Characterization of Primary Muscle Tension Dysphonia Using Acoustic and Aerodynamic Voice Metrics

Optical Flow Analysis of Paralaryngeal Muscle Movement

OBJECTIVES

The paralaryngeal muscles are thought to be hyperfunctional with phonation in patients with primary muscle tension dysphonia (pMTD). However, objective, quantitative tools to assess paralaryngeal movement patterns lack. The objectives of this study were to (1) validate the use of optical flow to characterize paralaryngeal movement patterns with phonation, (2) characterize phonatory optical flow velocities and variability of the paralaryngeal muscles before and after a vocal load challenge, and (3) compare phonatory optical flow measures to standard laryngoscopic, acoustic, and self-perceptual assessments.

METHODS

Phonatory movement velocities and variability of the paralaryngeal muscles at vocal onsets and offsets were quantified from ultrasound videos and optical flow methods across 42 subjects with and without a diagnosis of pMTD, before and after a vocal load challenge. Severity of laryngoscopic mediolateral supraglottic compression, acoustic perturbation, and ratings of vocal effort and discomfort were also obtained at both time points.

RESULTS

There were no significant differences in optical flow measures of the paralaryngeal muscles with phonation between patients with pMTD and controls. Patients with pMTD had significantly more supraglottic compression, higher acoustic perturbations, and higher vocal effort and vocal tract discomfort ratings. Vocal load had a significant effect on vocal effort and discomfort but not on supraglottic compression, acoustics, or optical flow measures of the paralaryngeal muscles.

CONCLUSION

Optical flow methods can be used to study paralaryngeal muscle movement velocity and variability patterns during vocal productions, although the role of the paralaryngeal in pMTD diagnostics (e.g., vocal hyperfunction) remains suspect.

LEVEL OF EVIDENCE

2 Laryngoscope, 134:1792-1801, 2024.

Relationships Between Vocal Fold Adduction Patterns, Vocal Acoustic Quality, and Vocal Effort in Individuals With and Without Hyperfunctional Voice Disorders

OBJECTIVES/HYPOTHESIS

Increased vocal effort and aberrant vocal quality are often attributed to vocal fold hyperadduction in hyperfunctional voice disorders. However, there are currently no established methods to quantify vocal fold adduction beyond subjective descriptors in this clinical population. Furthermore, relationships between vocal fold adduction patterns, vocal effort severity, and vocal quality are not well characterized. Therefore, the objectives of this study were to (1) quantify vocal fold adduction, applying a previously validated method developed for patients with vocal fold paralysis, and (2) correlate these measures with acoustic vocal quality and self-perceived measures of vocal effort severity.

METHODS

A deep learning program, Automated Glottic Action Tracking using artificial Intelligence, was used to track glottic angle configurations and vocal fold adduction velocities on laryngoscopic videos across 60 laryngoscopies (20 primary muscle tension dysphonia [pMTD], 20 phonotraumatic lesions, and 20 healthy controls). Voice samples were also acquired, and cepstral peak prominence (CPP) and H1-H2 acoustic measures were used to quantify vocal quality. Participants were also asked to rate their vocal effort on a 100 mm visual analog scale.

RESULTS

There were no significant group differences in glottic angle configurations or vocal fold adduction velocities, although there were trends toward increased peak vocal fold adduction velocities in patients with hyperfunctional voice disorders compared to controls. Vocal effort was significantly higher in the two hyperfunctional groups compared to controls. CPP was significantly lower in the pMTD group, but there were no group differences in acoustic parameters between any of the other groups or for H1-H2 values.

CONCLUSION

Despite significantly more vocal effort reported in patients with hyperfunctional voice disorders, there were no significant group differences in vocal fold adduction patterns. These findings suggest other physiologic mechanisms may also be responsible for the symptoms and genesis of pMTD and benign vocal fold lesions.

Use of Motion Capture Technology to Study Extrinsic Laryngeal Muscle Tension and Hyperfunction

OBJECTIVES

Patients with primary muscle tension dysphonia (pMTD) commonly report paralaryngeal pain and discomfort, and extrinsic laryngeal muscle (ELM) tension and hyperfunction are commonly implicated. However, quantitative physiological metrics to study ELM movement patterns for the characterization of pMTD diagnosis and monitoring of treatment progress are lacking. The objectives of this study were to validate motion capture (MoCap) technology to study ELM kinematics, determine whether MoCap could distinguish ELM tension and hyperfunction between individuals with and without pMTD, and investigate relationships between common clinical voice metrics and ELM kinematics.

METHODS

Thirty subjects (15 with pMTD and 15 controls) were recruited for the study. Sixteen markers were placed on different anatomical landmarks on the chin and anterior neck. Movements across these regions were tracked during four voice and speech tasks using two three-dimensional cameras. Movement displacement and variability were determined based on 16 key-points and 53 edges.

RESULTS

Intraclass correlation coefficients demonstrated high intra- and inter-rater reliability (p's < 0.001). Other than greater movement displacements around the thyrohyoid space during longer phrasing (reading passage, 30-s diadochokinetics) and more movement variability in patients with pMTD, kinematic patterns between groups were similar across the 53 edges for the four voice and speech tasks. There were also no significant correlations between ELM kinematics and standard voice metrics.

