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

Phonation differentiation by non-contact laryngeal magnetomyography

Phonation is important for our daily communication and requires the activation of internal and external laryngeal muscles, which can be recorded by electromyography (EMG) using surface or needle electrodes. Here we present a new noncontact method, laryngeal magnetomyography. As a proof-of-concept, we investigated the feasibility of differentiating various vocalization conditions using laryngeal MMG in two healthy subjects using optically pumped magnetometers (OPM). We recorded magnetic muscle activity of the larynx and neighboring cervical muscles using a 3 × 5 array of OPMs. Subjects vocalized an /a/ in three different conditions: loud high pitch, loud low pitch, and soft high pitch, in 90 s blocks. After removing cardiac artifacts, MMG signals were in the range of 1.5 pT with significant amplitude differences between conditions. In both subjects, Linear Discriminant Analysis (LDA) was able to significantly classify vocalization conditions based on the spatial pattern of MMG activities. In sum, we show that laryngeal MMG allows contactless differentiation of phonations based on myomagnetic signals. Our results set the stage for future studies to explore this method for clinical diagnostics and therapy. Functional, contactless muscle recordings during vocalization enable new applications for miniaturized quantum sensors, e.g. in linguistic studies and speech rehabilitation.

An Integrative Supraglottic Sound Source Taxonomy (SSST) for Pathological Speaking Voice: A Case Series

OBJECTIVES

Supraglottic structures can participate in sound source creation when there is either pathological or healthy glottal-level voice production. For pathological voices, supraglottal structures may form part of the overall sound production, be associated with a presenting symptom, or may constitute a substitutional vibratory source. A recent taxonomy in healthy singing populations proposes four dimensions, including distinct phenotyping, vibrational strategies, level of control, and number of vibrating sources to distinguish among a number of supraglottic sound sources in healthy voices, yet differences and similarities between healthy and unhealthy involvement of supraglottic sound sources remain unclear. The purpose of this study was to extend the previously outlined supraglottic sound source taxonomy based in healthy singing populations to pathological voice and develop an integrative supraglottic sound source taxonomy (SSST).

METHOD

A case series of seven patients identified as involving vibrations of supraglottic structures during routine clinical assessment were included and discussed according to the supraglottic sound source taxonomy dimensions. Patients were assessed using stroboscopy, electroglottography, and acoustic measures during sustained vowel tasks and continuous speech tasks at comfortable pitches.

RESULTS

Beyond supplementary and substitutional strategies for involving supraglottic sound sources, pathological voices may also recruit supraglottic structures in a compensatory manner allowing for improved vocal fold entrainment. The results suggest that compensatory strategies came in two forms, one for which the pathology necessitating supraglottic sound source involvement is irreversible (e.g., following extensive cordectomy) and one where the pathology is reversible (e.g., following medialization laryngoplasty procedure for unilateral paralysis). Accordingly, supraglottic vibrations can be separated into an integrative taxonomy that outlines supplementary, compensatory, or substitutional functions of vibration with further dimensions related to intentional or unintentional level of control, unisource or multisource number of supraglottic sound sources, and distinction of the involved supraglottic phenotypes. Previously identified distinct phenotypes were determined in the studied population according to the anatomical vibration source, including ventricular fold vibrations, arytenoid against arytenoid vibrations, cuneiform/arytenoid against epiglottis vibrations, and vibrations in the aryepiglottic free edge along with large vocal fold amplitude of vibrations. The study proposes hypotheses as to differences between healthy and pathological use of supraglottic vibrations along dimensions of laryngeal, respiratory, and resonatory technical ability and control.

CONCLUSIONS

The study presents an integrative SSST including phenotyping for both pathological and healthy voice. Diagnostic, surgical, rehabilitative, and pedagogical relevance is discussed.

Preliminary Effects of Respiratory Lung Volume Training (RLVT) on Hyolaryngeal Kinematics in People With Primary Muscle Tension Dysphonia

OBJECTIVES

The purpose of this preliminary study was to determine the effects of a novel respiratory-based intervention on hyolaryngeal kinematics in people with primary muscle tension dysphonia (pMTD) using ultrasonography and acoustic measures.

