Atomic force microscopy investigation of vocal fold collagen

OBJECTIVES: Collagen is an important constituent of the vocal fold extracellular matrix and is necessary for providing tensile strength and maintaining tissue geometry. Traditional investigations of vocal fold collagen using light and electron microscopy do not provide information on the organization and mechanical properties of collagen in native topographic state. The primary objective of this study was to use Atomic Force Microscopy (AFM) to examine the surface characteristics and organization of collagen in the deep layer of the lamina propria at nanoscale resolution. STUDY DESIGN: Experimental in vitro design. METHODS: Freshly dissected porcine vocal folds were mounted on AFM discs and imaged under contact and tapping mode to obtain information on topographic distribution of collagen. RESULTS: AFM imaging of the deep layer of the lamina propria revealed dense, abundant collagen fibers with a characteristic banding pattern. The distribution of collagen was heterogeneous, with both hydrophilic and hydrophobic regions within a sample. CONCLUSIONS: AFM offers a useful tool to obtain topographic information about biologic samples at nanoscale resolution with minimal sample preparation. Mapping the topography and mechanical properties of vocal fold collagen is necessary for designing rheologically compatible bioimplants for the treatment of dysphonia resulting from vocal fold scarring and bowing.     

Aerodynamics of the human larynx during vocal fold vibration

OBJECTIVES:: The goal of this study was to comprehensively analyze the influence of aerodynamics on laryngeal function. Three specific aspects were considered: 1) a multidimensional comparison of the interaction of subglottic pressure, sound intensity, and fundamental frequency; 2) examination of instantaneous changes in subglottic pressure during each glottic cycle; and 3) determination of the threshold subglottic pressure for vocal fold vibration and its dependence on other aerodynamic factors. STUDY DESIGN:: Prospective study with six healthy individuals without history of voice disorders. METHODS:: The subjects vocalized the vowel sound /i/ with a variety of different intensities, pitch, and sound intensity. Subglottic air pressure, fundamental frequency, sound intensity, and the electroglottography signal were simultaneously measured. RESULTS:: Linear relationships were seen in all subjects between subglottic air pressure and sound intensity, although there were large variations in the slopes of these relationships. Rapid variations in subglottic pressure during each glottic cycle were detected, corresponding to the opening of the vocal folds with each individual vibration. Threshold pressures for vocal fold vibration were dependent primarily on sound intensity and fundamental frequency and tended to be higher at vibration onset than at offset. CONCLUSION:: The larynx responded in a predictable pattern to general aerodynamic forces, but there was tremendous variability in its specific behavior. Fundamental frequency and sound intensity tended to increase with subglottic air pressure, but that relationship was not seen consistently in all subjects. The relationship between subglottic air pressure and sound intensity was usually linear, unlike the exponential relationship seen in previous studies. Subglottic pressure was noted to undergo rapid change with each glottic cycle in some, but not all, subjects and was most strongly affected by average subglottic pressure. Phonation threshold air pressure was influenced by the sound intensity and, to a smaller extent, by the fundamental frequency of the voiced sound.     

Cyclic adenosine monophosphate regulation of ion transport in porcine vocal fold mucosae

Objectives/Hypothesis: Cyclic adenosine monophosphate (cAMP) is an important biological molecule that regulates ion transport and inflammatory responses in epithelial tissue. The present study examined whether the adenylyl cyclase activator, forskolin, would increase cAMP concentration in porcine vocal fold mucosa and whether the effects of increased cAMP would be manifested as a functional increase in transepithelial ion transport. Additionally, changes in cAMP concentrations following exposure to an inflammatory mediator, tumor necrosis factor‐α (TNFα) were investigated. Study Design: In vitro experimental design with matched treatment and control groups. Methods: Porcine vocal fold mucosae (N = 30) and tracheal mucosae (N = 20) were exposed to forskolin, TNFα, or vehicle (dimethyl sulfoxide) treatment. cAMP concentrations were determined with enzyme‐linked immunosorbent assay. Ion transport was measured using electrophysiological techniques. Results: Thirty minute exposure to forskolin significantly increased cAMP concentration and ion transport in porcine vocal fold and tracheal mucosae. However, 30‐minute and 2‐hour exposure to TNFα did not significantly alter cAMP concentration. Conclusions: We demonstrate that forskolin‐sensitive adenylyl cyclase is present in vocal fold mucosa, and further, that the product, cAMP increases vocal fold ion transport. The results presented here contribute to our understanding of the intracellular mechanisms underlying vocal fold ion transport. As ion transport is important for maintaining superficial vocal fold hydration, data demonstrating forskolin‐stimulated ion transport in vocal fold mucosa suggest opportunities for developing pharmacological treatments that increase surface hydration.     

