The effect of chin-to-chest contact on upper neck axial force in UN Regulation No. 129 frontal impact tests of child restraint systems.

OBJECTIVE: The objective of this study was to investigate the effect of chin-to-chest contact on upper neck axial force in United Nations (UN) Regulation No. 129 frontal impact tests of child restraint systems. METHODS: Frontal impact pilot experiments were carried out according to the test procedure in UN Regulation No. 129. Q-Series child dummies were seated in a small convenience sample of forward-facing child restraint systems. The timing and duration of chin-to-chest contact were determined using the procedure for calculating external head impact force in SAE J2052. RESULTS: Chin-to-chest contact was observed in all of our experiments and generated a tensile peak in the upper neck axial force of the Q-Series dummies. Prior to chin-to-chest contact, a purely inertial, noncontact peak was observed in the axial tension force. The tensile peak due to chin-to-chest contact was often greater than the inertial, noncontact peak force. CONCLUSIONS: Chin-to-chest contact can increase axial neck tension force beyond the level it would reach under purely inertial loading. Adopting upper neck axial force in regulation, without considering how the force is generated, might encourage child restraint designs that mitigate only chin-to-chest contact, rather than the true inertial neck loading.

Chin augmentation with the use of cannula from a single, midline entry point: Evaluation of 50 patients.

BACKGROUND: A chin that is of right size, shape, and contour plays a crucial role in overall facial balance and esthetically harmonious appearance. Dermal fillers have been widely used for correcting mild to moderate chin retrusion and resorption. AIMS: The aim of this study was to share our preferential technique for chin augmentation and to evaluate our results in 50 patients. METHODS: A total of 50 patients consisting of females who received hyaluronic acid injection for chin augmentation and rejuvenation were enrolled in the study. We have described chin augmentation technique with the use of cannula from a single, midline entry point. RESULTS: The study included 50 female patients, and the mean age was 37.56 ± 8.84 years. The median injected filler volume for augmentation of the mental area was 2.25 mL (minimum = 1, maximum = 4 mL). Four (8%) patients had ecchymosis related to the procedure. CONCLUSION: Chin has a profound effect on the perception of attractiveness and is an area of concern for rejuvenation of the lower third of the face. Our preferential technique allows the practitioners to increase the likelihood of a satisfactory esthetic outcomes and minimize the risks of the procedure.

Effects of game-based chin tuck against resistance exercise vs head-lift exercise in patients with dysphagia after stroke: An assessor-blind, randomized controlled trial.

OBJECTIVE: To compare the effects of game-based chin-tuck against resistance exercise and head-lift exercise on swallowing function and compliance of patients with dysphagia after stroke. PATIENTS AND METHODS: A total of 37 patients with stroke were randomly assigned to 2 groups. The experimental group performed game-based chin tuck against resistance exercise, whereas the control group performed traditional head-lift exercise. The videofluoroscopic dysphagia scale (VDS) and penetration-aspiration scale (PAS) were used to evaluate swallowing function. In addition, the functional oral intake scale (FOIS) was used for dietary assessment. Finally, the numerical rating self-report scale was used to assess compliance (motivation, interest/enjoyment, physical effort needed, muscle fatigue) with the 2 exercises. RESULTS: After intervention, there was no significant difference in VDS, PAS, and FOIS between the 2 groups. Comparing the compliance with the 2 exercises, the scores for motivation and interest/enjoyment items were significantly higher, and the scores for physical effort needed and muscle fatigue were significantly lower, in the experimental group than in the control group. CONCLUSION: Game-based chin-tuck against resistance exercise not only has a similar effect to head-lift exercise on swallowing function of patients with dysphagia, but is also a less strict and more enjoyable and interesting method.

Determining the Efficacy of the Chin-Down Maneuver Following Esophagectomy With Fiberoptic Endoscopic Evaluation of Swallowing.

