An automatic method to quantify mucosal waves via videokymography

Objective/Hypothesis: Vocal fold vibration is associated with four distinct vibratory patterns: those of the right‐upper, right‐lower, left‐upper, and left‐lower vocal fold lips. The purpose of this study was to propose a least squares method to quantify the vibratory properties of each of the four vocal fold lips via videokymography (VKG). Study Design: This was a methodological study designed to examine the impact of subglottal pressure and line‐scan position on mucosal wave parameters. Methods: VKG, a line‐scan imaging technique, has proven to be an effective method for studying vocal fold vibratory patterns. This study used VKG images and an automatic mucosal wave extraction method to examine the vibration of each individual vocal fold lip of 17 excised canine larynges under differing subglottal pressures and line‐scan positions. Results: Varying subglottal pressure led to results consistent with previous studies. Examination of the vocal folds at different line‐scan positions along its length revealed that amplitude is greatest at the midpoint of the vocal fold, followed by the anterior portion of the vocal fold, with the posterior portion having the lowest amplitude (P < .001). Frequency and phase delay did not change significantly throughout the length of the vocal fold. Conclusions: The method used in this study allows for easy determination of four sets of vibratory parameters, and examination of the effect of biomechanical parameters on vocal fold vibrations.     

Videostrobokymographic analysis of benign vocal fold lesions

OBJECTIVES: Videostrobokymography (VSK) has recently been introduced. The aim of this study was to analyze vibratory patterns and objective parameters in various benign vocal fold lesions using VSK and to examine the efficacy of VSK in clinical applications. MATERIAL AND METHODS: Using VSK, we analyzed the vibration patterns of normal vocal folds, various benign lesions such as nodules, polyps, cysts and Reinke's edema and cases of unilateral vocal fold paralysis. We also calculated the objective parameters open quotient and asymmetric index and compared them with their mean values in normal controls. RESULTS: In nodules, polyps and cysts, the open quotient at the site of the lesion was similar to the mean value in the normal controls; however, on the other parts of the vocal folds, it was much larger than the normal mean value. In Reinke's edema, irregular and asymmetric vibrations were observed. The posterior area of the vocal folds showed larger open quotients than the anterior area. In unilateral vocal fold paralysis, irregular vocal fold vibration and incomplete closure of the vocal folds were documented. Much larger asymmetric indices were calculated for unilateral vocal fold paralysis than in normal controls or for other lesions. The asymmetric index may be a good quantitative parameter of vibration in patients with vocal fold paralysis. CONCLUSION: This study demonstrated that VSK could generate clear quantitative documentation of fine vibrations of vocal folds in many different types of benign lesion. VSK has the potential to be an effective tool for the quantitative analysis of vibratory patterns of vocal folds in clinical settings.     

A new instrument for intraoperative assessment of individual vocal folds

OBJECTIVES: Intraoperative assessment of vocal fold vibration during phonomicrosurgery performed under general anesthesia may enhance surgical decision-making. We therefore developed and bench-tested a new device we refer to as the aerodynamic vocal fold driver (AVFD). MATERIALS AND METHODS: The AVFD comprises a hand-held probe that uses airflow to drive individual vocal folds into phonatory-like vibration. This permits stroboscopic visualization of mucosal waves with simultaneous control of subglottal air pressure. In initial experiments to validate the technique, AVFD driven phonation and conventional whole-larynx phonation were compared using excised canine larynges (n = 14). RESULTS: Single vocal fold phonation using the AVFD and whole larynx phonation yielded similar, positive correlations between subglottal pressure and both amplitude and frequency of vibration. Experiments simulating vocal fold scar-related mucosal stiffening by subepithelial injection of fixative showed the expected elevation of phonation threshold pressures as measured with the AVFD. Likewise, unilateral tissue compression injury disrupted vocal fold vibration, and the AVFD was useful for quantifying improvement in the damaged vocal fold after repair with injection of cross-linked hyaluronic acid gel. CONCLUSIONS: These results show that this new instrument has the potential to provide novel and useful information for laryngeal experimentation and to improve phonosurgery.     

Vocal fold injury following endotracheal intubation

Vocal fold scarring results in the formation of fibrous tissue which disturbs the vibratory pattern of the fold during phonation. However, vocal fold scarring in humans is poorly understood because of the lack of clear case reports focusing on voice quality. The authors present a case of vocal fold scarring with changes in voice quality. At the time of injury the pedicle mucosa was cemented with fibrin glue. Phonation was inhibited for two weeks and tranilast (300 mg/day) was given for 3 months. Sixty-nine days later, perceptual evaluation showed a normal result and the phonation time became better, but the mucosal vibration was still lacking. Ninety-seven days later, mucosal vibration was finally restored. We suggest that characterization of vocal fold scarring in humans may be different from that in animals, and recommend that surgical management should be avoided for at least three months after injury.     

