Register transitions in an in vivo canine model as a function of intrinsic laryngeal muscle stimulation, fundamental frequency, and sound pressure level.

Phonatory instabilities and involuntary register transitions can occur during singing. However, little is known regarding the mechanisms which govern such transitions. To investigate this phenomenon, we systematically varied laryngeal muscle activation and airflow in an in vivo canine larynx model during phonation. We calculated voice range profiles showing average nerve activations for all combinations of fundamental frequency (F0) and sound pressure level (SPL). Further, we determined closed-quotient (CQ) and minimum-posterior-area (MPA) based on high-speed video recordings. While different combinations of muscle activation favored different combinations of F0 and SPL, in the investigated larynx there was a consistent region of instability at about 400 Hz which essentially precluded phonation. An explanation for this region may be a larynx specific coupling between sound source and subglottal tract or an effect based purely on larynx morphology. Register transitions crossed this region, with different combinations of cricothyroid and thyroarytenoid muscle (TA) activation stabilizing higher or lower neighboring frequencies. Observed patterns in CQ and MPA dependent on TA activation reproduced patterns found in singers in previous work. Lack of control of TA stimulation may result in phonation instabilities, and enhanced control of TA stimulation may help to avoid involuntary register transitions, especially in the singing voice.

Heterogeneous Presentations of Pharyngoesophageal Diverticula Occurring after Cervical Spine Surgery.

Dysphagia after anterior cervical spine surgery (ACSS) may be secondary to pharyngoesophageal diverticulum. Our objectives are to (1) highlight the heterogeneity in clinical presentation, (2) discuss pathophysiology and management, and (3) present a comprehensive literature review of these diverticula. All patients undergoing pharyngoesophageal diverticulum repair between 2013 and 2019 were identified. Cases with ACSS history underwent detailed review of clinical presentation, assessment, and management. Literature review and analysis of all reported ACSS-associated pharyngoesophageal diverticula was performed. Two hundred forty-three cases of pharyngoesophageal diverticulum repair were performed during the study period; 13 cases were ACSS-associated. Four types of clinical presentation were identified: (Type A) Spinal hardware present, with videofluoroscopic evidence of exposed hardware; (Type B) Spinal hardware present, without videofluoroscopic evidence of exposed hardware; (Type C) Spinal hardware absent due to prior spinal hardware removal or ACSS performed without hardware; and (Type D) Concurrent esophago-esophageal fistula (EEF) present. All of our cases were evaluated using modified barium swallow study and esophagoscopy and definitively managed with endoscopic diverticulotomy. Literature review identified 21 cases of ACSS-associated pharyngoesophageal diverticulum repair from 18 publications. The majority of cases were identified using barium esophagram (N = 18, 86%) and managed with open diverticulectomy (N = 19, 90%). There were no reports of EEF. ACSS-associated pharyngoesophageal diverticulum must be evaluated with fluoroscopy and endoscopy, which determine presentation type. Presentation type guides management. Esophageal perforation requires hardware removal and perforation repair with flap placement. Endoscopic diverticulotomy was found essential to definitive management.Level of Evidence: 4.

Effect of changes in medial surface shape on voice production in excised human larynges.

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.

Utility of the transnasal esophagoscope in the management of chemoradiation-induced esophageal stenosis.

OBJECTIVE: This study aimed to describe management of esophageal stenosis after chemoradiation therapy for head and neck squamous cell carcinoma (HNSCC), with particular emphasis on techniques and outcomes with the use of the transnasal esophagoscope (TNE) in the office as well as operating room settings. METHODS: Retrospective analysis of all patients with esophageal stenosis following head and neck cancer radiation, with or without chemotherapy, and managed with TNE-assisted esophageal dilation over a 5-year period. Preoperative and postoperative swallowing function were assessed objectively with the Functional Outcome Swallowing Scale (FOSS; ranging from score 0, a normal diet, to score 5, complete dependence on nonoral nutrition). RESULTS: Twenty-five patients met inclusion criteria. The mean pretreatment FOSS score was 4.4, whereas the mean posttreatment FOSS score was 2.7 (Wilcoxon signed-rank test, P<.001). Prior to dilation, 16 patients were completely gastrostomy-tube dependent (FOSS 5), of whom 12 (75%) were able to tolerate oral nutrition for a majority of their diet following treatment according to our protocol. No complications were noted. CONCLUSION: Dysphagia following chemoradiation therapy for HNSCC is often related to esophageal stenosis. With the aid of TNE, we have developed a successful treatment strategy for esophageal stenosis with improved success rates.

