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The aim of this study was to compare magnetic resonance imaging (MRI) features of reconstruction with locoregional flaps (LRFs) with free flaps (FFs) after surgical treatment for tongue cancer.In total, 115 cases of postoperative tongue carcinoma (67 cases of LRF surgery and 48 cases of FF surgery) were retrospectively reviewed. All patients had undergone nonenhanced and contrast-enhanced MRI at 0-4, 5-12, and 13-48 months after surgery. Signal intensity, margins, maximal size, contrast enhancement, change in the hyoglossus and mylohyoid muscles, recurrence, lymph node metastasis, and complications were evaluated.Significant differences were found between LRF and FF for signal intensity (P.001) in all 3 periods, with LRF mostly isointense with muscle on T1-weighted images (T1WIs) and FF producing mixed hyperintensity with muscular striations in all cases in T1WIs and T2-weighted images (T2 WIs). Margin definition was similar between groups in the early period, but sharp margins were more common in FF after 4 months (P ≤ .018). LRF was significantly smaller than FF in all periods (P ≤ .017). Both mylohyoid and hyoglossus enlargements were common in the early period in both groups, but all cases became atrophic later.MRI can differentiate LRFs from FFs in a variety of parameters after flap reconstructive surgery for tongue cancer.

Obstructive sleep apnea (OSA) is more common in patients with asthma, and inhaled corticosteroids may contribute to OSA pathogenesis in these patients. This study tested the effects of orally inhaled fluticasone propionate (FP) on extrinsic tongue muscles. Unanesthetized rats were treated with FP or placebo for 28 days. On day 29, tongue retrusive and protrusive functions were tested via hypoglossal nerve stimulation under a state of anesthesia, followed by genioglossus (GG), styloglossus (SG) and hyoglossus (HG) muscle extraction, after euthanasia, for histology [myosin heavy chain (MHC) fibers and laminin content reflecting extracellular matrix (ECM)]. On protrusive testing, FP increased percent maximum tetanic force at 40 Hz ( P = 0.03 vs. placebo) and endurance index ( P = 0.029 vs. placebo). On retrusive testing, FP increased maximum twitch ( P = 0.026 vs. placebo) and tetanic forces ( P = 0.02 vs. placebo) with no effect on endurance index. On histology, FP increased GG cross-sectional area of MHC type IIa ( P = 0.036 vs. placebo) and tended to increase type IIb ( P = 0.057 vs. placebo) fibers and HG MHC IIx fibers ( P = 0.065). The FP group had significantly increased laminin-stained areas, of greatest magnitude in the HG muscle. FP affects tongue protrusive and retrusive functions differently, concurrent with a shift in MHC fibers and increased ECM accumulation. These differential alterations may destabilize the tongue’s “muscle hydrostat” during sleep and promote collapse. NEW & NOTEWORTHY The effects of inhaled corticosteroid on upper airway may contribute to OSA pathogenesis in asthma. In this study, we tested the effects of orally inhaled fluticasone propionate on tongue protrusive and retrusive functions and on tongue extrinsic muscle fiber composition and molecular properties. We found that fluticasone treatment: 1) increased protrusive endurance and retrusive maximum twitch and tetanic force; and 2) on histology, increased cross-sectional area of myosin heavy chain (MHC) type IIa fibers and tended to increase cross-sectional area of MHC type IIb fibers in the protrusive muscle and of MHC IIx fibers in the retrusors. It also increased laminin-stained areas, across extrinsic tongue muscles, of greatest magnitude in the retrusors; and 3) reduced protein degradation and activated pathways associated with increased protein synthesis in the protrusor. These differential effects on the protrusors and retrusors may destabilize the tongue’s “muscle hydrostat” properties during sleep and promote collapse.

Purpose: Exercise-based treatment approaches for dysphagia may improve swallow function in part by inducing adaptive changes to muscles involved in swallowing and deglutition. We have previously shown that both aging and progressive resistance tongue exercise, in a rat model, can induce biological changes in the genioglossus (GG); a muscle that elevates and protrudes the tongue. However, the impacts of progressive resistance tongue exercise on the retrusive muscles (styloglossus, SG; hyoglossus, HG) of the tongue are unknown. The purpose of this study was to examine the impact of a progressive resistance tongue exercise regimen on the retrusive tongue musculature in the context of aging. Given that aging alters retrusive tongue muscles to more slowly contracting fiber types, we hypothesized that these biological changes may be mitigated by tongue exercise.Methods: Hyoglossus (HG) and styloglossus (SG) muscles of male Fischer 344/Brown Norway rats were assayed in age groups of young (9 months old, n = 24), middle-aged (24 months old, n = 23), and old (32 months old, n = 26), after receiving an 8-week period of either progressive resistance protrusive tongue exercise, or sham exercise conditions. Following exercise, HG and SG tongue muscle contractile properties were assessed in vivo. HG and SG muscles were then isolated and assayed to determine myosin heavy chain isoform (MyHC) composition.Results: Both retrusive tongue muscle contractile properties and MyHC profiles of the HG and SG muscles were significantly impacted by age, but were not significantly impacted by tongue exercise. Old rats had significantly longer retrusive tongue contraction times and longer decay times than young rats. Additionally, HG and SG muscles showed significant MyHC profile changes with age, in that old groups had slower MyHC profiles as compared to young groups. However, the exercise condition did not induce significant effects in any of the biological outcome measures.Conclusion: In a rat model of protrusive tongue exercise, aging induced significant changes in retrusive tongue muscles, and these age-induced changes were unaffected by the tongue exercise regimen. Collectively, results are compatible with the interpretation that protrusive tongue exercise does not induce changes to retrusive tongue muscle function.

By comparing styloglossus and hyoglossus muscle invasion (SHMI) of oral tongue squamous cell cancer (OTSCC) on MR imaging to pathological depth of invasion (DOI) and prognosis, we aimed to evaluate the clinical significance of MR imaging findings of SHMI.Forty-five, early stages and clinically N0 OTSCCs were retrospectively reviewed. Data included pathological DOI, DOI on MR imagings, two-year potential cervical lymph node positive, locoregional control, disease-free survival, and overall survival. Data were statistically compared between the groups with MR evidence of SHMI (SHMI+) and without MR evidence of SHMI (SHMI-).There were 17 SHMI + and 28 SHMI-. Elective neck dissections performed on 13 cases revealed five node positive cases, all of which were SHMI + . Pathological DOI in SHMI + was significantly larger than SHMI- (average 9.0 vs 4.6 mm, p0.001). All SHMI + revealed pathological DOI larger than 4 mm. The two-year potential cervical lymph node positive rate of SHMI + was significantly higher than SHMI- (p = 0.01). Locoregional control rate and disease-free survival of SHMI+ were significantly lower than in SHMI- (p = 0.02). There was no significant difference in overall survival. Interobserver agreement in evaluation of SHMI on MR imaging was good (kappa value = 0.72, p 0.001).Pathological DOIs of SHMI + were all larger than 4 mm, which is the cut-off point that National Comprehensive Cancer Network recommends for neck dissection, and SHMI + had a worse prognosis than SHMI-. SHMI + can be used as a criterion for elective neck dissection.

BACKGROUND AND PURPOSE: When optimising radiotherapy treatments today, the pharyngeal constrictor muscles and the larynx are usually regarded as the swallowing organs at risk (SWOARs). The purpose of this study was to identify and describe additional, previously undefined groups of muscles (functional units) involved in crucial components of swallowing (hyolaryngeal elevation (HLE), tongue base retraction (TBR) and tongue motion), and to emphasise their relevance in radiation-induced dysphagia.MATERIAL AND METHODS: Based on available literature on human anatomy and swallowing physiology, the functional units of muscles involved in HLE, TBR and tongue motion have been identified and described.RESULTS AND CONCLUSION: Functional swallowing units (FSUs) were defined as groups of swallowing muscles sharing their function, that are in close proximity to each other. Seven FSUs involved in HLE, TBR and tongue motion were identified: floor of mouth, thyrohyoid muscles, posterior digastric/stylohyoid muscles complex, longitudinal pharyngeal muscles, hyoglossus/styloglossus muscles complex, genioglossus muscles, intrinsic tongue muscles. The swallowing physiology and anatomy of the FSUs described in this paper will lead to a greater understanding of radiation-induced dysphagia mechanisms and, consequently, to an improvement in the development of swallowing sparing strategies. This article (PART 1) serves as the theoretical foundation for a subsequent article (PART 2), which provides detailed delineation guidelines for FSUs.

