The Role of the Cerebellum in Swallowing

Device-based solutions supporting patients with swallowing problems

INTRODUCTION

Swallowing is a highly complex activity requiring the coordination of numerous muscles within the head and neck through connections from multiple areas within the central nervous system. Dysphagia is common and has long been known to lead to significant adverse effects on morbidity, mortality, and quality of life. Classical approaches toward dysphagia management involve input by clinical deglutologists who teach rehabilitative exercises and recommend alteration of the consistency of food and fluids. However, the evidence base in support of some of these approaches is inconsistent and requires further and larger studies to support their widespread implementation.

AREAS COVERED

This paper shall explore some of these novel techniques and explore the evidence that they will alter the future of dysphagia care.

EXPERT OPINION

Medical devices form one aspect of these rehabilitation strategies and over the past decade, numerous novel techniques targeting the complex swallowing sensorimotor pathway or swallowing associated musculature have come to prominence. These include interventions such as noninvasive brain stimulation, swallowing related biofeedback, and peripheral stimulation approaches, developed to bolster existing management methods. The evidence suggests that many of these approaches have the capability to enhance swallowing function and impact dysphagia recovery, however, more evidence is needed.

Age-Specific Clinical and Brain Features of Masticatory and Swallowing Performance

BACKGROUND

Mastication and swallowing are the fundamental processes for food intake and the primary functions of living. The clinical and neurological features associated with individual differences in masticatory performance and swallowing performance have remained unexplored.

OBJECTIVES

The study focuses on the age-specific association between masticatory/swallowing performance and oral/systemic/nutritional factors and their association with functional brain connectivity.

METHODS

One-hundred and eighteen healthy adults (48 older age, 27 middle-aged and 43 younger age) were recruited for food-mixing and repetitive saliva swallowing tests, respectively, indexed for masticatory and swallowing performance, as well as oral, systemic and nutritional factors, including mid-upper arm and calf circumferences. Structural and resting-state (rs) functional magnetic resonance imaging was acquired. Seed-based connectivity analyses were conducted to investigate the association between swallowing performance and rs-functional connectivity (rs-FC) of the sensorimotor network.

RESULTS

(a) In contrast to mastication, individual swallowing performance was not associated with oral or systemic factors. (b) In older adults, higher mid-upper arm and calf circumferences were associated with both higher masticatory and swallowing performance (a statistically significant interaction, p = 0.018). (c) In older adults, higher swallowing performance was associated with stronger rs-FC between the cerebellum and basal ganglia (p = 0.008, corrected for small volume), whilst higher masticatory performance was associated with stronger rs-FC between the cerebellum and primary sensorimotor cortices (p = 0.045, corrected for small volume).

CONCLUSION

Our findings reveal age-specific associations between swallowing, mastication, nutritional factors and brain functional connectivity. The findings highlight the association between the brain and individual differences in masticatory and swallowing performance.

Purkinje cells of the cerebellum control deceleration of tongue movements

We use our tongue much like our hands: to interact with objects and transport them. For example, we use our hands to sense properties of objects and transport them in the nearby space, and we use our tongue to sense properties of food morsels and transport them through the oral cavity. But what does the cerebellum contribute to control of tongue movements? Here, we trained head-fixed marmosets to make skillful tongue movements to harvest food from small tubes that were placed at sharp angles to their mouth. We identified the lingual regions of the cerebellar vermis and then measured the contribution of each Purkinje cell (P-cell) to control of the tongue by relying on the brief but complete suppression that they experienced following an input from the inferior olive. When a P-cell was suppressed during protraction, the tongue's trajectory became hypermetric, and when the suppression took place during retraction, the tongue's return to the mouth was slowed. Both effects were amplified when two P-cells were simultaneously suppressed. Moreover, these effects were present even when the pauses were not due to the climbing fiber input. Therefore, suppression of P-cells in the lingual vermis disrupted the forces that would normally decelerate the tongue as it approached the target. Notably, the population simple spike activity peaked near deceleration onset when the movement required precision (aiming for a tube), but not when the movement was for the purpose of grooming. Thus, the P-cells appeared to signal when to stop protrusion as the tongue approached its target.

