Computational Analysis of Pharyngeal Swallowing Mechanics in Patients with Motor Neuron Disease: A Pilot Investigation

Dynamic suprahyoid muscle ultrasound in assessing oropharyngeal dysphagia in neurological disorders

BACKGROUND

Appropriate evaluation and management of dysphagia are essential in neurological disorders. However, there is currently a lack of a simple yet reliable method for dysphagia evaluation.

AIM

This study aimed to investigate the usefulness of new dynamic M-mode ultrasonography (US) parameters of suprahyoid muscle (SHM) to evaluate dysphagia.

DESIGN

Prospective observational, cross-sectional study.

SETTING

Inpatient setting at neurology department of tertiary medical center.

POPULATION

A total of 89 patients with dysphagia and 175 healthy volunteers were enrolled in the study. Patients were subdivided into mild and severe dysphagia groups depending on the need for dietary changes and disease classification, which included amyotrophic lateral sclerosis, peripheral neuromuscular diseases, and stroke.

METHODS

Dynamic M-mode US was performed during swallowing to obtain the SHM thickness (the baseline thickness of the SHM), SHM displacement (peak-to-peak amplitude of SHM movement), SHM difference (SHM displacement - SHM thickness), SHM ratio (SHM displacement/SHM thickness), peak-to-peak time, and total duration. A videofluoroscopic swallowing study (VFSS) was performed.

RESULTS

Significant differences were found in SHM displacement and SHM difference according to dysphagia severity (P<0.001). The SHM ratio, total duration (P<0.001), and peak-to-peak time (P=0.001) differed significantly according to the patients' underlying diseases. The pharyngeal delay time and penetration-aspiration scale from the VFSS demonstrated significant negative correlations with SHM displacement and difference (P<0.001). By combining SHM difference and total duration, patients with dysphagia could be distinguished from healthy controls, with the highest negative predictive value of 95.6%.

CONCLUSIONS

Dynamic M-mode US of the SHM provided added value in evaluating the severity of dysphagia and differentiating swallowing mechanics of dysphagia related to underlying neurological disorders.

CLINICAL REHABILITATION IMPACT

Dynamic M-mode US of the SHM can serve as a supportive tool for rapid screening and repetitive follow-up of patients with dysphagia, which would contribute to dysphagia rehabilitation in patients with various neurological disorders.

A Newly Discovered Tendon Between the Genioglossus Muscle and Epiglottic Cartilage Identified by Histological Observation of the Pre-Epiglottic Space

Epiglottic retroversion is difficult to explain anatomically. One reason is inadequate structural identification of the ligaments in the submucosal tissue anterior to the epiglottis (pre-epiglottic space, PES). Although studies have shown that tongue root movement plays a role in epiglottic retroversion, few morphological reports have investigated the attachment of the lingual muscles to the epiglottis. This study reconstructed the fiber structure of the PES by comprehensively analyzing fiber alignment in the PES focusing on the hyoepiglottic ligament, which runs between the lingual muscles and the epiglottis. Gross and microscopic observations of the submucosal structures from the tongue to the larynx of 20 cadavers (10 men, 10 women; mean age 79 years) were performed. A tendon continuing from the posterior part of the genioglossus muscle and attaching to the center of the epiglottic cartilage was identified in the midline area of the epiglottis. We named this tendon the glossoepiglottic tendon. In contrast, the hyoepiglottic ligament is found between the hyoid bone and the epiglottis and is attached from the lateral margin of the epiglottic cartilage to its base. Furthermore, the glossoepiglottic tendon consists of a high-density fiber bundle that is thicker than the hyoepiglottic ligament. These results show that the conventional hyoepiglottic ligament has a two-layer structure consisting of an upper fiber bundle connected to the genioglossus muscle and a lower fiber bundle connected to the hyoid bone. Sustained contraction of the posterior part of the genioglossus muscle therefore places the epiglottis under persistent traction, suggesting that its relaxation may cause epiglottic retroversion.