Objectives We aimed to discuss the definition of lingual lymph nodes based on the deep cervical fascia anatomy. Methods A total of 11 cadavers were histopathologically evaluated. Specimens were dissected into serial stepwise cross-sections. The deep cervical fascia and lymph nodes were evaluated by staining the cross-sections with Elastica van Gieson and hematoxylin and eosin stains, respectively. The gross anatomy of the deep cervical fascia was evaluated in 1 cadaver after bilateral dissection. Results A single severely degenerated medial lingual lymph node (MLLN) was identified in the lingual septum of 1 cadaver. A single lateral lingual lymph node (LLLN) was identified in 1 cadaver, between the genioglossus and the hyoglossus. The superficial layer of deep cervical fascia (SLDF) was found to split into two layers encapsulating the submandibular gland. The deeper portion of this fascia was in close contiguity with the hyoglossus and formed the boundary between the mouth and the neck. The SLDF was found to be discontinuous with the area between the sublingual space and the submandibular gland. Conclusions The SLDF could serve as an anatomical landmark for lingual lymph nodes, since it is considered to be the demarcating boundary during neck dissection. When lymph nodes that are located deeper than the SLDF were defined as lingual lymph nodes, 1 MLLN and 1 LLLN were identified.

During primate swallowing, tongue base retraction (TBR) drives the food bolus across the oropharynx towards the esophagus and flips the epiglottis over the laryngeal inlet, protecting against penetration and aspiration of food into the airway. Despite the importance of TBR for swallowing performance, the mechanics of TBR are poorly understood. Using biplanar videoradiography (XROMM) of four macaque monkeys, we tested the extrinsic muscle shortening hypothesis, which posits that shortening of the hyoglossus and styloglossus muscles pulls the tongue base posteriorly, and the muscular hydrostat or intrinsic tongue muscle hypothesis, which suggests that, because the tongue is composed of incompressible fluid, intrinsic muscle shortening increases tongue length and displaces the tongue base posteriorly. Our data falsify these hypotheses. Instead we suggest a novel hydraulic mechanism of TBR: shortening and rotation of suprahyoid muscles compresses the tongue between the hard palate, hyoid and mouth floor, squeezing the midline tongue base and food bolus back into the oropharynx. Our hydraulic mechanism is consistent with available data on human tongue swallowing kinematics. Rehabilitation for poor tongue base retraction might benefit from including suprahyoid muscle exercises during treatment.

Objective To determine whether muscle invasion evident on pretreatment imaging in p16 + oropharyngeal squamous cell carcinoma (OPSCC) correlates with recurrence. Study design Retrospective review. Methods Two-hundred and seventy-six patients with p16 + OPSCC treated at a tertiary referral center from 2003 to 2015 were analyzed. All scans were reviewed by a dedicated neuroradiologist with subspecialty expertise in head and neck imaging. Radiographic evidence of muscle invasion to the genioglossus, hyoglossus, medial pterygoid, and prevertebral muscles was analyzed. Local and regional recurrence rates were compared between the muscle invasion and no muscle invasion groups. Results One hundred and ninety patients met inclusion criteria with adequate follow-up data and pretreatment imaging. Patients were predominantly male (87.5% male) and smokers (65.6% smokers) with a mean age of 56.7 (standard deviation: 9.0 years). Most commonly invaded muscles in the muscle invasion group were hyoglossus (57.8%) and genioglossus (56.3%). There was no statistically significant difference in primary site or nodal recurrence between the combined group, including definite or possible muscle invasion and the group without muscle invasion (P = 0.205 and P = 0.569, respectively). Additionally, no statistically significant difference was present in recurrence-free and disease-specific survival between the two groups at 3- and 5-year follow-up (P > 0.05). Conclusion Radiographic evidence of muscle invasion does not appear to be a predictor of human papilloma virus (+) OPSCC recurrence. Additional studies are needed to validate our findings. Level of evidence 4 Laryngoscope, 129:871-876, 2019.

Introduction Neuromuscular electrical stimulation (NMES) for the treatment of swallowing disorders is delivered at a variety of stimulation frequencies. We examined the effects of stimulation frequency on tongue muscle plasticity in an aging rat model. Methods Eighty-six young, middle-aged, and old rats were assigned to either bilateral hypoglossal nerve stimulation at 10 or 100 Hz (5 days/week, 8 weeks), sham, or no-implantation conditions. Muscle contractile properties and myosin heavy chain (MyHC) composition were determined for hyoglossus (HG) and styloglossus (SG) muscles. Results Eight weeks of 100-Hz stimulation resulted in the greatest changes in muscle contractile function with significantly longer contraction and half-decay times, the greatest reduction in fatigue, and a transition toward slowly contracting, fatigue-resistant MyHC isoforms. Discussion NMES at 100-Hz induced considerable changes in contractile and phenotypic profiles of HG and SG muscles, suggesting higher frequency NMES may yield a greater therapeutic effect. Muscle Nerve, 2018.

The tongue is a dense muscular organ, in which the muscles are arranged in a confusing pattern. The intrinsic muscles were gross anatomically investigated in 25 cadavers to clarify their configuration. The superior longitudinal muscle (SLm) ran beneath the dorsal mucosa and was divided into bundles by the other muscles passing through it to the dorsum. The external bundle of the styloglossus, with the palatoglossus, coursed externally to the hyoglossus. Their fibers spread beneath the SLm or attached to the apex and the inferior longitudinal muscle (ILm) ascended from the root and joined them. The genioglossus and the anterior part of the hyoglossus extended internally and externally to the ILm, respectively, to the dorsum, and the vertical muscle was sandwiched between them. The transverse muscle passed laterally from the lingual septum. The fibers of the posterior part of the hyoglossus converged to the root and spread beneath the SLm. The intersections between these vertical and transverse fibers divided one another into bundles or lamellae. The middle bundle of the styloglossus, passing between the two parts of the hyoglossus, was divided into slips by the intersection with the genioglossus. The internal bundle of the styloglossus, with the glossopharyngeus, descended internally to the posterior part to the root. The findings indicate that the intrinsic and extrinsic muscles of the tongue are not independent groups, and their fibers form a three-dimensional latticework. Each muscle contains numerous bundles or lamellae as functional units that can act separately or cooperate across the muscles.

Our aim was to find out first whether the extrinsic muscles of the tongue are histologically identifiable, and secondly to what degree the use of the new criteria in the 8th editions of the American Joint Committee on Cancer(AJCC)/Union for International Cancer Control (UICC) manuals (which have recognised the importance of depth of invasion of tumour, rather than invasion of the extrinsic muscles of the tongue and extranodal extension), will alter staging of lingual squamous cell carcinoma (SCC). The histological sections from 165 patients who had had primary resection of lingual SCC were reviewed, and one or more extrinsic muscles of the tongue was identified in 100 patients (61%), with the genioglossus seen the most often (in 96). By contrast, the hyoglossus was identified in only eight patients, the styloglossus in two, and the palatoglossus in none. Identification was straightforward only in extensive resections. Applying the criteria from the 8th edition increased the number of pT3 SCC with a simultaneous reduction in pT4a tumours. The number of pN2b SCC was also reduced, but the new category of pN3b meant that overall 53% of tumours were upstaged. The kappa scores for agreement between the two sets of criteria were 0.221 (weighted 0.410) for the pT values, 0.508 (0.713) for pN values (but 0.227, weighted 0.386, if the pN0 values were removed before calculation), and 0.243 (0.514) for overall stage, indicating poor to fair agreement. We conclude that the removal of invasion of extrinsic muscles of the tongue as a criterion for a pT4a SCC is justified, and that many SCC of the tongue will be upstaged as a result of implementation of the 8th editions.

