Effect of vocal fold augmentation on laryngeal vibration in simulated recurrent laryngeal nerve paralysis: a study of Teflon and Phonogel

Destiny of autologous bone marrow-derived stromal cells implanted in the vocal fold

OBJECTIVES

The aim of this study was to investigate the destiny of implanted autologous bone marrow-derived stromal cells (BSCs) containing mesenchymal stem cells. We previously reported the successful regeneration of an injured vocal fold through implantation of BSCs in a canine model. However, the fate of the implanted BSCs was not examined. In this study, implanted BSCs were traced in order to determine the type of tissues resulting at the injected site of the vocal fold.

METHODS

After harvest of bone marrow from the femurs of green fluorescent transgenic mice, adherent cells were cultured and selectively amplified. By means of a fluorescence-activated cell sorter, it was confirmed that some cells were strongly positive for mesenchymal stem cell markers, including CD29, CD44, CD49e, and Sca-1. These cells were then injected into the injured vocal fold of a nude rat. Immunohistologic examination of the resected vocal folds was performed 8 weeks after treatment.

RESULTS

The implanted cells were alive in the host tissues and showed positive expression for keratin and desmin, markers for epithelial tissue and muscle, respectively. The implanted BSCs differentiated into more than one tissue type in vivo.

CONCLUSIONS

Cell-based tissue engineering using BSCs may improve the quality of the healing process in vocal fold injuries.

Regeneration of the vocal fold using autologous mesenchymal stem cells

The aim of this study was to regenerate the injured vocal fold by means of selective cultured autologous mesenchymal stem cells (MSCs). Eight adult beagle dogs were used for this experiment. Selective incubation of MSCs from bone marrow was done. These MSCs were submitted to 3-dimensional incubation in 1% hydrochloric acid atelocollagen. Three-dimensional incubated MSCs were injected into the left vocal fold, and atelocollagen only was injected into the right vocal fold of the same dog as a control. Four days after injection, the posterior parts of the vocal folds were incised. The regeneration of the vocal fold was estimated by morphological and histologic evaluations. Our results showed that 3-dimensional incubated MSCs were useful in the regeneration of the injured vocal fold. This study shows that damaged tissues such as an injured vocal fold would be able to be regenerated by tissue engineering.

Effect of recurrent laryngeal nerve paralysis on superior laryngeal nerve afferents during evoked vocalization

We tested the hypothesis that vocal fold paresis leads to a substantial reduction in activity from the internal branch of the superior laryngeal nerve (iSLN) during respiration and evoked vocalization. The iSLN afferent activity was measured before and after recurrent laryngeal nerve paresis by cold block in decerebrate cats during spontaneous respiration and electrically evoked vocalization. Response rate patterns of 33 iSLN single units from 11 cats were categorized into 5 groups based on responses to vocalization. Only 24% of single units during spontaneous respiration and 18% during evoked phonation displayed activity pattern changes as a result of paresis. Those fibers affected were heterogeneous in discharge pattern, but none of the units that followed voice frequency lost this characteristic when the motor nerve was cooled. The relative insensitivity of iSLN activity to motor paralysis suggests that the receptors studied are coupled to tissue such that passive interaction rather than active muscular contraction is the major stimulus.

Internal superior laryngeal nerve afferent activity during respiration and evoked vocalization in cats

The purpose of this project was to identify and categorize patterns of activity of the internal branch of the superior laryngeal nerve during vocalization evoked by midbrain stimulation in cats anesthetized with alpha-chloralose. Unit activity was isolated from the cut distal end of the internal branch of the superior laryngeal nerve by means of floating bipolar electrodes that retained their contact with nerve fibers despite movement due to vocalization. The phases of respiration and vocalization were determined with a diaphragm electromyogram, a photoglottogram, and a microphone recording. Five groups of discrete afferent activities were defined according to relationships between the spike activity and the phases of vocalization. Group 1 cell activity peaked just before phonation, during expiratory airflow (n = 26). Group 2 cells (n = 19) followed a vocal fold vibratory pattern during phonation. Group 3 cell activity (n = 6) peaked during phonation, but did not follow vocal fold vibration. Group 4 cells (n = 3) were active during inspiration between phonations. Group 5 cells (n = 4) showed both inspiratory and expiratory modulation. These results indicate that laryngeal afferent activity responds to phonation-specific events during vocalization. This stereotyped afferent information might be used by the central nervous system to modulate vocalization.

