Normal contractile algorithm of swallowing related muscles revealed by needle EMG and its comparison to videofluoroscopic swallowing study and high resolution manometry studies: A preliminary study

sEMG as complementary tool for VFSS: A synchronized study in patients with neurogenic oropharyngeal dysphagia

The neurogenic oropharyngeal dysphagia is a prevalent functional swallowing disorder resulting from neurological causes. The conventional diagnosis involves ionizing radiation in Videofluoroscopy Swallowing Studies (VFSS). Surface electromyography (sEMG) offers a non-invasive alternative by recording muscle activity. This research compares bolus passage timing through anatomical structures using VFSS and sEMG-related activation times. Fifty confirmed oropharyngeal dysphagia patients underwent synchronized VFSS and sEMG, evaluating muscle groups during cracker and fluid ingestion. sEMG revealed activation patterns in masseters, suprahyoid, and infrahyoid muscles, occurring before bolus passage through the mandibular line and concluding near the upper esophageal sphincter complex. sEMG identified differences in dysphagia severity (EAT-10 score), age, and diagnosis, contrasting VFSS results. Results indicate potential complementarity between sEMG and VFSS for dysphagia screening, diagnosis, and monitoring.

Normative High-Resolution Pharyngeal Manometry: Impact of Age, Size of System, and Sex on Primary Metrics and Pressure Stability

There have been many reports of normative pharyngeal swallowing pressures using high-resolution pharyngeal manometry, but there is a fair amount of between-subject variance in reported pressure parameters. The purpose of this study was to put forward normative pharyngeal high-resolution manometry measures across the lifespan and investigate the effects of age, size of system, and sex. High-resolution pharyngeal manometry was performed on 98 healthy adults (43 males) between the ages 21 and 89. Pressure duration, maxima, integral, and within-individual variability metrics were averaged over 10 swallows of 10-ml thin liquid. Multiple linear and logistic regressions with model fitting were used to examine how pharyngeal pressures relate to age, pharyngeal size, and sex. Age was associated with tongue base maximum pressure, tongue base maximum variability, and upper esophageal sphincter-integrated relaxation pressure (F3,92 = 6.69; p < 0.001; adjusted R2 = 0.15). Pharyngeal area during bolus hold was associated with velopharynx integral (F1,89 = 5.362; p = 0.02; adjusted R2 = 0.05), and there was no significant model relating pharyngeal pressures to C2-C4 length (p < 0.05). Sex differences were best described by tongue base integral and hypopharynx maximum variability (χ2 = 10.27; p = 0.006; pseudo R2 = 0.14). Normative data reveal the distribution of swallow pressure metrics which need to be accounted for when addressing dysphagia patients, the importance of pressure interactions in normal swallow, and address the relative stability of swallow metrics with normal aging.

Residual effect of sequential 4-channel neuromuscular electrical stimulation evaluated by high-resolution manometry

BACKGROUND

High-resolution manometry (HRM) can quantify swallowing pathophysiology to evaluate the status of the pharynx. Sequential 4-channel neuromuscular electrical stimulation (NMES) was recently developed based on the normal contractile sequences of swallowing-related muscles. This study aimed to examine the effects of sequential 4-channel NMES for compensatory application during swallowing and to observe the residual effects after the application of NMES using HRM.

RESULTS

Sequential 4-channel NMES significantly improved the HRM parameters, with respect to the maximal pressure and area of the velopharynx (VP), maximal pressure and area of the mesopharynx (MP), and upper esophageal sphincter (UES) activation and nadir duration. Furthermore, the improvement in the pressure and area variables of the VP and MP showed a tendency to maintain even when measured after NMES, but there are no significant differences.

CONCLUSIONS

The present study suggests that the sequential 4-channel NMES application of the suprahyoid and infrahyoid muscles during swallowing improves the pressure, area, and time variables of the oropharynx, as measured by HRM, and it is likely that the effects may persist even after stimulation. Trial Registration Clinicaltrials.gov, registration number: NCT02718963 (initial release: 03/20/2016, actual study completion date: 06/24/2016, last release: 10/20/2020).

Chemoradiation to the submental muscles alters hyoid movement during swallowing in a rat model

Hyolaryngeal dysfunction is a commonly reported swallowing problem after chemoradiation treatment for head and neck cancer. The displacement of the hyolaryngeal complex during swallowing protects the airway and assists in opening the upper esophageal sphincter. Activation of the submental muscles, specifically the mylohyoid and geniohyoid muscles, is thought to facilitate movement of the hyoid. The purpose of this study was to determine if targeted radiation to the submental muscles given concurrently with chemotherapy alters hyolaryngeal displacement 1 mo after treatment. We hypothesized that chemoradiation treatment would result in abnormal patterns of hyoid movement compared with controls. Furthermore, we propose that these changes are associated with alterations in bolus size and discoordination of the jaw during drinking. Eighteen rats underwent either chemoradiation, radiation, or no treatment. Radiation treatment was targeted to submental muscles using a clinical linear accelerator given in 12 fractions of 4 Gy (3 days per week). Cycles of 1 mg/kg of cisplatin were administered concurrently each week of radiation. One month posttreatment, videofluoroscopy swallow studies (VFSS) were performed in self-drinking rats using a fluoroscope customized with a high-speed camera. The hyoid, jaw, and hard palate were tracked during swallowing from VFSS. Hyoid kinematics were analyzed from the start to the end of hyoid movement, and parameters were compared with bolus size and jaw movement. Significant differences in hyoid retraction parameters were found postchemoradiation. Alterations in the trajectory of hyoid motion during swallowing were observed. The findings demonstrate early changes in hyoid motion during swallowing associated with chemoradiation treatment.NEW & NOTEWORTHY Chemoradiation treatment for head and neck cancer can cause functional impairments in swallowing, which can adversely affect quality of life. This study provides new evidence that chemoradiation targeted to the submental muscles provokes early adaptations in hyoid movement during swallowing, which correlate with changes in bolus size. We also demonstrate a method for tracking the hyoid during swallowing in a rat model of chemoradiation injury.

