Neurophysiology of swallowing: effects of age and bolus type

Cognitive decline limits compensatory resource allocation within the aged swallowing network

Cognitive decline has been postulated to predispose to presbyphagia but the neurophysiological basis of this interaction is unclear. To investigate the role of cognition for compensatory resource allocation within the swallowing network and behavioral swallowing performance in dual-task cognitive and motor interference in ageing, volunteers ≥ 70 years of age without preexisting diseases causing dysphagia were investigated using Flexible Endoscopic Evaluation of Swallowing (FEES) including a cognitive and motor dual-task paradigm and a Montreal Cognitive Assessment. The neural correlates of swallowing during dual-task were characterized using magnetoencephalography. Results were related to cognitive function. Sixty-three participants (77.7 ± 6.1 years) underwent FEES, of which 40 additionally underwent MEG. Both cognitive and motor dual-tasks interfered with swallowing function resulting in an increase in pharyngeal residue and premature bolus spillage. The extent of swallowing deterioration ("dual-task cost") was associated with cognitive decline (cognitive dual-task: Spearman's rho =  - 0.39, p = 0.002; motor dual-task: Spearman's rho =  - 0.25, p = 0.046). When challenged with dual-tasking participants with regular cognition showed compensatory stronger and broader brain activation in cortical pre- and supplementary motor planning areas as well as in frontal executive regions within the cortical swallowing network (p = 0.004) compared to participants with cognitive deficits. They also performed better in the competing cognitive and motor dual-task and showed fewer incorrect responses (p = 0.028). Oropharyngeal swallowing involves cognitive cortical processing. Cognitive decline seems to limit the capacity for compensatory resource allocation within the swallowing network. This may lead to deterioration in both swallowing function and concurrent cognitive-motor performance in challenging dual-task situations.

Cortical Activation during Swallowing Exercise Tasks: an fNIRS Pilot Study

This pilot study used functional near-infrared spectroscopy (fNIRS) to examine brain activity in selected regions of the left motor and sensory cortex while doing swallowing-related tasks. Specifically, differences in cortical activation during normal saliva swallows, effortful swallows, and tongue pressing were investigated. Nine healthy, right-handed adults (5 female, 4 male; Age: 22-30 years) were recruited. The tasks included were (1) normal saliva swallowing, (2) effortful saliva swallowing, and (3) lingual pressing against the palate. Each task was completed three times in a block, for a total of five blocks. Blocks were randomized and presented with set time intervals using PsychoPy. Motor activity was highest during effortful swallows, followed by normal swallows, and lingual presses. Activation in the sensory region was not significantly different across tasks; however, effortful swallows elicited the highest mean peak activation. Our findings suggest that fNIRS can be a viable imaging method used to examine differences in cortical activity in the context of swallowing. Its applicability in future dysphagia research should be explored.

Normative Values of the Repetitive Saliva Swallow Test and Clinical Factors Affecting the Test Scores in Healthy Adults

The Repetitive Saliva Swallow Test (RSST) is a screening test for oropharyngeal dysphagia during which the subject is asked to perform as many empty swallows as possible in 30 s. Previous validation studies found a cutoff value of 3 > swallows as pathological. The aims of this study were to establish the normative values of the RSST and to examine the effect of clinical factors on RSST scores in healthy adults. A cross-sectional study of 280 adults. An equal number of females and males were recruited for each decade of life, ages 20 to 90 years. Patients reporting swallowing difficulties, history of neurologic disorders, or head and neck surgery or radiation were excluded. Data collected included RSST scores, number and type of comorbidities, number of prescribed medications, body mass index, smoking habits, and self-assessment xerostomia questionnaire. The mean RSST score for the entire cohort was 7.01 ± 2.86. Males had a higher RSST score (7.6 ± 3.04 compared to 6.47 ± 2.56, p = 0.001). Age showed an inverse correlation with RSST scores (Pearson's Correlation Coefficient (PCC) = -0.463, p < 0.0001), as well as body mass index, BMI (PCC = -0.2, p < 0.0001), number of co-morbidities (PCC=-0.344, p < 0.0001) and number of prescribed medications (PCC= -0.425, p < 0.0001). Self-reported amount of saliva positively correlated (PCC = 1.05, p = 0.04) with RSST scores. A multivariate logistic regression analysis was performed. Age, sex, BMI, and number of prescribed medications were found as significant independent factors on RSST scores. RSST scores in healthy adults decline with age and are lower in females, individuals taking multiple medications and with higher BMI. Mean RSST for all age groups did not fall beneath the previously established pathological cut-off.

Correlation Between Swallowing and Cognitive Brain Networks in Older Adults via Functional MRI

BACKGROUND

Clinical evidence supports that swallowing function is correlated with cognition, but the neurobiological mechanism associated with cognitive impairment and dysphagia remains unclear.

OBJECTIVES

To compare the brain activation patterns of the swallowing and the cognitive tasks and explore neural associations between swallowing and cognitive function via task-related functional magnetic resonance imaging (fMRI).

METHODS

A total of 13 healthy older adults (aged > 60 years) were recruited. Participants underwent the clinical dementia rating (CDR) test and the Montreal Cognitive Assessment (MoCA). A block-designed task-related fMRI study was conducted where each participant completed both swallowing and cognitive tasks within a single session. During the swallowing task, participants swallowed 2 mL of thickened water, while the Stroop Colour Word Test (SCWT) served as the cognitive task. First-level analysis of swallowing time-series images utilised the general linear model (GLM) with Statistical Parametric Mapping (SPM), applying a voxel threshold of p < 0.001 for significance. Common activations in brain regions during swallowing and cognitive tasks were extracted at the group level, with significance set at p < 0.05, corrected for multiple comparisons using the false discovery rate (FDR), with a minimum cluster size of 20 voxels. Correlation analysis between behavioural measurements and imaging signals was also conducted.

RESULTS

Some regions were commonly activated in both task networks; these regions were the bilateral occipital lobe, cerebellum, lingual gyrus, fusiform, middle frontal gyrus, precentral and postcentral gyrus, right supramarginal and inferior parietal lobe. Most importantly, the average beta value of cognitive and swallowing tasks in these areas are both significantly negative related to the MoCA score. Furthermore, opposite signal changes were seen in the bilateral prefrontal lobes during the swallowing task, while positive activation in the bilateral prefrontal lobes was observed during the SCWT. Postcentral gyrus activation was more extensive than precentral gyrus activation in the swallowing task.

CONCLUSION

The common activation of swallowing and cognitive tasks had multiple foci. The activity of cognitive and swallowing task in these areas is significantly negative correlated with the MoCA score. These findings may help to illustrate the association between dysphagia and cognitive impairment due to the common brain regions involved in cognition and swallowing and may provide a reference for further rehabilitation of dysphagia.

TRIAL REGISTRATION

Clinical Trial: (Chinese Clinical Trial Registry): ChiCTR1900021795.

Short-term cortical activation changes associated with postural compensation in swallowing

Compensatory strategies used to treat dysphagia, like the chin-down and chin-up positions, are often employed by speech-language pathologists to enhance swallowing safety. However, their effects on cortical neural responses remain unclear. This study aimed to investigate the cortical hemodynamic responses to swallowing across three head positions -chin-down, chin-neutral, and chin-up - using functional near-infrared spectroscopy (fNIRS) in the bilateral precentral and postcentral gyrus regions of interest. Twenty-six healthy adults completed 32 swallows of 5 ml water in each head position. Results revealed short-term cortical activation increases for chin-up swallows compared to both chin-neutral (mean difference = 1.2, SE = 0.18, p = .048) and chin-down swallows (mean difference = 0.76, SE = 0.18, p = .009). These findings suggest that postural changes during swallowing induce immediate neural adaptations in people without swallowing difficulty. These modifications likely reflect the necessary sensory and neuromuscular adaptations required for safe swallowing in different head positions, with less hyolaryngeal movement needed for a chin-down swallow and more movement needed for a chin-up swallow. While challenging swallow conditions, like the chin-up, may offer promising therapeutic potential, caution is warranted considering the associated safety risk, and further investigation is needed. This study provides insights into the immediate effects of head positions on cortical activity during swallowing and highlights avenues for future research in dysphagia rehabilitation.

Stochastic electrical stimulation of the thoracic or cervical regions with surface electrodes facilitates swallow in rats

Introduction

Aspiration pneumonia, a leading cause of mortality, poses an urgent challenge in contemporary society. Neuromuscular electrical stimulation (NMES) has been commonly used in dysphagia rehabilitation. However, given that NMES at motor threshold targets only specific muscles, it carries a potential risk of further compromising functions related to swallowing, respiration, and airway protection. Considering that the swallow motor pattern is orchestrated by the entire swallow pattern generator (the neural mechanism governing a sequence of swallow actions), a rehabilitation approach that centrally facilitates the entire circuit through sensory nerve stimulation is desirable. In this context, we propose a novel stimulation method using surface electrodes placed on the back to promote swallowing.