Growth factor therapy for vocal fold scarring in a canine model

Vocal fold scarring remains a therapeutic challenge. Hepatocyte growth factor (HGF) has strong antifibrotic activity and has proved to have therapeutic potential in restoration of scar tissues such as liver cirrhosis and lung fibrosis. The present study aimed to clarify the effects of HGF injection into scarred vocal folds in a canine model. Canine vocal folds were stripped unilaterally and treated with intracordal injection of saline solution (sham group), HGF (HGF group), or HGF with cultured autologous normal vocal fold fibroblasts (Fb/HGF group) 1 month after injury. The larynges were harvested 6 months after the initial injury and then subjected to vibratory and histologic examination. The results of vibratory examinations in the excised larynx setup revealed that phonation threshold pressure significantly increased and vocal efficiency was significantly reduced in all treated groups as compared to normal data obtained from normal canine larynges. However, the HGF group presented much better results than both the sham and Fb/HGF groups in terms of mucosal wave amplitude and incidence of vocal fold bowing, glottal incompetence, and phase asymmetry. The histologic data indicated a significant increase of collagen in both the sham and Fb/HGF groups, while normal levels of collagen were found in the HGF group. Tissue contraction of the lamina propria was also observed in both the sham and Fb/HGF groups, but was barely detectable in the HGF group. Although the HGF-treated vocal folds appeared to require more driving forces for vibration, HGF might prevent excessive collagen deposition and tissue contraction and thus reduce the effects of scarring on the vibratory properties of the vocal folds. From these data it is concluded that HGF has considerable potential in the treatment of vocal fold scarring.     

Quantitative study of mucosal wave via videokymography in canine larynges

OBJECTIVES: Vocal fold mucosal wave movements are thought to be important in determining voice characteristics and quality. To see these movements, high-speed cinematography and videostroboscopy have been used clinically; however, these techniques have disadvantages that make them impractical for quantitative measurement of mucosal wave movements. This study explored the feasibility of using line-scan cameras for mucosal wave analysis. METHODS: An excised larynx bench model was used to examine the effects of elongation and changes in subglottal pressure on the amplitude, frequency, and phase difference of vocal fold mucosal movements as calculated from line-scan images. RESULTS: The data showed a positive and linear relationship between an increase in subglottal pressure and amplitude of the mucosal wave; elongation of the vocal folds appeared to decrease the amplitude of mucosal wave upheaval at each level of subglottal pressure. Similarly, increase in subglottal pressure had a positive and linear relationship with increase in frequency of vibration; elongation of the vocal folds further increased the frequency at any given subglottal pressure. Phase difference between the movements of the upper and lower margins of the mucosal lips was estimated and did not appear to be significantly affected by changes in subglottal pressure and elongation. CONCLUSION: The data presented in this study are consistent with relationships that we would expect to be true from currently accepted models of vocal fold vibration.     

An accurate method of Teflon injection using functional phonosurgery

A technique for Teflon injection is described that allows the laryngologist to assess vocal fold vibration during general anesthesia. A tracheostomy tube fitted with a rostral air line allows translaryngeal airflow. During endoscopy with a bivalved laryngoscope, the cords are approximated manually. Vocal fold vibration is produced with the cords adducted. The precise site of defects in glottic closure is clearly seen and corrected with Teflon injection. In cases where standard Teflon injection has failed, utilization of this method has allowed substantial voice improvement. The ability to assess vibratory function of the vocal folds during direct suspension laryngoscopy enhances the precision of vocal fold augmentation techniques in difficult rehabilitation cases.     

喉良性增生性病变的嗓音学特点及治疗转归

目的 :探讨喉良性增生性病变对发声功能的影响及CO2 激光显微外科术后的转归特点。方法 :对2 92例喉良性增生性病变患者 (声带息肉、任克水肿、声带小结、囊肿、慢性肥厚性喉炎 )的流行病学、嗓音声学、形态及CO2 激光显微外科术后转归进行分析。结果 :声带小结患者均为青年女性 ,2 3.0 8%与职业有关 ;任克水肿为中老年患者。声带息肉及小结病变局限 ,手术仅涉及声带局部 ,术后改善明显 ,术后 1个月达正常状态 ;任克水肿患者术后 1个月改善明显 ,术后 3个月恢复最佳稳定 ;声带囊肿患者术后 1个月声音达最佳状态 ,但由于病变切除术后局部存在缺损 ,一定程度上影响预后 ;慢性肥厚性喉炎患者术后改善不满意。术后声门上代偿纠正均不明显。结论 :喉良性增生性病变主要累及声带被覆层 ,嗓音声障碍的程度及疗效与受累范围有关 ,激光显微外科手术可以保留良好结构及功能。除外科治疗外 ,还应及时矫正不良发声习惯等因素 ,以期获得最佳疗效。     

