Describing the Cellular Impact of IQOS™ Smoke Extract and Vibration on Human Vocal Fold Fibroblasts

OBJECTIVES

The isolated or combined effects of vibration and smoke extract (SE) from the IQOS™ "heat-not-burn" technology on human vocal fold fibroblasts (hVFF) were evaluated in an in vitro setting in order to elucidate their influence on vocal fold (patho-) physiology.

STUDY DESIGN

Experimental pilot study using intervention with IQOS™-SE in vitro.

METHODS

Immortalized hVFF were exposed to IQOS™-SE or control medium under static or vibrational conditions. A phonomimetic bioreactor was used to deliver vibrational patterns to hVFF over a period of 5days. Cytotoxicity was quantified by lactate dehydrogenase assay. Effects on extracellular matrix production, inflammation, fibrogenesis, and angiogenesis were assessed by reverse transcription-quantitative polymerase chain reaction, western blot, enzyme-linked immunosorbent assay, and Magnetic Luminex assays.

RESULTS

We observed significant changes induced either by IQOS™-SE exposure alone (matrix metalloproteinase 1, fibronectin, cyclooxygenase (COX)1, interleukin-8 gene expression), or by the combination of IQOS™-SE and vibration (hyaluronidase 2, COX2, interleukin-8 protein levels, vascular endothelial growth factor D).

CONCLUSION

Short-term in vitro exposure of hVFF to IQOS™-SE did not result in cytotoxicity and reduced the gene expression of measured inflammation mediators, but had no effect on their protein expression. However, the clinical effects of long-term IQOS™ use are still not known and further research is needed in order to assess, if IQOS™ is in fact less harmful than conventional cigarettes.

Synchronized and Desynchronized Dynamics Observed from Physical Models of the Vocal and Ventricular Folds

The ventricular folds, located superiorly to the vocal folds, do not usually vibrate during normal phonations. It has been shown, however, that they do vibrate together with the vocal folds under special circumstances such as voice pathology and singing voice. Towards understanding the effect of the ventricular fold oscillations on the vocal fold oscillations, the present study developed a synthetic model that takes into account anatomical features of the human ventricular folds. The synthetic model is made of flexible silicone compounds with material properties comparable to those of human ventricular fold tissues. In our experiment, an air-flow was injected into the vocal and ventricular fold models. As the distance between the left and right ventricular folds was reduced, the ventricular folds started to co-vibrate with the vocal folds. Depending upon the distance, various oscillation patterns of the vocal-ventricular folds were observed, e.g., synchronized dynamics with 1:1 or 1:2 frequency ratio and desynchronized chaotic dynamics. The observed chaotic dynamics might be related to voice pathology induced by the ventricular phonation. A computational model was further presented to elucidate the experimental findings.

Laryngeal Leishmaniasis: A Neglected, Emerging Disease in Northern Italy

Leishmaniasis represents an emerging public health issue in Mediterranean countries. The incidence of this condition has progressively risen in Northern Italy due to the growing number of immunocompromised people and probably due to climate changes. We hereby describe a case of relapsing laryngeal leishmaniasis in a female immunocompetent patient, presenting as aspecific chronic laryngitis. She was affected by severe asthma treated by inhaled steroid therapy, likely responsible for the parasite's diffusion through a locus minori resistentiae. The aspecific clinical presentation led to a delayed diagnosis and the lack of guidelines for the treatment caused multiple relapses. Biopsies of laryngeal lesions in the follow-up were performed by operative flexible videolaryngoscopy, thus avoiding general anesthesia and reducing associated healthcare costs. The aim of this report is to underline the diagnostic and therapeutic challenges that patients with this condition face and to present what is, to the best of our knowledge, the first application of prophylactic aerosolized pentamidine for relapsing laryngeal leishmaniasis.

Injuries of Different Surgical Instruments on the Vocal Folds of Dogs

OBJECTIVE

This study aimed to compare the damage of vocal folds caused by four different surgical instruments: CO2 laser, electrosurgical knife, plasma radiofrequency ablation, and steel knife.

STUDY DESIGN

Randomized controlled study.

METHODS

The CO2 laser, electrosurgical knife, plasma radiofrequency ablation, steel knife, and other instruments were used to simulate the laryngeal microsurgery on experimental dogs. Both total vocal fold resection and punctate ablation were performed. On the day of surgery and 6 days later, the vocal fold tissue from the surgical site was removed for histological evaluation. The extent of vocal fold damage was assessed using the automatic digital pathological scanning system.

RESULTS

We detected varying degrees of damage to the laryngeal tissues. Only the steel knife caused epidermal defects on the vocal fold tissue, while other instruments produced thermal damage of different degrees. Furthermore, the steel knife also showed better and faster healing. The plasma radiofrequency ablation was found to cause more severe thermal burns to vocal folds than other surgical instruments (P < 0.05). Six days postsurgery the inflammatory reaction from the steel knife had basically subsided, with only hyperplasia and tissue repair visible microscopically, showing the best healing degree. On the other hand, the radiofrequency ablation group showed the heaviest inflammatory reaction, indicating relatively poor prognosis (P < 0.05).

CONCLUSION

Compared with the CO2 laser, the electrotome and steel knife showed less damage and better healing, while the plasma radiofrequency ablation showed the most obvious thermal burns to laryngeal and vocal tissues during surgery, with relatively poor healing.

Better Breathing, Tougher Speaking? A Scoping Review of the Effects of Inhaled Corticosteroids on the Voice Quality of Asthmatic Children

BACKGROUND

Inhaled corticosteroids (ICS) are a common treatment for certain lung diseases, including chronic obstructive pulmonary disorder in adults, and asthma across the lifespan. There is a link between the use of ICS and dysphonia in adults. This scoping review aims to investigate the incidence of dysphonia, in children aged under 12, who use ICS to treat asthma.

METHODS

A scoping review was conducted, in accordance with the guidelines prescribed by Arksey and O'Malley (2005). ASHAWire, Science Direct, PubMed, and ProQuest databases were searched. Out of the total yield of 1471 articles, four articles met the inclusion criteria, that is, were primary studies reporting on voice quality in children who use ICS, who present with asthma and/or allergy.

RESULTS

The majority of papers yielded from the initial search were retrieved because of the use of the term "dysphonia" in the basic definitions of asthma and descriptors of its side effects. Only four studies presented primary data about the presence of dysphonia in asthmatic children (with or without comorbid allergic conditions). None specifically investigated the relationship between ICS and dysphonia. Research questions focused on side effects associated with allergies and asthma, which included some information about medication. Only three of the four studies conducted a comprehensive review of the voice and utilized video laryngoscopy.

DISCUSSION

The evidence of a relationship, between ICS and dysphonia in children, is not conclusive, and is complicated by the connection between asthma, and breath support for phonation. There is a need for more thorough and focused investigation of the relationship between ICS, with or without bronchodilator use, and any resultant effects on children's vocal quality.

Vocal Fold Fat injection for Glottic Insufficiency: Systematic Review

Vocal fold fat injection is a technique for treating glottic insufficiency (GI) resulting from various conditions. The use of fat as a graft has several advantages over other grafts. Similar pliability, and vibratory characteristics as a normal vocal fold, not causing foreign body reactions, having the potential to contain stem cells, and often can be done in the office. Long-term results, however, are unpredictable. The objective of this study is to carry out a systematic review of published articles using the technique of fat injection in the vocal folds.

STUDY DESIGN

Systematic review.

REVIEW METHODS

A literature search was conducted utilizing the combination of the following keywords "vocal folds fat injection," "laryngoplasty," and "autologous fat injection vocal folds." The criteria inclusion of the study for the systematic review were based on PICOTS (population, intervention, comparison outcome, timing, and setting) and Preferred Reporting Items for Systematic Reviews and Meta-analyses statements. Outcomes reviewed included technique, study duration, perceptual and acoustic analysis, and quality of life preoperation and 1-year postoperation.

RESULTS

A systematic review on PubMed, Cochrane, and Embase databases included 13 studies analyzing the data of 472 patients, that had fat injection laryngoplasty for treatment of GI. The causes of GI varied substantially across studies. Considerable heterogeneity across studies was found, including technique for harvest, processing the fat, site of injection, and acoustic analysis. In the studies that measured maximum phonation time (MPT) there was a significant improvement in a follow-up of at least 1 year after the injection. The patient's perception of vocal quality, measured by the Voice Handicap Index, also showed significant improvement in several studies after fat injection laryngoplasty.

CONCLUSION

Fat injection laryngoplasty seems to be safe and effective for GI for at least 12 months. Multiple studies show favorable outcomes, but the lack of control groups, the heterogeneity in inclusion criteria, nonstandardized techniques, and objective voice evaluations limit this evaluation.