A comparative study of cricotracheal resection and staged laryngotracheoplasty for adult subglottic stenosis.

OBJECTIVE: Cricotracheal resection (CTR) and laryngotracheoplasty (LTP) are open surgical treatments for severe subglottic stenosis. This study aims to compare the applications and outcomes of these techniques. METHOD: Patients with subglottic stenosis at a tertiary academic institution from 2000 to 2012 were identified by diagnosis codes. Patients who underwent LTP or CTR were included. Records were reviewed for treatment data and outcomes. Patients with a history of head and neck malignancy or stenosis without cricoid involvement were excluded. RESULT: Sixty-one and 20 patients underwent LTP and CTR, respectively. When comparing patients receiving LTP and CTR, there was a significant difference in stenosis etiology (P=.014). The groups were similar in Cotton-Myer grade (P=.102). At last follow-up, 80.3% of LTP patients and 90.0% of CTR patients were decannulated. On multivariate analysis, there was a significant association between stenosis grade and decannulation in the LTP group (P=.01). Decannulation was not associated with stenosis grade in the CTR group. In both groups, there was no significant association between decannulation and sex, stenosis etiology, or stenosis length. CONCLUSION: Cricotracheal resection and LTP have both shown excellent long-term decannulation rates. Etiology and stenosis grade are likely to be determining factors when recommending specific surgical interventions for subglottic stenosis.

Airway management and endoscopic treatment of subglottic and tracheal stenosis: the laryngeal mask airway technique.

OBJECTIVES: The objective is to present clinical outcomes of subglottic and tracheal stenosis treated by flexible bronchoscopic delivery of carbon dioxide (CO2) laser via laryngeal mask airway (LMA). METHODS: All consecutive, nontracheotomy dependent cases of subglottic and tracheal stenosis treated endoscopically over a 4-year period were retrospectively reviewed. The surgical approach consisted of radial incisions using a flexible fiber-based CO2 laser, balloon dilation, and topical application of mitomycin C. Ventilation during the procedure occurred through the LMA, and the CO2 laser fiber was delivered through the working channel of a flexible bronchoscope passed through the LMA. Number of dilations, period between dilations, and operative times were reviewed. RESULTS: Eleven patients who underwent airway intervention during the study period were identified. Average follow-up was 28 months. Etiologies of airway stenosis included intubation injury (6), idiopathic (4), or autoimmune disease (1), requiring an average of 1.3, 1.5, and 3 dilations, respectively. Average operative time was 67 minutes. Autoimmune etiology correlated with more frequent dilations. CONCLUSION: LMA is an effective way to manage ventilation while simultaneously allowing unencumbered flexible bronchoscopic access for laser surgery, balloon dilation, and mitomycin C application for airway stenosis. Long-term success in treating stenosis is achievable using this technique.

Higher risk of superficial injection during injection laryngoplasty in women.

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.

Office-based tracheoesophageal puncture: updates in techniques and outcomes.

