Lateral Cricoarytenoid Research Articles

Deep Learning for Neuromuscular Control of Vocal Source for Voice Production.

A computational neuromuscular control system that generates lung pressure and three intrinsic laryngeal muscle activations (cricothyroid, thyroarytenoid, and lateral cricoarytenoid) to control the vocal source was developed. In the current study, LeTalker, a biophysical computational model of the vocal system was used as the physical plant. In the LeTalker, a three-mass vocal fold model was used to simulate self-sustained vocal fold oscillation. A constant/ǝ/vowel was used for the vocal tract shape. The trachea was modeled after MRI measurements. The neuromuscular control system generates control parameters to achieve four acoustic targets (fundamental frequency, sound pressure level, normalized spectral centroid, and signal-to-noise ratio) and four somatosensory targets (vocal fold length, and longitudinal fiber stress in the three vocal fold layers). The deep-learning-based control system comprises one acoustic feedforward controller and two feedback (acoustic and somatosensory) controllers. Fifty thousand steady speech signals were generated using the LeTalker for training the control system. The results demonstrated that the control system was able to generate the lung pressure and the three muscle activations such that the four acoustic and four somatosensory targets were reached with high accuracy. After training, the motor command corrections from the feedback controllers were minimal compared to the feedforward controller except for thyroarytenoid muscle activation.

Electrical Stimulation of Vocal Fold Adduction Triggered by Laryngeal Electromyography Using a Custom Implant.

Medialization procedures for unilateral vocal fold (VF) paralysis generally improve voice but do not fully replace dynamic VF adduction. Paralyzed VFs typically experience synkinetic reinnervation, which makes it feasible to elicit movement through electrical stimulation. We tested a novel laryngeal pacing implant capable of providing closed-loop (automatic) stimulation of a VF triggered by electromyography (EMG) potentials from the contralateral VF. A custom, battery-powered, microprocessor-based stimulator was tested in eight dogs with bipolar electrodes implanted for recording EMG from the left VF and stimulating adduction of the right VF. A cuff electrode on the left recurrent laryngeal nerve (RLN) stimulated unilateral VF adduction, modeling voluntary control in anesthetized animals. Closed-loop stimulation was tested in both acute and chronic experiments. Synkinetic reinnervation was created in two animals by right RLN transection and suture repair to model unilateral VF paralysis. In all animals, left VF activation through RLN stimulation generated a robust EMG response that rapidly triggered stimulation of contralateral thyroarytenoid and lateral cricoarytenoid muscles, causing nearly simultaneous bilateral adduction. Optimal triggering of VF stimulation from elicited EMG was achieved using independent onset and offset thresholds. Real-time artifact blanking allowed closed-loop stimulation without self-perpetuating feedback, despite the proximity of recording and stimulation electrodes. Using a custom implant system, we demonstrated real-time closed-loop stimulation of one VF triggered by the activation of the contralateral VF. This approach could potentially restore dynamic glottic closure for reflexive behaviors or phonation in cases of unilateral VF paralysis with synkinetic reinnervation. https://doi.org/10.23641/asha.24492133.

An Euler–Bernoulli-type beam model of the vocal folds for describing curved and incomplete glottal closure patterns

Incomplete glottal closure is a laryngeal configuration wherein the glottis is not fully obstructed prior to phonation. It has been linked to inefficient voice production and voice disorders. Various incomplete glottal closure patterns can arise and the mechanisms driving them are not well understood. In this work, we introduce an Euler–Bernoulli composite beam vocal fold (VF) model that produces qualitatively similar incomplete glottal closure patterns as those observed in experimental and high-fidelity numerical studies, thus offering insights into the potential underlying physical mechanisms. Refined physiological insights are pursued by incorporating the beam model into a VF posturing model that embeds the five intrinsic laryngeal muscles. Analysis of the combined model shows that co-activating the lateral cricoarytenoid (LCA) and interarytenoid (IA) muscles without activating the thyroarytenoid (TA) muscle results in a bowed (convex) VF geometry with closure at the posterior margin only; this is primarily attributed to the reactive moments at the anterior VF margin. This bowed pattern can also arise during VF compression (due to extrinsic laryngeal muscle activation for example), wherein the internal moment induced passively by the TA muscle tissue is the predominant mechanism. On the other hand, activating the TA muscle without incorporating other adductory muscles results in anterior and mid-membranous glottal closure, a concave VF geometry, and a posterior glottal opening driven by internal moments induced by TA muscle activation. In the case of initial full glottal closure, the posterior cricoarytenoid (PCA) muscle activation cancels the adductory effects of the LCA and IA muscles, resulting in a concave VF geometry and posterior glottal opening. Furthermore, certain maneuvers involving co-activation of all adductory muscles result in an hourglass glottal shape due to a reactive moment at the anterior VF margin and moderate internal moment induced by TA muscle activation. These findings have implications regarding potential laryngeal maneuvers in patients with voice disorders involving imbalances or excessive tension in the laryngeal muscles such as muscle tension dysphonia.