Feasibility of Cerebellar Stimulation for the Treatment of Post-Stroke Dysphagia

Post-stroke dysphagia (PSD) is common and associated with poor outcomes. We aimed to explore the feasibility, safety, and proof of concept of cerebellar rTMS in patients with sub-acute PSD. We intended to recruit 48 participants with PSD. Randomised to: (i) sham treatment twice-daily for five days, (ii) cerebellar rTMS daily for three days, and (iii) cerebellar rTMS twice-daily for five days (1:1:1). Participants were blinded to treatment group. Primary outcomes were feasibility, safety, and functional outcome intake scale (FOIS), dysphagia severity rating scale (DSRS), and feeding status scale (FSS) at two weeks. However, due to lower-than-expected enrolment, the active rTMS groups were combined. We recruited 14 participants in total, (mean 68 years, 57% female). Due to the time-limited funding period, recruitment was adversely affected by the COVID-19 pandemic. DSRS and FSS trended lower in the combined active rTMS groups at two weeks, i.e. less swallowing impairment. However, at death/discharge FOIS was higher/better (mean, (standard deviation)), 4.0 (2.1) vs. 1.8 (1.0) (p = 0.032) with active TMS, with trends to lower/better DSRS and FSS. There was no difference in the acceptability of treatment between groups. High-intensity (n = 5) vs. low-intensity (n = 5) cerebellar rTMS was associated with lower DSRS 3.0 (1.4) vs. 9.4 (2.7) and FSS 0.6 (0.5) vs. 1.6 (0.5) at 2 weeks, and DSRS 3.0 (1.4) vs. 9.0 (3.7) at hospital discharge or death. Cerebellar rTMS is a feasible ward-based treatment for reducing swallowing impairment. Although enrolment was lower than desired, there was evidence for proof of concept, particularly for high-intensity cerebellar rTMS. Larger studies are warranted.

Control of tongue movements by the Purkinje cells of the cerebellum

We use our tongue much like our hands: to interact with objects and transport them. For example, we use our hands to sense properties of objects and transport them in the nearby space, and we use our tongue to sense properties of food morsels and transport them through the oral cavity. But what does the cerebellum contribute to control of tongue movements? Here, we trained head-fixed marmosets to make skillful tongue movements to harvest food from small tubes that were placed at sharp angles to their mouth. We identified the lingual regions of the cerebellar vermis and then measured the contribution of each Purkinje cell (P-cell) to control of the tongue by relying on the brief but complete suppression that they experienced following an input from the inferior olive. When a P-cell was suppressed during protraction, the tongue's trajectory became hypermetric, and when the suppression took place during retraction, the tongue's return to the mouth was slowed. Both effects were amplified when two P-cells were simultaneously suppressed. Therefore, suppression of P-cells in the lingual vermis disrupted the forces that would normally decelerate the tongue as it approached the target. Notably, the population simple spike activity peaked near deceleration onset when the movement required precision (aiming for a tube), but not when the movement was for the purpose of grooming. Thus, the P-cells appeared to signal when to stop protrusion as the tongue approached its target.

Determination of oral feeding skills in late preterm, early term, and full-term infants using the neonatal oral feeding monitor (NeoSAFE)

BACKGROUND

Mature oral feeding is a complex function involving numerous muscles and nerves, typically developing between the postmenstrual age of 34-36 weeks in newborn infants. The objective of this study was to analyze the oral feeding skills of healthy late preterm, early term, and full-term infants using a neonatal oral feeding monitor.

METHODS

We used the oral feeding parameters reported by NeoSAFE which is a certified medical device, to assess the swallowing and swallow-respiration coordination in newborn infants. Oral feeding parameters were recorded over a 2-minutes long bottle-feeding session. The total swallow count, swallow time, maximum rhythmic swallows, resting interval duration, time between rhythmic swallows and inspiration after swallow count were recorded by NeoSAFE. We planned to examine the relationship of oral feeding parameters according to the gestational age. We also investigated whether the coordination of swallowing and respiration changes with respect to gestational age in newborn infants.

