Styloglossus Research Articles

Growing stylohyoideus muscle insertion to the hyoid bone with special reference to its topographical relation to the intermediate tendon of digastricus muscle: A histological study using human fetuses

BackgroundIn adults, the intermediate tendon of digastricus muscle usually runs along the medial or lateral side of the stylohyoideus muscle insertion. To provide a better understanding of the variations, we examined the topographical anatomy of the muscle and tendon in fetuses. MethodsWe examined histological sections from six early-term, 26 mid-term and six near-term fetuses (approximately 8–9, 12–18 weeks and 25–33 weeks). ResultsAt early-term, an initial sheath of intermediate tendon of digastricus muscle received the stylohyoideus muscle at the superior aspect. The muscle and tendon was distant from the hyoid. At mid-term, near the insertion to the hyoid greater horn, the stylohyoideus muscle consistently surrounded more than 2/3 of the intermediate tendon circumference. In contrast, we found no near-term specimen in which the stylohyoideus muscle surrounded the intermediate tendon. The multilayered tendon sheath was fully developed until near-term and connected to the body of hyoid by an intermuscular septum between the thyrohyoideus muscle and one or two of suprahyoid muscles. Therefore, the hyoid insertion of the styloglossus muscle was a transient morphology at mid-term. ConclusionThe stylohyoideus muscle insertion was appeared to move from the tendon sheath to the hyoid greater horn and, until near-term, return to the tendon sheath. A fascia connecting the tendon sheath to the body of hyoid was strengthened by the suprahyoid and infrahyoid muscles. The latter muscles seemed to regulate fixation/relaxation of the intermediate tendon to the hyoid. The stylohyoideus muscle slips sandwiching the intermediate tendon might be a rare morphology.

Age-related sex differences in tongue strength and muscle morphometry in a rat model

ObjectiveTo investigate potential effects of sex on voluntary tongue strength, evoked twitch and tetanic tension, speed of contraction, and muscle fiber cross-sectional area in the muscles of the rat tongue. Additionally, we aimed to determine whether estrous cycle stage impacts any of the dependent variables as a pilot investigation into the use of female rats in a model of tongue exercise and aging. DesignFischer 344-Brown Norway male and female rats in two age groups (16 middle-aged, 16 young-adult) were trained to use a tongue force operandum. Tongue muscle contraction, myosin heavy chain (MyHC) composition, and cross section area of the genioglossus and styloglossus muscles were examined. Vaginal lavage determined estrous cycle stage of the female rats daily. ResultsThe female group had significantly lower evoked twitch and tetanic tension, longer contraction times, and a smaller proportion of MyHC type IIa and MyHC type IIx in the styloglossus muscle. There was no significant sex effect in maximal voluntary tongue force (MVTF) despite a significant weight difference between the male and female groups. There were no significant age or sex effects in the genioglossus. Estrous cycle stage did not have a significant effect on any of the dependent variables. ConclusionsSex and age both have a significant effect on tongue muscle structure and physiology. While the female group showed reduced contraction speed and maximal twitch and tetanic tension relative to the male group, differences in muscle morphology appeared to vary by muscle.

Abnormal Relationship with the Styloglossus and Medial Pterygoid Muscles: A Description of Two Cases