The effect of swelling on vocal fold kinematics and dynamics

Swelling in the vocal folds is caused by the local accumulation of fluid, and has been implicated as a phase in the development of phonotraumatic vocal hyperfunction and related structural pathologies, such as vocal fold nodules. It has been posited that small degrees of swelling may be protective, but large amounts may lead to a vicious cycle wherein the engorged folds lead to conditions that promote further swelling, leading to pathologies. As a first effort to explore the mechanics of vocal fold swelling and its potential role in the etiology of voice disorders, this study employs a finite-element model with swelling confined to the superficial lamina propria, which changes the volume, mass, and stiffness of the cover layer. The impacts of swelling on a number of vocal fold kinematic and damage measures, including von Mises stress, internal viscous dissipation, and collision pressure, are presented. Swelling has small but consistent effects on voice outputs, including a reduction in fundamental frequency with increasing swelling (10 Hz at 30 % swelling). Average von Mises stress decreases slightly for small degrees of swelling but increases at large magnitudes, consistent with expectations for a vicious cycle. Both viscous dissipation and collision pressure consistently increase with the magnitude of swelling. This first effort at modeling the impact of swelling on vocal fold kinematics, kinetics, and damage measures highlights the complexity with which phonotrauma can influence performance metrics. Further identification and exploration of salient candidate measures of damage and refined studies coupling swelling with local phonotrauma are expected to shed further light on the etiological pathways of phonotraumatic vocal hyperfunction.

Versatile fiber-reinforced hydrogels to mimic the microstructure and mechanics of human vocal-fold upper layers

Human vocal folds are remarkable soft laryngeal structures that enable phonation due to their unique vibro-mechanical performances. These properties are tied to their specific fibrous architecture, especially in the upper layers, which comprise a gel-like composite called lamina propria. The lamina propria can withstand large and reversible deformations under various multiaxial loadings. Despite their importance, the relationships between the microstructure of vocal folds and their resulting macroscopic properties remain poorly understood. There is a need for versatile models that encompass their structural complexity while mimicking their mechanical features. In this study, we present a candidate model inspired by histological measurements of the upper layers of human vocal folds. Bi-photonic observations were used to quantify the distribution, orientation, width, and volume fraction of collagen and elastin fibers between histological layers. Using established biomaterials, polymer fiber-reinforced hydrogels were developed to replicate the fibrillar network and ground substance of native vocal fold tissue. To achieve this, jet-sprayed poly(ε-caprolactone) fibrillar mats were successfully impregnated with poly(L-lysine) dendrimers/polyethylene glycol hydrogels. The resulting composites exhibited versatile structural, physical and mechanical properties that could be customized through variations in the chemical formulation of their hydrogel matrix, the microstructural architecture of their fibrous networks (i.e., fiber diameter, orientation and volume fraction) and their assembly process. By mimicking the collagen network of the lamina propria with polymer fibers and the elastin/ground substance with the hydrogel composition, we successfully replicated the non-linear, anisotropic, and viscoelastic mechanical behavior of the vocal-fold upper layers, accounting for inter/intra-individual variations. The development of this mimetic model offers promising avenues for a better understanding of the complex mechanisms involved in voice production. STATEMENT OF SIGNIFICANCE: Human vocal folds are outstanding vibrating soft living tissues allowing phonation. Simple physical models that take into account the histological structure of the vocal fold and recapitulate its mechanical features are scarce. As a result, the relations between tissue components, organisation and vibro-mechanical performances still remain an open question. We describe here the development and the characterization of fiber-reinforced hydrogels inspired from the vocal-fold microstructure. These systems are able to reproduce the mechanics of vocal-fold tissues upon realistic cyclic and large strains under various multi-axial loadings, thus providing a mimetic model to further understand the impact of the fibrous network microstructure in phonation.

An Euler-Bernoulli-type beam model of the vocal folds for describing curved and incomplete glottal closure patterns

Incomplete glottal closure is a laryngeal configuration wherein the glottis is not fully obstructed prior to phonation. It has been linked to inefficient voice production and voice disorders. Various incomplete glottal closure patterns can arise and the mechanisms driving them are not well understood. In this work, we introduce an Euler-Bernoulli composite beam vocal fold (VF) model that produces qualitatively similar incomplete glottal closure patterns as those observed in experimental and high-fidelity numerical studies, thus offering insights into the potential underlying physical mechanisms. Refined physiological insights are pursued by incorporating the beam model into a VF posturing model that embeds the five intrinsic laryngeal muscles. Analysis of the combined model shows that co-activating the lateral cricoarytenoid (LCA) and interarytenoid (IA) muscles without activating the thyroarytenoid (TA) muscle results in a bowed (convex) VF geometry with closure at the posterior margin only; this is primarily attributed to the reactive moments at the anterior VF margin. This bowed pattern can also arise during VF compression (due to extrinsic laryngeal muscle activation for example), wherein the internal moment induced passively by the TA muscle tissue is the predominant mechanism. On the other hand, activating the TA muscle without incorporating other adductory muscles results in anterior and mid-membranous glottal closure, a concave VF geometry, and a posterior glottal opening driven by internal moments induced by TA muscle activation. In the case of initial full glottal closure, the posterior cricoarytenoid (PCA) muscle activation cancels the adductory effects of the LCA and IA muscles, resulting in a concave VF geometry and posterior glottal opening. Furthermore, certain maneuvers involving co-activation of all adductory muscles result in an hourglass glottal shape due to a reactive moment at the anterior VF margin and moderate internal moment induced by TA muscle activation. These findings have implications regarding potential laryngeal maneuvers in patients with voice disorders involving imbalances or excessive tension in the laryngeal muscles such as muscle tension dysphonia.

Vocal fold restoration after scarring: biocompatibility and efficacy of an MSC-based bioequivalent

BACKGROUND

There is growing interest to application of regenerative medicine approaches in otorhinolaryngological practice, especially in the framework of the therapy of vocal fold (VF) scar lesions. The used conservative and surgical methods, despite the achieved positive outcomes, are frequently unpredictable and do not result in the restoration of the VF's lamina propria's structure, which provides the mechanical properties necessary for vibration. In this connection, the aim of this study was to ascertain the safety and efficacy of a bioequivalent in the treatment of VF scars using a rabbit model of chronic damage.

METHODS

The bioequivalent consisted of a hydrogel system based on a PEG-fibrin conjugate and human bone marrow-derived MSC. It was characterized and implanted heterotopically into rats and orthotopically into rabbits after VF scar excision.

RESULTS

We showed that the fabricated bioequivalent consisted of viable cells retaining their metabolic and proliferative activity. While being implanted heterotopically, it had induced the low inflammatory reaction in 7 days and was well tolerated. The orthotopic implantation showed that the gel application was characterized by a lower hemorrhage intensity (p = 0.03945). The intensity of stridor and respiratory rate between the groups in total and between separate groups had no statistically significant difference (p = 0.96 and p = 1; p = 0.9593 and p = 0.97…1, respectively). In 3 days post-implantation, MSC were detected only in the tissues closely surrounding the VF defect. The bioequivalent injection caused that the scar collagen fibers were packed looser and more frequently mutually parallel that is inherent in the native tissue (p = 0.018). In all experimental groups, the fibrous tissue's ingrowth in the adjacent exterior muscle tissue was observed; however, in Group 4 (PEG-Fibrin + MSC), it was much less pronounced than it was in Group 1 (normal saline) (p = 0.008). The difference between the thicknesses of the lamina propria in the control group and in Group 4 was not revealed to be statistically significant (p = 0.995). The Young's modulus of the VF after the bioequivalent implantation (1.15 ± 0.25 kPa) did not statistically significantly differ from the intact VF modulus (1.17 ± 0.45 kPa); therefore, the tissue properties in this group more closely resembled the intact VF.

CONCLUSIONS

The developed bioequivalent showed to be biocompatible and highly efficient in the restoration of VF's tissue.

Vocal Fold Vibration of the Whistle Register Observed by High-Speed Digital Imaging

INTRODUCTION

Singers use a whistle register to sing at a fundamental frequency above 1000 Hz. In previous studies, vocal fold vibrations with or without complete closure and partial vocal fold vibrations were observed depending on the subject. However, the production mechanism of the whistle register is not yet clearly understood because of the limitations of the imaging device for the glottis and subjects.

OBJECTIVES

This study aims to examine vocal fold vibrations in a whistle register.

METHODS

The dynamic behavior of the glottis was recorded for six singers (four females and two males) using a high-speed digital imaging device with a frame rate above 10,000 fps. Audio signals were recorded simultaneously. The data were analyzed in the form of topography, glottal area waveforms, spectrograms, and phonovibrography to examine spatiotemporal patterns of glottal motion.

RESULTS

The vibratory motion of the vocal folds was classified into six patterns. The first pattern was the entire vocal fold vibration with complete closure during the closed phase. The second to fifth was the entire vocal fold vibration without complete closure, where a gap was observed for the full length of the vocal folds for the second, at the posterior part of the glottis for the third, at the anterior for the fourth, and at both ends for the fifth. In the sixth pattern, the vocal folds vibrated partially. Our results support the previous findings on the vibration of the vocal folds. In addition, we identified novel vibratory patterns in the vocal folds.

CONCLUSION

We conclude that the production of the whistle register is not just an extension of the falsetto register to the higher fundamental-frequency region; rather, the production mechanism of the whistle register appeared to be diverse as a means of vocalization.