RESULTS

A total of 88 infants were included; 34 late preterm, 34 early term, and 20 full term. The gestational age was found to have significant negative correlation with the average time between rhythmic swallows and positive correlation with the swallow time. Feeding volume was found to have a negative correlation with the resting interval duration and average time between rhythmic swallows. It was also found that the feeding volume has a positive correlation with total swallow count, swallow time, maximum rhythmic swallow and inspirium after swallow count.

CONCLUSION

Although the oral feeding skills of infants at 34 weeks gestation are still developing, this study identified differences in oral feeding skills among late preterm, early term, and full-term infants when assessed using a neonatal swallow and respiration detection system. However, conducting larger cohort studies using NeoSAFE would be beneficial for guiding oral feeding approaches in infants.

TRIAL REGISTRATION

Not applicable.

The neurorehabilitation of post-stroke dysphagia: Physiology and pathophysiology

Swallowing is a complex process involving the precise contractions of numerous muscles of the head and neck, which act to process and shepherd ingested material from the oral cavity to its eventual destination, the stomach. Over the past five decades, information from animal and human studies has laid bare the complex network of neurones in the brainstem, cortex and cerebellum that are responsible for orchestrating each normal swallow. Amidst this complexity, problems can and often do occur that result in dysphagia, defined as impaired or disordered swallowing. Dysphagia is common, arising from multiple varied disease processes that can affect any of the neuromuscular structures involved in swallowing. Post-stroke dysphagia (PSD) remains the most prevalent and most commonly studied form of dysphagia and, as such, provides an important disease model to assess dysphagia physiology and pathophysiology. In this review, we explore the complex neuroanatomical processes that occur during normal swallowing and PSD. This includes how strokes cause dysphagia, the mechanisms through which natural neuroplastic recovery occurs, current treatments for patients with persistent dysphagia and emerging neuromodulatory treatments.

Study on the predictive value of APACHE II score and neurogenic dysphagia in carbapenem-resistant Klebsiella pneumoniae

Carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a growing challenge in clinical treatment globally. Early identification of high-risk patients is essential to control infection spread and improve treatment outcomes. This retrospective study analyzed 152 patients with K pneumoniae infections at the Second People's Hospital of Hefei City, Anhui Province, dividing them into carbapenem-resistant and non-carbapenem-resistant groups. Clinical data, microbiological test results, Acute Physiology and Chronic Health Evaluation II (APACHE II) scores, and neurogenic dysphagia status were evaluated to identify risk factors for CRKP infection. The study revealed that patients in the carbapenem-resistant group had significantly higher APACHE II scores and a higher incidence of neurogenic dysphagia (P < 0.05). Multivariate logistic regression analysis identified APACHE II scores and neurogenic dysphagia as independent risk factors for CRKP infection. Receiver operating characteristic curve analysis showed an area under the curve of 0.824 (95% confidence interval: 0.749-0.898) for the APACHE II score, with an optimal threshold of 14.5 points. A new predictive model combining neurogenic dysphagia with APACHE II scores improved classification performance, as demonstrated by Net Reclassification Improvement (NRI = 0.0967, 95% confidence interval: -0.0477 to 0.2410) and reclassification probability analysis, correctly reclassifying 24.32% of individuals into a higher risk category. The findings highlight the combined predictive value of APACHE II scores and neurogenic dysphagia for early identification and intervention in high-risk CRKP patients.

Every bite counts to achieve oral health: a scoping review on diet and oral health preventive practices

OBJECTIVE

To examine the landscape of preventive strategies and interventions directed to achieve oral health equity, with particular emphasis on the interplay between dental caries prevention, individual behaviors, and population-level strategies across various demographic and geographic regions.

