Deviant Vocal Fold Vibration as Observed During Videokymography: The Effect on Voice Quality

Videokymographic images of deviant or irregular vocal fold vibration, including diplophonia, the transition from falsetto to modal voice, irregular vibration onset and offset, and phonation following partial laryngectomy were compared with the synchronously recorded acoustic speech signals. A clear relation was shown between videokymographic image sequences and acoustic speech signals, and the effect of irregular or incomplete vocal fold vibration patterns was recognized in the amount of perceived breathiness and roughness and by the harmonics-to-noise ratio in the speech signal. Mechanisms causing roughness are the presence of mucus, phase differences between the left and right vocal fold, and short-term frequency and amplitude modulation. It can be concluded that the use of simultaneously recorded videokymographic image sequences and speech signals contributes to the understanding of the effect of irregular vocal fold vibration on voice quality.     

Changes in Vocal Fold Morphology During Singing Over Two Octaves

ObjectiveVocal folds are widely assumed to only elongate to raise vocal pitch. However, the mechanisms seem to be more complex and involve both elongation and tensioning of the vocal folds in series. The aim of the present study was to show that changes in vocal fold morphology depend on vocal fold elongation and tensioning during singing.Study designThis was a prospective study.MethodsForty-nine professional female singers (25 sopranos, 24 altos) were recruited and three-dimensional laryngeal images analyzed in a coronal view derived from high-resolution computed tomography scans obtained at the mean speaking fundamental frequency (ƒ₀) and one (2ƒ₀) and two octaves (4ƒ₀) above ƒ₀.ResultsThe vocal fold angle, defined by a tangent above and below the vocal folds, was 58° at ƒ₀, 47° at 2ƒ₀, and 59° at 4ƒ₀.ConclusionThe decreased caudomedial angle of the vocal fold from ƒ₀ to 2ƒ₀ (change in muscle belly from “;fat” to “thin”) and increased angle from 2ƒ₀ to 4ƒ₀ (from “thin” to “fat”) strongly supports the hypothesis that the vocal folds elongate and then tension when singing from ƒ₀ to 4ƒ₀. This is the first study to show this relationship in vivo.     

The Evolving Etiology of Bilateral Vocal Fold Immobility

In the past, bilateral vocal fold immobility (BVFI) occurred most commonly after thyroidectomy. However, no large series documenting the etiology of adult BVFI has been published within the past fifteen years. This study reviews the etiologic patterns of BVFI at our institutions. We compare BVFI from before and after 1980. We also review combined studies of unilateral vocal fold immobility (UVFI) to compare and unilateral versus bilateral etiologic trends. In comparison with previously published series, fewer cases of BVFI present today as a complication of thyroid surgery and more as the result of malignancies and nonsurgical trauma. Unfortunately, BVFI caused by malignancy is not usually an initial sign of local disease, but an ominous sign of recurrence or metastases. In comparing UVFI and BVFI we found that thyroidectomy causes a higher percentage of BVFI than of UVFI. Over one-third of UVFI cases were caused by neoplasm which further underscores the potential seriousness of immobile vocal folds and the need for careful investigation.     

Visualization and Quantification of the Medial Surface Dynamics of an Excised Human Vocal Fold During Phonation

SUMMARY: The purpose of this investigation was to investigate physical mechanisms of vocal fold vibration during normal phonation through quantification of the medial surface dynamics of the fold. An excised hemilarynx setup was used. The dynamics of 30 microsutures mounted on the medial surface of a human vocal fold were analyzed across 18 phonatory conditions. The vibrations were recorded with a digital high-speed camera at a frequency of 4,000 Hz. The positions of the sutures were extracted and converted to three-dimensional coordinates using a linear approximation technique. The data were reduced to principal eigenfuctions, which captured over 90% of the variance of the data, and suggested mechanisms of sustained vocal fold oscillation. The vibrations were imaged as the following phonatory conditions were manipulated: glottal airflow, an adductory force applied to the muscular process, and an elongation force applied to the thyroid cartilage. Over the range of variables studied, only the variation in glottal airflow yielded significant changes in subglottal pressure and fundamental frequency. All recordings showed high correlation for the distribution of the dynamics across the medial surface of the vocal fold. The distribution of the different displacement directions and velocities showed the highest variations around the superior region of the medial surface. Although the computed vibration patterns of the two largest empirical eigenfunctions were consistent with previous experimental observations, the relative prominence of the two eigenfunctions changed as a function of glottal airflow, impacting theories of vocal efficiency and vocal economy.     

