Determining the Relationship Between Hyoid Bone Kinematics and Airway Protection in Swallowing

Purpose: Research remains equivocal regarding the links between hyoid movement and penetration–aspiration. The aims of this study were (a) to explore associations between hyoid parameters, laryngeal vestibule closure (LVC) parameters, and penetration–aspiration on thin liquids; and (b) to determine which of these parameters are the strongest predictors of penetration–aspiration. Method: This study involved retrospective analysis of an existing videofluoroscopy data set, collected in 305 participants (152 males) with noncongenital/nonsurgical/non-oncological risk for dysphagia. We extracted data for six thin liquid swallows per participant, and obtained measures of hyoid movement (peak position, speed) and LVC (complete/incomplete, timing, duration). Resulting values were coded as typical/atypical relative to healthy reference data. Relationships were explored using chi-square tests and odds ratios (a) for the entire data set and (b) for the subset of data with complete LVC. Hierarchical logistic regression models determined the strongest predictors of penetration–aspiration. Results: Significant associations were found between penetration–aspiration and incomplete LVC, prolonged time-to-most-complete-LVC, short LVC duration, reduced anterior hyoid peak position, and reduced hyoid speed. Hyoid measures were also significantly associated with LVC parameters. In the first regression model, incomplete LVC and prolonged time-to-most-complete-LVC were the only significant predictors of penetration–aspiration. For cases with complete LVC, the only significant predictor was prolonged time-to-most-complete-LVC. Conclusions: Although reduced anterior hyoid peak position and speed are associated with penetration–aspiration on thin liquids, these measures do not independently account for penetration–aspiration when considered in conjunction with measures of LVC. When identifying mechanisms explaining penetration–aspiration, clinicians should focus on LVC (complete/incomplete) and timeliness of LVC.

Swallowing Kinematic Analysis Might Be Helpful In Predicting Aspiration And Pyriform Sinus Stasis

Aspiration and pyriform sinus stasis resulting from compromised swallowing might cause aspiration pneumonia, which can have a negative impact on the patient’s prognosis. Clinically, videofluoroscopic swallow study (VFSS) is considered the standard instrument that is able to provide clues that contribute to the physiological impairment of swallowing. In addition, according to previously published literature, the parameters of kinematic analyses of VFSS might provide further information for aspiration detection. In this study, 449 files of VFSS studies from 232 patients were divided into three groups: normal, aspiration, and pyriform sinus stasis. Kinematic analyses and between-group comparison were conducted. Significant between-group differences were noted among parameters, including anterior hyoid displacement, maximal hyoid displacement, and average velocity of hyoid movement. No significant difference was detected in superior hyoid displacement. Furthermore, receiver-operating characteristic (ROC) analyses using anterior hyoid displacement, velocity of anterior hyoid displacement, and average velocity of maximal hyoid displacement showed acceptable predictability for detecting aspiration. Using 33.0 mm/s as a cutoff value of average velocity of maximal hyoid displacement, the sensitivity of detecting the presence of aspiration could be about 90%. Therefore, we assumed that the average velocity of maximal hyoid displacement could be a potential screening tool to detect aspiration.

Compensatory Effects of Sequential 4-Channel Neuromuscular Electrical Stimulation for the Treatment of Acute, Subacute, and Chronic Dysphagia in a Prospective, Double-Blinded Randomized Clinical Trial

Background. The precise mechanism of 2-channel neuromuscular electrical stimulation (NMES) treatment is unknown, and controversy remains over its efficacy. The sequential 4-channel NMES was newly developed based on normal contractile sequences of swallowing-related muscles. Objective. To assess the clinical efficacy of sequential 4-channel NMES during swallowing. Methods. In this prospective RCT, 52 inpatients with dysphagia (acute, subacute, and chronic state) after stroke, brain tumor, or encephalitis were enrolled. Participants who underwent a videofluoroscopic swallowing study (VFSS) and clinical evaluation were enrolled and were randomly assigned to the 4-channel NMES or sham group. The 4-channel NMES and sham groups swallowed thin and honey-like fluids under NMES (sequential stimulation on suprahyoid and infrahyoid) and sham stimulation, respectively. The procedures were evaluated with the VFSS. Pre- and post-treatment evaluations were performed with the videofluoroscopic dysphagia scale (VDS), penetration–aspiration scale (PAS), Likert scale, and kinematic analysis. Results. The 4-channel NMES group showed significantly greater improvements than the sham group with respect to oral VDS, pharyngeal VDS, total VDS, and PAS ( P < .05). Furthermore, the Likert scale for satisfaction, easiness, and discomfort for swallowing showed favorable results for the 4-channel NMES group ( P < .05). In the kinematic analysis, the peak speed point, distance, and velocity of hyoid movement were significantly greater in the 4-channel NMES group ( P < .05). Conclusions. Sequential 4-channel NMES activating the suprahyoid, thyrohyoid, and other infrahyoid muscles during swallowing showed significant clinical improvement with respect to VDS, PAS, and kinematic analysis. Therefore, sequential 4-channel NMES is a potential new functional electrical stimulation system for the treatment of dysphagia.