Advancements and Challenges in Non-Invasive Sensor Technologies for Swallowing Assessment: A Review

Dysphagia is a pervasive health issue that impacts diverse demographic groups worldwide, particularly the elderly, stroke survivors, and those suffering from neurological disorders. This condition poses substantial health risks, including malnutrition, respiratory complications, and increased mortality. Additionally, it exacerbates economic burdens by extending hospital stays and escalating healthcare costs. Given that this disorder is frequently underestimated in vulnerable populations, there is an urgent need for enhanced diagnostic and therapeutic strategies. Traditional diagnostic tools such as the videofluoroscopic swallowing study (VFSS) and flexible endoscopic evaluation of swallowing (FEES) require interpretation by clinical experts and may lead to complications. In contrast, non-invasive sensors offer a more comfortable and convenient approach for assessing swallowing function. This review systematically examines recent advancements in non-invasive swallowing function detection devices, focusing on the validation of the device designs and their implementation in clinical practice. Moreover, this review discusses the swallowing process and the associated biomechanics, providing a theoretical foundation for the technologies discussed. It is hoped that this comprehensive overview will facilitate a paradigm shift in swallowing assessments, steering the development of technologies towards more accessible and accurate diagnostic tools, thereby improving patient care and treatment outcomes.

Chronic intermittent hypoxia reveals role of the Postinspiratory Complex in the mediation of normal swallow production

Obstructive sleep apnea (OSA) is a prevalent sleep-related breathing disorder that results in multiple bouts of intermittent hypoxia. OSA has many neurological and systemic comorbidities, including dysphagia, or disordered swallow, and discoordination with breathing. However, the mechanism in which chronic intermittent hypoxia (CIH) causes dysphagia is unknown. Recently, we showed the postinspiratory complex (PiCo) acts as an interface between the swallow pattern generator (SPG) and the inspiratory rhythm generator, the preBötzinger complex, to regulate proper swallow-breathing coordination (Huff et al., 2023). PiCo is characterized by interneurons co-expressing transporters for glutamate (Vglut2) and acetylcholine (ChAT). Here we show that optogenetic stimulation of ChATcre:Ai32, Vglut2cre:Ai32, and ChATcre:Vglut2FlpO:ChR2 mice exposed to CIH does not alter swallow-breathing coordination, but unexpectedly disrupts swallow behavior via triggering variable swallow motor patterns. This suggests that glutamatergic-cholinergic neurons in PiCo are not only critical for the regulation of swallow-breathing coordination, but also play an important role in the modulation of swallow motor patterning. Our study also suggests that swallow disruption, as seen in OSA, involves central nervous mechanisms interfering with swallow motor patterning and laryngeal activation. These findings are crucial for understanding the mechanisms underlying dysphagia, both in OSA and other breathing and neurological disorders.

High-resolution manometry with impedance for the study of pharyngeal motility and the upper esophageal sphincter: Keys for its use in the study of the pathophysiology of oropharyngeal dysphagia

Oropharyngeal dysphagia (OD) is a pathology with a high prevalence in different patient phenotypes. High-resolution pharyngoesophageal manometry (HRPM) with impedance (HRPM-I) has become in recent years a fundamental technique for better understanding the pathophysiology of pharynx and upper oesophageal sphincter (UES) dysfunctions in patients with OD. Various groups of experts have proposed a methodology for the practice of the HRPM-I and for the standardization of the different metrics for the study of pharyngeal motility and UES dysfunctions based on the quantification of 3main phenomena: relaxation of the UES, resistance to flow through the UES and propulsion of the bolo through the pharynx into the oesophagus. According to the alterations of these metrics, 3patterns of dysfunction are proposed that allow a specific therapeutic approach: (a) UES flow restriction with normal pharyngeal propulsión; (b) UES flow restriction with ineffective pharyngeal propulsion, and (c) ineffective pharyngeal contraction with normal relaxation of the UES. We present a practical review of the methodology and metrics used by the main working groups together with the description of the main patterns of dysfunction according to our experience to highlight the usefulness of the HRPM-I in the study of the pathophysiology and selection of a specific treatment in patients with OD.

Kinematic mechanism of the rehabilitative effect of 4-channel NMES: post-hoc analysis of a prospective randomized controlled study

The sequential 4-channel neuromuscular electrical stimulation (NMES), based on the normal contractile sequences of swallowing-related muscles, is a new rehabilitative treatment. The objective of this study was to explore the mechanism of the rehabilitative effect of the 4-channel NMES using kinematic analysis of videofluoroscopic swallowing study (VFSS) data. For this post-hoc analysis, we included a subset of participants from the prospective randomized controlled study on the clinical effectiveness of the sequential 4-channel NMES compared with that of the conventional 2-channel NMES. Seventeen subjects (11 and six in the 4- and 2-channel NMES groups, respectively) were eligible for the kinematic analysis of VFSS data. The hyoid bone movement was analyzed by evaluating the distance and time parameters with four peak points (A, B, C, D). The 4-channel NMES group showed significant improvement in vertical distances (A-C), horizontal distance (A-B, A-C), time interval (A-B-C) and total time, compared with their pretreatment data. The 2-channel NMES group showed significant improvements in time interval (A-B); however, the Euclidean distance (A-D) and mean velocity of the Euclidean distance (A-C) were significantly decreased. When the two groups were directly compared, the 4-channel group showed significantly greater improvement in horizontal distance (A-B), Euclidean distance (A-D), time interval (A-B-C), and mean velocity the Euclidean distance (A-D). The results in this study suggest that the sequential 4-channel NMES might lead to the physiologic circular movement of the hyoid bone during swallowing, and therefore be an effective treatment for dysphagia.Trial registration: Clinicaltrials.gov, registration number: NCT03670498.