Methods

The efficacy of the proposed method in promoting swallowing was evaluated by electrically stimulating sensory nerves in the back or neck. Probabilistic stimulus was applied to either the back or neck of male and female rats. Swallows were evoked by an oral water stimulus, and electromyographic (EMG) activity of the mylohyoid, thyroarytenoid, and thyropharyngeus muscles served as the primary outcome measure.

Results

Gaussian frequency stimulation applied to the skin surface of the thoracic back elicited significant increases in EMG amplitude of all three swallow-related muscles. Neck stimulation elicited a significant increase in EMG amplitude of the thyroarytenoid during swallow, but not the mylohyoid or thyropharyngeus muscles.

Discussion

While the targeted thoracic spinal segments T9-T10 have been investigated for enhancing respiration, the promotion of swallowing through back stimulation has not been previously studied. Furthermore, this study introduces a new probabilistic stimulus based on Gaussian distribution. Probabilistic stimuli have been reported to excel in nerve stimulation in previous research. The results demonstrate that back stimulation effectively facilitated swallow more than neck stimulation and suggest potential applications for swallowing rehabilitation.

Swallowing performance in older adults: Associated cognitive, neuroanatomical and demographic factors

BACKGROUND

Swallowing problems are frequently seen in older adults, especially in individuals with cognitive impairment (CI). The brain plays a crucial role in both cognition and swallowing. Using magnetic resonance imaging (MRI) data, researchers identified regions associated with swallowing. However, it is not yet fully elucidated which factors influence the swallowing performance in older adults.

OBJECTIVES

The current study investigated which factors, such as cognitive function, neuroanatomical factors (e.g., the cortical thickness and volume of specific brain regions) and demographical factors are associated with swallowing performance in older adults. Secondly, it was investigated whether there is a difference in neuroanatomical factors between individuals with and without CI.

RESEARCH DESIGN AND METHODS

In total, 15 CI individuals (73.1 ± 9.1 years; 46.7% male) and 48 non-CI controls (69.0 ± 5.1 years; 29.2% male) were included. The repetitive saliva swallowing test (RSST) was performed, and an MRI scan was acquired from the participants.

RESULTS

Multivariate linear regression analysis showed that the cortical thickness of the right supramarginal gyrus and female gender were positively associated, and a higher age was negatively associated with the RSST in older adults (p < .05). CI was not significantly associated with swallowing performance. Furthermore, it was found that the cortical volume differs more frequently between CI and non-CI than the cortical thickness.

CONCLUSION

A thinner cortex of the right supramarginal gyrus and being an older female are associated with poorer swallowing performance. Secondly, cortical volume was more often found to differ between CI and non-CI individuals than cortical thickness.

Swallowing dysfunctions in patients with disorders of consciousness: Evidence from neuroimaging data, assessment, and management

Following severe brain injuries, a subset of patients may remain in an altered state of consciousness; most of these patients require artificial feeding. Currently, a functional oral phase and the presence of exclusive oral feeding may constitute signs of consciousness. Additionally, the presence of pharyngo-laryngeal secretions, saliva aspiration, cough reflex and tracheostomy are related to the level of consciousness. However, the link between swallowing and consciousness is yet to be fully understood. The primary aim of this review is to establish a comprehensive overview of the relationship between an individual's conscious behaviour and swallowing (reflexive and voluntary). Previous studies of brain activation during volitional and non-volitional swallowing tasks in healthy subjects are also reviewed. We demonstrate that the areas activated by voluntary swallowing tasks (primary sensorimotor, cingulate, insula, premotor, supplementary motor, cerebellum, and operculum) are not specific to deglutitive function but are shared with other motor tasks and brain networks involved in consciousness. This review also outlines suitable assessment and treatment methods for dysphagic patients with disorders of consciousness. Finally, we propose that markers of swallowing could contribute to the development of novel diagnostic guidelines for patients with disorders of consciousness.

Electroacupuncture at HT5 + GB20 promotes brain remodeling and significantly improves swallowing function in patients with stroke

Background

This study compared the differences in the degree of brain activation, and swallowing function scales in patients with post-stroke dysphagia after treatment. We explored the mechanism of cortical remodeling and the improvement effect of electroacupuncture on swallowing function in patients and provided a theoretical basis for the clinical application of electroacupuncture.

Methods

Fifty patients with post-stroke dysphagia were randomized to the control or electroacupuncture group. The control group underwent conventional swallowing rehabilitation for 30 min each time for 12 sessions. In the electroacupuncture group, electroacupuncture was performed based on conventional swallowing rehabilitation for 30 min each time for 12 sessions. Cortical activation tests and swallowing function assessments were performed before and after treatment. Statistical analyses were used to investigate the differences within and between the two groups to explore the treatment effects.

Results

There were no statistical differences in clinical characteristics and baseline data between the two groups before treatment. Cortical activation and swallowing function were improved to different degrees in both groups after treatment compared with before treatment. After treatment, the electroacupuncture group showed higher LPM (t = 4.0780, p < 0.001) and RPM (t = 4.4026, p < 0.0001) cortical activation and tighter functional connectivity between RS1 and LM1 (t = 2.5336, p < 0.05), RM1 and LPM (t = 3.5339, p < 0.001), RPM and LM1 (t = 2.5302, p < 0.05), and LM1 and LPM (t = 2.9254, p < 0.01) compared with the control group. Correspondingly, the improvement in swallowing function was stronger in the electroacupuncture group than in the control group (p < 0.05).

Conclusion

This study demonstrated that electroacupuncture based on conventional treatment activated more of the cerebral cortex associated with swallowing and promoted functional connectivity and remodeling of the brain. Accompanying the brain remodeling, patients in the electroacupuncture group also showed greater improvement in swallowing function.

Clinical trial registration

ClinicalTrials.gov, ChiCTR2300067457.

Surface Electromyography for Evaluating the Effect of Aging on the Coordination of Swallowing Muscles

Swallowing function can deteriorate with age, leading to a risk of dysphagia. Swallowing evaluation by surface electromyography (sEMG) can be easily and extensively applied for an elderly population. This study evaluated the temporal events observed by sEMG to clarify how aging affects the coordination among the masticatory and suprahyoid muscles. We recruited elderly individuals (over 65 years old) who denied dysphagia. The sEMG activities of anterior temporalis, masseter, and suprahyoid muscles were recorded during 3, 15, and 30 ml water swallowing tests (WST). We calculated the time interval between anterior temporalis and suprahyoid peak activity (T-SH interval) and masseter and suprahyoid peak activity (M-SH interval) and analyzed their correlation with age. The subjects who could and could not swallow 30 ml of water in one gulp were further assigned into the one-gulp and piecemeal groups, respectively, for subgroup analysis. We recruited 101 subjects, among whom 75 (26 males and 49 females) were analyzed after excluding those with suspected dysphagia or low-quality sEMG recordings. Age was significantly correlated with the bilateral T-SH (left: r = 0.249, p = 0.031; right: r = 0.412, p < 0.01) and right M-SH (r = 0.242, p = 0.037) intervals in the 30 ml WST. The correlation between intervals and age were observed in both subgroups. sEMG can be used to investigate the effect of aging on the temporal coordination between masticatory and suprahyoid contraction. Further studies are needed to verify the validity of screening subclinical dysphagia in the elderly.

Post-stroke dysphagia: Clinical characteristics and evolution in a single-primary stroke center

BACKGROUND

Dysphagia is a common manifestation after stroke and seems to play a major role in clinical and functional outcomes.

OBJECTIVES

To identify clinical predictors of higher degrees of dysphagia, as well as assess its burden in our hospital, in order to understand how to improve the approach to this symptom.

METHODS

We included 311 patients admitted in an acute stroke unit in a year-long period. The relationship of dysphagia with different outcomes, both in acute phase and within the first year after stroke, were investigated.

RESULTS

Using the Pearson Correlation Coefficient, NIHSS score at admission was positively correlated with the degree of dysphagia (r = 0,783; p <  0,001) and total anterior circulation infarcts and age (>  70 years) were also associated with higher risk of dysphagia (p <  0.001). During hospitalization both respiratory infections and mortality occurred at significantly higher rates for dysphagic patients (p <  0.001) and we observed an increasing trend towards a higher mortality rate, the higher the degree of dysphagia. These patients stayed longer in the stroke unit, with less chance to be discharged home and more frequently transferred to inpatient rehabilitation care. One year after admission, dysphagic patients were more frequently readmitted due to pneumonia and we observed a higher mortality rate compared to patients without dysphagia (p <  0.001).