PURPOSE: Tracheoesophageal puncture (TEP) is an effective rehabilitation method for postlaryngectomy speech and has already been described as a procedure that is safely performed in the office. We review our long-term experience with office-based TEP over the past 7 years in the largest cohort published to date. MATERIALS AND METHODS: A retrospective chart review was performed of all patients who underwent TEP by a single surgeon from 2005 through 2012, including office-based and operating room procedures. Indications for the chosen technique (office versus operating room) and surgical outcomes were evaluated. RESULTS: Fifty-nine patients underwent 72 TEP procedures, with 55 performed in the outpatient setting and 17 performed in the operating room, all without complication. The indications for performing TEPs in the operating room included 2 primary TEPs, 14 due to concomitant procedures requiring general anesthesia, and 1 due to failed attempt at office-based TEP. Nineteen patients with prior rotational or free flap reconstruction successfully underwent office-based TEP. CONCLUSIONS: TEP in an office-based setting with immediate voice prosthesis placement continues to be a safe method of voice rehabilitation for postlaryngectomy patients, including those who have previously undergone free flap or rotational flap reconstruction. Office-based TEP is now our primary approach for postlaryngectomy voice rehabilitation.

Influence and interactions of laryngeal adductors and cricothyroid muscles on fundamental frequency and glottal posture control.

The interactions of the intrinsic laryngeal muscles (ILMs) in controlling fundamental frequency (F0) and glottal posture remain unclear. In an in vivo canine model, three sets of intrinsic laryngeal muscles-the thyroarytenoid (TA), cricothyroid (CT), and lateral cricoarytenoid plus interarytenoid (LCA/IA) muscle complex-were independently and accurately stimulated in a graded manner using distal laryngeal nerve stimulation. Graded neuromuscular stimulation was used to independently activate these paired intrinsic laryngeal muscles over a range from threshold to maximal activation, to produce 320 distinct laryngeal phonatory postures. At phonation onset these activation conditions were evaluated in terms of their vocal fold strain, glottal width at the vocal processes, fundamental frequency (F0), subglottic pressure, and airflow. F0 ranged from 69 to 772 Hz and clustered into chest-like and falsetto-like groups. CT activation was always required to raise F0, but could also lower F0 at low TA and LCA/IA activation levels. Increasing TA activation first increased then decreased F0 in all CT and LCA/IA activation conditions. Increasing TA activation also facilitated production of high F0 at a lower onset pressure. Independent control of membranous (TA) and cartilaginous (LCA/IA) glottal closure enabled multiple pathways for F0 control via changes in glottal posture.

A Novel Hybrid Procedure Combining Resection and Tracheoplasty for Complex Laryngotracheal Stenosis.

Adult airway stenosis is a common condition treated in the otolaryngology clinic. Patients with high-grade, long-segment stenosis often fail endoscopic management. We describe the successful use of a hybrid resection and laryngotracheoplasty procedure that maximizes airway luminal patency in adults with successful decannulation. Laryngoscope, 2024.

Heterogeneous Presentations and Serologies in Myasthenia Gravis Patients Presenting with Dysphagia.

INTRODUCTION: Myasthenia gravis (MG) is an autoimmune disease that affects the neuromuscular junction. MG patients may present de novo with primary otolaryngology complaints, including swallowing dysfunction. This study describes a range of unique presentations and rare diagnostic serologies, which have not previously been fully described. METHODS: A retrospective review was performed of all patients presenting with primary symptom of dysphagia and subsequently diagnosed with MG. Data collected included demographics, clinical presentation, swallow studies, serology, imaging, treatment, and response. RESULTS: Five patients met the inclusion criteria. Four endorsed dysphagia as primary complaint and one endorsed dysphagia and dysphonia. All patients underwent in-office swallow evaluations that showed vallecular or pyriform sinus residue. Three patients completed modified barium swallow studies that showed pharyngeal weakness and epiglottic dysfunction in all, and upper esophageal sphincter dysfunction in two. One patient with additional symptom of dyspnea was admitted and found to be in myasthenic crisis. Upon serologic evaluation, three patients were positive for acetylcholine receptor (AChR) antibodies only, one for muscle-specific-kinase (MuSK) antibodies only, and one for low density lipoprotein receptor-related protein 4 (LRP4) antibodies only. All patients received neurology evaluation and were treated with steroids, pyridostigmine, plasma exchange, or rituximab. In three patients with over 1 year follow-up, symptoms were significantly improved or resolved. CONCLUSION: MG is an important differential diagnosis in patients with unexplained pharyngeal dysphagia. While workup can include AChR antibody screening, in seronegative patients with persistent symptoms, additional testing for MuSK and LRP4 may lead to diagnosis and effective treatment. LEVEL OF EVIDENCE: Level 4 Laryngoscope, 2024.