Toward a robust swallowing detection for an implantable active artificial larynx: a survey

Total laryngectomy consists in the removal of the larynx and is intended as a curative treatment for laryngeal cancer, but it leaves the patient with no possibility to breathe, talk, and swallow normally anymore. A tracheostomy is created to restore breathing through the throat, but the aero-digestive tracts are permanently separated and the air no longer passes through the nasal tracts, which allowed filtration, warming, humidification, olfaction, and acceleration of the air for better tissue oxygenation. As for phonation restoration, various techniques allow the patient to talk again. The main one consists of a tracheo-esophageal valve prosthesis that makes the air passes from the esophagus to the pharynx, and makes the air vibrate to allow speech through articulation. Finally, swallowing is possible through the original tract as it is now isolated from the trachea. Yet, many methods exist to detect and assess a swallowing, but none is intended as a definitive restoration technique of the natural airway, which would permanently close the tracheostomy and avoid its adverse effects. In addition, these methods are non-invasive and lack detection accuracy. The feasibility of an effective early detection of swallowing would allow to further develop an implantable active artificial larynx and therefore restore the aero-digestive tracts. A previous attempt has been made on an artificial larynx implanted in 2012, but no active detection was included and the system was completely mechanic. This led to residues in the airway because of the imperfect sealing of the mechanism. An active swallowing detection coupled with indwelling measurements would thus likely add a significant reliability on such a system as it would allow to actively close an artificial larynx. So, after a brief explanation of the swallowing mechanism, this survey intends to first provide a detailed consideration of the anatomical region involved in swallowing, with a detection perspective. Second, the swallowing mechanism following total laryngectomy surgery is detailed. Third, the current non-invasive swallowing detection technique and their limitations are discussed. Finally, the previous points are explored with regard to the inherent requirements for the feasibility of an effective swallowing detection for an artificial larynx. Graphical Abstract.

Synchronization between videofluoroscopic swallowing study and surface electromyography in patients with neurological involvement presenting symptoms of dysphagia

Introduction: Dysphagia is defined as the difficulty in transporting food and liquids from the mouth to the stomach. The gold standard to diagnose this condition is the videofluoroscopic swallowing study. However, it exposes patients to ionizing radiation. Surface electromyography is a non-radioactive alternative for dysphagia evaluation that records muscle electrical activity during swallowing. Objective: To evaluate the relationship between the relative activation times of the muscles involved in the oral and pharyngeal phases of swallowing and the kinematic events detected in the videofluoroscopy. Materials and methods: Electromiographic signals from ten patients with neurological involvement who presented symptoms of dysphagia were analyzed simultaneously with videofluoroscopy. Patients were given 5 ml of yogurt, 10 ml of water, and 3 g of crackers. Masseter, suprahyoid, and infrahyoid muscle groups were studied bilaterally. The bolus transit through the mandibular line, vallecula, and the cricopharyngeus muscle was analyzed in relation to the onset and offset times of each muscle group activation. Results: The average time of the pharyngeal phase was 0.89 ± 0.12 s. Muscle activation was mostly observed prior to the bolus transit through the mandibular line and vallecula. The end of the muscle activity suggested that the passage of the bolus through the cricopharyngeus muscle was almost complete. Conclusión: The muscle activity times, duration of the pharyngeal phase, and sequence of the muscle groups involved in swallowing were determined using sEMG validated with the videofluoroscopic swallowing study.

Usefulness of the Modified Videofluoroscopic Dysphagia Scale in Determining the Allowance of Oral Feeding in Patients with Dysphagia Due to Deconditioning or Frailty

Introduction: In patients with dysphagia due to deconditioning or frailty, as with other disorders that cause swallowing disorders, the videofluoroscopic swallowing study (VFSS) is the gold standard for dysphagia evaluation. However, the interpretation of VFSS results is somewhat complicated and requires considerable experience in the field. Therefore, in this study we evaluated the usefulness of the modified videofluoroscopic dysphagia scale (mVDS) in determining whether to allow oral feeding in patients with dysphagia due to deconditioning or frailty. Methods: Data from the VFSS of 50 patients with dysphagia due to deconditioning or frailty were retrospectively collected. We evaluated the association between mVDS and the selected feeding method based on VFSS findings, and between mVDS and the presence of aspiration pneumonia. Results: Multivariate logistic analysis showed that the mVDS total score had a significant association with oral feeding methods based on VFSS findings in patients with dysphagia due to deconditioning or frailty (p < 0.05). In the receiver operating characteristic (ROC) curve analysis, the area under the ROC curve for the selected feeding method was 0.862 (95% confidence interval, 0.747−0.978; p < 0.0001). Conclusions: mVDS seems a valid scale for determining the allowance of oral feeding, and it can be a useful tool in the clinical setting and in studies that aim to interpret VFSS findings in patients with dysphagia due to deconditioning or frailty. However, studies involving a more general population of patients with dysphagia due to deconditioning or frailty are needed.

Deep Learning Analysis to Automatically Detect the Presence of Penetration or Aspiration in Videofluoroscopic Swallowing Study

BACKGROUND

Videofluoroscopic swallowing study (VFSS) is currently considered the gold standard to precisely diagnose and quantitatively investigate dysphagia. However, VFSS interpretation is complex and requires consideration of several factors. Therefore, considering the expected impact on dysphagia management, this study aimed to apply deep learning to detect the presence of penetration or aspiration in VFSS of patients with dysphagia automatically.

METHODS

The VFSS data of 190 participants with dysphagia were collected. A total of 10 frame images from one swallowing process were selected (five high-peak images and five low-peak images) for the application of deep learning in a VFSS video of a patient with dysphagia. We applied a convolutional neural network (CNN) for deep learning using the Python programming language. For the classification of VFSS findings (normal swallowing, penetration, and aspiration), the classification was determined in both high-peak and low-peak images. Thereafter, the two classifications determined through high-peak and low-peak images were integrated into a final classification.

RESULTS

The area under the curve (AUC) for the validation dataset of the VFSS image for the CNN model was 0.942 for normal findings, 0.878 for penetration, and 1.000 for aspiration. The macro average AUC was 0.940 and micro average AUC was 0.961.