IntroductionLateral pharyngeal space is of great interest to dentists and surgeons. The pre‐styloid space is located in a portion of the lateral pharyngeal space. The pre‐styloid space has stylohyoid muscle, styloglossus muscle, stylopharyngeus muscle, and external carotid artery. Medial and lateral pterygoid muscles are located anterior to the pre‐styloid space. This study describes the relationship of the structures in the cases.HypothesisThe muscular attachment from the medial pterygoid muscle to the styloglossus muscle is unique. Morphological understanding with the external carotid artery of the cases will be helpful to prevent surgical mistakes.MethodsThe two cadavers were found to have a rare medial pterygoid and styloglossus during the dissection in 2020. It had been assessed in the adjacent structures.ResultsBoth cases showed that the medial pterygoid muscle has a tendinous attachment from the inside to the styloglossus muscle. The first case’s tendon and muscle were 5mm wide, 3mm thick, and 10mm long and attached to 15mm proximal area of the styloglossus muscle (Fig. 1). The second case’s tendon was 5mm wide, 1mm thick, and 7mm long and attached to a 12mm proximal area of the styloglossus muscle (Fig. 2). Both styloglossus muscles were attached to the tip of the styloid process. Both styloid processes were more than 25mm long from the temporal bone (Fig. 2).Both external carotid arteries passed through between stylohyoid and styloglossus muscles and ran behind the tendon and up to the head of the mandible (Fig. 1.C).ConclusionThe medial pterygoid muscle attaches to the ramus of the mandible. The ramus has an accessory fascicle that attaches to the styloglossus muscle in the fetus. It may not entirely disappear after being born. The length of the styloid process may be a contributing factor in the development of eagle syndrome.The styloglossus muscle plays an essential role in swallowing, mastication, and speech. The attachment involves the function of the motion of the mandible. The external carotid artery travels along with the accessory muscle‐tendon and needs to be considered during surgery.

Methodology for eliciting the brainstem trigeminal-hypoglossal reflex in humans under general anesthesia

ObjectiveBrainstem trigeminal-hypoglossal reflexes (THRs), also known as the jaw-tongue reflexes, coordinate the position of the tongue in the mouth in relation to the jaw movement during oromotor behaviors such as mastication, swallowing, vocalization, and breathing. Their use in brainstem surgery however, has never been assessed in spite of its potential benefit possibly due to the lack of a methodology to elicit these reflexes under general anesthesia. MethodsWe proposed a technique to elicit the THRs during total intravenous anesthesia (TIVA) consisting on a V3 infrazygomatic train stimulation paradigm and recording from the Styloglossus (31 patients) and the Genioglossus (21 patients) muscles to elicit long latency responses. ResultsThe THR was successfully recorded using the V3 stimulation point in 82.1% of patients, of which 96.9% presented a response on the Styloglossus muscle (Jaw-opening reflex) while 0.06% presented a response on the Genioglossus muscle instead (Jaw-closing reflex). ConclusionsThe THRs can be successfully recorded in surgery under general anaesthesia with the predominant reflex seen being the jaw-opening reflex. SignificanceWe provide a novel method to elicit the THRs during general anesthesia, which could be of aid in brainstem surgery.

Progressive Protrusive Tongue Exercise Does Not Alter Aging Effects in Retrusive Tongue Muscles.

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.

Functional characterization of extrinsic tongue muscles in the Pink1-/- rat model of Parkinson disease.

Parkinson disease (PD) is associated with speech and swallowing difficulties likely due to pathology in widespread brain and nervous system regions. In post-mortem studies of PD, pathology has been reported in pharyngeal and laryngeal nerves and muscles. However, it is unknown whether PD is associated with neuromuscular changes in the tongue. Prior work in a rat model of PD (Pink1-/-) showed oromotor and swallowing deficits in the premanifest stage which suggested sensorimotor impairments of these functions. The present study tested the hypothesis that Pink1-/- rats show altered tongue function coinciding with neuromuscular differences within tongue muscles compared to wildtype (WT). Male Pink1-/- and WT rats underwent behavioral tongue function assays at 4 and 6 months of age (n = 7-8 rats per group), which are time points early in the disease. At 6 months, genioglossus (GG) and styloglossus (SG) muscles were analyzed for myosin heavy chain isoforms (MyHC), α-synuclein levels, myofiber size, centrally nucleated myofibers, and neuromuscular junction (NMJ) innervation. Pink1-/- showed greater tongue press force variability, and greater tongue press forces and rates as compared to WT. Additionally, Pink1-/- showed relative increases of MyHC 2a in SG, but typical MyHC profiles in GG. Western blots revealed Pink1-/- had more α-synuclein protein than WT in GG, but not in SG. There were no differences between Pink1-/- and WT in myofiber size, centrally-nucleated myofibers, or NMJ innervation. α-synuclein protein was observed in nerves, NMJ, and vessels in both genotypes. Findings at these early disease stages suggest small changes or no changes in several peripheral biological measures, and intact motor innervation of tongue muscles. Future work should evaluate these measures at later disease stages to determine when robust pathological peripheral change contributes to functional change, and what CNS deficits cause behavioral changes. Understanding how PD affects central and peripheral mechanisms will help determine therapy targets for speech and swallowing disorders.