Phonomicrosurgery II: surgical techniques

Optimal vocal outcome is the major goal of treatment of benign non-neoplastic vocal fold lesions. Current phonomicrosurgery techniques are based on a complete understanding of vocal fold anatomy and the physiology of vocal fold vibration. With the knowledge that these lesions typically involve the superficial layer of the lamina propria and not the overlying epithelium, dissection and excision should be limited to this layer. Vocal fold microflap techniques leave the overlying epithelium and the mucosal cover intact to minimize postoperative scarring and possible tethering to the underlying vocal ligament. Surgical excision is followed by a program of vocal rehabilitation.     

Videostrobokymographic Analysis of Benign Vocal Fold Lesions

Objectives—Videostrobokymography (VSK) has recently been introduced. The aim of this study was to analyze vibratory patterns and objective parameters in various benign vocal fold lesions using VSK and to examine the efficacy of VSK in clinical applications.

Material and Methods—Using VSK, we analyzed the vibration patterns of normal vocal folds, various benign lesions such as nodules, polyps, cysts and Reinke's edema and cases of unilateral vocal fold paralysis. We also calculated the objective parameters open quotient and asymmetric index and compared them with their mean values in normal controls.

Results—In nodules, polyps and cysts, the open quotient at the site of the lesion was similar to the mean value in the normal controls; however, on the other parts of the vocal folds, it was much larger than the normal mean value. In Reinke's edema, irregular and asymmetric vibrations were observed. The posterior area of the vocal folds showed larger open quotients than the anterior area. In unilateral vocal fold paralysis, irregular vocal fold vibration and incomplete closure of the vocal folds were documented. Much larger asymmetric indices were calculated for unilateral vocal fold paralysis than in normal controls or for other lesions. The asymmetric index may be a good quantitative parameter of vibration in patients with vocal fold paralysis.

Conclusion—This study demonstrated that VSK could generate clear quantitative documentation of fine vibrations of vocal folds in many different types of benign lesion. VSK has the potential to be an effective tool for the quantitative analysis of vibratory patterns of vocal folds in clinical settings.     

A methodological study of hemilaryngeal phonation

An excised hemilarynx setup was developed. The phonatory characteristics of nine excised canine larynges were examined. The left vocal fold of each larynx was then removed and substituted with a vertical plexiglass plate. The larynges were phonated again. Recordings were made of phonation threshold pressure, sound pressure level, average glottal flow, fundamental frequency, and amplitude of vocal fold vibration as observed with a video stroboscope. Measurements were made over a range of subglottal pressures. For the hemilarynx, simultaneous recordings of intraglottal pressure and vocal fold contact area were also made. It was found that amplitude and frequency of vocal fold vibration of the hemilarynx, as well as rates of change of amplitude and frequency as a function of subglottal pressure, were similar to those of the full larynx. Also similar were phonation threshold pressures and ranges of subglottal pressure over which the larynges phonated. The average airflow of the hemilarynx was approximately half that of the full larynx, and the sound pressure level, under similar conditions, was one fourth (about 6 dB less) in the hemilarynx.     

Study of vibratory pattern of the vocal folds in the excised canine larynx.

The effect of simulated thyroarytenoid and cricothyroid muscle contraction on the vibratory pattern of the vocal folds was studied in the excised canine larynx. To simulate the action of the thyroarytenoid muscle, small balloons were inflated in the paraglottic space at the level of the vocal folds. To simulate the action of the cricothyroid muscle, longitudinal tension was applied to the anterior commissure of the vocal folds. The photoglottographic and electroglottographic signals, sound intensity, and airflow rate were measured. This study showed that balloon inflation simulating thyroarytenoid muscle contraction produced an elevation of frequency of vibration with a decrease in open quotient, and that an increase in longitudinal tension simulating cricothyroid muscle contraction produced an elevation of frequency with an increase in open quotient. Vocal resistance decreased with increasing open quotient, amplitude of the photoglottographic waveform, and the frequency of vibration. Vocal efficiency increased with increasing photoglottographic amplitude and decreased with increasing frequency. The vocal efficiency peaked when the open quotient was approximately 0.5. This study suggests that glottographic parameters may be useful in assessing the effect of intrinsic laryngeal muscle activity on vocal efficiency and glottic resistance.     

