Thyroplasty by external approach with silastic prosthesis in the treatment of laryngeal paralysis

From August 1995 to January 1997 8 phonosurgical procedures were performed to correct glottal incompetence. There were 4 men and 4 women, the median age was 42 years. The most common indication for thyroplasty was recurrent or vagal nerve injury (6/8 cases). In 7 cases the paralyzed vocal cord was unilateral and in 1 case bilateral after oesophagectomy. Two patients were previously treated by endoscopic injection without success. The procedure was conducted under general anaesthesia. A window in the thyroid ala was created and silastic implant inserted. This technique was indicated to correct large glottal incompetence or in case of failure after endoscopic treatment. There have been no complications. Improvement of post operative voice was noted. The maximum phonation duration, intensity and objective voice measurements were improved in all cases.     

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.     

Estimating phonation threshold pressure

Phonation threshold pressure (PTP) is the minimum subglottal pressure required to initiate vocal fold oscillation. Although potentially useful clinically, PTP is difficult to estimate noninvasively because of limitations to vocal motor control near the threshold of soft phonation. Previous investigators observed, for example, that trained subjects were unable to produce flat, consistent oral pressure peaks during/pae/syllable strings when they attempted to phonate as softly as possible (Verdolini-Marston, Titze, & Druker, 1990). The present study aimed to determine if nasal airflow or vowel context affected phonation threshold pressure as estimated from oral pressure (Smitheran & Hixon, 1981) in 5 untrained female speakers with normal velopharyngeal and voice function. Nasal airflow during /p/occlusion was observed for 3 of 5 participants when they attempted to phonate near threshold pressure. When the nose was occluded, nasal airflow was reduced or eliminated during /p/;however, individuals then evidenced compensatory changes in glottal adduction and/or respiratory effort that may be expected to alter PTP estimates. Results demonstrate the importance of monitoring nasal flow (or the flow zero point in undivided masks) when obtaining PTP measurements noninvasively. Results also highlight the need to pursue improved methods for noninvasive estimation of PTP.     

Aerodynamic and acoustic characteristics of the adult African American voice

Laryngeal aerodynamic and acoustic characteristics of African American voice production were examined from vowel samples produced by ten adult female and ten adult male speakers. The data were compared with that for a control group consisting of ten adult female and ten adult male White speakers, matched for age, height, and weight. All measures were analyzed using Cspeech 4.0. Aerodynamic measurements, extracted from a glottal airflow waveform, included maximum flow declination rate, alternating glottal airflow, minimum glottal airflow, and airflow open quotient. Acoustic measures included fundamental frequency and sound pressure level. No significant mean differences between the African American and White speakers were found, except for maximum-flow declination rate. The White speakers produced significantly higher declination rates than the African American speakers. The factor of sex for the African American speakers was statistically significant for the measures of maximum-flow declination rate, alternating glottal airflow, open quotient, and fundamental frequency, consistent with the functioning of the White speakers. The results suggest that during vowel production, where the vocal tract is in a fairly static position, acoustic and aerodynamic characteristics for African American and White Speakers are comparable.     

Functional voice quality assessment in curative microsurgery of laryngeal malignancies. Postoperative voice rehabilitation based on the "laryngeal double valve function"

According to Negus and Pressman the sphincter systems of the vocal folds and the ventricular folds form a respiratory "laryngeal double valve function". Correspondingly, we found a physiological phonation system of the glottis and a pathological-compensatory one of the supraglottis. They appear to be regulated through an automatic phonatory control system with the glottal phonatory function evidently acting as sensor level. In order to confirm this hypothesis, objective voice analyses with glottal-relevant parameters of 26 voice-rehabilitated patients after minimally invasive laser surgery of glottal carcinomas are presented and integrated into a "hoarseness diagram" with the coordinates roughness and breathiness. Using statistically deliminated acoustic dusters, our data show a qualitative hierarchy of different postoperative phonation mechanisms. They demonstrate the influence of the vibratory capacity of glottal and supraglottal structures on the quality of the vibratory closure. Both functional parameters evidently determine the resulting voice quality in the sense of our hypothesis.     

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.     

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.     

Effects of lung volume on the glottal voice source

According to experience in voice therapy and singing pedagogy, breathing habits can be used to modify phonation, although this relationship has never been experimentally demonstrated. In the present investigation we examine if lung volume affects phonation. Twenty-four untrained subjects phonated at different pitches and degrees of vocal loudness at different lung volumes. Mean subglottal pressure was measured and voice source characteristics were analyzed by inverse filtering. The main results were that with decreasing lung volume, the closed quotient increased, while subglottal pressure, peak-to-peak flow amplitude, and glottal leakage tended to decrease. In addition, some estimates of the amount of the glottal adduction force component were examined. Possible explanations of the findings are discussed.     

