Further studies of phonation threshold pressure in a physical model of the vocal fold mucosa

This paper reports results of further experimentation on a previously developed physical model of the vocal-fold mucosa [Titze et al., J. Acoust. Soc. Am. 97, 3080-3084 (1995)]. The effects of vocal-fold thickness, epithelial membrane thickness, and prephonatory glottal geometry on phonation threshold pressure were studied. Phonation threshold pressures in the range of 0.13 to 0.34 kPa were observed for an 11-mm-thick vocal fold with a 70-micron-thick "epithelial" membrane for different "mucosal" fluid viscosities. Higher threshold pressure was always obtained for thinner vocal folds and thicker membranes. In another set of experiments, lowest offset threshold pressure was obtained for a rectangular or a near-rectangular prephonatory glottis (with a glottal convergence angle within about +/- 3 degrees). It ranged from 0.07 to 0.23 kPa for different glottal half-widths between 2.0 and 6.0 mm. The threshold for more convergent or divergent glottal geometries was consistently higher. This finding only partially agrees with previous analytical work which predicts a lowest threshold for a divergent glottis. The discrepancy between theory and data is likely to be associated with flow separation from a divergent glottis.     

Reticular fibers in the vocal fold mucosa

Light and electron microscopic investigations of the reticular fibers (RFs) in the vocal fold mucosa were carried out on excised human adult larynges. The results are summarized as follows. Reticular fibers were found in the superficial and intermediate layers of the lamina propria of the vocal fold mucosa. They were most abundantly discovered around the vocal fold edge, and they decreased toward the superior and inferior portions of the vocal folds. The RFs were composed of slender fibrils, about 40 nm in diameter, and having cross-bands with a periodicity of about 67 nm. They were found in close association with the basal lamina of the epithelium and blood vessels. The slender fibrils of the RFs did not form any bundles, but branched and anastomosed. The RFs formed delicate 3-dimensional networks, and the spaces among the fibers were relatively large. Glycoprotein and glycosaminoglycan (proteoglycan) were situated around the RFs and in the spaces among the fibers. Elastic fibers were located in the spaces among the RFs. The 3-dimensional structure of the RFs in the vocal fold mucosa, first demonstrated in this study, appears to be one of the key components of the structural maintenance and viscoelasticity of the vibrating vocal fold tissue.     

Fine three-dimensional structure of pericytes in the vocal fold mucosa

An investigation was carried out to determine the fine three-dimensional structure of pericytes in excised human vocal fold mucosa, by means of scanning and transmission electron microscopic observation. The results are summarized as follows. 1) There were many pericytes around the true capillaries, arterial capillaries, and venous capillaries in the vocal fold mucosa. 2) Newborns had pericytes around the capillaries in the vocal fold mucosa. 3) The pericytes had bulged fusiform or polygonal cell bodies and branching processes. The branching processes consisted of long and relatively thick longitudinal ones and short circumferential ones. 4) The cell body and processes of the pericytes encircled the capillaries, and the tips of the processes formed intercellular tight junctions with endothelial cells and made a firm connection with them. 5) The pericytes had many cytoplasmic filaments. 6) The pericytes in the vocal fold mucosa appeared to support and protect capillary walls in the vibrating tissue.     

Finite element modeling of vocal fold vibration in normal phonation and hyperfunctional dysphonia: implications for the pathogenesis of vocal nodules

Schizophrenia may involve disturbed subcortical mechanisms or anomalous functional asymmetries. We therefore examined any anomalies of functional asymmetry in a kinematic analysis of a cued sequential movement task previously found to be sensitive to basal ganglia dysfunction. Twenty patients with schizophrenia and 20 matched controls used preferred or non-preferred hand to connect a series of targets on a WACOM SD420 graphics tablet, in response to the pattern of illumination of light emitting diodes (LEDs). Movements were to be initiated with or without an external cue as to target location. Patients with schizophrenia exhibited relatively normal functional asymmetries, but had programming deficits, taking longer to initiate (i.e. self generate) movements in the absence of an external cue. The movements of patients with schizophrenia were more variable and less efficient, resembling those seen in Huntington's disease. Results supported a hypothesis of disturbance at some level in fronto-subcortical circuitry in schizophrenia.     