XROMM and diceCT reveal a hydraulic mechanism of tongue base retraction in swallowing

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.

Radiological approach for the newly incorporated T staging factor, depth of invasion(DOI), of the oral tongue cancer in the 8th edition of American Joint Committee on Cancer (AJCC) staging manual: assessment of the necessity for elective neck dissection.

The 8th edition of American Joint Committee on Cancer's (AJCC) Cancer Staging Manual was modified by incorporating depth of invasion (DOI) in the T categorization of oral cavity cancer. This is because DOI is strongly associated with cervical lymph node metastasis, which is the most important negative prognostic factor of oral cavity cancer. This major change in the AJCC Cancer Staging Manual caused re-staging of T category in several cases. Although, the DOI on MRI and CT (radiological DOI; r-DOI) strongly correlated with pathological DOI (p-DOI), it is often 2-3mm larger than p-DOI. Due to this variance, estimation of p-DOI based on r-DOI may not be accurate. However, when a lesion is undetectable on MRI, p-DOI was often smaller than 4mm. On the other hand, when MRI depicts lesions with styloglossus and hyoglossus muscle invasion, p-DOI was always larger than 4mm. These correlations between MRI findings and p-DOI are important when assessing the need for elective neck dissection, as the National Comprehensive Cancer Network (NCCN) recommends elective neck dissection in cases with DOI greater than 4mm.

Safe surgical zone during TORS radical tonsillectomy: An anatomical and radiological study

ObjectiveParapharyngeal space contains intricate vascular anatomy (external and internal carotid arteries) that might be inadvertently injured during the dissection in this plane. None of the bony landmarks can be used during the transoral robotic surgery (TORS) radical tonsillectomy as these landmarks lie lateral to the internal carotid artery (ICA) and external carotid artery (ECA) in transoral approach. Our study aims to identify the safe surgical limits during the dissection of parapharyneal space in TORS radical tonsillectomy and to correlate the same with radiological study. Material and methodsFifteen cadavers (30 head and neck regions) and 50 CT-Angiogram of neck (100 head and neck regions) were included in the anatomical and radiological study respectively. The vertical midpoint of anterior tonsillar pillar (palatoglossus muscle) was taken as the reference point and all the measurements were done at the level of reference point both for anatomical and radiological study. Distance between tonsillar fossa and ECA, distance between tonsillar fossa and ICA, relation between ECA and styloglossus and relation between ICA and stylopharyngeus at reference level were studied. ResultsThe mean distance of ECA from the tonsillar fossa at the reference point was 18.2 mm in the anatomical study and 16.2 mm in the radiological study. The mean distance of ICA from the tonsillar fossa was 23.4 mm and 23.3 mm in the anatomical study and radiological study. There was no significant difference between the anatomical and radiological findings for both the mean distance between ECA and ICA to the tonsillar fossa (p value was 0.45 and 0.30 respectively). ECA was located posterolateral to styloglossus in 24 cases (80.0%) and 79 cases (79.0%) in the anatomical and radiological study respectively. ICA was found posterolateral to stylopharyngeus in 21 cases (70.0%) and 69 cases (69.0%) in the anatomical and radiological study respectively. ConclusionThe muscular plane between styloglossus and stylopharyngeus can be used as an envelope to locate the ECA and ICA that lie medial to these critical vascular structures during TORS. We propose to divide the parapharyngeal space into two compartments (anterior and posterior) based on the surgical perspective of inside-out anatomy. The anterior compartment houses styloglossus muscle with ECA posterolateral to it and the posterior compartment has stylopharyngeus and ICA posterolateral to it.

