Generation, Coordination, and Evolution of Neural Circuits for Vocal Communication.

In many species, vocal communication is essential for coordinating social behaviors including courtship, mating, parenting, rivalry, and alarm signaling. Effective communication requires accurate production, detection, and classification of signals, as well as selection of socially appropriate responses. Understanding how signals are generated and how acoustic signals are perceived is key to understanding the neurobiology of social behaviors. Here we review our long-standing research program focused on Xenopus, a frog genus which has provided valuable insights into the mechanisms and evolution of vertebrate social behaviors. In Xenopus laevis, vocal signals differ between the sexes, through development, and across the genus, reflecting evolutionary divergence in sensory and motor circuits that can be interrogated mechanistically. Using two ex vivo preparations, the isolated brain and vocal organ, we have identified essential components of the vocal production system: the sexually differentiated larynx at the periphery, and the hindbrain vocal central pattern generator (CPG) centrally, that produce sex- and species-characteristic sound pulse frequencies and temporal patterns, respectively. Within the hindbrain, we have described how intrinsic membrane properties of neurons in the vocal CPG generate species-specific vocal patterns, how vocal nuclei are connected to generate vocal patterns, as well as the roles of neurotransmitters and neuromodulators in activating the circuit. For sensorimotor integration, we identified a key forebrain node that links auditory and vocal production circuits to match socially appropriate vocal responses to acoustic features of male and female calls. The availability of a well supported phylogeny as well as reference genomes from several species now support analysis of the genetic architecture and the evolutionary divergence of neural circuits for vocal communication. Xenopus thus provides a vertebrate model in which to study vocal communication at many levels, from physiology, to behavior, and from development to evolution. As one of the most comprehensively studied phylogenetic groups within vertebrate vocal communication systems, Xenopus provides insights that can inform social communication across phyla.

Ex vivo investigation of the effect of the transverse arytenoid ligament on abduction of the arytenoid cartilage when performing equine laryngoplasty.

Aims: To investigate the effect of the transverse arytenoid ligament (TAL) on abduction of the arytenoid cartilage when performing laryngoplasty. Methods: Modified prosthetic laryngoplasty was performed on right and left sides of 13 cadaver larynges. Increasing force was sequentially applied to the left arytenoid cartilage at 3 N intervals from 0-24 N, when the force on the right arytenoid cartilage was either 0 or 24 N, before and after TAL transection. Digital photographs of the rostral aspect of the larynx were used to determine the left arytenoid abduction angles for these given force combinations and results compared before and after TAL transection. Longitudinal and transverse sections of the TAL from seven other equine larynges were also examined histologically. Results: Increasing force on the left arytenoid cartilage from 0-24 N produced a progressive increase in the angle of the left arytenoid cartilage (p < 0.001) and increasing force on the right arytenoid cartilage from 0-24 N reduced the angle of the left arytenoid cartilage (p < 0.001). Following transection of the TAL the mean angle of the left arytenoid increased from 36.7 (95% CI = 30.5-42.8)° to 38.4 (95% CI = 32.3-44.5)°. Histological examination showed that the TAL was not a discrete ligament between the arytenoid cartilages but was formed by the convergence of the ligament and the left and right arytenoideus transversus muscles. Conclusions: Transection of the TAL in ex vivo equine larynges enabled greater abduction of the left arytenoid cartilage for a given force. These results indicate that TAL transection in conjunction with prosthetic laryngoplasty may have value, but the efficacy and safety of TAL transection under load in vivo, and in horses clinically affected with recurrent laryngeal neuropathy must be evaluated. Abbreviations: Fmax: Force needed to maximally abduct the left or right arytenoid; TAL: Transverse arytenoid ligament.

A Novel Lateral Approach to the Assessment of Vocal Cord Movement by Ultrasonography.

