The Geniohyoid Muscle Directly Affects Masticatory Function: Evaluation with Decision-Tree Analysis.

PURPOSE: To clarify the effect of geniohyoid (GH) muscle morphology and related function on masticatory ability using a decision-tree analysis. MATERIALS AND METHODS: A total of 103 participants were enrolled. A cross-sectional area (CSA) of the GH muscle, neck circumference, body mass index, tongue pressure, jaw opening strength, and masticatory ability score were measured. The CSA of the GH muscle was selected as an independent variable for the first layer of the decision tree, with masticatory score as the dependent variable. RESULTS AND CONCLUSION: These data suggest that the CSA of the GH muscle may have a large impact on the masticatory ability score when evaluating masticatory ability.

Assessment of cricopharyngeal muscle aging with apoptotic markers.

OBJECTIVES: The aims of this study were to evaluate histochemical markers of apoptosis in the cricopharyngeus muscle, which is the gatekeeper of the pharyngoesophageal region during the swallowing process; to investigate the effects of primary aging on this muscle; and to determine whether a relationship exists with gastroesophageal reflux disease. MATERIALS AND METHODS: The study included 30 fresh cadavers with a time of death of 12 hours or less obtained from the Turkish Ministry of Justice Forensic Medicine Unit. All cadavers were dissected with routine postmortem skin incisions to extract specimens from the cricopharyngeus muscle and the esophagocardiac junction mucosa. Muscle degeneration and primary aging were demonstrated by immunodetection of Bax, Bcl-2, and Caspase-3 proteins as markers of the apoptosis. Esophageal specimens were examined for the presence of reflux esophagitis. RESULTS: The mean age was 41.5 (14-74) years, and the study included 18 male and 9 female cadavers. Three of them were excluded because of fixation artifacts. The mean Bax, Bcl-2, and Caspase scores showed no statistically significant relationship with age (P = 0.94). The right and left sides of the muscle were investigated separately, and the Bax scores of the right side of the cricopharyngeus muscle showed a statistically significant decrease with age (P = 0.026), whereas the Bax and Bcl-2 scores were increased with age (P = 0.035 and 0.049, respectively) on the left side. Evaluation of the 23 esophagus specimens revealed 10 cases of esophagitis. No relationship was found between the mean of each apoptotic marker and esophagitis. CONCLUSIONS: It is histopathologically not possible to demonstrate muscle death due to either primary aging or reflux. This might be attributable to the defensive capability of this unique muscle to maintain the feeding process.

Instrumental assessment of velopharyngeal function and resonance: a review.

UNLABELLED: The purpose of this literature review is to describe and discuss instrumental assessment techniques of the velopharyngeal function in order to diagnose velopharyngeal disorders and resonance characteristics. Both direct and indirect assessment techniques are addressed, in which successively nasopharyngoscopy, videofluoroscopy, magnetic resonance imaging (MRI), cephalometric radiographic analysis, computed tomography (CT), ultrasound, acoustic and aerodynamic measurements are considered. Despite the multiple instrumental assessments available to detect and define velopharyngeal dysfunction, the ideal technique is not yet accessible. Therefore, a combination of different quantitative parameters can possibly form a solution for a more reliable determination of resonance disorders. These multi-dimensional approaches will be described and discussed. The combination of quantitative measurement techniques and perceptual evaluation of nasality will probably remain necessary to provide sufficient information to make appropriate decisions concerning the diagnosis and treatment of resonance disorders. LEARNING OUTCOMES: The reader will be able to describe and discuss currently available instrumental techniques to assess the velopharyngeal mechanism and its functioning in order to diagnose velopharyngeal disorders. Additionally, he will be able to explain the possible advantages of the combination of several types of complementary measurement techniques.

The distributed lambda (λ) model (DLM): a 3-D, finite-element muscle model based on Feldman's λ model; assessment of orofacial gestures.

