cancer and paired normal DNA samples. The results were analyzed in relation to clinicopathological features, including the prognostic and predictive significance of TS genotype in patients who underwent curative surgery. Complete VNTR, SNP and LOH information for TS was obtained in 226 cases. No significant associations were observed between normal tissue TS genotype status and clinicopathological features. LOH of TS was observed in 58% of tumor samples and was associated with poor prognosis independently of clinical stage. Cases exhibiting TS LOH were classified into the three groups of 2R/loss, 3G/loss and 3C/loss. Patients with 3C/loss genotype status had poor outcomes when treated by surgery alone, but their survival was similar to patients with other genotypes following Fluorouracil (5-FU)-based adjuvant chemotherapy. The results suggested that LOH of the TS locus may be a significant prognostic factor in colorectal cancer, with the genotype of the residual allele also demonstrating an influence on prognosis. In conclusion, LOH status should be considered when TS genotype is explored as a potential prognostic and predictive marker for 5-FU-based adjuvant chemotherapy in colorectal cancer.

Intracordal Injection of Basic Fibroblast Growth Factor in 100 Cases of Vocal Fold Atrophy and Scar.

OBJECTIVES/HYPOTHESIS: Vocal fold atrophy, scar, and sulcus reduce the vibratory function of the vocal fold mucosa, which causes severe refractory dysphonia. We have reported encouraging preliminary results using an intracordal injection of basic fibroblast growth factor (bFGF) and showed improvement in phonatory parameters and voice. The present study summarizes our experience with 100 cases of stiffened vocal folds that were treated with bFGF injections. STUDY DESIGN: Retrospective chart review with Interstitial Review Board (IRB) approval. METHODS: Local injection of bFGF was performed in 100 cases of vocal fold pathology, which included 43 cases of vocal fold atrophy, 41 cases with scar, and 16 cases with sulcus. Ten micrograms of bFGF were injected into the vocal folds under topical anesthesia 4 times in each patient. Therapeutic outcomes were examined with maximum phonation time (MPT), voice handicap index-10 (VHI-10), and GRBAS scale. RESULTS: MPT, VHI-10, and GRBAS scores significantly improved in all pathology groups. An improvement on the VHI-10 greater than five points was observed in 82% of atrophy cases, 78% of scar cases, and 67% of sulcus cases. Improvement on the VHI-10 was significantly better in the atrophy group than the scar or sulcus groups. The mild/moderate cases of scar and sulcus showed better improvement than severe cases. CONCLUSIONS: The current large case series indicates positive effects of intracordal injection of bFGF for improvement of voice with no severe adverse events. The effects appeared best for cases of atrophy, while the treatment of severe scar and sulcus requires further improvement. LEVEL OF EVIDENCE: 4 Laryngoscope, 131:2059-2064, 2021.

Effect of Voice Therapy Using Semioccluded Vocal Tract Exercises in Singers and Nonsingers With Dysphonia.

OBJECTIVES: Voice therapy with semioccluded vocal tract exercises (SOVTE) has a long history of use in singers and nonsingers with dysphonia. SOVTE with increased vocal tract impedance leads to increased vocal efficiency and economy. Although there is a growing body of research on the physiological impact of SOVTE, and growing clinical sentiment about its therapeutic benefits, empirical data describing its potential efficacy in singers and nonsingers are lacking. The objective of the current study is to evaluate vocal tract function and voice quality in singers and nonsingers with dysphonia after undergoing SOVTE. METHODS: Patients who were diagnosed with functional dysphonia, vocal fold nodules and age-related atrophy were assessed (n = 8 singers, n = 8 nonsingers). Stroboscopic examination, aerodynamic assessment, acoustic analysis, formant frequency, and self-assessments were evaluated before and after performing SOVTE. RESULTS: In the singer group, expiratory lung pressure, jitter, shimmer, and self-assessment significantly improved after SOVTE. In addition, formant frequency (first, second, third, and fourth), and the standard deviation (SD) of the first, second, and third formant frequency significantly improved. In the nonsinger group, expiratory lung pressure, jitter, shimmer, and Voice Handicap Index-10 significantly improved after SOVTE. However, no significant changes were observed in formant frequency. CONCLUSIONS: These results suggest that SOVTE may improve voice quality in singers and nonsingers with dysphonia, and SOVTE may be more effective at adjusting the vocal tract function in singers with dysphonia compared to nonsingers.

