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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.

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

Three hypothetical models of tongue movement of the walrus during suction feeding are examined. These models encompass the entire range of simple tongue retraction movements possible by examining 1) movement of the tongue directly to the rear following the curvature of the palate, 2) to the rear and ventrally in a straight line, and 3) ventrally in a straight line. The percent of muscular force available from the hyoglossus, genioglossus, and styloglossus that could be applied toward retraction as predicted by each model is calculated. The resistance that the tongue would provide during retraction is calculated using projected tongue areas and is combined with the above data from the muscles to provide an estimate of the percent of the total available force that is needed to retract the tongue for each model. A separate examination of the direction of tongue-induced wear striations on the palatal and lingual aspects of the teeth is used to help support or reject the three models. The model where the tongue is moved directly to the rear is supported by studies of both muscle force and tooth wear. In the mammalian groups that were compared to the walrus, there is a great deal of interspecific variation in movements of the tongue during suction feeding; no two groups can be considered to have identical stereotyped tongue movements.

Tongue musculature in 24 genera of snakes was examined histologically. In all snakes, the tongue is composed of a few main groups of muscles. The M. hyoglossus is a paired bundle in the center of the tongue. The posterior regions of the tongue possess musculature that surrounds these bundles and is responsible for protrusion. Anterior tongue regions contain hyoglossal bundles, dorsal longitudinal muscle bundles and vertical and transverse bundles, which are perpendicular to the long axis of the tongue. The interaction of the longitudinal with the vertical and horizontal muscles is responsible for bending during tongue flicking. Despite general similarities, distinct patterns of intrinsic tongue musculature characterize each infraorder of snakes. The Henophidia are primitive; the Scolecophidia and Caenophidia are each distinguished by derived characters. These derived characters support hypotheses that these latter taxa are each monophyletic. Cylindrophis (Anilioidea) is in some characters intermediate between Booidea and Colubroidea. The condition in the Booidea resembles the lizard condition; however, no synapomorphies of tongue musculature confirm a relationship with any specific lizard family. Although the pattern of colubroids appears to be the most biomechanically specialized, as yet no behavioral or performance feature has been identified to distinguish them from other snakes.

Prey capture in Agama stellio was recorded by high-speed video in combination with the electrical activity of both jaw and hyolingual muscles. Quantification of kinematics and muscle activity patterns facilitated their correlation during kinematic phases. Changes in angular velocity of the gape let the strike be subdivided into four kinematic phases: slow open (SO1 and SOII), fast open (FO), fast close (FC), and slow close-power stroke (SC/PS). The SO1 phase is marked by initial activity in the tongue protractor, the hyoid protractor, and the ring muscle. These muscles project the tongue beyond the anterior margin of the jaw. During the SO11 phase, a low level of activity in the jaw closers correlates with a decline of the jaw-opening velocity. Next, bilateral activity in the jaw openers defines the start of the FO phase. This activity ends at maximal gape. Simultaneously, the hyoid retractor and the hyoglossus become active, causing tongue retraction during the FO phase. At maximal gape, the jaw closers contract simultaneously, initiating the FC phase. After a short pause, they contract again and the prey is crushed during the SC/PS phase. Our results support the hypothesis of tongue projection in agamids by Smith (( 19881 J. Morphol. 196:157-171), and show some striking similarities with muscle activity patterns during the strike in chameleons (Wainwright and Bennett ( 1992al J. Exp. Biol. 168:l-21). Differences are in the activation pattern of the hyoglossus. The agamid tongue projection mechanism appears to be an ideal mechanical precursor for the ballistic tongue projection mechanism of chameleonids; the key derived feature in the chameleon tongue projection mechanism most likely lies in the changed motor pattern controlling the hyoglossus muscle. B 1995 Wiley-Liss, Inc. Lizards capture prey by means of lingual or jaw prehension (Smith, '84, '88). Some authors argue that jaw-mediated prey cap- ture might be the primitive condition in squa- mates (Bels and Goosse, '90; referring to the plesiomorphic condition of jaw prehension in Amphibia, Thexton et al., '77; Lauder and ShafTer, '88; Findeis and Bemis, '90; Nishi- kawa and Cannatella, '91; Anderson, '931, but lingual prey capture is considered by most authors to be more primitive than jaw capture (Schwenk, '88; Schwenk and Bell, '88; Schwenk and Throckmorton, '89). Most functional morphological studies con- cerning prey capture in lizards have empha- sized a few groups belonging to the Iguania (Agamidae: Schwenk and Throckmorton, '89; Kraklau, '91; Iguanidae: Schwenk and Throckmorton, '89; Bels, '90; Bels and Go- osse, '90; Delheusy and Bels, '92; and Cha- maeleonidae: Gnanamuthu, '30; Zoond, '33; Bels and Baltus, '87; Bell, '89, '90; Wain