METHODS

This scoping review was guided by Peters et al.'s framework, which incorporates four key concepts aimed at reducing caries: education for individuals and healthcare providers, behavioral modifications, addressing broader social determinants of health, and extending oral health education programs beyond traditional dental settings. A systematic search was conducted across five databases, from 2011 to 2022.

RESULTS

This review identified 107 studies highlighting three main themes: behavioral practices (N = 33), which focused on reducing the prevalence of caries, improving oral hygiene practices, and enhancing overall oral health knowledge; educational interventions (N = 39), which explored strategies to integrate oral health with broader public health initiatives; and dietary interventions (N = 35), which emphasized the critical relationship between diet and oral health.

CONCLUSION

This SR highlights the critical need for comprehensive multilevel approaches that address the complex interplay between nutrition, oral health, and sociodemographic factors, while emphasizing the critical relationship between societal factors and individual health behaviors. Multifaceted interventions that include behavioral change, education, and dietary modifications are crucial for improving oral and overall health outcomes across diverse populations. Comprehensive strategies should prioritize medical-dental integration and data-driven approaches to effectively reduce oral health disparities for vulnerable populations, promoting long-term health equity.

Relationship Between DWI-Based Acute Ischemic Stroke Volume, Location and Severity of Dysphagia

BACKGROUND/OBJECTIVES

The impact of stroke location and volume on the development of post-stroke dysphagia is not fully understood. The aim of this study is to evaluate the relationship between acute ischemic lesions and the severity of dysphagia.

METHODS

Brain MRIs were obtained with a 1.5 Tesla MRI system (Magnetom Avanto B13, Siemens, Erlangen, Germany). The brain MRI protocol included axial echo planar diffusion-weighted imaging (DWI). The acute ischemic volume was obtained using DWI by drawing regions of interest (ROIs). The diagnosis and assessment of the severity of dysphagia was carried out by a multidisciplinary team and included the Dysphagia Outcome and Severity Scale (DOSS), the Penetration-Aspiration Scale (PAS), and the Pooling score (P-score). The threshold for statistical significance was set at 5%.

RESULTS

Among all the patients enrolled (n = 64), 28 (43.8%) were males and 36 (56.2%) were females, with a mean age of 78.8 years. Thirty-three (51.6%) of them had mild dysphagia and thirty-one (48.4%) had moderate-severe dysphagia. The total ischemic volume was negatively correlated with the DOSS (r = -0.441, p = 0.0003) and positively with the P-score (rs = 0.3054, p = 0.0328).

CONCLUSIONS

There are significant associations between the severity of dysphagia and the quantitative DWI-based data of the acute ischemic volume and anatomical location.

Revealing Goal-Directed Neural Control of the Pharyngeal Phase of Swallowing

Swallowing is considered a three-phase mechanism involving the oral, pharyngeal, and esophageal phases. The pharyngeal phase relies on highly coordinated movements in the pharynx and larynx to move food through the aerodigestive crossing. While the brainstem has been identified as the primary control center for the pharyngeal phase of swallowing, existing evidence suggests that the higher brain regions can contribute to controlling the pharyngeal phase of swallowing to match the motor response to the current context and task at hand. This suggests that the pharyngeal phase of swallowing cannot be exclusively reflexive or voluntary but can be regulated by the two neural controlling systems, goal-directed and non-goal-directed. This capability allows the pharyngeal phase of swallowing to adjust appropriately based on cognitive input, learned knowledge, and predictions. This paper reviews existing evidence and accordingly develops a novel perspective to explain these capabilities of the pharyngeal phase of swallowing. This paper aims (1) to integrate and comprehend the neurophysiological mechanisms involved in the pharyngeal phase of swallowing, (2) to explore the reflexive (non-goal-directed) and voluntary (goal-directed) neural systems of controlling the pharyngeal phase of swallowing, (3) to provide a clinical translation regarding the pathologies of these two systems, and (4) to highlight the existing gaps in this area that require attention in future research. This paper, in particular, aims to explore the complex neurophysiology of the pharyngeal phase of swallowing, as its breakdown can lead to serious consequences such as aspiration pneumonia or death.