BACKGROUND: Ultrasonography is a non-invasive technique that is commonly used by endocrinologists and endocrine surgeons to examine the thyroid region and could be useful for the assessment of vocal cord movement by these specialists. However, previous studies reported a low rate of successful visualization of vocal cord movement by ultrasonography. To address this issue, we devised a novel ultrasonographic procedure for assessing vocal cord movement indirectly by observing the arytenoid movement from a lateral view. METHODS: Subjects were 188 individuals, including 23 patients with vocal cord paralysis and 13 with vocal cord paresis. We performed ultrasonographic assessment of vocal cord movement using two different procedures: the conventional middle transverse procedure and the novel lateral vertical procedure. RESULTS: The rate of visualization of vocal cords with the middle transverse procedure was 70.2% and that of the arytenoid cartilage with the lateral vertical procedure was 98.4%. The lateral vertical procedure enabled visualization of all patients with vocal cord paresis/paralysis and detected all 23 patients with vocal paralysis; only one of 13 patients with vocal cord paresis was positively identified. The conventional procedure enabled visualization of 21 of 36 patients with vocal cord paresis/paralysis with high accuracy. There was no false-positive case in either procedure. CONCLUSION: The proposed lateral vertical procedure improved the rate of visualization of vocal cord movement by ultrasonography, suggesting that it is a useful technique to screen for vocal cord paralysis by ultrasonography.

Effects of alfaxalone, thiopental, or propofol and diazepam on laryngeal motion in healthy dogs.

Laryngeal function is assessed by direct visualization of the larynx under a light plane of anesthesia. This study compared the effects of 3 anesthetic protocols on arytenoid motion in healthy dogs. Eight dogs were randomly assigned to receive alfaxalone, propofol and diazepam, or thiopental. Videolaryngoscopy was performed and still images at maximum inspiration and expiration were used to measure the area and height of the glottal gap. The normalized glottal gap area (NGGA = area in pixels/height2) was calculated. The NGAA change was defined as the difference between NGAA during inspiration and exhalation. Data were analyzed using Mann-Whitney and Kruskal-Wallis tests, P-values < 0.05 were considered statistically significant. No significant difference among induction protocols was found when comparing NGGA change after induction or before recovery. Alfaxalone and propofol/diazepam are useful for evaluation of laryngeal function when administered to effect and a light plane of anesthesia is maintained.

Effets de l'alfaxalone, du thiopental ou du propofol et du diazépam sur le mouvement du larynx chez des chiens en santé. La fonction du larynx est évaluée par visualisation directe du larynx sous une légère anesthésie. Cette étude a comparé les effets de trois protocoles anesthésiques sur le mouvement aryténoïde chez des chiens en santé. Huit chiens ont été assignés au hasard pour recevoir de l'alfaxalone, du propofol et du diazépam ou du thiopental. Une vidéo-laryngoscopie a été réalisée et des images fixes à l'inspiration et à l'expiration maximales ont été utilisées pour mesurer la région et la hauteur de l'écart glottal. La région normalisée de l'écart glottal (RNEG = région en pixels/hauteur2) a été calculée. Le changement RNEG a été défini comme la différence entre le RNEG durant l'inspiration et l'expiration. Les données ont été analysées en utilisant les tests de Mann-Whitney et Kruskal-Wallis, les valeurs-P < 0,05 étaient considérées comme étant significatives sur le plan statistique. Aucune différence significative n'a été trouvée parmi les protocoles d'induction lors de la comparaison du changement RNEG après l'induction ou le réveil. L'alfaxalone et le propofol/diazépam sont utiles pour l'évaluation de la fonction du larynx lorsqu'ils sont administrés jusqu'à l'effet et qu'une légère anesthésie est maintenue.(Traduit par Isabelle Vallières).

Effects of thiopentone, propofol and alfaxalone on laryngeal motion during oral laryngoscopy in healthy dogs.