Introduction The hypoglossal nerve (HN) may be damaged during neck surgeries. A detailed understanding of the anatomy of the hypoglossal nerve in relation to various anatomical landmarks and surrounding structures is important to reduce procedural complications and the risk of nerve damage. Methods The study was carried out using 21 sagittal sections of head and neck of male cadavers (16 right and 5 left). To measure the required parameters the anatomical landmarks taken were the posterior belly of digastric muscle (PBD), descendens hypoglossi of ansa cervicalis (AC), bifurcation of common carotid artery (CCA), tip of the mastoid process (TMP), lingual artery (LA) at the posterior border of hyoglossus muscle, tip of greater cornu of hyoid bone (GH), bifurcation of CCA to the attachment of descendens hypoglossi (CCA-AC). Results The length of PBD was 3.77 ± 1.08 cm on right side and 3.15 ± 0.05 cm on left side. The extended length was measured from the TMP to GH which was 6.7 ± 1.23 cm on right side and 6.75 ± 0.75 on left side. The distance between HN to the GH did not vary much between right and left sides which were 1.21 ± 0.35 and 1.2 ± 0.69 cm respectively. The distance between HN and LA at the posterior border of hyoglossus was 1.12 ± 0.3 cm on right side and 0.5 ± 0.3 cm on left side. Discussion HN dissection is more complicated, as the location of the HN is much deeper. Moreover, there are no bony landmarks around the HN. Therefore PBD, CCA, ICA, ECA, LA were used as landmarks for HN in head and neck surgeries.

There are increased risks for deglutition disorders in people with Down syndrome (DS). Although mouse models have been used to study the biological underpinnings of DS in other areas, relatively little is known about swallowing phenotypes in these models. We hypothesized that swallowing performance would be affected in adult mouse models of DS, relative to typical control mice. Videofluoroscopic swallow studies (VFSS) were conducted on adults of two mouse models of DS: Ts65Dn and Dp(16)1Yey, and evaluated in comparison with age-matched controls. Relative to other groups, adult Ts65Dn showed significantly slower swallow rates, longer inter-swallow intervals (ISI), and greater numbers of jaw excursion cycles preceding each swallow. In contrast, adult Dp(16)1Yey mice showed swallowing performance similar to control mice. Exploratory quantitative analyses of the intrinsic tongue (transverse muscle), and extrinsic tongue muscles [genioglossus (GG), styloglossus (SG), and hyoglossus (HG)] showed no significant differences between genotype groups in myosin heavy chain isoform profiles. Collectively, these findings suggest that while swallowing is typical in adult Dp(16)1Yey, swallowing in adult Ts65Dn is atypical due to unknown causes. The finding that adult Ts65Dn may have utility as a model of dysphagia provides new opportunities to elucidate biological underpinnings of dysphagia associated with DS.

Objectives/hypothesis Upper airway stimulation for obstructive sleep apnea (OSA) via implantable hypoglossal nerve stimulation (HGNS) reduces airway obstruction by selectively stimulating nerve fibers that innervate muscles that produce tongue protrusion, while avoiding fibers that produce tongue retraction. This selective stimulation likely depends upon the location, intensity, and type of electrical stimulation delivered. This study investigates the impact of changing stimulation parameters on tongue muscle activation during HGNS using intraoperative nerve integrity monitoring in conjunction with electromyography (EMG). Study design Prospective case series. Methods Ten patients undergoing unilateral HGNS implantation for OSA in a university hospital setting were studied. Data included EMG responses in tongue muscles that produce protrusion (genioglossus), retraction (styloglossus/hyoglossus), and stiffening (transverse/vertical) in response to intraoperative bipolar probe electrical stimulation of lateral and medial branches of the hypoglossal nerve (HGN) and to implantable pulse generator (IPG) unipolar and bipolar settings after placement of the stimulation cuff. Results Stimulation of medial division HGN branches resulted in EMG responses in genioglossus muscles, but not in styloglossus/hyoglossus muscles, whereas stimulation of the lateral division HGN branches drove responses in styloglossus/hyoglossus muscles. Variable responses in transverse/vertical muscles were observed with stimulation of lateral and medial division branches. After electrode cuff placement, unipolar and bipolar HGN stimulation configurations of IPG resulted in unique patterns of muscle activation. Conclusions The relative activation of extrinsic and intrinsic tongue musculature by HGNS is determined by stimulus location, intensity, and type. Intraoperative neurophysiological monitoring of tongue muscle activation enables proper electrode cuff placement and may provide essential data for stimulus optimization. Level of evidence 4 Laryngoscope, 130:1836-1843, 2020.

Purpose Tongue base retraction during swallowing is critical to bolus propulsion in normal physiological swallowing. A better understanding of the hyoglossus and styloglossus, muscles thought to be key to tongue base retraction, will improve the quality of physical rehabilitation in dysphagic patients in addition to preventing iatrogenic damage to structures critical to deglutition. This study utilized muscle functional MRI in healthy adult human subjects in order to determine if the hyoglossus and styloglossus are active during swallowing. Methods and materials Data were collected for 11 subjects with mfMRI before and after swallowing, and after performing the Mendelsohn maneuver. Whole muscle relaxation time profiles (T2 signal in milliseconds) were calculated from weighted averages of multiple dual echo MRI slices, allowing for comparison of physiological response for the muscles in each test condition. Changes in effect size (Cohen’s d) of whole muscle T2 profiles were used to establish whether or not the hyoglossus and styloglossus are utilized during swallowing and during the Mendelsohn maneuver. Results Post-swallowing effect size changes (where a d value of > 0.20 indicates significant activity) for the T2 signal profiles of the hyoglossus and styloglossus were found to be d = 1.19 and 0.22, respectively. The hyoglossus showed an effect size change of d = 0.26 for the Mendelsohn maneuver. Conclusions Muscle functional MRI indicates a physiological response of the hyoglossus and styloglossus during swallowing, and the hyoglossus during the Mendelsohn maneuver.

Objectives/Hypothesis Determine swallowing mechanics associated with the first and second epiglottic movements, that is, movement to horizontal and full inversion, respectively, to provide a clinical interpretation of impaired epiglottic function. Study Design Retrospective cohort study. Methods A heterogeneous cohort of patients with swallowing difficulties was identified (n = 92). Two speech-language pathologists reviewed 5-mL thin and 5-mL pudding videofluoroscopic swallow studies per subject, and assigned epiglottic component scores of 0 = complete inversion, 1 = partial inversion, and 2 = no inversion, forming three groups of videos for comparison. Coordinates mapping minimum and maximum excursion of the hyoid, pharynx, larynx, and tongue base during pharyngeal swallowing were recorded using ImageJ software. A canonical variate analysis with post hoc discriminant function analysis of coordinates was performed using MorphoJ software to evaluate mechanical differences between groups. Eigenvectors characterizing swallowing mechanics underlying impaired epiglottic movements were visualized. Results Nineteen of 184 video swallows were rejected for poor quality (n = 165). A Goodman-Kruskal index of predictive association showed no correlation between epiglottic component scores and etiologies of dysphagia (λ = .04). A two-way analysis of variance by epiglottic component scores showed no significant interaction effects between sex and age (f = 1.4, P = .25). Discriminant function analysis demonstrated statistically significant mechanical differences between epiglottic component scores: 1 and 2, representing the first epiglottic movement (Mahalanobis distance = 1.13, P = .0007); and 0 and 1, representing the second epiglottic movement (Mahalanobis distance = 0.83, P = .003). Eigenvectors indicate that laryngeal elevation and tongue base retraction underlie both epiglottic movements. Conclusions Results suggest that reduced tongue base retraction and laryngeal elevation underlie impaired first and second epiglottic movements. The styloglossus, hyoglossus, and long pharyngeal muscles are implicated as targets for rehabilitation in dysphagic patients with impaired epiglottic inversion. Level of Evidence 2b Laryngoscope, 2015

The purpose of the present study was to classify the courses of the human sublingual artery. For this purpose, the arteries supplying the floor of the mouth and the tongue were gross anatomically investigated using 101 sides of 53 cadavers. The courses were divided into three categories: those passing medial or lateral to the hyoglossus (categories M and L) and that piercing the mylohyoid (category P); they were subdivided into five types. Category M had one type, regarded as the usual one, in which the lingual artery took the usual pattern of distribution. Categories L and P, in which the sublingual artery arose from the facial or submental artery, had the respective two types and were collectively regarded as the unusual type. Sixty-one and 36 of the 101 sides were of the usual and unusual types, respectively, the latter of which included 17 of category L and 19 of category P. The remaining four were variations of the lingual artery itself. On examining the types by gender, the usual type was more often found in females (75.6 %), whereas the unusual type was more often found in males (48.1 %). Bilateral occurrence of the same type was often found in both the usual type (77.4 %) and the unusual type (65.0 %). Existence of the sublingual artery branch significantly increased the thicknesses of the submental arteries. The classification proposed here will conceivably contribute to safer dental implant surgery and more accurate interpretation of angiographic images of arteries in the floor of the mouth.