CONCLUSION

The presence of the above-mentioned dysphagia predictive factors should alert us to the need for an early approach, starting in the stroke unit, but also after discharge, taking into account its impact on clinical outcomes, mortality and healthcare costs.

Brain functional activity of swallowing: A meta-analysis of functional magnetic resonance imaging

BACKGROUND

Swallowing is one of the most important activities in our life and serves the dual roles of nutritional intake and eating enjoyment.

OBJECTIVE

The study aimed to conduct a meta-analysis to investigate the brain activity of swallowing.

METHODS

Studies of swallowing using functional magnetic resonance imaging were reviewed in PubMed, Web of Science, China National Knowledge Infrastructure (CNKI), Chinese Science and Technology Periodical Database (VIP) and Wan Fang before 30 November 2021. Two authors analysed the studies for eligibility criteria. The final inclusion of studies was decided by consensus. An activation likelihood estimation (ALE) meta-analysis of these studies was performed with GingerALE, including 16 studies.

RESULTS

For swallowing, clusters with high activation likelihood were found in the bilateral insula, bilateral pre-central gyrus, bilateral post-central gyrus, left transverse temporal gyrus, right medial front gyrus, bilateral inferior frontal gyrus and bilateral cingulate gyrus. For water swallowing, clusters with high activation likelihood were found in the bilateral inferior frontal gyrus and the left pre-central gyrus. For saliva swallowing, clusters with high activation likelihood were found in the bilateral cingulate gyrus, bilateral pre-central gyrus, left post-central gyrus and left transverse gyrus.

CONCLUSION

This meta-analysis reflects that swallowing is regulated by both sensory and motor cortex, and saliva swallowing activates more brain areas than water swallowing, which would promote our knowledge of swallowing and provide some direction for clinical and other research.

Screening of dysphagia in geriatrics

BACKGROUND

The oropharyngeal dysphagia is an underestimated symptom with various causes in the geriatric population. Clinical presentation is often insidious and dysphagia symptoms are seldomly mentioned by elderly patients although causing many life-threatening complications. The aim of this work was to introduce an easy applicable tool to be used by the caregivers and general practitioners for screening of dysphagia in geriatrics for early detection of at risk individuals.

METHODS

A sample of 200 Egyptian Arabic-speaking elderly patients (65 years or older) not complaining of dysphagia was recruited from nursing homes in Greater Cairo Area. They or their caregivers completed the designed screening tool, including; the designed questionnaires of dysphagia manifestations and eating habits. General, oral motor and bedside evaluation were also performed. In addition to filling in the EAT10 questionnaire and FEES that was performed for only suspected cases for the purpose of validation of the screening tool.

RESULTS

The dysphagia manifestations questionnaire was significantly correlated with EAT 10 with p value of 0.001. It was correlated in some of its aspects with FEES showing quite reliability with p values' range between 0.012 and 0.044. The Questionnaire of eating habits reliability of r- value of 0.568 slightly exceeding EAT10 reliability of r -value of 0.721 in the subjects under study. The cutoff point of total score of the dysphagia manifestations was > 5, with a sensitivity of 17.65% & a specificity of 94.20%. The cutoff point of total score of the bedside evaluation was ≤ 1 with a sensitivity of 66.9% & a specificity of 56.9%.

CONCLUSION

the use of this easy applicable screening tool managed to suspect and later on diagnose cases with oropharyngeal dysphagia in non-complaining aging subjects.

Bioenergetic Evaluation of Muscle Fatigue in Murine Tongue

Muscle fatigue is the diminution of force required for a particular action over time. Fatigue may be particularly pronounced in aging muscles, including those used for swallowing actions. Because risk for swallowing impairment (dysphagia) increases with aging, the contribution of muscle fatigue to age-related dysphagia is an emerging area of interest. The use of animal models, such as mice and rats (murine models) allows experimental paradigms for studying the relationship between muscle fatigue and swallowing function with a high degree of biological precision that is not possible in human studies. The goal of this article is to review basic experimental approaches to the study of murine tongue muscle fatigue related to dysphagia. Traditionally, murine muscle fatigue has been studied in limb muscles through direct muscle stimulation and behavioral exercise paradigms. As such, physiological and bioenergetic markers of muscle fatigue that have been validated in limb muscles may be applicable in studies of cranial muscle fatigue with appropriate modifications to account for differences in muscle architecture, innervation ratio, and skeletal support. Murine exercise paradigms may be used to elicit acute fatigue in tongue muscles, thereby enabling study of putative muscular adaptations. Using these approaches, hypotheses can be developed and tested in mice and rats to allow for future focused studies in human subjects geared toward developing and optimizing treatments for age-related dysphagia.

Destruction of Vowel Space Area in Patients with Dysphagia after Stroke

Dysphagia is associated with dysarthria in stroke patients. Vowel space decreases in stroke patients with dysarthria; destruction of the vowel space is often observed. We determined the correlation of destruction of acoustic vowel space with dysphagia in stroke patients. Seventy-four individuals with dysphagia and dysarthria who had experienced stroke were enrolled. For /a/, /ae/, /i/, and /u/ vowels, we determined formant parameter (it reflects vocal tract resonance frequency as a two-dimensional coordinate point), formant centralization ratio (FCR), and quadrilateral vowel space area (VSA). Swallowing function was assessed using the videofluoroscopic dysphagia scale (VDS) during videofluoroscopic swallowing studies. Pearson's correlation and linear regression were used to determine the correlation between VSA, FCR, and VDS. Subgroups were created based on VSA; vowel space destruction groups were compared using ANOVA and Scheffe's test. VSA and FCR were negatively and positively correlated with VDS, respectively. Groups were separated based on mean and standard deviation of VSA. One-way ANOVA revealed significant differences in VDS, FCR, and age between the VSA groups and no significant differences in VDS between mild and moderate VSA reduction and vowel space destruction groups. VSA and FCR values correlated with swallowing function. Vowel space destruction has characteristics similar to VSA reduction at a moderate-to-severe degree and has utility as an indicator of dysphagia severity.

Clinical determinants and neural correlates of presbyphagia in community-dwelling older adults

Background

“Presbyphagia” refers to characteristic age-related changes in the complex neuromuscular swallowing mechanism. It has been hypothesized that cumulative impairments in multiple domains affect functional reserve of swallowing with age, but the multifactorial etiology and postulated compensatory strategies of the brain are incompletely understood. This study investigates presbyphagia and its neural correlates, focusing on the clinical determinants associated with adaptive neuroplasticity.

Materials and methods

64 subjects over 70 years of age free of typical diseases explaining dysphagia received comprehensive workup including flexible endoscopic evaluation of swallowing (FEES), magnetoencephalography (MEG) during swallowing and pharyngeal stimulation, volumetry of swallowing muscles, laboratory analyzes, and assessment of hand-grip-strength, nutritional status, frailty, olfaction, cognition and mental health. Neural MEG activation was compared between participants with and without presbyphagia in FEES, and associated clinical influencing factors were analyzed. Presbyphagia was defined as the presence of oropharyngeal swallowing alterations e.g., penetration, aspiration, pharyngeal residue pooling or premature bolus spillage into the piriform sinus and/or laryngeal vestibule.

Results

32 of 64 participants showed swallowing alterations, mainly characterized by pharyngeal residue, whereas the airway was rarely compromised. In the MEG analysis, participants with presbyphagia activated an increased cortical sensorimotor network during swallowing. As major clinical determinant, participants with swallowing alterations exhibited reduced pharyngeal sensation. Presbyphagia was an independent predictor of a reduced nutritional status in a linear regression model.

Conclusions

Swallowing alterations frequently occur in otherwise healthy older adults and are associated with decreased nutritional status. Increased sensorimotor cortical activation may constitute a compensation attempt to uphold swallowing function due to sensory decline. Further studies are needed to clarify whether the swallowing alterations observed can be considered physiological per se or whether the concept of presbyphagia may need to be extended to a theory with a continuous transition between presbyphagia and dysphagia.

Cross-Cultural Brain Activity Differences Between True and Sham Acupuncture for Xerostomia During Head and Neck Cancer Radiotherapy

Background:

A prior phase III, multicenter (United States and China), clinical trial found true acupuncture (TA) resulted in lower xerostomia scores 12 months after radiotherapy than that of a standard care control group. This small pilot study examined brain function changes comparing TA to sham acupuncture (SA) in US and Fudan patients undergoing head and neck radiotherapy.

Methods:

To determine cerebral activity during TA versus SA acupuncture, patients underwent electroencephalogram evaluation (EEG) immediately prior, during and after both conditions. Acupuncture occurred during weeks 3 to 5 of radiotherapy, with patients receiving either TA or SA, followed 2 to 3 days later by the other treatment in a counterbalanced manner.