Screening for oropharyngeal dysphagia in adult patients with neuromuscular diseases using the Sydney Swallow Questionnaire

INTRODUCTION/AIMS

Oropharyngeal dysphagia is common in patients with neuromuscular diseases (NMDs). Its early recognition is vital for proper management. We tested a large cohort of adult NMD patients for oropharyngeal dysphagia using the Sydney Swallow Questionnaire (SSQ). We also looked for possible differences in characteristics of oropharyngeal dysphagia in various NMD groups and diseases. Finally, we compared results of this screening with those from their corresponding medical records for eventual "clinical history" of dysphagia.

METHODS

We asked patients to fill in the SSQ during follow-up outpatient visits at our neuromuscular reference center. A total score above the cutoff score of 118.5 out of 1700 was indicative of oropharyngeal dysphagia.

RESULTS

Of the 304 adult patients assessed for eligibility, 201 NMD patients (96 women and 105 men, aged 49.0 ± 16.2 years) were included and tested in this study. Oropharyngeal dysphagia was detected in 45% of all the NMD patients when using the SSQ, whereas only 12% had a positive medical record for dysphagia. The median SSQ scores for patients with myotonic syndromes (including myotonic dystrophy type 1), with amyotrophic lateral sclerosis, and with facioscapulohumeral dystrophy were above the cutoff score. The SSQ scores obtained revealed distinct oropharyngeal dysphagia characteristics in the different NMD groups and diseases.

DISCUSSION

The SSQ tests positively for oropharyngeal dysphagia in a higher proportion of NMD patients compared with their medical records. The distinct oropharyngeal dysphagia characteristics we revealed in different NMD groups and diseases may help to elaborate adapted clinical approaches in the management of oropharyngeal dysphagia.

Pilot Study of Quantitative Methods for Differentiating Pharyngeal Swallowing Mechanics by Dysphagia Etiology

Quantitative analysis of modified barium swallow (MBS) imaging is useful to determine the impact of various disease states on pharyngeal swallowing mechanics. In this retrospective proof of concept study, kinematic analysis and computational analysis of swallowing mechanics (CASM) were used to demonstrate how these methods differentiate swallowing dysfunction by dysphagia etiology. Ten subjects were randomly selected from four cohorts of dysphagic patients including COPD, head and neck cancer (HNC), motor neuron disease, and stroke. Each subject was age- and gender-matched with healthy, non-dysphagic controls. MBS videos of 5 ml thin and 5 ml thick bolus trials from each subject were used. A MATLAB tracker tool was adapted and updated to collect and compile data for each video (n = 160). For kinematic measurements, a MANOVA was performed with post-hoc analyses to determine group differences. For CASM measurements, a morphometric canonical variate analysis with post hoc analysis was performed to determine group differences. Kinematic analyses indicated statistically significant differences between HNC cohort and controls in distance measurements for hyolaryngeal approximation (p = .001), laryngeal elevation (p = 0.0001), pharyngeal shortening (p = 0.0002), and stage transition duration timing (p = 0.002). Timing differences were noted between the stroke cohort and controls for pharyngeal transit time (p = 0.007). Multivariate morphometric canonical variate analysis showed significant differences between etiology groups (p < 0.0001) with eigenvectors indicating differing patterns of swallowing mechanics. This study demonstrated that swallowing mechanics among cohorts of dysphagic patients can be differentiated using kinematics and CASM, providing different but complementary quantitative methods for investigating the impact of various disease states on swallowing function.

Best Practices in Modified Barium Swallow Studies

Purpose The modified barium swallow study (MBSS) is a widely used videofluoroscopic evaluation of the functional anatomy and physiology of swallowing that permits visualization of bolus flow throughout the upper aerodigestive tract in real time. The information gained from the examination is critical for identifying and distinguishing the type and severity of swallowing impairment, determining the safety of oral intake, testing the effect of evidence-based frontline interventions, and formulating oral intake recommendations and treatment planning. The goal of this review article is to provide the state of the science and best practices related to MBSS. Method State of the science and best practices for MBSS are reviewed from the perspectives of speech-language pathologists (SLPs) and radiologists who clinically practice and conduct research in this area. Current quandaries and emerging clinical and research trends are also considered. Results This document provides an overview of the MBSS and standards for conducting, interpreting, and reporting the exam; the SLPs' and radiologist's perspectives on standardization of the exam; radiation exposure; technical parameters for recording and reviewing the exam; the importance of an interdisciplinary approach with engaged radiologists and SLPs; and special considerations for examinations in children. Conclusions The MBSS is the primary swallowing examination that permits visualization of bolus flow and swallowing movement throughout the upper aerodigestive tract in real time. The clinical validity of the study has been established when conducted using reproducible and validated protocols and metrics applied according to best practices to provide accurate and reliable information necessary to direct treatment planning and limit radiation exposure. Standards and quandaries discussed in this review article, as well as references, provide a basis for understanding the current best practices for MBSS.