Reconstruction of Vocal Fold Medial Surface 3D Trajectories: Effects of Neuromuscular Stimulation and Airflow.

INTRODUCTION: Analysis of medial surface dynamics of the vocal folds (VF) is critical to understanding voice production and treatment of voice disorders. We analyzed VF medial surface vibratory dynamics, evaluating the effects of airflow and nerve stimulation using 3D reconstruction and empirical eigenfunctions (EEF). STUDY DESIGN: In vivo canine hemilarynx phonation. METHODS: An in vivo canine hemilarynx was phonated while graded stimulation of the recurrent and superior laryngeal nerves (RLN and SLN) was performed. For each phonatory condition, vibratory cycles were 3D reconstructed from tattooed landmarks on the VF medial surface at low, medium, and high airflows. Parameters describing medial surface trajectory shape were calculated, and underlying patterns were emphasized using EEFs. Fundamental frequency and smoothed cepstral peak prominence (CPPS) were calculated from acoustic data. RESULTS: Convex-hull area of landmark trajectories increased with increasing flow and decreasing nerve activation level. Trajectory shapes observed included circular, ellipsoid, bent, and figure-eight. They were more circular on the superior and anterior VF, and more elliptical and line-like on the inferior and posterior VF. The EEFs capturing synchronal opening and closing (EEF1) and alternating convergent/divergent (EEF2) glottis shapes were mostly unaffected by flow and nerve stimulation levels. CPPS increased with higher airflow except for low RLN activation and very dominant SLN stimulation. CONCLUSION: We analyzed VF vibration as a function of neuromuscular stimulation and airflow levels. Oscillation patterns such as figure-eight and bent trajectories were linked to high nerve activation and flow. Further studies investigating longer sections of 3D reconstructed oscillations are needed. LEVEL OF EVIDENCE: N/A, Basic Science Laryngoscope, 134:1249-1257, 2024.

Total tracheoesophageal puncture failure: A scoping review of patient characteristics and etiologies.

OBJECTIVES: Tracheoesophageal prosthesis (TEP) is a common method for post-laryngectomy speech rehabilitation. Despite its common use, some patients ultimately fail TEP rehabilitation. TEP dysfunction negatively affects quality of life due to poor voice quality and need for repeated interventions to restore TEP function. Occasionally, voice rehabilitation with TEP is completely unsuccessful. We performed a scoping review to characterize the main reasons for total TEP failure, in hopes of guiding selection of optimal TEP candidates. STUDY DESIGN: Scoping review using PubMed of all English language articles from 1990 to 2020 addressing causes of TEP failure. METHODS: This scoping review followed the population, intervention, comparison, outcome and study (PICOS) guidelines. Total TEP failure was defined as complete loss or abandonment of TEP voice or tract. A comprehensive search strategy using PubMed's MeSH subject headings and keywords was created. Causes and rates of failure were reviewed. RESULTS: Among 544 peer-reviewed journal articles reviewed for inclusion. Seventy articles met inclusion criteria, resulting in a total of 4928 TEP voice restoration patients for analysis. 15.2% of these patients had total TEP failure. The most common reasons for failure were dissatisfaction with voice (26.3%), leakage (17.9%), inadequate patient motivation (14.7%), comorbidities (14.2%), stoma problems (11.6%), and abandonment of TEP after dislodgement (10.6%). CONCLUSION: Common reasons for TEP failure included voice dissatisfaction, leakage, lack of patient motivation, patient comorbidities, and stoma problems. These factors should be considered when selecting candidates for TEP voice restoration.

