Real-time ultrasonographic assessment of true vocal fold length in professional singers

A computational study of the influence of thyroarytenoid and cricothyroid muscle interaction on vocal fold dynamics in an MRI-based human laryngeal model

A human laryngeal model, incorporating all the cartilages and the intrinsic muscles, was reconstructed based on MRI data. The vocal fold was represented as a multilayer structure with detailed inner components. The activation levels of the thyroarytenoid (TA) and cricothyroid (CT) muscles were systematically varied from zero to full activation allowing for the analysis of their interaction and influence on vocal fold dynamics and glottal flow. The finite element method was employed to calculate the vocal fold dynamics, while the one-dimensional Bernoulli equation was utilized to calculate the glottal flow. The analysis was focused on the muscle influence on the fundamental frequency (fo). We found that while CT and TA  activation increased the fo in most of the conditions, TA activation resulted in a frequency drop when it was moderately activated. We show that this frequency drop was associated with the sudden increase of the vertical motion when the vibration transited from involving the whole tissue to mainly in the cover layer. The transition of the vibration pattern was caused by the increased body-cover stiffness ratio that resulted from TA activation.

An Old Myth: Prediction of the Correct Singing Voice Classification. True or not?

OBJECTIVE

Predicting the correct singing voice classification based on laryngoscopy is an old myth. The aim of this study was to evaluate if a professional phoniatrician/laryngologist can predict the correct singing voice classification only from laryngoscopy and to analyze different anatomical parameters between professional sopranos and altos to determine whether a multivariate analysis of anatomical parameters can predict the singing register.

STUDY DESIGN

Prospective study METHODS: We included 49 professional female singers (25 sopranos, 24 altos). Laryngoscopic images were shown to professional phoniatricians/laryngologists to rate whether it they show a soprano or an alto. In addition, a high-resolution computer tomography (HRCT) scan was performed during singing of ƒ0 by each singer. DICOM scan data were rendered and 3D-visualized using the software MIMICS. In all singers, we measured the length of the vocal folds of the glottis, the distance from the anterior commissure orthogonally to the vertebral spine, and the antero-posterior distance of the subglottis/trachea 1 cm and 2 cm below the glottis. We also measured the length and volume of the resonance space.

RESULTS

It was not possible to predict the singing voice classification only from laryngoscopy. In the HRCT images, sopranos had significantly shorter vocal folds, a shorter glottal length, a shorter distance from the anterior commissure to the spine, and a shorter resonance space. When combining all parameters, the chance of correctly predicting a soprano was 74.1% and an alto 68.2%.

CONCLUSION

Although there are anatomical differences between sopranos and altos, prediction of the singing voice classification from laryngoscopy or HRCT is not reliable enough for clinical use.

Pathophysiological Mechanisms Underlying Unilateral Vocal Fold Paralysis in Female Patients: An Ultrasonographic Study

OBJECTIVES

Laryngeal ultrasonography (LUS) has been suggested as an alternative diagnostic tool for unilateral vocal fold paralysis (UVFP). The present study applied LUS and quantitative laryngeal electromyography (LEMG) in female UVFP patients to investigate the pathophysiologic mechanisms of UVFP.

METHODS

In this cross-sectional study, vocal fold (VF) length parameters included resting and phonating VF length measured using B-mode LUS, and color Doppler vibrating length (CDVL) measured using the color Doppler mode.

RESULTS

Forty female patients with UVFP were enrolled, among whom 11 and 29 were assigned to the thyroarytenoid (TA) muscle+cricothyroid (CT) muscle group (with CT involvement) and the TA (without CT involvement) group, respectively. In the TA group, the turn frequency in thyroarytenoid-lateral cricoarytenoid (TA-LCA) on the paralyzed side, as observed through LEMG, correlated with the VF length during the resting phase (R=0.368, P=0.050) and CDVL values (R=0.627, P=0.000) on the paralyzed side. In the TA+CT group, the turn ratio in the CT muscle correlated with the normalized phonatory vocal length change (nPLC; R=0.621, P=0.041) on the paralyzed side.

CONCLUSION

CDVL and nPLC are two parameters that can be utilized to predict the turn frequencies of TA-LCA in UVFP cases without CT involvement, and the turn ratio of CT in cases of UVFP with CT involvement, respectively. The findings suggest that LUS, as a noninvasive tool, can serve as an alternative method for assessing the severity of laryngeal nerve injury and offer valuable insights into the pathophysiology of UVFP.

Normative data for certain vocal fold biomarkers among young normophonic adults using ultrasonography

PURPOSE

The current study aimed to profile vocal fold morphology, vocal fold symmetry, gender and task-specific data for vocal fold length (VFL) and vocal fold displacement velocity (VFDV) in young normophonic adults in the age range of 18-30 years using ultrasonography (USG).

METHODS

Participants underwent USG across quiet breathing, /a/ phonation and /i/ phonation tasks, and acoustic analysis was conducted to explore the relationship between USG and acoustic measures.

RESULTS

The study found that males have longer vocal folds than females, and overall greater velocities were observed in /a/ phonation, followed by /i/ phonation, with the lowest velocity observed in the quiet breathing task.

CONCLUSIONS

The obtained norms can be used as a quantitative benchmark for analyzing the vocal fold behavior in young adults.