METHOD

Pretraining to post-training changes in hyolaryngeal kinematics were studied for 11 participants with pMTD using ultrasonography to objectively measure and compare the relative positions of the hyoid bone and thyroid cartilage before and after treatment. Displacement of the hyoid bone and thyroid cartilage was measured during sustained phonation of the vowel /ɑ/, before and after completion of Respiratory Lung Volume Training (RLVT), which trains the use of higher speech lung volume initiation and termination levels while implementing real-time visual biofeedback. Hyolaryngeal position was determined from still frames extracted from ultrasound video recordings, with measures normalized to reflect change from rest during voicing for each participant. The associations between hyolaryngeal kinematics and acoustic measures of voice were also investigated.

RESULTS

Thyroid-to-hyoid displacement during voicing was significantly lower after completion of RLVT. There were no differences in hyoid-to-mandible displacement during voicing when comparing pretraining to post-training timepoints. Moderate-to-strong associations between thyroid-to-hyoid displacement and acoustic voice measures were identified for one or more speaking contexts.

CONCLUSIONS

Laryngeal elevation during voicing appears to be reduced after completion of RLVT in people with pMTD. Mechanical and functional interactions of the respiratory and laryngeal subsystems likely contributed to this kinematic change and the associations between laryngeal kinematics and acoustic voice features. Ultrasonography-based anatomic displacement measurements may provide an objective and sensitive method for determining treatment-related change in hyolaryngeal kinematics.

Relationships Between Aerodynamics and Voice Symptoms in Primary Muscle Tension Dysphonia

OBJECTIVES

Measures of self-perceived voice symptoms and aerodynamic assessments are commonly used in voice clinics, particularly for patients with primary muscle tension dysphonia (pMTD). However, relationships between these perceptual metrics and physiological parameters are not well-understood, making it difficult to determine how one informs the other in clinical decision-making. The goal of this study was to characterize relationships between self-perceived voice symptoms and physiological aerodynamic parameters in individuals with and without pMTD.

METHODS

Aerodynamic voicing efficiency metrics (mean peak subglottal pressure, mean transglottal airflow, peak expiratory airflow, expiratory airflow duration, and total expiratory volume) and self-perceived voice symptoms (vocal effort, vocal fatigue, vocal tract discomfort, and vocal impact) were collected in 45 participants with (n = 20) and without (n = 25) pMTD. Group differences in aerodynamic parameters and voice symptom metrics were determined with t tests. Relationships between these measures were determined by Pearson's correlations and Principal Component Analysis.

RESULTS

Although patients with pMTD had significantly higher vocal effort, vocal fatigue, and vocal tract discomfort scores compared with vocally healthy controls (P's < 0.0001), there were no significant group differences in any of the aerodynamic parameters after Bonferroni correction (P's > 0.005) and no significant correlations between voice symptoms and aerodynamics (P's > 0.05). The voice symptom metrics clustered closely together and accounted for the majority of the variance in the pMTD cohort, while subglottal pressure and transglottal airflow aerodynamic parameters contributed to a lesser extent.

CONCLUSION

The weak relationships between voice symptoms and aerodynamics in patients with pMTD suggest that somatosensory perceptions of voice symptoms do not always correspond to underlying aberrant laryngeal-respiratory motor patterns. Additionally, non-significant trends toward increased and more variable subglottal pressures and transglottal airflows in the pMTD group could indicate the presence of pMTD phenotypes.

Salient Voice Symptoms in Primary Muscle Tension Dysphonia

INTRODUCTION

Patients with primary muscle tension dysphonia (pMTD) commonly report symptoms of vocal effort, fatigue, discomfort, odynophonia, and aberrant vocal quality (eg, vocal strain, hoarseness). However, voice symptoms most salient to pMTD have not been identified. Furthermore, how standard vocal fatigue and vocal tract discomfort indices that capture persistent symptoms-like the Vocal Fatigue Index (VFI) and Vocal Tract Discomfort Scale (VTDS)-relate to acute symptoms experienced at the time of the voice evaluation is unclear. Finally, correlations between voice symptoms and acoustic vocal quality are poorly understood. As such, the objectives of this study were to: (1) identify the most salient pMTD symptoms, (2) correlate the VFI and VTDS with acute voice symptom severity, and (3) better understand relationships between voice symptom experiences and vocal acoustics.

METHODS

Thirty subjects (15 pMTD, 15 controls) rated their vocal effort, vocal fatigue, vocal tract discomfort, odynophonia, and vocal quality on separate 100 mm visual analog scales (VAS) and completed the VFI-Part1 and VTDS. Cepstral peak prominences (CPP) were obtained from voice recordings of sustained /i/ and the all-voiced consensus of auditory-perceptual evaluation of voice (CAPE-V) sentence.

