Functional involvement of the sternohyoid muscle during breathing and swallowing in rats.

The sternohyoid muscle depresses the hyoid bone, but it is unclear whether the muscle contributes to respiratory and swallowing mechanisms. This study aimed to clarify whether the sternohyoid muscle participates in the respiration and swallowing reflex and how the activity is modulated in two conditions: with airway stenosis and with a fixed sternohyoid muscle length. Electromyographic activity in the sternohyoid, digastric, thyrohyoid, and diaphragm muscles was recorded in anesthetized rats. The sternohyoid muscle activity was observed in the inspiratory phase and during swallowing, and was well coordinated with digastric and thyrohyoid muscle activity. With airway stenosis, the respiratory activity per respiratory cycle was facilitated in all assessed muscles but the facilitation of activity per second occurred only in the digastric, thyrohyoid, and sternohyoid muscles. With airway stenosis, the swallowing activity was facilitated only in the digastric muscle but not in the thyrohyoid and sternohyoid muscles. Swallowing activity was not observed in the sternohyoid muscle in the condition with the sternohyoid muscle length fixed, although increased inspiratory activity remained. The current results suggest that 1) the sternohyoid muscle is slightly activated in the inspiratory phase, 2) the effect of airway stenosis on respiratory function may differ between the upper airway muscles and diaphragm, and 3) swallowing activity in the sternohyoid muscle is not dominantly controlled by the swallowing central pattern generator but instead occurs as a myotatic reflex.NEW & NOTEWORTHY We found that the sternohyoid muscle was activated in the inspiratory phase. However, increased airway resistance had different effects on the extrathoracic muscles than on the diaphragm. The swallowing activity of the sternohyoid disappeared when the muscle length was fixed. These findings suggest that the sternohyoid muscle may be activated not by the swallowing central pattern generator but as a myotatic reflex.

Physiologic and anatomic determinants of hyoid motion during drug-induced sleep endoscopy.

PURPOSE: To examine factors accounting for differences in hyoid motion during obstructive breathing events amongst obstructive sleep apnea (OSA) patients. METHODS: This was a prospective cohort study from June 2022 to October 2022. Patients with OSA undergoing evaluation for PAP alternative therapies with drug-induced sleep endoscopy with positive airway pressure titration (DISE-PAP). All patients underwent DISE-PAP and concurrent hyoid-focused ultrasound. DISE-PAP enabled measurement of airway physiology (flow, respiratory effort) and airway collapsibility (pharyngeal opening pressure, PhOP). Hyoid-ultrasound enabled hyoid bone movement during obstructive breathing. Respiratory effort was measured using a retro-epiglottic pressure-sensitive catheter. Hyoid position was measured using a standardized, awake, CT protocol. Regression analyses adjusted for age, race, sex, and BMI were performed to associate indices of respiratory effort and CT data with hyoid motion. RESULTS: On average, the 26 patients in this cohort were older (63.9 ± 10.5 years), male (69%), overweight (29.6 ± 3.99 kg/m2), and with moderate-to-severe OSA (26.8 ± 10.4 events/hour). Greater respiratory effort was associated with increased hyoid motion (ß [95% CI] = 0.034 [0.016,0.052], standardized ß = 0.261,p = 0.0003). Higher hyoid position was associated with greater hyoid displacement (ß [95% CI] = -0.20 [-0.38,-0.01], Standardized ß = -0.57, p = 0.036). CONCLUSION: Our data demonstrate that greater respiratory effort, higher hyoid position, and higher airway collapsibility, but not airflow, are associated with greater hyoid motion during obstructive breathing in DISE. These findings suggest that downward hyoid movement represents a compensatory response to upper airway obstruction. Further studies should investigate the vectors of hyoid motion to better understand its role in sleep-related airway collapse.

Disruption of hedgehog signaling leads to hyoid bone dysplasia during embryogenesis.