The cerebellum modulates thirst

The cerebellum, a phylogenetically ancient brain region, has long been considered strictly a motor control structure. Recent studies have implicated the cerebellum in cognition, sensation, emotion and autonomic function, making it an important target for further investigation. Here, we show that cerebellar Purkinje neurons in mice are activated by the hormone asprosin, leading to enhanced thirst, and that optogenetic or chemogenetic activation of Purkinje neurons induces rapid manifestation of water drinking. Purkinje neuron-specific asprosin receptor (Ptprd) deletion results in reduced water intake without affecting food intake and abolishes asprosin's dipsogenic effect. Purkinje neuron-mediated motor learning and coordination were unaffected by these manipulations, indicating independent control of two divergent functions by Purkinje neurons. Our results show that the cerebellum is a thirst-modulating brain area and that asprosin-Ptprd signaling may be a potential therapeutic target for the management of thirst disorders.

Incidence and Risk Factors for Dysphagia Following Cerebellar Stroke: a Retrospective Cohort Study

The cerebellum is known to play a supportive role in swallowing-related functions; however, wide discrepancies about the incidence rate of swallowing disorders following cerebellar strokes exist within the literature. This study aimed to investigate the incidence rate of dysphagia and the factors which may affect the presence of dysphagia and clinical recovery in individuals diagnosed with cerebellar stroke. A retrospective chart audit of 1651 post-stroke patients (1049 males and 602 females) admitted with a cerebellar stroke to a comprehensive tertiary hospital in China was conducted. Data on demographics, medical, along with swallowing function assessment were collected. Differences between dysphagic and non-dysphagic groups were evaluated using t-tests and Pearson's chi-square test. Univariate logistic regression analysis was performed to establish factors associated with the presence of dysphagia. A total of 11.45% of participants were identified with dysphagia during inpatient admission. Individuals with mixed types of stroke, multiple lesions in the cerebellum, and ages older than 85 years old were more likely to develop dysphagia. Moreover, the prognosis of dysphagia following a cerebellar stroke was associated with lesions in different parts of the cerebellum. The cumulative recovery rates from the best to worse were the right hemisphere group, the cerebellum vermis or peduncle group, and both the hemisphere group and the left hemisphere group, respectively.

New and Evolving Treatments for Neurologic Dysphagia

Despite swallowing being a frequently performed daily function, it is highly complex. For a safe swallow to occur, muscles within the head, neck, and thorax need to contract in a concerted pattern, controlled by several swallowing centers at multiple levels of the central nervous system, including the midbrain, cerebral cortex, and cerebellum in addition to five cranial nerves. Dysphagia, or difficulty swallowing, is caused by a long list of pathologic processes and diseases, which can interfere with various stages along the swallowing sensorimotor pathway. When present, dysphagia leads to increased mortality, morbidity, hospital length of stay, and reduced quality of life. Current dysphagia management approaches, such as altering the texture and consistency of foods and fluids and teaching patients rehabilitative exercises, have been broadly unchanged for many years and, in the case of texture modification, are of uncertain effectiveness. However, evidence is emerging in support of new medication-based and neuromodulatory treatment approaches. Regarding medication-based therapies, most research has focused on capsaicinoids, which studies have shown are able to improve swallowing in patients with post-stroke dysphagia. Separately, albeit convergently, in the field of neuromodulation, there is a growing and positive evidential base behind three non-invasive brain stimulation techniques: repetitive transcranial magnetic stimulation (rTMS), transcranial direct current stimulation (TDCS), and pharyngeal electrical stimulation (PES). Should some or all of these emerging therapies fulfill their promise, dysphagia-related patient outcomes may be improved. This paper describes the current state of our understanding regarding new medication and neuromodulation-based neurogenic oropharyngeal dysphagia treatments.