Results:

In the TA minus SA condition (N = 14 Fudan; N = 13 US), most changes were in the delta (0.5-3.5 Hz) and alpha (8-12 Hz) bandwidths. Delta was present in the frontal gyrus and parahippocampal gyrus. Alpha was present in the anterior and posterior cingulate, lingual gyrus, amygdala, precuneus, medial frontal gyrus, fusiform gyrus, and superior frontal gyrus. Maximal cortical differences in the Fudan cohort between TA and SA were in areas previously shown to be associated with (TA). In the US cohort, maximal differences between TA and SA were associated with areas which are usually decreased in TA conditions.

Conclusions:

There were distinct differences in brain function between those receiving TA and SA and there were clear differences between cultures, helping to explain the lack of placebo effect in the Fudan participants and strong placebo effect in the US patients.

Association between Dysphagia and Frailty in Older Adults: A Systematic Review and Meta-Analysis

BACKGROUND

Increasing bodies of epidemiological evidence indicate potential associations between dysphagia and the risk of frailty in older adults. We hypothesized that older adults with symptoms of dysphagia might have a higher prevalence of frailty or prefrailty than those without dysphagia.

METHODS

We systematically searched the PubMed, Embase, and Cochrane Library databases for relevant studies published through 20 April 2022. Cross-sectional and longitudinal studies that examined the associations between dysphagia and the existence of frailty or prefrailty in community-dwelling, facility-dwelling, or hospitalized adults aged 50 years or older were synthesized. The Newcastle-Ottawa Scale was used to evaluate study quality.

RESULTS

The meta-analysis comprised 12 cohorts, including 5,503,543 non-frailty participants and 735,303 cases of frailty or prefrailty. Random-effect meta-analysis demonstrated a significant association between dysphagia and the risk of frailty and prefrailty (OR, 3.24; 95% CI, 2.51-4.20). In addition, we observed consistent results across the subgroups and heterogeneity assessments.

CONCLUSIONS

We propose including dysphagia assessment as a critical factor in the cumulative deficit model for identifying frailty in older adults. Understanding dysphagia and the potential role of nutritional supplements in older adults may lead to improved strategies for preventing, delaying, or mitigating frailty.

How the motor system copes with aging: a quantitative meta-analysis of the effect of aging on motor function control

Motor cognitive functions and their neurophysiology evolve and degrade along the lifespan in a dramatic fashion. Current models of how the brain adapts to aging remain inspired primarily by studies on memory or language processes. Yet, aging is strongly associated with reduced motor independence and the associated degraded interaction with the environment: accordingly, any neurocognitive model of aging not considering the motor system is, ipso facto, incomplete. Here we present a meta-analysis of forty functional brain-imaging studies to address aging effects on motor control. Our results indicate that motor control is associated with aging-related changes in brain activity, involving not only motoric brain regions but also posterior areas such as the occipito-temporal cortex. Notably, some of these differences depend on the specific nature of the motor task and the level of performance achieved by the participants. These findings support neurocognitive models of aging that make fewer anatomical assumptions while also considering tasks-dependent and performance-dependent manifestations. Besides the theoretical implications, the present data also provide additional information for the motor rehabilitation domain, indicating that motor control is a more complex phenomenon than previously understood, to which separate cognitive operations can contribute and decrease in different ways with aging.

Many aspects of neuronal control degrade with ageing, including motor control. Using a meta-analysis of functional MRI images, it is made apparent that the ageing brain relies more on visual strategies than sensory stimuli to maintain motor function.

Analysis of Factors That Influence the Prognosis of Swallowing Function Rehabilitation Therapy in Patients with Dysphagia After Medullary Infarction

PURPOSE

This study investigated the factors that influence the prognosis of swallowing function rehabilitation therapy in patients with dysphagia after medullary infarction.

PATIENTS AND METHODS

This retrospective study was conducted using the clinical data of 51 patients who were diagnosed with dysphagia after medullary infarction and hospitalized at our institution between January 2019 and January 2021. As per the water swallow test (WST) grade at 1 month after rehabilitation treatment, patients were classified into the good prognosis group and the poor prognosis group. Univariate analysis as well as univariate and multivariate logistic regression analysis were used to analyze factors that influence the prognosis of swallowing function rehabilitation therapy in patients with dysphagia after medullary infarction. Receiver operating characteristic (ROC) curves were then used to test the predictive ability of the significant parameters to predict the prognosis of the rehabilitation therapy in these patients.

RESULTS

Univariate analysis and univariate logistic regression analysis showed that previous stroke (odds ratio [OR] = 1.361), dysarthria (OR = 3.771), disease course (OR = 1.112), National Institutes of Health Stroke Scale (NIHSS) score at admission (OR = 2.596), and infarct site (OR = 11.071) were all significantly correlated with the prognosis of swallowing function rehabilitation therapy in patients with dysphagia after medullary infarction (P < 0.05). Multivariate logistic regression analysis showed that dysarthria (OR = 5.519, 95% confidence interval (CI) 1.413-21.566), infarct site (OR = 18.634, 95% CI 1.696-204.73), and the NIHSS score (OR = 1.001, 95% CI 1.536-4.820) were independent influencing factors of the prognosis of swallowing function rehabilitation therapy in these patients. The ROC curve showed that the area under the curve for the combined prediction of the three indicators was 0.943.

CONCLUSION

The NIHSS score, dysarthria, and infarct site are independent influencing factors for the prognosis of swallowing function rehabilitation therapy in patients with dysphagia after medullary infarction.

Advancing Laryngeal Adductor Reflex Testing Beyond Sensory Threshold Detection

Flexible endoscopic evaluation of swallowing with sensory testing (FEESST) is a promising clinical tool to assess airway integrity via the laryngeal adductor reflex (LAR). The current clinical protocol relies on sensory threshold detection, as relatively little is known about the motor response of this sensorimotor airway protective reflex. Here, we focused on characterizing normative LAR motion dynamics in 20 healthy young participants using our prototype high-pressure syringe-based air pulse device and analytic software (VFtrack™) that tracks vocal fold (VF) motion in endoscopic videos. Following device bench testing for air pulse stimulus characterization, we evoked and objectively quantified LAR motion dynamics in response to two suprathreshold air pulse stimuli (40 versus 60 mm Hg), delivered to the arytenoid mucosa through a bronchoscope working channel. The higher air pressures generated by our device permitted an approximate 1 cm endoscope working distance for continual visualization of the bilateral VFs throughout the LAR. Post hoc video analysis identified two main findings: (1) there are variant and invariant subcomponents of the LAR motor response, and (2) only a fraction of suprathreshold stimuli evoked complete glottic closure during the LAR. While the clinical relevance of these findings remains to be determined, we have nonetheless demonstrated untapped potential in the current FEESST protocol. Our ongoing efforts may reveal LAR biomarkers to quantify the severity of laryngeal pathology and change over time with natural disease progression, spontaneous recovery, or in response to intervention. The ultimate goal is to facilitate predictive modeling of patients at high risk for dysphagia-related aspiration pneumonia.

Evaluation of the Swallowing and Voice Functions in Ankylosing Spondylitis Patients

This study aimed to evaluate the swallowing and voice functions in patients with ankylosing spondylitis. Thirty patients with ankylosing spondylitis (Group 1) and 30 healthy individuals (Group 2) were included in the study. Following the laryngoscopic evaluation of the patients, the fiberoptic endoscopic evaluation of swallowing was performed, and then, the penetration-aspiration score was determined. The participants were asked to fill the eating assessment tool form. Voice recordings obtained to evaluate sound disorders were measured acoustically and analyzed using the PRAAT program. In terms of swallowing, the penetration-aspiration score obtained as a result of the flexible endoscopic swallowing assessment and eating assessment tool score was found to be higher in Group 1 than in Group 2, and a statistically significant difference was noted (p ≤ 0.001). When analyzing the maximum phonation time (p < 0.001) and fundamental frequency (p = 0.408) values in phonation evaluation, a statistically significant difference was found between the two groups. Group 1 showed a deterioration in terms of jitter (p = 0.040) and shimmer (p = 0.007) compared to Group 2, and a statistically significant difference was noted. There was no statistically significant difference in the harmonic/noise ratio (mean ± standard deviation) between the two groups (p = 0.051). Swallowing and voice functions significantly affect quality of life. Therefore, approaches aimed to improve the associated symptoms have become increasingly important. In patients with ankylosing spondylitis, swallowing quality and phonation ability may be negatively affected. These patients should be monitored for hidden or overt food aspiration.Trial Registry: https://clinicaltrials.gov/ct2/show/NCT04437394.