PURPOSE: The authors aimed to design a distributed lambda model (DLM), which is well adapted to implement three-dimensional (3-D), finite-element descriptions of muscles. METHOD: A muscle element model was designed. Its stress-strain relationships included the active force-length characteristics of the λ model along the muscle fibers, together with the passive properties of muscle tissues in the 3-D space. The muscle element was first assessed using simple geometrical representations of muscles in the form of rectangular bars. It was then included in a 3-D face model, and its impact on lip protrusion was compared with the impact of a Hill-type muscle model. RESULTS: The force-length characteristic associated with the muscle elements matched well with the invariant characteristics of the λ model. The impact of the passive properties was assessed. Isometric force variation and isotonic displacements were modeled. The comparison with a Hill-type model revealed strong similarities in terms of global stress and strain. CONCLUSION: The DLM accounted for the characteristics of the λ model. Biomechanically, no clear differences were found between the DLM and a Hill-type model. Accurate evaluations of the λ model, based on the comparison between data and simulations, are now possible with 3-D biomechanical descriptions of the speech articulators because of the DLM.

Magnetic resonance imaging assessment of the velopharyngeal mechanism at rest and during speech in Chinese adults and children.

PURPOSE: Recent applications of the magnetic resonance imaging (MRI) technique introduced accurate 3-dimensional measurements of the velopharyngeal mechanism. Further standardization of the data acquisition and analysis protocol was successfully applied to imaging adults at rest and during phonation. This study was designed to test and modify a noninvasive protocol for evaluating young children without using general anesthesia. In addition, the velopharyngeal structures and their maximal motion were compared between adults and children. METHOD: MRI data were acquired in 12 young adults and 9 children at rest and during speech production. Multiple measurements were made on the velopharyngeal and craniofacial structures as well as on the levator veli palatini muscle. RESULTS: Most of the ratio measurements of structural shape and maximal motion in the velopharyngeal and craniofacial regions were not significantly different between the adults and the children, despite the fact that the children had much smaller structures than the adults. CONCLUSION: The proportion of the velopharyngeal mechanism remains stable in young children and adults so that the motions of the velum and pharyngeal walls are adequate to close the velopharyngeal port completely.

Assessment of upper airway stabilizing forces with the use of phrenic nerve stimulation in conscious humans.

Phrenic nerve stimulation (PNS) applied at end-expiration allows the investigation of passive upper airway (UA) dynamic during wakefulness. Assuming that phasic UA dilating/stabilizing forces should modify the UA properties when twitches are applied during inspiration, we compared the UA dynamic responses to expiratory and inspiratory twitches (2 s and 200 ms after expiratory and inspiratory onset, respectively) in nine men (mean age 28 yr). This procedure was repeated with a 2-cm mouth opening provided with a closed mouthpiece. The percentage of flow-limited (FL) twitches was significantly higher when PNS was realized during expiration than during inspiration. Maximal inspiratory flow (Vi(max)) of FL twitches was significantly higher for inspiratory twitches (1,383 +/- 42 and 1,185 +/- 40 ml/s). With mouth aperture, Vi(max) decreased with an increase in the corresponding pharyngeal resistance values, and the percentage of twitch with a FL regimen increased but only for inspiratory twitches. We conclude that 1) UA dynamics are significantly influenced by the inspiratory/expiratory timing at which PNS is applied, 2) the improvement in UA dynamic properties observed from expiratory to inspiratory PNS characterizes the overall inspiratory stabilizing effects, and 3) mouth aperture alters the stability of UA structures during inspiration.

Assessment of muscle action on upper airway stability in anesthetized dogs.

Skeletal muscle activation is believed to be important in the maintenance of upper airway patency. To determine where and how muscles affect pharyngeal stability, we assessed in heavily anesthetized, ventilated dogs, the negative pressure required to close the nasopharynx and the passage from the oral to the pharyngeal airway before and after electrical stimulation of six pairs of upper airway muscles: the sternohyoid, sternothyroid, ceratohyoid, thyrohyoid, genioglossus, and geniohyoid. Before muscle stimulation, the pressures required to close the nasopharynx and the oral passage were -9.8 +/- 2.3 (mean +/- SEM) and -4.9 +/- 1.9 cm H2O, respectively. Submaximal electrical stimulation of each of the six muscle pairs caused consistent and substantial improvements in nasopharynx closing pressure. In contrast, the stabilizing actions of these muscles on the oral passage was less consistent and smaller in magnitude. Using pressure in the sealed upper airway as an index of forces acting on the airway, we found a strong association between the effect of muscle stimulation on the closing pressure and the effect of muscle stimulation on producing a dilating force on the airway. We conclude that muscles in the anterior and lateral pharyngeal wall improve nasopharynx stability to a greater extent than oral passage stability and that the action by any of these six muscle pairs improves airway stability through their ability to dilate the upper airway.