Progressive Dysphagia in Joubert Syndrome: A Report of a Rare Case

Joubert syndrome is an uncommon, autosomal recessive disorder characterized by abnormal brain development involving the underdevelopment or absence of the cerebellar vermis. The classic clinical features include developmental delays, hypotonia, abnormal eye movements, and hyperpnea. On brain magnetic resonance imaging (MRI), an essential finding for the diagnosis of Joubert syndrome is a cerebellar and brainstem malformation called the molar tooth sign, characterized by a hypoplastic cerebellar vermis with dysplasia of the superior cerebellar peduncles. Here, we describe a case of a two-month-old female with an atypical presentation of Joubert syndrome. Her initial clinical presentation included respiratory distress and concerns for reflux complicated with aspiration pneumonia. Early recognition of clinical and radiologic findings for Joubert syndrome enables an early diagnosis, and therefore timely interventions for improving the child's development and quality of life.

Progressive Cerebrocerebellar Uncoupling in Sporadic and Genetic Forms of Amyotrophic Lateral Sclerosis

BACKGROUND AND OBJECTIVES

Amyotrophic lateral sclerosis (ALS) is predominantly associated with motor cortex, corticospinal tract (CST), brainstem, and spinal cord degeneration, and cerebellar involvement is much less well characterized. However, some of the cardinal clinical features of ALS, such as dysarthria, dysphagia, gait impairment, falls, and impaired dexterity, are believed to be exacerbated by coexisting cerebellar pathology. Cerebellar pathology may also contribute to cognitive, behavioral, and pseudobulbar manifestations. Our objective was to systematically assess both intracerebellar pathology and cerebrocerebellar connectivity alterations in a genetically stratified cohort of ALS.

METHODS

A prospective, multimodal neuroimaging study was conducted to evaluate the longitudinal evolution of intracerebellar pathology and cerebrocerebellar connectivity, using structural and functional measures.

RESULTS

A total of 113 healthy controls and 212 genetically stratified individuals with ALS were included: (1) C9orf72 hexanucleotide carriers ("C9POS"), (2) sporadic patients who tested negative for ALS-associated genetic variants, and (3) intermediate-length CAG trinucleotide carriers in ATXN2 ("ATXN2"). Flocculonodular lobule (padj = 0.014, 95% CI -5.06e-5 to -3.98e-6) and crura (padj = 0.031, 95% CI -1.63e-3 to -5.55e-5) volume reductions were detected at baseline in sporadic patients. Cerebellofrontal and cerebelloparietal structural connectivity impairment was observed in both C9POS and sporadic patients at baseline, and both projections deteriorated further over time in sporadic patients (padj = 0.003, t(249) = 3.04 and padj = 0.05, t(249) = 1.93). Functional cerebelloparietal uncoupling was evident in sporadic patients at baseline (padj = 0.004, 95% CI -0.19 to -0.03). ATXN2 patients exhibited decreased cerebello-occipital functional connectivity at baseline (padj = 0.004, 95% CI -0.63 to -0.06), progressive cerebellotemporal functional disconnection (padj = 0.025, t(199) = -2.26), and progressive flocculonodular lobule degeneration (padj = 0.017, t(249) = -2.24). C9POS patients showed progressive ventral dentate atrophy (padj = 0.007, t(249) = -2.75). The CSTs (padj < 0.001, 95% CI 4.89e-5 to 1.14e-4) and transcallosal interhemispheric fibers (padj < 0.001, 95% CI 5.21e-5 to 1.31e-4) were affected at baseline in C9POS and exhibited rapid degeneration over the 4 time points. The rate of decline in CST and corpus callosum integrity was faster than the rate of cerebrocerebellar disconnection (padj = 0.001, t(190) = 6.93).

DISCUSSION

ALS is associated with accruing intracerebellar disease burden as well as progressive corticocerebellar uncoupling. Contrary to previous suggestions, we have not detected evidence of compensatory structural or functional changes in response to supratentorial degeneration. The contribution of cerebellar disease burden to dysarthria, dysphagia, gait impairment, pseudobulbar affect, and cognitive deficits should be carefully considered in clinical assessments, monitoring, and multidisciplinary interventions.