Reinke's Edema: New Insights into Voice Analysis, a Retrospective Study

PURPOSE

Reinke's edema (RE) is a pathological condition involving increased volume of the vocal folds and resulting in significant impact on speech, fundamental frequency, and vocal range. Literature reports few studies which analyze vocal features according to the severity of RE. The aims of this study were to investigate the aerodynamics, acoustic characteristics, and sound spectrograms of a group of RE patients and to assess whether there was any correlation with their endoscopic grading.

METHODS

A total of 98 patients were included in the study, 49 patients with RE and 49 healthy volunteers (HV). Multidimensional Voice Program was used to perform objective voice assessment. Maximum phonation time (MPT) and Voice Handicap Index (VHI) questionnaire were collected. The spectrograms of the vowel /a/ and of the word /aiuole/, which contains the five Italian vowels, of each patient were analyzed according to the classification of Yanaghiara modified by Ricci Maccarini and De Colle. Laryngological assessment was used to record vocal folds morphology according to Yonekawa's classification. Univariate analysis was used to compare group outcomes. Bivariate analysis was used to compare endoscopic grading and voice analysis results.

RESULTS

Univariate analysis of the HV and RE groups revealed statistically significant differences (P < 0.05) for the following parameters: jitter%, shimmer%, harmonic-to-noise ratio (NHR), voice turbulence index (VTI), MPT, VHI except for soft phonation index. Spearman's rank correlation showed a positive correlation between vocal parameters such as jitter%, shimmer%, NHR, VTI, and RE gradings. A negative correlation was found between MPT and RE gradings. Bivariate analysis indicated a strong positive correlation between RE grading and the spectrogram classification performed both with the vowel / a / (Rho 0.86; P = 0.0001) and with the word / aiuole / (Rho 0.81; P = 0.0001).

CONCLUSION

The present study demonstrates that patients with RE have different voice characteristics compared to HV. In particular, the voice analysis highlighted acoustic parameters that correlated to differing degrees of RE. In addition, spectrogram analysis should be considered for acoustic assessments before and after medical and surgical therapy and also in forensic medicine.

Correlation Between Laryngoscopic Appearance and Histopathology in Vocal Fold Cysts

OBJECTIVES/HYPOTHESIS

Cysts are benign vocal fold lesions typically divided into mucous retention or epidermoid subtypes. The conventional paradigm that the former are translucent and the latter opaque fails to encompass the heterogeneity of cyst appearance on laryngoscopy. This study aims to characterize the relationships between clinical cyst characteristics and histopathology.

STUDY DESIGN

Retrospective cohort METHODS: Clinicodemographic data, videostroboscopy findings, and histopathology results were retrospectively reviewed for adults who underwent surgical excision of vocal fold cysts at our institution between 2006 and 2021.

RESULTS

Diagnostic histopathologic material was available for 69 patients (age: 50.4 ± 15.1 years, 68.1% female). Clinically, most cysts were opaque (69.6%) and located at the vibratory margin (82.6%). 11.6% were infraglottic. Significant associations existed between cyst location and epithelial type, with infraglottic cysts and those at the superior surface more commonly exhibiting ductal (P = 0.003) and squamous (P = 0.002) epithelium, respectively. Cyst opacity did not correlate with histopathology (P = 0.415). Epidermoid cysts were more likely to exhibit clinical inflammation (P = 0.002).

CONCLUSIONS

Singing more, singing harsher: occurrence of nonlinear phenomena in a primate' song

Nonlinear phenomena (NLP) in animal vocalizations arise from irregularities in the oscillation of the vocal folds. Various non-mutually exclusive hypotheses have been put forward to explain the occurrence of NLP, from adaptive to physiological ones. Non-human primates often display NLP in their vocalizations, yet the communicative role of these features, if any, is still unclear. We here investigate the occurrence of NLP in the song of a singing primate, the indri (Indri indri), testing for the effect of sex, age, season, and duration of the vocal display on their emission. Our results show that NLP occurrence in indri depends on phonation, i.e., the cumulative duration of all the units emitted by an individual, and that NLP have higher probability to be emitted in the later stages of the song, probably due to the fatigue indris may experience while singing. Furthermore, NLP happen earlier in the vocal display of adult females than in that of the adult males, and this is probably due to the fact that fatigue occurs earlier in the former because of a greater contribution within the song. Our findings suggest, therefore, that indris may be subjected to physiological constraints during the singing process which may impair the production of harmonic sounds. However, indris may still benefit from emitting NLP by strengthening the loudness of their signals for better advertising their presence to the neighboring conspecific groups.

A Prospective Observational Study to Determine the Added Clinical Value of Videokymography to Videostroboscopy in Patients with Change in Voice

Videolaryngostroboscopy (VLS) is considered gold standard method for assessing voice disorders. But patients with irregular waveform of vocal folds cannot benefit from the VLS. Videokymography [VKG] is a single line real time, high speed imaging technique. It detects voice disorders based on vocal fold vibration characteristics whether the vibrations are regular or irregular. There is no standard clinical protocol or evidence on the clinical relevance of VKG for functional assessment of voice disorders. Since mechanism of voice production depends on vibration characteristics, VKG imaging leads to new possibilities for diagnosis, objective documentation and monitoring of vocal fold behavior in clinical practice in case of voice disorders. This study aims to evaluate clinical value of VKG in addition to VLS as a complementary tool for the assessment of voice disorder.

Efficacy of the DoctorVox Voice Therapy Technique for the Management of Vocal Fold Nodules

Objective

Vocal fold nodules (VFNs) are among the most common causes of dysphonia. Phono-laryngeal microsurgery, pharmacological treatments, and voice therapy (VT) have been used for treating VFNs. VT has been advocated as the primary treatment of choice. This study investigated the efficacy of the DoctorVox Voice therapy technique (DVT) for treating VFNs.

Methods

A total of 38 patients with VFNs and 40 individuals without any voice problem (control group) were included. All patients received the DVT program. Otorhinolaryngology examination, videolaryngostroboscopy (VLS), and acoustic analysis (SPL, mean F0, jitter %, shimmer %, NHR) were performed at pretreatment, one and six months after the end of treatment. The voice handicap index-10 (VHI-10) and the GRB scales were used for perceptual voice evaluation. GRB and VLS scorings were done blindly.

Results

Compared with the pretreatment values, the first- and the sixth-month values after treatment demonstrated a significant decrease in VHI-10 (19.5 vs. 5.1), GRB (2.3 vs 0.68 for G value) and VLS scores, SPL (54.4 vs 66.1 dB), F0 (201 vs. 227 Hz), jitter % (1.46 vs 0.85), shimmer % (3.27 vs 2.51), NHR (1.15 vs. 0.46) values among patients. Most of the voice parameters in the sixth month after the DVT program did not differ significantly from those of the control group.

Conclusion

The DVT was found to be an effective method in VFN treatment.

Hydration State and Hyaluronidase Treatment Significantly Affect Porcine Vocal Fold Biomechanics

OBJECTIVES

The understanding of vocal fold hydration state, including dehydrated, euhydrated, rehydrated tissue, and how hydration affects vocal fold biomechanical properties is still evolving. Although clinical observations support the benefits of increasing vocal fold hydration after dehydrating events, more mechanistic information on the effects of vocal fold dehydration and the beneficial effects of rehydration are needed. Alterations to hyaluronic acid (HA), an important component of the vocal fold extracellular matrix, are likely to influence the biomechanical properties of vocal folds. In this study, we investigated the influence of hydration state and HA on vocal fold tissue stiffness via biomechanical testing.

STUDY DESIGN

Prospective, ex vivo study design.

METHODS

Fresh porcine vocal folds (N = 18) were examined following sequential immersion in hypertonic (dehydration) and isotonic solutions (rehydration). In a separate experiment, vocal folds were incubated in hyaluronidase (Hyal) to remove HA. Control tissues were not exposed to any challenges. A custom micromechanical system with a microforce sensing probe was used to measure the force-displacement response. Optical strain was calculated, and ultrasound imaging was used to measure tissue cross-sectional area to obtain stress-strain curves.

RESULTS

Significant increases (P ≤ 0.05) were found in tangent moduli between dehydrated and rehydrated vocal folds at strains of ε = 0.15. The tangent moduli of Hyal-digested tissues significantly increased at both ε = 0.15 and 0.3 (P ≤ 0.05).

CONCLUSION

Vocal fold dehydration increased tissue stiffness and rehydration reduced the stiffness. Loss of HA increased vocal fold stiffness, suggesting a potential mechanical role for HA in euhydrated vocal folds.