Measurement of vocal fold collision forces during phonation: methods and preliminary data.

Forces applied to vocal fold tissue as the vocal folds collide may cause tissue injury that manifests as benign organic lesions. A novel method for measuring this quantity in humans in vivo uses a low-profile force sensor that extends along the length and depth of the glottis. Sensor design facilitates its placement and stabilization so that phonation can be initiated and maintained while it is in place, with minimal interference in vocal fold vibration. In 2 individuals with 1 vibrating vocal fold and 1 nonvibrating vocal fold, peak collision force correlates more strongly with voice intensity than pitch. Vocal fold collision forces in 1 individual with 2 vibrating vocal folds are of the same order of magnitude as in previous studies. Correlations among peak collision force, voice intensity, and pitch were indeterminate in this participant because of the small number of data points. Sensor modifications are proposed so that it can be used to reliably estimate collision force in individuals with 2 vibrating vocal folds and with changing vocal tract conformations.     

High-speed imaging used to detect vocal fold paresis: a case report

High-speed imaging has been used to study vocal fold vibration and has been shown to provide additional information in aid of our understanding of pathologic vocal fold vibration. This is the first case report of vocal fold paresis diagnosed by high-speed imaging. An 18-year-old girl presented with intermittent voice loss that had been present for 4 years. The patient had been seen by other otolaryngologists and had been given proton pump inhibitors without any improvement in her voice. Her voice was diplophonic. The patient was examined by rigid stroboscopy and was found to have a predominantly open phase pattern but a normal vibratory pattern. High-speed photography showed a distinct vibratory frequency for each vocal fold, suggestive of a paresis pattern. Laryngeal electromyography confirmed the diagnosis of vocal fold paresis. A computed tomographic scan of the larynx and chest showed a thymoma. After thymectomy, the patient recovered full voice function. High-speed imaging is useful for the clinical evaluation of pathologic vocal fold vibration and can detect subtle features of paralysis that may not be detected on fiberoptic endoscopy and rigid stroboscopy. The additional information from high-speed imaging helped to make the diagnosis of vocal fold paresis in this patient.     

Prevention of vocal fold scarring by topical injection of hepatocyte growth factor in a rabbit model

OBJECTIVES/HYPOTHESIS: Vocal fold scarring disrupts the layer structure of the vocal fold lamina propria that is essential for optimal mucosal vibration. Prevention of vocal fold scarring remains challenging. Hepatocyte growth factor (HGF) has strong antifibrotic activity. The authors' previous studies have found that HGF stimulates hyaluronic acid production and suppresses collagen production from vocal fold fibroblasts, suggesting that HGF has therapeutic potential in prevention of vocal fold scarring. The present study aimed to demonstrate the effects of HGF on vocal fold scarring in an in vivo rabbit model. STUDY DESIGN: Animal experiment. METHODS: The vocal fold mucosa was stripped unilaterally in 20 rabbits, then HGF or saline (sham-treated group) was immediately injected into the injured site. At 6 months after the procedure, histological, rheological, and physiological examinations of vibratory behavior were completed. RESULTS: Histological examination revealed excessive collagen deposition and disorganized elastin in the sham-treated group, whereas the HGF-treated group presented with better wound healing exhibiting less collagen deposition. Contraction of the injured vocal folds observed in the sham-treated group did not occur in the HGF-treated group. Rheological data indicated that the HGF-treated vocal folds were less stiff and viscous compared with the sham-treated group. Mucosal vibration of HGF-treated vocal folds appeared much better than the sham-treated group in terms of phonation threshold pressure, vocal efficiency, mucosal wave amplitude, and glottal closure. CONCLUSION: Hepatocyte growth factor proved to be useful in preventing vocal fold scarring and maintaining viscoelastic shear properties of the vocal fold.     