Prevalence, recovery and phenotype of dysphagia in patients with ischaemic cerebellar stroke

BACKGROUND AND PURPOSE

Swallowing is a complex task, moderated by a sophisticated bilateral network including multiple supratentorial regions, the brainstem and the cerebellum. To date, conflicting data exist about whether focal lesions to the cerebellum are associated with dysphagia. Therefore, the aim of the study was to evaluate dysphagia prevalence, recovery and dysphagia pattern in patients with ischaemic cerebellar stroke.

METHODS

A retrospective analysis of patients consecutively admitted to an academic stroke centre with ischaemic stroke found only in the cerebellum was performed. The presence of dysphagia was the primary end-point and was assessed by a speech-language pathologist, according to defined criteria. Dysphagia pattern was evaluated by analysing the videos of the flexible endoscopic evaluation of swallowing. Brain imaging was used to identify lesion size and location associated with dysphagia.

RESULTS

Between January 2016 and December 2021, 102 patients (35.3% female) with a mean age of 52.8 ± 17.3 years were included. Thirteen (12.7%) patients presented with dysphagia. The most frequently observed flexible endoscopic evaluation of swallowing phenotype was premature spillage (n = 7; 58.3%), whilst significant residues or aspiration did not occur. One patient died (7.7%); the other patients showed improvement of dysphagia and one patient (7.7%) was discharged with dietary restrictions.

CONCLUSIONS

Although the involvement of the cerebellum in deglutition has become increasingly evident, isolated lesions to the cerebellum are less likely to cause clinically relevant and persisting dysphagia compared to other brain regions. The observed dysphagia pattern shows a lack of coordination and control, resulting in premature spillage or fragmented bolus transfer in some patients.

The impact of physical therapy on dysphagia in neurological diseases: a review

A neurogenic dysphagia is dysphagia caused by problems with the central and peripheral nervous systems, is particularly prevalent in conditions such as Parkinson's disease and stroke. It significantly impacts the quality of life for affected individuals and causes additional burdens, such as malnutrition, aspiration pneumonia, asphyxia, or even death from choking due to improper eating. Physical therapy offers a non-invasive treatment with high efficacy and low cost. Evidence supporting the use of physical therapy in dysphagia treatment is increasing, including techniques such as neuromuscular electrical stimulation, sensory stimulation, transcranial direct current stimulation, and repetitive transcranial magnetic stimulation. While initial studies have shown promising results, the effectiveness of specific treatment regimens still requires further validation. At present, there is a lack of scientific evidence to guide patient selection, develop appropriate treatment regimens, and accurately evaluate treatment outcomes. Therefore, the primary objectives of this review are to review the results of existing research, summarize the application of physical therapy in dysphagia management, we also discussed the mechanisms and treatments of physical therapy for neurogenic dysphagia.

Supra- and infra-tentorial degeneration patterns in primary lateral sclerosis: a multimodal longitudinal neuroradiology study

BACKGROUND

Primary lateral sclerosis (PLS) is traditionally solely associated with progressive upper motor neuron dysfunction manifesting in limb spasticity, gait impairment, bulbar symptoms and pseudobulbar affect. Recent studies have described frontotemporal dysfunction in some patients resulting in cognitive manifestations. Cerebellar pathology is much less well characterised despite sporadic reports of cerebellar disease.

METHODS

A multi-timepoint, longitudinal neuroimaging study was conducted to characterise the evolution of both intra-cerebellar disease burden and cerebro-cerebellar connectivity. The volumes of deep cerebellar nuclei, cerebellar cortical volumes, cerebro-cerebellar structural and functional connectivity were assessed longitudinally in a cohort of 43 individuals with PLS.