OBJECTIVE: To compare the effects of thiopentone, propofol and alfaxalone on arytenoid cartilage motion and establish the dose rates to achieve a consistent oral laryngoscopy examination. STUDY DESIGN: Randomised crossover study. ANIMALS: Six healthy adult Beagle dogs. METHODS: Each dog was randomly administered three induction agents with a 1-week washout period between treatments. Thiopentone (7.5 mg kg-1), propofol (3 mg kg-1) or alfaxalone (1.5 mg kg-1) was administered over 1 minute for induction of anaesthesia. If the dog was deemed inadequately anaesthetised, then supplemental boluses of 1.8, 0.75 and 0.4 mg kg-1 were administered, respectively. Continual examination of the larynx, using a laryngoscope, commenced once an adequate anaesthetic depth was reached until examination end point. The number of arytenoid motions and vital breaths were counted during three time periods and compared over time and among treatments. Data were analysed using Friedman and Mann-Whitney U tests, Spearman rho and a linear mixed model with post hoc pairwise comparison with Tukey correction. RESULTS: The median (range) induction and examination times were 2.8 (2.0-3.0), 2.7 (2.0-3.3) and 2.5 (1.7-3.3) minutes (p = 0.727); and 14.1 (8.0-41.8), 5.4 (3.3-14.8) and 8.5 (3.8-31.6) minutes (p = 0.016) for thiopentone, propofol and alfaxalone, respectively. The median dose rates required to achieve an adequate anaesthetic depth were 6.3 (6.0-6.6), 2.4 (2.4-2.4) and 1.2 (1.2-1.2) mg kg-1 minute-1, respectively. There was no significant difference for the total number of arytenoid motions (p = 0.662) or vital breaths (p = 0.789) among induction agents. CONCLUSION AND CLINICAL RELEVANCE: The number of arytenoid motions were similar among the induction agents. However, at the dose rates used in this study, propofol provided adequate conditions for evaluation of the larynx with a shorter examination time which may be advantageous during laryngoscopy in dogs.

Vocal Fry and Vowel Height in Simulated Room Acoustics.

PURPOSE: The purpose of this study was to investigate the influence of room acoustics in the relationship between vowel height and vocal fry. METHODS: This was a cross-sectional study. Participants (college students, n = 40) read the first six sentences of "The Rainbow Passage" under nine simulated room acoustic conditions. Using two words with low vowels (act, pot) and two words with high vowels (shape, strikes) preceding a voiceless stop, the presence/absence of vocal fry was assessed using an automatic detection script. Generalized estimation equations were used to investigate the relationship between percentage of vocal fry, vowel height, and room acoustics. RESULTS: The percentage of vocal fry was significantly higher for the low-height vowels compared with the high-height vowels (ß = 1.21; standard er ror = 0.35), and for pink background noise present (ß = 0.89; standard error = 0.35) compared with the condition without artificial noise added. CONCLUSION: The results of this study indicate that young college students are more likely to produce fry phonation when producing low-height vowels under pink background noise condition compared with no noise conditions and high-height vowels. This result is of special interest for voice clinicians when designing therapy plans and vocal assessment protocols with fry-like components.

Interaction between the thyroarytenoid and lateral cricoarytenoid muscles in the control of vocal fold adduction and eigenfrequencies.

Although it is known vocal fold adduction is achieved through laryngeal muscle activation, it is still unclear how interaction between individual laryngeal muscle activations affects vocal fold adduction and vocal fold stiffness, both of which are important factors determining vocal fold vibration and the resulting voice quality. In this study, a three-dimensional (3D) finite element model was developed to investigate vocal fold adduction and changes in vocal fold eigenfrequencies due to the interaction between the lateral cricoarytenoid (LCA) and thyroarytenoid (TA) muscles. The results showed that LCA contraction led to a medial and downward rocking motion of the arytenoid cartilage in the coronal plane about the long axis of the cricoid cartilage facet, which adducted the posterior portion of the glottis but had little influence on vocal fold eigenfrequencies. In contrast, TA activation caused a medial rotation of the vocal folds toward the glottal midline, resulting in adduction of the anterior portion of the glottis and significant increase in vocal fold eigenfrequencies. This vocal fold-stiffening effect of TA activation also reduced the posterior adductory effect of LCA activation. The implications of the results for phonation control are discussed.

Long-term maintenance of arytenoid cartilage abduction and stability during exercise after laryngoplasty in 33 horses.