OBJECTIVES: To clarify the reliability of fiberoptic endoscopic evaluation of swallowing (FEES) compared to videofluoroscopic swallowing studies (VFSSs). Second, we explored the effect of the chin-down maneuver in the presence or absence of vocal fold paralysis (VFP) using FEES in patients with 3-field lymphadenectomy (3FL) postesophagectomy. DESIGN: Retrospective data collection from FEES and VFSS. SETTING: Dysphagic clinics in the ear, nose, and throat department. PARTICIPANTS: Patients (N=15) underwent esophagectomy with 3FL at the Department of Gastroenterologic Surgery, during a period of 12 months. INTERVENTIONS: The patients underwent FEES and VFSS with neutral and chin-down maneuvers 2 weeks postoperatively. Two raters of speech pathology blindly scored aspiration, penetration, delayed initiation, and pharyngeal clearance in the pyriform sinus and vallecula, respectively, from recorded movie clips of both examinations, using the penetration aspiration scale (PAS) and modified Hyodo FEES rating scale. MAIN OUTCOME MEASURES: The intrarater and interrater correlation coefficients of each parameter examined with FEES. Statistical comparison of each parameter between FEES and VFSS and of each parameter evaluated using FEES between 2 maneuvers with or without VFP. RESULTS: The intrarater and interrater correlation coefficients of the PAS and pyriform sinus examined with FEES were both statistically consistent between the 2 raters. The PAS and pyriform sinus evaluated using FEES were significantly correlated with those evaluated in a VFSS (P<.05). The 2 parameters evaluated using FEES were significantly (P<.05) improved with the chin-down maneuver compared to the neutral maneuver, especially in VFP patients. CONCLUSION: FEES performed postesophagectomy with 3FL for evaluation of aspiration is as reliable statistically as VFSSs. The chin-down maneuver is especially useful for reducing the PAS score and pyriform sinus in VFP patients.

Evaluation of accuracy and sensory outcomes of mandibular reconstruction using computer-assisted surgical simulation.

PURPOSE: To introduce a modified protocol for mandibular reconstruction and evaluate the protocol using a standardized assessment method. METHOD: This retrospective study involved a case series of nine patients who underwent mandibular reconstruction between 2015 and 2017. The modular protocol comprised three novel modifications in terms of computer-assisted surgical simulation (CASS); surgical template (ST), and surgical procedure. The standardized postoperative evaluation consisted of operation time, part comparison analysis (PCA), facial symmetry, and mechanical quantitative sensory testing. RESULTS: The surgery successfully removed the affected mandible and preserved the inferior alveolar neurovascular bundle (IANB). PCA revealed that the mean error and standard deviation were 0.92 and 0.96 mm, respectively, for all mandibular surface sites. Follow-up results showed good facial symmetry, existence of sensation in lower lip, and no significant differences in pulp vitality between both sides (p = 0.181). Also, the results showed a reduction in the overall operating time. CONCLUSION: The modified mandibular reconstruction method used in this study could repair lateral mandibular defects and preserve the sensory function of the chin and lower lip.

Perception of aesthetics and personality traits in orthognathic surgery patients: A comparison of still and moving images.

It is common in practicing orthognathic surgery to evaluate faces with retruded or protruded chins (dysgnathic faces) using photographs. Because motion may alter how the face is perceived, we investigated the perception of faces presented via photographs and videos. Two hundred naïve raters (lay persons, without maxillo facial surgery background) evaluated 12 subjects with varying chin anatomy [so-called skeletal Class I (normal chin), Class II (retruded chin), and Class III (protruded chin)]. Starting from eight traits, with Factor analysis we found a two-Factor solution, i.e. an "aesthetics associated traits cluster" and a Factor "personality traits cluster" which appeared to be uncorrelated. Internal consistency of the Factors found for photographs and videos was excellent. Generally, female raters delivered better ratings than males, but the effect sizes were small. We analyzed differences and the respective effect magnitude between photograph and video perception. For each skeletal class the aesthetics associated dimensions were rated similarly between photographs and video clips. In contrast, specific personality traits were rated differently. Differences in the class-specific personality traits seen on photographs were "smoothed" in the assessment of videos, which implies that photos enhance stereotypes commonly attributed to a retruded or protruded chin.

