Hyoglossus Research Articles

Anatomic variation of cranial parasympathetic ganglia

Having broad knowledge of anatomy is essential for practicing dentistry. Certain anatomical structures call for detailed studies due to their anatomical and functional importance. Nevertheless, some structures are difficult to visualize and identify due to their small volume and complicated access. Such is the case of the parasympathetic ganglia located in the cranial part of the autonomic nervous system, which include: the ciliary ganglion (located deeply in the orbit, laterally to the optic nerve), the pterygopalatine ganglion (located in the pterygopalatine fossa), the submandibular ganglion (located laterally to the hyoglossus muscle, below the lingual nerve), and the otic ganglion (located medially to the mandibular nerve, right beneath the oval foramen). The aim of this study was to present these structures in dissected anatomic specimens and perform a comparative analysis regarding location and morphology. The proximity of the ganglia and associated nerves were also analyzed, as well as the number and volume of fibers connected to them. Human heads were dissected by planes, partially removing the adjacent structures to the point we could reach the parasympathetic ganglia. With this study, we concluded that there was no significant variation regarding the location of the studied ganglia. Morphologically, our observations concur with previous classical descriptions of the parasympathetic ganglia, but we observed variations regarding the proximity of the otic ganglion to the mandibular nerve. We also observed that there were variations regarding the number and volume of fiber bundles connected to the submandibular, otic, and pterygopalatine ganglia.

Effect of coactivation of tongue protrusor and retractor muscles on pharyngeal lumen and airflow in sleep apnea patients

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 cmH(2)O, but coactivation lowered Pcrit to 0.2 +/- 1.9 cmH(2)O (P < 0.01 for both). In the AnS, intramuscular stimulation of GG lowered Pcrit from 2.6 +/- 1.3 to 1.0 +/- 2.8 cmH(2)O, HG increased Pcrit to 6.2 +/- 2.5 cmH(2)O (P < 0.01), and coactivation had a similar effect to that of GG (Pcrit = 1.2 +/- 2.4 cmH(2)O, 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.

A case of epidermoid cyst arising between the submandibular gland and the platysma

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.

Hemorrhage in the Floor of the Mouth After Second-Stage Surgery: Case Report

Placement of dental implants in the interforaminal region of the mandible is generally considered a routine, simple, and safe procedure. However, severe bleeding and hematoma in the floor of the mouth have been reported as a rare but potentially fatal complication related to the placement of an implant in this region. The following report describes a case of life-threatening hemorrhage in the floor of the mouth after second-stage surgery to place the healing abutment. The implants were forced to match with the prosthesis in a severely atrophic upper jaw, resulting in a perforation of the lingual cortex and mucosa of the floor of the mouth. Clinicians who place implants should be knowledgeable in the treatment of such a serious complication.

Myosin heavy chain and fibre diameter of extrinsic tongue muscles in rhesus monkey

The purpose of this investigation was to identify the myosin heavy chain (MHC) phenotype and fibre diameters of hypoglossal innervated extrinsic tongue muscles in rhesus monkey. Genioglossus, styloglossus and hyoglossus muscle samples obtained from three female rhesus monkeys were analysed for MHC isoforms via gel electrophoresis and stained with MHC antibodies to measure least mean diameters. MHC phenotypes were consistent for all three muscles. Each muscle was predominantly composed of MHC type IIa and I. All three isoforms were significantly different from each other in fibre diameter for styloglossus and genioglossus (IIb>IIa and IIx>I; P<0.001). For hyoglossus, the MHC type II isoforms had larger diameters than the MHC type I isoform (P<0.001). While the extrinsic tongue muscle MHC and/or muscle fibre type composition may be different between mammalian species, there are consistent similarities between the intrinsic and extrinsic tongue muscles. We suggest this is necessary for the highly coordinated activities performed by the tongue such as mastication, respiration and swallowing. The differences in fibre diameters among MHC isoforms suggest a large force gradation, which would be consistent with the coordination of these activities. The similarities among primates in MHC and/or muscle fibre composition as well as similar cortical inputs to the hypoglossal nucleus, suggest that we could expect to see similar MHC phenotype for extrinsic tongue muscles in human.