OBJECTIVES: To (1) assess long-term maintenance of arytenoid cartilage abduction (ACA) after laryngoplasty (LP); and (2) correlate the residual grade of ACA and postoperative abductory loss with arytenoid cartilage stability (ACS) during exercise. STUDY DESIGN: Case series. ANIMALS: Horses re-examined after laryngoplasty (n = 33). METHODS: Of 89 LP horses (2005-2010), 33 had historic ACA data available and upper airway endoscopy at rest and during over-ground exercise (mean, 33 months; range, 4-71 months) after surgery. ACA grade at 1 and 6 weeks postoperatively were correlated to long-term ACA grade. Effects of long-term ACA grade and magnitude of postoperative abductory loss on ACS during exercise were investigated. RESULTS: Median ACA grade at 1 week (n = 33) was 2, reducing to grade 3 by week 6 (n = 16). Grade 3 abduction was maintained in the long-term. Correlation between ACA at 1 week and the long-term was poor (ρ = .43, P = .1), but there was good correlation between week 6 and long-term (ρ = .89, P < .001). Arytenoid cartilage instability was observed during exercise in 7/33 of horses, and not significantly associated with the ACA grade (P = .50), or the number of grades of ACA lost (P = .64). CONCLUSIONS: Limited abductory loss occurs after 6 weeks postoperatively. Resting ACA grade was not a useful predictor of ACS during exercise.

Effect of three anesthetic induction protocols on laryngeal motion during laryngoscopy in normal cats.

OBJECTIVES: To objectively measure and subjectively score the effect of 3 anesthetic induction protocols on arytenoid cartilage motion in normal cats. STUDY DESIGN: Randomized prospective clinical study. ANIMALS: Cats (n = 35) without previous history of respiratory dysfunction. METHODS: Cats were randomly assigned to administration of alfaxalone, propofol, or midazolam and ketamine to induce anesthesia after premedication with methadone. Videolaryngoscopy was performed. Still images at maximum inspiration and expiration were used to measure the area and height of the rima glottidis. Change in rima glottidis area and of normalized glottal gap area (NGGA = area/height(2) ) was calculated. Subjective scores for arytenoid movement were obtained. Kruskal-Wallis test was performed on change of NGGA and rima glottidis area. RESULTS: No statistically significant difference was found between groups for age, sex, body weight, and body condition score. Percentage increase of rima glottidis area and change in NGGA were similar for all groups (P = .33 and P = .29). No significant differences were found for subjective scores between groups (P = .54). Arytenoid movement was not detected during videolaryngoscopy and subjective scoring in 3 cats anesthetized with propofol and in 3 cats anesthetized with midazolam and ketamine, despite presence of respiratory movements. CONCLUSIONS: No difference in laryngeal motion was observed between the 3 protocols used to induce anesthesia in cats premedicated with methadone.

Observation of arytenoid movement during laryngeal elevation using videoendoscopic evaluation of swallowing.

The purpose of this study was to confirm that the arytenoid regions dynamically adduct and extend upward toward the epiglottis during laryngeal elevation. While 14 healthy volunteers aged 19-32 years old swallowed 5 ml of white soft yogurt in one gulp without chewing, the movement of the arytenoid regions was observed for videoendoscopic evaluation of swallowing (VE). Each moving image was stored simultaneously on videotape. A cross-sectional area surrounded by the epiglottis and the bilateral arytenoid regions (S) and the length of a straight line passing through the anterior borders of the left and right arytenoid regions (L) were measured. The relative area of the entrance in the laryngeal vestibule was calculated as [S/L (2)] before the swallowing reflex (resting condition), just before laryngeal closure, and just after laryngeal closure. [S/L (2)] was smaller just before epiglottal descent than at the resting condition, and became smallest just after the epiglottis started to ascend. The mean area narrowed to 37.9% of the resting area just after laryngeal closure and in the most extreme case to 8.7% of the resting area. It was demonstrated that the arytenoid regions adducted and extended up toward the epiglottis during laryngeal elevation. The technique used to measure the cross-sectional area of the entrance in the laryngeal vestibule employing VE was an effective analytical procedure.

Endoscopic evaluation of arytenoid function and epiglottic structure in Thoroughbred yearlings and association with racing performance at two to four years of age: 2,954 cases (1998-2001).