Análisis de funciones discriminantes para la estimación del sexo con la mandíbula en población mexicana / Gender assessment using the mandible in the mexican population

Introducción. El presente trabajo tuvo como objetivos: conocer el grado de dimorfismo sexual entre una población de la Ciudad de México y otra de Hidalgo, México; y el desarrollo de funciones discriminantes para la estimación de sexo por medio de la mandíbula, para identificación humana. Material y métodos. Se analizaron morfométricamente mandíbulas de dos muestras, una procedente de la Ciudad de México (MEX) (Colección-UNAM) y otra de Santa María Xigui, Alfajayucan, Hidalgo, México (XIG). La muestra MEX consistió en 108 mandíbulas (75 masculinos y 33 femeninos) y en la muestra XIG se utilizaron 56 mandíbulas (33 femeninos y 30 masculinos), con una edad media entre 49,2 y 55,1 años. Se tomaron 18 medidas mandibulares y se desarrollaron cuatro funciones discriminantes para estimar el sexo con cada muestra. Resultados. Se observó el mismo patrón de diferenciación en ambas poblaciones, no obstante se presentaron diferencias entre estas, ya que se demostró que existe mayor grado de diferencias sexuales en XIG. Las funciones discriminantes desarrolladas para ambas poblaciones, alcanzaron entre el 76,4 y 84% de clasificación sexual correcta. Conclusiones. La muestra XIG presentó mayor dimorfismo sexual que la muestra MEX, con mandíbulas más alargadas y mentones altos y alargados. Las funciones discriminantes del presente trabajo presentan porcentajes de clasificación mayores a los de las demás propuestas existentes. Y al ser desarrolladas a partir de población contemporánea, pueden ser utilizadas en contextos forenses para identificación humana con restos completos o fragmentados y/o incompletos (AU)

Introduction. The aims of the present study were to determine the level of sexual dimorphism among two populations, one from Mexico City and the other from Hidalgo, Mexico, as well as the development of discriminant functions for gender assessment using the mandible, for human identification. Material and methods. Two samples of mandibles were analysed morphometrically, one from Mexico City (Colección-UNAM) (MEX), and the other from Santa María Xigui, Alfajayucan, Hidalgo, México (XIG). The sample MEX consisted of 108 mandibles (75 male and 33 female), and XIG sample with 56 mandibles (33 female and 30 male), with a mean age between 49.2 to 55.1 years old. Eighteen measurements were taken to create four discriminant functions for gender estimation for each sample. Results. The differentiation pattern among populations (samples) was the same. Nevertheless, there were differences between them, with a higher degree of sexual difference in XIG. The discriminant functions, developed for both populations, achieved a correct classification in between 76.4 and 84%, respectively. Conclusions. The XIG sample showed greater sexual dimorphism than the MEX sample, with longer mandibles and higher and elongated chins. The discriminant functions generated in this study, present higher classification percentages than the other existing proposals. Furthermore, being developed from the contemporary population, they can be used in forensic contexts for human identification, with complete or fragmented/incomplete remains (AU)

Intraoral Observation of the Mentalis and Incisivus Labii Inferioris Muscles.

The mentalis (MT) and the incisivus labii inferioris (ILI), which are accessory muscles of the orbicularis oris (OO) muscle, form an intertwined and three-dimensionally related complex. The purpose of this study is to clarify the relationship between the MT, ILI, and OO muscles via intraoral dissection. Twenty-two sides from 11 fresh adult Caucasian cadaveric heads were used, and the MT, ILI, and OO dissected under the surgical microscope. Next, measurements of the bony attachment were carried out on another 12 sides. The fibers of the MT were separated into 2 parts: a superior and an inferior part with the former coursing anteromedially and joining the inferior part of the OO. The latter coursed anteroinferiorly to the skin of the chin. The ILI traveled anterolaterally and joined the inferior part of the OO. Inferior labial branches of the mental nerves ran on the OO. There was a significant difference (P = 0.0001) between specimens that were edentulous or had severe periodontitis with regard to the distance from the alveolar ridge to the upper side of the quadrangle when compared with specimens with mild periodontitis. However, there was no significant difference (P > 0.05) between specimens that were edentulous or had severe periodontitis specimens with mild periodontitis with regard to the distance from the inferior border of the mandible to the lower side of the quadrangle. We believe that the observations of this study could help surgeons better understand the anatomy of the chin and minimize complications following surgical and other invasive procedures in this area.

Evaluation of the relation between lipid coat, transepidermal water loss, and skin pH.