Examining the influence of epithelium layer modeling approaches on vocal fold kinematics and kinetics

Grouping the thin epithelium and thicker superficial lamina propria layers into a single cover layer has been widely adopted in finite element vocal fold models. Recent silicone vocal fold studies have suggested, however, that inclusion of a distinct epithelial layer leads to more physiologically representative motion. This study systematically explores the ramifications of incorporating an epithelial layer into a cover grouping for finite element vocal fold modeling. A membrane model for the epithelium is introduced to facilitate parametric investigation by reducing the mesh density requirement of the epithelium into a single infinitesimally thin layer. Excluding the epithelium entirely leads to increased energy in higher order modes and larger inferior-superior excursion of the folds. Integrating the epithelium into a cover layer with volume-weighted average stiffness results in similar kinematics to that of a model treating the epithelium as a distinct layer. However, the internal stress/strain and contact pressure during collision are higher, and viscous dissipation is lower, when the epithelium is integrated into the cover. Thus, careful treatment of the epithelium is recommended for finite element studies, particularly when employing the models for estimating measures dependent upon internal stress/strain and/or collision pressure, such as vocal dose.

Laryngeal Diadochokinesis in the Mandarin Population

INTRODUCTION

This study identifies the most suitable syllable for laryngeal diadochokinesis (LDDK) in Mandarin speakers.

METHODS

One hundred and ten Mandarin speakers aged 18-83 years were used in the study. LDDK was assessed using quick repetitions of /ʔe/, /ʔi/, /ʔa/, /he/, /ha/, and /hi/. The observation index included the average rate (syllable/s) and regularity (%).

RESULTS

In the various age groups, there was no significant difference in LDDK rate and regularity of adducted syllables (p > 0.05), and only the regularity of /ʔi/ is significantly different between aged 18-40 and 41-64 years (p = 0.040). When vocal fold adduction was compared between various syllables, there was no significant difference in LDDK rate and regularity (p > 0.05). In various age groups, the LDDK rate of abduction syllables is different (p < 0.05) compared with the LDDK regularity of abduction syllables (p > 0.05). In various abduction syllables, there is no difference in LDDK rate (p > 0.05); however, /ha/ and /hi/ have significant differences in LDDK regularity (p = 0.007).

CONCLUSION

According to the preliminary data, /ʔa/ and /ha/ can be used as suitable indicators to analyse the coordination ability of the laryngeal movement of Mandarin speakers.

Membranous Vocal Fold Lesions in Patients With Chronic Cough: A Case Series

OBJECTIVES

Trauma related to chronic cough and forceful glottal closure has been associated with lesions of the vocal process; however, there is limited description of cough leading to membranous vocal fold lesions. We present a series of mid-membranous vocal fold lesions in a cohort of patients with chronic cough, with a proposed mechanism of lesion formation.

METHODS

Patients treated for chronic cough with membranous vocal fold lesions affecting phonation were identified. Presentation, diagnosis, treatment strategies (behavioral, medical, and surgical), patient-reported outcome measures (PROMs), and videostroboscopy were reviewed.

RESULTS

Five patients are included (four females, one male, aged 56±16 years). Mean cough duration was 2.6±3.5 years. All patients were on acid suppressive medications for existing gastroesophageal reflux disease (GERD) prior to referral. All lesions were identified at the mid-membranous vocal folds and morphologically encompassed a wound healing spectrum between ulceration and/or granulation tissue (granuloma) formation. Patients were treated in an interdisciplinary fashion with behavioral cough suppression therapy, superior laryngeal nerve block, and neuromodulators. Three had persistent lesions requiring procedural intervention (one office-based steroid injection and two surgical excisions). At the completion of treatment, all five patients had improvement in Cough Severity Index with an average decrease of 15.2±4.8. All but one patient had improvement in their Voice Handicap Index-10 with an average decrease of 13.2±11.1. One patient undergoing surgical intervention was noted to have a persistent lesion on follow-up.

CONCLUSION

Mid-membranous vocal fold lesions in patients with chronic cough are uncommon. When they do occur, they represent epithelial change arising in context of shear injury and are distinct from phonotraumatic lesions in the lamina propria. An interdisciplinary approach including behavioral cough suppression therapy, neuromodulators, superior laryngeal nerve block, and acid suppression are reasonable for initial management, reserving surgical intervention for refractory lesions once the inciting source of injury has been controlled.

A 6-Year Retrospective Study of the Demographics of Glottic Keratosis in a Tertiary Care Voice Centre

Since Keratosis may be accompanied with severe dysplasia or malignancy; early management of this condition is of essence. However, since this condition has a high rate of recurrence the surgical dilemma remains as to how frequently the surgeries should be performed and what should be the factors to guide this decision. The objectives of our study are to attempt to understand the demographics of laryngeal keratosis and its behaviour pattern including the potential to recur, disease upstaging and malignant transformation. This is a 6-year retrospective study of patients presenting to a Voice and Swallowing Centre. All patients had been operated upon and confirmed to have keratosis with or without cancer. The medical records and stroboscopy videos were reviewed for details such as age, gender, history of smoking, laterality of lesion, location of lesion on the vocal fold, recurrence with any disease upstaging or malignant transformation. In the case of recurrence of lesion the histopathology of the recurrence was compared with the primary histopathology. Chi square test & Fisher's exact test was used for comparison of proportions between two groups. A total of 71 patients were included in the study, 88% were males. Recurrence was seen in 20 patients (28%), 14 with benign recurrence and 6 with malignant. Rate of recurrence when the primary keratosis had been benign was 30.7 and 20.6% when the primary keratosis had been associated with malignancy. A majority of patients with glottic keratosis were males and all that underwent malignant transformation were males. The rate of postoperative recurrence when the primary keratosis had been benign was higher than when it had been keratosis associated with malignancy. This may indicate the need for aggressive surgical management for benign keratosis.

Support of deep learning to classify vocal fold images in flexible laryngoscopy

PURPOSE

To collect a dataset with adequate laryngoscopy images and identify the appearance of vocal folds and their lesions in flexible laryngoscopy images by objective deep learning models.

METHODS

We adopted a number of novel deep learning models to train and classify 4549 flexible laryngoscopy images as no vocal fold, normal vocal folds, and abnormal vocal folds. This could help these models recognize vocal folds and their lesions within these images. Ultimately, we made a comparison between the results of the state-of-the-art deep learning models, and another comparison of the results between the computer-aided classification system and ENT doctors.

RESULTS

This study exhibited the performance of the deep learning models by evaluating laryngoscopy images collected from 876 patients. The efficiency of the Xception model was higher and steadier than almost the rest of the models. The accuracy of no vocal fold, normal vocal folds, and vocal fold abnormalities on this model were 98.90 %, 97.36 %, and 96.26 %, respectively. Compared to our ENT doctors, the Xception model produced better results than a junior doctor and was near an expert.

CONCLUSION

Our results show that current deep learning models can classify vocal fold images well and effectively assist physicians in vocal fold identification and classification of normal or abnormal vocal folds.

Exploring the mechanics of fundamental frequency variation during phonation onset

Fundamental frequency patterns during phonation onset have received renewed interest due to their promising application in objective classification of normal and pathological voices. However, the associated underlying mechanisms producing the wide array of patterns observed in different phonetic contexts are not yet fully understood. Herein, we employ theoretical and numerical analyses in an effort to elucidate the potential mechanisms driving opposing frequency patterns for initial/isolated vowels versus vowels preceded by voiceless consonants. Utilizing deterministic lumped-mass oscillator models of the vocal folds, we systematically explore the roles of collision and muscle activation in the dynamics of phonation onset. We find that an increasing trend in fundamental frequency, as observed for initial/isolated vowels, arises naturally through a progressive increase in system stiffness as collision intensifies as onset progresses, without the need for time-varying vocal fold tension or changes in aerodynamic loading. In contrast, reduction in cricothyroid muscle activation during onset is required to generate the decrease in fundamental frequency observed for vowels preceded by voiceless consonants. For such phonetic contexts, our analysis shows that the magnitude of reduction in the cricothyroid muscle activation and the activation level of the thyroarytenoid muscle are potential factors underlying observed differences in (relative) fundamental frequency between speakers with healthy and hyperfunctional voices. This work highlights the roles of sometimes competing laryngeal factors in producing the complex array of observed fundamental frequency patterns during phonation onset.

Comparative proteomic changes in rabbit vocal folds undergoing systemic dehydration and systemic rehydration

BACKGROUND

A considerable body of clinical evidence suggests that systemic dehydration can negatively affect voice production, leading to the common recommendation to rehydrate. Evidence for the corrective benefits of rehydration, however, is limited with mixed conclusions, and biological data on the underlying tissue changes with rehydration is lacking. In this study, we used a rabbit model (n = 24) of acute (5 days) water restriction-induced systemic dehydration with subsequent rehydration (3 days) to explore the protein-level changes underlying the molecular transition from euhydration to dehydration and following rehydration using LC-MS/MS protein quantification in the vocal folds. We show that 5-day water restriction led to an average 4.3% decrease in body weight with relative increases in anion gap, Cl-, creatinine, Na+, and relative decreases in BUN, iCa2+, K+, and tCO2 compared to control (euhydrated) animals. A total of 309 differentially regulated (p < 0.05) proteins were identified between the Control and Dehydration groups. We observed a noteworthy similarity between the Dehydration and Rehydration groups, both well differentiated from the Control group, highlighting the distinct timelines of resolution of the clinical symptoms of systemic dehydration and the underlying molecular changes.