Viscoelasticity of hyaluronan and nonhyaluronan based vocal fold injectables: implications for mucosal versus muscle use

OBJECTIVES: The purpose of this study was to measure and compare biomechanical properties of commonly used vocal fold injectates Cymetra, Radiesse, Restylane, Hylaform, and one investigational injectate, Carbylan-GSX 5%, to determine suitability for mucosal injection. STUDY DESIGN: Rheologic investigation. METHODS: Oscillatory shear stress was applied to five samples of each injectate using a parallel plate controlled stress rheometer. Shear stress, shear strain, and strain rate associated with the oscillatory shear deformation were computed from the prescribed torque and measured angular velocity; viscoelastic data were obtained on the basis of these functions. Values calculated included elastic shear moduli, viscous moduli, and dynamic viscosity as a function of oscillatory frequency (0.01-150 Hz). RESULTS: Elastic moduli for all samples increased as the frequency increased. Hyaluronan based materials were all comparable with each other and at least an order of magnitude lower than the stiffer and more viscous Cymetra and Radiesse. Carbylan-GSX 5% was found to have almost identical values to Hylaform with the exception of its mean viscosity, which was noticeably lower. CONCLUSIONS: Hyaluronan based biomaterials offer less resistance to flow and stiffness and may be better suited for injections into the mucosa, whereas Cymetra and Radiesse appear to be appropriate for injections into muscle. Viscoelastic properties of Hylaform and Carbylan-GSX 5% were found to most resemble that of the human vocal fold mucosa.     

The utility of evaluating true vocal fold motion before thyroid surgery

OBJECTIVE: The objective of this study was to evaluate the utility of screening laryngoscopic examination in evaluating vocal fold (VF) mobility before thyroid surgery. METHODS: The authors conducted a retrospective chart review of 340 patients who have undergone thyroid surgery from January 1998 to June 2005 and had preoperative laryngoscopy by mirror, fiberoptic, or videostroboscopic examination. Reports of preoperative voice change or complaint and reports of preoperative VF examination, including the method of examination, were recorded. For patients with VF motion impairment, reports of the intraoperative condition of the recurrent laryngeal nerve (RLN), preoperative diagnosis based on fine needle aspiration, and final postoperative histopathologic examination results were recorded. RESULTS: Twenty-two patients were found to have preoperative VF motion impairment, of which seven (32%) patients were asymptomatic with no detectable subjective or objective voice problems. This differs significantly from the hypothesis that patients with VF motion impairment are always symptomatic (P=.009). Using voice symptoms as a screening test to predict VF motion impairment in 340 patients reveals that the sensitivity was 68%, specificity was 91%, positive predictive value (PPV) was 31%, and negative predictive value (NPV) was 98%. Among the 22 patients with preoperative VF motion impairment, five (72%) of the seven asymptomatic patients had benign, slowly progressive disease on their final histopathology reports. Six of these asymptomatic patients had their preoperative VF evaluation by fiberoptic examination, whereas one patient had indirect mirror laryngoscopy. Of 22 patients with preoperative VF motion impairment, five (22.5%) patients had abnormal VF mobility contralateral to the thyroid lesion on their preoperative evaluation, and only two of them had nerve injury reported after a previous thyroid surgery. This result differs significantly from the hypothesis that impaired mobility is ipsilateral to the side of the lesion (P=.05). CONCLUSIONS: Patients without voice complaints can have VF motion impairment. Patients can also have VF motion impairment contralateral to the thyroid lesion. Preoperative VF examination helps counsel patients appropriately about the risks of surgery and helps outline a plan for the extent of surgery while minimizing the medicolegal ramifications of iatrogenic RLN injury.     

Laterofixation of the vocal fold using an endo-extralaryngeal needle carrier for bilateral vocal fold paralysis

Objectives

Laterofixation of the vocal fold is a simple and reliable surgical intervention for laryngeal obstruction due to bilateral vocal fold fixation to obtain sufficient glottal space. Nevertheless, it has some technical disadvantages. This report summarizes the surgical outcomes in patients who underwent laterofixation of the vocal fold with or without the use of an endo-extralaryngeal needle carrier (EENC).