OBJECTIVE: The epidermis is an epidermal barrier which accumulates lipid substances and participates in skin moisturizing. An evaluation of the epidermal barrier efficiency can be made, among others, by the measurement of the following values: the lipid coat, the transepidermal water loss (TEWL) index, and pH. MATERIALS: The study involved 50 Caucasian, healthy women aged 19-35 years (mean 20.56). METHODS: Measurements were made using Courage & Khazaka Multi Probe Adapter MPA 580: Tewameter TM 300, pH-Meter PH 905, Sebumeter SM 815. The areas of measurements included forehead, nose, left cheek, right cheek, chin, and thigh. RESULTS: In the T-zone, the lipid coat was in the range between 0 and 270 µg/cm2 (mean 128 µg/cm2 ), TEWL between 1 and 55 g/m2 /h (mean 11.1 g/m2 /h), and pH 4.0-5.6 (mean 5.39). Lower values of the lipid coat up to 100 µg/cm2 were accompanied by TEWL greater than 30 g/m2 /h and less acidic pH of 5.6-9.0. In the U-zone the range of lipid coat was up to 200 µg/cm2 (mean 65.2 µg/cm2 ), the skin pH remained 4.0-5.6 (mean 5.47), and TEWL was in the range between 1 and 20 g/m2 /h (mean 8.7 g/m2 /h). Lower values of the lipid coat up to 100 µg/cm2 were accompanied by TEWL between 1 and 20 g/m2 /h and less acidic pH of 5.6-9.0. High values of the lipid coat between 180 and 200 µg/cm2 were connected with TEWL of 1-15 g/m2 /h. On the skin of the thigh, we observed a very thin lipid coat - 35 µg/cm2 (mean 5.6 µg/cm2 ), pH (mean 5.37), and TEWL (mean 8.5 g/m2 /h) were considered by us to be within regular limits. CONCLUSIONS: In the T-zone, a thinner lipid coat resulted in relatively high TEWL and pH levels changing toward alkaline. In the U-zone, thinner lipid coat was accompanied by lower TEWL and pH changing toward alkaline. We also observed that lower values of lipid coat up to 100 µg/cm2 were associated with higher pH values ranging toward the basic character pH 5.6-9.0).

Effects of Chin-Down Maneuver on the Parameters of Swallowing Function After Esophagectomy With 3-Field Lymphadenectomy Examined by Videofluoroscopy.

OBJECTIVES: To determine the effect of the chin-down maneuver after esophagectomy with 3-field lymphadenectomy (3FL) on pharyngeal residue, upper esophageal sphincter (UES) opening, and laryngeal closure. DESIGN: Prospective data were collected from a pharyngeal videofluoroscopic swallowing study. SETTING: Dysphagia clinics. PARTICIPANTS: Patients selected according to the inclusion criteria (N=14; mean age, 65.9y) from a total of 43 patients who underwent esophagectomy with 3FL from May to December 2014 were enrolled. INTERVENTIONS: Videofluoroscopy was conducted in head-neutral and chin-down positions to measure the pharyngeal constriction ratio (PCR), amount of residue in the vallecula and pyriform sinus after the first swallow, UES opening diameter, duration of UES opening, and duration of laryngeal vestibule closure. MAIN OUTCOME MEASURES: The aforementioned parameters were compared statistically between the head-neutral and chin-down positions. RESULTS: In comparison with the neutral group, the PCR and residue in the pyriform sinus were significantly smaller in the chin-down group (P<.01). However, the residue in the vallecula did not differ significantly from that of the neutral group (P=.44). The UES opening diameter, duration of UES opening, and duration of laryngeal vestibule closure were all significantly larger in the chin-down group than in the neutral group (P<.05). CONCLUSIONS: This study demonstrates that use of the chin-down maneuver after esophagectomy with 3FL can help expedite swallowing by strengthening pharyngeal constriction, widening the UES, and enhancing laryngeal closure.

Treating Scars of the Chin and Perioral Region.

Lip and chin scarring occurs owing to reconstruction of congenital, cancer resection, or traumatic defects. Knowledge of lip anatomy and function is critical to optimize results. Realistic expectations should be established before intervention. Scar revision and reconstruction is ideally performed with a subunit approach, placing scars along aesthetic borders and performing subunit reconstruction to camouflage scars. Surgical techniques include direct excision, scar reorientation, local flap rearrangement, pedicled flaps, and regional or free flaps. Resurfacing/adjunctive procedures play important roles in the treatment of scars. This article reviews the anatomy, patient assessment, and techniques used in scar revision of the perioral region.