CONCLUSION

This study demonstrated that deep learning algorithms, particularly the CNN, could be applied for detecting the presence of penetration and aspiration in VFSS of patients with dysphagia.

The effect of the Shaker head‐lift exercise on swallowing function following treatment for head and neck cancer: Results from a randomized, controlled trial with videofluoroscopic evaluation

Background

Dysphagia is common following treatment for head and neck cancer (HNC) and intervention to improve swallowing function is warranted. This study aimed to evaluate the efficacy of the Shaker head‐lift exercise (HLE) to improve dysphagia in HNC patients.

Methods

Patients treated for HNC with radiochemotherapy and with subsequent dysphagia were randomly assigned to intervention (HLE, n = 25) and control (standard dysphagia management, n = 27) groups. Videofluoroscopic evaluation of penetration‐aspiration, initiation, residue, movement of selected structures, and self‐perceived swallowing function, before and after 8 weeks of treatment, were compared.

Results

Although adherence to training was high, no statistically significant differences in objectively measured swallowing function between the groups or within‐group changes were found. Self‐perceived swallowing function improved in the intervention group.

Conclusions

In this HNC population, neither HLE nor standard dysphagia management improved objectively measured swallowing function as evaluated after 8 weeks. Future research focusing on finding effective interventions for dysphagia is warranted.

Validation and Inter-rater Reliability of the Modified Videofluoroscopic Dysphagia Scale (mVDS) in Dysphagic Patients with Multiple Etiologies

BACKGROUND

the Videofluoroscopic Dysphagia Scale (VDS) is used to interpret and predict the long-term prognosis of patients with dysphagia. However, the inter-rater agreement of the VDS was shown to be lower in a previous study. To overcome the mentioned limitation of the VDS, a modified version (mVDS) was created and applied clinically. We aimed to validate its usefulness in determining the appropriate feeding method and predicting the prognosis of dysphagia.

METHODS

the videofluroscopic swallowing study (VFSS) data of 50 patients with dysphagia were collected retrospectively. The VFSS data were evaluated using the mVDS, and the inter-rater reliability was calculated. We also evaluated the association between the mVDS and type of feeding method selected, and between the mVDS and presence of aspiration pneumonia in patients with dysphagia.

RESULTS

among the different parameters of mVDS, "aspiration" showed the highest reliability (k = 0.767), followed by "mastication" and "lip closure" (k = 0.648 and k = 0.634, respectively). Conversely, "triggering pharyngeal swallow" and "pyriformis residue" demonstrated the lowest reliabilities (k = 0.312 and k = 0.324, respectively). The intraclass correlation coefficient (ICC), which is used as a measure of the reliability of the total mVDS score, was 0.876. In all patients with dysphagia, the mVDS score correlated significantly with the type of feeding method selected (p < 0.05), and the presence of aspiration pneumonia (p < 0.05).

CONCLUSION

the ICC of the total mVDS score was 0.876. Therefore, the mVDS could be a useful tool for quantifying the severity of dysphagia. It could be helpful in the analysis of the VFSS findings among patients with dysphagia in clinical settings and research.

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.

Clinical effectiveness of the sequential 4-channel NMES compared with that of the conventional 2-channel NMES for the treatment of dysphagia in a prospective double-blind randomized controlled study

Background

To date, conventional swallowing therapies and 2-channel neuromuscular electrical stimulation (NMES) are standard treatments for dysphagia. The precise mechanism of 2-channel NMES treatment has not been determined, and there are controversies regarding the efficacy of this therapy. The sequential 4-channel NMES was recently developed and its action is based on the normal contractile sequence of swallowing-related muscles.

Objective

To evaluate and compare the rehabilitative effectiveness of the sequential 4-channel NMES with that of conventional 2-channel NMES.

Methods

In this prospective randomized case–control study, 26 subjects with dysphagia were enrolled. All participants received 2- or 4-channel NMES for 2–3 weeks (minimal session: 7 times, treatment duration: 300–800 min). Twelve subjects in the 4-channel NMES group and eleven subjects in the 2-channel NMES group completed the intervention. Initial and follow-up evaluations were performed using the videofluoroscopic dysphagia scale (VDS), the penetration-aspiration scale (PAS), the MD Anderson dysphagia inventory (MDADI), the functional oral intake scale (FOIS), and the Likert scale.

Results

The sequential 4-channel NMES group experienced significant improvement in their VDS (oral, pharyngeal, and total), PAS, FOIS, and MDADI (emotional, functional, and physical subsets) scores, based on their pretreatment data. VDS (oral, pharyngeal, and total) and MDADI (emotional and physical subsets) scores, but not PAS and FOIS scores, significantly improved in the 2-channel NMES group posttreatment. When the two groups were directly compared, the 4-channel NMES group showed significant improvement in oral and total VDS scores.

Conclusions

The sequential 4-channel NMES, through its activation of the suprahyoid and thyrohyoid muscles, and other infrahyoid muscles mimicking physiological activation, may be a new effective treatment for dysphagia.

Trial registration: clinicaltrial.gov, registration number: NCT03670498, registered 13 September 2018, https://clinicaltrials.gov/ct2/show/NCT03670498?term=NCT03670498&draw=2&rank=1.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12984-021-00884-6.