Regenerative Effects of Basic Fibroblast Growth Factor on Restoration of Thyroarytenoid Muscle Atrophy Caused by Recurrent Laryngeal Nerve Transection.

OBJECTIVES: Vocal fold atrophy following unilateral vocal fold paralysis is caused by atrophy of the thyroarytenoid (TA) muscle and remains a challenge. Medialization procedures are popular treatment options; however, hoarseness often remains due to the reduction in mass or tension of the TA muscle. Therefore, in addition to medialization procedures, TA muscle reinnervation is desirable. In vivo studies have shown the potential for basic fibroblast growth factor (bFGF) to affect muscular and nerve regeneration. The present study aimed to examine the regenerative effects of bFGF on restoration of TA muscle atrophy caused by recurrent laryngeal nerve transection. STUDY DESIGN: Prospective animal experiments with controls. METHODS: TA muscle atrophy was induced by unilateral transection of the recurrent laryngeal nerve. One month after transection, different doses (200 ng, 100 ng, 10 ng) of bFGF in 50 µL were repeatedly injected into the TA muscle four times with an interval of 1 week between injections. Saline only was injected in the sham group. Larynges were harvested for histologic and immunohistochemical examination 4 weeks after the final injection. RESULTS: The cross-sectional TA muscle area was significantly larger in the bFGF-treated groups compared with the sham-treated groups. Immunohistochemistry indicated that bFGF significantly increases the number of neuromuscular junctions and satellite cells in the TA muscle. CONCLUSIONS: These results suggest that local application of bFGF to the TA muscle may improve TA muscle atrophy caused by recurrent laryngeal nerve paralysis. Furthermore, bFGF may have regenerative effects on both nerves and muscles.

Effects of Voice Therapy on Laryngeal Motor Units During Phonation in Chronic Superior Laryngeal Nerve Paresis Dysphonia.

OBJECTIVES: Injury to the superior laryngeal nerve can result in dysphonia, and in particular, loss of vocal range. It can be an especially difficult problem to address with either voice therapy or surgical intervention. Some clinicians and scientists suggest that combining vocal exercises with adjunctive neuromuscular electrical stimulation may enhance the positive effects of voice therapy for superior laryngeal nerve paresis (SLNP). However, the effects of voice therapy without neuromuscular electrical stimulation are unknown. The purpose of this retrospective study was to demonstrate the clinical effectiveness of voice therapy for rehabilitating chronic SLNP dysphonia in two subjects, using interspike interval (ISI) variability of laryngeal motor units by laryngeal electromyography (LEMG). METHODS: Both patients underwent LEMG and were diagnosed with having 70% recruitment of the cricothyroid muscle, and 70% recruitment of the cricothyroid and thyroarytenoid muscles, respectively. Both patients received voice therapy for 3 months. Grade, roughness, breathiness, asthenia, and strain (GRBAS) scale, stroboscopic examination, aerodynamic assessment, acoustic analysis, and Voice Handicap Index-10 were performed before and after voice therapy. Mean ISI variability during steady phonation was also assessed. RESULTS: After voice therapy, both patients showed improvement in vocal assessments by acoustic, aerodynamic, GRBAS, and Voice Handicap Index-10 analysis. LEMG indicated shortened ISIs in both cases. CONCLUSIONS: This study suggests that voice therapy for chronic SLNP dysphonia can be useful for improving SLNP and voice quality.

A phase I/II exploratory clinical trial for intracordal injection of recombinant hepatocyte growth factor for vocal fold scar and sulcus.