Functional connectivity patterns of normal human swallowing: difference among various viscosity swallows in normal and chin-tuck head positions.

Consuming thicker fluids and swallowing in the chin-tuck position has been shown to be advantageous for some patients with neurogenic dysphagia who aspirate due to various causes. The anatomical changes caused by these therapeutic techniques are well known, but it is unclear whether these changes alter the cerebral processing of swallow-related sensorimotor activity. We sought to investigate the effect of increased fluid viscosity and chin-down posture during swallowing on brain networks. 55 healthy adults performed water, nectar-thick, and honey thick liquid swallows in the neutral and chin-tuck positions while EEG signals were recorded. After pre-processing of the EEG timeseries, the time-frequency based synchrony measure was used for forming the brain networks to investigate whether there were differences among the brain networks between the swallowing of different fluid viscosities and swallowing in different head positions. We also investigated whether swallowing under various conditions exhibit small-world properties. Results showed that fluid viscosity affects the brain network in the Delta, Theta, Alpha, Beta, and Gamma frequency bands and that swallowing in the chin-tuck head position affects brain networks in the Alpha, Beta, and Gamma frequency bands. In addition, we showed that swallowing in all tested conditions exhibited small-world properties. Therefore, fluid viscosity and head positions should be considered in future swallowing EEG investigations.

The effectiveness of the head-turn-plus-chin-down maneuver for eliminating vallecular residue.

Purpose When swallowing efficiency is impaired, residue accumulates in the pharynx. Cued or spontaneous swallows in the head neutral position do not always successfully clear residue. We investigated the impact of a novel maneuver on residue clearance by combining a head turn with the chin down posture. Methods Data were collected from 26 participants who demonstrated persistent vallecular residue after an initial head neutral clearance swallow in videofluoroscopy. Participants were cued to perform a head-turn-plus-chin-down swallow, with the direction of head turn randomized. Pixel-based measures of residue in the vallecular space before and after the maneuver were made on still frame lateral images using ImageJ software. Measures of % full and the Normalized Residue Ratio Scale (NRRS) were extracted. Univariate analyses of variance were used to detect significant reductions in residue. Results On average, pre-maneuver measures showed residue filling 56-73% of the valleculae, depending on stimulus consistency (NRRS scores: 0.2-0.4). More than 80% of pre-swallow measures displayed NRRS ratios > 0.06, a threshold previously linked to increased risk of post-swallow aspiration. Conclusion The head-turn-plus-chin-down maneuver achieved significant reductions in residue for thin and nectar-thick fluids, suggesting that this maneuver can be effective in reducing persistent vallecular residue with these consistencies.

Optimal chin-brow vertical angle for sagittal visual fields in ankylosing spondylitis kyphosis.

PURPOSE: Chin-brow vertical angle (CBVA) is very important in correction of thoracolumbar kyphotic deformity in ankylosing spondylitis (AS), especially for the patients with cervical ankylosis. In previous study, Suk et al. stated that the patients with CBVA between -10° and 10° had better horizontal gaze. Unfortunately, in our clinical practice, we found the patients with CBVA between -10° and 10° after surgery usually complained of difficulty in cooking, cleaning, desk working and the like, although they had excellent horizontal gaze. In other words, for the patients with cervical ankylosis, good horizontal gaze existed together with poor downward gaze. Then, which condition do the patients prefer? Is there a compromise solution that makes a better quality life possible for the patients? In this research, we studied AS patients with cervical ankylosis, aiming to investigate the optimal CBVA for deformity correction. METHODS: 25 AS thoracolumbar kyphotic patients with cervical ankylosis were studied, whose function and expectation of visual field related to life quality were assessed by questionnaire before and after surgery. Pre- and post-operative CBVA were obtained on lateral photos of the patients with free-standing posture, and 50 cases of CBVA were included, which were divided into six groups according to the angle irrespective of surgery (Group A, CBVA <0°; Group B, 0° ≤ CBVA < 10°; Group C, 10° ≤ CBVA < 20°; Group D, 20° ≤ CBVA < 30°; Group E, 30° ≤ CBVA < 40°; Group F, CBVA ≥ 40°). Kruskal-Wallis test was used to assess all the groups in terms of various items in the questionnaire, while Mann-Whitney test was used to assess every two groups. RESULTS: In overall evaluation, Group C (10°-20°) obtained the optimal expectation (p < 0.05); Group B, C and D (0°-30°) obtained better function (p < 0.05), and there was no significant difference between the 3 groups. In appearance, Group A, B and C (<20°) were better than the other groups both in function and expectation (p < 0.05), without dramatic difference among the three groups. In outdoor activities, Group A, B, C and D (<30°) were better in most of the items (p < 0.05). In indoor activities, Group C and D (10-30°) were much better (p < 0.05). CONCLUSION: AS thoracolumbar kyphotic patients with cervical ankylosis had the best satisfaction when 10° ≤ CBVA < 20°.