RESULTS

Patients with pMTD reported significantly higher severities of vocal effort (P < 0.0001), fatigue (P = 0.001), and discomfort (P = 0.0008) and scored significantly higher on both vocal indices (VFI-Part1: P < 0.0001; VTDS: P = 0.0056) compared to vocally healthy controls. Both indices had medium-to-high correlations with acute symptom severities in both groups. However, there were no significant differences between groups on odynophonia severity (P = 0.349), acoustic vocal quality (/i/: P = 1.00, CAPE-V: P = 0.228) or self-perceptual vocal quality (P = 0.141). There were also no significant relationships between vocal acoustics and patient symptoms or between vocal acoustics and standard vocal fatigue and vocal tract discomfort indices (P's > 0.05).

CONCLUSION

Somatosensory symptoms of vocal effort, vocal fatigue, and vocal tract discomfort are the most salient clinical features in patients with pMTD. Standard voice indices that capture more chronic symptoms can also reliably capture symptoms experienced at the time of the voice evaluation in patients with pMTD. Although odynophonia and aberrant acoustic vocal quality may be present in some patients with pMTD, they do not appear to be symptoms central to the condition. Because somatosensory experiences are more salient than vocal quality and vocal acoustics in pMTD, somatosensory symptoms of vocal effort, fatigue, and discomfort should hold more weight during the voice evaluation when pMTD is suspected.

Patient Motivation for Voice Therapy Increases After Stimulability Testing: Validation of a Voice Therapy Motivation and Voice Perception Inventory

OBJECTIVE

Measuring patient motivation for voice therapy is an important component of determining prognosis and estimating compliance. Voice stimulability testing is assumed to influence the patient's motivation by improving their perception of the sound and/or feel of the voice. The purpose of this study was to validate a Voice Therapy Motivation and Voice Perception Inventory and to determine whether stimulability testing elicits improvements in motivation and patient-perceived voice status.

METHOD

Seventy-five patients who underwent initial voice therapy evaluation completed a four-item inventory that queried their commitment to voice therapy, confidence that they could change their voice through voice therapy, perception of their voice severity, and ratings of their vocal effort. Inventories were completed shortly before and after stimulability testing. A psychometric analysis of the survey was conducted, including the internal consistency of each construct of the inventory along with content, predictive, and concurrent validity. Paired-samples statistical analyses were conducted to determine differences before and after stimulability testing, and Spearman correlations between voice and motivation ratings were conducted to determine relationships between the patient's perception of their voice and their motivation for voice therapy.

RESULTS

Internal consistency reliability was acceptable to good for each construct, particularly after stimulability testing. Motivation scales were predictive of returning for voice therapy sessions, subjective improvement of voice by the first therapy session, and likelihood of the patient practicing the home practice program. Patient ratings of voice severity and effort were positively correlated with clinician ratings of overall severity. Motivation and voice impairment perception improved following stimulability testing. Reduction in vocal effort was related to improved motivation, but change in voice severity was not.

CONCLUSIONS

Voice stimulability testing can influence patient motivation for voice therapy and patient-perceived voice improvements. It should be considered a critical part of the voice evaluation.

Hyolaryngeal Kinematics in Primary Muscle Tension Dysphonia Determined by Ultrasound

OBJECTIVES

The purpose of this study was to determine hyolaryngeal kinematics during voicing in people with primary muscle tension dysphonia (pMTD) compared with healthy speakers, and to investigate the relationships between hyolaryngeal displacement and self-perceived vocal function.

METHODS

Twenty-six participants, 13 with pMTD and 13 healthy speakers, were assessed using sonography during sustained vowel phonation and rest. Displacement of the hyoid bone and thyroid cartilage was measured from still frames extracted from ultrasound video recordings, with measures normalized to reflect change from rest during voicing for each participant. Vocal function was determined for all participants through self-perceived speaking effort and the Voice Handicap Index-10.

RESULTS

Normalized displacement of the hyoid bone and thyroid cartilage was significantly greater during voicing for participants with pMTD than for the healthy speakers. Weak-to-moderate, nonsignificant relationships between hyoid displacement and vocal function measures were evidenced, whereas moderate-to-strong, significant relationships were found for thyroid displacement and vocal function measures.