The Influence of Age, Eating a Meal, and Systematic Fatigue on Swallowing and Mealtime Parameters

Fatigue is widely accepted as a clinically relevant factor in the diagnosis, treatment, and management of dysphagia. Despite the relative importance that is placed on swallowing-related fatigue, the occurrence and effects of fatigue during swallowing is unclear. The goal of this study was to explore effects of eating a meal on measures of tongue strength, endurance, and other parameters of swallowing function under normal conditions compared to when the tongue is intentionally fatigued. Thirty healthy females, 15 "Young" (18-35 years old), and 15 "Old" (70 + years old) were seen for two data collection sessions one week apart. On both days, pre-meal measures were collected, then participants consumed a standardized meal based on a previously published protocol (half a bagel with peanut butter and 8 baby carrots) followed by post-meal measures. An additional pre-meal fatigue task was included on one of the test days (counterbalanced), involving maximal tongue presses until participants could not achieve 40% of baseline maximum pressure. Pre- and post-meal measures included anterior and posterior maximum tongue pressures, saliva swallow pressure, tongue endurance, surface electromyography (sEMG), the modified Borg scale, and the Test of Mastication and Swallowing of Solids (TOMASS). Linear mixed effects regressions compared pre- and post-meal outcome measures (1) on the non-fatigue day and (2) between fatigue and non-fatigue days while controlling for participant and age. The fatigue task caused significant reductions in maximum anterior and posterior tongue pressure. After a normal meal (i.e., without fatigue), we found decreased anterior pressures in the older group only. Older participants also had decreased saliva swallow pressures after the meal compared to pre-meal, while this measure increased post-mean in the young participants. When compared to the non-fatigue meal, eating a meal after tongue fatigue resulted in significantly lower post-meal posterior pressures, regardless of age group. The same pattern was observed with posterior functional reserve. Our results demonstrate that a systematic, participant-specific tongue fatigue task induced measurable changes in maximum tongue pressure. A meal by itself was observed to reduce anterior tongue strength and saliva swallow pressures only in older participants. Overall, it appears that older adults may be more vulnerable to fatigue-induced changes in tongue strength, though the relationship between these measures and changes to functional swallowing remains unknown.

Investigation of Embodied Language Processing on Command-Swallow Performance in Healthy Participants

Purpose During videofluoroscopic examination of swallowing, patients commonly are instructed to hold a bolus in their mouth until they hear a verbal instruction to swallow, which usually consists of the word swallow and is commonly referred to as the command swallow condition. The language-induced motor facilitation theory suggests that linguistic processes associated with the verbal command to swallow should facilitate the voluntary component of swallowing. As such, the purpose of the study was to examine the linguistic influences of the verbal command on swallowing. Method Twenty healthy young adult participants held a 5-ml liquid bolus in their mouth and swallowed the bolus after hearing one of five acoustic stimuli presented randomly: congruent action word (swallow), incongruent action word (cough), congruent pseudoword (spallow), incongruent pseudoword (pough), and nonverbal stimulus (1000-Hz pure tone). Suprahyoid muscle activity during swallowing was measured via surface electromyography (sEMG). Results The onset and peak sEMG latencies following the congruent action word swallow were shorter than latencies following the pure tone and pseudowords but were not different from the incongruent action word. The lack of difference between swallow and cough did not negate the positive impact of real words on timing. In contrast to expectations, sEMG activity duration and rise time were longer following the word swallow than the pure tone and pseudowords but were not different from cough. No differences were observed for peak suprahyoid muscle activity amplitude and fall times. Conclusions Language facilitation was observed in swallowing. The clinical utility of the information obtained in the study may depend on the purposes for using the command swallow and the type of patient being assessed. However, linguistic processing under the command swallow condition may alter swallow behaviors and suggests that linguistic inducement could be useful as a compensatory technique for patients with difficulty initiating oropharyngeal swallows.

Effects of aging on brain networks during swallowing: general linear model and independent component analyses

Swallowing disorders occur more frequently in older adults. However, the effects of the aging process on neural activation when swallowing are unclear. We aimed to identify neural regions activated during swallowing and evaluate changes in neural activation and neural networks with aging. Using a general linear model (GLM) and independent component (IC) analyses, blood oxygen level-dependent (BOLD) signals were observed in the lateral precentral gyrus, postcentral gyrus, anterior insular cortices, supramarginal gyri, and medial frontal gyrus during swallowing. The right thalamus and anterior cingulate gyri were found to be active areas by GLM and IC analyses, respectively. In the correlational analyses, age was negatively correlated with BOLD signals of the lateral precentral gyri, postcentral gyri, and insular cortices in swallowing tasks. Additionally, correlation analyses between ICs of all participants and age revealed negative correlations in the right supramarginal gyrus, both anterior cingulate cortices, putamen, and cerebellum. In the network analysis, the BOLD signal positively correlated with age in the default mode network (DMN), and was negatively correlated in the lateral precentral gyri, postcentral gyri, and insular cortices. The amplitude of low-frequency fluctuations was significantly decreased in the DMN and increased in swallowing-related areas during swallowing tasks. These results suggest that aging has negative effects on the activation of swallowing-related regions and task-induced deactivation of the DMN. These changes may be used to detect early functional decline during swallowing.

Targeting the sensory feedback within the swallowing network-Reversing artificially induced pharyngolaryngeal hypesthesia by central and peripheral stimulation strategies

Pharyngolaryngeal hypesthesia is a major reason for dysphagia in various neurological diseases. Emerging neuromodulation devices have shown potential to foster dysphagia rehabilitation, but the optimal treatment strategy is unknown. Because functional imaging studies are difficult to conduct in severely ill patients, we induced a virtual sensory lesion in healthy volunteers and evaluated the effects of central and peripheral neurostimulation techniques. In a sham-controlled intervention study with crossover design on 10 participants, we tested the potential of (peripheral) pharyngeal electrical stimulation (PES) and (central) transcranial direct current stimulation (tDCS) to revert the effects of lidocaine-induced pharyngolaryngeal hypesthesia on central sensorimotor processing. Changes were observed during pharyngeal air-pulse stimulation and voluntary swallowing applying magnetoencephalography before and after the interventions. PES induced a significant (p < .05) increase of activation during swallowing in the bihemispheric sensorimotor network in alpha and low gamma frequency ranges, peaking in the right premotor and left primary sensory area, respectively. With pneumatic stimulation, significant activation increase was found after PES in high gamma peaking in the left premotor area. Significant changes of brain activation after tDCS could neither be detected for pneumatic stimulation nor for swallowing. Due to the peripheral cause of dysphagia in this model, PES was able to revert the detrimental effects of reduced sensory input on central processing, whereas tDCS was not. Results may have implications for therapeutic decisions in the clinical context.

Targeting Chemosensory Ion Channels in Peripheral Swallowing-Related Regions for the Management of Oropharyngeal Dysphagia

Oropharyngeal dysphagia, or difficulty in swallowing, is a major health problem that can lead to serious complications, such as pulmonary aspiration, malnutrition, dehydration, and pneumonia. The current clinical management of oropharyngeal dysphagia mainly focuses on compensatory strategies and swallowing exercises/maneuvers; however, studies have suggested their limited effectiveness for recovering swallowing physiology and for promoting neuroplasticity in swallowing-related neuronal networks. Several new and innovative strategies based on neurostimulation in peripheral and cortical swallowing-related regions have been investigated, and appear promising for the management of oropharyngeal dysphagia. The peripheral chemical neurostimulation strategy is one of the innovative strategies, and targets chemosensory ion channels expressed in peripheral swallowing-related regions. A considerable number of animal and human studies, including randomized clinical trials in patients with oropharyngeal dysphagia, have reported improvements in the efficacy, safety, and physiology of swallowing using this strategy. There is also evidence that neuroplasticity is promoted in swallowing-related neuronal networks with this strategy. The targeting of chemosensory ion channels in peripheral swallowing-related regions may therefore be a promising pharmacological treatment strategy for the management of oropharyngeal dysphagia. In this review, we focus on this strategy, including its possible neurophysiological and molecular mechanisms.