The purpose of this study was to show the benefit of visualizing a tree-dimensional (3D) image of the tongue's muscle structure, which until now has been regarded as fully understood. Until now, no suitable 3D observation methods have been developed for soft tissue, such as the tongue, using histological magnification. For this purpose, this study used a micro-computed tomographic method (micro-CT) and image processing after the fixation, decalcification, and dehydration of a mouse tongue. Results: 3D rendered images of tongue muscles obtained by micro-CT showed every mus- cle and their relationships to each other. The superior longitudinal and the hyoglossus muscles of the tongue made up one group, while the inferior longitudinal and the styloglossus muscles of the tongue made up another. The boundary of the two muscles in each group was difficult to distin- guish. On the other hand, what appear to be newly described muscles were identified. These re- sults indicate that our micro-CT method is beneficial and that classical knowledge of tongue mus- cles derived from two-dimensional (2D) images does not fully describe the actual complexity of the tongue muscles. In our opinion, 3D rendered images mixed with raw structure can provide a more in-depth picture of the tongue from an integrated as well as an analytical perspective.

Although respiratory muscle motor units have been studied during natural breathing, simultaneous measures of muscle force have never been obtained. Tongue retractor muscles, such as the hyoglossus (HG), play an important role in swallowing, licking, chewing, breathing, and, in humans, speech. The HG is phasically recruited during the inspiratory phase of the respiratory cycle. Moreover, in urethane anesthetized rats the drive to the HG waxes and wanes spontaneously, providing a unique opportunity to study motor unit firing patterns as the muscle is driven naturally by the central pattern generator for breathing. We recorded tongue retraction force, the whole HG muscle EMG and the activity of 38 HG motor units in spontaneously breathing anesthetized rats under low-force and high-force conditions. Activity in all cases was confined to the inspiratory phase of the respiratory cycle. Changes in the EMG were correlated significantly with corresponding changes in force, with the change in EMG able to predict 53–68% of the force variation. Mean and peak motor unit firing rates were greater under high-force conditions, although the magnitude of discharge rate modulation varied widely across the population. Changes in mean and peak firing rates were significantly correlated with the corresponding changes in force, but the correlations were weak ( r2 = 0.27 and 0.25, respectively). These data indicate that, during spontaneous breathing, recruitment of HG motor units plays a critical role in the control of muscle force, with firing rate modulation playing an important but lesser role.

Presence of accessory submandibular salivary gland (ASSG) is an extremely rare variation. Knowledge of its relations could be very useful to oral and maxillofacial surgeons, head and neck surgeons, and radiologists. During dissection classes, an ASSG was noted between the mylohyoid and hyoglossus muscles. The main submandibular salivary gland had superficial and deep parts. The deep part was narrow and measured about 5 cm. The lingual nerve passed between the superficial and deep parts. The accessory submandibular gland was situated below and parallel to the deep part of SSG. It also measured 5 cm. The ASSG had its own duct, which joined the duct of main gland. The ASSG and the deep part of the SSG were united at the lateral border of geniohyoid muscle to give a characteristic ‘‘horseshoe’’ appearance. The ASSG overlapped both lingual and hypoglossal nerves.

The pharyngeal muscles overlap each other and some of their parts have different areas of origin. Such arrangements make the interrelationships among pharyngeal muscles complicated. This study investigated the attachments of the middle constrictor to clarify its configuration and re-examine its functions. The gross anatomies of the pharyngeal and neighboring muscles were examined in 41 cadavers. The middle constrictor arose from the stylohyoid ligament and the hyoid bone, and its fibers were divided into three overlapping groups. The anterosuperior group ascended posterosuperiorly from the ligament and the lesser horn and fanned out. The middle group ascended posterosuperiorly from the greater horn and fanned out. The posteroinferior group fanned out from the posterior part of the greater horn, while the middle constrictor arose internally to the hyoglossus; some fibers often passed externally, and their fibers sometimes intersected around the lingual artery, which ran between them. Some fibers attached to the hyoglossus, occasionally to the stylohyoid and the posterior belly of the digastric, but seldom to the lingual artery and the triticeal cartilage in the thyrohyoid ligament. The three groups were inserted into the pharyngeal raphe, and the descending fibers joined the longitudinal pharyngeal muscles. The ascending and descending fibers rarely reached the top of the pharynx and the thyroid cartilage, respectively. The fiber arrangement suggested that, besides constriction of the pharynx, the ascending and descending fibers of the middle constrictor can act as an elevator muscle, and the irregular attachments could affect the functions of the muscles and vessels. Clin. Anat. 603–609, 2014. © 2013 Wiley Periodicals, Inc.

The TNM classification for oral malignancies has been criticized for its upstaging to T4a when tumour involves styloglossus, hyoglossus, palatoglossus and genioglossus. The aims of this study were to (1) create an anatomical computer atlas of extrinsic tongue musculature, and (2) reassess the original staging of pre-treatment archived magnetic resonance images (MRI) of tongue carcinomas using the strict extrinsic muscle criteria. The anatomy of the extrinsic tongue muscles was mapped using images from the Visible Human Project (VHP) to create a computer model of the extrinsic tongue muscles. This was co-registered with 87 archived pre-staging MRI scans of tongue carcinomas to assess tumour ingress of the extrinsic tongue muscles. Of the 87 image sets reviewed, 16 were of superficial tumours not visible on MRI. In the remaining 71 cases that showed positive extrinsic muscle tumour ingress, 52% were upstaged from T1/2/3 tumours to cT4a based upon this finding. Extrinsic lateral and genioglossus muscle invasion did not predict occult cervical lymph node invasion or disease-related survival. In conclusion, tumour invasion of styloglossus or hyoglossus would result in the majority of lateral tongue tumours being staged T4a. Such stratification is of little clinical relevance, and an alternative more reliable method is required.

The base of tongue plays an important role in the pathophysiology of obstructive sleep apnea (OSA), and addressing the tongue base can be an alternative for continuous positive airway pressure and some surgeries done such as uvulopalatopharyngoplasty to treat OSA. One of the options to address the tongue base to treat the OSA is stimulation of human hypoglossal nerve with implantable devices. Thus, one needs to know the physiology of the human hypoglossal nerve to understand the mechanism of such devices. The human hypoglossal nerve is the primary motor nerve that innervates 7 of the 8 extrinsic and intrinsic muscles of the tongue on each side, except palatoglossus muscle, which is innervated by the ipsilateral vagus nerve. At the level of the hyoid bone, the human hypoglossal nerve (the proximal and midthird) is normally unfasciculated, becoming fascicular only in its distal third where it branches. The lateral branch has many small, independent branches that supply the styloglossus, hyoglossus, and inferior longitudinalis muscles. The medial branch innervates the genioglossus, superior longitudinalis, transversalis, and verticalis muscles.

The salivary glands comprise the parotid, the submandibular and the sublingual glands as well as small subsidiary glands scattered beneath the mucosa of the buccal cavity. The largest, the parotid, drains by its duct into the mouth at the level of the second upper molar tooth. It is traversed by the facial nerve, which may be invaded by a parotid carcinoma or damaged during parotid surgery. The submandibular gland has a superficial part, at the angle of the jaw, wedged between the mandible and the mylohyoid muscle. Its deep part projects deep to mylohyoid along the hyoglossus. Its duct opens alongside the fraenum of the tongue, where it is easily visible, and is crossed by the lingual nerve. The sublingual gland lies in the floor of the mouth into which it drains directly by a series of short ducts.

