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.     

Autologous fat injection for unilateral vocal fold paralysis

This study evaluates the efficacy of autologous fat injection for medialization of the paralyzed vocal fold. In 21 patients with unilateral vocal fold paralysis, autologous abdominal fat was injected into the thyroarytenoid muscle to achieve medialization. All patients were followed up with serial videolaryngoscopy and voice evaluation. At 2 months' follow-up, the voice was judged to be excellent in 10 patients, slightly breathy but significantly better than the preoperative voice in 6 patients, and markedly breathy in 4 patients. At 3 to 4 months' follow-up, of the 10 patients with excellent results, 5 maintained an excellent voice, 3 had developed slight breathiness, and 1 had developed severe breathiness. Long-term (6 to 12 months) results were available in 11 patients, and all of them maintained the same voice quality that was noted during the 3 to 4 months' examination. Magnetic resonance imaging of the larynx was obtained in 7 patients at intervals ranging from 1 to 7 months and compared to the baseline scan obtained at 1 week postoperative to assess the amount of fat remaining in the muscle. The images showed fat volume to persist, but a decrease in the fat signal was observed over time. The results suggest that the duration of medialization with autologous fat is variable, but appears to last at least 2 to 3 months. This loss of volume after 3 months seems to be due to absorption of the fat and possibly muscle atrophy. Autologous fat injection is relatively safe and easy to perform, and is an ideal method of temporary vocal fold medialization in patients in whom return of vocal fold function is expected.     

Phonosurgery of chronic vocal cord edema

INTRODUCTION: Chronic (Reinke's) oedema of the vocal folds is a frequent and declicate objective of phonosurgery. It is characterized by a marked bilateral subepithelial oedema, which develops by degrees, as a non-specific reaction of the vocal folds to various irritative noxious agents (especially smoking), in patients with some predisposition. It is found, by the light and electron microscopes and immunohistochemistry, that oedema is characterized by subepithelial fissure-like spaces, which accumulate a protein-rich fluid, and develops like neobursae. Therefore, mechanical factors and functional influences may also contribute to the development of Reinke's oedema. The voice is low pitched and with various degrees of hoarseness. Reinke's oedema alters the mechanical properties of the cover, which becomes very pliable and with reduced stiffness, incapacitating the vocal fold for production of high tones. Hoarseness is induced in subject with associated laryngitis, or disbalance in mechanical properties of the vocal folds. Hyperkinetic pattern of voice production can often be seen in patients with Reinke's oedema, which is a compensatory results of reduced functional capability of the vocal folds. Stroboscopy reveals a prolonged closed phase of the vibratory cycles and strikingly marked mucosal waves. MATERIAL AND METHOD: A series of 371 patients with Reinke's oedema was operated by direct microlaryngoscopy, under the general anaesthesia. The "excessive" mucosa was removed by bimanual micro-procedure, while the care was not taken to severe layers deeper than a superficial part of the intermediate layer of the vocal fold (Reinke's space). In this procedure we used the micro-forceps and scissors, to detach oedema parallel to the free edge of the vocal fold, at its upper and lower demarcation lines, beginning from the posterior part of oedema. Another 27 patients were operated by indirect procedures. Microstroboscopy (IMS) was used in subjects, while videostroboscopy (IVS) was carried out in another 18 patients. These procedures were used when general anaesthesia was contraindicated, and in patients with Reinke's oedema of the first degree (initial oedema). In these patients only a mucosal strip was removed from the upper surface of the vocal fold, apart from the free edge. Oedema was removed bilaterally, while the formation of the postoperative web was prevented by regular examinations of the patient. In several cases of adherence between the two folds in their anterior commissure, the problem was solved indirectly by the use of a curved forceps and under the topical anaesthesia. Postoperative voice rest and administration of steroids were mandatory. Surgical and functional results were followed-up by stroboscopy over the period of at least three years after surgery. The majority of patients were additionally treated by the voice therapy, while the decision about its use was made three weeks after surgery. RESULTS: Functional results of our therapeutic strategy were satisfactory in our series of 398 subjects with Reinke's oedema. In comparison with other benign lesions of the vocal folds, it was more time-consuming and required a more frequent use of the postoperative voice therapy (Table 1). Thus, we have not encountered recurrences. DISCUSSION: During the last 10 years we operated on 1550 patients with various benign lesions of the vocal folds, including 398 subjects with Reinke's oedema (25.7%). Excision of the "excessive" mucosa may appear today as a procedure which is too radical if compared with many techniques which have been offered during the last decades: conservative excision and suction, squeezing technique, laser. Nevertheless, the histological structure of Reinke's oedema, with subepithelial fissure-like spaces indicated that the latter procedures can hardly be expected to prevent recurrences. It was found that the use of laser was not favourable in this area for its deteriorative local effect.     

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.     

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.     

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.     

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.     

Vocal fold scarring: current concepts and management

Scarring of the vocal folds can occur as the result of blunt laryngeal trauma or, more commonly, as the result of surgical, iatrogenic injury after excision or removal of vocal fold lesions. The scarring results in replacement of healthy tissue by fibrous tissue and can irrevocably alter vocal fold function and lead to a decreased or absent vocal fold mucosal wave. The assessment and treatment of persistent dysphonia in patients with vocal fold scarring presents both diagnostic and therapeutic challenges to the voice treatment team. The common causes of vocal fold scarring are described, and prevention of vocal fold injury during removal of vocal fold lesions is stressed. The anatomic and histologic basis for the subsequent alterations in voice production and contemporary modalities for clinical and objective assessment will be discussed. Treatment options will be reviewed, including nonsurgical treatment and voice therapy, collagen injection, fat augmentation, endoscopic laryngoplasty, and Silastic medialization.     