CONCLUSION

Results demonstrate the feasibility and reliability of MoCap for the study of ELM kinematics.

LEVEL OF EVIDENCE

3 Laryngoscope, 133:3472-3481, 2023.

Extrinsic Laryngeal Muscle Tension in Primary Muscle Tension Dysphonia with Shear Wave Elastography

OBJECTIVES

It has been assumed that patients with primary muscle tension dysphonia (pMTD) have more extrinsic laryngeal muscle (ELM) tension, but tools to study this phenomenon lack. Shear wave elastography (SWE) is a potential method to address these shortcomings. The objectives of this study were to apply SWE to the ELMs, compare SWE measures to standard clinical metrics, and determine group differences in pMTD and typical voice users before and after vocal load.

METHODS

SWE measurements of the ELMs from ultrasound examinations of the anterior neck, supraglottic compression severities from laryngoscopic images, cepstral peak prominences (CPP) from voice recordings, and self-perceptual ratings of vocal effort and discomfort were obtained in voice users with (N = 30) and without (N = 35) pMTD, before and after a vocal load challenge.

RESULTS

ELM tension significantly increased from rest-to-voiced conditions in both groups. However, the groups were similar in their ELM stiffness levels at SWE at baseline, during vocalization, and post-vocal load. Levels of vocal effort and discomfort and supraglottic compression were significantly higher and CPP was significantly lower in the pMTD group. Vocal load had a significant effect on vocal effort and discomfort but not on laryngeal or acoustic patterns.

CONCLUSION

SWE can be used to quantify ELM tension with voicing. Although the pMTD group reported significantly higher levels of vocal effort and vocal tract discomfort and, on average, exhibited significantly more severe supraglottic compression and lower CPP values, there were no group differences in levels of ELM tension using SWE.

LEVEL OF EVIDENCE

2 Laryngoscope, 133:3482-3491, 2023.

Examining Therapy Duration in Adults With Voice Disorders

PURPOSE

This study examined the number of voice therapy sessions and the number of weeks in treatment to achieve desired voice outcomes in adults with voice disorders. Factors that may predict therapy duration were examined, as was the percentage of patients returning to the clinic for additional voice therapy after initial discharge.

METHOD

An observational cohort design was utilized. Data from 558 patients were extracted from the University of Wisconsin-Madison Voice and Swallow Outcomes Database. Patients diagnosed with muscle tension dysphonia, vocal fold paralysis, benign vocal fold lesions, laryngospasm/irritable larynx, and presbyphonia were examined. Patient demographics, auditory-perceptual assessments, acoustics, aerodynamics, videostroboscopy ratings, self-reported scales, and medical comorbidities were collected.

RESULTS

Patients required an average of 5.32 (SD = 3.43) sessions of voice therapy before voice outcomes were sufficiently improved for discharge. Average number of sessions ranged from 4.3 for presbyphonia to 6.7 for benign vocal fold lesions. Baseline overall Grade Roughness Breathiness Asthenia and Strain rating (p < .001), Dysphonia Severity Index (p < .001), Voice Handicap Index score (p < .01), age (p = .006), and occupational voice user status (p < .001) significantly predicted the number of therapy sessions required. Overall, 14.5% of patients returned for additional voice therapy following an initial discharge from treatment.

CONCLUSIONS

Findings inform our understanding of how many sessions patients with voice disorders require to achieve desired voice outcomes. Additional research is needed to optimize the efficacy of voice treatment and determine how recurrence of dysphonia might best be prevented.

Interoception, Voice Symptom Reporting, and Voice Disorders

OBJECTIVES

Interoception may play a role in how individuals perceive their voice disorder. The first objective of this study was to investigate relationships between interoception and voice disorder class (functional, structural, neurological). The second objective was to determine relationships between interoception and voice-related outcome measures between patients with functional voice and upper airway disorders and typical voice users. The third objective was to determine whether patients with primary muscle tension dysphonia (a type of functional voice disorder) had different levels of interoceptive awareness than typical voice users.

STUDY DESIGN

Prospective cohort study.

METHODS

One hundred subjects with voice disorders completed the multidimensional assessment of interoceptive awareness-2 (MAIA-2). Voice diagnosis and singing experience were also acquired from each patient's medical chart. Voice handicap (VHI-10) and Part 1 of the vocal fatigue index (VFI-Part1) scores were obtained from patients diagnosed with functional voice and upper airway disorders. MAIA-2, VHI-10, VFI-Part1, and singing experience were also obtained from 25 typical voice users. Multivariable linear regression models were used to assess the association between response variables and voice disorder class, adjusting for singing experience, gender, and age.

RESULTS

There were no significant group differences between voice disorder class (functional, structural, neurological) after adjusting for multiple comparisons. Participants with functional voice and upper airway disorders who scored significantly higher on the VHI-10 and VFI-Part1 had lower Attention Regulation sub-scores on the MAIA-2 (P's<0.05). Patients with primary muscle tension dysphonia scored significantly lower on the Emotional Awareness MAIA-2 subscale than typical voice users (P=0.005).