Ultrasound-guided injection into the lateral crico-arytenoid muscle: a pilot study

ObjectivesThe anterior, percutaneous Botulinum neurotoxin (BoNT) injection in the lateral cricoarytenoid muscle (LCA) guided by laryngeal electromyography (LEMG) is considered the golden standard treatment for several neurolaryngological disorders. The study presented in this article aims to assess the effectiveness of an alternative approach by which the injection is performed laterally under ultrasound monitoring.Study designAnatomical dissection study in human cadavers.SettingsAcademic health care center.MethodsUltrasound-guided bilateral dye (0.1 mL of dye solution containing cold-curing polymers, latex, acrylates, acrylic esters, alcohol, and green color) injection in the LCA was performed by means of 24G needles and 1 mL syringes using the lateral approach. The dye location and distribution were assessed by anatomic dissection, performed immediately after the injection.ResultsIn 9/10 specimens, the dye was exclusively detectable in the LCA. In 1/10 case (left side), the dye could not be delivered in the LCA because of unintended penetration of the thyroid cartilage by the needle during injection. Anatomic dissection confirmed that the dye spread neither into the thyroarytenoid (TA) nor the cricothyroid muscle (CT).ConclusionsThe anatomic dissection following lateral dye injection in the LCA under ultrasound guide confirmed the precision of this approach in delivery a substance exclusively in a pre-determined target. This feature makes this method an interesting addition or alternative to the standard LEMG-guided BoNT injection at least when the LCA is its target.Level of evidenceIII.

Temporal expression of Laminin-111 in the developing rat larynx

Laminin-111 is a basement membrane protein that participates in motor innervation and reinnervation. During axonal pathfinding, laminin-111 interacts with netrin-1 (NTN1) and changes its attractant growth cone properties into repulsion. While previous models of recurrent laryngeal nerve (RLN) transection show increased Laminin-111 and NTN1 production after injury, developmental expression in the larynx has not been defined. This study investigates the expression of laminin-111 in laryngeal muscles during primary laryngeal innervation of Sprague Dawley rats. Adult larynges and embryos were sectioned for immunohistochemistry with βIII-Tubulin, laminin subunit α-1 (LAMA1), NTN1, and α-bungarotoxin. Sections were processed for single-molecule inexpensive RNA fluorescence in situ hybridization analysis of LAMA1 mRNA. LAMA1 expression increased in all intrinsic laryngeal muscles, except the medial thyroarytenoid (MTA), at E20.5. At E20.5 there was increased expression in the lateral thyroarytenoid (LTA) and posterior cricoarytenoid (PCA) compared to the MTA. NTN1 upregulation was limited to the LTA and lateral cricoarytenoid (LCA) at E16.5 without any increase in the MTA or PCA. LAMA1 and NTN1 expression did not strictly follow expected patterns relative to the known timing of innervation and does not appear to be acting similarly to its role following RLN injury. These differences between developmental and post-injury innervation provide targets for investigations of therapeutics after nerve injury.