From the stylet of the temple to the tongue in so-called Riolan's bouquet

The styloglossus muscle is a key landmark for staging and surgery of certain squamous cell cancers of the oropharynx. The purpose of this historical note is to try to determine when the styloglossus muscle was described for the first time, and to understand its integration into the so-called Riolan's bouquet.

Effects of inhaled fluticasone propionate on extrinsic tongue muscles in rats.

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.

Transcervical endoscopic approach for parapharyngeal space: a cadaver study and clinical practice

Background: The traditional transcervical approach is frequently applied but limited in handling the tumors in parapharyngeal space.Objectives: We explore a new transcervical endoscopic approach with more direct visualization, less complications, and better outcomes.Material and methods: Eight cadaver heads (sixteen sides) were prepared for endoscopic dissection. Clinical cases were carefully selected, and thirty patients accepted the transcervical endoscopic surgery.Results: The transcervical approach with an endoscopic video system clearly exposed the detailed structures in the parapharyngeal space. The stylopharyngeus, styloglossus muscles, and styloid process were critical landmarks in this approach. During the thirty cases of clinical surgeries, internal carotid arteries and cranial nerves could be effectively exposed and protected with the endoscopic video system. Accurate hemostasis could be achieved under endoscopic transcervical approach with a mean amount between 30 to 100 ml of hemorrhaging. There was no postoperative hemorrhages and emergency tracheotomies. The follow up led to promising results.Conclusions and significance: The transcervical endoscopic approach provides a wide corridor for surgery in the parapharyngeal space. With accurate hemostasis, this approach can be applied as the first-line strategy for parapharyngeal surgeries in selected patients.

The Adult Ts65Dn Mouse Model of Down Syndrome Shows Altered Swallow Function

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.

A cadaveric study quantifying the anatomical landmarks of the facial artery and its parapharyngeal branches for safe transoral surgery.

Hemorrhage remains a major potential risk when performing any form of transoral surgery. This is the first study to focus on the location of the facial artery "bulb" (FaB) and its tonsillar branches within the parapharyngeal space (PPS) from the perspective of the transoral surgeon. A total of 44 hemi-sections were dissected via the transoral approach with endoscopic assistance: 26 from fresh-frozen specimens and 18 formalin-fixed hemi-sections. The distance from the superior apex of the FaB to the pterygoid hamulus (PH) was recorded, and the arterial branching variations described. The average distance from the PH to the FaB was 4.17 ± 0.4 cm. In 90.9% of cases, the two tonsillar artery branches passed between styloglossus muscle (SGM) and stylopharyngeus muscle (SPM). Understanding the FaB location and its branching patterns offers the surgeon confidence dissecting in the PPS transorally.

Magnetic resonance imaging findings of styloglossus and hyoglossus muscle invasion: Relationship to depth of invasion and clinical significance as a predictor of advisability of elective neck dissection in node negative oral tongue cancer

PurposeBy 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. MethodForty-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-). ResultsThere 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, p < 0.001). 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). ConclusionsPathological 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.

Styloglossus muscle: a critical landmark in head and neck oncology

GoalTo document the role of the styloglossus muscle (SG) in head and neck oncology and at the time of surgical treatment and mandibular preservation surgery for squamous cell carcinoma of the lateral oropharynx (SCCLO). MethodBased on a search conducted within the Pubmed, Embase, and Cochrane databases, using the key words SG muscle, parapharyngeal space and oropharynx, the authors discuss the embryology, physiology, anatomy and radiology of this muscle as well as its role in the oncologic staging surgery of SCCLO. ResultsThe most specific radiologic exam to evaluate the involvement of SG muscle in SCCLO is magnetic resonance imaging (MRI). According to the eigth international staging classification systems, radiologic invasion of the SG muscle, at the time of MRI, leads to reclassify as T4a many tumors considered as T1-3 at the time of clinical and/or on computerized tomography evaluation. This must lead to extreme care when comparing oncologic results from series published prior and after the MRI era. When transoral resection of the SG muscle is advocated for SCCLO, one must know that this maneuver brings numerous arterial and venous structures within the operative field. If difficulties to achieve safe margins of resection and/or to control bleeding are encountered, a simple trans cervical maneuver described herein is most useful. ConclusionThe importance of the SG muscle should be emphasized as a touchstone for staging and surgeon's guide to mandibular preservation surgery of SCCLO. The various approaches allowing the control of this muscle and its vascular environment must be taught at the time of initial training.