Submandibular Push Exercise Using Visual Feedback from a Pressure Sensor in Patients with Swallowing Difficulties: A Pilot Study

Objectives: We aimed to determine the usefulness and effectiveness of a submandibular push exercise with visual feedback from a pressure sensor in patients with dysphagia through continuous exercise sessions. Methods: Twelve patients with dysphagia of various etiologies were included. A total of five exercise sessions (every 3 or 4 days) over three weeks were conducted. During the submandibular push exercise, patients were instructed to maintain a maximum force for 3 s, repeated for 1 min to measure the number of exercises, the maximum pressure, and the area of the pressure-time graph. We statistically compared the values of each exercise trial. Results: Among the 12 patients, eight completed the exercise sessions. As the number of exercise trials increased, the maximum pressure and the area in the pressure-time graph showed a significant increase compared to the previous attempt (p < 0.05). The maximum pressure and the area of the pressure-time graph improved from the first to the fourth session (p < 0.05). The values were maintained after the fourth session, and there was no significant difference between the fourth and the fifth exercise (p > 0.05). There was no significant difference between successful and non-successful groups, except for the Modified Barthel Index (p < 0.05). Conclusion: Through repetitive exercise training, the submandibular push exercise using visual feedback from a pressure sensor can be applied as an exercise method to strengthen swallowing related muscles, such as the suprahyoid and infrahyoid muscles. However, additional studies including more patients and a long-term study period are warranted to evaluate the effects of the exercise for improvement of dysphagia.

Comparison of three different types of exercises for selective contractions of supra- and infrahyoid muscles

Several exercise methods, such as the Shaker exercise, tongue press exercise, chin tuck against resistance (CTAR) exercise, and submandibular push exercise, have been introduced to strengthen the muscles involved in swallowing. In this study, we compared the effectiveness of the CTAR, submandibular push, and Shaker exercises for the induction of selective supra- and infrahyoid muscle contractions using surface electromyography (EMG). This study is a prospective non-randomized controlled study. Twenty-five healthy subjects and 20 patients experiencing swallowing difficulty were enrolled. During the three different types of exercises, the root mean square (RMS) values of the sternocleidomastoid (SCM), suprahyoid (anterior belly of the digastric and mylohyoid muscles), and infrahyoid (sternothyroid and thyrohyoid muscles) muscles were analyzed using surface EMG. Differences in the activity of swallowing muscles among the three different exercises were analyzed using one-way repeated measured analysis of variance. In terms of both the maximum and mean RMS values of the suprahyoid muscle, the submandibular push exercise showed a larger RMS value than the CTAR and Shaker exercises in healthy subjects (p < 0.05). In terms of both the maximum and mean RMS values of the suprahyoid muscle, the Shaker exercise and submandibular push exercise showed a larger RMS value than the CTAR exercise in patients with swallowing difficulty (p < 0.05). The submandibular push exercise may be effective as a swallowing muscle exercise owing to its superiority in inducing selective contractions of the supra- and infrahyoid muscles. The CTAR and Shaker exercises are also effective in this regard.

Electromyographic activation patterns during swallowing in older adults

Age-related weakness due to atrophy and fatty infiltration in oropharyngeal muscles may be related to dysphagia in older adults. However, little is known about changes in the oropharyngeal muscle activation pattern in older adults. This was a prospective and experimental study. Forty healthy participants (20 older [> 60 years] and 20 young [< 60 years] adults) were enrolled. Six channel surface electrodes were placed over the bilateral suprahyoid (SH), bilateral retrohyoid (RH), thyrohyoid (TH), and sternothyroid (StH) muscles. Electromyography signals were then recorded twice for each patient during swallowing of 2 cc of water, 5 cc of water, and 5 cc of a highly viscous fluid. Latency, duration, and peak amplitude were measured. The activation patterns were the same, in the order of SH, TH, and StH, in both groups. The muscle activation patterns were classified as type I and II; the type I pattern was characterized by a monophasic shape, and the type II comprised a pre-reflex phase and a main phase. The oropharyngeal muscles and SH muscles were found to develop a pre-reflex phase specifically with increasing volume and viscosity of the swallowed fluid. Type I showed a different response to the highly viscous fluid in the older group compared to that in the younger group. However, type II showed concordant changes in the groups. Therefore, healthy older people were found to compensate for swallowing with a pre-reflex phase of muscle activation in response to increased liquid volume and viscosity, to adjust for age-related muscle weakness.

Examining the Relationships Between Lingual Strength, Perihyoid Strength, and Swallowing Kinematics in Dysphagic Adults: A Retrospective Cross-Sectional Analysis

Purpose The aim of this study was to examine the relationships of clinical measures of lingual and perihyoid strength with displacement swallowing kinematics and swallowing safety in a heterogenous group of dysphagic adults. Method A retrospective analysis was completed of videofluoroscopic swallow studies of consecutive dysphagic outpatient adults presenting to a tertiary swallowing center from January 1, 2015, to December 31, 2017. Videofluoroscopic swallow study records were included if containing displacement swallowing kinematics of a 20-ml single liquid swallow and clinical measures of anterior (L-MIPA) or posterior (L-MIPP) lingual maximal isometric press, saliva mean swallowing pressures (S-MSP), and/or open mouth-maximal isometric press (OM-MIP). Regression analyses were used to examine the relationships between clinical measures of lingual (L-MIPA, L-MIPP, S-MSP) and perihyoid (OM-MIP) strength and displacement swallowing kinematics, and binomial logistic regressions were used to examine the relationships between clinical measures of lingual and perihyoid strength and swallowing safety (Penetration-Aspiration Scale [PAS]). Results Multivariate regressions revealed significant relationships of L-MIPA, L-MIPP, S-MSP, and OM-MIP with group-level changes to the displacement swallowing kinematics. Univariate analyses revealed significant relationships of L-MIPA and L-MIPP with pharyngeal constriction ratio, maximal extent of upper esophageal segment opening, and PAS. Conclusions Weak relationships were identified of clinical measures of lingual and perihyoid strength with displacement swallowing kinematics. These findings suggest that clinical measures of lingual and perihyoid strength do not fully explain impairments in swallowing kinematics across a heterogenous group of dysphagic patients. Weak-to-moderate relationships were identified between clinical measures of lingual strength and PAS, suggesting that they may have value in predicting functional measures of swallowing safety. Further research is needed to examine how findings may differ between specific patient populations.