A Cross-Sectional, Quantitative Videofluoroscopic Analysis of Swallowing Physiology and Function in Individuals With Amyotrophic Lateral Sclerosis

Purpose To date, research characterizing swallowing changes in individuals with amyotrophic lateral sclerosis (ALS) has primarily relied on subjective descriptions. Thus, the degree to which swallowing physiology is altered in ALS, and relationships between such alterations and swallow safety and/or efficiency are not well characterized. This study provides a quantitative representation of swallow physiology, safety, and efficiency in a sample of individuals with ALS, to estimate the degree of difference in comparison to published healthy reference data and identify parameters that pose risk to swallow safety and efficiency. Secondary analyses explored the therapeutic effect of thickened liquids on swallowing safety and efficiency. Method Nineteen adults with a diagnosis of probable-definite ALS (El-Escorial Criteria-Revised) underwent a videofluoroscopic swallowing study, involving up to 15 sips of barium liquid (20% w/v), ranging in thickness from thin to extremely thick. Blinded frame-by-frame videofluoroscopy analysis yielded the following measures: Penetration-Aspiration Scale, number of swallows per bolus, amount of pharyngeal residue, degree of laryngeal vestibule closure (LVC), time-to-LVC, duration of LVC (LVCdur), pharyngeal area at maximum constriction, diameter of upper esophageal sphincter opening, and duration of UES opening (UESOdur). Measures of swallow physiology obtained from thin liquid trials were compared against published healthy reference data using unpaired t tests, chi-squared tests, and Cohen's d effect sizes (adjusted p < .008). Preliminary relationships between parameters of swallowing physiology, safety, and efficiency were explored using nonparametric Cochrane's Q, Friedman's test, and generalized estimating equations (p < .05). Results Compared to healthy reference data, this sample of individuals with ALS displayed a higher proportion of swallows with partial or incomplete LVC (24% vs. < 1%), increased time-to-LVC (d = 1.09), reduced UESwidth (d = 0.59), enlarged pharyngeal area at maximum constriction, prolonged LVCdur (d = 0.64), and prolonged UESOdur (d = 1.34). Unsafe swallowing (i.e., PAS ≥ 3) occurred more frequently when LVC was partial/incomplete or time-to-LVC was prolonged. Pharyngeal residue was associated with larger pharyngeal areas at maximum constriction. Unsafe swallowing occurred less frequently with extremely thick liquids, compared to thin liquids. No significant differences in pharyngeal residue were observed based on liquid thickness. Conclusions Quantitative videofluoroscopic measurements revealed moderate-to-large differences in swallow physiology between this sample of individuals with ALS and healthy reference data. Increased time-to-LVC, noncomplete LVC, and enlarged pharyngeal area at maximum constriction were associated with impaired swallow safety or efficiency. Thickened liquids may mitigate the risk of acute episodes of aspiration in individuals with ALS. Further work is needed to corroborate these preliminary findings and explore how swallowing profiles evolve throughout disease progression.