Anatomical study of jugular foramen in the neck

IntroductionThe anatomical complexity of the jugular foramen makes surgical procedures in this region delicate and difficult. Due to the advances in surgical techniques, approaches to the jugular foramen became more frequent, requiring improvement of the knowledge of this region anatomy. ObjectiveTo study the anatomy of the jugular foramen, internal jugular vein and glossopharyngeal, vagus and accessory nerves, and to identify the anatomical relationships among these structures in the jugular foramen region and lateral-pharyngeal space. MethodsA total of 60 sides of 30 non-embalmed cadavers were examined few hours after death. The diameters of the jugular foramen and its anatomical relationships were analyzed. ResultsThe diameters of the jugular foramen and internal jugular vein were greater on the right side in most studied specimens. The inferior petrosal sinus ended in the internal jugular vein up to 40mm below the jugular foramen; in 5% of cases. The glossopharyngeal nerve exhibited an intimate anatomical relationship with the styloglossus muscle after exiting the skull, and the vagal nerve had a similar relationship with the hypoglossal nerve. The accessory nerve passed around the internal jugular vein via its anterior wall in 71.7% of cadavers. ConclusionAnatomical variations were found in the dimensions of the jugular foramen and the internal jugular vein, which were larger in size on the right side of most studied bodies; variations also occurred in the trajectory and anatomical relationships of the nerves. The petrosal sinus can join the internal jugular vein below the foramen.

Effect of neuromuscular electrical stimulation frequency on muscles of the tongue.

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. 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. 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. 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.

Osseous Loading by a Volume-Reduced Tongue During Muscle Contractions

To investigate how tongue volume reduction affects loads on surrounding bone surfaces produced by neuromuscular stimulation of the tongue. Of each pair of same-gender minipig siblings, 1 received tongue reduction and 1 underwent sham surgery. Either immediately (acute, 6 pairs) or 1month (chronic, 5 pairs) after surgery, bone surface and/or suture strains and pressures were recorded from the following locations when the hypoglossal nerve trunk, hypoglossal nerve medial branch, hypoglossal nerve lateral branch, genioglossus, and styloglossus (SG) were electrically stimulated: 1) three rosette strain gauges on the premaxillary palatal surface (premaxilla [PM]) and lingual surfaces of the mandibular alveolus at anterior (mandibular incisor [MI]) and posterior (mandibular molar [MM]) locations; 2) two single-element strain gauges over the palatal surface of the premaxillary-maxillary suture and the lingual surface of the mandibular symphysis; and 3) two pressure transducers on the palatal surface of the maxilla (palatal process) and the lingual surface of the mandibular alveolus (mandibular corpus). Compared with the sham animals in the acute study, reduction animals showed significantly decreased PM and MI strains, as well as palatal process pressure.With muscle contractions, mandibular symphysis and MM strains were enhanced significantly with a more dorsal orientation.In the chronic study, reduction animals showed decreased PM and increased MM strains. On comparison of chronic versus acute studies, PM, MI, and MM strains under SG stimulation were significantly smaller whereas MM strain was significantly larger under hypoglossal nerve trunk, hypoglossal nerve lateral branch, and SG stimulations. Muscle contractions from a volume-reduced tongue produce lower and higher loads in the anterior and posterior mouth, respectively.However, although the effects on reducing loads in the anterior mouth are persisting over time, compensatory load enhancement in the posterior mouth diminishes owing to surgical healing.

Non-isometric muscular performance evaluation of styloglossus muscle during tongue vertical movement

Non-isometric muscular performance evaluation of styloglossus muscle during tongue vertical movement