Objectives/hypothesis

Laryngeal adductor muscle dysfunction is a common cause of voice disorders. Reconstitution of adductor muscle function is often the target of therapy, but the effects of these muscles on voice production remain to be fully understood. This study investigated the differential roles of thyroarytenoid (TA) and lateral cricoarytenoid (LCA) muscles on voice production.

Study design

Basic science study using an in vivo canine model of phonation.

Methods

The TA and LCA muscle nerve branches were stimulated to obtain seven graded levels of muscle activation, from threshold to maximal contraction. The effects of LCA muscle activation alone, TA muscle activation alone, and combined TA and LCA muscle activation on phonation onset parameters were investigated. Phonatory posture, phonation onset type, fundamental frequency (F0), phonation onset pressure, and airflow were evaluated.

Results

LCA muscle activation closed the posterior glottis, but the midmembranous gap remained. TA muscle activation closed the membranous glottis, but the posterior gap remained. Complete glottal closure was obtained only with combined TA and LCA muscle activation. Phonation onset with the LCA muscle alone was characterized by multiple modes (soft, aperiodic, periodic), whereas with the TA muscle alone it was abrupt and periodic but had significant baseline noise. Combined muscle activation led to elimination of baseline noise with stable abrupt periodic onset of phonation. Combined muscle activation was also necessary for F0 variation. The LCA muscle assisted the TA muscle in increasing subglottal pressure while concurrently reducing phonation onset airflow.

Conclusions

The TA muscle is necessary for F0 variation, stable onset phonation, and increased subglottal pressure, but needs the LCA muscle for optimal effectiveness and to reduce airflow requirements with increased activation.

Level of evidence

NA.

Clinical intervention of glottal insufficiency often focuses on correcting glottal gap as visualized from above. In contrast, changes in medial surface shape due to intervention have received less attention. This study investigated how changes in medial surface shape affect voice production in excised human larynges, by locally medializing the medial surface at different longitudinal and vertical locations. The results showed that localized medialization at a more inferior location yielded better improvement in glottal closure and higher-order harmonic excitation in the produced voice. This study shows that surgical intervention of glottal insufficiency should also aim at restoring desirable medial surface shape.

Objectives

The objective of this study was to measure the elastic modulus (Young's modulus) of canine vocal fold cover layers.

Study design

Basic science study.

Methods

Cover layers from vocal folds of eight canine larynges were dissected. Cover layer samples from the mid-membranous, medial vocal fold surface area were used to measure material stiffness using a previously validated indentation method. Cover layers from two human larynges were also measured as control references. Superior and inferior medial cover layers were measured separately. A total of 15 superior medial surface and 17 inferior medial surface specimens from the canine and two and four specimens, respectively, from the human were tested.

Results

In the canine larynges, the mean Young's modulus of the superior medial surface was 4.2 kPa (range, 3.0-5.4 kPa; standard deviation [SD], 0.6 kPa) and of the inferior medial surface was 6.8 kPa (range, 5.4-8.5 kPa; SD, 0.8 kPa). Measurements on human cover samples were 5.0 kPa (range, 4.7-5.4 kPa; SD, 0.5 kPa) and 7.0 kPa (range, 6.7-7.3 kPa; SD, 0.3 kPa) for the superior medial and inferior medial surface, respectively. Human measurements were similar to the previously validated measurements. There was no difference between the stiffness measurements in the human and canine cover layer samples (P>0.05).

Conclusions

The elastic stiffness (Young's modulus) of the canine and human vocal fold cover layers is similar. Findings support the use of canine larynx as an externally valid model to study voice production.

Objectives/hypothesis

The posterior cricoarytenoid (PCA) muscle is the sole abductor of the glottis and serves important functions during respiration, phonation, cough, and sniff. The present study examines vocal fold abduction dynamics during PCA muscle activation.

Study design

Basic science study using an in vivo canine model and human subjects.

Methods

In four canines and five healthy humans vocal fold abduction time was measured using high-speed video recording. In the canines, PCA muscle activation was achieved using graded stimulation of the PCA nerve branch. The human subjects performed coughing and sniffing tasks. High-speed video and audio signals were concurrently recorded.

Results

In the canines, the vocal fold moved posteriorly, laterally, and superiorly during abduction. Average time to reach 10%, 50%, and 90% abduction was 23, 50, and 100 ms with low stimulation; 24, 58, and 129 ms with medium stimulation; and 21, 49, and 117 ms with high-level stimulation, respectively. In the humans, 100% abduction times for coughing and sniffing tasks were 79 and 193 ms, respectively.