Laryngeal reinnervation with the hypoglossal nerve. I. Physiology, histochemistry, electromyography, and retrograde labeling in a canine model

This study was performed to determine whether the hypoglossal nerve (cranial nerve XI [XII]) would serve as a useful donor for laryngeal reinnervation by anastomosis to the recurrent laryngeal nerve (RLN). Twenty hemilarynges in 10 dogs were studied prospectively after XII-RLN anastomosis (group A; n = 5), split XII-RLN anastomosis (group B; n = 3), XII-RLN anastomosis with a 2-cm interposition graft (group C; n = 2), no treatment (group D; n = 5), RLN section (group E; n = 2), or ansa cervicalis-RLN anastomosis (group F; n = 3). Spontaneous activity was observed monthly by infraglottic examination through permanent tracheostomies and was recorded by electromyography. Laryngeal adductory pressure and induced phonation were obtained by stimulating the RLN while passing a pressure transducer balloon or humidified air through the glottis. At sacrifice, the laryngeal muscles were stained for adenosine triphosphatase to determine the ratio of type I to type II fibers. Retrograde labeling of the brain stem was performed with horseradish peroxidase. Infraglottic examination at 6 months showed a full range of adductory motion in groups A and B during the swallow reflex, comparable with that in group D. Groups C and F showed good bulk and tone, but little spontaneous motion. Group E remained paralyzed. Stimulation of the transferred nerves caused more activity in groups A and B than in the other groups; groups C and F partially adducted at high levels. The laryngeal adductory pressure responses of groups A and B were similar to those of group D. The XII-reinnervated larynges were capable of producing normal induced phonation. Retrograde labeling of the RLN showed that the reinnervating axons originated only in the hypoglossal nucleus. Electromyography of the reinnervated adductor muscles confirmed spontaneous activity in the dogs (awake). Histochemical analysis confirmed slow-to-fast transformation of both the posterior and lateral cricoarytenoid muscles, indicating that significant reinnervation occurred. We conclude that the hypoglossal nerve functions well as a donor for adductory reinnervation of the larynx.

Homologous Collagen Substances for Vocal Fold Augmentation

OBJECTIVES/HYPOTHESIS

Dysphonia resulting from failure of glottic closure during voicing is a difficult clinical problem. Recently developed homologous collagen compounds may be beneficial in treating this problem. The objectives of this thesis are to: 1) evaluate the potential site(s) of collagen graft placement in the human vocal fold, quantify the amount of graft material that can be injected into these sites, and determine how these sites are accessed by the currently available surgical tools for injection; 2) determine the effects of the superficial vocal fold implant on laryngeal vibratory patterns and characterize how the implant affects the forces required to bring vocal folds into an adducted position for vibration; and 3) evaluate the host response to two different forms of cadaveric collagen.

STUDY DESIGN

Prospective laboratory.

METHODS

Three separate experiments were undertaken: 1) Eight cadaver larynges were injected with collagen compounds through a 27-gauge needle. The amount of substance required to medialize the vocal fold and potential positions for graft placement were evaluated. 2) Six cadaver larynges were mounted on a stabilizing stand while airflow, vocal fold length, adduction forces, and abduction forces on the vocal folds were manipulated. Vibratory patterns before and after the injection of the vocal folds with solubilized collagen were assessed. 3) A nude mouse model was used to study the host response to two different exogenous collagen compounds.