How the pharyngeal resonator is controlled articulatorily

Indigenous languages of North America, especially west coast Vancouver Island Nuuchahnulth and Interior BC Salish, illustrate an extensive range of use of the pharyngeal resonator. The pharynx is classified as part of the laryngeal articulator (rather than lingual) because the laryngeal constrictor mechanism (controlling changes from the glottis to the aryepiglottic folds) is the principal articulator whose movements determine the shape of the pharynx. The Nuuchahnulth (Nootka) dialects (e.g., Ahousaht) and Thompson, Moses-Columbia, and Spokane/Kalispel Salish varieties all close the larynx completely for the speech sound epiglottal stop. With the airway optimally shut, the pharynx is small; the aryepiglottic folds are pressed against the epiglottic tubercle, the tongue is retracted, and the larynx is raised. There are good indications that the thyroarytenoid, aryepiglottic, thyroepiglottic, hyoglossus and hyothyroid muscles participate in this buckling maneuvre. These languages also contain either a pharyngeal fricative or approximant (at the same place of articulation but with less stricture) and, in Thompson, also pharyngealized uvulars (with even less stricture). Pharyngeal resonance in all of these cases is dependent initially on the shortening of the supraglottic tube and subsequently on the combined effect of tongue retraction and larynx raising reducing the volume immediately above the supraglottic tube.

Postnatal development of hypoglossal motoneurons that innervate the hyoglossus and styloglossus muscles in rat

Postnatal development of hyoglossus and styloglossus motoneurons was studied in this investigation of the hypoglossal nucleus. Our findings show separate and distinct locations for hyoglossus and styloglossus motoneurons within the retrusor (dorsal) subdivision of the hypoglossal nucleus for all age groups. Hyoglossus and styloglossus motoneuron cross-sectional area reached their adult size at different times (by weeks 2 and 3, respectively). Cell roundness, as measured by form factor (measure of cell perimeter relative to its area), decreased with advancing postnatal age for both populations of motoneurons. Differences in the direction of the dendritic projection between hyoglossus and styloglossus motoneurons were found. Hyoglossus and styloglossus motoneuron development was compared to genioglossus motoneuron postnatal development.

Ear pain in patients with oropharynx carcinoma: how MRI contributes to the explanation of a prognostic and predictive symptom.

Reflex otalgia is a predictive and prognostic parameter for local control in patients with oropharynx carcinoma. Can a morphologic correlate of this important symptom be detected by MRI? Thirty-six patients were prospectively evaluated by MRI before radical radiotherapy. Sixteen patients had reflex otalgia; 20 did not. The oropharynx and adjacent regions were analyzed. Alteration was defined as effacement of anatomical structures, signal alteration or enhancement after contrast medium administration. The chi(2)-test was used to compare categorical parameters. In patients with reflex otalgia, alteration of the following structures innervated by the glossopharyngeal nerve were found significantly more often: nasopharynx, hard palate, superior constrictor pharyngis muscle, palatine tonsil, palatopharyngeus muscle, palatoglossus muscle, stylopharyngeus muscle, hyoglossus muscle and preepiglottic space. No difference was found for the muscles of mastication, levator and tensor veli palatini muscles, styloglossus muscle, genioglossus muscle, intrinsic muscles of the tongue, digastric muscles, mucosal surface of the lateral and posterior pharyngeal wall, uvula, valleculae, parapharyngeal space and larynx. An alteration of structures innervated by the glossopharyngeal nerve was visualized on MRI significantly more often when reflex otalgia was present. Involvement of structures innervated by other cranial nerves did not show the same association with ear pain.

Morphological study of the human chondroglossus muscle in Japanese

The chondroglossus muscle was macroscopically studied to clarify its fundamental morphology. This muscle was present in all of the 100 tongue halves examined in Japanese cadavers. In 14% of the specimens, however, the muscular fibers were sparse and vestigial. Originating mainly from the medial side of the lesser cornu of the hyoid bone, the chondroglossus muscle passed upward to penetrate the inferior longitudinal muscle of the tongue, and immediately entered the genioglossus muscle. Ascending inside the genioglossus muscle, it's bundles spread, taking a broom head or a fan-like shape. Thereafter it reached the submucosal layer in the root of the tongue, changed the direction from upward to forward, and terminated diffusely, never going past the sulcus terminalis. The origin, course, and spreading manner of the chondroglossus muscle were quite different from those of the hyoglossus muscle. The nerve fiber supplying the chondroglossus muscle was a ramus from the first lateral branch of the hypoglossal nerve. It should be considered a separate extrinsic lingual muscle independent of the hyoglossus muscle, although they have a phylogenetically close relationship.