Gross Morphological and Histological Features of Larynx in Yankasa Sheep ‎‎(Ovis aries)‎

The present study, conducted on the larynx of five adult Yankasa sheep of local breed, aimed at exploring its basic anatomy and histological features. The larynx consists of four cartilages; the unpaired epiglottis rostroventral, unpaired thyroid ventrally, dorsal paired arytenoid, and caudal unpaired cricoid. These cartilages presented distinct morphological features and were connected to each other by ligaments. The intrinsic laryngeal muscles include; the dorsal cricoarytenoid and transverse arytenoid muscles. The lateral cricoarytenoid was concealed by the thyroid laminae. The ventrally located thyroarytenoid and cricothyroid muscles. The laryngeal cavity comprised of rostral vestibule, a narrow middle glottic cleft and a wide infraglottic cavity caudally. Histologically, the epiglottis was lined by stratified squamous keratinized epithelium, the thyroid cartilage was lined by pseudostratified columnar epithelium, whereas the arytenoid cartilage was lined by pseudostratified columnar ciliated epithelium with goblet cells. The loose irregular loose connective tissue of the propria submucosa comprised of connective tissue cells mainly fibroblast, and fine blood capillaries, whereas the deeper part presented glandular tissues, ducts, fat cells and cartilages. It is envisaged that the study has provided basic information on gross and histological feature of the larynx in the Yankasa sheep.

Phonation Threshold Pressure Revisited: Effects of Intrinsic Laryngeal Muscle Activation.

Phonation threshold pressure (Pth ) is the minimum subglottic pressure required to reach phonation onset and is considered a marker for vocal efficiency and health. We investigated the effects of intrinsic laryngeal muscle (ILM) activation on Pth . In vivo animal study. In an in vivo canine phonation model, laryngeal adductor muscles were activated together by stimulation of the recurrent laryngeal nerves (RLNs) and individually via stimulation of respective terminal nerve branches. Cricothyroid (CT) muscles were activated via stimulation of the superior laryngeal nerves. ILMs were activated in a graded manner at various combinations as transglottal airflow was gradually increased. Aerodynamic and glottal posture parameters were measured at phonation onset. Graded RLN stimulation decreased glottal distance and increased Pth . Thyroarytenoid (TA) muscle activation alone increased Pth . Lateral cricoarytenoid (LCA) muscle activation alone had minimal effects. However, graded TA activation as a function of LCA activation level revealed a synergistic relationship between the two muscles in increasing Pth . Effects of CT activation were dependent on adductor stimulation level: CT activation increased Pth at low RLN stimulation levels and decreased Pth at high RLN levels. The effects of ILM activation on Pth were consistent with their expected effects on vocal fold stiffness and tension. TA was the primary adductor controlling Pth . While LCA alone had minimal effects on Pth , it enhanced the role of TA in controlling Pth . TA and CT have antagonistic roles in controlling Pth . These relationships should be considered in clinical efforts to improve ease of phonation and vocal efficiency. NA, basic science Laryngoscope, 132:1427-1432, 2022.

Characteristics of Early Internal Laryngeal Muscle Atrophy After Recurrent Laryngeal Nerve Injuries in Rats.

The present study investigated the characteristics of early internal laryngeal muscle atrophy in recurrent laryngeal nerve injury (RLNI) rats. To observe the characteristics of early internal laryngeal muscle atrophy post RLNI. Rats were divided into three groups: sham-operated control group (n = 20), recurrent laryngeal nerve transverse injury group (RLNTI, n = 50), and recurrent laryngeal nerve blunt contusion group (RLNBC, n = 50). Five weeks after RLNI, certain rats were sacrificed weekly, and their laryngeal tissues were harvested. The atrophic features of internal laryngeal muscles were detected using hematoxylin and eosin. NF-κB and MuRF-1 levels were tested using IHC. The atrophic degree and fibrosis of thyroarytenoid, posterior cricoarytenoid, and lateral cricoarytenoid muscles were related to the type of RLNI. The average myofiber cross-sectional areas increased before an obvious decrease in the RLNTI and RLNBC groups. Muscle recovery occurred in the RLNBC group starting 4 weeks after RLNI, but only a weak trend was observed in the RLNTI group in the 5th week. During the muscle atrophy process, MuRF-1 and NF-κB were upregulated early and were maintained at a high level, which showed a trend similar to muscle atrophy. However, NF-κB expression was opposite to MuRF-1 expression and muscle atrophy when the muscles recovered. The atrophy degree of internal laryngeal muscles was associated with the type of RLNI. The NF-κB/MuRF-1 signaling pathway was involved in internal laryngeal muscle atrophy after RLNI, which is different from skeletal muscle after denervation. NA Laryngoscope, 131:E1256-E1264, 2021.

Ultrasonographic findings post laryngoplasty in the horse.