OBJECTIVE-To determine the association between results of endoscopic evaluation of arytenoid function (AF) and epiglottic structure (ES) in Thoroughbred yearlings and racing performance at 2 to 4 years of age. DESIGN-Retrospective case series. ANIMALS-2,954 Thoroughbred yearlings. Procedures-Records of yearlings that had endoscopic evaluation of the larynx between 1998 and 2001 were obtained, and results were graded by use of standardized scales. A modified Havemeyer scale (grade I, II.1, II.2, III, or IV) was used to evaluate AF; ES was graded on a scale of 0 to IV. Records were annotated if the epiglottis was subjectively short or narrow. Racing performance data were obtained from an online database. RESULTS-Horses with grade II.2 AF had significantly less earnings at 4 years of age, compared with earnings of horses with AF grades < II.2. Grade III AF was associated with fewer starts and less earnings at 3 and 4 years of age. No horses met the criteria for grade IV AF. Horses with ES grades > II had less earnings at 2 and 4 years of age, compared with earnings of horses with ES grades < II. A short epiglottis was associated with less earnings at 2 and 3 years of age. CONCLUSIONS AND CLINICAL RELEVANCE-Analysis suggested that yearlings with grade III AF had a decrease in athletic potential. Yearlings with grade II.2 AF, an ES grade > II, or a short epiglottis typically had decreases in racing performance. These factors should be evaluated carefully when developing purchase recommendations.

[Laryngeal function as node metastasis predictor in patients with cancer of the larynx]. / Funcionalidad laríngea como predictora de metástasis ganglionares en pacientes con cáncer de laringe.

INTRODUCTION: Although the possibility of developing cervical node metastases (CNM) in patients with squamous cell carcinoma of the larynx (SCCL) depends on the site of tumor origin, other factors may be associated, even in glottic tumors. The objective of this study was to determine factors associated with CNM. METHODS: We carried out a retrospective analysis of a series of patients with SCCL. We analyzed the following variables: T-staging, tumor site, and arytenoid-mobility/fixation. and correlated them with histopathological node status. Statistical significance was assessed using chi2 tests. RESULTS: 91 patients were included 82 were male and 9 female; median age was 66 years. The most frequently affected site was the glottic-subglottic region (38) followed by the glottis (22). The most frequent T stage was T3 (46%) followed by T4 (25%); 81% were NO and 19% N+. 76 (83%) had arytenoid fixation. Factors associated with CNM included glottic-supraglottic infiltration (65%) and arytenoid fixation (17% vs. 0, p = 0.048). None of the patients with arytenoid mobility had CNM. Tumor infiltration to thyroid gland was observed among 14% of patients studied The most important risk factor was subglottic extension (17%; p = 0.5). CONCLUSIONS: Lack of mobility of the arytenoid cartilage is a factor associated with CNM among SCCL patients. A subglottic tumor is a risk factor for thyroid infiltration

Spatial Motion of Arytenoid Cartilage Using Dynamic Computed Tomography Combined with Euler Angles.

OBJECTIVE: To investigate the feasibility of dynamic computed tomography in recording and describing the spatial motion characteristics of the arytenoid cartilage. METHODS: Dynamic computed tomography recorded the real-time motion trajectory of the arytenoid cartilage during inspiration and phonation. A stationary coordinate system was established with the cricoid cartilage as a reference and a motion coordinate system was established using the movement of the arytenoid cartilage. The Euler angles of the arytenoid cartilage movement were calculated by transformation of the two coordinate systems, and the spatial motion characteristics of the arytenoid cartilage were quantitatively studied. RESULTS: Displacement of the cricoid cartilage was primarily inferior during inspiration. During phonation, the displacement was mainly superior. When the glottis closed, the superior displacement was about 5-8 mm within 0.56 s. During inspiration, the arytenoid cartilage was displaced superiorly approximately 1-2 mm each 0.56 s. The rotation angle was subtle with slight rotation around the XYZ axis, with a range of 5-10 degrees. During phonation, the displacement of the arytenoid cartilage was mainly inferior (about 4-6 mm), anterior (about 2-4 mm) and medial (about 1-2 mm). The motion of the arytenoid cartilage mainly consisted of medial rolling, and there was an alternating movement of anterior-posterior tilting. The arytenoid cartilage rolled medially (about 20-40 degrees within 0.56 s), accompanied by anterior-posterior tilting (about 15-20 degrees within 0.56 s). CONCLUSION: Dynamic computed tomography recordings of arytenoid cartilage movement can be combined with Euler transformations as a tool to study the spatial characteristics of laryngeal structures during phonation. LEVEL OF EVIDENCE: 4 Laryngoscope, 130:E646-E653, 2020.