Variations in Hyoid Kinematics Across Liquid Consistencies in Healthy Swallowing

Purpose Judgments regarding hyoid movement are frequently included in evaluations of swallowing. However, the literature lacks reference values for measures of hyoid kinematics in healthy swallowing. This study explores hyoid movement across the continuum from thin to extremely thick liquids. Method Participants were 39 healthy adults under the age of 60 years (19 men) who underwent videofluoroscopy involving three sips each of 20% w/v thin barium and six sips each of slightly, mildly, moderately, and extremely thick barium. Half of the thickened stimuli were prepared using xanthan gum; and half, with a starch-based thickener. Sip volume was derived from pre- and post-sip cup weights. Hyoid position was tracked frame-by-frame relative to the anterior–inferior corner of C4. Measures of peak hyoid position (along the XY axis) were normalized to a C2–C4 scalar, and measures of time-to-peak position, speed, and time-to-peak speed were derived. As a first step, Spearman's correlations confirmed the influence of sip volume on these hyoid measures. Linear mixed-effects models then explored the effects of stimulus, sip volume, and task repetition on the dependent variables. Results The data set comprised 975 swallows with available hyoid tracking data. Sip volume was correlated with peak hyoid XY position ( r s = .15, p < .01), time-to-peak position ( r s = −.15, p < .05), and speed ( r s = .13, p < .01). No significant differences in hyoid kinematics were found across stimuli. Conclusion Measures of hyoid movement in healthy swallowing remain stable across the range from thin to extremely thick liquids with no systematic alterations in hyoid position or kinematics.

Measuring Hyoid Excursion Across the Life Span: Anatomical Scaling to Control for Variation

Purpose A method for controlling for sex-based differences in measures of hyoid movement using an internal anatomical scalar has been validated in young healthy individuals. Known anatomical changes with aging necessitate validation of this methodology in a mixed-age sample. The primary aim of this study was to validate a method for controlling for sex-based differences in measures of hyoid movement across the life span. Measurement error as a potential source of variability was addressed to inform best practice recommendations. Method Two distinct data sets previously collected using identical protocols were combined for this study to achieve a data set of young (< 40 years) and older (> 65 years) healthy adults. Data included videofluoroscopic swallow studies with three swallow trials each of 5 and 20 ml thin liquid barium. Previously reported methodology was replicated to validate the use of an anatomical scalar for measuring hyoid excursion in this sample. Hyoid movement was measured using 2 methods (rest-to-peak displacement and peak only) in 3 planes of movement (anterior, superior, and hypotenuse), was expressed in millimeters and individually scaled units relative to C4, and normalized using the C2–C4 vertebral distance. Mixed-model repeated-measures analyses of variance were run with each of the 6 hyoid measures as the dependent variable (in both millimeters and C2–C4 units), within-subject factors of sex and bolus volume, and a between-subjects factor of age group. We predicted that the C2–C4 scalar would adequately control for sex-based differences across age groups. Results Significant differences in absolute hyoid movements (millimeters) were observed by sex, bolus volume, and age group. When measured in %C2–C4 units, all differences between males and females were neutralized. Significant differences between 5- and 20-ml boluses were found for all peak position measures. Significant differences between young and older individuals were found for all peak position measures. Conclusion Expressing hyoid excursion as a percentage of the C2–C4 distance appears valid for use across the life span. Peak position is preferable over displacement measures for quantifying hyoid excursion for research and clinical purposes.

Application of Automatic Kinematic Analysis Program for the Evaluation of Dysphagia in ALS patients

Dysphagia in amyotrophic lateral sclerosis (ALS) increases the risk of malnutrition, dehydration, and aspiration pneumonia. Kinematic analysis of videofluoroscopic swallowing study (VFSS) can provide detailed movement of the hyoid bone, revealing abnormalities of swallowing in ALS patients. We developed an automated kinematic analysis program (AKAP) that analyzes the trajectory of the hyoid bone via a visual tracking method. The aim of this study was to investigate the hyoid movement in ALS patients using AKAP and compare it with non-dysphagic subjects. Thirty ALS patients who underwent VFSS in Seoul National University Bundang Hospital between 2015 and 2017 were recruited. For comparison, 30 age-matched control subjects were also enrolled; the same swallowing study was conducted using thin fluid and yogurt. The hyoid bone movement was analyzed by evaluating the vertical and horizontal distances with four peak points (A, B, C, D), and the time of each point were also calculated. With respect to distance parameters, only vertical peak distance (distance between B, D points) during thin fluid swallowing was significantly decreased in ALS patients. (p = 0.038) With respect to temporal parameters, Time ABC, Time ABCD, and Duration C were significantly increased in ALS patients when swallowing both thin fluid and yogurt. (Time ABC p = 0.019, p = 0.002; Time ABCD p = 0.001, p = 0.004; Duration C p = 0.004, p = 0.025 respectively). This result revealed that dysphagia in ALS patient is caused by decreased velocity of hyoid bone movement due to the development of weakness in swallowing-related muscles. The parameters of kinematic analysis could be used to quantitatively evaluate dysphagia in motor neuron disease.

Functional Anatomy Underlying Pharyngeal Swallowing Mechanics and Swallowing Performance Goals

Purpose Rehabilitation of pharyngeal swallowing dysfunction requires a thorough understanding of the functional anatomy underlying the performance goals of pharyngeal swallowing. These goals include the safe and efficient transfer of a bolus through the hypopharynx into the esophagus. Penetration or aspiration of a bolus threatens swallowing safety. Bolus residue indicates swallowing inefficiency. Several primary mechanics, or elements of the swallowing mechanism, underlie these performance goals, with some elements contributing to both goals. These primary mechanics include velopharyngeal port closure, hyoid movement, laryngeal elevation, pharyngeal shortening, tongue base retraction, and pharyngeal constriction. Each element of the swallowing mechanism is under neuromuscular control and is therefore, in principle, a potential target for rehabilitation. Secondary mechanics of pharyngeal swallowing, those movements dependent on primary mechanics, include opening the upper esophageal sphincter and epiglottic inversion. Conclusion Understanding the functional anatomy of pharyngeal swallowing underlying swallowing performance goals will facilitate anatomically informed critical thinking in the rehabilitation of pharyngeal swallowing dysfunction.