SIGNIFICANCE

Voice disorders are a ubiquitous problem with considerable economic and psychological impact. Maintenance of proper hydration is commonly prescribed as a general vocal hygiene practice. There is evidence that dehydration negatively impacts phonation, but our understanding of the state of vocal folds in the context of systemic dehydration are limited, particular from a molecular perspective. Further, ours is a novel molecular study of the short-term impact of rehydration on the tissue. Given the relatively minimal difference in vocal fold proteomic profiles between the Dehydration and Rehydration groups, our data demonstrate a complex physiological response to acute systemic dehydration, and highlight the importance of considering persistent underlying molecular pathology despite the rapid resolution of clinical measures. This study sets a foundation for future research to confirm the nature of potential beneficial outcomes of clinical recommendations related to hydration.

Quasi-static ultrasound elastography of ex-vivo porcine vocal folds during passive elongation and adduction

OBJECTIVES

The elastic properties of the vocal folds have great influence on the primary sound and thus on the entire subsequent phonation process. Muscle contractions in the larynx can alter the elastic properties of the vocal fold tissue. Quasi-static ultrasound elastography is a non-destructive examination method that can be applied to ex-vivo vocal folds. In this work, porcine vocal folds were passively elongated and adducted and the changes of the elastic properties due to that manipulations were measured.

METHODS

Manipulations were performed by applying force to sewn-in sutures. Elongation was achieved by a suture attached to the thyroid cartilage, which was pulled forward by defined weights. Adduction was effected by two sutures exerting torque on the arytenoid cartilage. A series of ten specimens was examined and evaluated using a quasi-static elastography algorithm. In addition, the surface stretch was measured optically using tattooed reference points.

RESULTS

This study showed that the expected stiffening of the tissue during the manipulations can be measured using quasi-static ultrasound elastography. The measured effect of elongation and adduction, both of which result in stretching of the tissue, is stiffening. However, the relative change of specific manipulations is not the same for the same load on different larynges, but is rather related to stretch caused and other uninvestigated factors.

CONCLUSION

The passive elongation and adduction of vocal folds stiffen the tissue of the vocal folds and can be measured using ultrasound elastography.

Proteomic analysis reveals that aging rabbit vocal folds are more vulnerable to changes caused by systemic dehydration

BACKGROUND

Older adults are more prone to develop systemic dehydration. Systemic dehydration has implications for vocal fold biology by affecting gene and protein expression. The objective of this study was to quantify vocal fold protein changes between two age groups and hydration status, and to investigate the interaction of age and hydration status on protein expression, which has not been investigated in the context of vocal folds before. Comparative proteomics was used to analyze the vocal fold proteome of 6.5-month-old and > 3-year-old rabbits subjected to water ad libitum or water volume restriction protocol.

RESULTS

Young and older adult rabbits (n = 22) were either euhydrated (water ad libitum) or dehydrated by water volume restriction. Dehydration was confirmed by body weight loss of - 5.4% and - 4.6% in young and older groups, respectively, and a 1.7-fold increase of kidney renin gene expression in the young rabbits. LC-MS/MS identified 2286 proteins in the rabbit vocal folds of young and older adult rabbits combined. Of these, 177, 169, and 81 proteins were significantly (p ≤ 0.05) affected by age, hydration status, or the interaction of both factors, respectively. Analysis of the interaction effect revealed 32 proteins with opposite change patterns after dehydration between older and young rabbit vocal folds, while 31 proteins were differentially regulated only in the older adult rabbits and ten only in the young rabbits in response to systemic dehydration. The magnitude of changes for either up or downregulated proteins was higher in the older rabbits. These proteins are predominantly related to structural components of the extracellular matrix and muscle layer, suggesting a disturbance in the viscoelastic properties of aging vocal fold tissue, especially when subjected to systemic dehydration.

CONCLUSIONS

Water restriction is a laboratory protocol to assess systemic dehydration-related changes in the vocal fold tissue that is translatable to human subjects. Our findings showed a higher number of proteins differentially regulated with a greater magnitude of change in the vocal folds of older adult rabbits in the presence of systemic dehydration compared to younger rabbits. The association of these proteins with vocal fold structure and biomechanical properties suggests that older human subjects may be more vulnerable to the effects of systemic dehydration on vocal function. The clinical implications of these protein changes warrant more investigation, but age should be taken into consideration when evaluating vocal treatment recommendations that interfere with body fluid balance.

Factors Associated With Injury to Recurrent Laryngeal Nerve in Patients Undergoing Surgery for Thyroid Cancer: A Single-centre Study Using Translaryngeal Ultrasound

AIMS

Intraoperative injury to the recurrent laryngeal nerve (RLN) is a serious complication occurring more frequently in patients with thyroid cancer than in those with benign thyroid diseases. However, data on the risk factors for RLN injury among patients with thyroid cancer are scarce. Currently, RLN injury is diagnosed by laryngoscopy, but translaryngealultrasonography (TLUS), which is less invasive, appears to have a similar accuracy. Herein, we analysed risk factors ofintraoperative RLN injury in patients with thyroid cancer and assessed the diagnostic performance of TLUS.

PATIENTS AND METHODS

In this prospective study, we enrolled patients undergoing surgery for thyroid cancer from October 2020 to October 2021. Medical and surgical variables were analysed as risk factors of RLN injury. TLUS was compared with laryngoscopy in diagnosing RLN injury.

RESULTS

There were 185 patients who underwent 196 surgeries. Of all surgeries, 23 (11.7%) caused RLN injury ascertained on laryngoscopy. Compared with laryngoscopy, TLUS displayed high sensitivity (97.7%; 95%CI: 94.3%-99.4%) and specificity (100%; 95% CI: 82.4%-100%). Before surgery, medical and surgical characteristics did not differ significantly between patients with or without RLN injury, but RLN entrapment by tumour was more frequent in those with the injury (P < 0.001). The risk of RLN injury was increased in patients undergoing thyroidectomy with lateral neck dissection (OR = 4.53; 95% CI: 1.29-14.32) and in those with lymph node metastases (OR = 2.76; 95% CI: 1.03-7.01).

CONCLUSION

Intraoperative RLN injury in patients with thyroid cancer is more common after operations requiringgreater resections and with lymph node involvement. TLUS could be used to diagnose RLN injury.

Stem cell therapy for vocal fold regeneration after scarring: a review of experimental approaches

This review aims at becoming a guide which will help to plan the experimental design and to choose adequate methods to assess the outcomes when testing cell-based products in the treatment of the damaged vocal folds. The requirements to preclinical trials of cell-based products remain rather hazy and dictated by the country regulations. Most parameters like the way the cells are administered, selection of the cell source, selection of a carrier, and design of in vivo studies are decided upon by each research team and may differ essentially between studies. The review covers the methodological aspects of preclinical studies such as experimental models, characterization of cell products, assessment of the study outcome using molecular, morphological and immunohistochemical analyses, as well as measuring the tissue physical properties. The unified recommendations to perform preclinical trials could significantly facilitate the translation of cell-based products into the clinical practice.

Advances in Organ Preservation for Laryngeal Cancer

OPINION STATEMENT

At the University of Wisconsin, all treatment of head and neck cancer patients begins with discussion at our multi-disciplinary tumor board. Most patients with T4 disease, with existing laryngeal dysfunction, considered unlikely to complete definitive CRT or who have a high risk of persistent aspiration after non-operative management undergo total laryngectomy. A laryngeal sparing approach is attempted on most other patients. Radiotherapy is delivered over 6.5 weeks, preferably with concurrent weekly cisplatin. If the patient is hesitant of chemotherapy or has contraindications to cisplatin, concurrent cetuximab may be offered. Patients treated with RT alone are often treated to the same dose, but via an accelerated schedule by adding a 6th fraction per week. The 6th fraction is given by delivering two treatments at least 6 h apart on a weekday of the patient's choosing. We consider the following to be major risk factors for clinically significant weight loss during treatment: a 10% or greater loss of weight in the 6 months prior to starting treatment, delivery of concurrent cisplatin, and treatment of the bilateral neck with radiation. Patients who have 2-3 of these characteristics are often given gastrostomy tubes prophylactically. Patients are seen 2 weeks after completion of therapy, and then every 3 months after completion for 2 years. A CT neck and PET-CT are performed at the first 3-month visit. They are seen twice in year three, and then yearly until years 5-7. At each of these visits, we have a low threshold to present the patient at our multidisciplinary tumor board for consideration of salvage laryngectomy if there are signs of progression.