Histologic Examination of Vocal Fold Mucosal Wave and Vibration.

OBJECTIVES: Despite gross anatomic and histologic differences between human and canine vocal folds, similar wave patterns have been described yet not fully characterized. We reconstructed vocal fold (VF) vibration in a canine hemilarynx and performed histologic examination of the same vocal fold. We demonstrate comparable wave patterns while exploring the importance of certain anatomic architectures. METHODS: An in vivo canine hemilarynx was phonated against a glass prism at low and high muscle activation conditions. Vibration was captured using high-speed video, and trajectories of VF medial surface tattooed landmarks were 3D-reconstructed. The method of empirical eigenfunctions was used to capture the essential dynamics of vibratory movement. Histologic examination of the hemilarynx was performed. RESULTS: Oscillation patterns were highly similar between the in vivo canine and previous reports of ex vivo human models. The two most dominant eigenfunctions comprised over 90% of total variance of movement, representing opening/closing and convergent/divergent movement patterns, respectively. We demonstrate a vertical phase difference during the glottal cycle. The time delay between the inferior and superior VF was greater during opening than closing for both activation conditions. Histological examination of canine VF showed not only a thicker lamina propria layer superiorly but also a distinct pattern of thyroarytenoid muscle fibers and fascicles as described in human studies. CONCLUSIONS: Histologic and vibratory examination of the canine vocal fold demonstrated human vocal fold vibratory patterns despite certain microstructural differences. This study suggests that the multilayered lamina propria may not be fundamental to vibratory patterns necessary for human-like voice production. LEVEL OF EVIDENCE: NA (Basic science study) Laryngoscope, 134:264-271, 2024.

Effects of Thyroarytenoid Activation Induced Vibratory Asymmetry on Voice Acoustics and Perception.

INTRODUCTION: Asymmetry of vocal fold (VF) vibration is common in patients with voice complaints and also observed in 10% of normophonic individuals. Although thyroarytenoid (TA) muscle activation plays a crucial role in regulating VF vibration, how TA activation asymmetry relates to voice acoustics and perception is unclear. We evaluated the relationship between TA activation asymmetry and the resulting acoustics and perception. METHODS: An in vivo canine model of phonation was used to create symmetric and increasingly asymmetric VF vibratory conditions via graded stimulation of bilateral TA muscles. Naïve listeners (n = 89) rated the perceptual quality of 100 unique voice samples using a visual sort-and-rate task. For each phonatory condition, cepstral peak prominence (CPP), harmonic amplitude (H1-H2), and root-mean-square (RMS) energy of the voice were measured. The relationships between these metrics, vibratory asymmetry, and perceptual ratings were evaluated. RESULTS: Increasing levels of TA asymmetry resulted in declining listener preference. Furthermore, only severely asymmetric audio samples were perceptually distinguishable from symmetric and mildly asymmetric conditions. CPP was negatively correlated with TA asymmetry: voices produced with larger degrees of asymmetry were associated with lower CPP values. Listeners preferred audio samples with higher values of CPP, high RMS energy, and lower H1-H2 (less breathy). CONCLUSION: Listeners are sensitive to changes in voice acoustics related to vibratory asymmetry. Although increasing vibratory asymmetry is correlated with decreased perceptual ratings, mild asymmetries are perceptually tolerated. This study contributes to our understanding of voice production and quality by identifying perceptually salient and clinically meaningful asymmetry. LEVEL OF EVIDENCE: N/A (Basic Science Study) Laryngoscope, 134:1327-1332, 2024.

Speech and Swallowing Outcomes of Surgically Managed Cervical Chordoma: A Case Series.