RESULTS

Solubilized collagen compounds could be injected reliably into the superficial layer of the lamina propria (SLLP), medial portion of the thyroarytenoid muscle, or lateral portion of the thyroarytenoid muscle. When injected superficially, significantly less material was required to displace the medial edge of the vocal fold to midline (P =.0001). When graft material was placed into the medial portion of the thyroarytenoid (TA) muscle, the forces required to bring the vocal fold into a position suitable for vibration were significantly reduced (P =.0106) and the vibratory patterns of the vocal folds were not impaired. Both AlloDerm(R) and Dermalogen(R) solubilized preparations of human dermal tissue were well tolerated in the nude-mouse model. Minimal inflammatory reaction occurred. Small amounts of graft material were identified histologically at the end of the 6-month study period. The graft material appeared organized and had been infiltrated with fibroblasts of host origin.

CONCLUSIONS

Homologous collagen compounds can be reliably injected into the cadaveric human larynx. When the substances are injected into the medial portion of the TA muscle, immediately deep to the vocal ligament, they decrease the force of contraction needed to bring the vocal folds into a position adequate for phonation and have minimal affect on the vibratory patterns. These forms of homologous collagen are well tolerated. A small amount persists over a 6-month interval. These materials warrant further clinical trials in human subjects.

Effects of thyroplasty type I on vocal fold vibration

OBJECTIVE

To ascertain effects of medialization thyroplasty on vocal fold vibration in glottic incompetence dysphonia.

STUDY DESIGN

Quantitative videostroboscopic glottic measurements and vocal function study were perioperatively undertaken in 20 patients undergoing Isshiki's thyroplasty type I.

METHODS

In digitized images, the glottal area, glottal width, posterior glottal width, and amplitude over an entire glottal cycle were measured and normalized by membranous vocal fold length. The ratio of closed phase to total phase of vibratory cycle was calculated from the data of the glottal area and the glottal width at the middle point of the membranous vocal fold. Well-accepted acoustic, aerodynamic, and perceptual measures analyzed vocal function.

RESULTS

Glottal area and glottal width were reduced after surgery. While preoperative closure of glottal area was incomplete in all 20 patients, incomplete closure was obtained in 16 patients after surgery. In these 16 patients, closure of glottal width at the middle point of the membranous vocal fold was complete, whereas a posterior glottal gap remained in 14 patients. Closed phase over one cycle of glottal width waveform and amplitude of vocal fold vibration were increased after surgery. Glottal area, glottal width, posterior glottal width, and closed phase over one cycle of glottal width waveform correlated with vocal function measures.

CONCLUSIONS

Thyroplasty type I reduces a glottal gap and increases closed phase over one cycle and amplitude of vocal fold vibration, although a posterior glottal gap remains. With the improved glottic vibration, thyroplasty type I provides more efficient phonation in patients with glottic incompetence dysphonia.

Glottographic phase difference in recurrent nerve paralysis

Phase measures with simultaneously recorded electroglottography (EGG) and photoglottography (PGG) signals have been studied in canine models and found to be sensitive to the effect of recurrent laryngeal nerve (RLN) paralysis on vocal fold vibration. This study examined the usefulness of this type of measure in clinical application. The combined glottographic signals were obtained from 5 men with a diagnosis of unilateral RLN paralysis and 5 age-matched controls. In the patient group, EGG waveforms were found to have a consistent phase delay in relation to PGG. A measure of the overall glottographic phase difference (GPD) was found to significantly distinguish the control group (mean GPD = 0.2371 ms) from the patient group (mean GPD = -0.2765 ms). A validity analysis performed on 19 subjects with or without unilateral RLN paralysis confirmed that the GPD test had a relatively high efficiency (91.7%) in detecting unilateral RLN paralysis in the male population.

Integrated analyzer and classifier of glottographic signals

Electroglottography (EGG) and photoglottography (PGG) are two plausible methods to study voice production for monitoring the patterns of laryngeal vibrations. It has been suggested that measures such as open quotient and speed quotient calculated from glottographic signals can provide useful information regarding pathological phonation. In this paper, an integrated analyzer and classifier of glottographic signals was implemented. The system makes it possible to calculate the measures from digitized EGG and PGG signals automatically in order to examine vocal fold abnormality. The system developed several techniques to extract features from glottographic signals and proposed a statistical classification method that can possibly aid the diagnosis process. To check the reliability of the system, a training set and a test set of glottographic signals from normal people and patients with recurrent/superior laryngeal paralysis were analyzed and classified by the system. The results showed that the system is a useful tool for quantitative study of phonatory pathophysiology and can be used by the examiner who is interested in the clinical examination of glottographic signals. Moreover, glottographic techniques may have some clinical applications in the quantitative documentation of phonatory function in patients with voice disorders but requires further evaluation before clinical application.