Conclusions

The PCA abduction times in canines are within the range in humans. The results also further support the notion that PCA muscles are fully active during cough.

Objectives/hypothesis

Fundamental frequency (F0) and intensity sound pressure level (SPL) of voice are controlled by intrinsic laryngeal muscle (ILM) activation and subglottal pressure (Psub). Their interactions were investigated.

Methods

In an in vivo canine model, the thyroarytenoid (TA), lateral cricoarytenoid/interarytenoid (LCA/IA), and cricothyroid (CT) muscles were independently activated from threshold to maximal contraction by neuromuscular stimulation in various combinations, whereas airflow was increased to phonation onset pressure and beyond. The resultant acoustic output was analyzed for effects of Psub on vibratory stability, F0, and SPL. Muscle activation plots and vocal range profiles by individual ILM activation states were analyzed.

Results

Cricothyroid activation increased phonation onset F0, but vibration was less stable in high CT conditions and displayed vibratory mode change. In addition, a decrease in F0 with increased Psub was observed in high CT conditions. Intensity increased with Psub in all conditions, but the slope was greater at high CT, low TA/LCA/IA activations. Lateral cricoarytenoid/interarytenoid activation improved vocal efficiency. To maintain same F0 with increasing SPL (messa di voce), TA activation was decreased and LCA/IA activation was increased. The same F0 and SPL could be achieved with a variety of ILM activation combinations.

Conclusion

Cricothyroid is primarily required for increasing F0, whereas TA can increase or decrease F0 and SPL. Lateral cricoarytenoid/interarytenoid activation likely maintains vocal fold adduction during increased Psub and improves vocal efficiency. This study also demonstrates laryngeal motor equivalence, the ability of the larynx to achieve the same target F0 and SPL with multiple combinations of ILM activation.

Level of evidence

N/A. Laryngoscope, 126:1123-1130, 2016.

Purpose of review

The superior laryngeal nerve (SLN) provides motor innervation to the cricothyroid muscle. However, the functions of this muscle and the anatomic variations of the nerve that supplies it are not fully understood. SLN paresis and paralysis (SLNp) is difficult to diagnose because of a lack of consistent laryngeal findings, and its effects on the voice likely go beyond simple pitch elevation control.

Recent findings

Although SLNp has traditionally been thought to lead to voice pitch limitation, recent research findings reveal multiple roles for this nerve in voice and speech. Cricothyroid muscles are the primary controls of fundamental frequency of voice. SLNp can lead to significant contraction of pitch range, vocal fold vibratory phase asymmetry, and acoustic aperiodicity, thus leading to an overall poor vocal quality. In addition, cricothyroid muscles may also play a role in pitch lowering and shifting from voiced to unvoiced sounds during speech.

Summary

Subtle signs, symptoms, and diagnostic findings associated with SLNp make this disorder difficult to characterize clinically. Lack of treatment methodologies to restore the dynamic action of the cricothyroid muscles poses difficulties in treating patients with this condition. A more thorough understanding of the effects of SLNp will improve diagnosis and treatment.

Introduction

In speech and singing, the intrinsic laryngeal muscles set the prephonatory posture prior to the onset of phonation. The timing and shape of the prephonatory glottal posture can directly affect the resulting phonation type. We investigated the dynamics of human laryngeal phonatory posturing.

Methods

Onset of vocal fold adduction to phonation was observed in 27 normal subjects using high-speed video recording. Subjects were asked to utter a variety of phonation types (modal, breathy, pressed, /i/ following sniff). Digital videokymography with concurrent acoustic signal was analyzed to assess the timing of the following: onset of adduction to final phonatory posture (FPT), phonation onset time (POT), and phonatory posture time (PPT). Final phonatory posture time was determined as the moment at which the laryngeal configuration used in phonation was first achieved.

Results

Thirty-three audiovisual recordings met inclusion criteria. Average FPT, PPT, and POT were as follows: 303, 106, and 409 ms for modal; 430, 104, and 534 ms for breathy; 483, 213, and 696 ms for pressed; and 278, 98, and 376 ms for sniff-/i/. The following posturing features were observed: 1) pressed phonation: increased speed of closure just prior to final posture, complete glottal closure, and increased supraglottic hyperactivity; and 2) breathy phonation: decreased speed of closure prior to final posture, increased posterior glottal gap, and increased midmembranous gap.

Conclusions

Phonation onset latency was shortest for modal and longest for pressed voice. These findings are likely explained by glottal resistance and subglottal pressure requirements.