The tongue is a highly muscular organ, and the extrinsic muscles of the tongue overlap one another, which makes their configuration intricate. The aim was to clarify their spatial interrelationships. The extrinsic muscles of the tongue were gross anatomically investigated in 42 cadavers. The hyoglossus consisted of two parts arising from the hyoid body and the greater horn, respectively. They ascended to the tongue external to the genioglossus. The quadrilateral anterior part contained several parallel bundles, and the triangular posterior part comprised of three bundles converging to the insertion. The genioglossus consisted of many compartments. Although its fibers radiated from the mental spine to the tongue internal to the inferior longitudinal muscle, the lateral fibers of the inferior parts passed externally to it, and the most inferior part attached to the hyoid bone and the epiglottis. The chondroglossus arising from the lesser horn ascended internally to the lateral fibers of the inferior parts. The styloglossus arising from the styloid process coursed externally and internally to the hyoglossus and between its two parts. The external and internal bundles fused with the fibers of the palatoglossus and the superior pharyngeal constrictor, respectively. Three bundles were inserted into the apex with the inferior longitudinal muscle or joined the inferior parts of the genioglossus. The extrinsic muscles are subdivided into small groups of fibers depending on their spatial interrelationships, suggesting that they contain many functional units. Some units act separately, and others cooperate across the traditional boundaries of the muscles.

There are many reports on the variation of origin site of the lingual artery branching from the external carotid artery. However, there are few reports systematically investigating the course of the lingual artery in detail from branching site to the body of tongue. The purpose of this study is to classify systematically the courses of the lingual artery including variations. Using 111 body sides of 63 Japanese cadavers for dissection practices, the lingual artery and the surrounding structures were investigated gross anatomically. The courses of the lingual artery were classified into five types based on the positional relationships with the hyoglossus and the mylohyoid as follows; type M: coursing medial to the hyoglossus (normal course, 104 sides), type L: coursing lateral to the hyoglossus (2 sides), type T: transferring its course from lateral to medial to the hyoglossus (2 sides), type P: penetrating the mylohyoid (2 sides), and type C: the coinciding of types M and P (1 side). Types L, T, P, and C were considered to be variant lingual arteries. Types M and T, type L, and type P arose from the external carotid, facial, and submental arteries, respectively. In types L and P, adding to the variant lingual artery, the remnant of the normal lingual artery was also observed. The present study provides detailed information on the courses of lingual artery which will be of clinical importance especially in the super-selective arterial angiography.

A wide range of pathologic processes may involve the floor of the mouth, the part of the oral cavity that is located beneath the tongue. They include lesions that arise uniquely in this location (eg, ranula, submandibular duct obstruction) as well as various malignancies, inflammatory processes, and vascular abnormalities that may also occur elsewhere in the head and neck. Some lesions that arise in superficial tissues such as the mucosa may be easily diagnosed at physical examination. However, computed tomography, magnetic resonance imaging, or ultrasonography may be necessary for a reliable assessment of lesion extension to deeper structures. In such cases, knowledge of the complex muscular, vascular, glandular, ductal, and neural anatomy of the region is important for accurate diagnosis and treatment planning. Familiarity with the radiologic imaging appearances of the floor of the mouth and recognition of anatomic landmarks such as the mylohyoid and hyoglossus muscles are especially useful for localizing disease within this region.

The human tongue muscle hyoglossus (HG) muscle is active in oro-motor behaviors encompassing a wide range of tongue movement speeds. Here we test the hypothesis that the human HG is composed of “uncommon” myosin heavy chain (MHC) isoforms MHCembryonic, MHCneonatal and MHCslow tonic as has been reported for other head and neck muscles active during kinematically diverse behaviors. Following reaction of human HG with antibodies specific for MHCI, MHCIIA, MHCII, MHCembryonic, MHCextraocular, MHCneonatal and MHCslow tonic only antibodies to MHCI, MHCIIA and MHCIIA-X label more than occasional muscle fibers. These antibodies describe five phenotypes with prevalence MHCIIA>MHCI>MHCI-IIX>MHCI-IIA>MHCIIX. In MHC composition, the human HG is thus similar to human appendicular muscles, the human tongue muscle styloglossus and many human head and neck muscles but different from human masseter and extraocular muscles which contain five or more MHC isoforms.

The pharyngeal swallow can be elicited as an isolated event but, in normal animals, it occurs within the context of rhythmic tongue and jaw movement (RTJM). The response includes activation of the multifunctional geniohyoid muscle, which can either protract the hyoid or assist jaw opening; in conscious nonprimate mammals, two bursts of geniohyoid EMG activity (GHemg) occur in swallow cycles at times consistent with these two actions. However, during experimentally elicited pharyngeal swallows, GHemg classically occurs at the same time as hyoglossus and mylohyoid activity (short latency response) but, when the swallow is elicited in the decerebrate in the absence of RTJM, GHemg occurs later in the swallow (long latency response). We tested the hypothesis that it was not influences from higher centers but a brain stem mechanism, associated with RTJM, which caused GHemg to occur earlier in the swallow. In 38 decerebrate piglets, RTJM occurred sporadically in seven animals. Before RTJM, GHemg had a long latency, but, during RTJM, swallow related GHemg occurred synchronously with activity in hyoglossus and mylohyoid, early in the swallow. Both early and late responses were present during the changeover period. During this changeover period, duplicate electrodes in the geniohyoid could individually detect either the early or the late burst in the same swallow. This suggested that two sets of geniohyoid task units existed that were potentially active in the swallow and that they were differentially facilitated or inhibited depending on the presence or absence of rhythmic activity originating in the brain stem.

The present study evaluated the effect of coactivation of tongue protrusors and retractors on pharyngeal patency in patients with obstructive sleep apnea. The effect of genioglossus (GG), hyoglossus (HG), and coactivation of both on nasal pressure (Pn):flow relationships was evaluated in a sleep study (SlS, n = 7) and during a propofol anesthesia study (AnS, n = 7). GG was stimulated with sublingual surface electrodes in SlS and with intramuscular electrodes in AnS, while HG was stimulated with surface electrodes in both groups. In the AnS, the cross-sectional area (CSA):Pn relationships was measured with a pharyngoscope to estimate velopharyngeal compliance . In the SlS, surface stimulation of GG had no effect on the critical pressure (Pcrit), HG increased Pcrit from 2.8 ± 1.7 to 3.7 ± 1.6 cmH2O, but coactivation lowered Pcrit to 0.2 ± 1.9 cmH2O ( P < 0.01 for both). In the AnS, intramuscular stimulation of GG lowered Pcrit from 2.6 ± 1.3 to 1.0 ± 2.8 cmH2O, HG increased Pcrit to 6.2 ± 2.5 cmH2O ( P < 0.01), and coactivation had a similar effect to that of GG (Pcrit = 1.2 ± 2.4 cmH2O, P < 0.05). None of the interventions affected significantly velopharyngeal compliance. We conclude that the beneficial effect of coactivation depends on the pattern of GG fiber recruitment: although surface stimulation of GG failed to protrude the tongue, it prevented the occlusive effect of the retractor, thereby improving pharyngeal patency during coactivation. Stimulation of deeper GG fibers with intramuscular electrodes enlarged the pharynx, and coactivation had no additive effect.

Dermoid or epidermoid cysts usually appear as a midline swelling in the sublingual region or the floor of the mouth. There have been several case reports of lateral neck epidermoid cysts, which are considered to arise as median cysts and extend to the space between the mylohyoid and hyoglossus muscles. We report a rare case of epidermoid cyst arising between the submandibular gland and the platysma. A 40-year-old woman was referred to our hospital for evaluation of an asymptomatic swelling in the submandibular region. The MR imaging showed a well-defined cystic mass between the submandibular gland and the platysma. The lesion was extirpated under general anesthesia. No adhesion to the surrounding tissues was observed. White caseous material was contained in the lesion. Histopathologically, the cyst lumen was filled with keratin and lined by stratified squamous epithelium. There was no skin appendage, and a final diagnosis of epidermoid cyst was made. The postoperative course has been good, without any complications.