The development of the hyoid bone is a complex process that involves the coordination of multiple signaling pathways. Previous studies have demonstrated that disruption of the hedgehog pathway in mice results in a series of structural malformations. However, the specific role and critical period of the hedgehog pathway in the early development of the hyoid bone have not been thoroughly characterized. In this study, we treated pregnant ICR mice with the hedgehog pathway inhibitor vismodegib by oral gavage in order to establish a model of hyoid bone dysplasia. Our results indicate that administration of vismodegib at embryonic days 11.5 (E11.5) and E12.5 resulted in the development of hyoid bone dysplasia. We were able to define the critical periods for the induction of hyoid bone deformity through the use of a meticulous temporal resolution. Our findings suggest that the hedgehog pathway plays a crucial role in the early development of the hyoid bone. Additionally, our research has established a novel and easily established mouse model of synostosis in the hyoid bone using a commercially available pathway-selective inhibitor.

Biomechanical and Cortical Control of Tongue Movements During Chewing and Swallowing.

Tongue function is vital for chewing and swallowing and lingual dysfunction is often associated with dysphagia. Better treatment of dysphagia depends on a better understanding of hyolingual morphology, biomechanics, and neural control in humans and animal models. Recent research has revealed significant variation among animal models in morphology of the hyoid chain and suprahyoid muscles which may be associated with variation in swallowing mechanisms. The recent deployment of XROMM (X-ray Reconstruction of Moving Morphology) to quantify 3D hyolingual kinematics has revealed new details on flexion and roll of the tongue during chewing in animal models, movements similar to those used by humans. XROMM-based studies of swallowing in macaques have falsified traditional hypotheses of mechanisms of tongue base retraction during swallowing, and literature review suggests that other animal models may employ a diversity of mechanisms of tongue base retraction. There is variation among animal models in distribution of hyolingual proprioceptors but how that might be related to lingual mechanics is unknown. In macaque monkeys, tongue kinematics-shape and movement-are strongly encoded in neural activity in orofacial primary motor cortex, giving optimism for development of brain-machine interfaces for assisting recovery of lingual function after stroke. However, more research on hyolingual biomechanics and control is needed for technologies interfacing the nervous system with the hyolingual apparatus to become a reality.

Hyoid Bone Movement During Swallowing in Female Thyroidectomy Patients: A Kinematic Ultrasound Study.

The aim of this study was to investigate the measures of displacement, time and velocity of hyoid bone movement in female thyroidectomy patients. Fifty-eight ultrasound videos of 29 women during swallowing were analyzed. The sample was divided into experimental group (EG), composed of 12 women following total or partial thyroidectomy; and control group (CG) of 17 healthy women. The kinematic measures of displacement, time and velocity of hyoid bone displacement were tracked during swallowing of 10 ml of liquid (water) and 10 ml of thickened liquid (honey) in both groups for comparisons. Additional analysis included bolus consistency effect and relationship with clinical characteristics. Ultrasound videos were analyzed according to a standardized protocol using ImageJ software. Displacement, time and velocity of hyoid movement during swallowing of 10 ml of liquid or thickened liquid were not statistically different between female thyroidectomy patients and healthy women. There is no bolus consistency effect on kinematic measures in both groups, but among thyroidectomy patients, velocity of hyoid bone movement is significantly faster in those with swallowing complaints.

Impact of Varying Transcutaneous Electrical Stimulation Pulse Frequency on Swallow Timing Measures in Healthy Adults.

The impaired swallow timing subsequent to dysphagia or aging can potentially endanger swallowing safety and efficiency. Preliminary evidence has suggested that transcutaneous electrical stimulation (TES) may have the potential to affect swallow timing. However, limited knowledge exists regarding which TES parameters can optimize swallow timing. Pulse frequency is one of the primary TES parameters that can affect the quality of muscle contraction. Yet, no clear information exists regarding how changing pulse frequency impacts the timing of swallowing events. This study aimed to investigate the varying effects of submental TES pulse frequency on swallowing events during and post-15-min TES administration. Twenty-six healthy individuals between the ages of 20 and 54 participated in this study and were assigned to high pulse frequency (HPF) (80 Hz) or low pulse frequency (LPF) (30 Hz) groups. Videofluoroscopic swallowing study (VFSS) was used to record swallowing. Three trials of 10 mL pureed mixed with barium sulfate were presented under three different conditions, including pre-TES, during TES, and post-TES, in which measures were taken following 15 min of TES delivery. The swallow timing events that were measured in each condition were time to maximum hyoid elevation, time to maximum laryngeal elevation, laryngeal vestibule closure reaction time (LVCrt), laryngeal vestibule closure duration (LVCd), time to maximum pharyngeal constriction, and pharyngoesophageal segment (PES) opening duration. No significant pulse frequency effect was found on any swallow timing measures during or after 15 min of TES. Both protocols decreased the duration of some swallowing events during TES including time to maximum hyoid elevation [p < 0.017, ηp2 = 0.185], LVCrt [p < 0.032, ηp2 = 0.158], and time to maximum pharyngeal constriction [p < 0.034, ηp2 = 0.155]. None of the significant TES effects were continued when TES ceased after 15 min. Overall, both protocols have comparable immediate effects on shortening the duration of some swallowing events during TES. Future clinical trials should examine whether these physiologic timing changes can lead to safer and more efficient swallows in patients with dysphagia.

