Laryngeal Muscles Research Articles

Exploring Neuromuscular changes in the larynx: Insights from rat ultrasonic vocalizations

The study of rat ultrasonic vocalizations (USVs) provides a unique window into understanding the neuromuscular changes in the human larynx that occur with aging. Rats communicate with each other using USVs to convey positive and negative affective states in a variety of communication situations, such as juvenile play, mating, and alerting one another to threats (Brudzynski, 2013). USVs are produced using a glottal constriction to generate a jet of air which creates a whistle (Hakansson et al., 2022). The frequency of this whistle is modulated using the same muscles that humans use to modulate our vocalization frequency (the cricothyroid and thyroarytenoid) (Riede, 2011). The vocal fold cover is not engaged in vibration during USVs production. However, the neuromuscular similarities between rat USVs and human vocalizations make USVs a good model to investigate laryngeal neuromuscular mechanisms, such as the laryngeal muscle fibers and neuromuscular junctions (NMJs; the connections between peripheral nerves and muscle fibers).

Investigation of Acoustic Voice Characteristics of Individuals Diagnosed with Muscle Tension Dysphonia.

Muscle tension dysphonia (MTD) is a functional voice condition that causes irregular and imbalanced laryngeal and paralaryngeal muscle activation. Our study aimed to examine the acoustic characteristics of patients with MTD and reveal the differences between genders. The study retrospectively reviewed the acoustic examination findings from the files of patients diagnosed with MTD during evaluations in the laryngology outpatient clinic at a tertiary reference hospital between 2015 and 2022. The parameters assessed in prolonged vowel phonation analysis were fundamental frequency (F0), jitter, shimmer, noise-to-harmonic-to-ratio, and soft phonation index; in the counting task analysis, they were intensity, frequency, and semitone. Gender differences in acoustic measurements obtained during prolonged vowel phonation and counting tasks were also examined. The study included 80 individuals diagnosed with MTD. Although all parameters in the acoustic analysis of/a/ phonation were increased, differences were statistically significant only in the F0 and jitter parameters between females and males (p≤0.05). In the analysis of the counting task, the mean and minimum F0 parameters were significantly higher in females than in males (p=0.000). The mean dB level was decreased, particularly in the counting task, but the results for the intensity parameter did not differ significantly between genders (p>0.05). The values in the acoustic voice analysis parameters of patients with MTD were determined. These acoustic parameters are thought to guide the clinician in evaluating voice and determining voice therapy goals for MTD patients.

A case report of an Adachi-Williams type CG plus H aortic arch anomaly and implications for the development of the cervicothoracic circulation.

It is unclear whether the development of the branches of the subclavian artery is dependent on the proximal part of this artery since great vessel formation is partially regulated by haemodynamic stress. For example, the vertebral artery that usually arises from the subclavian artery might be affected by anomalies in the aortic arch branches. This uncertainty is partly due to the limited reports of highly anomalous cases of proximal and distal branching morphologies. Here, we report an Adachi-Williams type CG plus H aortic arch case found during student dissection and discuss the development of the cervicothoracic circulation. Here, we report an aberrant right subclavian artery that arose from the aorta distal to the left subclavian artery, via a retroesophageal course, whereas the right and left common carotid arteries arose from a short common trunk from the aorta (the carotid trunk) (Adachi-Williams type H). In addition, the left vertebral artery arose directly from the aortic arch between the carotid trunk and the left subclavian artery (Adachi-Williams type CG). Anomalies in the branching arteries from this aberrant right subclavian artery (the right vertebral artery, internal thoracic artery, thyrocervical trunk, costocervical trunk and thoracoacromial artery) were unidentifiable. The right vagus nerve directly innervates the laryngeal muscles without forming the recurrent nerve. The development of an aberrant right subclavian artery might affect haemodynamic stress in both the proximal and distal regions of the anterior limb region. The distal branching morphology, however, was normal, suggesting an independence of proximal and distal vasculature development. Since the concomitance of Adachi-Williams-type CG and H is rare, rather than sequentially develop, the distal arteries develop in a fine-tuned manner to adapt to anomalies in the proximal arteries.

Adductor Laryngeal Dystonia Versus Muscle Tension Dysphonia: Examining the Utility of Automated Acoustic Analysis to Detect Task Dependency as a Distinguishing Feature.

