Membranous Vocal Fold Research Articles

The membranous contact quotient: A new phonatory measure of glottal competence

The membranous contact quotient (MCQ) is introduced as a measure of dynamic glottal competence. It is defined as the ratio of the membranous contact glottis (the anterior-posterior length of contact between the two membranous vocal folds) and the membranous vocal fold length. An elliptical approximation to the vocal fold contour during phonation was used to predict MCQ values as a function of vocal process gap (adduction), maximum glottal width, and membranous glottal length. MCQ is highly dependent on the vocal process gap and the maximum glottal width, but not on vocal fold length. Five excised larynges were used to obtain MCQ data for a wide range of vocal process gaps and maximum glottal widths. Predicted and measured MCQ values had a correlation of 0.93, with an average absolute difference of 9.6% (SD = 10.5%). The model is better at higher values of MCQ. The theory for MCQ is also expressed as a function of vocal process gap and subglottal pressure to suggest production control potential. The MCQ measure is obtainable with the use of stroboscopy and appears to be a potentially useful clinical measure.

Function of the interarytenoid(IA) muscle in phonation: in vivo laryngeal model.

Thyroarytenoid(TA), lateral cricoarytenoid(LCA), and IA muscles are referred to as the adductors of the vocal fold. The TA is known to shorten the vocal folds and to adduct the membranous vocal fold, and the LCA adducts the inter-vocal process region and IA adducts the posterior commissure. Even though IA has an important role for the positioning of the vocal folds during respiration and phonation together with the action of the posterior cricoarytenoid muscle, little is known about the effect of IA on voice parameters during phonation. An in vivo canine model was used in five mongrel dogs to examine the role of the IA muscle in controlling phonation. In two out of five dogs, sound could not be elicited without stimulating the IA branches of the recurrent laryngeal nerves. When the IA was dynamically and statistically stimulated, subglottic pressure, vocal intensity and fundamental frequency were increased. However, open quotient was not changed markedly. These results suggest that the IA affects the voice parameters mainly by controlling subglottic pressure during phonation.

Measurement of vocal fold intraglottal pressure and impact stress

Intraglottal pressure was measured according to a previously described hemilarynx procedure. Three phases were identified for intraglottal pressure: an impact phase, in which the vocal folds come into contact and produce a sharp pressure pulse; a preopen phase, in which there is a progressive pressure buildup due to increased exposure of the vocal fold surfaces to subglottal pressure; and an open phase, in which intraglottal pressure becomes aerodynamic and drops gradually from opening to closing. Impact pressure peaks were positively related to subglottal pressure, elongation, and adduction of the vocal folds. The midpoint of the membranous vocal fold received the maximum impact stress. The experimental results match well with analytical predictions and support a current theory of mechanical trauma leading to vocal nodules.

Arytenoid adduction and type I thyroplasty in the treatment of aphonia

Arytenoid adduction is a procedure used to medialize the paralyzed vocal fold, closing the posterior glottis. Isshiki type I thyroplasty allows medialization of the anterior membranous vocal fold. Using the arytenoid adduction, in combination with Isshiki type I thyroplasty as needed, five patients were treated for aphonia. Surgical results were evaluated with voice recordings, electroglottography, and photoglottography. Jitter ratio, shimmer ratio, and signal-to-noise ratio were measured. Laryngeal stroboscopy and glottography were used to assess the mucosal wave and vibratory nature of the vocal folds. After operation, vocal function was restored. Analysis of data from these five aphonia patients revealed improved glottic phonatory function. The arytenoid adduction in combination with the Isshiki type I thyroplasty is an effective technique for aphonia caused by a significant posterior glottic gap with unilateral vocal-cord paralysis.

The vertebrate larynx: Adaptations and aberrations

The complex anatomy of the vertebrate larynx shows a steady progression from the simple slit on the floor of the lungfish's pharynx to the fine-tuned mechanism of the human vocal apparatus. The frog's larynx acts as a check valve to prevent collapse of the lungs during a dive, since the animal has no rib cage. The crocodile's laryngeal framework has acquired an epiglottic analogue which fits snugly into the nasopharynx and protects the lower respiratory tract from inundation while the animal drowns its prey. The snake's larynx lies intraorally and can be extended beyond the lower teeth while the reptile leisurely swallows its prey intact. The mammal has acquired a cricothyroid joint, allowing its membranous vocal folds to be stretched during phonation. In Homo sapiens, vocal performance has reached its highest degree of versatility, with a vocal fold capable of adjustment in length, tension and shape. In the course of organic evolution, man appears to have chosen the ability to speak and sing over the security that an intranarial epiglottis would have given him.

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.

A New Clinical Measure of External Laryngeal Size Which Predicts the Fundamental Frequency of the Larynx

A method for accurately predicting the average fundamental frequency of the larynx from an external measurement of laryngeal size has been developed. In 21 human cadaveric dissections we have demonstrated that the external height of the larynx (measured from the lower border of the cricoid cartilage to the upper border of the thyroid notch) was significantly correlated to the length of the membranous vocal fold (r = 0.94, p less than 0.001). This same external measure of laryngeal size in 115 healthy volunteers was found to be related to their voice fundamental frequency. Significant differences were found between males and females with respect to both laryngeal size (p less than 0.001) and voice fundamental frequency (p less than 0.001). A strong correlation between the external laryngeal measurement and speaking fundamental frequency was found with an overall correlation coefficient for both sexes of 0.8 (p less than 0.001). Using this external measurement, it may be possible to accurately predict the fundamental frequency in males and females. It is proposed that such a measurement could be used to identify various laryngeal diseases and also serve as a basis for corrective treatment in various voice disorders.

Changes in vocal fold length with nerve stimulation in canine larynges

Vocal fold length change and adductory movement of the glottis were obtained from seven canine larynges when the recurrent and the superior laryngeal nerve were stimulated bilaterally. A surgical procedure was used to make marks on the vocal fold for length measurements. Frame by frame analysis was used to get static and dynamic data on vocal fold length. The mean maximum elongation of the membranous vocal folds was 44.7% with 120‐ms elongation time and 140‐ms relaxation time. The mean maximum shortening of membranous vocal folds was 17.8%, with 110‐ms contraction time and 115‐ms relaxation time. When both agonist and antagonist muscles were in maximum contraction, the mean elongation was 24.3%. The length‐time curve approximates an exponential function. Closing of glottis occurred in less than 35 ms. The temporal results agree with earlier pitch change results. [Work supported by NIH Grant NS16320.]