Measuring Vallecular Volume on Flexible Endoscopic Evaluation of Swallowing: A Proof of Concept Study

Currently, no method exists to measure the size of pharyngeal and laryngeal structures on endoscopy. Imaging for dysphagia diagnostic techniques, for the most part, still relies on qualitative assumptions and cursory visual examinations to induce patients' swallowing safety and function. In this proof of concept study, we measured vallecular cavity volume using simultaneous modified barium swallows (MBS) and flexible endoscopic evaluation of swallowing (FEES). Similar to the three-dimensional image compilation fields of facial reconstruction, medical imagery, and forensic science, this proposed methodology combines the two-dimensional images yielded in FEES and MBS videos to calculate estimates of the valleculae in a 3D perspective. A tracking tool was used to measure distances on MBS, while endoscopic specifications were used to find distances on FEES. This combination of ratio measurements allowed for measurement on both the MBS and FEES. In a sample of n = 37 dysphagia patients referred for MBS/FEES studies, the mean distance from the tip of endoscope to the closest point of epiglottis was 25.38 mm, the mean vallecular area outlined on MBS video was 84.72 mm², the mean epiglottal width was 18.16 mm, and the mean vallecular volume was 1.55 mL. Future application could include tracking growth of tumors, glottic opening, volume of residue and tracking of any other important outcome involving movement, size, and targets of interest with higher precision.

Functional Modules of Pharyngeal Swallowing Mechanics

OBJECTIVES

The present retrospective cohort study aims to test the hypothesis that elements of swallowing mechanics including hyoid movement, laryngeal elevation, tongue base retraction, pharyngeal shortening, pharyngeal constriction, and head and neck extension can be grouped into functional modules, and that these modules are predictably altered in disease states.

METHODS

Modified barium swallow video clips of a thick and a thin liquid swallow from 40 normal patients and 10 dysphagic post-treatment oropharyngeal head-and-neck cancer (HNC) patients were used in this study. Coordinate locations of 12 anatomical landmarks mapping pharyngeal swallowing mechanics were tracked on every frame during the pharyngeal phase of each swallow using a custom-made MATLAB tool. Morphometric modularity hypothesis testing was performed on these coordinate data to characterize the modular elements of swallowing function in each cohort using MorphoJ software.

RESULTS

The elements of normal swallowing can be grouped into four functional modules including bolus propulsion, pharyngeal shortening, airway protection, and head and neck posture. Modularity in HNC patient showed an intact airway protection module but altered bolus propulsion and pharyngeal shortening modules. To cross-validate the alteration in modules, a post hoc analysis was performed, which showed significantly increased vallecular (P < .04) and piriform (P < .05) residue but no significant change in aspiration status in the HNC cohort versus controls.

CONCLUSIONS

This study suggests that while pharyngeal swallowing mechanics is highly complex, the system is organized into functional modules, and that changes in modularity impacts swallowing performance. This approach to understanding swallowing function may help the patient care team better address swallowing difficulties.

LEVEL OF EVIDENCE

2b.

Age-related alterations in swallowing biomechanics

BACKGROUND

Aging rodent models allow for the discovery of underlying mechanisms of cranial muscle dysfunction. Methods are needed to allow quantification of complex, multivariate biomechanical movements during swallowing. Videofluoroscopic swallow studies (VSS) are the standard of care in assessment of swallowing disorders in patients and validated quantitative, kinematic, and morphometric analysis methods have been developed. Our purpose was to adapt validated morphometric techniques to the rodent to computationally analyze swallowing dysfunction in the aging rodent.

METHODS

VSS, quantitative analyses (bolus area, bolus velocity, mastication rate) and a rodent specific multivariate, morphometric computational analysis of swallowing biomechanics were performed on 20 swallows from 5 young adult and 5 old Fischer 344/Brown Norway rats. Eight anatomical landmarks were used to track the relative change in position of skeletal levers (cranial base, vertebral column, mandible) and soft tissue landmarks (upper esophageal sphincter, base of tongue).

RESULTS

Bolus area significantly increased and mastication rate significantly decreased with age. Aging accounted for 77.1% of the variance in swallow biomechanics, and 18.7% of the variance was associated with swallow phase (oral vs pharyngeal). Post hoc analyses identified age-related alterations in tongue base retraction, mastication, and head posture during the swallow.

CONCLUSION

Geometric morphometric analysis of rodent swallows suggests that swallow biomechanics are altered with age. When used in combination with biological assays of age-related adaptations in neuromuscular systems, this multivariate analysis may increase our understanding of underlying musculoskeletal dysfunction that contributes to swallowing disorders with aging.