Background Neurostimulation of the hypoglossal nerve has shown promising results in the treatment of obstructive sleep apnea. This anatomic study describes the detailed topography of the hypoglossal nerve's motor points as a premise for super-selective neurostimulation in order to optimize results and minimize the risk of complications related to main nerve trunk manipulation. Methods Thirty cadaveric hypoglossal nerves were dissected and characterized by number of branches, arborization pattern, and terminal branch motor point location. For each motor point, the distance to cervical midline (x axis), distance to posterior aspect of the symphysis (y axis), and depth from the plane formed by the inferior border of symphysis and anterior border of hyoid (z axis) were recorded. Results The average number of distal branches for each hypoglossal nerve was found to be 9.95 ± 2.28. The average number of branches per muscle was found to be 3.3 ± 1.5 for the hyoglossus muscle, 1.8 ± 0.9 for the geniohyoid muscle, and 5.0 ± 1.6 for the genioglossus muscle. It was found that branches to the genioglossus and geniohyoid muscles were located closer to midline (relative lengths of 0.19 ± 0.07 and 0.19 ± 0.05, respectively) while hyoglossus branches were located more laterally (0.38 ± 0.10 relative length). On the y-axis, the branches to the genioglossus were the most anterior and therefore closest to the posterior symphysis of the mandible (relative length of 0.48 ± 0.11), followed by the geniohyoid (0.66 ± 0.09), and the hyoglossus (0.76 ± 0.16). The branches to the geniohyoid were the most superficial (relative length of 0.26 ± 0.06), followed by the genioglossus (0.36 ± 0.09), and finally, the hyoglossus branches (0.47 ± 0.11), which were located deeply. Conclusion A topographical map of the hypoglossal nerve terminal motor points was successfully created and could provide a framework for the optimization of the neurostimulation techniques.

Tongue muscles are difficult to study by dissection and imaging methods because of the intermeshing of the muscular fibers. The study of the architecture of the tongue was based on 853 tongue sections of a fetus aged 32 weeks after conception. The analysis of the sections allowed demonstration of the different intrinsic and extrinsic muscles of the tongue, to determine their situation from the palatoglossus arch to the apex of the tongue. The tongue muscles are organized in different layers from cranial to caudal and from lateral to medial, one medial for the genioglossus muscle, one paramedial for the hyoglossus, the styloglossus and the inferior longitudinal muscles. In the anterior third of the tongue, the muscles presented a concentric organization.

Rationale: Historically, respiratory-related research in sleep apnea has focused exclusively on the extrinsic tongue muscles (i.e., genioglossus, hyoglossus, and styloglossus). Until recently, the respiratory control and function of intrinsic tongue muscles (i.e., inferior and superior longitudinalis, transverses, and verticalis), which comprise the bulk of the tongue, were unknown. Objectives: The current study sought to determine if extrinsic and intrinsic tongue muscles are coactivated in conditions of hypoxemia comparable to that experienced by adults with obstructive sleep apnea. Measurements: Esophageal pressure and EMG activity of an extrinsic (hyoglossus) and an intrinsic (superior longitudinal) tongue muscle were studied in anesthetized, tracheotomized, spontaneously breathing rats. Average EMG activity was compared in a control gas condition (PaO2, 160 ± 12 mm Hg) and in mild isocapnic hypoxia (PaO2, 69 ± 7.2 mm Hg), with and without brief (3-breath) airway occlusions, pre- and postbilateral vagotomy. Main Results: (1) intrinsic and extrinsic tongue muscles are coactivated in mild hypoxia, (2) airway occlusion increased the activities of intrinsic retractor muscles in mild hypoxia, and (3) extrinsic retractor muscles have a steeper rate of rise of activity and an earlier burst onset relative to intrinsic retractor activities in mild hypoxia. Conclusions: These findings support our working hypothesis that airway patency is maintained not simply by activation of extrinsic tongue muscles but by the coactivation of intrinsic and extrinsic protrudor and retractor muscles.

Laboratory rats were acutely implanted with an electrode array composed of eight independently controllable contacts applied to ventral and dorsal aspects of the left and right hypoglossal nerves (HGNs) and their branches. Bipolar intramuscular electromyographic (EMG) electrodes were implanted into the left and right genioglossus, hyoglossus and styloglossus muscles to identify which muscles were activated during stimulation via the contacts. Elicited movements, including changes in the position of the tongue and in the size and the shape of the airway, were documented video-graphically through a surgery microscope and an endoscope. Constant current electrical stimulation activated various combinations of electrode contacts and the stimulation patterns were correlated with corresponding oral movements, airway sizes, and EMG activities. Results demonstrate that graded responses and differential activation of the various tongue muscles are achievable by stimulation of specific contacts in the electrode array. These effects are interpreted to result from the targeted activation of regions of the nerve lying under and between the electrodes. Further testing established that the muscle responses elicited by unilateral electrical stimulation with the present approach can be smoothly graded, that the muscle responses resulted in opening of the airway and could be reliably maintained for long durations.

Obstructive sleep apnea (OSA) patients have increased upper airway muscle activity, including such lingual muscles as the genioglossus (GG), geniohyoid (GH), and hyoglossus (HG). This adaptation partially protects their upper airway against obstructions. Rodents are used to study the central neural control of sleep and breathing but they do not naturally exhibit OSA. We investigated whether, in chronically instrumented, behaving rats, disconnecting the GH and HG muscles from the hyoid (H) apparatus would result in a compensatory increase of other upper airway muscle activity (electromyogram, EMG) and/or other signs of upper airway instability. We first determined that, in intact rats, lingual (GG and intrinsic) muscles maintained stable activity levels when quantified based on 2 h-long recordings conducted on days 6 through 22 after instrumentation. We then studied five rats in which the tendons connecting the GH and HG muscles to the H apparatus were experimentally severed. When quantified across all recording days, lingual EMG during slow-wave sleep (SWS) was modestly but significantly increased in rats with surgically altered upper airway [8.6 ± 0.7% (SE) vs. 6.1 ± 0.7% of the mean during wakefulness; p = 0.012]. Respiratory modulation of lingual EMG occurred mainly during SWS and was similarly infrequent in both groups, and the incidence of sighs and central apneas also was similar. Thus, a weakened action of selected lingual muscles did not produce sleep-disordered breathing but resulted in a relatively elevated activity in other lingual muscles during SWS. These results encourage more extensive surgical manipulations with the aim to obtain a rodent model with collapsible upper airway.

A new technique, tagged Cine-Magnetic Resonance Imaging (tMRI), was used to develop a mechanical model that represented local, homogeneous, internal tongue deformation during speech. The goal was to infer muscle activity within the tongue from tissue deformations seen on tMRI. Measurements were made in three sagittal slices (left, middle, right) during production of the syllable /ka/. Each slice was superimposed with a grid of tag lines, and the approximately 40 tag line intersections were tracked at 7 time-phases during the syllable. A local model, similar to a finite element analysis, represented planar stretch and shear between the consonant and vowel at 110 probed locations within the tongue. Principal strains were calculated at these locations and revealed internal compression and extension patterns from which inferences could be drawn about the activities of the Verticalis, Hyoglossus, and Superior Longitudinal muscles, among others.

1. Our purpose was to examine the effects of chemoreceptor stimulation and lung inflation on neural drive to tongue protrudor and retractor muscles in the rat. 2. Inspiratory flow, tidal volume, transpulmonary pressure, compliance and electromyographic (EMG) activity of genioglossus (GG), hyoglossus (HG) and inspiratory intercostal (IIC) muscles were studied in 11 anaesthetized, tracheotomized and spontaneously breathing rats. Mean EMG activity during inspiration was compared with mean EMG activity during an occluded inspiration, at each of five levels of inspired CO(2) (0, 3, 6, 9 and 12 %). 3. Lung inflation suppressed EMG activity in all muscles, with the effect on both tongue muscles exceeding that of the intercostal muscles. Static elevations of end-expiratory lung volume evoked by 2 cmH(2)O positive end-expiratory pressure (PEEP) had no effect on tongue muscle activity. 4. Despite increasing inspiratory flow, tidal volume and transpulmonary pressure, the inhibition of tongue muscle activity by lung inflation diminished as arterial PCO2 (P(a),CO(2)) increased. 5. The onset of tongue muscle activity relative to the onset of IIC muscle activity advanced with increases in P(a),CO(2) but was unaffected by lung inflation. This suggests that hypoglossal and external intercostal motoneuron pools are controlled by different circuits or have different sensitivities to CO(2), lung inflation and/or anaesthetic agents. 6. We conclude that hypoglossal motoneuronal activity is more strongly influenced by chemoreceptor-mediated facilitation than by lung volume-mediated inhibition. Hypoglossal motoneurons driving tongue protrudor and retractor muscles respond identically to these stimuli.