Drug delivery system of hepatocyte growth factor for the treatment of vocal fold scarring in a canine model

OBJECTIVES: Vocal fold scarring remains a therapeutic challenge. Previous studies have indicated that hepatocyte growth factor (HGF), a strong antifibrotic element, has therapeutic potential for restoring scarred vocal folds. To enhance the effect of HGF in vivo, we developed a novel drug delivery system (DDS) in which HGF is embedded in gelatin hydrogel and continuously released over a period of 2 weeks. In the present study we investigated the therapeutic efficacy of the HGF DDS on vocal fold scarring by using a canine model. METHODS: The vocal folds of 8 beagles were unilaterally scarred by stripping the entire layer of the lamina propria. The contralateral vocal folds were kept intact as normal controls. One month after the procedure, hydrogels (0.5 mL) containing 1 microg of HGF were injected into the scarred vocal folds of 4 dogs (HGF-treated group), whereas hydrogels containing saline solution were injected in the other 4 dogs (sham group). Histologic and vibratory examinations were completed for each group 6 months after the initial surgery. RESULTS: The excised larynx experiments showed significantly better vibration in terms of mucosal wave amplitude and glottal closure in the HGF-treated group compared to the sham group. Histologic evaluation of the vocal folds indicated remarkable reduction in collagen deposition and tissue contraction, with favorable restoration of hyaluronic acid and elastin in the HGF-treated group. CONCLUSIONS: The present findings suggest that the novel HGF DDS may provide favorable effects in restoring the vibratory properties of scarred vocal folds.     

Histopathologic investigations of the unphonated human vocal fold mucosa

CONCLUSION: Vocal fold vibration (phonation) after birth is one of the important factors in the growth and development of the human vocal fold mucosa. OBJECTIVES: Stellate cells in the maculae flavae located at both ends of the vocal fold mucosa are inferred to be involved in the metabolism of extracellular matrices. Maculae flavae are also considered to be an important structure in the growth and development of the human vocal fold mucosa. Tension caused by phonation (vocal fold vibration) is hypothesized to stimulate stellate cells to accelerate production of extracellular matrices. Vocal fold mucosae unphonated since birth were investigated histologically. SUBJECTS AND METHODS: Vocal fold mucosae, which were unphonated since birth, of three younger adults (17, 24, 28 years old) were investigated by light and electron microscopy. RESULTS: Vocal fold mucosae were hypoplastic and rudimentary and did not have a vocal ligament, Reinke's space or a layered structure. The lamina propria appeared as a uniform structure. Some stellate cells in the maculae flavae showed degeneration. Not many vesicles were present at the periphery of the cytoplasm. The stellate cells synthesized fewer extracellular matrices, such as fibrous protein and glycosaminoglycan. Cytoplasmic processes of the stellate cells were short and shrinking. The stellate cells appeared to have decreased activity.     

Vocal fold epithelial hyperplasia. Vibratory behavior vs extent of lesion

The vibratory behavior of 72 vocal folds with epithelial hyperplasia or dysplasia was investigated by means of videostroboscopy. The amplitude of vibration (AMP) and mucosal wave (WAV) were related to the relative area, depth, and relative volume of the lesion. The AMP and WAV were evaluated for the entire vocal fold (AMPE, WAVE) and for the affected portion or the lesion (AMPL, WAVL). The AMPE, AMPL, WAVE, and WAVL were negatively related to the relative area, depth, and relative volume. The relationship between the limited vibratory movement and the extent of the lesion was most significantly manifested in WAVL. A complete absence of any vibratory movement of the vocal fold took place only for large lesions occupying three fourths or more of the membranous vocal fold.     

Upper displacement of the anterior commissure: experimental study of a new phonosurgical approach to raising vocal pitch

OBJECTIVES: The present study assessed the effects of a unique pitch-raising surgical technique designated upper displacement of the anterior commissure (UDAC), comparing the results with those obtained through cricothyroid approximation (CTA). METHODS: Vocal fold vibration was artificially evoked in 20 excised human larynges through tracheal injection of compressed air. Vocal fold length, fundamental frequency, and videokymography parameters were determined preoperatively, post-CTA, and post-UDAC. In UDAC, a bilateral incision was made between the middle and anterior thirds of the thyroid cartilage. The inferiormost portion of the anterior thyroid cartilage (anterior to the cartilaginous incision) was sutured to the superiormost portion of the posterior thyroid cartilage (posterior to the cartilaginous incision). The anterior commissure was thus moved upward and forward, ensuring increased vocal fold tension. RESULTS: The mean vocal fold length was 16.88 mm preoperatively, 20.02 mm post-CTA, and 18.67 mm post-UDAC (p < .05). The mean fundamental frequency was 151.60 Hz preoperatively, 271.10 Hz post-CTA, and 239.30 Hz post-UDAC (p < .05). The post-CTA and post-UDAC vibration amplitudes were significantly lower than the preoperative values (p < .05). CONCLUSIONS: Vocal fold length and fundamental frequency increased significantly after UDAC (p < .05), although to a lesser degree than after CTA.     

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.