Differentiating adductor laryngeal dystonia (ADLD) and primary muscle tension dysphonia (pMTD) can be challenging. Unlike pMTD, ADLD is described as "task-dependent" with voiced phonemes purportedly provoking greater sign expression than voiceless phonemes. We evaluated the ability of two automated acoustic measures, the Cepstral Spectral Index of Dysphonia (CSID) and creak, to detect task dependency and to discriminate ADLD and pMTD. CSID, % creak, and listener ratings of dysphonia severity were obtained from audio recordings of patients with ADLD (n = 29) or pMTD (n = 33) reading two sentences loaded with either voiced or voiceless phonemes. Group × Sentence Type interaction effects confirmed that both "normalized" CSID and % creak detected task-dependent sign expression in ADLD (i.e., worse symptoms on the voiced- vs. voiceless-loaded sentence). However, a stepwise binary logistic regression analysis with group (ADLD vs. pMTD) as the dependent variable and % creak and normalized CSID variables (voiced, voiceless, and voiced vs. voiceless difference) as covariates revealed that the normalized CSID voiceless-laden sentence z score was the only significant predictor of group membership. Estimates of diagnostic precision from the normalized CSID voiceless sentence z scores were superior to % creak or listener ratings. Finally, the CSID possessed the strongest correlations with listener severity ratings regardless of group or sentence type. Although both normalized CSID and % creak detected task-dependent performance as a distinguishing feature of ADLD, a CSID profile wherein (a) the voiceless sentence z score was less severe than the voiced sentence and (b) the normalized voiceless sentence z score was within approximately 2 SDs (or less) of typical expectations provided the best estimates of diagnostic precision. Automated acoustic measures such as the CSID and creak provide useful information to objectively discriminate ADLD and pMTD.

Role of the Kölliker-Fuse/Parabrachial Complex in generation of post-inspiratory vagal and sympathetic nerve activities.

In the rat, the activity of laryngeal adductor muscles, the crural diaphragm, and sympathetic vasomotor neurons is entrained to the post-inspiratory (post-I) phase of the respiratory cycle, a mechanism thought to enhance cardiorespiratory efficiency. The identity of the central neurons responsible for transmitting respiratory activity to these outputs remains unresolved. Here we explore the contribution of the Kölliker-Fuse/Parabrachial nuclei (KF-PBN) in the generation of post-I activity in vagal and sympathetic outputs under steady-state conditions and during acute hypoxemia, a condition that potently recruits post-I activity. In artificially ventilated, vagotomised and urethane-anesthetised rats, bilateral KF-PBN inhibition by microinjection of the GABAA receptor agonist isoguvacine evoked stereotypical responses on respiratory pattern, characterised by a reduction in phrenic nerve burst amplitude, a modest lengthening of inspiratory time, and an increase in breath-to-breath variability, while post-I vagal nerve activity was abolished and post-I sympathetic nerve activity diminished. During acute hypoxemia, KF-PBN inhibition attenuated tachypnoeic responses and completely abolished post-I vagal activity while preserving respiratory-sympathetic coupling. Furthermore, KF-PBN inhibition disrupted the decline in respiratory frequency that normally follows resumption of oxygenation. These findings suggest that the KF-PBN is a critical hub for the distribution of post-I activities to vagal and sympathetic outputs and is an important contributor to the dynamic adjustments to respiratory patterns that occur in response to acute hypoxia. While KF-PBN appears essential for post-I vagal activity, it only partially contributes to post-I sympathetic nerve activity, suggesting the contribution of multiple neural pathways to respiratory-sympathetic coupling.

Impact of Audio-Visual Complexity on Symptomatology of Laryngeal Dystonia: A Virtual Reality Study.