Clinical Association Between Nasopharyngeal Reflux and Aspiration

Nasopharyngeal reflux (NPR) is a disturbing phenomenon which interferes swallowing, and the occurrence of NPR is known to be related to aspiration prevalence. The aim of this study is to verify a hypothesis that aspiration will occur more severely in patients with severe NPR, and when it occurs before NPR. Through 2650 video review of videofluoroscopic swallowing study (VFSS) conducted between January 2013 and July 2017 in a tertiary hospital, 100 patients who presented with NPR (NPR group) and age/sex-matched 100 non-NPR patients were screened. The severities of NPR and that of aspiration were analyzed by using final refluxed space and Penetration-Aspiration Scale (PAS) scores. The mean PAS score was significantly higher in the NPR group than in the non-NPR group (p = 0.01). The mean PAS score was significantly high in patients who had a higher NPR grade (p < 0.01). The PAS score was higher when aspiration occurred before NPR (p = 0.02), whereas NPR was more severe when NPR preceded aspiration (p = 0.01). A high index of suspicion is necessary in patients with regurgitating symptom toward the nasopharynx and nasal cavity. Since the severity of the NPR and that of aspiration may differ according to the order of occurrence, biomechanical study through VFSS is important.

Effect of the submandibular push exercise using visual feedback from pressure sensor: an electromyography study

We developed a new exercise method called the submandibular push exercise that can strengthen the suprahyoid muscle by inducing only the motion of the hyoid bone without neck flexion. In this study, we aimed to investigate and compare the muscle activity of the suprahyoid and infrahyoid muscles in the course of performing three different swallowing exercises. Twenty healthy participants and fifteen patients with dysphagia were recruited. Each participant consecutively performed three exercises: Shaker, CTAR, and submandibular push exercises. To investigate muscle activation, surface electromyography was performed on the suprahyoid, infrahyoid, and SCM muscles, during the exercises. Root mean square (RMS) was measured. In healthy participants, the submandibular push exercise showed a significantly higher RMS value in the suprahyoid and infrahyoid muscles than the Shaker and CTAR exercises using repeated ANOVA with Tukey's post hoc test (p < 0.05). In patients with dysphagia, the submandibular push and Shaker exercises showed significantly higher RMS value in the suprahyoid and infrahyoid muscles than the CTAR exercise. However, no significant difference was found between the submandibular push and Shaker exercises. In both healthy and patients with dysphagia, the mean RMS values of the SCM muscles during the submandibular push exercise were significantly lower than those during the Shaker exercise using repeated ANOVA with Tukey's post hoc test (p < 0.05). In conclusion, considering the relatively superior selectiveness in suprahyoid and infrahyoid muscle contraction, the submandibular push exercise using visual feedback from pressure sensor could be an efficient supplementary exercise to the conventional swallowing muscle exercises. However, further studies may be necessary to confirm the improvement in swallowing difficulty.

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.

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.

Using Wearable and Non-Invasive Sensors to Measure Swallowing Function: Detection, Verification, and Clinical Application

BACKGROUND

A widely used method for assessing swallowing dysfunction is the videofluoroscopic swallow study (VFSS) examination. However, this method has a risk of radiation exposure. Therefore, using wearable, non-invasive and radiation-free sensors to assess swallowing function has become a research trend. This study addresses the use of a surface electromyography sensor, a nasal airflow sensor, and a force sensing resistor sensor to monitor the coordination of respiration and larynx movement which are considered the major indicators of the swallowing function. The demand for an autodetection program that identifies the swallowing patterns from multiple sensors is raised. The main goal of this study is to show that the sensor-based measurement using the proposed detection program is able to detect early-stage swallowing disorders, which specifically, are useful for the assessment of the coordination between swallowing and respiration.

METHODS

Three sensors were used to collect the signals from submental muscle, nasal cavity, and thyroid cartilage, respectively, during swallowing. An analytic swallowing model was proposed based on these sensors. A set of temporal parameters related to the swallowing events in this model were defined and measured by an autodetection algorithm. The verification of this algorithm was accomplished by comparing the results from the sensors with the results from the VFSS. A clinical application of the long-term smoking effect on the swallowing function was detected by the proposed sensors and the program.

RESULTS

The verification results showed that the swallowing patterns obtained from the sensors strongly correlated with the laryngeal movement monitored from the VFSS. The temporal parameters measured from these two methods had insignificant delays which were all smaller than 0.03 s. In the smoking effect application, this study showed that the differences between the swallowing function of smoking and nonsmoking participants, as well as their disorders, is revealed by the sensor-based method without the VFSS examination.

CONCLUSIONS

This study showed that the sensor-based non-invasive measurement with the proposed detection algorithm is a viable method for temporal parameter measurement of the swallowing function.

High-Resolution Pharyngeal Manometry and Impedance: Protocols and Metrics-Recommendations of a High-Resolution Pharyngeal Manometry International Working Group

High-resolution manometry has traditionally been utilized in gastroenterology diagnostic clinical and research applications. Recently, it is also finding new and important applications in speech pathology and laryngology practices. A High-Resolution Pharyngeal Manometry International Working Group was formed as a grass roots effort to establish a consensus on methodology, protocol, and outcome metrics for high-resolution pharyngeal manometry (HRPM) with consideration of impedance as an adjunct modality. The Working Group undertook three tasks (1) survey what experts were currently doing in their clinical and/or research practice; (2) perform a review of the literature underpinning the value of particular HRPM metrics for understanding swallowing physiology and pathophysiology; and (3) establish a core outcomes set of HRPM metrics via a Delphi consensus process. Expert survey results were used to create a recommended HRPM protocol addressing system configuration, catheter insertion, and bolus administration. Ninety two articles were included in the final literature review resulting in categorization of 22 HRPM-impedance metrics into three classes: pharyngeal lumen occlusive pressures, hypopharyngeal intrabolus pressures, and upper esophageal sphincter (UES) function. A stable Delphi consensus was achieved for 8 HRPM-Impedance metrics: pharyngeal contractile integral (CI), velopharyngeal CI, hypopharyngeal CI, hypopharyngeal pressure at nadir impedance, UES integrated relaxation pressure, relaxation time, and maximum admittance. While some important unanswered questions remain, our work represents the first step in standardization of high-resolution pharyngeal manometry acquisition, measurement, and reporting. This could potentially inform future proposals for an HRPM-based classification system specifically for pharyngeal swallowing disorders.