Comments on the myoelastic - aerodynamic theory of phonation

The myoelastic-aerodynamic theory of phonation has been quantified and tested with mathematical models. The models suggest that vocal fold oscillation is produced as a result of asymmetric forcing functions over closing and opening portions of the glottal cycle. For nearly uniform tissue displacements, as in falsetto voice, the asymmetry in the driving forces can result from the inertia of the air moving through the glottis. This inertia can in turn be enhanced or suppressed by supraglottal or subglottal vocal tract coupling. More obvious and pronounced asymmetries in the driving forces are associated with non-uniform vocal fold tissue displacements. These are combinations of normal tissue modes, and can result in vertical and horizontal phase differences along the surfaces, as observed in chest voice. The ranges of oscillation increase among various models as more freedom in the simulated tissue movement is incorporated. Of particular significance in initiating and maintaining oscillation are the vertical motions that facilitate coupling of aerodynamic energy into the tissues and allow tissue deformations under conditions of incompressibility. Vertical displacements also can have a significant on vocal tract excitation. Control of fundamental frequency of oscillation (FO) is basically myoelastic, partially as a result of deliberate or reflex adjustments of laryngeal muscles, and partially as a result of nonlinear tissue strain over the vibrational cycle. This places limits on the control of FO by subglottal pressure, and forces such control to be inseparably connected with vibrational amplitude, or less directly, with vocal intensity.     

Medialization laryngoplasty

Medialization laryngoplasty was performed in 25 patients between 1993 and 1997. The underlying pathology resulting in glottal incompetence was vocal cord paralysis in 22 patients and vocal cord bowing in 3 patients. Two types of implants were used: self-carved Proplast in 19 patients and prefabricated hydroxyapatite prostheses in 6 patients. Preoperative and postoperative results were compared in terms of dysphagia, vocal quality as graded by three experienced voice specialists, and computer measurements of the glottal gap. All patients showed improvement both subjectively and on the objective measurements used. Swallowing returned to normal in all patients who had isolated recurrent laryngeal nerve paralysis. The voice improved in all patients but was rarely judged as entirely normal.     

Longitudinal evaluation of vocal function following thyroplasty type I for the treatment of unilateral vocal paralysis

Longitudinal changes of vocal efficiency and stability following thyroplasty type I were analysed. Fifty-three patients with unilateral vocal fold paralysis underwent vocal function evaluation preoperatively and 1, 3 and 6 months postoperatively. Vocal function assessment included videostrobolaryngoscopic examination, acoustical and aerodynamic analyses, and perceptual ratings of voice. Parameters including glottic gag size, maximum phonation time, glottic flow rate, jitter, harmonic to noise ratio, breathness, hoarseness, loudness and phrasing showed significant improvement after thyroplasty and remained stable within 1 month with only slight fluctuations over a 6 month period. Postoperative voice outcome was not affected by age, sex, duration of vocal symptoms, etiology of paralysis, or preoperative pulmonary function.     

Vocal mechanics as the basis for phonosurgery

OBJECTIVE: A number of modifications in laryngoplastic phonosurgery have recently been proposed. This report is intended to clarify the concept on which the surgery should be based, vocal mechanics, for further rational development of the surgery. STUDY DESIGN: The results of various previous surgeries were compared. In an attempt to elucidate what makes the difference in the results, simulation of voice production was conducted with the use of excised larynges. METHODS: Excised larynges were mounted on a tube so as to be blown from below. Experimental variables in the model included the glottal area initially set, stiffness of the vocal folds, and subglottal pressure. The conditions under which the voice became hoarse were examined. RESULTS: The voice became hoarse under the following major conditions: 1) the initial glottal area exceeded a certain value, 2) stiffness was too high, and 3) the glottis was too tightly closed. Clinical representation for each condition was made, particularly for excessively tight glottal closure such as in spasmodic dysphonia. A new type of surgical treatment for spasmodic dysphonia, lateralization thyroplasty, was briefly reported, which restored the voice to normal without recurrence for 1 year at the time of this writing. CONCLUSIONS: A potential new type of laryngoplastic phonosurgery should be conformed to the mechanics of voice production. In treating dysphonia, it is often necessary to switch from etiologic or radical treatment, if infertile, to symptomatic treatment instead, at the level of mechanics.     

Financing changes of schistosomiasis control programmes in China 1980-1995: a case study in Songzi county

The biomechanics of arytenoid adduction surgery are not well understood. An excised canine larynx model was used to study the effects of variable suture tension on glottal configuration and on vocal fold tension (at the midfold and the vocal process). Arytenoid adduction both medializes the vocal fold and closes a posterior glottal chink. Vocal fold tension at the midfold did not vary significantly with suture tension. As suture tension increased to approximately 100 g, vocal fold tension at the vocal process also increased. Beyond 100 g of suture tension, vocal fold tension at the vocal process did not increase. We conclude that the effects of suture tension on the resistance to lateral movement are different at the midfold compared to the vocal process. Procedures for surgical rehabilitation of vocal fold paralysis should address the biomechanical subunits of the larynx individually in order to achieve optimum results.     