Dysphagia Pattern in Early to Moderate Parkinson's Disease Caused by Abnormal Pharyngeal Kinematic Function.

Airway invasion is common in patients with Parkinson's disease (PD) and can cause serious complications. However, a PD-related dysphagic pattern has not been clearly elucidated. In this study, 53 patients with early to moderate PD were enrolled to undergo a videofluoroscopic study of swallowing evaluation (VFSS) and a battery of neuropsychological assessments. A set of VFSS variables (three visuoperceptual, nine temporal, and six spatial) were measured. The main effects of bolus viscosity and volume on airway invasion were calculated. Statistical analyses were performed to determine key kinematic factors of airway invasion for swallowing each bolus type. Airway invasion frequency was significantly higher for liquid boluses (liquid vs. pudding P < 0.001; liquid vs. honey P = 0.006). Laryngeal vestibule closure reaction time (LVCrt) was the key kinematic factor of airway invasion for 3 ml liquid swallow (P = 0.040), anterior displacement of hyoid bone was the key kinematic factor for both 5 ml and 10 ml liquid swallows (P = 0.010, 0.034, respectively). Male sex and advanced Hoehn and Yahr stage were significantly related to reduced anterior displacement of hyoid bone. These results reveal the dysphagic pattern related to PD, demonstrating that prolonged LVCrt and reduced anterior displacement of hyoid bone are two crucial kinematic factors contributing to airway invasion during the liquid swallow. In addition, hyoid bone dysfunction was correlated with disease severity and male sex. Our findings warrant further investigation of the pathophysiological mechanism of dysphagia in PD and would guide clinical intervention.

Medicare volume and reimbursement trends in lingual and hyoid procedures for obstructive sleep apnea.

OBJECTIVES: This study aims to analyze utilization and reimbursement trends in lingual and hyoid surgery for obstructive sleep apnea (OSA). METHODS: Annual retrospective data on lingual and hyoid OSA surgeries was obtained from the 2000-2021 Medicare Part B National Summary Datafiles. Current Procedural Terminology (CPT) codes utilized included 21,685 (hyoid myotomy and suspension [HMS]), 41,512 (tongue base suspension [TBS]), 41,530 (radiofrequency ablation of the tongue [RFT]) and 42,870 (lingual tonsillectomy [LT]). RESULTS: The number of lingual and hyoid OSA surgeries rose 2777 % from 121 in 2000 to 3481 in 2015, before falling 82.9 % to 594 in 2021. Accordingly, Medicare payments rose 17,899 % from an inflation-adjusted $46,958 in 2000 to $8.45 million in 2015, before falling drastically to $341,011 in 2021. As the number of HMSs (2000: 91; 2015: 84; 2021: 165), TBS (2009: 48; 2015: 31; 2021: 16), and LTs (2000: 121; 2015: 261; 2021: 234) only experienced modest changes in utilization, this change was largely driven by RFT (2009: 340; 2015: 3105; 2021: 179). Average Medicare payments for RFT rose from $1110 in 2009 to $2994 in 2015, before falling drastically to $737 in 2021. CONCLUSION: Lingual and hyoid surgery for OSA has overall fallen in utilization among the Medicare population from 2000 to 2021. However, there was a brief spike in usage, peaking in 2015, driven by the adoption (and then quick dismissal) of RFT. The rise and fall in RFT use coincide with the rise and fall in reimbursement.

Adverse events associated with device assisted hyoid and tongue base suspension for obstructive sleep apnea.

