Towards the Expression of Sex Hormone Receptors in the Human Vocal Fold

BACKGROUND: The human larynx is assumed to be a steroid receptor target organ. There are only very limited data on the evidence of steroid receptors in the vocal folds, although voice alterations due to hormonal influence and treatment have been found. GOAL OF THE STUDY: To investigate the expression of estrogen alpha, progesterone, and androgen receptors in human vocal folds (vocalis muscle, glands, lamina propria, epithelium). METHODS: Immunohistochemically, vocal fold cadaver specimens of 15 autopsied patients (6 women, 9 men), which were taken approximately 4 to 8 hours postmortem were investigated. Furthermore, one (male) vocal fold biopsy obtained intraoperatively during a laryngectomy was tested. RESULTS: No specific immunohistochemical staining for the different types of steroid hormones investigated could be observed in either the postmortem taken biopsies nor the intraoperatively one. However, several unspecific staining patterns could be observed. CONCLUSION: The results of this study contradict recently published data and question the expression of sex hormone receptors in the vocal folds. Main causes of false interpretations of unspecific staining are discussed.     

Current Understanding and Review of the Literature: Vocal Fold Scarring

Vocal fold scarring is the greatest cause of poor voice after vocal fold injury. Scarring causes a disruption of the viscoelastic layered structure of the lamina propria, an increase in stiffness of the vibratory structure, and glottic incompetence. Current treatments for this complex condition are inconsistent and often produce suboptimal results. Research investigating this condition has dramatically increased over the last several years. The literature has been directed toward understanding vocal fold scarring at the biological level and translating this to the clinical forum. We present an up-to-date, thorough, and scholarly review of the literature in vocal fold scarring since 1996.     

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.     

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.     

Multiparametric Analysis of Vocal Fold Vibrations in Healthy and Disordered Voices in High-Speed Imaging

Objectives

The aim of this study was to look for visual subjective and objective parameters of vocal fold dynamics being capable of differentiating healthy from pathologic voices in daily clinical practice applying endoscopic high-speed digital imaging (HSI).

Study Design and Methods

Four hundred ninety-six datasets containing 80 healthy and 416 pathologic subjects (232 functional dysphonia (FD), 13 bilateral, and 171 unilateral vocal fold nerve paralysis) were analyzed retrospectively. Videos at 4000 Hz (256 × 256 pixel) were recorded during sustained phonation. Subjective parameters were visually evaluated and complemented by an analysis of objective parameters. Visual subjective parameters were mucosal wave, glottal closure type, glottal closure insufficiency (GI), asymmetries of the vocal folds, and phonovibrogram (PVG) symmetry. After image segmentation, objective parameters were computed: closed quotient, perturbation measures (PMs) of glottal area, and left-right asymmetry values.

Results

HSI evaluation enabled to distinguish healthy from pathologic voices. For visual subjective parameters, GI, symmetrical behavior, and PVG symmetry exhibited statistical significant differences. For 95% of the data, objective parameters could be computed. Among objective parameters, closed quotient, jitter, shimmer, harmonic-to-noise ratio, and signal-to-noise ratio for the glottal area function differentiated statistically significant normal from pathologic voices. Applying linear discriminant analysis by combining visual subjective and objective parameters, accurate classifications were made for 63.2% of the female and 87.5% of the male group for the three-class problem (healthy, FD, and unilateral vocal fold nerve paralysis).

Conclusion

Actual acoustically applied PMs can be transferred to clinical beneficial HSI analysis. Combining visual subjective and objective basic parameters succeeds in differentiating pathologic from healthy voices. The presented evaluation can easily be included into everyday clinical practice. However, further research is needed to broaden our understanding of the variability within and across healthy and pathologic vocal fold vibrations for diagnosing voice disorders and therapy control.     

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.     

Vocal fold vibration of the canine larynx: Observation from an infraglottic view

The authors studied the vibratory action of the canine vocal fold from the tracheal side utilizing high-speed cinematography. Five excised canine larynges were used, and the lower surface of the vocal fold of three of them were marked with India ink as a tracer of a specific point on the vocal fold. A mucosal prominence, called the mucosal upheaval, appeared between the anterior commissure and the vocal process. Vibration was not seen below the mucosal upheaval. The mucosal wave started to move medially from just above the mucosal upheaval. The mucosal wave then became the free edge (lower lip) and collided with that of the other side at the midline. After collision, the lower lip moved upward to become the upper lip. At the same time, a part of the lower lip reflected laterally. The mucosal wave of the next cycle started from just above the mucosal upheaval during an opening phase. The mucosal upheaval vibrated with a low amplitude and with an earlier phase than the other portion of the vocal fold. The increase in tension of the vocal fold did not change the basic vibratory pattern of the mucosal upheaval, the mucosal wave, or the free edge. However, analysis of the mark before and after the increase in tension revealed that the mucosal upheaval occurred more medially or above when the vocal fold tension increased.     

Cooperative Regulation of Vocal Fold Morphology and Stress by the Cricothyroid and Thyroarytenoid Muscles

Voice is produced by vibrations of vocal folds that consist of multiple layers. The portion of the vocal fold tissue that vibrates varies depending primarily on laryngeal muscle activity. The effective depth of tissue vibration should significantly influence the vibrational behavior of the tissue and resulting voice quality. However, thus far, the effect of the activation of individual muscles on the effective depth is not well understood. In this study, a three-dimensional finite element analysis is performed to investigate the effect of the activation of two major laryngeal muscles, the cricothyroid (CT) and thyroarytenoid (TA) muscles, on vocal fold morphology and stress distribution in the tissue. Because structures that bear less stress can easily be deformed and involved in vibration, information on the morphology and stress distribution may provide a useful estimate of the effective depth. The results of the analyses indicate that the two muscles perform distinct roles, which allow cooperative control of the morphology and stress. When the CT muscle is activated, the tip region of the vocal folds becomes thinner and curves upward, resulting in the elevation of the stress magnitude all over the tissue to a certain degree that depends on the stiffness of each layer. On the other hand, the TA muscle acts to suppress the morphological change and controls the stress magnitude in a position-dependent manner. Thus, the present analyses demonstrate quantitative relationships between the two muscles in their cooperative regulation of vocal fold morphology and stress.