Laryngeal dystonia (LD) is an isolated focal dystonia characterized by involuntary spasms in laryngeal muscles selectively impairing speech production. Anecdotal observations reported the worsening of LD symptoms in stressful or vocally demanding situations. To examine the impact of surrounding audio-visual complexity on LD symptomatology for a better understanding of disorder phenomenology. We developed well-controlled virtual reality (VR) environments of real-life interpersonal communications to investigate how different levels of audio-visual complexity may impact LD symptoms. The VR experiments were conducted over five consecutive days, during which each patient experienced 10 h of 4100 experimental trials in VR with gradually increasing audio-visual complexity. Daily reports were collected about patients' voice changes, as well as their comfort, engagement, concentration, and drowsiness from using VR technology. After a weekly VR exposure, 82% of patients reported changes in their voice symptoms related to changes in background audio-visual complexity. Significant differences in voice symptoms were found between the first two levels of the audio-visual challenge complexity independent of study sessions or VR environments. This study demonstrated that LD symptoms are impacted by audio-visual background across various virtual realistic settings. These findings should be taken into consideration when planning behavioral experiments or evaluating the outcomes of clinical trials in these patients. Moreover, these data show that VR presents a reliable and useful technology for providing real-life assessments of the impact of various experimental settings, such as during the testing of novel therapeutic interventions in these patients. Level 3 Laryngoscope, 2024.

Laryngeal Myasthenia Gravis in Voice Patients: Clinical, Serologic, and Neuromuscular Characterization of Seronegative Patients for Antibodies Against the Acetylcholine Receptor and Muscle-Specific Kinase

OBJECTIVELaryngeal myasthenia gravis (MG) is a focal manifestation of MG, and most patients are seronegative for antibodies against the acetylcholine receptor (AChR) and muscle specific kinase (MuSK). The purpose of this study was to determine the incidence of anti-AChR and anti-Musk antibodies in voice patients and to characterize the clinical and neuromuscular profiles of these patients in order to guide the diagnosis of laryngeal MG. STUDY DESIGNThis was a retrospective case-control study that included patients over the age of 18 who underwent laryngeal electromyography as part of their evaluation for neuromuscular junction dysfunction. METHODSCases and controls were evaluated serologically, for the anti-AChR, anti-MuSK, and anti-striational muscle antibodies, and neuromuscularly using the Tensilon test in some patients, repetitive nerve stimulation (RNS) test, and a treatment trial of pyridostigmine bromide. Cases were defined as either (1) positive anti-AChR or anti-MuSK, or (2) a positive Tensilon test or positive pyridostigmine bromide trial. RESULTSTwo hundred and eleven patients were screened; 61 (29%) patients were identified with laryngeal MG, and 77 (36%) patients were selected as controls. All case and control patients were seronegative for the anti-AChR and anti-MuSK antibodies with no significant difference between case and control status for seropositivity for anti-striational muscle antibodies. Of the case patients with an electrically positive Tensilon test (80.6%) who completed a treatment trial, 100% had symptom improvement. Of the case patients with a symptomatically positive Tensilon test (16.1%), only 60% of patients had improvement with a treatment trial. The RNS was more likely to be positive in case patients than control patients, and cases had a higher severity of paresis in all laryngeal muscles with LEMG evaluation. CONCLUSIONSLaryngeal MG is an underrecognized condition in the otolaryngology community owing in part to its seronegative presentation. Electrical improvement with a Tensilon test, or electrical or substantial symptomatic improvement with pyridostigmine bromide represent the most robust diagnostic criteria in these patients.

A meta-analysis on the improvement of vocal function in unilateral vocal cord paralysis by reinnervation of the recurrent laryngeal nerve

Objective:To conduct a systematic description and meta-analysis of the treatment of unilateral vocal cord paralysis（UVCP） with recurrent laryngeal nerve reinnervation through literature search, and to analyze the therapeutic effect of recurrent laryngeal nerve reinnervation on improving vocal function in UVCP. Methods:Electronic databases Pubmed, Web of Science, EMBASE, Cochrane Library, CNKI, and Wanfang databases were searched using relevant keywords and screened in strict accordance with the inclusion and exclusion criteria, and quality evaluations were conducted. Reported treatment outcomes were measured by relevant data extracted from literature, such as auditory perception assessment（GRBAS）, voice handicap index（VHI）, maximal phonation time（MPT）, jitter, shimmer, and noise harmonic ratio（NHR）, etc. Meta-analysis was performed by Revman5.3 and heterogeneity was analyzed using fixed effects or random effects models. Results:Eight articles were included in this study, all of which showed that the postoperative maximum phonation time of patients was significantly prolonged compared to preoperative, while the postoperative GRBAS score, Jitter, Shimmer, and NHR decreased compared to preoperative with statistical significance. Conclusion:The innervation of the internal laryngeal muscle was obtained through the reinnervation of the recurrent laryngeal nerve, which effectively improved the patient's vocal function and had a good long-term therapeutic effect. Although there was no difference in the efficacy of surgical methods for reconstructing the recurrent laryngeal nerve, the anastomosis between ansa cervicalis nerve and the recurrent laryngeal nerve is more ideal. Further randomized controlled studies with longer follow-up periods and larger samples will increase the credibility of their effectiveness.