Effect of pulmonary stretch receptor feedback and CO(2) on upper airway and respiratory pump muscle activity in the rat.

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.

Consequences of periodic augmented breaths on tongue muscle activities in hypoxic rats.

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 x 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 <10 respiratory cycles) after ABs. Adding 7% CO(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.

Response of human tongue protrudor and retractors to hypoxia and hypercapnia.

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.

Biomechanical basis for lingual muscular deformation during swallowing.

Our goal was to quantify intramural mechanics in the tongue through an assessment of local strain during the physiological phases of swallowing. Subjects were imaged with an ultrafast gradient echo magnetic resonance imaging (MRI) pulse sequence after the application of supersaturated magnetized bands in the x and y directions. Local strain was defined through deformation of discrete triangular elements defined by these bands and was depicted graphically either as color-coded two-dimensional strain maps or as three-dimensional octahedra whose axes correspond to the principal strains for each element. During early accommodation, the anterior tongue showed positive strain (expansive) in the anterior-posterior direction (x), whereas the middle tongue showed negative strain (contractile) in the superior-inferior direction (y). During late accommodation, the anterior tongue displayed increased positive x-direction and y-direction strain, whereas the posterior tongue displayed increased negative y-direction strain. These findings were consistent with contraction of the anterior-located intrinsic muscles and the posterior-located genioglossus and hyoglossus muscles. During propulsion, posterior displacement of the tongue was principally associated with positive strain directed in the x and y directions. These findings were consistent with posterior passive stretch in the midline due to contraction of the laterally inserted styloglossus muscle, as well as contraction of the posterior located transversus muscle. We conclude that MRI of lingual deformation during swallowing resolves the synergistic contractions of the intrinsic and extrinsic muscle groups.

Respiratory-related control of extrinsic tongue muscle activity

The purpose of this brief report is to introduce new evidence showing that the protrudor and retractor muscles of the tongue are co-activated during inspiration in eupnea and hyperpnea in an anesthetized, tracheotomized rat model. We also review previous work on the respiratory related control of the tongue musculature, and briefly consider the clinical significance of this work. The important new findings are that: (1) Both hypoxia and hypercapnia cause parallel increases in drive to the tongue protrudor and retractor muscles (the genioglossus and hyoglossus muscles, respectively); (2) phasic volume feedback inhibits the peak inspiratory activity of both muscles; and (3) the tongue muscles consistently produce a retraction force when the genioglossus and hyoglossus are co-activated, in both animal and human subjects. This latter observation is consistent with previous work showing that the retractor muscles (hyoglossus and styloglossus) develop up to ten times more force than the genioglossus muscle. The possible mechanical consequences of tongue muscle co-activation are briefly considered.

Compartmental organization of styloglossus and hyoglossus motoneurons in the hypoglossal nucleus of the rat

Surgical techniques were used to isolate the extrinsic bellies of the styloglossus and hyoglossus muscles from the body of the tongue for cholera toxin HRP injection. An average of 53 styloglossus and 121 hyoglossus motoneurons in the dorsal subdivision of the hypoglossal nucleus were demonstrated using tetramethyl benzidine histochemistry. Styloglossus motoneurons were restricted to the rostral 25% of the nucleus while hyoglossus motoneurons occupied other regions of the dorsal nucleus.

The kinematics and mechanism of prey capture in the African pig-nosed frog (Hemisus marmoratum): description of a radically divergent anuran tongue.

High-speed videography and muscle denervation experiments were used to quantify the feeding kinematics of Hemisus marmoratum and to test hypotheses of muscle function. The feeding behavior of H. marmoratum, which feeds on ants and termites, differs radically from that of other frogs that have been studied. During feeding in H. marmoratum, the tongue 'telescopes' straight out of the mouth, as opposed to the 'flipping' tongue trajectory observed in most other frogs. At the time of prey contact, two lateral lobes of tissue at the tongue tip envelop the prey. These lateral lobes are capable of applying significant pulling forces to the prey and the tongue is, therefore, described as prehensile. The trajectory of the tongue can be adjusted throughout protraction so that the frog can 'aim' its tongue in all three dimensions; distance, azimuth and elevation. Bilateral denervation of the genioglossus muscles results in a complete lack of tongue protraction, indicating that the genioglossus muscle is the main tongue protractor in H. marmoratum, as in other frogs. Thus, H. marmoratum provides strong evidence of functional conservatism of the genioglossus muscle within anurans. Bilateral denervation of the hyoglossus muscle indicates that although the hyoglossus is involved in several aspects of normal tongue retraction, including the prehensile capability of the tongue tip, it is not necessary for tongue retraction. Unilateral denervation of the genioglossus muscle causes significant deviation of the tongue towards the denervated side, providing evidence for a mechanism of lateral tongue aiming. On the basis of the kinematics of prey capture, the anatomy of the tongue and the results of the denervation experiments, we propose that H. marmoratum uses a hydraulic mechanism to protract its tongue.