Methods

A prospective study of 11 consecutive patients with bilateral vocal fold paralysis. All of the patients underwent unilateral vocal fold laterofixation. Six patients were assigned to the non-EENC group and five to the EENC group. The surgical outcomes were evaluated, including the operating time and respiratory and phonatory functions.

Results

The operating time was 44% shorter in the EENC group and less skin incisions were required. Postoperatively, the dyspnea was eliminated in all of the patients in both groups, and the six patients who required a tracheotomy were successfully decannulated. Spirometry confirmed the improvements in %FEV₁ and %PEF in the two groups. Postoperative voice function was socially acceptable in all patients, and it tended to be better in the non-EENC group. In the EENC group, one patient developed a minor submucosal hematoma and another patient had a recurrence of dyspnea 2 months postoperatively, probably due to thread disruption.

Conclusion

The present study confirms that laterofixation of the vocal fold with or without EENC relieves laryngeal obstruction. Surgery with the EENC is simpler and quicker than the conventional procedure. However, the surgery with the EENC has some disadvantages, including likely problems with the thread and downward traction on the vocal fold. Surgeons should be aware of these possible shortcomings.     

Voice and vocal fold position in men with unilateral vocal fold paralysis

The paralyzed vocal fold positioning and the degree of dysphonia are important inputs when one is deciding upon treatment options for unilateral vocal fold paralysis (UVFP).ObjectiveTo check voice characteristics and paralyzed vocal fold position in men with UVFP.Materials and MethodsThis is a retrospective historical cross-sectional cohort study, with data from 24 men with UVFP with mean age of 60.7 years, submitted to voice assessment by three speech therapists and three ENT physicians used laryngeal images to classify the position of the paralyzed vocal fold.ResultsThe paralyzed vocal fold was found in the paramedian position in 45.83% of the cases; in the intermediary position in 25%; lateral in 20.83%, and it was in the median position in 4.16%; the dysphonia resulting from the UVFP was characterized by moderate hoarseness, roughness and stress in the voice; breathiness (most had severe breathiness); weakness and instability(mostly mild); the position of the paralyzed vocal fold had a significant influence on the general degree of vocal deviation.ConclusionThe general degree of dysphonia is associated with the paralyzed vocal fold position; dysphonia is characterized by hoarseness, breathiness, roughness and stress of moderate to severe levels.     

Vocal function after vertical partial laryngectomy with glottic reconstruction by false vocal fold flap: durational and frequency measures.

OBJECTIVE: Compare vocal function following vertical partial laryngectomy (VPL) with or without glottic reconstruction by false vocal fold (FVF) mucosal flap. STUDY DESIGN: Twenty-seven patients with Tla squamous cell carcinoma (SCC) of the glottis were included in a prospective randomized clinical study. All patients were treated by frontolateral partial laryngectomy (FLPL). Glottic reconstruction with FVF mucosal flap was performed in 14 patients at the time of the FLPL, whereas 13 patients had standard FLPL. METHODS: Objective voice assessment was based on computerized acoustic recordings performed before and 1 year after surgery. When possible, additional recordings were performed at 3 months, 6 months, and 2 years postoperatively. Incidence of postoperative granuloma and anterior neoglottic web were noted. Repeated analysis of variance (ANOVA) was used to compare the durational (maximum phonation time, speech rate) and frequency measurements (average fundamental frequency [Fo], standard deviation of Fo, jitter, shimmer, noise-to-harmonics ratio, degree of voice breaks) between patients with or without glottic reconstruction, postoperative granuloma, and anterior neoglottic web. Linear regression was used to study the evolution over time of the durational and frequency measurements. RESULTS: Frequency measurements improved with time and were significantly better in patients treated with glottic reconstruction. In addition, glottic reconstruction decreased incidence of postoperative granuloma and anterior neoglottic web. CONCLUSIONS: The FVF mucosal flap technique can improve vocal results in selected cases of Tla SCC of the glottis when FLPL is the adequate surgical treatment. false vocal folds; glottic reconstruction; vertical partial laryngectomy; vocal function.     

Periodic botulinum toxin injections for paradoxical vocal fold motion in a child with cerebral palsy: A case study

We describe an unusual case of paradoxical vocal fold motion in a child with cerebral palsy. Clinically, the child presented with mild stridor, which worsened over months, eventually requiring emergency intubation. After an unsuccessful trial of medical management, microlaryngoscopy revealed abnormal adduction of the vocal folds during inspiration. This was successfully treated with periodic type A botulinum toxin injections to the vocal folds, sparing the child from tracheostomy.