Feasibility of high-resolution manometry for decision of feeding methods in patients with amyotrophic lateral sclerosis

As amyotrophic lateral sclerosis (ALS) progresses, dysphagia gets worse due to the weakening of pharyngeal musculature. As oral feeding becomes more difficult or dangerous due to worsening dysphagia, tracheal aspiration, or undernutrition, the necessity for tube feeding becomes increasingly important. This study aims to establish a standard pressure point by applying pharyngeal pressure using high-resolution manometry (HRM) to start tube feeding in patients with ALS.This study was designed as a retrospective analysis of prospectively collected data. Forty-one patients with ALS and 20 healthy subjects were participated. Both groups were evaluated using HRM, videofluoroscopic swallowing study (VFSS), and pulmonary function test. The swallowing pressure along the velopharynx (VP), tongue base (TB), pre-upper esophageal sphincter (UES), lower pharynx, and cricopharyngeus, as well as minimal UES pressure were measured using HRM.There was significantly positive correlation between the pressure of cricopharyngeus and forced expiratory volume in 1 second (FEV1). And there were significant correlations between results of VFSS and FEV1, FEV1%, forced vital capacity (FVC), and FVC%. There was a significant difference in the pressure of TB and cricopharyngeus between the control group and the ALS patient group. The pressures of VP, TB, lower pharynx, and cricopharyngeus have a significant correlation with the recommended feeding type by VFSS.Because it is possible to use HRM to quantitatively assess pharyngeal and respiratory weaknesses and it is more sensitive than other evaluation tools, the cutoff value of HRM parameters may be used to decide the feeding type in patients with ALS.

Differential kinematic features of the hyoid bone during swallowing in patients with Parkinson's disease

This study aimed to investigate spatiotemporal characteristics of the hyoid bone during swallowing in patients with Parkinson's disease (PD) and dysphagia. Spatiotemporal data of the hyoid bone was obtained from videofluoroscopic images of 69 subjects (23 patients with PD, 23 age- and sex-matched healthy elderly controls, and 23 healthy young controls). Normalized profiles of displacement/velocity were analyzed during different periods (percentile) of swallowing using functional regression analysis, and the maximal values were compared between the groups. Maximal horizontal displacement and velocity were significantly decreased during the initial backward (P = 0.006 and P < 0.001, respectively) and forward (P = 0.008 and P < 0.001, respectively) motions in PD patients compared to elderly controls. Maximal vertical velocity was significantly lower in PD patients than in elderly controls (P = 0.001). No significant difference was observed in maximal displacement and velocity in both horizontal and vertical planes between the healthy elderly and young controls, although horizontal displacement was significantly decreased during the forward motion (51st-57th percentiles) in the elderly controls. In conclusion, reduced horizontal displacement and velocity of the hyoid bone during the forward motion would be due to combined effects of disease and aging, whereas those over the initial backward motion may be considered specific to patients with PD.

High-resolution manometry: what about the pharynx?

PURPOSE OF REVIEW

High-resolution pharyngeal manometry (HRPM) is a well tolerated, catheter-based, method for recording the pressures and bolus flow generated by the pharyngeal muscles during swallowing. Despite a body of published evidence and a critical mass of investigators in the field, there is a lack of consensus surrounding what biomechanical phenomena to measure. The purpose of this review is to provide some insights into the information on swallowing physiology that can be gathered using HRPM.

RECENT FINDINGS

HRPM literature has focused on measuring biomechanical phenomena that may be relevant to measure in relation to dysphagia research. This review focuses on the measurement of pharyngeal luminal occlusive forces, intrabolus distension pressure, bolus presence and bolus flow timing as key features of pharyngeal swallowing that require measurement and allow for derivation of the Swallow Risk Index, a global measure of swallow function indicative of swallowing functional reserve.

SUMMARY

HRPM allows objective derivation of measures of swallow function that may have value for diagnosis and research in relation to swallowing disorders. HRPM has demonstrated clinical applicability in specific patient populations and offers unique advantages that compliment current assessment methods.

Open Mouth-Maximal Isometric Press: Development and Norms for Clinical Swallowing Evaluations and Treatment

Purpose The aims of this study were to (a) describe the development and utility of the Open Mouth-Maximal Isometric Press (OM-MIP), a tool designed for the quantitative assessment of suprahyoid-infrahyoid muscle strength; (b) examine the effects of age and sex on the OM-MIP; and (c) establish age- and sex-based OM-MIP norms. Method Two hundred sixteen healthy male and female volunteers were recruited. Participants performed the OM-MIP, and the maximum of 3 trials that were within 10% of each other was recorded. Rest between each trial was allowed to avoid fatigue. Multiple regression examined the influence of age and sex on the OM-MIP. Descriptive statistics outlined normative OM-MIP values for young adult (aged 18-39 years), middle-aged adult (aged 40-59 years), old adult (aged 60-79 years), and very old adult (aged ≥ 80 years) men and women. Two-way analysis of variance determined if normative data differed significantly between the age and sex groups. Results Age and sex significantly influenced the OM-MIP, although no significant interaction effect was identified. Women had lower mean OM-MIPs when compared with men ( p < .0005), and very old adults had lower mean OM-MIPs when compared with young ( p = .001), middle-aged ( p < .0005), and old ( p = .013) adults. Conclusions This study establishes age- and sex-based OM-MIP norms and outlines its potential utility during clinical swallowing evaluations and treatment. By providing these norms, clinicians can begin to quantitatively measure suprahyoid and infrahyoid strength, individualize resistance training programs to patients' OM-MIP 1 repetition maximum, and track strength changes over time in response to therapeutic interventions.