Efficacy analysis of ansa cervicalis anterior root-recurrent laryngeal nerve anastomosis in the treatment of unilateral vocal cord paralysis

Objective:Investigates the application and clinical efficacy of ansa cervicalis anterior root-recurrent laryngeal nerve（RLN） anastomosis in the treatment of unilateral vocal fold paralysis（UVFP）. Methods:A prospective study was conducted with 92 UVFP patients admitted to our department from January 2018 to January 2022 who received ansa cervicalis anterior root-RLN anastomosis. The course of nerve injury ranged from 6 to 24 months. Videostroboscopy, voice subjective auditory perceptual assessment（GRBAS）, Voice Handicap Index（VHI-10）, voice objective acoustic analysis and laryngeal electromyography（EMG） were used to evaluate the efficacy of the operation. Results:Videostroboscopy showed that although the movement of vocal cords did not return to normal 12 months after operation, their volume and muscle tension were significantly improved and their positions were adducted to the median or near-median. Also the glottic closure, vocal cord position, vocal cord edge, symmetry and regularity of vocal cord vibration were significantly improved than pre-operation（P<0.01）. The five indexes of GRBAS（Grade, Roughness, Breathiness, Asthenia, Strain） and VHI-10, as well as voice acoustic parameters（Jitter, Shimmer, NHR） post-operation were significantly reduced, while the maximum phonation time（MPT） was significantly longer（P<0.01）. The results of laryngeal EMG indicated that the maximum voluntary motor unit recruitment（VMUR） post-operation was significantly recovered（P<0.01）, which confirmed that the affected laryngeal muscle obtained effective nerve reinnervation. Conclusion:Ansa cervicalis anterior root-RLN anastomosis can effectively improve the voice function of patients which is safe and satisfactory. It is an ideal method for the treatment of unilateral RLN injury.

Structural and functional brain alterations in laryngeal dystonia: A coordinate-based activation likelihood estimation meta-analysis.

Laryngeal dystonia (LD) is an isolated, task-specific, focal dystonia characterized by intermittent spasms of laryngeal muscles impairing speech production. Although recent studies have demonstrated neural alterations in LD, the consistency of findings across studies is not well-established, limiting their translational applicability. We conducted a systematic literature search to identify studies reporting stereotactic coordinates of peak structural and functional abnormalities in LD patients compared to healthy controls, followed by a coordinate-based activation likelihood estimation meta-analysis. A total of 21 functional and structural neuroimaging studies, including 31 experiments in 521 LD patients and 448 healthy controls, met the study inclusion criteria. The multimodal meta-analysis of these studies identified abnormalities in the bilateral primary motor cortices, the left inferior parietal lobule and striatum, the right insula, and the supplementary motor area in LD patients compared to healthy controls. The meta-analytical findings reinforce the current view of dystonia as a neural network disorder and consolidate evidence for future investigations probing these targets with new therapies.

Coactivation of the Laryngeal Muscles in Pigs Without External Neural Control Indicates Existence of an Intrinsic Neuronal Network

Electrophysiological studies of the larynx expose the mechanisms by which voice production is controlled. Previous studies have revealed certain phenomena during laryngeal oscillations that suggest a complex control mechanism.Starting from the principle of agonist-antagonist muscular pairing, the aim of this study was to gain a deeper insight into the function of the cricothyroid and thyroarytenoid muscles, both central to voice production.Electromyographic recordings were used to determine the response of the two muscles to different stimulation situations in an ex-vivo animal model of the denervated larynx of pigs (n=26).Using a set of different experiments, it was shown that when one muscle (cricothyroid or thyroarytenoid muscle) was electrically stimulated, a response was observed in the other muscle, which in the otherwise denervated larynx was caused only by the applied stimulation and exhibited the characteristics of compound action potentials. This response was reproducible in all larynxes examined and was present bidirectionally. No response was registered in the absence of stimulation.Results show the existence of coactivation of the cricothyroid and thyroarytenoid muscles in the absence of external innervation hinting at the presence of a localized neuronal network of the larynx that has not been described previously. Further morphological investigation is needed to determine the presence of this internal laryngeal neuronal network.