Laryngoplasty is commonly used to treat laryngeal hemiplegia in Thoroughbred racehorses. Evaluation of the success of the laryngoplasty is traditionally determined using endoscopy. Laryngeal ultrasonography and normal ultrasonographic appearance have been reported in the standing horse, but post-laryngoplasty and ventriculectomy ultrasonographic evaluation has limited literature coverage. A prospective case series of 10 Thoroughbred racehorses with left laryngeal hemiplegia was examined ultrasonographically and endoscopically prior to 3-10 days, 30-50 days, and 6-12 months after laryngoplasty and ventriculectomy. Anatomical structures and Plica vocalis movements were described and measurements and gradings analyzed by repeated means analysis of variance (P<.05). Postsurgical ultrasonographic visualization of Ventriculus laryngis entrances was possible. The distance between Plica vocalis in exhalation was significantly larger than that during inhalation (P<.05). Pre- and postsurgical caudal Basihyoideum and rostral Cartilago thyroidea depth was significantly different in some instances (P<.05). No significant differences in the Muscularis cricoarytenoideus lateralis measurements were found. Complications in the extra-luminal structures were found in seven horses including soft tissue swelling, seroma, and hematoma. A luminal Plica vocalis abscess and Plica vocalis granuloma were also detected ultrasonographically. Ultrasonography can be used to evaluate the post-laryngoplasty horse for assessing the success of the procedure, monitoring healing, and detecting complications.

Surgical histoanatomy for adduction arytenopexy using injection laryngoplasty.

In order to improve a large posterior glottal gap and/or aspiration, injections of augmentation substances should not only be administered at the mid-membranous vocal fold in the thyroarytenoid muscle, but also at the cartilaginous portion of the vocal fold to make adduction arytenopexy possible. Ten adult human larynges were investigated using the whole-organ serial section technique. Vertical thickness of the posterior aspect of the thyroarytenoid muscle was relatively thin (3.4 ± 0.4 mm), especially in females (3.2 ± 0.3 mm). Consequently, care should be taken to ensure the correct depth of needle placement. If the needle is placed too deep, augmentation substances are injected into the lateral cricoarytenoid muscle, located beneath the thyroarytenoid muscle, or into the paraglottic space, located inferolateral to the thyroarytenoid muscle. The injection location and the amount of injected material should be modified based on the pathological conditions of the voice disorder and aspiration.

Unearthing a consistent bilateral R1 component of the laryngeal adductor reflex in awake humans.

The laryngeal adductor reflex (LAR) is an essential tracheobronchial protective mechanism resulting in vocal fold adduction to laryngeal stimulation. It was thought to consist of an early ipsilateral R1 component and a later, bilateral but highly centrally modulated R2 component. We recently demonstrated that bilateral R1 responses are robustly present in humans under general anesthesia. We herein give evidence that the R1 response is also bilateral in awake humans and is likely the primary component responsible for initiating the LAR. Seven volunteers were included (3 males, 4 females). The reflex was elicited by direct percutaneous monopolar needle stimulation of the internal superior laryngeal nerve. Electromyography traces from bilateral lateral cricoarytenoid muscles were recorded using hookwire electrodes. Reflex responses to variations in stimulus intensity and duration were evaluated. Bilateral R1 responses were recorded in all patients, even during deep inspiration when the vocal folds were maximally abducted. R1, but not R2, responses increased linearly in amplitude, with sequential increases in both stimulation intensity (1-8 mA) and duration (100-500 µsec) (Pearson correlation 0.94). Contradicting over 40 years of research, we demonstrate that the R1 LAR component is consistently bilateral in awake humans. It increases linearly with stimulus intensity and is unaffected by conscious state suggesting minimal central control. These findings may provide a means to objectively stratify patients for risk of laryngeal aspiration, even in unconscious states, and its potentially cardinal role in disease states such as laryngospasm and sudden infant death needs to be reevaluated. 4. Laryngoscope, 2581-2587, 2018.