Changing etiology of vocal fold immobility

HYPOTHESIS: Vocal fold immobility is a sign of underlying disease. When the etiology remains unclear, evaluation may become time consuming and costly, and directed work-up imperative. This study examined the hypothesis that the etiologies of vocal fold immobility are changing, with extralaryngeal malignancies and nonthyroidectomy surgical trauma having become more common causes. METHODS: A retrospective review of consecutive patients with vocal fold immobility who had an adequate workup to determine the etiology. RESULTS: Three hundred ninety-seven cases with a determined etiology were identified, yielding 280 unilateral and 117 bilateral immobilities. The largest single category in unilateral immobility was nonlaryngeal malignancy--69 patients (24.7%)--80% of which were pulmonary or mediastinal, followed by 67 patients (23.9%) with immobility secondary to surgical trauma. Thyroidectomy accounted for only 8.2%. The leading cause of bilateral immobility was surgical trauma-30 patients (25.7%)--21 (18%) of whom had thyroidectomy. Acute and chronic intubation injuries accounted for 21 unilateral (7.5%) and 18 bilateral (15.4%) cases. CONCLUSIONS: These data indicate a changing etiology of vocal fold immobility, with growing percentages of extralaryngeal malignancies and surgery-related injuries. These findings have implications for the timing and method of management based on anticipated outcome.     

A precricoid swelling in a patient treated with Teflon injection in the vocal fold after idiopathic left vocal fold palsy

Vocal fold palsy is a cause of dysphonia. Due to incomplete glottic closure during phonation, patients with a unilateral vocal fold palsy present with a weak and breathy voice and recurrent aspiration. To lessen the clinical manifestations of unilateral vocal fold palsy, polytetrafluoroethylene (Teflon) paste is one agent which has been injected into the paraglottic region, thus causing the vocal fold to move more medially. One of the complications associated with Teflon paste injection is migration of the paste into the surrounding tissues. We present a patient with idiopathic left vocal fold palsy who underwent Teflon injection to the vocal fold and subsequently developed a precricoid nodule, mimicking a cartilaginous swelling.     

Correlation between vocal functions and glottal measurements in patients with unilateral vocal fold paralysis

Observations and analysis of glottal characteristics are critical in choosing the best modality for surgery in patients with unilateral vocal fold paralysis (UVP). This study suggests that multiple glottal characteristics influence the vocal product in patients with UVP. In addition to the horizontal position of the paralyzed vocal fold (deviation from the midline), the glottal area, degree of bowing of the paralyzed and contralateral vocal folds, maximum separation between vocal folds, compensatory glottal maneuvers, and the vertical glottic closure plane significantly influenced the quality of the voice. Clinicians should be aware of these observations to facilitate treatment planning and assessment of the results of surgical procedures used to improve voice quality in cases of UVP.     

Swallowing performance in patients with vocal fold motion impairment

Twenty-seven patients with vocal fold motion impairment underwent detailed pharyngoesophagel manometry with a strain gauge assembly linked to a computer recorder. Nine were known to have lesions of the central vagal trunk or nucleus, 9 had recurrent laryngeal nerve (RLN) palsy, and the remainder were idiopathic. The site of the lesion was a more important determinant of subjective swallowing performance than the position of the involved cord at laryngoscopy. Patients with central lesions had lower tonic and contraction upper esophageal sphincter (UES) pressures than 25 age-matched controls, suggesting that high cervical branches of the lower cranial nerves are important in UES excitatory innervation. RLN palsy patients showed significantly increased pharyngeal contraction amplitude and reduced pharyngoesophageal wave durations. The results suggest that the dysphagia associated with vocal fold motion impairment is not simply due to the disruption of laryngeal deglutitive kinetics, but to independent effects on pharyngeal function.     

Inverse sequence similarity in proteins and its relation to the three-dimensional fold

PURPOSE: To determine whether an expression vector that encodes for human tyrosinase, the key enzyme in the melanin production pathway, can be used to image gene expression with magnetic resonance (MR) imaging and scintigraphy. MATERIALS AND METHODS: Mouse fibroblasts and human embryonal kidney cells were transfected with an expression vector that contained a complete complementary DNA sequence that encodes the human tyrosinase gene (pcDNA3tyr). Transfected cells were assayed for messenger RNA presence, melanin staining, and indium-111 binding; scintigraphy and MR imaging were performed. RESULTS: Transfected cells contained tyrosinase messenger RNA and stained positively for melanin. Transfected cells had a higher In-111 binding capacity than nontransfected cells, a difference readily detectable with scintigraphy. MR imaging showed transfected cells to have markedly higher signal intensity after gene transfer than nontransfected cells. CONCLUSION: Gene transfer and expression in cell culture can be detected with MR imaging and scintigraphy. The proposed strategy of using an imaging marker gene may have a substantial effect on the noninvasive imaging of gene therapy.     