Investigation of Anti-Hyaluronidase Treatment on Vocal Fold Wound Healing

SUMMARY: Phytochemical constituents of medicinal plants demonstrate inhibition of tissue and bacterial hyaluronidase. Echinacoside is a caffeoyl conjugate of Echinacea with known anti-hyaluronidase properties. The purpose of this study was to investigate the wound healing effects of Echinacea on vocal fold wound healing and functional voice outcomes. Pig animal model. Methods: Vocal fold injury was induced in 18 pigs by unilateral vocal fold stripping. The uninjured vocal fold served as control. Three groups of six pigs randomly received a topical application of 300, 600, or 1,200 mg of standardized Echinacea on the injured side. Animals were euthanized after 3, 10, and 15 days of wound healing. Phonation threshold pressure and vocal economy measurements were obtained from excised larynges. Treatment outcomes were examined by comparing the animals receiving treatment with a set of 19 untreated and 5 historical controls. Treatment effects on wound healing were evaluated by histologic staining for hyaluronan and collagen. Treated larynges revealed improved vocal economy and phonation threshold pressure compared with untreated larynges. Histologically, treated vocal folds revealed stable hyaluronan content and no significant accumulation of collagen compared with control. Findings provide a favorable outcome of anti-hyaluronidase treatment on acute vocal fold wound healing and functional measures of voice.     

Outcomes of Intubation-induced Vocal Fold Motion Impairment

ObjectiveVocal fold motion impairment (VFMI) is a potential consequence of intubation. Studies describing the natural course of this complication are largely case reports. This study aims to evaluate outcomes for a cohort of patients who endured varying degrees of vocal fold immobility or hypomobility post-intubation.Study DesignRetrospective chart review.MethodsUpon excluding known causes of VFMI, such as surgeries and tumors involving the head and neck, VFMI cases (ICD-9 diagnosis code 478.3) were identified from 2008 to 2014 at a regional healthcare institution. A total of 2,387 were identified and of those, 25 were intubation-induced VFMI cases. This cohort was then examined for notable features.ResultsWith a mean prolonged intubation duration of 6.55 days, 68% of cases resulted in left unilateral, 8% right unilateral, and 24% bilateral VFMI. Overall, 80% of patients experienced a recovery outcome (voice improvement or restoration of vocal fold mobility). Median recovery time was 4.31 months (mean, 6.51 months; range, 19-715 days). In cases of unilateral VFMI, 95% of cases had a recovery outcome. In cases of bilateral VFMI, 33% of cases had a recovery outcome. Additionally, bilateral cases showed a statistically significant association with an approximately 36-fold lower odds of recovery than unilateral cases (odds ratio, 0.0278; 95% confidence interval, 0.0020-0.3868; P value, 0.0077).ConclusionsIntubation-induced VFMI is rare. In this cohort, most cases resulted from prolonged intubation. While spontaneous recovery was the most common outcome, full remission was not guaranteed in every case. A sizable proportion of cases revealed bilateral motion impairment which was less likely to resolve. Our results are informative for tracheostomy decision-making and differential diagnoses for post-intubation laryngeal symptomatology.     

Laser Doppler Measurements of the Vocal Fold Blood Micro-Circulation

The authors have developed a laser Doppler method, referred to as LDF+LS (laser Doppler flowmetry by laryngostereometry), for measuring the vocal fold micro-circulation. The vocal folds of 103 patients were examined during general anesthesia. A laser Doppler probe was placed on defined positions at the vocal fold edge: midmembranous position (MP), 2 mm and 4 mm behind, and 1 mm anterior to MP. Three parameters were derived, ie, the concentration (CMBC) and velocity (V) of moving blood cells, and the product of both resulting in perfusion: P = CMBCxV. The results of 53 subjects with normal vocal fold status showed that the V at MP was significantly lower than 2 mm behind MP (P < 0.05). Men had significantly higher velocity than women (P < 0.05). Subjects older than 65 years had higher perfusion and CMBC as compared with younger subjects (P < 0.01). Smokers with normal vocal folds had higher velocity than non-smokers (P < 0.05). Measurements of healthy vocal folds were compared with benign vocal fold pathology. Vocal fold polyps had significantly higher perfusion than normal vocal folds (P < 0.01). In conclusion, the laser Doppler measurement is a sensitive tool estimating superficial blood flow in both normal and pathological vocal folds. The blood flow in normals differs with respect to gender and age probably due to variations in micro-circulation of the mucosa and lamina propria. Vocal fold pathology and external factors such as smoking result in blood flow changes.     

Histologic and Rheologic Characterization of Vocal Fold Scarring

Scarring of the vocal fold causes considerable dysphonia and presents significant treatment challenges. A rabbit model was developed to investigate the histologic ultrastructure and rheologic properties of the scarred vocal fold lamina propria. Eleven rabbit larynges were scarred by means of forcep biopsy. Sixty days postoperatively, the rabbits were sacrificed and their vocal folds were harvested. Histological analysis of the scarred and normal lamina propria was completed for collagen, procollagen, elastin, and hyaluronic acid. Linear viscoelastic shear properties of the tissues were also measured, including elastic shear modulus and dynamic viscosity. Compared to normal vocal fold lamina propria, scarred tissues demonstrated significantly less collagen, an increase in procollagen, and a decrease in elastin. Rheologically, both elastic shear modulus and dynamic viscosity were significantly higher for the scarred tissues. Increased stiffness and viscosity do not appear to result from an increase in collagen, but rather appear to be related to the presence of new, disorganized collagen scaffolding. Results are interpreted in terms of the possible role of interstitial proteins in the etiology of increased stiffness and viscosity, which requires further investigation. This animal model should allow for systematic future investigations of vocal fold scarring and its treatment.