Different clinical predictors of aspiration pneumonia in dysphagic stroke patients related to stroke lesion: A STROBE-complaint retrospective study

Although stroke is one of the most common causes of dysphagia, no studies have investigated the radionuclide salivagram as a predictor of aspiration pneumonia in patients with stroke. In addition, few researches on the risk factors of aspiration pneumonia in patients with subacute and chronic stroke undergoing rehabilitation in the rehabilitation unit have been rarely conducted. In this study, therefore, we investigated whether a radionuclide salivagram could predict aspiration pneumonia, and tried to find other clinical factors that may be helpful in predicting aspiration pneumonia in stroke patients undergoing rehabilitation in the rehabilitation department.From March 2013 and January 2018, a retrospective review of the medical records of 1182 subacute and chronic stroke patients who were admitted to rehabilitation department (South Korea) was carried out. We included 117 stroke patients with swallowing difficulties who were admitted to our rehabilitation department and satisfied our criteria retrospectively. Stroke lesion, the degree of paralysis, sex, age, onset duration, feeding methods, the Mini-Mental State Examination (MMSE), the Global Deterioration Scale (GDS), the presence of aspiration in VFSS or salivagram, the penetration-aspiration scale (PAS), and the total score of the Modified Barthel Index (MBI) were investigated by reviewing medical records.To evaluate the predictor of aspiration pneumonia for patients with stroke, multivariate logistic regression analysis with forward stepwise was performed. In the results of this study, only MMSE was significant as a clinical predictor, but not aspiration in VFSS or salivagram in multivariate analysis of supratentorial stroke patients (OR, 0.895) (95% CI, 0.830-964). In multivariate analysis of infratentorial stroke patients, combined results of salivagram and VFSS (aspiration in a salivagram or VFSS) (OR, 0.956) (95% CI, 0.919-995), and total MBI scores were significant as clinical predictors (OR, 24.882) (95% CI, 1.298-477.143).In conclusion, MMSE can be a clinical predictor of the occurrence of aspiration pneumonia in patients with supratentorial stroke. In contrast, total MBI score and combined results of a salivagram and VFSS can be clinical predictors of the occurrence of aspiration pneumonia in patients with infratentorial stroke.

Dysphagia in the Older Patient

Dysphagia in older adults is a challenging problem and necessitates a team approach. The key to effective management is recognition. Patients tend to dismiss their symptoms as normal aging; therefore, early diagnosis depends on the diligence of the primary care doctors. No diagnostic technique can replace the benefits of a thorough history, with a detailed understanding of nutritional status and aspiration risk. Although one of the main goals in management is to ensure safe swallowing, the impact of a nonoral diet on the quality of life of patients should not be underestimated.

A novel fluoroscopic method for multidimensional evaluation of swallowing function

OBJECTIVE

Dynamic videofluoroscopic swallow study (VFSS) is used to investigate swallowing movements. However, it requires prolonged radiation exposure and mainly provides qualitative information. Herein, we present a multi-dimensional method for analyzing swallowing based on a pulsed, low-dose fluoroscopy technique that uses serial-shot images and evaluates the size, position, and temporal profile of the bolus to obtain a more comprehensive and realistic analysis of swallowing movements.

METHODS

Fifteen healthy adults drank two liquids: 20mL of pure water followed by 20mL of contrast medium mixture in a fluoroscopic study. Data were recorded in serial-shot images (7.5 frames/second, 1024×1024-pixel resolution, DICOM format). The images from the water and contrast swallows were inverted, synchronized, and subtracted to visualize the bolus in each frame. The pathway of the bolus was divided into 15 parts traversing the oropharynx, hypopharynx, and upper esophagus, and the total gray value was measured in each section. The results were presented as contour graphs.

RESULTS

The contour graphs allowed for information on the size, anatomical location, and temporal location of the bolus during swallowing to be displayed simultaneously. Two distinct swallowing patterns were observed in the subjects. The bolus showed two peaks-one in the hypopharynx and one in the upper esophagus-in all subjects. However, in nine of the 15 subjects, the two peaks were in different frames, whereas in six of the subjects, the two peaks were in the same frame.

CONCLUSION

We developed a new method for quantitatively evaluating swallowing. The technique allows for multidimensional assessment of the size, position, and temporal profile of the movement of the bolus across the pharynx. This method evaluates the swallowing movements using sharp, high-resolution images obtained by serial-shot, pulsed fluoroscopy with low radiation exposure. Additional studies are required to further clarify the variability of swallowing patterns and their clinical relevance in the evaluation of swallowing movements in healthy subjects and in patients with swallowing disorders.

Dynamic Musculoskeletal Functional Morphology: Integrating diceCT and XROMM

The tradeoff between force and velocity in skeletal muscle is a fundamental constraint on vertebrate musculoskeletal design (form:function relationships). Understanding how and why different lineages address this biomechanical problem is an important goal of vertebrate musculoskeletal functional morphology. Our ability to answer questions about the different solutions to this tradeoff has been significantly improved by recent advances in techniques for quantifying musculoskeletal morphology and movement. Herein, we have three objectives: (1) review the morphological and physiological parameters that affect muscle function and how these parameters interact; (2) discuss the necessity of integrating morphological and physiological lines of evidence to understand muscle function and the new, high resolution imaging technologies that do so; and (3) present a method that integrates high spatiotemporal resolution motion capture (XROMM, including its corollary fluoromicrometry), high resolution soft tissue imaging (diceCT), and electromyography to study musculoskeletal dynamics in vivo. The method is demonstrated using a case study of in vivo primate hyolingual biomechanics during chewing and swallowing. A sensitivity analysis demonstrates that small deviations in reconstructed hyoid muscle attachment site location introduce an average error of 13.2% to in vivo muscle kinematics. The observed hyoid and muscle kinematics suggest that hyoid elevation is produced by multiple muscles and that fascicle rotation and tendon strain decouple fascicle strain from hyoid movement and whole muscle length. Lastly, we highlight current limitations of these techniques, some of which will likely soon be overcome through methodological improvements, and some of which are inherent. Anat Rec, 301:378-406, 2018. © 2018 Wiley Periodicals, Inc.