Extrinsic Laryngeal Muscle Activity and Vocal Economy in Professionally Trained Voices During Vocal Vibrato

Summary PurposeThe purpose of the present study was to determine the extrinsic laryngeal muscle activity and vocal economy during two different singing conditions (straight-tone singing vs. vibrato singing) over a physiologically relevant singing range. MethodsThirty professional singers or voice coaches participated in the study. The participants sang a sustained /a:/ vowel for approximately 5 seconds, once in straight-tone singing conditions and once more in vibrato. The target pitches were C3, F3, A3, C4, F4, A4, and C5. Surface electromyographic (sEMG) measures were performed in the infrahyoid (IH) muscle region and the suprahyoid (SH) muscle region. Contact quotient (CQ), sound pressure level (SPL), and fundamental frequencies were measured to derive the electroglottographic-based vocal economy parameter quasi-output cost ratio (QOCR). ResultssEMG measures show that IH and SH muscles significantly increased in activity with ascending pitch. IH and SH muscle activity were significantly higher when singing in vibrato than straight-tone. Moreover, SPL also increased with ascending pitch and when sung in vibrato. CQ increased and QOCR decreased as pitch ascended but did not significantly change when sung in vibrato. ConclusionSinging higher pitches were generally associated with higher extrinsic laryngeal muscle activity and lower QOCR values. When comparing the two singing conditions, the extrinsic laryngeal muscle activity was higher during vibrato, implicating that the IH and the SH muscles may contribute to rhythmic pulsations of pitch changes. Although the QOCR value did not show significant differences between the two singing conditions, a significantly high SPL during vibrato may indicate acoustical and physiological advantages while singing in vibrato.

Supraglottic Laryngeal Maneuvers in Adductor Laryngeal Dystonia During Connected Speech

ObjectiveAdductor laryngeal dystonia (AdLD) disrupts fine motor movements of vocal folds during speech, resulting in a strained, broken, and strangled voice. Laryngeal high-speed videoendoscopy (HSV) in connected speech enables the direct visualization of detailed laryngeal dynamics, hence, it can be effectively used to study AdLD. The current study utilizes HSV to investigate supraglottic laryngeal tissue maneuvers obstructing the view of the vocal folds, in AdLD and normophonic speakers during connected speech. Characterizing the laryngeal maneuvers in these groups can facilitate a deeper understanding of the normophonic voice physiology and AdLD voice pathophysiology. MethodsHSV data were obtained from six normophonic speakers and six patients with AdLD during production of connected speech. Three experienced raters visually analyzed the data to determine laryngeal tissues leading to obstructions of vocal folds in HSV images. The raters recorded the duration of each obstruction and indicated the specific tissue(s) leading to the obstruction After the completion of their individual visual analysis, the raters came to consensus about their observations and measurements. ResultsStatistical analysis indicated that AdLD patients exhibited higher occurrences of vocal fold obstructions and longer durations of obstructions compared to the normophonic group. Similar obstruction types were found in both groups, with the epiglottis being the primary site of obstruction for both. Participants with AdLD displayed significantly elevated occurrences of sphincteric compression resulting in vocal fold obstruction. ConclusionHSV can be used to study the movements of laryngeal tissues in detail during connected speech. The analysis of supraglottic laryngeal tissue dynamics in speech can help us characterize the AdLD pathophysiology. The study's findings regarding the tissues implicated in obstructions may potentially inform the development of patient-specific therapeutic strategies targeting individual control over specific laryngeal muscles during phonation and speech production.

Asymmetric triangular body-cover model of the vocal folds with bilateral intrinsic muscle activation.

Many voice disorders are linked to imbalanced muscle activity and known to exhibit asymmetric vocal fold vibration. However, the relation between imbalanced muscle activation and asymmetric vocal fold vibration is not well understood. This study introduces an asymmetric triangular body-cover model of the vocal folds, controlled by the activation of bilateral intrinsic laryngeal muscles, to investigate the effects of muscle imbalance on vocal fold oscillation. Various scenarios were considered, encompassing imbalance in individual muscles and muscle pairs, as well as accounting for asymmetry in lumped element parameters. Measurements of amplitude and phase asymmetries were employed to match the oscillatory behavior of two pathological cases: unilateral paralysis and muscle tension dysphonia. The resulting simulations exhibit muscle imbalance consistent with expectations in the composition of these voice disorders, yielding asymmetries exceeding 30% for paralysis and below 5% for dysphonia. This underscores the relevance of muscle imbalance in representing phonatory scenarios and its potential for characterizing asymmetry in vocal fold vibration.