Phonosurgical treatment of vocal cord cysts

INTRODUCTION: Functional-traumatic lesions of the vocal folds include mucous stranding, "nodular" lesions, polyps, cysts, contact hyperplasia and haematoma [1]. They all appear at the predilection sites of the vocal fold, at the junction between the anterior and middle thirds, slightly below the free edge. Vocal fold cysts are also located at the predilection site. They interfere with the glottic closure and vibration process. The treatment consists of surgical enucleation. This paper is aimed to present our results with direct and indirect surgical procedures. MATERIAL AND METHOD: A series of 63 vocal fold cysts was operated by the use of direct microlaryngoscopy (DML), indirect microlaryngoscopy (IMS) and videostroboscopy (IVCS). RESULTS: Over a 10-year period 1550 surgical procedures were performed for benign lesions of the vocal folds, including 63 cases of vocal fold cysts (4.1%). A very satisfactory phonusurgical result was obtained. Recovery of the vibration pattern was after DML procedures within 3 weeks in 66.6% of patients, while it was apparently faster after indirect operations. The latter were performed only for minor cystic lesions, and therefore direct and indirect procedures cannot be compared to vibration recovery. DISCUSSION: A careful surgical manipulation is required for the enucleation of vocal fold cysts, sparing the local tissue. DML is used in the majority of cases, while indirect procedures can be used only in minor lesions, where enucleation is not possible.     

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.     

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.     

Critical review of phonosurgical methods in the treatment of sulcus vocalis

INTRODUCTION: Sulcus vocalis is an epithelial invagination along the free edge of the membranous vocal fold. It interferes with the glottic closure and vibration pattern. Sulcus vocalis provokes voice fatigue, hoarseness and breathiness, and it usually appears in association with hyperkinetic phonatory pattern. Hyperkinesis develops secondarily, due to the compensatory effort to overcome the deficiency in glottic closure. The treatment of sulcus vocalis is very difficult. Phonosurgery is used, and is followed by postoperative voice therapy. PHONOSURGICAL OPERATIONS: Various surgical techniques are used in the therapy of sulcus vocalis. Over a 10-year period we have operated on 1550 patients with benign lesion of the vocal folds, of whom only 11 had sulcus vocalis (0.7%). We carried out various surgical techniques. a) Excision of sulcus A longitudinal incision of mucosa is performed along the upper surface of the vocal fold, distant of the free edge. Mucosa is undermined caudally, and sulcus is detached from its base. Sulcus is then removed by surgical scissors. With this technique we could not provide physiological phonation and vibration pattern, in spite of an apparent improvement in the voice. b) "Slicing mucosa" technique This procedure was suggested by Pontes, and it also begins with a longitudinal incision followed by creation of inferiorly based slices of mucosa. c) Excision plus rhyroplasty Excision of sulcus is combined with thyroplasty type I in order to achieve medialization of the vocal fold. It can be used in cases with severe glottal gap in order to improve the results of excision. d) Implants Various materials were used in order to enlarge the mass of the vocal fold. In our patients, the results of this procedure were inferior as related to excision surgery. DISCUSSION: The surgical procedure which is safe and accepted by the majority of surgeons has not yet been at our disposal. The treatment of sulcus vocalis should start with voice therapy, which lasts as long as the patient shows a progress. Only then the surgical procedure can be discussed. We obtained the best results with the combination of excision and voice therapy. However, the surgeon and the patient must be aware that the treatment is demanding and long-lasting.     

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.     

Assessment of vocal function using simultaneous aerodynamic and calibrated videostroboscopic measures

Despite many attempts to model how vocal fold movements relate to the aerodynamic forces acting on them during phonation, there have been few simultaneous measurements of glottal area and transglottal air pressures and flows. A novel system is described that combines endoscopic measurement of glottal area with aerodynamic flow and pressure measures made during phonation. Results from bench top model tests and from one human subject are presented. For both tests, an aerodynamic model of airflow through a constriction was used to predict the area of the constriction (glottis), and these predictions were compared with endoscopic measurements. The results showed good correlation between predicted and observed areas; however, for small constrictions (<0.025 cm2), whether artificial or glottal, the errors in estimating areas with either optical or aerodynamic methods increase significantly. These results suggest that this measurement system has the potential to enhance the assessment of vocal function.     

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.     

Pleiotropic functions of neurotrophins in development

Laryngeal framework surgery can change the position and tension of the vocal folds safely without direct surgical intervention in the vocal fold proper. Some 23 years of experience with phonosurgery have proved its usefulness in treating dysphonia related to unilateral vocal fold paralysis, vocal fold atrophy, and pitch-related dysphonias . Meanwhile, much information about the mechanism of voice production has been obtained through intraoperative findings of voice and fiberscopic examination of the larynx . Based on such knowledge together with information obtained through model experiments, the human vocal organ was reconsidered mainly from the mechanical view point, and the roles of voice therapy and singing pedagogy were discussed in relation to phonosurgery. The vocal organ may not be an ideal musical organ and is rather vulnerable, but its potential is enormous.     

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.     

Treatment of ventricular dysphonia with botulinum toxin

Ventricular dysphonia, traditionally known as dysphonia plica ventricularis, is a voicing disorder in which the false vocal folds are used as a vibratory source in addition to or instead of the true vocal folds. Traditional treatment of ventricular dysphonia has been voice therapy, which may be slow to produce results if the false fold activity masks an underlying problem of the true folds, is long standing, or has produced hypertrophy of the supraglottic structures. We present seven cases of ventricular dysphonia treated with botulinum toxin injection into the false vocal folds followed by speech therapy. The addition of botulinum toxin to the treatment regimen speeds recovery of normal voicing and allows immediate evaluation of dynamic true vocal fold function by the treating professional.     

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.     

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.