Investigation of four distinct glottal configurations in classical singing--a pilot study.

This study investigates four qualities of singing voice in a classically trained baritone: "naive falsetto," "countertenor falsetto," "lyrical chest" and "full chest." Laryngeal configuration and vocal fold behavior in these qualities were studied using laryngeal videostroboscopy, videokymography, electroglottography, and sound spectrography. The data suggest that the four voice qualities were produced by independently manipulating mainly two laryngeal parameters: (1) the adduction of the arytenoid cartilages and (2) the thickening of the vocal folds. An independent control of the posterior adductory muscles versus the vocalis muscle is considered to be the physiological basis for achieving these singing voice qualities.

Implications of different degrees of arytenoid cartilage abduction on equine upper airway characteristics.

REASON FOR PERFORMING STUDY: The necessary degree of arytenoid cartilage abduction (ACA) to restore airway patency at maximal exercise has not been determined. OBJECTIVES: Use computational fluid dynamics modelling to measure the effects of different degrees of ACA on upper airway characteristics of horses during exercise. HYPOTHESIS: Maximal ACA by laryngoplasty is necessary to restore normal peak airflow and pressure in Thoroughbred racehorses with laryngeal hemiplegia. METHODS: The upper airway was modeled with the left arytenoid in 3 different positions: maximal abduction; 88% cross-sectional area of the rima glottis; and 75% cross-sectional area of the rima glottis. The right arytenoid cartilage was maximally abducted. Two models were assumed: Model 1: no compensation of airway pressures; and Model 2: airway pressure compensation occurs to maintain peak airflow. The cross-sectional pressure and velocity distributions for turbulent flow were studied at peak flow and at different positions along the airway. RESULTS: Model 1: In the absence of a change in driving pressure, 12 and 25% reductions in cross-sectional area of the larynx resulted in 4.11 and 5.65% reductions in peak airflow and 3.68 and 5.64% in tidal volume, respectively, with mild changes in wall pressure. Model 2: To maintain peak flow, a 6.27% increase in driving tracheal pressure was required to compensate for a cross-sectional reduction of 12% and a 13.63% increase in driving tracheal pressure was needed for a cross-sectional area reduction of 25%. This increase in negative driving pressure resulted in regions with low intraluminal and wall pressures, depending on the degree of airway diameter reduction. CONCLUSION: Assuming no increase in driving pressure, the decrease in left ACA reduced airflow and tidal volume. With increasing driving pressure, a decrease in left ACA changed the wall pressure profile, subjecting the submaximally abducted arytenoid cartilage and adjacent areas to airway collapse. CLINICAL RELEVANCE: The surgical target of ACA resulting in 88 % of maximal cross-sectional area seems to be appropriate.

Sedation with detomidine and acepromazine influences the endoscopic evaluation of laryngeal function in horses.

REASON FOR PERFORMING STUDY: Endoscopy of the upper airways of horses is used as a diagnostic tool and at purchase examinations. On some occasions it is necessary to use sedation during the procedure and it is often speculated that the result of the examination might be influenced due to the muscle-relaxing properties of the most commonly used sedatives. OBJECTIVES: To evaluate the effect of detomidine (0.01 mg/kg bwt) and acepromazine (0.05 mg/kg bwt) on the appearance of symmetry of rima glottidis, ability to abduct maximally the arytenoid cartilages and the effect on recurrent laryngeal neuropathy (RLN) grade. METHODS: Forty-two apparently normal horses underwent endoscopic examination of the upper airways on 3 different occasions, under the influence of 3 different treatments: no sedation (control), sedation with detomidine and sedation with acepromazine. All examinations were performed with a minimum of one week apart. The study was performed as an observer-blind cross-over study. RESULTS: Sedation with detomidine had a significant effect on the RLN grading (OR = 2.91) and ability maximally to abduct the left arytenoid cartilages (OR = 2.91). Sedation with acepromazine resulted in OR = 2.43 for the RLN grading and OR = 2.22 for the ability to abduct maximally. The ability to abduct maximally the right arytenoid cartilage was not altered. CONCLUSIONS: Sedating apparently healthy horses with detomidine or acepromazine significantly impairs these horses' ability to abduct fully the left but not the right arytenoid cartilage. This resulted in different diagnosis with respect to RLN when comparing sedation to no sedation. POTENTIAL RELEVANCE: Since the ability to abduct the right arytenoid cartilage fully is not altered by sedation, it is speculated that horses changing from normal to abnormal laryngeal function when sedated, might be horses in an early stage of the disease. To confirm or reject these speculations, further studies are needed. Until then sedation during endoscopy should be used with care.