A comparison of type I thyroplasty and arytenoid adduction

Glottal incompetence is a common laryngeal disorder causing impaired swallowing and phonation. The resultant voice has been characterized as weak and breathy with a restricted pitch range. Currently, medialization thyroplasty and arytenoid adduction are two of the surgical treatments for patients with glottal incompetence. However, few studies have evaluated the changes in objective measures of speech with type I thyroplasty and arytenoid adduction. In this study, 59 patients with glottal incompetence underwent either type I thyroplasty or arytenoid adduction. Acoustic (jitter, shimmer, and harmonics-to-noise ratio) and aerodynamic (airflow, subglottic pressure, and glottal resistance) measures were obtained both pre- and postoperatively. No significant differences were found among acoustic or aerodynamic measures for operation type. However, a significant pre/postsurgery effect was observed for translaryngeal airflow. In addition, no significant differences were found among the measures for patients with traditional compared with nontraditional operative indications. Patients who developed glottal insufficiency due to previous laryngeal surgery (e.g., vocal fold stripping) demonstrated no statistically significant improvement in acoustic or aerodynamic measures following thyroplasty or arytenoid adduction.

An analysis of vocal cord paralysis before and after Teflon injection using combined glottography

Combined glottography shows clinical potential but has only had limited use in monitoring laryngeal function before and after surgery. Eight patients undergoing Polytetrafluoroethylene (Teflon) injection for unilateral vocal cord palsies had pre- and post-operative combined glottography performed. Grossly abnormal waveforms pre-operatively confirmed poor glottic closure and irregular vibratory cycles. Analysis was difficult. Post-operatively all patients had a marked improvement in voice. Combined glottography showed a clear recovery of the waveforms towards normal with resumption of the two-mass model of glottal movement. Analysis was greatly simplified. Objective records were produced.

Function of the posterior cricoarytenoid muscle in phonation: in vivo laryngeal model

The function of the posterior cricoarytenoid (PCA) muscle in phonation has not been well documented. To date, several electromyographic studies have suggested that the PCA muscle is not simply an abductor of the vocal folds, but also functions in phonation. This study used an in vivo canine laryngeal model to study the function of the PCA muscle. Subglottic pressure and electroglottographic, photoglottographic, and acoustic waveforms were gathered from five adult mongrel dogs under varying conditions of nerve stimulation. Subglottic pressure, fundamental frequency, sound intensity, and vocal efficiency decreased with increasing stimulation of the posterior branch of the recurrent laryngeal nerve. These results suggest that the PCA muscle not only acts to brace the larynx against the anterior pull of the adductor and cricothyroid muscles, but also functions inhibitorily in phonation by controlling the phonatory glottal width.

Precise vocal cord medialization using an adjustable laryngeal implant: a preliminary study

Treatment of symptomatic unilateral vocal cord paralysis is most frequently surgical. Medialization of the vocal cord using Teflon injection has proved effective; however, studies have shown this technique to produce stiffness of the vocal fold with loss of the "mucosal wave" and concomitantly poor vocal function. As well, overcorrection may occur and is not reversible. Isshiki type 1 medialization thyroplasty has been shown to produce a substantial improvement in vocal quality, as well as preserve the mucosal wave. A number of problems encountered during the performance of Isshiki type 1 thyroplasty has led us to modify the original technique. We have developed a new implant that allows for precise, easily adjustable control of vocal cord medialization. To evaluate the degree of vocal cord medialization afforded by this implant, larynges of fresh male and female cadavers were used as an experimental model. In both larynges, vocal cord medialization was shown to occur in a predictable fashion for the anterior, middle, and posterior segments, as well as in the functionally important inter-arytenoid region. We believe the use of this implant in medialization thyroplasty will allow precise, atraumatic medialization of the paralyzed vocal cord. This greater control over positioning and ease of adjustment should contribute to enhanced vocal quality.