CONCLUSION

Patients with functional voice disorders with lower capabilities to attend to body sensations may score higher on voice-related patient-reported outcome measures, like the VHI-10 and VFI-Part1. Patients with primary muscle tension dysphonia may also have lower capabilities in processing their body sensations than typical voice users.

Clinical Characteristics and Effects of Vocal Demands in Occupational Voice Users With and Without Primary Muscle Tension Dysphonia

OBJECTIVES

The objectives of this study were to (1) compare laryngeal configuration patterns in occupational voice users with and without primary muscle tension dysphonia (pMTD), (2) characterize laryngeal configurations in relation to other clinical metrics (acoustic, perceptual), and (3) determine the effects of vocal demands (load) on these clinical parameters.

METHODS

Thirty subjects (15 pMTD, 15 control) were recruited for the study. Laryngoscopic examinations and voice samples for sustained /i/ were obtained before and after a half hour vocal load task. Subjects rated their vocal effort and discomfort before and after the vocal load. Laryngeal configurations were analyzed subjectively with dichotomous and categorical rating scales and hyper function severity quantified (endolaryngeal area outlets). Overall dysphonia severity and vocal instability of each voice sample was rated on 100mm visual analog scales and cepstral peak prominence (CPP) extracted from each voice sample.

RESULTS

Laryngeal configurations between groups or vocal load condition were not distinguishable with any of the dichotomous, categorical, or quantitative laryngeal metrics. Vocal effort and discomfort ratings were significantly higher in the pMTD group compared to the control group. Vocal load also had significant effects across groups on vocal effort and vocal tract discomfort ratings. Although CPP values fell within the normal range in both groups, CPP was significantly lower in the pMTD group at both pre-load and post-load time points. Auditory-perceptual ratings were also significantly worse in the pMTD group. Vocal load did not have a significant effect on acoustic or auditory-perceptual measures.

CONCLUSION

Similar laryngeal configurations between groups at both pre- and post-vocal load suggests classic patterns of laryngeal "hyperadduction" may occur variably in occupational voice users and may not be indicative of pMTD pathophysiology. Greater vocal effort, discomfort, instability, and perturbation within the vocal system may better define pMTD than laryngeal configuration in occupational voice users with pMTD.

Laying the Groundwork to Study the Heterogeneous Nature of Vocal Fatigue

Vocal fatigue has remained an elusive construct-despite its significant impact on communication, vocation, and quality of life. Current frameworks define vocal fatigue in the context of vocal demands and vocal demand-responses. However, the impact of factors like individuals' baseline vocal fitness and perception of the demand are not well understood. What is also not well understood are the effects of specific vocal demand ingredients on an individual's vocal demand responses. Furthermore, current outcome measures utilized to capture vocal fatigue lack sensitivity and underlying mechanisms are poorly understood. These gaps have led to inconclusive next steps in how to best define, assess, monitor, and manage vocal fatigue. A conceptual framework is needed to study and better understand vocal fatigue constructs. Such a framework should consider the individual's baseline physiology, psychology, key vocal demand ingredients, and biophysiological mechanisms underlying demand responses. The objective of this paper is to help the reader better understand the complex and heterogeneous nature of vocal fatigue and its impact on reliable assessment and monitoring. Future studies will require better elucidation of vocal demand ingredients, will need more sensitive vocal demand response measures, and will need to take in to account an individual's baseline physiology and psychological factors.

Integrative Review and Framework of Suggested Mechanisms in Primary Muscle Tension Dysphonia

PURPOSE

Despite the high prevalence of primary muscle tension dysphonia (MTD-1), its underlying mechanisms and their interrelationships have yet to be fully identified. The objectives of this integrative review were (a) to describe and classify the suggested underlying mechanisms for MTD-1, (b) to appraise the empirical evidence supporting each of the proposed mechanisms, and (c) to summarize the information in an integrative model.

METHOD

PubMed, Scopus, and CINAHL were searched for all publications pertaining to muscle tension dysphonia. Papers were retained if they included theoretical or empirical data pertaining to underlying mechanisms of MTD-1. A total of 921 papers initially qualified for screening, of which 100 remained for consideration in this review. Underlying mechanisms of MTD-1 were extracted using a consensus approach.

RESULTS

Seven broad categories of putative mechanisms involved in MTD-1 were identified: psychosocial, autonomic, sensorimotor, respiratory, postural, inflammatory, and neuromuscular. These categories were further divided into 19 subcategories detailed in the body of this review article. Based on the reviewed evidence, our proposed integrative model presents MTD-1 as an idiosyncratic motor adaptation to physiological perturbation or perceived threat. Under this model, physiologically or psychologically aversive stimuli can instigate a series of motor adaptations at multiple levels of the nervous system, ultimately disturbing muscle activation patterns and their biomechanical outcomes. Importantly, these adaptations appear to have the potential to become chronic even after threatening stimuli are withdrawn.

CONCLUSIONS

The proposed model highlights the importance of personalized rehabilitation in MTD-1 treatment. Limitations of the literature are discussed to provide guidance for future research aimed at improving our understanding of MTD-1.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.19586065.