Swallow Motor Pattern Is Modulated by Fixed or Stochastic Alterations in Afferent Feedback

Afferent feedback can appreciably alter the pharyngeal phase of swallow. In order to measure the stability of the swallow motor pattern during several types of alterations in afferent feedback, we assessed swallow during a conventional water challenge in four anesthetized cats, and compared that to swallows induced by fixed (20 Hz) and stochastic (1-20Hz) electrical stimulation applied to the superior laryngeal nerve. The swallow motor patterns were evaluated by electromyographic activity (EMG) of eight muscles, based on their functional significance: laryngeal elevators (mylohyoid, geniohyoid, and thyrohyoid); laryngeal adductor (thyroarytenoid); inferior pharyngeal constrictor (thyropharyngeus); upper esophageal sphincter (cricopharyngeus); and inspiratory activity (parasternal and costal diaphragm). Both the fixed and stochastic electrical stimulation paradigms increased activity of the laryngeal elevators, produced short-term facilitation evidenced by increasing swallow durations over the stimulus period, and conversely inhibited swallow-related diaphragm activity. Both the fixed and stochastic stimulus conditions also increased specific EMG amplitudes, which never occurred with the water challenges. Stochastic stimulation increased swallow excitability, as measured by an increase in the number of swallows produced. Consistent with our previous results, changes in the swallow motor pattern for pairs of muscles were only sometimes correlated with each other. We conclude that alterations in afferent feedback produced particular variations of the swallow motor pattern. We hypothesize that specific SLN feedback might modulate the swallow central pattern generator during aberrant feeding conditions (food/liquid entering the airway), which may protect the airway and serve as potentially important clinical diagnostic indicators.

An fMRI Study of the Brain Network Involved in Teeth Tapping in Elderly Adults

Cortical activity during jaw movement has been analyzed using various non-invasive brain imaging methods, but the contribution of orofacial sensory input to voluntary jaw movements remains unclear. In this study, we used functional magnetic resonance imaging (fMRI) to observe brain activities during a simple teeth tapping task in adult dentulous (AD), older dentulous (OD), and older edentulous subjects who wore dentures (OEd) or did not wear dentures (OE) to analyze their functional network connections. (1) To assess the effect of age on natural activation patterns during teeth tapping, a comparison of groups with natural dentition—AD and OD—was undertaken. A general linear model analysis indicated that the major activated site in the AD group was the primary sensory cortex (SI) and motor cortex (MI) (p < 0.05, family wise error corrected). In the OD group, teeth tapping induced brain activity at various foci (p < 0.05, family wise error corrected), including the SI, MI, insula cortex, supplementary motor cortex (SMC)/premotor cortex (PMA), cerebellum, thalamus, and basal ganglia in each group. (2) Group comparisons between the OD and OEd subjects showed decreased activity in the SI, MI, Brodmann’s area 6 (BA6), thalamus (ventral posteromedial nucleus, VPM), basal ganglia, and insular cortex (p ¡ 0.005, uncorrected). This suggested that the decreased S1/M1 activity in the OEd group was related to missing teeth, which led to reduced periodontal afferents. (3) A conjunction analysis in the OD and OEd/OE groups revealed that commonly activated areas were the MI, SI, cerebellum, BA6, thalamus (VPM), and basal ganglia (putamen; p < 0.05, FWE corrected). These areas have been associated with voluntary movements. (4) Psychophysiological interaction analysis (OEd vs OE) showed that subcortical and cortical structures, such as the MI, SI, DLPFC, SMC/PMA, insula cortex, basal ganglia, and cerebellum, likely function as hubs and form an integrated network that participates in the control of teeth tapping. These results suggest that oral sensory inputs are involved in the control of teeth tapping through feedforward control of intended movements, as well as feedback control of ongoing movements.

Functional Adaptation of Oromotor Functions and Aging: A Focused Review of the Evidence From Brain Neuroimaging Research

“Practice makes perfect” is a principle widely applied when one is acquiring a new sensorimotor skill to cope with challenges from a new environment. In terms of oral healthcare, the traditional view holds that restoring decayed structures is one of the primary aims of treatment. This assumes that the patient’s oromotor functions would be recovered back to normal levels after the restoration. However, in older patients, such a structural–functional coupling after dental treatment shows a great degree of individual variations. For example, after prosthodontic treatment, some patients would adapt themselves quickly to the new dentures, while others would not. In this Focused Review, I argue that the functional aspects of adaptation—which would be predominantly associated with the brain mechanisms of cognitive processing and motor learning—play a critical role in the individual differences in the adaptive behaviors of oromotor functions. This thesis is critical to geriatric oral healthcare since the variation in the capacity of cognitive processing and motor learning is critically associated with aging. In this review, (a) the association between aging and the brain-stomatognathic axis will be introduced; (b) the brain mechanisms underlying the association between aging, compensatory behavior, and motor learning will be briefly summarized; (c) the neuroimaging evidence that suggests the role of cognitive processing and motor learning in oromotor functions will be summarized, and critically, the brain mechanisms underlying mastication and swallowing in older people will be discussed; and (d) based on the current knowledge, an experimental framework for investigating the association between aging and the functional adaptation of oromotor functions will be proposed. Finally, I will comment on the practical implications of this framework and postulate questions open for future research.

Effects of Motor Imagery and Visual Neurofeedback on Activation in the Swallowing Network: A Real-Time fMRI Study

Motor imagery of movements is used as mental strategy in neurofeedback applications to gain voluntary control over activity in motor areas of the brain. In the present functional magnetic resonance imaging (fMRI) study, we first addressed the question whether motor imagery and execution of swallowing activate comparable brain areas, which has been already proven for hand and foot movements. Prior near-infrared spectroscopy (NIRS) studies provide evidence that this is the case in the outer layer of the cortex. With the present fMRI study, we want to expand these prior NIRS findings to the whole brain. Second, we used motor imagery of swallowing as mental strategy during visual neurofeedback to investigate whether one can learn to modulate voluntarily activity in brain regions, which are associated with active swallowing, using real-time fMRI. Eleven healthy adults performed one offline session, in which they executed swallowing movements and imagined swallowing on command during fMRI scanning. Based on this functional localizer task, we identified brain areas active during both tasks and defined individually regions for feedback. During the second session, participants performed two real-time fMRI neurofeedback runs (each run comprised 10 motor imagery trials), in which they should increase voluntarily the activity in the left precentral gyrus by means of motor imagery of swallowing while receiving visual feedback (the visual feedback depicted one's own fMRI signal changes in real-time). Motor execution and imagery of swallowing activated a comparable network of brain areas including the bilateral pre- and postcentral gyrus, inferior frontal gyrus, basal ganglia, insula, SMA, and the cerebellum compared to a resting condition. During neurofeedback training, participants were able to increase the activity in the feedback region (left lateral precentral gyrus) but also in other brain regions, which are generally active during swallowing, compared to the motor imagery offline task. Our results indicate that motor imagery of swallowing is an adequate mental strategy to activate the swallowing network of the whole brain, which might be useful for future treatments of swallowing disorders.

A Systematic Review of Physiological Changes in Swallowing in the Oldest Old

Age-related swallowing changes are well-researched in deglutology, usually distinguishing those over 60 years as older aged. World-wide, older adults are healthier and forecast to live longer: many over 85 years. It is necessary for clinicians to understand healthy swallowing changes in this 'oldest old' in order to appropriately manage swallowing complaints in older patients. This systematic review collated and critically appraised studies investigating swallowing changes in adults over 85 years using instrumental assessment. Criteria for inclusion were healthy subjects over 85 years. Exclusion criteria included studies focused on anatomy and oral processing. Studies published until December 2018 were retrieved from BIOSIS, CINAHL, Embase, Medline, and Scopus, totaling 2125 articles. During data screening, 64% of studies investigating age-related swallowing changes were excluded, as the oldest old were not recruited. After PRISMA screening, 44 articles met criteria. These were further reviewed for data extraction, bias and quality. Main quantitative age-related changes in swallowing included increases in delay in swallow onset, bolus transit times, duration of UES opening, pressure above the UES and UES relaxation pressure, and reduction in pressure at the UES. Few studies detected increased residue or airway compromise in the form of aspiration. Results were not easily comparable due to differences in age ranges, methods for deeming participants 'healthy', measures used to define swallowing physiology, and swallowing tasks. Age-related swallowing changes are identified that do not compromise safety. The oldest old are underrepresented in normative deglutition research. It is essential future studies plan accordingly to recruit those over 85 years.

Factors Influencing Oral Intake Improvement and Feeding Tube Dependency in Patients with Poststroke Dysphagia

OBJECTIVE

To assess ischemic stroke patients regarding the relationship between lesion locations, swallowing impairment, medical and demographic factors and (1) oral intake improvement and (2) feeding tube dependency at discharge from their acute hospital stay.

METHODS

We conducted an exploratory, retrospective observational longitudinal cohort study of acute, first-ever, ischemic stroke patients. Patients who had an initial nonoral feeding recommendation from a speech and language pathologist and who underwent a modified barium swallow study within their hospital stay were included. Oral intake status was measured with the Functional Oral Intake Scale (FOIS) as the change in FOIS during the hospital stay and as feeding tube dependency at hospital discharge. Associations were assessed with multiple linear regression modeling controlling for age, comorbidities, and hospital length of stay.