F95. Laryngeal electromyography in patients with Amiotrophic Lateral Sclerosis (ALS): Preliminary results

Introduction Amyotrophic Lateral Sclerosis (ALS) is the most relevant motor neuron disease in adults and characterized by widespread weakness. Despite frequent bulbar involvement, little is known about clinical and electrophysiological changes in the larynx in patients with ALS. The objective of this study was to evaluate the frequency and pattern of involvement of laryngeal muscles in ALS and its functional relevance. In addition, we assessed whether laryngeal EMG (LEMG) would increase the diagnostic sensitivity for ALS. Methods Fourteen ALS patients, 13 with spinal onset and 1 with bulbar onset, underwent nasofibroscopy (NF) followed by LEMG, in which a concentric needle was used to evaluate the thyroid-arytenoid (TA), lateral crico-arytenoid (CAL), posterior crico-arytenoid (CAP) and crico-thyroid (CT) muscles, at rest and during activation. After LEMG, resting and activation of the genioglossus and masseter muscles were also studied using the same concentric needle. Results The mean age of the patients was 48.5 years and there were 6 women. The procedures were fast (30 min on average) and uneventful. Thirteen patients presented neurogenic changes in at least one laryngeal muscle. A single patient had entirely normal LEMG. We found a pattern compatible with chronic denervation (MUAPs remodeling and incomplete recruitment) with the following frequency: TA muscle in 11/14 patients (78.5%); CT in 10/14 patients (71.4%); CAP in 10/14 patients (71.4%) and CAL in 7/14 patients (50%). In 8 patients, there were fibrillations and/ or fasciculations associated with chronic neurogenic changes in the same muscle; of these, 4 had no alteration in the genioglossus muscle and 2 had only chronic alterations in the same muscle. NF revealed motor abnormalities in the larynx in 9 patients; in the remaining 5, NF was normal but LEMG identified signs of denervation in 4 of them. Conclusion LEMG is able to identify laryngeal denervation in patients with ALS. This procedure may increase diagnostic sensitivity for ALS by identifying bulbar involvement in patients without tongue denervation. Changes in LEMG may precede clinical involvement of the larynx in these patients.

S124. Comprehensive tube-based methodology for evaluating the brainstem laryngeal adductor reflex in humans under anesthesia

The laryngeal adductor reflex (LAR) is a vago-vagal reflex necessary for airway protection that is organized by the brainstem. It consists of an early R1 and late R2 responses that prevent aspiration by causing thyroarytenoid and lateral cricoarytenoid muscles contraction and thus vocal fold closure. The afferent sensation from the glottis and supraglottis mucosa travels through the internal branch of the superior laryngeal nerve (a branch of the vagus nerve) to the nucleus of the solitary tract. The motor neurons contributing to the efferent arc, through the vagus nerve, lie in the nucleus ambiguous. Bilateral simultaneous adduction of both vocal folds is a mandatory condition for achieving an effective protective function of the lower airway. LAR impairment leads to increased risk of aspiration what is highly correlated with increased morbidity and mortality. The LAR was elicited by electrical stimulation of the laryngeal mucosa on the side contralateral to the operative field using the electrodes attached to the endotracheal tube (EET). A single stimulus at intensity up to 15 mA applied. Surface electrodes ipsilateral to the operative field attached to the EET were used to record the contralateral R1 (cR1) and R2(cR2) responses of the LAR. One hundred patients (134 nerves at risk), aged between 21 and 84 years, who underwent thyroid surgeries (19 males, 81 females) were included. Before the surgical procedure started cR1 and cR2 responses were reliably elicited in 100% and 67% of the patients, respectively. Mean cR1 latencies ± standard deviation were 21.6 ± 3 ms (left) and 21.8 ± 2.8 ms (right). Mean cR1 amplitudes were 312.9 ± 178.2 μV (left) and 314 ± 183.7 μV (right). During surgery, monitorability of the LAR decreased to 84% due to methodological limitations. The LAR is a comprehensive tube-based methodology for evaluating the integrity of vagus nerve and brainstem LAR pathway. Advantages over current monitoring techniques including simplicity, ability to continuously monitor neural function without placement of additional neural probes and ability to assess the integrity of both sensory and motor pathways. The LAR has the potential to revolutionize how the vagus nerve is continuously monitored during neck neurosurgical procedures.