Furosemide-induced systemic dehydration alters the proteome of rabbit vocal folds

Whole-body dehydration (i.e., systemic dehydration) leads to vocal fold tissue dehydration. Furosemide, a common diuretic prescribed to treat hypertension and edema-associated conditions, induces systemic dehydration. Furosemide also causes voice changes in human speakers, making this method of systemic dehydration particularly interesting for vocal fold dehydration studies. Our objective was to obtain a comprehensive proteome of vocal folds following furosemide-induced systemic dehydration. New Zealand White rabbits were used as the animal model and randomly assigned to euhydrated (control) or furosemide-dehydrated groups. Systemic dehydration, induced by injectable furosemide, was verified by an average body weight loss of -5.5% and significant percentage changes in blood analytes in the dehydrated rabbits compared to controls. Vocal fold specimens, including mucosa and muscle, were processed for proteomic analysis using label-free quantitation LC-MS/MS. Over 1600 proteins were successfully identified across all vocal fold samples; and associated with a variety of cellular components and ubiquitous cell functions. Protein levels were compared between groups showing 32 proteins differentially regulated (p ≤ 0.05) in the dehydrated vocal folds. These are mainly involved with mitochondrial translation and metabolism. The downregulation of proteins involved in mitochondrial metabolism in the vocal folds suggests a mechanism to prevent oxidative stress associated with systemic dehydration. SIGNIFICANCE: Voice disorders affect different population demographics worldwide with one in 13 adults in the United States reporting voice problems annually. Vocal fold systemic hydration is clinically recognized for preventing and treating voice problems and depends on optimal body hydration primarily achieved by water intake. Herein, we use the rabbit as a translatable animal model, and furosemide as a translatable method of systemic dehydration, to reveal a comprehensive proteomic profile of vocal fold mucosa and muscle in response to systemic dehydration. The significant subset of proteins differentially regulated due to furosemide-induced dehydration offer novel insights into the molecular mechanisms of systemic dehydration in the vocal folds. These findings also deepen our understanding of changes to tissue biology after diuretic administration.

Excised human larynx in N-vinyl-2-pyrrolidone-embalmed cadavers can produce voiced sound by pliable vocal fold vibration

Tissue-hardening effect and health-hazard issue of formaldehyde (FA) have long been a great disadvantage of this conventional fixative in anatomical research. We recently developed a FA-free embalming method for cadavers which utilizes N-vinyl-2-pyrrolidone (NVP) and enables assessment of motion kinetics by maintaining the softness of embalmed tissue. By assessing the feasibility of NVP-embalmed tissue to mimic vocalization, this study aimed to prove the potential of embalmed cadavers, which have previously been used only for the understanding of anatomical morphology, for the assessment of precise motion physiology in the human body. Ten cadavers embalmed in NVP (n = 6) and FA (n = 4) were incorporated in this study. Excised larynges underwent experimental phonation to mimic vocalization with fast and pliable vibration of vocal folds. High-speed digital imaging was utilized for the assessment of vocal fold vibration. Furthermore, acoustic analysis of the voiced sound, and reproducibility examination were also performed. Regular vocal fold vibrations successfully produced voiced sounds during experimental phonation using NVP-embalmed larynges. The vibratory frequency, vibration amplitude, and stretch rate of the vocal folds were comparable to those of living humans. Six months after the first experiment, the vocal parameters were reproduced, to suggest the long-term preservation potential of our NVP-embalming technique. On the other hand, neither voiced sound nor vocal fold vibration were observed in FA-embalmed larynges. This novel embalming technique could pioneer the next era to utilize embalmed cadavers for the examination of motion physiology in the human body.

Piezo1-expressing vocal fold epithelia modulate remodeling via effects on self-renewal and cytokeratin differentiation

Mechanoreceptors are implicated as functional afferents within mucosa of the airways and the recent discovery of mechanosensitive channels Piezo1 and Piezo2 has proved essential for cells of various mechanically sensitive tissues. However, the role for Piezo1/2 in vocal fold (VF) mucosal epithelia, a cell that withstands excessive biomechanical insult, remains unknown. The purpose of this study was to test the hypothesis that Piezo1 is required for VF mucosal repair pathways of epithelial cell injury. Utilizing a sonic hedgehog (shh) Cre line for epithelial-specific ablation of Piezo1/2 mechanoreceptors, we investigated 6wk adult VF mucosa following naphthalene exposure for repair strategies at 1, 3, 7 and 14 days post-injury (dpi). PIEZO1 localized to differentiated apical epithelia and was paramount for epithelial remodeling events. Injury to wildtype epithelium was most appreciated at 3 dpi. Shh^cre/+; Piezo1^loxP/loxP, Piezo2 ^loxP/+ mutant epithelium exhibited severe cell/nuclear defects compared to injured controls. Conditional ablation of Piezo1 and/or Piezo2 to uninjured VF epithelium did not result in abnormal phenotypes across P0, P15 and 6wk postnatal stages compared to heterozygote and control tissue. Results demonstrate a role for Piezo1-expressing VF epithelia in regulating self-renewal via effects on p63 transcription and YAP subcellular translocation-altering cytokeratin differentiation.

Development and validation of a 3D laryngeal model in surgical skills training

OBJECTIVE

To present and validate a new simulation model for endoscopic phonomicrosurgery training as an improved teaching method.

METHODS

A low-cost artificial model was assembled using 3D printing, silicone, and gelatin. The study was designed to test the model's ability to carry out training and teaching of endoscopic phonomicrosurgery. The synthetic model was built to simulate normal and pathological vocal folds such as polyps, intracordal cysts and keratoses, made of silicone and gelatin and embedded in a larynx framework made by 3D printing. Simulations of endoscopic surgical procedures were performed and documented through photographs and videos and the images were submitted to the evaluation of a group of 17 otorhinolaryngologists who used a Likert scale questionnaire. The responses were submitted to an agreement analysis using the sum of the scores obtained for the responses as an appropriate level of validation. Cronbach's alpha index was calculated to measure the degree of the questionnaire internal consistency.

RESULT

The evaluations indicated maximum approval for the model adequacy for use in practical classes and for the teaching of the procedures, as well as in the overall satisfaction with the model in the use of surgical training.

CONCLUSION

The present proposal for training laryngeal endoscopic surgery in a 3D synthetic model is a viable option according to the validation methodology used in the present study.

Embedded 3D printing of multi-layer, self-oscillating vocal fold models

The biomechanics of human voice production are commonly studied using benchtop silicone vocal fold models that mimic the vibration of their in vivo counterparts. These models often have multiple layers of differing stiffness that represent human vocal fold tissue layers and are fabricated using a multi-step casting process. The purpose of the present study is to introduce and demonstrate a process for fabricating functional multi-layer vocal fold models using an alternative approach, termed embedded 3D printing, that is a hybrid of casting and 3D printing. In this paper the fabrication process is described. Analysis of the resulting geometric and stiffness characteristics of the layers, including layer elastic modulus values ranging from less than 1 kPa to approximately 40 kPa, is presented. The results of tests demonstrating that the models are capable of sustained phonomimetic vibration are given. Capabilities and limitations of the embedded 3D printing process are discussed. It is concluded that the process has the potential to contribute to voice biomechanics research by facilitating prospective improvements in the fabrication, design, and functionality of multi-layer vocal fold models.

RNA sequencing identifies transcriptional changes in the rabbit larynx in response to low humidity challenge

BACKGROUND

Voice disorders are a worldwide problem impacting human health, particularly for occupational voice users. Avoidance of surface dehydration is commonly prescribed as a protective factor against the development of dysphonia. The available literature inconclusively supports this practice and a biological mechanism for how surface dehydration of the laryngeal tissue affects voice has not been described. In this study, we used an in vivo male New Zealand white rabbit model to elucidate biological changes based on gene expression within the vocal folds from surface dehydration. Surface dehydration was induced by exposure to low humidity air (18.6% + 4.3%) for 8 h. Exposure to moderate humidity (43.0% + 4.3%) served as the control condition. Ilumina-based RNA sequencing was performed and used for transcriptome analysis with validation by RT-qPCR.

RESULTS

There were 103 statistically significant differentially expressed genes identified through Cuffdiff with 61 genes meeting significance by both false discovery rate and fold change. Functional annotation enrichment and predicted protein interaction mapping showed enrichment of various loci, including cellular stress and inflammatory response, ciliary function, and keratinocyte development. Eight genes were selected for RT-qPCR validation. Matrix metalloproteinase 12 (MMP12) and macrophage cationic peptide 1 (MCP1) were significantly upregulated and an epithelial chloride channel protein (ECCP) was significantly downregulated after surface dehydration by RNA-Seq and RT-qPCR. Suprabasin (SPBN) and zinc activated cationic channel (ZACN) were marginally, but non-significantly down- and upregulated as evidenced by RT-qPCR, respectively.

CONCLUSIONS

The data together support the notion that surface dehydration induces physiological changes in the vocal folds and justifies targeted analysis to further explore the underlying biology of compensatory fluid/ion flux and inflammatory mediators in response to airway surface dehydration.

Sectorial Analysis of the Fibrous Matrix of Vocal Folds in the Elderly

OBJECTIVE

to determine the sectorial concentration of fibrous matrix along the vocal folds of the elderly.

METHODS

Thirteen fresh vocal folds were removed from 13 cadavers. The subjects were divided into two groups: control group (CG) - age range 25-40 years (n = 5), and elderly group (EG), aged ≥70 years (n-8). The vocal folds were separated according to regions in: anterior macula flava (AMF), posterior macula flava (PMF), medial region (M) and lateral region of the membranous vocal fold (L). The material was examined using a scanning electron microscope and 10 pictures per region were obtained at 1200x magnification. The area of fibrous matrix was quantified in both groups using the AVSOFT Biovew Program.