RESULTS

We included 44 stroke patients. At hospital discharge, 93% of patients had oral intake restrictions and 30% were feeding tube dependent. Following multiple linear regression modeling, age, damage to the left superior frontal gyrus, dorsal anterior cingulate gyrus, hypothalamus, and nucleus accumbens were significant predictors for FOIS change. Feeding tube dependency showed no significant associations with any prognostic variables when controlling for confounders.

CONCLUSIONS

The vast majority of patients with an initial nonoral feeding recommendation are discharged with oral intake restrictions indicating a continued need for swallowing assessments and treatment after discharge. Lesion locations associated with motivation, reward, and drive to consume food as well as swallowing impairment, higher age, and more comorbidities were related to less oral intake improvement.

Mapping acute lesion locations to physiological swallow impairments after stroke

Dysphagia is a common deficit after a stroke, and it is frequently associated with pneumonia, malnutrition, dehydration, and poor quality of life. It is not yet fully clear which brain regions are directly related to swallowing, and how lesions affect swallow physiology. This study aimed to assess the statistical relationship between acute stroke lesion locations and impairment of specific aspects of swallow physiology. We performed lesion symptom mapping with 68 retrospectively recruited, acute, first-ever ischemic stroke patients. Lesions were determined on diffusion weighted MRI scans. Post-stroke swallow physiology was determined using the Modified Barium Swallow Study Impairment Profile (MBSImP©™). The relationship between brain lesion location and 17 physiological aspects of swallowing were tested using voxel-based and region-based statistical associations corrected for multiple comparisons using permutation thresholding. We found that laryngeal elevation, anterior hyoid excursion, laryngeal vestibular closure, and pharyngeal residue were associated with lesioned voxels or regions of interests. All components showed distinct and overlapping lesion locations, mostly in the right hemisphere, and including cortical regions (inferior frontal gyrus, pre- and postcentral gyrus, supramarginal gyrus, angular gyrus, superior temporal gyrus, insula), subcortical regions (thalamus, amygdala) and white matter tracts (superior longitudinal fasciculus, corona radiata, internal capsule, external capsule, ansa lenticularis, lenticular fasciculus). Our findings indicate that different aspects of post-stroke swallow physiology are associated with distinct lesion locations, primarily in the right hemisphere, and primarily including sensory-motor integration areas and their corresponding white matter tracts. Future studies are needed to expand on our findings and thus, support the development of a neuroanatomical model of post-stroke swallow physiology and treatment approaches targeting the neurophysiological underpinnings of swallowing post stroke.

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Different aspects of swallow physiology are associated with distinct stroke lesion locations.

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Sensory-motor integration areas and white matter tracts are crucial for swallow physiology.

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Mostly regions in the right and only few in the left hemisphere contribute to swallow physiology.

Influence of Body Height on Oral and Pharyngeal Transit Time of a Liquid Bolus in Healthy Volunteers

BACKGROUND

Swallowing duration may be influenced by several factors. The effect of body height on oral-pharyngeal bolus transit has not been clearly elucidated. The hypothesis of this investigation was that height has influence on oral-pharyngeal transit time of a liquid bolus.

METHODS

Videofluoroscopic assessment of swallowing was performed on 40 healthy volunteers: 20 "tall" (171 cm to 207 cm) and 20 "short" (152 cm to 170 cm) subjects, 10 men and 10 women in each group. Each subject performed three swallows of 10 mL of liquid barium bolus. The following parameters were measured: oral transit time (OTT): time from the beginning of tongue tip movement at incisors to arrival of the bolus tail at the fauces; pharyngeal transit time (PTT): time between the arrival of the bolus tail at fauces and complete passage of the bolus tail through the upper esophageal sphincter (UES); pharyngeal clearance (PC): time between the arrival of the bolus head at fauces to complete passage of the bolus tail through the UES; UES opening (UESO): time between the arrival of the bolus head at the UES to complete passage of the bolus tail through the UES; duration of hyoid movement (HM): time interval between the onset and the end of hyoid movement; oral-pharyngeal transit time (OPTT): time from the beginning of tongue tip movement at incisors until complete passage of the bolus tail through the UES. The statistical analysis was done by a linear model with mixed effects. Correlation between height and swallowing events duration was assessed by Spearman's correlation coefficient (r).

RESULTS

In women OTT, PC, HM and OPTT were longer in tall than in short subjects, what was not seen in men. In women there was a positive correlation between OTT, PTT and OPTT and height. Men (mean height: 177 cm) had longer PTT and PC than women (mean height: 166 cm).

CONCLUSIONS

In women, oral and pharyngeal transit time of a 10 mL liquid bolus were influenced by height and was longer in taller subjects.

Differences in swallow physiology in patients with left and right hemispheric strokes

BACKGROUND

We sought to determine the impact of lesion lateralization and lesion volume on swallow impairment on group-level by comparing patients with left and right hemisphere strokes and on patient-level by analyzing patients individually.

METHODS

We performed a retrospective, observational, cross-sectional study of 46 patients with unilateral (22 left, 24 right), acute, first-ever, ischemic strokes who received a diffusion weighted MRI (DW-MRI) and modified barium swallow study (MBSS) during their acute hospital stay. We determined lesion side on the DW-MRI and measured swallow physiology using the Modified Barium Swallow Impairment Profile (MBSImP™©), Penetration-Aspiration Scale (PAS), swallow timing, distance, area, and speed measures. We performed Pearson's Chi-Square and Wilcoxon Rank-Sum tests to compare patients with left and right hemisphere strokes, and Pearson or Spearman correlation, simple logistic regression, linear, and logistic multivariable regression modeling to assess the relationship between variables.

RESULTS

At the group-level, there were no differences in MBSImP oral swallow impairment scores between patients with left and right hemisphere stroke. In adjusted analyses, patients with right hemisphere strokes showed significantly worse MBSImP pharyngeal total scores (p = 0.02), worse MBSImP component specific scores for laryngeal vestibular closure (Bonferroni adjusted alpha p ≤ 0.0029), and worse PAS scores (p = 0.03). Patients with right hemisphere strokes showed worse timing, distance, area, and speed measures. Lesion volume was significantly associated with MBSImP pharyngeal residue (p = 0.03) and pharyngeal total scores (p = 0.04). At the patient-level, 24% of patients (4 left, 7 right) showed opposite patterns of MBSImP oral and pharyngeal swallow impairment than seen at group-level.

CONCLUSION

Our study showed differences in swallow physiology between patients with right and left unilateral strokes with patients with right hemisphere strokes showing worse pharyngeal impairment. Lesion lateralization seems to be a valuable marker for the severity of swallowing impairment at the group-level but less informative at the patient-level.

Swallowing and Temporomandibular Disorders in Adults

INTRODUCTION

Temporomandibular disease (TMD) etiology is multifactorial and is related to many perpetuating, predisposing, and initiating factors. The daytime parafunctions may have an important role in TMD pathogenesis. The most frequent parafunctions analyzed were the static parafunction (ie, clenching) and the dynamic parafunction (ie, grinding). In the present paper, the authors evaluated the swallowing (an oral function/parafunction) with the surface electromyography in patients with TMD.

MATERIALS AND METHODS

Twenty patients with TMD problems (nonhealthy patients, NHP) (mean age: 33 ± 1.994; 8 men and 12 women) and 20 healthy matched subjects (HP) (34.4 ± 2.782; 6 men and 14 women) were selected and examined. On each patient, an 8-channel surface electromyography was done during saliva swallowing.

RESULTS

Nonhealthy patients presented higher masseter and temporalis activation (P < 0.05) and an unbalancing of temporalis and submental muscles activation (P < 0.05) than the HP.

DISCUSSION

Nonhealthy patients presented a time of swallow higher than HP (P < 0.001). Nonhealthy patients presented a higher muscles activation and time of swallow than HP and a decrease of muscles balancing activation.

Hemodynamic signal changes during saliva and water swallowing: a near-infrared spectroscopy study

Here, we compared the hemodynamic response observed during swallowing of water or saliva using near-infrared spectroscopy (NIRS). Sixteen healthy adults swallowed water or saliva in a randomized order. Relative concentration changes in oxygenated and deoxygenated hemoglobin during swallowing were assessed. Both swallowing tasks led to the strongest NIRS signal change over the bilateral inferior frontal gyrus. Water swallowing led to a stronger activation over the right hemisphere while the activation focus for saliva swallowing was stronger left lateralized. The NIRS time course also differed between both swallowing tasks especially at the beginning of the tasks, which might be a sign of differences in task effort. Our results show that NIRS is a sensitive measure to reveal differences in the topographical distribution and time course of the hemodynamic response between distinct swallowing tasks and might be therefore an adequate diagnostic and therapy tool for swallowing difficulties.