Biomechanical Flow Amplification Arising From the Variable Deformation of the Subglottic Mucosa

OBJECTIVE

This study mapped the variation in tissue elasticity of the subglottic mucosa, applied these data to provide initial models of the likely deformation of the mucosa during the myoelastic cycle, and hypothesized as to the impact on the process of phonation.

STUDY DESIGN

Six donor human larynges were dissected along the sagittal plane to expose the vocal folds and subglottic mucosa. A linear skin rheometer was used to apply a controlled shear force, and the resultant displacement was measured. These data provided a measure of the stress/strain characteristics of the tissue at each anatomic point. A series of measurements were taken at 2-mm interval inferior of the vocal folds, and the change in elasticity was determined.

RESULTS

It was found that the elasticity of the mucosa in the subglottic region increased linearly with distance from the vocal folds in all 12 samples. A simple deformation model indicated that under low pressure conditions the subglottic mucosa will deform to form a cone, which could result in a higher velocity, thus amplifying the low pressure effect resulting from the Venturi principle, and could assist in maintaining laminar flow.

CONCLUSIONS

This study indicated that the deformation of the subglottic mucosa could play a significant role in the delivery of a low pressure airflow over the vocal folds. A large scale study will now be undertaken to secure more data to evaluate this hypothesis, and using computational fluid dynamics based on actual three-dimensional structure obtained from computed tomography scans the aerodynamics of this region will be investigated.

Predicting Achievable Fundamental Frequency Ranges in Vocalization Across Species

Vocal folds are used as sound sources in various species, but it is unknown how vocal fold morphologies are optimized for different acoustic objectives. Here we identify two main variables affecting range of vocal fold vibration frequency, namely vocal fold elongation and tissue fiber stress. A simple vibrating string model is used to predict fundamental frequency ranges across species of different vocal fold sizes. While average fundamental frequency is predominantly determined by vocal fold length (larynx size), range of fundamental frequency is facilitated by (1) laryngeal muscles that control elongation and by (2) nonlinearity in tissue fiber tension. One adaptation that would increase fundamental frequency range is greater freedom in joint rotation or gliding of two cartilages (thyroid and cricoid), so that vocal fold length change is maximized. Alternatively, tissue layers can develop to bear a disproportionate fiber tension (i.e., a ligament with high density collagen fibers), increasing the fundamental frequency range and thereby vocal versatility. The range of fundamental frequency across species is thus not simply one-dimensional, but can be conceptualized as the dependent variable in a multi-dimensional morphospace. In humans, this could allow for variations that could be clinically important for voice therapy and vocal fold repair. Alternative solutions could also have importance in vocal training for singing and other highly-skilled vocalizations.

Clinical Usefulness of Ultrasonography-Guided Laryngeal Electromyography

OBJECTIVES/HYPOTHESIS

To investigate the proper approach and technical method of ultrasonography-guided laryngeal electromyography (US-guided LEMG).

STUDY DESIGN

This is a prospective study.

METHODS

Twenty patients who underwent US-guided LEMG were enrolled. US-guided LEMG was cooperatively performed by one otolaryngologist, one neurologist, and one radiologist. The location of the needle electrode was confirmed with US after electrode insertion into the laryngeal intrinsic muscle. The US transducer was applied on the neck by a transverse/midline and transverse/oblique approach to identify the cricothyroid (CT), thyroarytenoid (TA) muscles, and the location of the needle electrode.

RESULTS

CT muscles were easily identified on US in all 20 patients. TA muscles were identified in 17 patients (85%). The transverse/oblique approach was helpful to detect TA muscle in case of calcified thyroid cartilage or anatomic variation.

CONCLUSIONS

US-guided LEMG, which enables the exact insertion of the needle electrode, improves the reliability of examination and is helpful in early detection and to prevent complications.

Ultrasound applicability in Speech Language Pathology and Audiology

PURPOSE: To present recent studies that used the ultrasound in the fields of Speech Language Pathology and Audiology, which evidence possibilities of the applicability of this technique in different subareas. RESEARCH STRATEGY: A bibliographic research was carried out in the PubMed database, using the keywords "ultrasonic," "speech," "phonetics," "Speech, Language and Hearing Sciences," "voice," "deglutition," and "myofunctional therapy," comprising some areas of Speech Language Pathology and Audiology Sciences. The keywords "ultrasound," "ultrasonography," "swallow," "orofacial myofunctional therapy," and "orofacial myology" were also used in the search. SELECTION CRITERIA: Studies in humans from the past 5 years were selected. In the preselection, duplicated studies, articles not fully available, and those that did not present direct relation between ultrasound and Speech Language Pathology and Audiology Sciences were discarded. DATA ANALYSIS: The data were analyzed descriptively and classified subareas of Speech Language Pathology and Audiology Sciences. The following items were considered: purposes, participants, procedures, and results. RESULTS: We selected 12 articles for ultrasound versus speech/phonetics subarea, 5 for ultrasound versus voice, 1 for ultrasound versus muscles of mastication, and 10 for ultrasound versus swallow. Studies relating "ultrasound" and "Speech Language Pathology and Audiology Sciences" in the past 5 years were not found. CONCLUSION: Different studies on the use of ultrasound in Speech Language Pathology and Audiology Sciences were found. Each of them, according to its purpose, confirms new possibilities of the use of this instrument in the several subareas, aiming at a more accurate diagnosis and new evaluative and therapeutic possibilities.