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.

Little is known about the anatomy and musculature of the gray whale (Eschrichtius robustus), especially related to the anatomy of the tongue and hyoid region. The recovery of an extremely fresh head of a neonatal female gray whale provided an opportunity to conduct the first in-depth investigation of the musculoskeletal features of the tongue and hyoid apparatus. Unlike other mysticetes, the gray whale tongue is strong, muscular, and freely mobile inside the buccal cavity. In particular, the genioglossus and hyoglossus muscles are extremely large and robust making up the majority of the body of the tongue. In addition, the genioglossus had a unique position and fiber orientation in the tongue compared to other mammals. The structure of the hyoid apparatus differs between E. robustus and other mysticete species, although there are similarities among individual elements. We provide the first documentation of fungiform papillae that may be associated with taste buds in Mysticeti. The highly mobile, robust tongue and the presence of well-defined tongue and hyoid musculature are in keeping with observations of gray whale feeding that suggest this group of whales utilize oral suction to draw benthic prey into the buccal cavity. Anat Rec, 298:660–674, 2015. © 2014 Wiley Periodicals, Inc.

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.

The hypoglossal or twelfth cranial nerve is the motor nerve to the extrinsic and intrinsic muscles of the tongue, and the superior root of the ansa cervicalis and the thyrohyoid and geniohyoid branches are delivered through the nerve. This study investigated the muscular branches of the hypoglossal nerve to clarify their spatial relationships with the muscles of the tongue and the neighboring structures. The muscles and the nerve were gross anatomically examined in 42 cadavers. The superior root and the thyrohyoid branch left the nerve near the occipital and lingual arteries, respectively. The extrinsic muscles consisted of some components, and the geniohyoid branch and the lingual branches arose on the hyoglossus. The ascending lingual branches formed a plexus on the anterior part of the hyoglossus and were divided into the proximal and distal groups. They supplied the two parts of the hyoglossus, the three bundles of the styloglossus and the superior and inferior longitudinal muscles and communicated with the lingual nerve. The descending lingual branches supplied the inferior part of the genioglossus, and the terminal branches gave intramuscular twigs to its main part and the transverse and vertical muscles. The findings indicated that the branching pattern of the hypoglossal nerve is characterized by the positional relationships to the components of the extrinsic muscles. The hyoid bone can be an effective marker to identify the branches and affected position if it was used in combination with the morphology of the extrinsic muscles, and the knowledge of their variations is also beneficial. Anat Rec, 302:558-567, 2019. © 2018 Wiley Periodicals, Inc.

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.