PURPOSE: Hyoid and tongue base suspension may treat obstructive sleep apnea (OSA). This study summarizes device-related adverse events associated with the AIRvance and AIRLIFT systems used for hyoid and tongue base suspension. MATERIALS AND METHODS: The U.S. Food and Drug Administration's Manufacturer and User Facility Device Experience (MAUDE) database was queried for reports describing adverse events associated with hyoid or tongue base suspension from January 2012 to December 2022. RESULTS: 77 adverse events were identified. When performed separately, adverse events were equally as common with hyoid suspension as with tongue base suspension. More complications occurred postoperatively (51 [66.2 %]) than intraoperatively (26 [33.8 %]). The most reported adverse events were infection (23 [29.9 %]), broken screw (15 [19.5 %]), pain or discomfort (10 [13.0 %]), suture rupture (8 [10.4 %]), and dislodged screw (7 [9.1 %]). 10 infections required drainage or debridement; 12 required device explantation. CONCLUSIONS: The present study is the largest and most longitudinal review of adverse events associated with hyoid and tongue base suspension. Infection was the most common adverse event, and may require device explantation. While adverse events were most frequently attributed to device malfunction, broken screw, suture rupture, and broken needle were often attributed to operator error due to application of excessive force. Surgeon training to increase familiarity with hyoid and tongue base suspension may reduce adverse events caused by operator error. The MAUDE database is limited as a passive surveillance system. Standardized reporting may improve understanding of associated adverse events, enabling better informed comparisons between surgical treatment options for OSA.

A Possible Mechanism of Laryngohyoid Fractures in Hanging: A Preliminary Observation.

ABSTRACT: Fractures of the hyoid bone, particularly the greater horns, and thyroid cartilage (superior horns) are known to be associated with hanging deaths. Depending on the literature, the frequency of these fractures varies from 0% to 83%. The mechanism underlying these fractures is believed to be direct compression or indirect traction from the ligature. The relationship of these structures with the cervical spine cannot be visualized with traditional internal examination, due to obstruction by surrounding soft tissue. Postmortem computed tomography scan offers an unobscured view of the relationship of the laryngohyoid structures with the cervical spine.We aim to illustrate the phenomenon of displacement of the laryngohyoid structures associated with fractures of the horns. In our case reports, the laryngohyoid structures were displaced, not only superiorly and posteriorly, but also in 2 of the cases, by tilting, when the suspension point was at the posterior or posterolateral aspect of the neck. This displacement had caused the greater horns of the hyoid bone and superior horns of the thyroid cartilage to be approximated against the cervical spine, particularly the transverse processes. We believe that, in these circumstances, the fractures were caused by pressure of the horns of the laryngohyoid structures against the cervical spine.

Consideration of Hyoid Variability in the Diagnostic Workup of Fishbone Foreign Body Aspiration.

Fishbone foreign body (FFB) can lodge in the upper respiratory or gastrointestinal tracts and frequently cause discomfort. While FFBs are common, variations in the hyoid may present radiographically similarly. The authors present a case in which a 32-year-old woman presented with pain in the right neck with a globus sensation after eating fish. Examination, including flexible fiberoptic laryngoscopy, did not reveal a foreign body. Given the patients' persistent symptoms, a noncontrast computed tomography was performed, demonstrating a radiopaque body superior to the right lateral hyoid bone, consistent with FFB. Direct examination under anesthesia was performed, and no FFB was noted. A reassessment of the imaging suggested a likely aberrant hyoid bone. The authors report this case to remind clinicians that while rare, aberrant hyoid variants may mimic FFB. The authors also review the imaging findings of aberrant hyoid variants in this report, as recognition of hyoid variability can mitigate unnecessary intervention.

Effect of bolus property on swallowing dynamics in patients with dysphagia.