Botulinum Toxin Injections Into the Lateral Cricoarytenoid Muscles for Vocal Process Granuloma

Contact granulomas are benign, exophytic inflammatory lesions of the larynx that typically arise on or near the vocal process of the arytenoid cartilage. The most common management options include voice therapy and antireflux pharmacotherapy, intralesional steroid injections, botulinum toxin injections, and surgical excision. In-office Botox injection into the lateral cricoarytenoid (LCA) muscle can be effective even for recurrent granulomas. This is a retrospective chart review and literature review. We reviewed more than 400 charts and included two patients, who underwent in-office injection with botulinum toxin A into LCA muscles bilaterally, after previously failing both conservative and surgical management. Both cases showed significant improvement of the laryngeal granulomas after 6 months and a single botulinum toxin injection. Both cases were initially grade III granuloma that improved to grade I. In-office injection of botulinum toxin A targeting the LCA muscle appears to be a safe and effective treatment modality in refractory laryngeal granuloma.

Quantitative Evaluation of the In Vivo Vocal Fold Medial Surface Shape

Glottal insufficiency is a common clinical problem in otolaryngology and medialization laryngoplasty (ML) procedures remain the primary treatment modality. Although the goal of ML is to restore physiologic glottal posture and achieve optimal phonation, this posture has not been directly measured. In this study, we assessed glottal medial surface contour changes with selective activation of the intrinsic laryngeal muscles (ILMs). Basic science study using an in vivo canine hemilarynx model. In an in vivo canine hemilarynx, India ink was used to mark fleshpoints in a grid-like fashion along the medial surface of the vocal fold and ILMs were activated in a graded manner. A right-angled prism provided two views of the medial surface, which were recorded using a high-speed camera and used to reconstruct the 3D posture deformations of the medial surface. Thyroarytenoid (TA) muscle activation results in initial inferomedial bulging and increased glottal channel thickness and then glottal adduction with a final rectangular glottal channel shape. Lateral cricoarytenoid (LCA) activation closes the posterior glottis but final posture remains slightly convergent. Together, TA + LCA forms a rectangular glottis with an increased glottal vertical thickness. Posterior cricoarytenoid activation results in abduction and a slightly divergent glottis, whereas cricothyroid activation elongates the glottis and reduces the glottal channel vertical thickness. A quantitative analysis of in vivo canine vocal fold medial surface upon activation of selective ILMs is provided. This may guide our therapeutic efforts during medialization laryngoplasty, as well as computational modeling of laryngeal physiology.

An empirical model linking intrinsic laryngeal muscle activation to vocal fold geometry and stiffness

Although vocal fold vibration and the resulting voice production depend on the geometry and mechanical properties of the vocal folds, control of voice is achieved through laryngeal muscle activation, which postures the vocal folds into desired geometry and mechanical properties. Such posturing process is known to cause simultaneous changes in vocal fold position, geometry, stiffness, and tension, which has been hypothesized to be a possible origin of vocal registers. Understanding such co-variations in vocal fold geometry and mechanical properties is thus critical to our understanding of human voice production and control, and the development of muscularly controlled, computationally efficient models of phonation. In this study, an empirical model is developed to link the glottal gap, vocal fold length, vocal fold vertical thickness, and the mechanical properties of the vocal fold to the activation levels of the cricothyroid, thyroarytenoid, lateral cricoarytenoid, interarytenoid, and posterior cricoarytenoid muscles, based on data from in vivo larynx experiments. Combined with a continuum model of phonation, this model is used to investigate muscular control of pitch and vocal registers and the preliminary results are discussed.

Lateral Cricoarytenoid Release: Development of a Novel Surgical Treatment Option for Adductor Spasmodic Dysphonia in a Canine Laryngeal Model.

To investigate the efficacy of a novel adductor muscle-releasing technique designed to decrease the force of vocal fold adduction, as a potential surgical therapy for patients with adductor spasmodic dysphonia (ADSD). Experimental animal study. A canine laryngeal model was used to assess the acute and sustained efficacy of a lateral cricoarytenoid (LCA) muscle release. A total of 34 canine hemilaryngeal preparations were divided among 7 experimental groups. The LCA muscle was separated from its cricoid cartilage origin via an open, anterior, submucosal approach. The laryngeal adductory pressures (LAP) were assessed pre- and post-muscle release via direct recurrent laryngeal nerve stimulation. Measurements were repeated at 1.5, 3, or 6 months postoperatively. Another study evaluated release of the thyroarytenoid (TA) muscle from its thyroid cartilage origin. Releasing the LCA muscle demonstrated a significant decrease in LAP acutely and was maintained at all 3 time points with the aid of a barrier (P < .05). Without the barrier, the LCA muscle reattached to the cricoid. Acute release of the TA muscle did not significantly decrease the LAP. The proposed LCA release procedure may provide patients with a permanent treatment option for ADSD. However, longer-term studies and human trials are needed.