CONCLUSIONS

Displacement of the hyoid and elevation of the larynx during phonation appear to be prominent features of pMTD that differentiate the disorder from healthy phonatory kinematics. Ultrasound imaging provides a sensitive, reliable, noninvasive, and feasible method for objectively determining hyolaryngeal kinematics and may be useful for differential diagnosis and determination of treatment outcomes in pMTD.

Laryngeal and Global Somatosensation in Primary Muscle Tension Dysphonia

INTRODUCTION

Primary muscle tension dysphonia (pMTD) is a functional voice disorder that reduces communicative abilities and adversely impacts occupational productivity and quality of life. Patients with pMTD report increased vocal effort, fatigue, discomfort, and odynophonia. Although laryngeal and paralaryngeal muscle tension and hyperfunction are the most commonly proposed mechanisms underlying these symptoms, recent studies suggest pMTD may have more to do with the somatosensory system. However, relationships between voice symptoms and somatosensory mechanisms are poorly understood, creating challenges for mechanistic-based pMTD management. The first objective was to compare laryngeal, paralaryngeal, and global somatosensation between subjects with and without pMTD. The second was to determine relationships between pMTD symptoms and somatosensation.

METHODS

Fifty-two (20 pMTD and 32 control) subjects underwent laryngeal sensory testing with aesthesiometers, as well as peripheral mechanosensory and dynamic temporal summation testing to paralaryngeal and limb regions. Voice symptom severities (vocal effort, fatigue, discomfort, and odynophonia) were collected on 100-mm visual analog scales before and after laryngeal sensory testing. Participants also completed the Central Sensitization Inventory.

RESULTS

Patients with pMTD reported significantly higher laryngeal sensations (P = 0.0072) and voice symptom severities (P < 0.001) compared with the control group, and had significantly more vocal tract discomfort postlaryngeal sensory testing compared with the prelaryngeal sensory testing timepoint (P = 0.0023). However, there were no significant group differences in laryngeal airway protection responses suggestive of peripheral laryngeal hypersensitivities (P = 0.444). There were also no significant group differences on paralaryngeal or global sensitivities (P > 0.05), and no correlations between severity of voice symptoms and perceptual laryngeal sensations or hypersensitivities (P > 0.05).

CONCLUSION

Patients with pMTD perceive more sensitivities in the larynx and feel more sensations related to the voice (vocal effort, fatigue, discomfort, and pain). However, in general, patients with pMTD do not have abnormal peripheral laryngeal hypersensitivities, increased global somatosensation, or heightened central sensitivity. The lack of significant correlations between peripheral laryngeal hypersensitivities and voice symptom severity ratings suggests these outcome variables target distinct mechanistic constructs.

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.

Acoustic and Physiologic Correlates of Vocal Effort in Individuals With and Without Primary Muscle Tension Dysphonia

OBJECTIVES

The aims of this study were to determine relationships between vocal effort and (a) acoustic correlates of vocal output and (b) supraglottic compression in individuals with primary muscle tension dysphonia (pMTD) and without voice disorders (controls) in the context of a vocal load challenge.

METHOD

Twenty-six individuals with pMTD and 35 vocally healthy controls participated in a 30-min vocal load challenge. The pre- and postload relationships among self-ratings of vocal effort, various acoustic voice measures, and supraglottic compression (mediolateral and anteroposterior) were tested with multiple regression models and post hoc Pearson's correlations. Acoustic measures included cepstral peak prominence (CPP), low-to-high spectral ratio, difference in intensity between the first two harmonics, fundamental frequency, and sound pressure level (dB SPL).

RESULTS

Regression models for CPP and mediolateral compression were statistically significant. Vocal effort, diagnosis of pMTD, and vocal demand were each significant variables influencing CPP measures. CPP was lower in the pMTD group across stages. There was no statistical change in CPP following the vocal load challenge within either group, but both groups had an increase in vocal effort postload. Vocal effort and diagnosis influenced the mediolateral compression model. Mediolateral compression was higher in the pMTD group across stages and had a negative relationship with vocal effort, but it did not differ after vocal loading.

CONCLUSIONS

CPP and mediolateral supraglottic compression were influenced by vocal effort and diagnosis of pMTD. Increased vocal effort was associated with lower CPP, particularly after vocal load, and decreased mediolateral supraglottic compression in the pMTD group.