This work was carried out on the heads of sixteen apparently healthy adult domestic cats of various sex- es. The available literatures dealing with the gross anatomy of the hyoid apparatus of various species of domestic animals were reviewed. The Manual dissection, dry bony specimens as well as histological exami- nation were used according to the purpose under investigation. The study described the six segments forming the cat hyoid apparatus; Tympanohyoideum, Stylohyoide- um, Epihyoideum, Ceratohyoideum, Basihyoideum and Thyrohyoideum.Elevenpairs of muscles where attached to the hyoid apparatus. The most enlarged of these muscles were those that retract the hyoid bone caudally, the sternohyoid muscle and rostrally, the geniohyoid muscle as well as those controlling the tongue movement, styloglossus and hyoglossus. The histological studies showed that the Tympano-hyoideum and Ceratohyoideum were mostly hyaline cartilage, the Epihyoideum was partly hyaline and partly fibrous, the Stylohyoideum and Thyrohyoideum were partly hyaline and partly osseous while the Basihyoideum was completely ossified. The results obtained were photographed, described and discussed with those of other domestic animals.

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.

This study reports an investigation of the well-known context-dependent variation in English /r/ using a biomechanical tongue-jaw-hyoid model. The simulation results show that preferred /r/ variants require less volume displacement, relative strain, and relative muscle stress than variants that are not preferred. This study also uncovers a previously unknown mechanism in tongue biomechanics for /r/ production: Torque in the sagittal plane about the mental spine. This torque enables raising of the tongue anterior for retroflexed [Symbol: see text] by activation of hyoglossus and relaxation of anterior genioglossus. The results provide a deeper understanding of the articulatory factors that govern contextual phonetic variation.

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.

UNLABELLED With 8 figures SUMMARY This study aimed at revealing the origin, course and distribution of the hypoglossal nerve in 20 adult male New Zealand rabbits. In all the animals dissected, the hypoglossal nerve arose from the ventrolateral side of the medulla oblongata with two main roots and gave off a descending branch to the ansa cervicalis before reaching the division of the common carotid artery. This branch was not seen on the right side of only one case. At the lateral aspect of the hyoglossus muscle, the nerve then divided into the lateral and medial main branches, sent branches to the styloglossus, hyoglossus, genioglossus and geniohyoideus muscles and terminated in the intrinsic tongue muscles. A communicating branch was observed between the hypoglossal and accessory nerves in the right side of one animal and between the hypoglossal nerve and the ganglion nodosum in the right retropharyngeal area of another animal. An additional branch was observed innervating the stylohyoideus muscle in one animal only. A lateral lingual-hypoglossal communication was also seen between the lateral branch of the hypoglossal nerve and terminal branches of the lingual nerve.

The respiratory central pattern generator distributes rhythmic excitatory input to phrenic, intercostal, and hypoglossal premotor neurons. The degree to which this input shapes motor neuron activity can vary across respiratory muscles and motor neuron pools. We evaluated the extent to which respiratory drive synchronizes the activation of motor unit pairs in tongue (genioglossus, hyoglossus) and chest-wall (diaphragm, external intercostals) muscles using coherence analysis. This is a frequency domain technique, which characterizes the frequency and relative strength of neural inputs that are common to each of the recorded motor units. We also examined coherence across the two tongue muscles, as our previous work shows that, despite being antagonists, they are strongly coactivated during the inspiratory phase, suggesting that excitatory input from the premotor neurons is distributed broadly throughout the hypoglossal motoneuron pool. All motor unit pairs showed highly correlated activity in the low-frequency range (1–8 Hz), reflecting the fundamental respiratory frequency and its harmonics. Coherence of motor unit pairs recorded either within or across the tongue muscles was similar, consistent with broadly distributed premotor input to the hypoglossal motoneuron pool. Interestingly, motor units from diaphragm and external intercostal muscles showed significantly higher coherence across the 10–20-Hz bandwidth than tongue-muscle units. We propose that the lower coherence in tongue-muscle motor units over this range reflects a larger constellation of presynaptic inputs, which collectively lead to a reduction in the coherence between hypoglossal motoneurons in this frequency band. This, in turn, may reflect the relative simplicity of the respiratory drive to the diaphragm and intercostal muscles, compared with the greater diversity of functions fulfilled by muscles of the tongue.