Three-dimensional posture changes of the vocal fold from paired intrinsic laryngeal muscles.

Although the geometry of the vocal fold medial surface affects voice quality and is critical in the treatment of glottic insufficiency, the prephonatory shape of the vocal fold medial surface is not well understood. In this study, we activated intrinsic laryngeal muscles individually and in combinations, and recorded the temporal sequence and precise three-dimensional configurational changes of the vocal fold medial surface. In vivo canine hemilarynx model. A hemilaryngectomy was performed in an in vivo canine model and ink was used to mark the medial surface of the in situ vocal fold in a grid-like fashion. The thyroarytenoid (TA), lateral cricoarytenoid (LCA), cricothyroid (CT), and posterior cricoarytenoid (PCA) muscles were stimulated individually and in combinations. A right-angle prism whose hypotenuse formed the glottal midline provided two distinct views of the medial surface for a high-speed digital camera. Image-processing package DaVis (LaVision Inc., Goettingen, Germany) allowed time series cross-correlation analysis for three-dimensional deformation calculations of the vocal fold medial surface. Combined TA and LCA activation yields an evenly adducted rectangular glottal surface. Addition of thyroarytenoid to cricoarytenoid adducts the vocal fold from inferior to superior in a graded fashion allowing formation of a divergent glottis. Posterior cricoarytenoid has a bimodal relationship with thyroarytenoid favoring abduction. Cricothyroid and lateral cricoarytenoid yield unique glottal postures necessary but likely not conducive for efficient phonation. Understanding the three-dimensional geometry of the vocal fold medial surface will help us better understand the cause-effect relationship between laryngeal physiology and phonation. NA Laryngoscope, 127:656-664, 2017.

Surgical approach to the thyroarytenoid branch of the inferior laryngeal nerve through the thyroid cartilage.

To describe the anatomical course of the intralaryngeal portion of the inferior laryngeal nerve (ILN) and to standardize the surgical access to its thyroarytenoid branch (TAb) through the thyroid cartilage. Under surgical microscopy, 33 adult human excised larynges were dissected, to expose the intralaryngeal portion of ILN. The point of entry of TAb, ILN's terminal branch, in the thyroarytenoid (TA) muscle was determined and correlated with thyroid cartilage dimensions. After entering the larynx, the ILN consistently traveled between the thyroid cartilage and the lateral cricoarytenoid muscle in an anterior and slightly cranial course. The distance from the point of entry of the TAb in the TA muscle to the midline (TAb-H) and to the inferior border (TAb-V) of the thyroid cartilage differed according to gender. In females, mean distances of TAb-H and TAb-V were 20.5mm and 5.2mm and in males, 22.3mm and 5.9mm, respectively. The intralaryngeal course of the inferior laryngeal nerve presents low variability and measures from landmarks in the thyroid cartilage help to estimate the point of entry of thyroarytenoid branch in thyroarytenoid muscle.

Botulinum Toxin A for Treatment of Contact Granuloma

Contact granuloma has been associated with voice abuse, laryngopharyngeal reflux, and habitual throat clearing. It has a high propensity for persistence and recurrence. Treatment options included voice therapy and antireflux measures. Surgical excision has been considered in patients who do not respond to medical management. In this research, we aimed to present our experience with botulinum toxin injection only. Retrospective case series of a tertiary referral center. Our series consisted of 22 patients, who underwent botulinum toxin injection only as an office procedure to bilateral thyroarytenoid and lateral cricoarytenoid muscles in 2 × 1.25 to 2×2.5 U. No other treatment was applied. The cases were followed up for at least 6months ranging between 6 and 100months with a mean of28. Seventeen cases (77%) were cured of their granuloma. Eleven of the cured cases had grade 2, four cases had grade 1, and two patients had grade 3 granuloma. Botulinum toxin A injection only is an efficient treatment modality in contact granuloma, especially for grade 1, 2, and 3 cases, and it can be used as a first-line treatment.