RESULTS

Percentage (%) of fibrous matrix per region (%): AMF (EG = 86.78%; CG = 81.63%); PMF (EG = 88.19%; CG = 81.52%); M (EG = 84.92%; CG = 77.96%); L (EG = 83.93%; CG = 78.91%). Irregular distribution of a dense fibrous matrix was also more evident in the elderly's larynges in a qualitative assessments.

CONCLUSION

A higher concentration of fibrous matrix was observed in the vocal folds of the elderly when compared to the control at all the studied regions. The greatest increase in the concentration of fibers in the medial portion of the body of the vocal folds is probably due to the phonatory stimulation. The macula flava remains functional even in the senile larynx.

Mechanics of human vocal folds layers during finite strains in tension, compression and shear

During phonation, human vocal fold tissues are subjected to combined tension, compression and shear loading modes from small to large finite strains. Their mechanical behaviour is however still not well understood. Herein, we complete the existing mechanical database of these soft tissues, by characterising, for the first time, the cyclic and finite strains behaviour of the lamina propria and vocalis layers under these loading modes. To minimise the inter or intra-individual variability, particular attention was paid to subject each tissue sample successively to the three loadings. A non-linear mechanical behaviour is observed for all loading modes: a J-shape strain stiffening in longitudinal tension and transverse compression, albeit far less pronounced in shear, stress accommodation and stress hysteresis whatever the loading mode. In addition, recorded stress levels during longitudinal tension are much higher for the lamina propria than for the vocalis. Conversely, the responses of the lamina propria and the vocalis in transverse compression as well as transverse and longitudinal shears are of the same orders of magnitude. We also highlight the strain rate sensitivity of the tissues, as well as their anisotropic properties.

Commentary about mesenchymal stem cells and scarred vocal folds

A commentary to “Hertegård, S., Nagubothu, S.R., Malmström, E. et al. Treatment of vocal fold scarring with autologous bone marrow-derived human mesenchymal stromal cells - first phase I/II human clinical study. Stem Cell Res Ther 11, 128 (2020)” concerning the surgical intervention including a scar resection, the use of the Voice Handicap Index, the surgical and regulatory points of view regarding the inclusion of patients with laryngeal carcinomas history, and the side effects of bone marrow harvesting.

Comparative Study Between Conventional Microlaryngeal Surgery and Carbon Dioxide Laser in Management of Minimal Associated Pathological Lesions of Vocal Folds

The aim of this study is to compare the relatively new CO₂ laser microlaryngeal surgery and conventional cold dissection method in treatment of minimal associated pathological lesions of vocal folds. Eighty patients aged 20-70 years old were randomly divided into two groups, group A (40 patients) was treated by the conventional method and group B (40 patients) was treated with CO₂ laser microlaryngeal surgery. Assessment procedures included GRBAS scale, stroboscopic examination, and Arabic version of voice handicap index. Results stated that improvement of quality of voice after surgery in both techniques had no significant difference. The significant difference was in operative time and bleeding because laser had less time and bleeding. Both techniques had no recurrence within 3-months follow-up.

Quantification of the Intraglottal Pressure Induced by Flow Separation Vortices Using Large Eddy Simulation

The greatest rate of change in the glottal flow rate during phonation is a rapid decrease that occurs during the latter part of the glottal closing. Previous works showed that intraglottal flow separation vortices form in a divergent glottis, produce negative gauge pressures (below atmospheric) during closing. It is hypothesized here that flow separation vortices contribute to the rapid closing mechanism of the true vocal folds during phonation. Four idealized static models (M5) of the human larynx were investigated using large eddy simulation: 2 models featured parallel folds that did not enable flow separation in the glottis and 2 models involved a divergent glottis. The influence of the ventricular gap (narrow/wide) is evaluated. An unsteady pressure inlet representing a voicing cycle was applied to the sub-glottal region to mimic the time-varying glottal flow. Intraglottal vortex structures formed downstream of the separation point in a divergent glottis. Their existence caused a higher closing force that was applied onto the vocal folds. A narrow ventricular gap strengthens this effect. Strength of the intraglottal vortices increased with the maximum flow declination rate. Therefore, a more divergent shape of the glottis during glottal closing will be one of the main contributors to the voice quality.

Vocal-fold leukoplakia and dysplasia. Mini-review by the French Society of Phoniatrics and Laryngology (SFPL)

Vocal-fold leukoplakia and dysplasia are together designated "epithelial hyperplastic laryngeal lesions" (EHLL). Work-up and follow-up are founded on optical examination with high-definition imaging, stroboscopy and narrow-band imaging. Diagnosis is based on pathology, using the new 2017 WHO classification, dichotomizing "low grade" and "high grade". Statistically, the risk of cancerous progression is 20% within 5 to 10 years of diagnosis, or more in over-65 year-old males; risk for any given patient, however, is unpredictable. Research focuses on the genetic criteria of the lesion and characterization of the tumoral microenvironment. Treatment is exclusively microsurgical. Resection depth is adjusted according to infiltration. EHLL is a chronic disease, necessitating long-term follow-up, which may be hampered by residual dysphonia and surgical sequelae in the vocal folds. Sequelae need to be minimized by good mastery of microsurgical technique and indications. When they occur, biomaterials such as autologous fat and hyaluronic acid can be useful. Tissue bio-engineering is a promising field.

Lipoma of the Larynx and Other Differential Diagnoses

Fatty lesions in the head and neck region are uncommon but can present in any subsite, including rarely the larynx. Most commonly, the fatty lesion is a benign lipoma and an incidental finding as in this case. However, the lesion must be differentiated from other fatty lesions such as liposarcoma, lipoblastoma, and hibernoma. Accurate diagnosis on imaging can prevent unnecessary biopsy and more importantly worry for the patient. We report a case of an incidental lipoma within the vocal folds of the larynx.

Cigarette Smoke Exposure to Pig Larynx in an Inhalation Chamber

OBJECTIVES

This study investigated the effects of cigarette smoke exposure on the pig larynx using an inhalation chamber. Specifically, we compared the effects of cigarette smoke exposure from either 3 cigarettes per day (3cd) or 15 cigarettes per day (15cd) for 20 days.

STUDY DESIGN

In vivo prospective design.

METHODS

Female pigs were exposed via an inhalation chamber to cigarette smoke (3R4F research cigarettes) from 3cd (n = 6) or 15cd (n = 6) for 20 days. Outcomes included histopathology of vocal fold and airway tissues; gene expression of interleukins, TNF-α, and VEGF; protein levels of TNF-α and IL-6; and number of coughs recorded in the chamber.

RESULTS

Pigs exposed to cigarette smoke from 15cd exhibited mild vocal fold edema as compared to the 3cd group on histopathological evaluation. There was also minimal inflammation of nasal and tracheal tissue characterized by presence of more granulocytes in the 15cd group compared to the 3cd group. Cough frequency was significantly greater for the 15cd group compared to the 3cd group.

CONCLUSIONS

A custom-designed large animal inhalation chamber successfully challenged pigs repeatedly, to varying levels of cigarette smoke. Future studies will combine such low levels of smoke exposure with other common challenges such as acid reflux to understand the multifactorial causation of laryngeal pathologies.

Transient vocal fold lesion and hoarseness associated with the use of ramucirumab: Case report

INTRODUCTION

Gastric cancer (GC) is among the leading neoplasms with highest morbidity and mortality in the world. Tumor angiogenesis represents one of important targets of antineoplastic treatment, as it has an important role in cell development and growth.

CASE REPORT

Ramucirumab, an IgG1 monoclonal antibody (MoAb), inhibits the angiogenesis pathway by blocking the VEGFR-2 activation. The most common adverse events associated with angiogenic inhibitors are cardiovascular and healing disorders, such as systemic arterial hypertension (HTN), thromboembolism, bleeding, wound healing delay and fistulas. We report a case of vocal fold lesion associated with ramucirumab in a patient with metastatic gastric cancer. The patient presented with transient hoarseness that was related to the exposure to ramucirumab.

DISCUSSION

Laryngeal toxicity due to anti-angiogenic agents is rare. Despite the fact that this adverse event is not a life-threatening complication, it can significantly impair quality of life and should be promptly recognized.

Medial Surface Dynamics as a Function of Subglottal Pressure in a Canine Larynx Model

During vocal fold vibration, there may be a mucosal wave in the superior-inferior (vertical) direction, resulting in a convergent shape during opening and a divergent shape during closing. Most of our understanding of the converging/diverging shape of the glottis has come from studies in a hemilarynx model. Previous work has shown that vibratory patterns in the full excised larynx are different than the hemilarynx. This study characterized the dynamics of the medial glottal wall geometry during vibrations in the full excised canine larynx model. Using particle image velocimetry, the intraglottal geometry was measured at the midmembranous coronal plane in an excised canine larynx model. Measurements of the glottal area were taken simultaneously using high-speed imaging. The results show that skewing of the glottal area waveform occurs without the presence of a vocal tract and that the phase-lag of the superior edge relative to the inferior edge is smaller than reported and depends on the subglottal pressure. In addition, it shows that the glottal divergence angle during closing is proportional to the magnitude of the acoustic intensity and the intraglottal negative pressure. This preliminary data suggests that more studies are needed to determine the important mechanisms determining the relationship between intraglottal flow, intraglottal geometry, and acoustics.