SUMMARYA combination of dissection and computed tomography scanning has provided significant novel insights into the structure and function of the Dermochelys coriacea larynx and its associated muscles. Several previously unknown features of the laryngeal aditus (glottis) are described and their functional significance in its opening and closure are considered. The tongue plays an essential part in producing and maintaining closure during dives and feeding bouts. Closure is brought about by compression of the glottis under the action of the two hyoglossus muscles. The tongue thus plays the role of the epiglottis of mammals, sealing the entrance to the larynx. As is already clear, opening is brought about by abduction of the arytenoid cartilages. In addition, there is a powerful mechanism for maintaining the larynx in close apposition to the hyoid plate during feeding and neck flexion, thereby enhancing the efficiency of feeding.

Obstruction of the upper airway (UA) is associated with episodes of hypoxia and upper airway negative pressure (UANP). In the companion paper it is shown that episodic hypoxia elicits long-term facilitation (LTF) of tongue protrudor, retractor and respiratory pump muscle activity. However, whether repeated exposure to UANP also induces LTF is unknown. We hypothesized that repetitive exposure to UANP would induce LTF of UA and respiratory pump muscle activity and when coupled with hypoxia, as occurs when the UA obstructs, would lead to an even greater facilitation of muscle activity and the response to UANP. Experiments were performed in 24 anaesthetized, spontaneously breathing rats with intact vagi. To induce LTF, UANP stimuli (−10 cmH2O) of 5 s duration were delivered every 30 s for 3 min (± hypoxia). This was repeated eight times over 1 h, each 3 min episode separated by 5 min of normoxia. Genioglossus (GG), hyoglossus (HG) and diaphragm (Dia) muscle activity was recorded before, during and for 1 h following the last exposure to episodic UANP alone (n= 8), UANP and hypoxia together (n= 8) or normoxia alone (n= 8). During the final hour, single pulses of UANP were applied at 1 min and every 10 min thereafter to determine whether LTF of the response to UANP had been induced. Our results show that LTF of GG muscle activity and its response to UANP was induced following exposure to episodic UANP stimuli alone and UANP applied during hypoxia. However, there was no significant difference between these responses. Episodic UANP alone also induced LTF of HG muscle activity but this effect did not manifest until 40 min following the last episode of repeated UANP stimulation. In the presence of hypoxia, no LTF of HG muscle response to UANP was found. In conclusion, episodic UANP stimulation induces LTF of UA dilator and retractor tongue muscles, but no further facilitation occurs when coupled with hypoxia. This response may serve as an important protective mechanism of respiratory homeostasis during sleep, particularly in patients who suffer from obstructive sleep apnoea.

We performed these experiments to determine if repeated exposure to episodic hypoxia induces long term facilitation (LTF) in anaesthetized spontaneously breathing rats. A previous study in spontaneously breathing rats was unable to demonstrate evidence of LTF with repeated hypoxia, but this may have been due to the low number of hypoxic episodes used. We hypothesized that with sufficient exposure, episodic hypoxia LTF of genioglossus (GG), hyoglossus (HG) and diaphragm (Dia) activities would be elicited. Experiments were performed in 24 anaesthetized spontaneously breathing rats with intact vagi. Peak and tonic GG, HG and Dia EMG activities were recorded before, during and for 1 h following exposure to eight (n= 8) or three (n= 8) episodes of isocapnic hypoxia (= 0.1) each of 3 min duration. A third time control series was also performed with exposure to normoxia alone (= 0.28, n= 8). Short-term potentiation of GG and HG muscle activity developed during the early period after repeated exposure to eight and three hypoxic episodes. LTF, however, occurred only after eight hypoxic episodes. This manifested as an increase in peak GG and Dia inspiratory muscle activity and tonic HG activity. LTF of respiratory breathing frequency was also induced, reflected by a reduction in inspiratory and expiratory time. These findings support our initial hypothesis that LTF in the anaesthetized, spontaneously breathing rat is dependent on the number of exposures to hypoxia and show that the responses to repetitive hypoxia are composed of both short and long-term facilitatory changes.

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.