Level of evidence

NA. Laryngoscope, 126:1837-1843, 2016.

Objectives

To determine symptoms and findings in patients with dysphagia related to epiglottic dysfunction. To analyze outcomes in patients who underwent partial epiglottidectomy due to dysphagia related to epiglottic dysfunction.

Study design

Review and analysis of clinical data obtained as part of the diagnosis and treatment of patients with dysphagia related to epiglottic dysfunction.

Methods

A retrospective review was performed of all post-treatment head and neck cancer patients who underwent epiglottidectomy at a single tertiary care referral center. Objective pre- and postprocedure swallow findings, endoscopic evaluation, and subjective improvement based on patient self-reports were reviewed.

Results

Seven patients were identified based on endoscopic evaluation and modified barium swallow study (MBSS) as having epiglottic pathology leading to dysphagia. Specific anatomic and functional findings included thickening of the epiglottis, absence of epiglottic deflection, vallecular bolus retention during and after the swallow, and bolus backflow from the pharynx to the oral or nasal cavity. Partial epiglottidectomy was performed in these patients. Postoperative MBSS was analyzed for changes in swallow efficiency and safety. Nearly all patients demonstrated improved pharyngeal bolus passage with little to no added swallowing morbidity.

Conclusions

Preliminary findings suggest a role for partial epiglottidectomy in post-treatment head and neck cancer patients with swallowing disorders. Ideal candidates have intact tongue base contraction and poor retroflexion of the epiglottis, which results in bolus obstruction at the level of the valleculae. Partial epiglottic resection enables improved bolus passage in the pharyngeal phase. Minimal postoperative morbidity occurs in the appropriately selected patient.

Purpose

To review our clinical experience with percutaneous injection laryngoplasty at a single institution over a three-year period, and to specifically assess the rate of unintentional injection into the superficial lamina propria (SLP) and compare with results found in the literature.

Materials and methods

Medical records were retrospectively reviewed to identify patients who underwent office-based injection laryngoplasty (OBIL) over a three-year period. Video documentation and the written notes of the procedures were reviewed to determine the rate of inadvertent placement of injectate into the SLP. A literature review was performed to identify other reports of this complication and contributing factors.

Results

113 consecutive patients were identified who underwent OBIL in the study period. Of these, 100 patients had adequate records and follow-up available for this review. All patients underwent injection augmentation with bovine collagen using a percutaneous trans-membrane or trans-cartilaginous technique. 96 had improvement in their vocal quality and/or effort. Four patients, who were all women, had unintentional injection into the SLP with resultant no change in voice or worsened voice. All superficially placed injectates were managed conservatively.

Conclusions

Injection into the SLP is a well-recognized possible complication of OBIL. Our results suggest that this complication occurs more often in women than in men, perhaps due to differing laryngeal anatomy and size.

Objectives/hypothesis

Arytenoid adduction (AA) is performed to treat unilateral vocal fold paralysis with a large posterior glottal gap. However, the voice effects of AA suture position remain unclear. This study aimed to evaluate voice production and quality as a function of AA suture position on the thyroid ala in a neuromuscularly intact in vivo larynx.

Study design

Animal model.

Methods

Unilateral recurrent laryngeal nerve and vagal paralysis were modeled in two canines. AA suture position was varied across five equidistant positions on the anterior inferior thyroid ala, from a paramedian position anteriorly to the oblique line posteriorly. Phonation was performed over 8 × 8 graded level combinations of recurrent and superior laryngeal nerve stimulation per suture position. The primary outcome was percent successful phonatory conditions. Secondary outcomes included fundamental frequency (F0), phonation onset pressure (PTP), cepstral peak prominence (CPP), and laryngeal posture.

Results

Anterior suture positions resulted in a greater percentage of successful phonatory conditions compared to posterior sutures. Suture position 2, located at the anterior inferior thyroid ala, resulted in the highest percentage of successful phonatory conditions, lowest PTP, and lower muscle activation levels to achieve higher CPP. Posterior sutures resulted in wider glottal gap and more effective F0 and vocal fold strain increase with cricothyroid muscle contraction, but with fewer successful phonatory conditions and higher PTP. Trends were consistent across both paralysis types.

Conclusions

AA suture placed in the anterior inferior thyroid ala resulted in the best acoustic, aerodynamic, and voice quality outcomes. This study provides scientific evidence for maintaining current clinical practice.

Level of evidence

NA Laryngoscope, 131:846-852, 2021.