Useful landmarks in arytenoid adduction and laryngeal reinnervation surgery.

OBJECTIVE: Knowledge of the location of the muscular process of the arytenoid cartilage and the recurrent laryngeal nerve is essential to performing a successful arytenoid adduction and laryngeal reinnervation surgery. We describe external landmarks useful in locating these structures. STUDY DESIGN: Cadaveric laryngeal dissection. METHODS: Posterior laryngeal dissection was performed in 16 human larynges. The position of the muscular process of the arytenoid was measured bilaterally relative to the inferior and superior borders of the thyroid lamina. The recurrent laryngeal nerve was followed distally from slightly below the level of the cricothyroid joint to its genu where its vertical course changes to an oblique intralaryngeal course. RESULTS: The muscular process of the arytenoid was usually found halfway between the roots of the superior and inferior cornu of the thyroid lamina. The recurrent laryngeal nerve was found just deep to the cricothyroid joint and lateral to the posterior cricoarytenoid muscle. There were no other nerves in this area. CONCLUSIONS: This study finds that the superior and inferior borders of the thyroid lamina are useful intraoperative landmarks to locate the muscular process of the arytenoid. The cricothyroid joint provides a good starting point to locate the recurrent laryngeal nerve, which can be identified slightly deeper between it and the posterior cricoarytenoid muscle.

Cricothyroid Articulation in Elderly Japanese With Special Reference to Morphology of the Synovial and Capsular Tissues.

OBJECTIVE: The present study aimed to clarify individual variations in the cricothyroid joint (CT joint). METHODS: Using 30 specimens of the CT joint obtained from elderly donated cadavers, we examined the composite fibers of the capsular ligament as well as the morphology of the synovial tissue. RESULTS: The capsular ligament consistently contained abundant thick elastic fiber bundles on the anterior side of the joint (anterior band) and an elastic fiber-made mesh on the posterior side (posterior mesh). The synovial membrane, lined by synovial macrophages, was usually restricted to the recesses in the medial or inferior end of the joint cavity. Without the synovial lining, elastic fibers of the capsular ligament were subsequently detached, dispersed, and exposed to the joint cavity. We also observed a folded and thickened synovial membrane and a hypertrophic protrusion of the capsular ligament. In six specimens, the joint cavity was obliterated by debris of synovial folds and elastic fiber-rich tissues continuous with the usual capsular ligament. Notably, with the exception of two specimens, we did not find lymphocyte infiltration in the degenerative synovial tissue. DISCUSSION: We considered the CT joint degeneration to be a specific, silent form of osteoarthritis from the absence of lymphocyte infiltration. For high-pitched phonation, the elderly CT joint seemed to maintain its anterior gliding and rotation with the aid of elastic fiber-rich tissues compensating for the loss of congruity between the joint cartilage surfaces. Conversely, however, high-pitched phonation may accelerate obliteration of the joint.

Exercise-induced stridor due to abnormal movement of the arytenoid area: videoendoscopic diagnosis and characterization of the "at risk" group.

We evaluated 4 patients who developed severe, symptomatic stridor during maximal cardiopulmonary exercise testing, all referred due to exercise-related dyspnea. All underwent resting, unsedated transnasal fiberoptic laryngoscopy and had normal findings. Four patients performed repeat maximal exercise testing with fiberoptic laryngoscopy, and they form the basis of this report. They had normal vocal cord motion during exercise, but developed abnormal anterior motion of the arytenoid and aryepiglottic folds only at peak exercise, leading to partial airway obstruction and severe stridor. This report details the workup and characterizes patients at risk for this unusual phenomenon.