The effectiveness of the head-turn-plus-chin-down maneuver for eliminating vallecular residue

ABSTRACT Purpose When swallowing efficiency is impaired, residue accumulates in the pharynx. Cued or spontaneous swallows in the head neutral position do not always successfully clear residue. We investigated the impact of a novel maneuver on residue clearance by combining a head turn with the chin down posture. Methods Data were collected from 26 participants who demonstrated persistent vallecular residue after an initial head neutral clearance swallow in videofluoroscopy. Participants were cued to perform a head-turn-plus-chin-down swallow, with the direction of head turn randomized. Pixel-based measures of residue in the vallecular space before and after the maneuver were made on still frame lateral images using ImageJ software. Measures of % full and the Normalized Residue Ratio Scale (NRRS) were extracted. Univariate analyses of variance were used to detect significant reductions in residue. Results On average, pre-maneuver measures showed residue filling 56-73% of the valleculae, depending on stimulus consistency (NRRS scores: 0.2-0.4). More than 80% of pre-swallow measures displayed NRRS ratios > 0.06, a threshold previously linked to increased risk of post-swallow aspiration. Conclusion The head-turn-plus-chin-down maneuver achieved significant reductions in residue for thin and nectar-thick fluids, suggesting that this maneuver can be effective in reducing persistent vallecular residue with these consistencies.

The enduring puzzle of the human chin.

Although modern humans are considered to be morphologically distinct from other living primates because of our large brains, dexterous hands, and bipedal gait, all of these features are found among extinct hominins. The chin, however, appears to be a uniquely modern human trait. Probably because of the chin's exclusivity, many evolutionary scenarios have been proposed to explain its origins. To date, researchers have developed adaptive hypotheses relating chins to speech, mastication, and sexual selection; still others see it as a structural artifact tangentially related to complex processes involving evolutionary retraction of the midfacial skeleton. Consensus has remained elusive, partly because hypotheses purporting to explain how this feature developed uniquely in modern humans are all fraught with theoretical and/or empirical shortcomings. Here we review a century's worth of chin hypotheses and discuss future research avenues that may provide greater insight into this human peculiarity.

Symphyseal surface strain during in vitro human mandibular wishboning.

OBJECTIVES: This research theoretically models and empirically records symphyseal surface strain during in vitro human mandibular wishboning (lateral transverse bending) in order to test one aspect of the hypothesis that the chin is an adaptive response to masticatory stresses. From a perspective of optimality, three questions were tested: 1) Do human mandibles function as curved beams during wishboning? 2) Is the presence of a chin associated with lower than predicted curved beam effects? 3) Are there relatively low strain gradients on the lingual and labial symphyseal surfaces respectively? MATERIALS AND METHODS: Based on morphometric criteria, theoretical wishboning strains were calculated for five dentate adult human mandibles. The same mandibles were fitted with strain gauges and subjected to simulated wishboning loads. From the empirically-recorded strains, relative strains were calculated by dividing all strains by the absolute lowest strain in a given specimen. The theoretical and empirical results were compared in order to address the three related questions guiding this research. RESULTS: Human mandibles behave as curved beams during wishboning (question 1). Empirical strain measures showed greater disparity both between and within the labial and lingual symphyseal surfaces than the theoretical models predictions (questions 2 and 3). DISCUSSION: Human symphyseal form, with its distinctive chin, is unlikely to be adapted for countering wishboning loads. Chins are associated with larger than expected strain gradients within and between symphyseal surfaces, which runs counter to the optimality criterion typically invoked in assessing trait performance for signs of adaptation. The implications are twofold: 1) wishboning may not, in fact, be a regular feature of human mastication or 2) wishboning may not pose the same structural risks in human jaws as this load does in other anthropoid primates.