Pliability of the vocal fold mucosa in relation to the mucosal upheaval during phonation

OBJECTIVES: To quantitatively evaluate the effect of vocal fold lengthening on pliability of the mucosa measured along the superior-inferior axis and to examine the relation of the location of mucosal upheaval (MU) during phonation to the changes in pliability pattern of the mucosa when the vocal fold was lengthened. DESIGN: Investigation of mechanical characteristics of the vocal fold in relation to the MU during phonation. MATERIALS: Five excised canine larynges. INTERVENTIONS: Vibrations with and without vocal fold lengthening were recorded from the tracheal side via high-speed photography or video recording combined with stroboscopic illumination. Tattooed marks on the lower surface of the vocal fold were used to locate the MU. Pliability was defined as the maximal distance elevated in response to a constant focal negative pressure. RESULTS: Pliability decreased significantly (P=.05) when the vocal fold was lengthened. The point of minimal pliability and MU without vocal fold lengthening were located slightly above the area where the muscular layer approached the epithelial layer. They were located closer to the free edge of the vocal fold when it was lengthened than when it was not. Discrepancy of their locations when the vocal fold was lengthened was suggested. CONCLUSIONS: The MU occurs around the point of minimal pliability when the vocal fold is not lengthened, whereas the MU occurs slightly more laterally than the point of minimal pliability when the vocal fold is lengthened. Although further study is necessary to explain this discrepancy, the presence of the sparse deep layer of the lamina propria seems to be essential in the generation of the mucosal wave.     

Endoscopic imaging of vocal cord vibrations. Digital high speed recording with various systems]

Vocal fold vibration patterns during phonation are presented with different digital imaging systems. With newly developed technical equipment color images up to 1000 digital images/s were obtained without light intensifying enhancement techniques via rigid and flexible endoscopy. With this color high-speed system, morphologic structures, such as small blood vessels, were visualized in high-resolution quality as a result of additional color information. In another system, zooming of endoscopic pictures via pixel interpolation algorithms provided full-monitor presentation of vocal fold vibratory patterns. This system allows PC-based synchronization with microphone and electroglottographic signals in a frame-by-frame technique. Although only processing gray scale images, analyses of dynamic changes in modes of vibration were facilitated by the higher frame rate recording of up to 2000 frames/s and, in addition, they display corresponding analog signals. Both methods provide clinically important information. Furthermore, we demonstrated irregular vocal fold vibration patterns in a healthy adult volunteer. In this experiment, the irregular vibratory modes were induced by voluntarily applying asymmetric vocal fold tension. The asymmetric vocal fold vibration pattern resulted in (functionally induced) roughness of the voice as predicted by computer models of asymmetric vocal fold vibration. Digital high-speed cinematography proved to be a highly promising technique in the analysis of dysphonia and provided physiological examples that could be compared with models of coupled nonlinear oscillators.     

Nucleotide sequencing analysis of the 146-kilobase segment around the IkBL and MICA genes at the centromeric end of the HLA class I region

The biomechanics of medialization laryngoplasty are not well understood. An excised canine larynx model was used to test the effects of various sized silicon implants. The vocal fold length, position, and tension were measured. Medialization laryngoplasty did not affect vocal fold length. At the mid-membranous vocal fold, larger shims resulted in greater medialization and tension. Medialization laryngoplasty neither medialized nor stiffened the vocal process to resist lateralizing forces. We conclude that medialization laryngoplasty provides bulk and support for defects of the membranous region of the vocal fold, but does not appear to close a posterior glottal gap. The selection of a surgical procedure to treat glottal incompetence should take into account the unique biomechanical properties of the anterior (membranous vocal folds) and posterior (cartilaginous portion) glottis.     

Changes in glottal configuration in women after loud talking

The purpose of this investigation was to examine changes in glottal configuration in women under a variety of pitch and loudness conditions after an interval of loud reading. Twelve young adult women with normal laryngeal structures were photographed under stroboscopic light and sustained the vowel/i/for a minimum of 3 s, at three pitch levels and three loudness levels, before and after a 15-min interval of loud reading. Results indicate that female speakers tend to alter glottic configurations across phonatory conditions after loud reading, particularly during high-pitch phonation. Specifically, five subjects tended to increase glottal closure, one tended to increase glottal opening, two tended to maintain the identical configuration, and four demonstrated no consistent pattern of response.     

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.     

Prevalence of hypertension in patients with type II diabetes in referral versus primary care clinics

We report our clinical experience in managing a 59-year-old Italian male with Churg-Strauss syndrome (CSS) whose first clinical manifestation was a persistent dysphonia; the patient worked as a mechanic. Video-laryngostroboscopic examination revealed paresis of the right vocal fold with a reduction in adduction together with incomplete glottal closure. Spectrographic and spirometric tests both showed abnormal changes. Laryngeal electromyography revealed neurogenic damage of the right thyroarytenoid and crycoarytenoid muscles. Due to the appearance of typical signs of systemic involvement of CSS as a necrotizing vasculitis, the patient was admitted to the Rheumatology Unit of the University of Pisa. Histologic analysis of a skin lesion on the patient's foot confirmed the diagnosis. Treatment with 6-methylprednisolone quickly brought remission from systemic and laryngeal symptoms, as well as improvement in the results of video-laryngostroboscopic, spectrographic and laryngeal myographic tests.     

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.