Vocal fold scar and sulcus are intractable diseases with no effective established treatments. Hepatocyte growth factor (HGF) has preclinically proven to have potent antifibrotic and regenerative effects on vocal fold scar. The current Phase I/II clinical trial aims to examine the safety and effectiveness of intracordal injection of a recombinant human HGF drug for patients with vocal fold scar or sulcus. This is an open-label, dose-escalating, first-in-human clinical trial. Eighteen patients with bilateral vocal fold scar or sulcus were enrolled and divided into three groups: Step I received 1 µg of HGF per vocal fold; Step II received 3 µg of HGF; and Step III received 10 µg of HGF. Injections were administered once weekly for 4 weeks. The protocol treatment was performed starting with Step I and escalating to Step III. Patients were followed for 6 months post-treatment. Local and systemic safety aspects were examined as primary endpoints, and therapeutic effects were assessed as secondary endpoints using voice handicap index-10; maximum phonation time; vocal fold vibratory amplitude; grade, rough, breathy, asthenic, strained scale; and jitter. The results indicated no serious drug-related adverse events in either the systemic or local examinations. In whole-subject analysis, voice handicap index-10, vocal fold vibratory amplitude, and grade, rough, breathy, asthenic, strained scale were significantly improved at 6 months, whereas maximum phonation time and jitter varied. There were no significant differences in phonatory data between the step groups. In conclusion, intracordal injection of a recombinant human HGF drug was safe, feasible, and potentially effective for human patients with vocal fold scar or sulcus.

Voice rest after laryngeal surgery: what's the evidence?

PURPOSE OF REVIEW: This article aims to review previous research reports and to summarize current strategies for the optimal duration of voice rest and the effect of phonatory stimulation after phonomicrosurgery. RECENT FINDINGS: Voice rest is commonly recommended after laryngeal surgery to prevent worsening of vocal fold injuries. However, there are no established standard protocol for voice rest, and the type and duration of voice rest vary among clinicians. The most effective duration of voice rest is unknown. Recently, early vocal stimulation was recommended as a means to improve wound healing, on the basis of the basic and clinical researches. SUMMARY: It seems that early vocal stimulation may enhance the wound healing process in the vocal fold. More basic and clinical researches are warranted to investigate appropriate timing of initiation of stimulation, as well as the type and amount of stimulation that are available for human.

Enhancement of nose-to-brain delivery of hydrophilic macromolecules with stearate- or polyethylene glycol-modified arginine-rich peptide.

Recently, nose-to-brain delivery is a highly versatile route, which, in combination with novel drugs being developed for treating intractable CNS diseases, is a promising approach for the treatment of disorders. Furthermore, nano-sized drug carriers may improve nose-to-brain drug delivery by their capability to increase the transmucosal penetration of the drugs across nasal mucosal tissue barrier. However, there is still not enough information regarding mechanism of absorption pathway from nasal cavity to brain using nanocarriers. In this study, to investigate the nose-to-brain transport pathway using nanocarriers, the distribution in whole brain, nasal mucosa, and trigeminal nerve after intranasal administration of two kinds of nanocarriers which have hydrophobic or hydrophilic moiety. We used CHHRRRRHHC peptide (CH2R4H2C) as basic peptide carriers, and modified with stearic acid (STR) as a hydrophobic moiety (STR-CH2R4H2C) or polyethylene glycol (PEG)-based block copolymer (PEG-PCL) as hydrophilic moiety (PEG-PCL-CH2R4H2C). The nose-to-brain drug delivery can be improved by using STR-CH2R4H2C and PEG-PCL-CH2R4H2C as carriers. Specifically, hydrophobic STR-CH2R4H2C is more suitable for the transport of drugs targeting the forebrain, while PEG-PCL-modified CH2R4H2C is more suitable for transporting drugs targeting the hindbrain or whole brain tissue. In conclusion, the results of this study support the possibility that drug delivery pathways can be controlled depending on the properties of different carrier complexes.