Comparison between an automatic and a visual scoring method of the chin muscle tone during rapid eye movement sleep.

OBJECTIVE: To compare two different methods, one visual and the other automatic, for the quantification of rapid eye movement (REM) sleep without atonia (RSWA) in the diagnosis of REM sleep behavior disorder (RBD). METHODS: Seventy-four RBD patients (mean age, 62.14±9.67 years) and 75 normal controls (mean age, 61.04±12.13 years) underwent one night video-polysomnographic recording. The chin electromyogram (EMG) during REM sleep was analyzed by means of a previously published visual method quantifying the percentage of 30s epochs scored as tonic (abnormal, > or =30%) and that of 2s mini-epochs containing phasic EMG events (abnormal, > or =15%). For the computer quantitative analysis we used the automatic scoring algorithm known as the atonia index (abnormal, <0.8). The percentage correct classification, sensitivity, specificity, and Cohen kappa were calculated. RESULTS: The atonia index correctly classified 82.6% of subjects, similar to the percentage of correct classifications with individual components of the visual analysis (83.2% each for tonic and phasic), and the combined visual parameters (85.9%). The sensitivity and specificity of automatic analysis (84% and 81%) was similar to the combined visual analysis (89% and 83%). The correlation coefficient between the automatic atonia index and the percentage of visual tonic EMG was high (r = -0.886, P<0.00001), with moderately high correlation with the percentage of phasic EMG (r = -0.690, P<0.00001). The agreement between atonia index and the visual parameters (individual or combined) was approximately 85% with Cohen's kappa, ranging from 0.638 to 0.693. CONCLUSION: Sensitivity, specificity, and correct classifications were high with both methods. Moreover, there was general agreement between methods, with Cohen's kappa values in the 'good' range. Given the considerable practical advantages of automatic quantification of REM atonia, automatic quantification may be a useful alternative to visual scoring methods in otherwise uncomplicated polysomnograms.

Short faces, big tongues: developmental origin of the human chin.

During the course of human evolution, the retraction of the face underneath the braincase, and closer to the cervical column, has reduced the horizontal dimension of the vocal tract. By contrast, the relative size of the tongue has not been reduced, implying a rearrangement of the space at the back of the vocal tract to allow breathing and swallowing. This may have left a morphological signature such as a chin (mental prominence) that can potentially be interpreted in Homo. Long considered an autopomorphic trait of Homo sapiens, various extinct hominins show different forms of mental prominence. These features may be the evolutionary by-product of equivalent developmental constraints correlated with an enlarged tongue. In order to investigate developmental mechanisms related to this hypothesis, we compare modern 34 human infants against 8 chimpanzee fetuses, whom development of the mandibular symphysis passes through similar stages. The study sets out to test that the shared ontogenetic shape changes of the symphysis observed in both species are driven by the same factor--space restriction at the back of the vocal tract and the associated arrangement of the tongue and hyoid bone. We apply geometric morphometric methods to extensive three-dimensional anatomical landmarks and semilandmarks configuration, capturing the geometry of the cervico-craniofacial complex including the hyoid bone, tongue muscle and the mandible. We demonstrate that in both species, the forward displacement of the mental region derives from the arrangement of the tongue and hyoid bone, in order to cope with the relative horizontal narrowing of the oral cavity. Because humans and chimpanzees share this pattern of developmental integration, the different forms of mental prominence seen in some extinct hominids likely originate from equivalent ontogenetic constraints. Variations in this process could account for similar morphologies.

The effect of bone displacement operations on facial soft tissues.

A novel biomechanical model for face soft tissue (skin, mucosa, and muscles) is introduced to investigate the effect of mandible and chin bone displacement on the overall appearance of the patient's face. Nonlinear FE analysis is applied to the model and the results obtained are used to help surgeons to decide the amount of displacement required.