BACKGROUND: Modification of foods or liquids is commonly administered as part of dysphagia treatment. However, no consensus exists on the parameters for defining texture-modified food for patients with dysphagia. OBJECTIVES: The aim of this study was to evaluate the effect of food/liquid material on swallowing physiology in patients with dysphagia and to discuss the optimal food choice for direct swallowing therapy. MATERIALS AND METHODS: A total of 140 patients underwent a videofluoroscopic swallowing study using three test foods/liquids: 3 mL of mildly thick liquid (Thick liquid), jelly made of agar and polysaccharide (Jelly) and jelly made of pectin (Reset gel). Outcome measures of videofluoroscopic images, bolus transit time and hyoid movements were compared. RESULTS: The frequency of chewing movements was highest for Jelly, followed by Reset gel and Thick liquid. While the probability of oral residue was the highest for Reset gel, pharyngeal residue after swallowing was high for Thick liquid as compared to Jelly and Reset gel. Oral transit time and pharyngeal transit time for Thick liquid were significantly smaller than that for Jelly and Reset gel. Pharyngeal delay time was significantly smaller for Thick liquid than that for Jelly and Reset gel. There was no difference in hyoid elevation time and hyoid movement time among the conditions. CONCLUSION: Mildly thick liquid material may be optimal for patients with primarily oral motor function impairment and jelly, such as Reset gel, may be more suitable for patients with primarily pharyngeal motor function impairment or oral and pharyngeal coordinative motor function decline.

Gender differences in the upper airway, craniofacial morphological and polysomnographic parameters in patients with obstructive sleep apnoea.

BACKGROUND: Obstructive sleep apnoea (OSA) is a common sleep disorder characterized by repetitive episodes of upper airway collapse during sleep associated with arousals with or without oxygen desaturation. OBJECTIVE: This study aims to assess and analyse the morphological and neurological factors associated with obstructive sleep apnoea using polysomnography study data and two-dimensional cephalometric analysis of airway and skeletal parameters and their correlation in the patients with varying severities of obstructive sleep apnoea. METHODS: This study included 892 patients who underwent a complete work up, including a thorough history, clinical examination, standard polysomnography study and 2D cephalometric analysis to diagnose obstructive sleep apnoea. This study divided the participants into two groups based on the AHI score from the PSG study: AHI < 15 and AHI > 15 groups. The groups were further divided into male and female groups to study the prevalence of OSA. The analysis involved 13 cephalometric parameters: Seven linear and six angular measurements. The airway parameters measured in this study were minimum posterior airway space (PAS_min), hyoid bone to the mandibular plane (H_MNP) and soft palate length (SPL). All the subjects in this study underwent a standard overnight polysomnography study at the sleep centre in Samsung Medical Center. RESULTS: A total of 892 adult participants (M: F = 727:165, mean age: 50.6 ± 13.2 years and age range: 18-85 years). AHI >15 group was significantly older with higher BMI, NC and WC compared to the AHI < 15 groups in both male and female groups. There was statistical significance observed in N1, N3, AI, ODI, lowest saturation (%) and apnoea max length between the groups (p < .001). The arousal index (AI), especially the respiratory arousal index was considerably higher in the male group. There were significantly higher values in all the PSG parameters in the male group. In the airway parameters, hyoid bone position and soft palate length showed significant differences (p < .001), whereas the PAS did not show any differences (p = .225) between the AHI <15 and AHI >15 groups. The overall skeletal cephalometric parameters showed no significant differences between the groups, whereas the gonial angle and AB to mandibular plane angle showed significant differences in the female group (p = .028, p = .041 respectively). CONCLUSION: The partial correlation of cephalometric parameters with AHI showed a stronger correlation between the H_MNP and AHI in both men and women. The position of the hyoid bone and the soft palate length influences the progression of OSA, especially in male patients. This study found no direct association between the minimum PAS and varying severities of OSA in men and women. We speculate that more than the craniofacial morphological factors such as the sagittal and vertical position of the maxilla and the mandible, the position of the hyoid bone might be more responsible for the severity of OSA.

Lowered hyoid bone overlapping the thyroid cartilage in CT angiograms.

BACKGROUND: The ventral enclosure of the thyroid cartilage by a collapsed hyoid bone (CHB) is poorly encountered in previous research. It was aimed to observe whether or not these malformations could be found and detailed anatomically in a consistent lot of computed tomography (CT) files. METHODS: Two hundred archived CT angiograms were explicitly observed for the CHB anatomical variant. RESULTS: Different possibilities of CHB were found in 6/200 cases, five males and one female. The symmetrical overlap of the thyroid cartilage by the hyoid body was found in one male case. In three cases, two males and one female, there was asymmetrical overlapping due to tilted hyoid bones. In one male case with such asymmetrical CHD, an ossified anterior longitudinal ligament was noted: the tips of the superior horns of the thyroid cartilage reached lateral to it, thus being retropharyngeal. A different male case had a lowered hyoid with a greater horn fused to the superior horn of the thyroid cartilage, with an interposed ossified triticeal cartilage. In the last male case, the right greater horn collapsed laterally to an ossified triticeal cartilage fused with the thyroid cartilage's superior horn. CONCLUSIONS: The CHB is an undeniable anatomical possibility of an atavism that alters conventional anatomical and surgical landmarks. Different anatomical components of the hyoid bone can descend uni- or bilaterally.