OBJECTIVES: Cervical chordoma is a rare, low-grade primary bone tumor occurring in the axial skeleton. Due to challenges in surgical exposure caused by anatomic location, patients may experience dysfunction in speech and swallowing. The objective of this study was to characterize speech and swallowing outcomes for patients undergoing surgical resection of cervical chordoma. Moreover, we detail in-depth two cases with similar initial presentations to compare prognostic factors and management strategies. METHODS: Eleven patients with histologically confirmed cervical chordoma treated between 1993 and 2020 were included in this retrospective case series. Outcomes measured included overall survival, disease-free survival, need for enteral feeds, as well as results of modified barium swallow study (MBSS) and fiberoptic laryngoscopy. RESULTS: The mean age at diagnosis was 55.9 years. The patient population was 81.8% male. Mean survival after diagnosis was 96 months. Four (36.4%) patients required post-operative MBSS and demonstrated aspiration. All four of these patients presented with tumors in the superior cervical spine and received surgeries utilizing anterior approaches. Of the four, 2 required enteral feeds long-term. Four (36.4%) patients endorsed dysphonia. One patient developed post-operative right vocal fold paresis. The remaining three patients experienced stable dysphonia pre- and post-operatively. Additionally, three (27%) patients required tracheostomy placement, two of which remained in place long-term. CONCLUSIONS: Dysphagia is a common side effect of cervical chordoma resection. It is associated with the use of an anterior approach during resection and with tumors located in the superior cervical spine. Patients with postoperative dysphagia should receive early multidisciplinary swallow rehabilitation. LEVEL OF EVIDENCE: 4 Laryngoscope, 134:3706-3712, 2024.

Risk Analysis Index Frailty Score as a Predictor of Otolaryngology Surgical Outcomes.

OBJECTIVE: The Risk Analysis Index (RAI) score is a screening tool to assess patient frailty. It has been shown to be predictive of postoperative outcomes and mortality in orthopedic, urologic, and neurosurgical patient populations. We sought to evaluate the predictive ability of RAI score for surgical outcomes in an otolaryngology patient population. STUDY DESIGN: Retrospective study. SETTING: Academic tertiary medical center. METHODS: A retrospective study was conducted of adult patients undergoing otolaryngology surgery at a tertiary medical care center over 21 months. Patients were sent electronic RAI survey questionnaires via direct messaging, which was completed prior to surgery. Endpoint data were analyzed, including demographics, RAI score, and patient outcome data. Univariate analysis, ROC curves, and predictive modeling were utilized. RESULTS: A total of 517 patients responded to the RAI questionnaire, resulting in a 59.6% response rate. Mean RAI score was 21.38 ± 11.83. Higher RAI scores were associated with increased 30-day readmissions (P < .0015), postoperative complications (P < .001), hospital length of stay (P < .001), and discharge with home health (P < .001). Predictive models for RAI score and postoperative outcomes were created, and a cutoff score of RAI = 30 was established to identify frail patients. CONCLUSION: We evaluated if RAI scoring predicted postoperative complications in an otolaryngology patient population. Increased RAI score is significantly associated with poorer surgical outcomes, including increased hospital length of stay, 30-day readmissions, and postoperative complications. We propose a predictive model with suggested RAI cutoff scoring for use in the otolaryngology surgical population.

3D Reconstruction of Phonatory Glottal Shape and Volume: Effects of Neuromuscular Activation.