Periventricular White Matter Lesions as a Prognostic Factor of Swallowing Function in Older Patients with Mild Stroke

Older patients with stroke have poor functional prognosis compared to younger patients. Patients with stroke who have severe white matter (WM) lesions have been reported to have poor functional prognosis such as cognitive dysfunction, increased propensity for falling, and gait and balance problems. The aim of this study was to determine whether WM lesions exert negative effects on swallowing function in older patients with mild stroke. We conducted a retrospective analysis of 63 patients aged >65 years who had a National Institutes of Health Stroke Scale score ≤5 and who underwent videofluoroscopic swallowing examination after their first stroke. Linear regression analysis showed that oral transit time tended to increase as Fazekas grade increased (p = 0.003). In addition, inadequate mastication was related to the presence of lesions in the left hemisphere (p = 0.039). The presence of penetration could also be predicted by Fazekas grade (p = 0.015). Our findings suggest that WM lesions observed in brain magnetic resonance imaging scans can impact swallowing problems in older patients with mild stroke, regardless of initial stroke severity or other factors associated with lesion location. Accordingly, our data indicate that WM lesions are a predictive factor by which patients can be stratified into favorable or unfavorable outcomes with respect to dysphagia.

Spatiotemporal characteristics of the pharyngeal event-related potential in healthy subjects and older patients with oropharyngeal dysfunction

BACKGROUND

Oropharyngeal dysphagia (OD) is a highly prevalent symptom in older people. Appropriate oropharyngeal sensory feedback is essential for safe and efficient swallowing. However, pharyngeal sensitivity decreases with advancing age and could play a fundamental role in the physiopathology of swallowing dysfunction associated with aging. We aimed to characterize pharyngeal sensitivity and cortical response to a pharyngeal electrical stimulus in healthy volunteers (HV) and older patients with and without OD.

METHODS

Eight young HV, eight older HV without OD, and 14 older patients with OD were studied by electroencephalography through 32 scalp electrodes. Pharyngeal event-related potentials (ERP) were assessed following electrical stimulation of the pharynx. Sensory and tolerance thresholds to the electrical stimulus and latency, amplitude, and scalp current density of each ERP component were analyzed and compared. An ERP source localization study was also performed using the sLORETA software.

KEY RESULTS

Older participants (with and without OD) presented an increased sensory threshold to pharyngeal electrical stimulation (10.2 ± 1.7 mA and 11.5 ± 1.9 mA respectively), compared with young HV (6.0 ± 1.2 mA). The cortical activation of older HV in response to pharyngeal electrical stimulus was reduced compared with young HV (N2 amplitude: 0.22 ± 0.79 vs -3.10 ± 0.59, P<.05). Older patients with OD also presented disturbances to the pharyngo-cortical connection together with disrupted pattern of cortical activation.

CONCLUSIONS AND INFERENCES

Older people present a decline in pharyngeal sensory function, more severe in older patients with OD. This sensory impairment might be a critical pathophysiological element and a potential target for treatment of swallowing dysfunction in older patients.

Nonspecific effects of gap paradigm on swallowing

OBJECTIVE

Analogous to the gap paradigm in experiments for saccadic eye movements with very short reaction times, we hypothesized that the initiation of oropharyngeal swallowing movements guided by visual cues are encouraged under experimental conditions using a similar gap paradigm.

METHODS

A red visual cue indicating to hold a bolus in the mouth and a blue one indicating to swallow the bolus were sequentially provided on a computer display to 11 healthy participants. The gap period between these cues varied from 0 to 800ms. Swallowing kinetics and kinematics were recorded using surface electromyography and a laser displacement sensor, respectively.

RESULTS

In comparison with the no-gap paradigm, the delay from the onset of muscle activities to initiation of movement significantly decreased with a 100- (p<0.01) and 200-ms (p<0.005) gap period. With other gap periods, no significant change was detected in the delay.

CONCLUSIONS

Initiation of visually guided swallowing was enhanced by a gap paradigm of 100-200ms. Wrist flexion was boosted in a similar manner. Thus, the gap effect may be a generalized warning effect.

SIGNIFICANCE

Our findings might provide insights into the contribution of the basal ganglia to volitional swallowing.

Sour taste increases swallowing and prolongs hemodynamic responses in the cortical swallowing network

Sour stimuli have been shown to upregulate swallowing in patients and in healthy volunteers. However, such changes may be dependent on taste-induced increases in salivary flow. Other mechanisms include genetic taster status (Bartoshuk LM, Duffy VB, Green BG, Hoffman HJ, Ko CW, Lucchina LA, Weiffenbach JM. Physiol Behav 82: 109-114, 2004) and differences between sour and other tastes. We investigated the effects of taste on swallowing frequency and cortical activation in the swallowing network and whether taster status affected responses. Three-milliliter boluses of sour, sour with slow infusion, sweet, water, and water with infusion were compared on swallowing frequency and hemodynamic responses. The sour conditions increased swallowing frequency, whereas sweet and water did not. Changes in cortical oxygenated hemoglobin (hemodynamic responses) measured by functional near-infrared spectroscopy were averaged over 30 trials for each condition per participant in the right and left motor cortex, S1 and supplementary motor area for 30 s following bolus onset. Motion artifact in the hemodynamic response occurred 0-2 s after bolus onset, when the majority of swallows occurred. The peak hemodynamic response 2-7 s after bolus onset did not differ by taste, hemisphere, or cortical location. The mean hemodynamic response 17-22 s after bolus onset was highest in the motor regions of both hemispheres, and greater in the sour and infusion condition than in the water condition. Genetic taster status did not alter changes in swallowing frequency or hemodynamic response. As sour taste significantly increased swallowing and cortical activation equally with and without slow infusion, increases in the cortical swallowing were due to sour taste.

European Society for Swallowing Disorders - European Union Geriatric Medicine Society white paper: oropharyngeal dysphagia as a geriatric syndrome

This position document has been developed by the Dysphagia Working Group, a committee of members from the European Society for Swallowing Disorders and the European Union Geriatric Medicine Society, and invited experts. It consists of 12 sections that cover all aspects of clinical management of oropharyngeal dysphagia (OD) related to geriatric medicine and discusses prevalence, quality of life, and legal and ethical issues, as well as health economics and social burden. OD constitutes impaired or uncomfortable transit of food or liquids from the oral cavity to the esophagus, and it is included in the World Health Organization's classification of diseases. It can cause severe complications such as malnutrition, dehydration, respiratory infections, aspiration pneumonia, and increased readmissions, institutionalization, and morbimortality. OD is a prevalent and serious problem among all phenotypes of older patients as oropharyngeal swallow response is impaired in older people and can cause aspiration. Despite its prevalence and severity, OD is still underdiagnosed and untreated in many medical centers. There are several validated clinical and instrumental methods (videofluoroscopy and fiberoptic endoscopic evaluation of swallowing) to diagnose OD, and treatment is mainly based on compensatory measures, although new treatments to stimulate the oropharyngeal swallow response are under research. OD matches the definition of a geriatric syndrome as it is highly prevalent among older people, is caused by multiple factors, is associated with several comorbidities and poor prognosis, and needs a multidimensional approach to be treated. OD should be given more importance and attention and thus be included in all standard screening protocols, treated, and regularly monitored to prevent its main complications. More research is needed to develop and standardize new treatments and management protocols for older patients with OD, which is a challenging mission for our societies.

Wearing complete dentures is associated with changes in the three-dimensional shape of the oropharynx in edentulous older people that affect swallowing

OBJECTIVE

To investigate the effects of wearing complete dentures on pharyngeal shape for swallowing in edentulous older people.

BACKGROUND

In the absence of complete dentures, edentulous older people often lose the occlusal support necessary to position the mandible, which leads to an anterosuperior shift of the mandible during swallowing. This may result in pharyngeal shape changes effecting swallowing function in older people. However, the details of this phenomenon are currently unclear.

MATERIALS AND METHODS

Participants were 17 older edentulous volunteers. Cone-beam computed tomography imaging was performed with the participant in the seated position and wearing (i) both maxillary and mandibular dentures, (ii) maxillary dentures only and (iii) no dentures. During imaging, participants were instructed to keep their mouth closed to the mandibular position determined in advance during swallowing for each denture-wearing condition. The volume, height and average cross-sectional area of the velopharynx and oropharynx were measured, and the positions of the epiglottis and mandible were recorded.

RESULTS

While the vertical height of the oral cavity and pharynx significantly decreased, the volume and average cross-sectional area of the oropharynx significantly increased when dentures were not worn (p < 0.01). The absence of dentures caused an anterosuperior shift of the mandible when swallowing and drew the epiglottis forward, resulting in expansion of the oropharynx where the tongue base forms the anterior wall.

CONCLUSION

The absence of dentures results in anatomical changes in oropharyngeal shape that may exacerbate the pharyngeal expansion caused by ageing and reduce the swallowing reserve.