Correlation between stroboscopy and electromyography in laryngeal paralysis

Twenty patients with vocal fold motion impairment were reviewed to correlate the findings of electromyography (EMG) and stroboscopy. The causes of motion impairment were idiopathic, previous surgery with recurrent laryngeal nerve injury, neck and skull base trauma, and neoplasm. The EMG studies were analyzed to assess the status of innervation of the immobile vocal fold. The presence or absence of the mucosal wave prior to therapeutic intervention was determined with stroboscopic examination. Eight of 10 patients with EMG evidence of reinnervation or partial denervation were found to have mucosal waves, and 3 of 10 patients with EMG evidence of denervation were found to have mucosal waves. Six patients developed mucosal waves after surgical medialization, despite evidence of denervation by EMG criteria. These findings support the premise that tension and subglottic pressure, rather than status of innervation, determine the presence of the mucosal wave.

Teflon vocal fold augmentation: failures and management in 28 cases

Although vocal fold augmentation by Teflon injection has been the mainstay of treatment for glottic insufficiency for three decades, the success and safety of this treatment have been overstated. Twenty-eight patients who manifested poor or complicated Teflon results between 1984 and 1991 were evaluated using acoustic, aerodynamic, videostroboscopic, perceptual, and subjective patient self-evaluation of voice, both before and after our management of these complications. Most of these had Teflon granulomas; subglottic overfilling was the most common condition. In most instances such management included microsurgical removal of the Teflon granuloma. Voice measures that were abnormal before correction tended to improve and move into the normal range, although the resultant voices were not totally normal. Degree of improvement varied depending on the Teflon-induced tissue changes and the methods of correction subsequently used. The worst results were in patients with scarring, atrophy, and bilaterally mobile vocal folds, for whom Teflon should never have been injected. Teflon injection should be reserved for those instances in which it is clearly indicated and the surgeon is skilled in the technique of intrafold injection.

Measurement of Young's modulus in the in vivo human vocal folds

Currently, surgeons have no objective means to evaluate and optimize results of phonosurgery intraoperatively. Instead, they usually judge the vocal folds subjectively by visual inspection or by listening to the voice. This paper describes a new device that measures Young's (elastic) modulus values for the human vocal fold intraoperatively. Physiologically, the modulus of the vocal fold may be important in determining the nature of vocal fold vibration in normal and pathologic states. This study also reports the effect of recurrent laryngeal nerve stimulation on Young's modulus of the human vocal folds, measured by means of transcutaneous nerve stimulation techniques. Young's modulus increased with increases in current stimulation to the recurrent laryngeal nerve. Ultimately, Young's modulus values may assist surgeons in optimizing the results of various phonosurgeries.

Effect of asymmetric vocal fold stiffness on traveling wave velocity in the canine larynx

The vocal fold (VF) traveling wave is essential to normal voice production. The present investigation describes a new method to determine traveling wave velocity (TWV) in the in vivo canine phonatory model. This method synchronizes photoglottographic and electroglottographic waveforms with videostroboscopic images to determine the duration of time the traveling wave moves between two tattoos placed a known distance apart between the upper and lower margins of each VF. Using this method, we compared the TWV of a paralyzed VF with the TWV of the contralateral, electrically stimulated VF during phonation in two canines. In addition, the presumed VF stiffness asymmetry in the simulated acute recurrent laryngeal nerve paralysis state was confirmed by measuring Young's modulus of each VF. The results indicated that the TWV of the paralyzed VF averaged 55% of the TWV of the normal, stiffer VF when the glottal gap was small and entrainment occurred. This study demonstrated the feasibility of quantifying traveling wave motion in asymmetric VF stiffness disorders. The potential use of TWV in human beings as a target to optimize the phonosurgical results in asymmetric VF stiffness disorders is discussed.