The previously undescribed variant of the thyrohyoid muscle and its potential impact on surgical procedures.

The thyrohyoid muscle belongs to the infrahyoid group located in the carotid triangle. It normally originates from thyroid cartilage and inserts into hyoid bone. Quite often, it is continuous with the sternohyoid muscle. Furthermore, there are variants that have their origin in the cricoid cartilage only, however, this occurs very rarely. During anatomical dissection, a two-headed variant of this muscle was found. One head had its origin in the cricoid cartilage and the other in the thyroid cartilage. This variant of thyrohyoid had not been previously described in the available literature. Therefore, we believe that it may be referred to as the cricothyrohyoid muscle. As the thyrohyoideus is often used as a landmark during surgical procedures in the prelaryngeal area and as a muscle graft, a thorough knowledge of its anatomy and variation is extremely important. We speculate that the two-headed version of this muscle may be problematic during surgical procedures in this region, however, it may also provide more options as a muscular graft.

Hyoid displacement during swallowing function for completely edentulous subjects rehabilitated with mandibular implant retained overdenture.

BACKGROUND: Hyoid bone is attached to the mandible, tongue, larynx, temporal bone, and cervical spine via different types of muscles or ligaments. The tongue, mandible, and hyoid system play a crucial role in swallowing function. This within subject study aimed to evaluate the impact of mandibular implant overdentures on the displacement of the hyoid bones during the swallowing process. METHODS: Twenty five healthy edentulous subjects were selected for participating in the study. New complete dentures were constructed for all the participants. Subsequently two dental implants were inserted in the canine regions of the participant's mandibular arch. In order to retain the mandibular prosthesis in place, ball attachments were incorporated into the mandibular dentures to convert them into implant overdentures. Using 10 ml of thin liquid bolus, videofluoroscopy swallowing examination was performed in three different oral conditions: without complete dentures (WCD), with complete denture (CDs), and with a mandibular implant overdenture (IODs). ANOVA with Bonferroni test was used to analyze the data in order to determine how the hyoid displacement varied throughout different oral conditions. RESULTS: Compared to complete dentures, mandibular implant overdentures showed a significant decrease (P < 0.05) in both anterior hyoid displacement and duration of hyoid maximum anterior excursion (DOHMAE). However, there was a non-significant difference (P > 0.05) between the two oral circumstances in terms of superior hyoid displacement or duration for hyoid maximum elevation (DOHME). There is no penetration or aspiration for both complete denture and implant overdenture oral conditions. CONCLUSION: Implant retained overdentures have a positive effect on hyoid displacement during swallowing of thin liquid bolus consistency relative to conventional complete dentures. TRIAL REGISTRATION: Retrospectively registered (NCT06187181) 02/1/2024.

[Forensic assessment of neck organs alterations in hanging depending on the noose position]. / Sudebno-meditsinskaya otsenka izmenenii v organokomplekse shei pri poveshenii v zavisimosti ot polozheniya petli.

OBJECTIVE: To reveal statistical patterns in the localization of alterations in organs and tissues of the neck in hanging depending on the noose location. MATERIAL AND METHODS: In this study 222 forensic examination reports of corpses of those who died from hanging, conducted in the Bureau of Forensic Medical Expertise of Moscow Oblast for 2019, were investigated. Standard methods of mathematical statistics, including Mann-Whitney U Test and the Fisher's Exact Test, were used for calculations. Sex and age characteristics of hanging cases were given. RESULTS: Retrospective statistical analysis has shown that the pattern of injuries revealed in organs and tissues of the neck both depends (in cases of Amussat's sign) and does not depend (in cases of hemorrhages in the legs of sternocleidomastoid muscle, fractures of the hyoid bone and thyroid cartilage, Martin's sign) on the noose position. CONCLUSION: The obtained results can be used to develop measures aimed at improving the quality of forensic examination of hanging cases.