This study was designed to investigate the influence of hypoxia-evoked augmented breaths (ABs) on respiratory-related tongue protrudor and retractor muscle activities and inspiratory pump muscle output. Genioglossus (GG) and hyoglossus (HG) electromyogram (EMG) activities and respiratory-related tongue movements were compared with peak esophageal pressure (Pes; negative change in pressure during inspiration) and minute Pes (Pes × respiratory frequency = Pes/min) before and after ABs evoked by sustained poikilocapnic, isocapnic, and hypercapnic hypoxia in spontaneously breathing, anesthetized rats. ABs evoked by poikilocapnic and isocapnic hypoxia triggered long-lasting (duration at least 10 respiratory cycles) reductions in GG and HG EMG activities and tongue movements relative to pre-AB levels, but Pes was reduced transiently (duration of 2 to the hypoxic inspirate had no effect on the frequency of evoked ABs, but this prevented long-term declines in tongue muscle activities. Bilateral vagotomy abolished hypoxia-induced ABs and stabilized drive to the tongue muscles during each hypoxic condition. We conclude that, in the rat, hypoxia-evoked ABs 1) elicit long-lasting reductions in protrudor and retractor tongue muscle activities, 2) produce short-term declines in inspiratory pump muscle output, and 3) are mediated by vagal afferents. The more prolonged reductions in pharyngeal airway vs. pump muscle activities may lead to upper airway narrowing or collapse after spontaneous ABs.

The influence of lingual muscle activity on airflow dynamics in the upper airway was examined in nine patients with obstructive sleep apnea. Muscles that retract the tongue (hyoglossus and styloglossus) and protrude the tongue (genioglossus) were selectively stimulated electrically during sleep with fine wire electrodes placed intramuscularly transorally. We confirmed that stimulation with 50 Hz and 40-microseconds pulse duration did not elicit changes in electroencephalographic patterns or heart rate or alter airflow after the stimulation burst had ceased. The highest stimulus intensity that did not arouse patients from sleep was then utilized to examine the effect of lingual muscle recruitment on airflow dynamics during steady-state periods of inspiratory airflow limitation. When applying a stimulus burst during single inspirations, maximal inspiratory airflow decreased by 239 +/- 177 ml/s (P < 0.05) during retractor stimulation, whereas maximal inspiratory airflow increased by 217 +/- 93 ml/s during protrusor stimulation (P < 0.001) compared with breaths immediately before and after the stimulated breath. When consecutive inspirations were stimulated repeatedly, protrusor stimulation decreased the frequency of obstructive breathing episodes in four patients breathing at 3.9 +/- 3.4 (SD) cmH2O nasal pressure. The findings suggest that stimulation of the lingual muscles can increase or decrease airflow depending on the specific muscles stimulated without arousing patients from sleep.

The current T4a subclassification of the TNM staging system for oral malignancies has been criticised as based almost exclusively on anatomical data. The aim of this study was to provide anatomical confirmation of the muscular constraints of T4a classification of oral tongue tumours.A detailed anatomical study describing and measuring the adjacency of the named extrinsic tongue muscles to the lateral tongue surface was completed on the Visible Human Female (VHF). The distance of styloglossus and hyoglossus to the over lying mucosa were determined.The appearance, position, orientation and anatomical relationships of the lateral tongue extrinsic muscles, with comparison to their classical descriptions are described. The right VHF styloglossus was 1.3 mm (0.33-1.48) and left 2.91 mm (0.66-7.68) from the mucosal surface in the axial plane. The right VHF hyoglossus was 2.93 mm (1.48-4.96) and left 4.33 (1.68-8.71) from the mucosal surface in the axial line.In the lateral tongue, styloglossus and hyoglossus are very superficial. The inclusion criteria of hyoglossus and styloglossus in the T4a staging does not appear justified based upon their anatomical position.

The intrinsic lingual neural interconnections are overlooked. It was hypothesized that intralingual anatomically well defined anastomoses interconnect the somatic and autonomic neural systems of the tongue. It was thus aimed to evaluate the intralingual neural scaffold in human tongues. Human tongue samples (ten adult and one pediatric) were microdissected (4.5 magnification). In the interstitium between the genioglossus and hyoglossus muscles, the branches of the lingual nerve (LN) and the medial trunk of the hypoglossal nerve (HN) had a layered disposition of the outer and inner side, respectively, of the lingual artery with its periarterial plexus. Anastomoses of these three distinctive neural suppliers of tongue were recorded, as also were those of the LN with the lateral trunk of the HN and the anastomoses between successive terminal branches of the LN. Successive ansae linguales were joining the LN branches and the medial trunk of the HN. The intrinsic neural system of the tongue supports integrative functions and allows a better retrospective understanding of various experimental studies. The topographical pattern is useful for an accurate diagnosis of intralingual nerves on microscopic slides.

CT scans of 40 patients without pathology in the floor of the mouth or the submandibular glands were reviewed. Intraglandular ducts were visualized in 27 and extraglandular ducts in 3 patients. The CT appearances of dilated submandibular ducts are described in 4 patients with proven causes of obstruction. Widening of the narrow gutter between the mylohyoid and hyoglossus muscles in one scan level is a prominent feature. An intra- or extraglandular duct diameter of 3 mm or more indicates possible obstruction, and the CT images should be scrutinized to reveal the cause.

Summary The aim of this study was to examine whether sectioning of the lateral branches of the hypoglossal nerves (l-XII) in young male rats affects regulation of body weight, food intake and water intake in their period of growth by using a linear fixed effects model or not. Three groups of the rats were prepared according to treatments applied at about 4 weeks after birth to the l-XII innervating the hyoglossus, styloglossus and inferior longitudinal muscles: bilaterally sectioned (n = 9), unilaterally sectioned (n = 3) and sham-operated (n = 6) groups. Changes in body weight, food intake and water intake of the rats in the three groups were measured for 32 days before and after the treatments. To test the abilities of eating and drinking, the amounts of food and water intake were also measured for 1 and 2 min, respectively, after 20 h food and water deprivation at the final stage of the experiment. The major findings obtained were that (i) bilateral sectioning of the l-XII in the young rats significantly reduced body weight and the amount of water, not food, intake consumed and (ii) the bilateral sectioning affected the ability of eating and bilateral and unilateral sectioning affected that of drinking. The results suggest that bilateral sectioning of the lateral branches of XII nerve in young male rats affects regulation of body weight and water intake in their period of growth.

The surgical treatment in early cancers of the lower gingivobuccal (GB) complex involves wide resection of the buccal mucosa and GB sulcus with or without marginal mandibulectomy. To reconstruct this defect we endeavour to describe a method of advancement of the lateral floor of mouth and tongue to provide pliable, vascularised tissue to bridge the mucosal defect and achieve tension free, primary closure whilst preserving maximum tongue mobility and maintaining adequate mouth opening, thus offering an elegant and simple solution to the problems of reconstruction in early lesions of the lower gingivo buccal complex.