Prognostic significance of T3b in papillary thyroid carcinoma: Appropriateness of classifying T3bN0M0 in patients aged 55years or older into stage II.

Papillary thyroid carcinoma (PTC) often extends to adjacent organs. According to the 8th Tumor-Node-Metastasis Classification, extension to the strap muscles was graded as T3b. We investigated the prognostic impact of T3b and the appropriateness of T3b in patients aged ≥55years who were classified as stage II. We enrolled 7811 patients with M0 PTC who underwent initial surgery at the Kuma Hospital (Kobe, Japan) between January 2007 and December 2016. Tumor extension was divided into T3b, T4a1 (extension to the tracheal adventitia, tracheal cartilage, esophageal muscle layer, recurrent laryngeal nerve, cricothyroid, and inferior constrictor muscles), and sT4a2 (extension to the subcutaneous soft tissues, tracheal mucosa, esophageal mucosa, internal jugular vein, brachiocephalic vein, larynx, pharynx, and sternocleidomastoid muscle). In patients ≥55years, the local recurrence-free survival (LR-FS), distant recurrence-free survival (DR-FS), and cause-specific survival (CSS) rates of T3bN0M0 were significantly poorer than those of T1/T2N0M0 but did not significantly differ from those of T3aN0M0. The LR-FS, DR-FS, and CSS rates of T3b stage II patients did not differ from those of T4a1 stage III patients but were significantly better than those of T4a2 stage III patients. T3b was an independent predictor of local recurrence and distant recurrence but not of death due to carcinoma in the multivariate analysis. In patients aged <55years with M0 PTC, T3b had no prognostic value in both analyses. T3bM0 patients are appropriate to be classified as stage II in patients ≥55years but be kept in stage I in patients <55years.

Utility of laryngeal electromyography for establishing prognosis and individualized treatment after laryngeal neuropathies.

Laryngeal electromyography (LEMG) is a technique used to characterize neuropathic injuries to the recurrent laryngeal nerve (RLN) and superior laryngeal nerve (SLN). The RLN and SLN innervate the laryngeal muscles to produce vocal fold (VF) motion and elongation, respectively. VF motion deficiencies can affect voice, swallowing, and breathing, which can greatly affect a patient's quality of life. Neuropathy-related VF motion deficiencies most often result from surgical interventions to the skull base, neck, or chest likely due to the circuitous route of the RLN. LEMG is ideally conducted by an electromyographer and an otolaryngologist using a team-approach. LEMG is a powerful diagnostic tool to better characterize the extent of neuropathic injury and thus clarify the prognosis for VF motion recovery. This updated review discusses current techniques to improve the positive and negative predictive values of LEMG using laryngeal synkinesis and quantitative LEMG. Synkinesis can be diagnosed by comparing motor unit potential amplitude during vocalization and sniff maneuvers when recording within adductor muscles. Quantitative turns analysis can measure motor unit recruitment to avoid subjective descriptions of reduced depolarization during vocalization, and normal values are >400 turns/s. By integrating qualitative, quantitative, and synkinetic data, a robust prognosis can help clinicians determine if VF weakness will recover. Based on LEMG interpretation, patient-centered treatment can be developed to include watchful waiting, temporary VF augmentation, or definitive medialization procedures and laryngeal reinnervation.

Towards enhanced functionality of vagus neuroprostheses through in silico optimized stimulation

Bioelectronic therapies modulating the vagus nerve are promising for cardiovascular, inflammatory, and mental disorders. Clinical applications are however limited by side-effects such as breathing obstruction and headache caused by non-specific stimulation. To design selective and functional stimulation, we engineered VaStim, a realistic and efficient in-silico model. We developed a protocol to personalize VaStim in-vivo using simple muscle responses, successfully reproducing experimental observations, by combining models with trials conducted on five pigs. Through optimized algorithms, VaStim simulated the complete fiber population in minutes, including often omitted unmyelinated fibers which constitute 80% of the nerve. The model suggested that all Aα-fibers across the nerve affect laryngeal muscle, while heart rate changes were caused by B-efferents in specific fascicles. It predicted that tripolar paradigms could reduce laryngeal activity by 70% compared to typically used protocols. VaStim may serve as a model for developing neuromodulation therapies by maximizing efficacy and specificity, reducing animal experimentation.