Prey capture in the lizard Agama stellio.

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 (SOI and SOII), fast open (FO), fast close (FC), and slow close-power stroke (SC/PS). The SOI 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 SOII 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 ([1988] J. Morphol. 196:157-171), and show some striking similarities with muscle activity patterns during the strike in chameleons (Wainwright and Bennett [1992a] J. Exp. Biol. 168:1-21). 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. © 1995 Wiley-Liss, Inc.

Olfactory influence on tongue activity.

Recent findings have shown that olfactory stimulation by brief puffs of air odorized with amyl acetate induces several patterns of response in rabbit hypoglossal neurons. It has been argued that the functional role of the olfactory input may be the modulation of tongue muscular tone during the oral phase of digestion. In the present research, the peripheral effect of olfactory-hypoglossal modulation was analyzed. Both the spike traffic along the fibers of the hypoglossal nerve and the electromyographic activity of single tongue muscles (genioglossus, styloglossus, superior longitudinal and hyoglossus) were recorded before, during and after olfactory stimulation. Results showed that brief puffs of air odorized with amyl acetate induced a significant change in the efferent volleys along the hypoglossal nerve, as well as a substantial modulation of tongue muscle activity. Olfactory stimulation induced a significant increase in the spontaneous activity of both type I and type II genioglossal fibers; excitation followed by inhibition both in tonic and phasic styloglossal fibers; excitatory responses in tonic and phasic superior longitudinal fibers and short-lasting excitatory responses in the hyoglossal fibers. The diverse patterns of activation of the tested muscle and the significant differences between fibers, tonically or phasically controlled by the XIIth neurons, indicate that olfaction may be strongly involved in tongue reflex regulation. Different functional hypothesis are discussed about the role played by olfaction in the economy of tongue muscle activity.

Role of water receptor in the frog

To elucidate the role of the water receptor in the frog (Rana catesbeiana), reflex activities elicited by its excitation were studied. Application of tap water to the oral mucosa depressed the rhythmical movement of gorge (buccal) respiration, accompanied by an elevation of the inner pressure of the oral cavity (buccal pressure). Tonic reflex discharges were elicited in the nerves innervating the submental and submaxillary muscles, which close the nostrils, the pterygoid and the profound portion of the major masseter muscles, which produce a strong bite, and the geniohyoid and hyoglossus muscles, which elevate buccal pressure. These muscles, except for the pterygoid, also participate in the rhythmical movement of gorge respiration as expiratory muscles. Rhythmical movements in the minor masseter and sternohyoid muscles, which act as inspiratory muscles in gorge respiration, were depressed by the water stimulation of the oral mucosa. These findings indicate that the water receptor plays a role in the interruption of gorge respiratory movements, accompanied by an elevation of buccal pressure.

The articulatory trajectories of the tongue in the muscle force space

The motor command generation mechanism for speech production may be considered as a transformation from a planned articulatory trajectory to multiple motor commands. This study aims to reconstruct a representation of such a trajectory by analyzing EMG signals associated with tongue movements in speech. Tongue EMG data recorded during /schwapVp/ utterances [Baer etal., Ann. Bull. RILP 22, 7–20] were analyzed on the basis of antagonistic relationships among four extrinsic tongue muscles: the genioglossus anterior (GGA), posterior (GGP), the hyoglossus (HG), and the styloglossus (SG). The computed patterns of equilibrium forces derived from EMG were then mapped into the muscle force space, defined by a coordinate system with GGP–HG and GGA–SG axes. The articulatory trajectories obtained correspond well to assumed tongue movements for the utterances. The vowel distribution in the muscle force space shows analogous patterning to vowel distributions in the acoustic and perceptual domains. This coincidence between the articulatory and perceptual representations of vowels implies the co-evolution of the somatoneural relation, and shows evidence of the modular organization of human speech production and perception. [Work supported in part by an NIH Grant No. 00120 to Haskins Laboratories.]