Analysis of pathological vocal fold vibrations using high-speed digital imaging

There have been various methods devised to monitor vocal fold vibration. Stroboscopy provides clinically-celevant information concerning pathology of the vocal folds. However, slow motion observation is based on the regularity of the vibration, and this ignores the role of irregularity of the vocal fold vibration in pathological cases. In order to know more about the nature of the vocal fold vibratory pattern, it is essential to monitor the vibration on a cycle by cycle basis. We analysed vocal fold vibrations of 22 pathological larynges using a computer-assisted high-speed digital imaging technique. Observed items included symmetry, regularity, phase difference, glottal closure, amplitude, mucosal wave and periodicity difference. Vibratory patterns were classified by location of lesion, severity of disease, expiratory pressure and laryngeal modulation. Analyses of pathological vocal fold vibrations using high-speed digital imaging techniques are providing the theoretical support for voice therapy and elucidating the causes of hoarseness.     

Langerhans cells in normal and pathological vocal cord mucosa

The Langerhans cells in samples of histologically normal and pathological vocal cord mucosa were counted after identification using S-100 polyclonal antibody. Langerhans cells were commonly seen in vocal cord polyp epithelium but were infrequent in normal cord mucosa. They were also identified in samples of squamous carcinoma, severe dysplasia and chronic inflammation.     

A nonlinear operator-based speech feature analysis method with application to vocal fold pathology assessment

Traditional speech processing methods for laryngeal pathology assessment assume linear speech production with measures derived from an estimated glottal flow waveform. They normally require the speaker to achieve complete glottal closure, which for many vocal fold pathologies cannot be accomplished. To address this issue, a nonlinear signal processing approach is proposed which does not require direct glottal flow waveform estimation. This technique is motivated by earlier studies of airflow characterization for human speech production. The proposed nonlinear approach employs a differential Teager energy operator and the energy separation algorithm to obtain formant AM and FM modulations from filtered speech recordings. A new speech measure is proposed based on parameterization of the autocorrelation envelope of the AM response. This approach is shown to achieve impressive detection performance for a set of muscular tension dysphonias. Unlike flow characterization using numerical solutions of Navier-Stokes equations, this method is extremely computationally attractive, requiring only a small time window of speech samples. The new noninvasive method shows that a fast, effective digital speech processing technique can be developed for vocal fold pathology assessment without the need for direct glottal flow estimation or complete glottal closure by the speaker. The proposed method also confirms that alternative nonlinear methods can begin to address the limitations of previous linear approaches for speech pathology assessment.     

Thyroarytenoid muscle activity and infraglottic aspect of canine vocal fold vibration

OBJECTIVES: To investigate the effect of contraction of the thyroarytenoid (TA) muscle on the location of the mucosal upheaval (MU) and to estimate the location of the MU in relation to the histologic structure of the vocal fold. BACKGROUND: The MU is a small mucosal ridge arising on the lower surface of the vocal fold during phonation and is thought to be the lower border of the vibrating structure. METHODS: Vibrations were elicited under three conditions: during bilateral TA muscle contraction, without TA muscle stimulation, and during vocal fold lengthening. The vibrations were recorded from the tracheal side by high-speed cinematography or videotape recording combined with stroboscopic illumination. The larynx was prepared for histologic observation in the frontal plane. Tattooed marks on the lower surface of the vocal fold were used to locate macroscopically observed landmarks with reference to microscopic structures. RESULTS: The MU shifted laterally toward the tracheal side during TA muscle contraction. When the vocal fold was lengthened, the MU shifted medially toward the free edge. Histologic examination showed that the MU in the absence of TA muscle contraction arose slightly above the area where the muscular layer approached the epithelial layer. CONCLUSION: When the TA muscle contracts, the vibrating area expands toward the tracheal side, and a more dynamic mucosal wave occurs in the vertical direction. We believe that a part of the body and the cover are probably involved in the vibratory movement of the vocal fold.     