A Narrative Review on Laryngeal Manual Therapy Methods in Muscle Tension Dysphonia: Manual Techniques, Target Structures, and Tension Criteria.

Laryngeal manual therapy (LMT) has been known as one of the main techniques for decreasing musculoskeletal tension in the (para) laryngeal muscles in dysphonic patients, especially patients with muscle tension dysphonia (MTD). A narrative review on the available LMT methods in MTD. (Method).A review on the literature regarding to the LMT methods in MTD was conducted using electronic databases up to December 2022. To identify all eligible literature, hand searching was also utilized. Moreover, articles and books in which LMT methods were introduced or used for the first time, or had innovation and were complementary for previous LMT methods were included. Relevant sources were identified by two reviewers based on screened titles/abstracts and full texts. The authors found five main common and some miscellaneous LMT methods that may not be used as conventional methods in clinical and research settings. There are some similarities and differences between the available LMT methods based on the manual techniques, target anatomical structures, and tension criteria. Although there is not enough information about details of some LMT methods, we additionally tried to provide some details about LMT treatment protocol. The LMT is still at the beginning and it is necessary to revise the previous methods or develop new ones according to the similarities and differences have been found in this review. This paper will be useful for learning and teaching the LMT methods in MTD for clinicians and students who are interested in. The online version contains supplementary material available at 10.1007/s12070-024-04896-1.

Scaffold-Forming Collagen and Motor-Endplate Expressing Muscle Cells for Porcine Laryngoplasty.

Vocal fold paralysis impairs quality of life, and no curative injectable therapy exists. We evaluated injection of a novel in situ polymerizing (scaffold-forming) collagen in the presence and absence of muscle-derived motor-endplate expressing cells (MEEs) to promote medialization and recurrent laryngeal nerve (RLN) regeneration in a porcine model of unilateral vocal fold paralysis. Twelve Yucatan minipigs underwent right RLN transection. Autologous muscle progenitor cells were isolated from muscle biopsies, differentiated, and induced to MEEs. Three weeks after RLN injury, animals received injections of collagen, collagen containing MEEs, or saline into the paralyzed right vocal fold. Stimulated laryngeal electromyography and acoustic vocalization were used for function assessments. Larynges were harvested and underwent histologic, gene expression, and further quantitative analyses. Injections were well-tolerated, with the collagen scaffold showing immunotolerance and collagen-encapsulated MEEs remaining viable. Collagen-treated paralyzed vocal folds showed increased laryngeal adductor muscle volumes relative to that of the uninjured side, with those receiving MEEs and collagen showing the highest volumes. Muscles injected with MEEs and collagen demonstrated increased expression of select neurotrophic (BDNF and NTN1), motor-endplate (DOK7, CHRNA1, and MUSK), and myogenic (MYOG and MYOD) related genes relative to saline controls. In a porcine model of unilateral vocal fold paralysis, injection of in situ polymerizing collagen in the absence and presence of MEEs enhanced laryngeal adductor muscle volume, modulated expression of neurotrophic and myogenic factors, and avoided adverse material-mediated immune responses. Further study is needed to determine long-term functional outcomes with this novel therapeutic approach. NA Laryngoscope, 2024.

Piezoresistive sensors based on bacterial cellulose/ZnO/PPy composite materials for human signal monitoring and sound detection

Wearable piezoresistive sensors based on flexible electronics have gained considerable attention in motion monitoring, human-machine interface, disease diagnosis and health monitoring. Research on flexible wearable sensors can be applied not only to basic sensing and human motion monitoring, but also to sound visualization techniques. In this paper, a piezoresistive sensor was prepared from bacterial cellulose, zinc oxide and polypyrrole and its sensing performance as a sound detector was investigated. The sensor has good sensing performance and can monitor human motion signals. As a sound detector, it can not only recognize different sound signals by monitoring the movement of the laryngeal muscles, but also sense air vibration to detect and recognize various natural sounds. Due to its ability to capture and present sound signals, it is able to build a visual-centred information dissemination system through visualization technology.