In their paper "Evaluating the Structural Properties of Suprahyoid Muscles and their Potential for Moving the Hyoid", Pearson et al. present the results of calculations based upon measurements from anatomical dissections to provide a background for understanding the forces that, potentially, can be generated by selected suprahyoid muscles. As they clearly point out, such results are useful only in the context of specific additional physiological information. What that physiological context is, and how one should interpret their statement that "muscle function is limited by structural data" is not made clear. The information necessary to understand normal, and hence abnormal hyoid movement, is scattered across many papers and a myriad of subdisciplines. The goal of this note is to point to some of the disparate sources of information that are relevant to hyoid movement, including Pearson et al.'s paper, in order generate a better understanding of the wide variety of factors that may affect hyoid movement. Hyoid movement is critical to swallowing, mastication, intraoral transport, vocalization, and respiration. Equally important for some of those behaviors, is non-movement, or stabilization of the hyoid. "Hyoid posture" is the concept that the position of the hyoid and the dynamic maintenance of that position is critical to function. Airway patency or anchoring the base of the tongue for speech or oral function are examples of when constancy of position is critical. Because the hyoid is a "floating bone", and its position is maintained by a sling of muscles, some of which do not articulate with another fixed bone (e.g., middle pharyngeal constrictor, hyoglossus), the limits and capabilities of the hyoid musculature are essential for hyoid posture. The paucity of information on several aspects of hyoid muscle contraction contribute to the difficulty of predicting hyoid behavior from the anatomy of its muscles; one is the lack of basic information on the length-tension and force-velocity characteristics of individual hyoid muscles. For several functions, the anterior and posterior suprahyoid and infrahyoid muscles are active simultaneously (van Lunteren 1987a; van Lunteren and Manubay 1992; Perlman et al. 1999; Thexton et al. 2007; German et al. 2009). Such simultaneous activities of agonist and antagonist muscles is important for stabilization and precise trajectories of movement (Ozkaya and Nordin 1999). Excitation patterns also vary tremendously within the hyoid muscles (Thexton et al. 2007; German et al. 2009; Thexton et al. 2009); multiple fine-wire or micropatch electrodes in geniohyoid and mylohyoid have demonstrated that the patterns of EMG activity not only varied with the specific function (suck, swallow) but also varied with the intramuscular site within the individual muscles. The relationship between EMG activity and muscle strain, or length change, is also complex. The differences in kinematics that result from concentric (muscle shortening), isometric (static length) and eccentric (muscle length increasing) contractions suggest that knowledge of the anatomical properties of a muscle, including its origin, insertion and effective fiber population, are still not sufficient to permit prediction of the movements that result from its activation. Furthermore, it is entirely possible that different portions of a muscle can generate different contraction patterns (Lapatki et al. 2006; Konow et al. 2010). Recent work (Wenzel et al - need cite) also shows that significant regionalization of function exists in geniohyoid and sternohyoid during a simple reflex behavior. While factors, such as fatigue resistance, muscle fiber twitch times and tetanic fusion frequency etc., have been investigated with respect to specific, even isolated, hyoid related muscles in a few species (van Lunteren et al 1987; van Lunteren and Manubay 1992) there is a general lack of such information for the hyoid musculature as a whole and a serious deficiency of information in the case of man. There are also a number of other considerations that have yet to be adequately investigated, such as elasticity and hysteresis in the hyoid musculature and the extent to which successive positions of the hyoid are determined by passive equilibria or actively by positional sensory feedback to motoneurons; the investigation of the latter is complicated by the apparent paucity and uncertain nature of the sensory receptors in those muscles. At the very least, in order to gain a very basic understanding of hyoid movement, the EMG and kinetic activity of the sets of agonist and antagonist muscles, such as geniohyoid, mylohyoid, sternohyoid and stylohyoid should be considered simultaneously with cranio-cervical posture. Such studies may be problematic in man. There is also a potential problem in interpreting EMG activity, recorded from hyoid muscles in humans, using conventional surface electrodes. Conventional electrodes detect signals from a volume that is likely to contain not only different hyoid muscles but different motor unit populations within those muscles. The functional heterogeneity, that has already been identified among the motor units of hyoid muscles by other methods ((Tsuiki 2000; van Lunteren and Dick 2001; Thexton et al. 2007; Konow et al. 2010) consequently be unlikely to be detected, If the goal of a study was to detect, within an EMG recording, signs of a particular neurological deficit, such conventional surface electrode recording methods could mask the specifics of that pathophysiology. Pearson et al conclude that the geniohyoid "has the most potential to displace the hyoid in an anterior direction" but do acknowledge that additional information on “fiber types, passive forces …‥ and motor units recruited for a specific task …… are essential to understanding function”. The lack of information on the level of recruitment of geniohyoid motor units to move the hyoid forward does, however, tend to undermine the use of physiological cross sectional area (PCSA) as a predictor of forward pull on the hyoid although the PCSA may well indicate the upper limit of that pull. Before firm conclusions can be drawn, it is necessary to obtain detailed in vivo data both on the hyoid kinematics and on the distribution of the intramuscular electromyographic activity simultaneously within the individual muscles that make up the three-way lines of action on the hyoid.

Whether electrical microstimulation of a rat’s striatal jaw region (SJR) in fact induced tongue or facial muscle activity in addition to jaw muscle activity was tested. Microstimulation of SJR-evoked EMG activity in a jaw-opener (anterior digastricus) and tongue-protruder (genioglossus). No activity was evoked in jaw-closers (temporalis or masseter), tongue-retractor (hyoglossus) or in facial muscles. In addition, the EMG effect could still be induced after extensive ablation of the neocortex; it was reproduced by microinjection of 50 mM kainic acid into SJR. The effective sites were histologically localized to a small central striatal region adjoining the anterior commissure. These findings may be of considerable value in understanding the striatal mechanism of orolingual dyskinesia involving involuntary jaw and tongue movements.

The influence of systemic hypoxia on the endurance performance of tongue protrudor and retractor muscles was examined in anesthetized, ventilated rats. Tongue protrudor (genioglossus) or retractor (hyoglossus and styloglossus) muscles were activated via medial or lateral XII nerve branch stimulation (0.1-ms pulse; 40 Hz; 330-ms trains; 1 train/s). Maximal evoked potentials (M waves) of genioglossus and hyoglossus were monitored with electromyography. Fatigue tests were performed under normoxic and hypoxic (arterial[Formula: see text] = 50 ± 1 Torr) conditions in separate animals. The fatigue index (FI; %initial force) after 5 min of normoxic stimulation was 85 ± 6 and 79 ± 7% for tongue protrudor and retractor muscles, respectively; these values were significantly lower during hypoxia (protrudor FI = 52 ± 10, retractor FI = 18 ± 6%; P < 0.05). Protrudor and retractor muscle M-wave amplitude declined over the course of the hypoxic fatigue test but did not change during normoxia ( P < 0.05). We conclude that hypoxia attenuates tongue protrudor and retractor muscle endurance performance; potential mechanisms include neuromuscular transmission failure and/or diminished sarcolemmal excitability.

It is well established that the genioglossus muscle (tongue protrudor) has a role in protecting or enhancing upper airway patency in individuals with obstructive sleep apnea. However, no investigation completed to date has addressed the role of the styloglossus and hyoglossus muscles (tongue retractors) in maintaining upper airway patency in humans. As a first step toward this goal, the present investigation was designed to examine the response of human tongue protrudor and retractor muscles during a breathhold maneuver and in steady-state hypoxic hypercapnia. The results showed that the protrudor and retractor muscles were coactivated under both conditions. Measurements of onset time of electromyographic activity during steady-state hypoxic hypercapnia revealed that phasic protrudor and retractor activity was initiated immediately before or during the early part of inspiration. We conclude that the tongue protrudor and retractor muscles are coactivated in response to hypoxia and hypercapnia, and that the tongue retractors may have a significant role in protecting upper airway patency during both apnea and hyperpnea.

1. The purpose of these experiments was to examine the mechanisms by which either co-activation or independent activation of tongue protrudor and retractor muscles influence upper airway flow mechanics. We studied the influence of selective hypoglossal (XIIth) nerve stimulation on tongue movements and flow mechanics in anaesthetized rats that were prepared with an isolated upper airway. In this preparation, both nasal and oral flow pathways are available. 2. Inspiratory flow limitation was achieved by rapidly lowering hypopharyngeal pressure (Php) with a vacuum pump, and the maximal rate of flow (VI,max) and the nasopharyngeal pressure associated with flow limitation (Pcrit) were measured. These experimental trials were repeated while nerve branches innervating tongue protrudor (genioglossus; medial XIIth nerve branch) and retractor (hyoglossus and styloglossus; lateral XIIth nerve branch) muscles were stimulated either simultaneously or independently at frequencies ranging from 20-100 Hz. Co-activating the protrudor and retractor muscles produced tongue retraction, whereas independently activating the genioglossus resulted in tongue protrusion. 3. Co-activation of tongue protrudor and retractor muscles increased VI, max (peak increase 44 %, P < 0.05), made Pcrit more negative (peak decrease of 44 %, P < 0.05), and did not change upstream nasopharyngeal resistance (Rn). Independent protrudor muscle stimulation increased VI,max (peak increase 61 %, P < 0.05), did not change Pcrit, and decreased Rn (peak decrease of 41 %, P < 0.05). Independent retractor muscle stimulation did not significantly alter flow mechanics. Changes in Pcrit and VI,max at all stimulation frequencies were significantly correlated during co-activation of protrudor and retractor muscles (r2 = 0.63, P < 0.05), but not during independent protrudor muscle stimulation (r2 = 0.09). 4. These findings indicate that either co-activation of protrudor and retractor muscles or independent activation of protrudor muscles can improve upper airway flow mechanics, although the underlying mechanisms are different. We suggest that co-activation decreases pharyngeal collapsibility but does not dilate the pharyngeal airway. In contrast, unopposed tongue protrusion dilates the oropharynx, but has a minimal effect on pharyngeal airway collapsibility.