Pre-mandibular pharyngeal pouches in early non-teleost fish embryos.

The vertebrate pharynx is a key embryonic structure with crucial importance for the metameric organization of the head and face. The pharynx is primarily built upon progressive formation of paired pharyngeal pouches that typically develop in post-oral (mandibular, hyoid and branchial) domains. However, in the early embryos of non-teleost fishes, we have previously identified pharyngeal pouch-like outpocketings also in the pre-oral domain of the cranial endoderm. This pre-oral gut (POG) forms by early pouching of the primitive gut cavity, followed by the sequential formation of typical (post-oral) pharyngeal pouches. Here, we tested the pharyngeal nature of the POG by analysing expression patterns of selected core pharyngeal regulatory network genes in bichir and sturgeon embryos. Our comparison revealed generally shared expression patterns, including Shh, Pax9, Tbx1, Eya1, Six1, Ripply3 or Fgf8, between early POG and post-oral pharyngeal pouches. POG thus shares pharyngeal pouch-like morphogenesis and a gene expression profile with pharyngeal pouches and can be regarded as a pre-mandibular pharyngeal pouch. We further suggest that pre-mandibular pharyngeal pouches represent a plesiomorphic vertebrate trait inherited from our ancestor's pharyngeal metameric organization, which is incorporated in the early formation of the pre-chordal plate of vertebrate embryos.

The changes in oral volume and hyoid bone position after maxillomandibular advancement and genioglossus advancement for patients with obstructive sleep apnea.

INTRODUCTION: Maxillomandibular advancement (MMA) and genioglossus advancement (GA) are surgeries for patients with obstructive sleep apnea (OSA). Postoperative evaluation is primarily based on the apnea-hypopnea index (AHI) measured by polysomnography. The purpose of this study was to identify the timing of hyoid bone relocation after MMA and GA surgery and to investigate whether or not hyoid bone relocation can be an indicator of postoperative evaluation of OSA. METHODS: Patients with OSA underwent MMA and GA surgery. Changes in hyoid bone position and tongue-to-oral volume ratio were analyzed on lateral radiographs before, immediately after, and 1 year after surgery. Then, a correlation was verified between these changes and postoperative AHI. RESULTS: In 18 patients studied, the position of the hyoid bone did not show a constant tendency immediately after surgery. One year after surgery, the bone had moved anteriorly and toward the oral cavity in all patients compared to its preoperative position. And AHI correlated with the movement of the hyoid bone to the oral side. DISCUSSION: One year after surgery, the tongue was adapted to the newly enlarged oral space, and as a result, the low position of the hyoid bone before the operation was improved. The findings suggest that the degree of lowering of the hyoid bone may be an indicator of the improvement of AHI.

A Newly Discovered Tendon Between the Genioglossus Muscle and Epiglottic Cartilage Identified by Histological Observation of the Pre-Epiglottic Space.

Epiglottic retroversion is difficult to explain anatomically. One reason is inadequate structural identification of the ligaments in the submucosal tissue anterior to the epiglottis (pre-epiglottic space, PES). Although studies have shown that tongue root movement plays a role in epiglottic retroversion, few morphological reports have investigated the attachment of the lingual muscles to the epiglottis. This study reconstructed the fiber structure of the PES by comprehensively analyzing fiber alignment in the PES focusing on the hyoepiglottic ligament, which runs between the lingual muscles and the epiglottis. Gross and microscopic observations of the submucosal structures from the tongue to the larynx of 20 cadavers (10 men, 10 women; mean age 79 years) were performed. A tendon continuing from the posterior part of the genioglossus muscle and attaching to the center of the epiglottic cartilage was identified in the midline area of the epiglottis. We named this tendon the glossoepiglottic tendon. In contrast, the hyoepiglottic ligament is found between the hyoid bone and the epiglottis and is attached from the lateral margin of the epiglottic cartilage to its base. Furthermore, the glossoepiglottic tendon consists of a high-density fiber bundle that is thicker than the hyoepiglottic ligament. These results show that the conventional hyoepiglottic ligament has a two-layer structure consisting of an upper fiber bundle connected to the genioglossus muscle and a lower fiber bundle connected to the hyoid bone. Sustained contraction of the posterior part of the genioglossus muscle therefore places the epiglottis under persistent traction, suggesting that its relaxation may cause epiglottic retroversion.