Laryngeal electromyography is a cost-effective clinically useful tool in the evaluation of vocal fold function

Primary cultures of human bronchial epithelial cells (HBE-cells) were established to measure granulocyte-macrophage colony stimulating factor (GM-CSF) release. HBE-cells showed a basal GM-CSF release (82+/-20 ng/well/24 h; 30 donors), which was increased by interleukin-1 beta(IL-1beta, 1 ng/ml) by 270%. This effect was blocked by 1 microM dactinomycin or 10 microM cycloheximide, i.e. the stimulatory effect of IL-1beta depended on de-novo synthesis. Histamine (100 microM) and acetylcholine ( 100 nM) stimulated GM-CSF release more than two-fold above the baseline. Nicotine (1 microM) increased GM-CSF release to a similar extent, and this effect was prevented by 30 microM (+)-tubocurarine. The stimulatory effect was attenuated or even lost with high agonist concentrations (10 microM acetylcholine; 100 microM nicotine) suggesting receptor desensitization. The muscarinic receptor agonist oxotremorine did not affect GM-CSF release. Serotonin, substance P and calcitonin-gene related peptide had no effect on GM-CSF release. In conclusion, acetylcholine can trigger GM-CSF release from human airway epithelial cells via stimulation of nicotinic receptors.     

Temperature distribution in expiratory speaking flow, and early detection of vocal fold pathology

This paper describes an application of heat transfer fundamentals to the development and testing of an instrument with potential use for speech production analysis. The method exploits an assumed difference between the air flow patterns of individuals with healthy and breathy voices: during breathy speech production, the glottis does not close completely, and the leakage of warm air through the glottis increases the extent of the temperature field outside the oral cavity. The proposed instrument is a pipe through which the tested individual breathes out while producing a sustained vowel. The pipe wall temperature is maintained uniform at a level considerably lower than the body temperature. The temperature gradient along the pipe centreline is measured and related to the average air velocity through the glottis. The measurements compare favourably with numerical results for the temperature field inside the instrument. These findings therefore suggest that the temperature distribution outside the oral cavity could be useful in understanding changes in air flow patterns through the vocal folds. The centreline temperature chart to be used in conjunction with the instrument is reported in dimensionless terms.     

Vocal fold strain and vocal pitch in singing: radiographic observations of singers and nonsingers

The relationship between vocal fold strain and vocal pitch in singers and nonsingers singing a rising pitch series has been indirectly investigated by means of lateral radiographs. Nonsingers tend to exhibit more strain than singers. To standardize the degree of strain, an index of strain per semitone is proposed. The semitone strain indicates the average amount of strain per 1 semitone of pitch increase or decrease. The index has been shown to be affected by several factors: gender, singing training, singing technique, voice class, age, and status of muscle function. Observations suggest that similar groups of individuals occupy different positions on the stress-strain curve, indicated by their semitone strain values.     

Lubrication mechanism of the larynx during phonation: an experiment in excised canine larynges

To evaluate how the viscosity of the laryngeal mucus influences vocal fold vibration, two fluids of differing viscosity were applied separately to excised canine larynges and experimental phonation was induced. Vibration of the vocal folds was measured by use of a laryngostroboscope and an X-ray stroboscope. With the high viscosity fluid, the amplitude of vibration of the free edge and the peak glottal area was decreased while the open quotient was increased. Because the viscosity of this fluid affected the wave motion of the vocal fold mucosa, changes in viscosity of the mucus may be involved in causing such disorders as hoarseness, in the absence of apparent changes in the vocal folds themselves.     

The effects of intraoral pressure change on F0 regulation--preliminary study for the evaluation of vocal fold stiffness

This study was intended to evaluate the stiffness of the vocal folds noninvasively. As a first step, the relationship between vocal fundamental frequency (F0) and intraoral pressure (P0) was investigated. F0 was recorded during production of forced P0 changes in three men and four women while they uttered sustained vowels. The pressure changes were applied by closing a valve mounted on a mouthpiece. Changes in F0 as a function of changes in P0 (dF0/dP0) were then measured. The values of dF0/dP0 varied with F0 in a manner inherent to each subject. The relationship between dF0/dP0 and F0 was found to have a potential benefit for the evaluation of stiffness at a specific length of vocal fold.