INTRODUCTION: Although phonatory glottal posture and airflow pulse shape affect voice quality, studies to date have been limited by visualization of vocal fold (VF) vibration from a superior view. We performed a 3D reconstruction of VF vibratory motion during phonation from a medial view and assessed the glottal volume waveform and resulting acoustics as a function of neuromuscular stimulation. STUDY DESIGN: In vivo canine hemilarynx phonation. METHODS: Across 121 unique combinations of the superior laryngeal nerve (SLN) and recurrent laryngeal nerve (RLN) stimulation, the hemilarynx was excited to the oscillation with airflow. VF medial surface reference points were tracked on high-speed video, mapped into 3D space, and surface shape was restored using cubic spline interpolation. Glottal surface shape, reconstruction-based parameters, and glottal volume waveform were calculated. Fundamental frequency (F0), cepstral peak prominence (CPP), and harmonic amplitude (H1-H2) were measured from high-quality audio samples. RESULTS: The glottis was convergent during opening and divergent during closing. Neuromuscular activation changed phonatory glottal shape and reduced glottal volume. Significant reduction in glottal volume and closing quotient were present with SLN stimulation. RLN stimulation significantly increased F0 and CPP and decreased H1-H2 (constricted glottis), while SLN effects were similar and synergistic with concurrent RLN stimulation. CONCLUSION: 3D reconstruction of in vivo medial surface vibration revealed effects of laryngeal nerve stimulation on glottal vibratory pattern and acoustic correlates of voice quality. SLN activation resulted in significantly quicker glottal closure per cycle, decreased glottal volume, and higher-pitched, less breathy, and less noisy voice. RLN had a similar effect on acoustic measures. LEVEL OF EVIDENCE: NA, Basic Science Laryngoscope, 133:357-365, 2023.

Validation and enhancement of a vocal fold medial surface 3D reconstruction approach for in-vivo application.

In laryngeal research, studying the vertical vocal fold oscillation component is often disregarded. However, vocal fold oscillation by its nature is a three-dimensional process. In the past, we have developed an in-vivo experimental protocol to reconstruct the full, three-dimensional vocal fold vibration. The goal of this study is to validate this 3D reconstruction method. We present an in-vivo canine hemilarynx setup using high-speed video recording and a right-angle prism for 3D reconstruction of vocal fold medial surface vibrations. The 3D surface is reconstructed from the split image provided by the prism. For validation, reconstruction error was calculated for objects located at a distance of up to 15 mm away from the prism. The influence of camera angle, changing calibrated volume, and calibration errors were determined. Overall average 3D reconstruction error is low and does not exceed 0.12 mm at 5 mm distance from the prism. Influence of a moderate (5°) and large (10°) deviation in camera angle led to a slight increase in error to 0.16 mm and 0.17 mm, respectively. This procedure is robust towards changes in calibration volume and small calibration errors. This makes this 3D reconstruction approach a useful tool for the reconstruction of accessible and moving tissue surfaces.

Control of Pre-phonatory Glottal Shape by Intrinsic Laryngeal Muscles.

OBJECTIVES: Surgical manipulations to treat glottic insufficiency aim to restore the physiologic pre-phonatory glottal shape. However, the physiologic pre-phonatory glottal shape as a function of interactions between all intrinsic laryngeal muscles (ILMs) has not been described. Vocal fold posture and medial surface shape were investigated across concurrent activation and interactions of thyroarytenoid (TA), cricothyroid (CT), and lateral cricoarytenoid/interarytenoid (LCA/IA) muscles. STUDY DESIGN: In vivo canine hemilarynx model. METHODS: The ILMs were stimulated across combinations of four graded levels each from low-to-high activation. A total of 64 distinct medial surface postures (4 TA × 4 CT × 4 LCA/IA levels) were captured using high-speed video. Using a custom 3D interpolation algorithm, the medial surface shape was reconstructed. RESULTS: Combined activation of ILMs yielded a range of unique pre-phonatory postures. Both LCA/IA and TA activation adducted the vocal fold but with greater contribution from TA. The transition from a convergent to a rectangular glottal shape was primarily mediated by TA muscle activation but LCA/IA and TA together resulted in a smooth rectangular glottis compared to TA alone, which caused rectangular glottis with inferomedial bulging. CT activation resulted in a lengthened but slightly abducted glottis. CONCLUSIONS: TA was primarily responsible for the rectangular shape of the adducted glottis with synergistic contribution from the LCA/IA. CT contributed minimally to vocal fold medial shape but elongated the glottis. These findings further refine laryngeal posture goals in surgical correction of glottic insufficiency. LEVEL OF EVIDENCE: NA, Basic science Laryngoscope, 133:1690-1697, 2023.