Role of injectable collagen in the treatment of glottic insufficiency: a study of 119 patients

Injectable bovine collagen has been used for treatment of glottic insufficiency at the University of Wisconsin Clinical Science Center since 1983. This report reviews our experience in treating 119 patients with a variety of vocal fold disorders manifested by glottic insufficiency. Many of the patients were referred because of prior treatment failures or problems that were impossible to treat with other modalities. Results were assessed by comprehensive voice evaluations using subjective patient self-assessments, perceptual judgments made by a panel of experts who had no prior knowledge of the study, objective assessments, and videostroboscopy. Objective assessment included vocal function measures and acoustic analysis. Results indicate that collagen not only is comparable to other injection filler substances but also has unique advantages as a bioimplant. Collagen injection seems uniquely suited for treatment of several problems, including vocal fold atrophy, focal defects, minimal glottic insufficiency, and scarred vocal folds that are not managed optimally with Teflon injection. Overall there were no serious complications and treatment was effective for a broad spectrum of problems. In most instances the correction persisted, and in those instances in which injected collagen seemed improperly distributed, the vocal fold was recontoured or the implant removed without appreciable damage to the surrounding tissues. Injectable collagen has been extensively studied and deserves to be included in the armamentarium of the laryngeal surgeon.

Further morphologic studies on collagen injected into canine vocal folds

We compared the morphologic fate of three types of soluble bovine collagen injected into vocal folds of dogs: 1) Zyderm collagen implant containing 35 mg/mL of collagen (ZCI I), 2) Zyderm collagen implant containing 65 mg/mL of collagen (ZCI II), and 3) GAX collagen containing 35 mg/mL of collagen minimally cross-linked with 0.0075% glutaraldehyde. Light and electron microscopy showed good host tolerance and a long-term persistence of the three types of collagen at the site of injection. The collagen implants were progressively colonized by fibroblasts and capillaries accompanied by host collagen deposition. No inflammatory process or foreign body reaction occurred, in contrast to the typical host reaction to injected Teflon. The colonization of GAX collagen was slower than for ZCI I and ZCI II. No other significant difference was evident among the three types of injectable collagen. All three appear to be very suitable materials for laryngeal implants; moreover, they seem to best meet accepted requirements for a good implant: they are easy to inject, they are well tolerated, and they persist for a long time. We prefer GAX collagen for clinical use because of its lower reactivity and higher stability, and because overinjection is not necessary (GAX shrinks less than ZCI I and ZCI II).

Vocal fold medialization by surgical augmentation versus arytenoid adduction in the in vivo canine model

There are a variety of methods for treating unilateral vocal cord paralysis, but to date there have been few studies that compare these phonosurgical techniques by using objective measures of voice improvement. Vocal efficiency is an objective voice measure that is defined as the ratio of the acoustic power produced by the larynx to the subglottic air power. Vocal efficiency has been found to decrease with glottic disorders such as vocal cord paralysis and carcinoma. This study compared the effects of vocal fold medialization by surgical augmentation to those of arytenoid adduction on the vocal efficiency, videostroboscopy, and acoustics (jitter, shimmer, and signal-to-noise ratio) of a simulated unilateral vocal cord paralysis in an in vivo canine model. Arytenoid adduction was superior to surgical augmentation in vocal efficiency, traveling wave motion, and acoustics.

The effects of phonosurgery on laryngeal vibration: Part I. Theoretic considerations

Surgical manipulation of the laryngeal framework (phonosurgery) is rapidly gaining interest and attention. To date, however, a comparative objective evaluation of the various phonosurgical techniques has not been reported. A theoretic model of the larynx, a four-mass model based on the work of Ishizaka (J Acoust Soc Am 1976;60:1193-8) and Koizumi et al. (J Acoust Soc Am 1987;82:1179-92), was developed and adapted to simulate laryngeal biomechanical behavior, as understood by current research. The model was then applied to a comparative evaluation of phonosurgical techniques. Input parameters that correlate laryngeal function and model simulation were developed. Surgical procedures were categorized according to their effect on these parameters. A model simulation of these techniques allowed comparison and prediction of the results of phonosurgery and a better understanding of the issues involved with surgical alteration of the voice.