Dehydration and Estrous Staging in the Rat Larynx: an in vivo Prospective Investigation

OBJECTIVE

This novel study sought to untangle the association between hydration state and the estrous cycle in the vocal folds, since the voice is reported to negatively change in speakers during the estrous cycle and with dehydration. We hypothesized that there would be alterations in vocal fold tissue morphology depending on hydration state and that these changes would vary with the estrous cycle.

STUDY DESIGN

Prospective, in vivo study design.

METHODS

Female Sprague Dawley rats (n = 30) were used in this study. Sixteen rats were systemically dehydrated to an average of 10% reduction in body weight by withholding water (range of body weight loss: 8%-13%). Fourteen rats were assigned to euhydrated, control condition. Estrous stage of female Sprague Dawley rats (n = 30) was determined via cytological evaluation of vaginal smears. Following euthanization, larynges were prepared for histological staining with hematoxylin and eosin, Masson's trichrome and alcian blue (pH 2.5). To quantify hyaluronan, alcian blue staining was completed pre- and posthyaluronidase incubation. The change in staining percent was quantified with image analysis algorithms and reported as the hyaluronan quantity. Relative collagen distribution (index of dehydration), hyaluronan quantity, and tissue morphology were the outcome measures.

RESULTS

Systemic dehydration was associated with changes in hyaluronan quantity in the rat vocal fold lamina propria. Dehydration did not significantly affect the collagen distribution nor the tissue morphology. Estrous stage alone does not impact the quantity of vocal fold hyaluronan, alter tissue morphology, or change collagen distribution.

CONCLUSION

Decreases in hyaluronan quantity in the lamina propria of the rat vocal fold may play a role in tissue fluid balance during systemic dehydration. Future studies will expand this work to investigate additional components of the vocal fold extracellular matrix to fully elucidate the impact of hydration state on the vocal fold.

Electroglottographic and acoustic analysis of voice in children with vocal nodules

PURPOSE

Vocal fold nodules are usually caused by voice overuse or vocal hyperfunction, and their symptoms include persistent hoarseness - a disturbance in the vocal fold vibrations which results in a turbulent passage of air in the glottis, manifested as a raspy, rough voice. The aim of the study was to present data concerning voice quality in patients with vocal nodules and to compare electroglottographic analysis (EGG) with acoustic analysis.

METHODS

The study examined 57 children with vocal fold nodules (Group 1). Each patient underwent a phoniatric evaluation of the vocal tract, a videolaryngoscopic examination, and a voice quality assessment, employing electroglottographic and acoustic analyses. The control group consisted of 37 healthy children (Group 2). The following parameters were analyzed: Closed Quotient (EGG signal), Peak Slope, Normalized Amplitude Quotient and Cepstral Peak Prominence (acoustic signal - waveform).

RESULTS

Changes in the EGG signal could be detected in 95% of the patients with vocal nodules, indicating the occurrence of vocal nodules and glottal insufficiency. The acoustic analysis confirmed breathy phonation in 63% of the patients. The Closed Quotient parameter proved to be more effective than Peak Slope. Closed Quotient, Peak Slope and Normalized Amplitude Quotient allowed for the differentiation of the EGG signal and the acoustic signal in groups 1 and 2 in a statistically significant way.

CONCLUSIONS

The results of electroglottographic and acoustic analysis show incorrect voice parameters in patients with vocal nodules with reference to the control group. At the same time, the EGG analysis proved to be more effective than the analysis of the acoustic signal.

Inspiratory and Expiratory Flow Changes, Voice Symptoms and Laryngeal Findings during Histamine Challenge Tests

OBJECTIVE

The aim of this study was to analyse the associations between the spirometry parameter changes in relation to laryngeal finding changes and self-reported voice and throat symptom changes among patients undergoing a histamine challenge test.

PATIENTS AND METHODS

Thirty adult patients with a chronic cough underwent a histamine challenge test. Videolaryngostroboscopy and voice and throat symptoms were assessed using a visual analogue scale immediately before and after the challenge test. Correlations between the relative changes in spirometry values in relation to the change in vocal fold oedema and redness and self-reported voice and throat symptom changes during the challenge test were assessed.

RESULTS

A correlation between the relative change in inspiratory and expiratory air flow values and the change in voice and throat symptoms during the histamine challenge test was found. The vocal fold oedema, visible on videolaryngostroboscopy, caused by the histamine challenge did not significantly affect the spirometry air flow values.

CONCLUSION

The relative changes in inspiratory and expiratory air flow and voice and throat symptoms during the histamine challenge test correlated. The vocal fold oedema caused by the histamine challenge, visible on videolaryngostroboscopy, did not significantly affect the spirometry air flow values.

Air Injection and Transillumination in Phonosurgery: A Novel Technique

OBJECTIVES/HYPOTHESIS

The goal of this study was to introduce two novel techniques in phonomicrosurgery, air injection (AIR), and transillumination (TI), to improve the diagnosis and surgical excision of pathological tissue in vocal folds during suspension laryngoscopy while preserving the healthy tissue as much as possible.

STUDY DESIGN

Prospective clinical case series.

METHODS

Thirty-four patients with benign vocal cord lesions who underwent phonomicrosurgery between January 2016 and May 2017 were evaluated. Pre- and intraoperative recordings were evaluated by three experienced laryngologists. Stroboscopic video images taken during the preoperative diagnosis and interoperative video recordings made before and after AIR and TI were performed were reviewed and compared. During the preoperative evaluation, the surgeons declared their surgical plans and noted changes while observing the intraoperative evaluation during AIR and TI.

RESULTS

Sixty-eight vocal folds were evaluated. The initial diagnosis was found to be consistent with the final diagnosis in only 10 patients (29.4%). The diagnoses of 29 vocal folds (42.6%) and the surgical plans changed after AIR and TI. In six cases, submucosal bands, additional morphological structures in the vicinity of the primary pathology, were observed; these could only be visualized with AIR and TI. AIR and TI revealed new pathologies in four vocal folds that were noted to be normal in the preoperative evaluation.

CONCLUSION

AIR and TI are useful and promising techniques to identify undiagnosed lesions in vocal folds and to increase the success of minimally invasive phonosurgery.

Incorporation of types I and III collagen in tunable hyaluronan hydrogels for vocal fold tissue engineering

Vocal fold scarring is the fibrotic manifestation of a variety of voice disorders, and is difficult to treat. Tissue engineering therapies provide a potential strategy to regenerate the native tissue microenvironment in order to restore vocal fold functionality. However, major challenges remain in capturing the complexity of the native tissue and sustaining regeneration. We hypothesized that hydrogels with tunable viscoelastic properties that present relevant biological cues to cells might be better suited as therapeutics. Herein, we characterized the response of human vocal fold fibroblasts to four different biomimetic hydrogels: thiolated hyaluronan (HA) crosslinked with poly(ethylene glycol) diacrylate (PEGDA), HA-PEGDA with type I collagen (HA-Col I), HA-PEGDA with type III collagen (HA-Col III) and HA-PEGDA with type I and III collagen (HA-Col I-Col III). Collagen incorporation allowed for interpenetrating fibrils of collagen within the non-fibrillar HA network, which increased the mechanical properties of the hydrogels. The addition of collagen fibrils also reduced hyaluronidase degradation of HA and hydrogel swelling ratio. Fibroblasts encapsulated in the HA-Col gels adopted a spindle shaped fibroblastic morphology by day 7 and exhibited extensive cytoskeletal networks by day 21, suggesting that the incorporation of collagen was essential for cell adhesion and spreading. Cells remained viable and synthesized new DNA throughout 21 days of culture. Gene expression levels significantly differed between the cells encapsulated in the different hydrogels. Relative fold changes in gene expression of MMP1, COL1A1, fibronectin and decorin suggest higher degrees of remodeling in HA-Col I-Col III gels in comparison to HA-Col I or HA-Col III hydrogels, suggesting that the former may better serve as a natural biomimetic hydrogel for tissue engineering applications. STATEMENT OF SIGNIFICANCE: Voice disorders affect about 1/3rd of the US population and significantly reduce quality of life. Patients with vocal fold fibrosis have few treatment options. Tissue engineering therapies provide a potential strategy to regenerate the native tissue microenvironment in order to restore vocal fold functionality. Various studies have used collagen or thiolated hyaluronan (HA) with gelatin as potential tissue engineering therapies. However, there is room for improvement in providing cells with more relevant biological cues that mimic the native tissue microenvironment and sustain regeneration. The present study introduces the use of type I collagen and type III collagen along with thiolated HA as a natural biomimetic hydrogel for vocal fold tissue engineering applications.