RESULTS

Cerebello-frontal, -temporal, -parietal, -occipital and cerebello-thalamic structural disconnection was detected at baseline based on radial diffusivity (RD) and cerebello-frontal decoupling was also evident based on fractional anisotropy (FA) alterations. Functional connectivity changes were also detected in cerebello-frontal, parietal and occipital projections. Volume reductions were identified in the vermis, anterior lobe, posterior lobe, and crura. Among the deep cerebellar nuclei, the dorsal dentate was atrophic. Longitudinal follow-up did not capture statistically significant progressive changes. Significant primary motor cortex atrophy and inter-hemispheric transcallosal degeneration were also captured.

CONCLUSIONS

PLS is not only associated with upper motor neuron dysfunction, but cerebellar cortical volume loss and deep cerebellar nuclear atrophy can also be readily detected. In addition to intra-cerebellar disease burden, cerebro-cerebellar connectivity alterations also take place. Our data add to the evolving evidence of widespread neurodegeneration in PLS beyond the primary motor regions. Cerebellar dysfunction in PLS is likely to exacerbate bulbar, gait and dexterity impairment and contribute to pseudobulbar affect.

Different Purkinje cell pathologies cause specific patterns of progressive gait ataxia in mice

Gait ataxia is one of the most common and impactful consequences of cerebellar dysfunction. Purkinje cells, the sole output neurons of the cerebellar cortex, are often involved in the underlying pathology, but their specific functions during locomotor control in health and disease remain obfuscated. We aimed to describe the effect of gradual adult-onset Purkinje cell degeneration on gaiting patterns in mice, and to determine whether two different mechanisms that both lead to Purkinje cell degeneration cause different patterns in the development of gait ataxia. Using the ErasmusLadder together with a newly developed limb detection algorithm and machine learning-based classification, we subjected mice to a challenging locomotor task with detailed analysis of single limb parameters, intralimb coordination and whole-body movement. We tested two Purkinje cell-specific mouse models, one involving stochastic cell death due to impaired DNA repair mechanisms (Pcp2-Ercc1-/-), the other carrying the mutation that causes spinocerebellar ataxia type 1 (Pcp2-ATXN1[82Q]). Both mouse models showed progressive gaiting deficits, but the sequence with which gaiting parameters deteriorated was different between mouse lines. Our longitudinal approach revealed that gradual loss of Purkinje cell function can lead to a complex pattern of loss of function over time, and that this pattern depends on the specifics of the pathological mechanisms involved. We hypothesize that this variability will also be present in disease progression in patients, and that our findings will facilitate the study of therapeutic interventions in mice, as subtle changes in locomotor abilities can be quantified by our methods.

Dysphagia following cerebellar stroke: analyzing the contribution of the cerebellum to swallowing function

Swallowing is essential for human health, and the cerebellum is crucial for motor movement regulation. Cerebellar strokes may cause dysphagia, but their exact effects remain unexplored in swallowing function. Therefore, the aim of this study was to analyze the precise clinical characteristics of the oral and pharyngeal phases of swallowing after cerebellar stroke and to critically discuss the cerebellum's contribution to swallowing. The study involved 34 participants with cerebellar strokes, gathered through convenience sampling. Neurologists diagnosed isolated strokes, and a speech and language pathologist examined swallowing ability using the Mann Assessment of Swallowing Ability. The study found that 52.9% of people experienced dysphagia after a cerebellar stroke. Dysphagia was significantly associated with a higher risk of aspiration. Age was also significantly correlated with dysphagia. No significant correlation was found between swallowing ability and sex. In conclusion, this study suggests isolated cerebellar stroke can adversely affect the motor and non-motor aspects of swallowing and cause severe dysphagia and aspiration risk. Thus, early diagnosis and timely management of dysphagia following a cerebellar stroke can help prevent serious consequences.

Swallowing capacity and gravity of the laryngotracheal aspiration risk in atypical cerebellar stroke: case report

This case report aimed to evaluate the swallowing capacity and the severity of the risk of laryngotracheal aspiration of a 52-year-old female patient with atypical and rare stroke, with major injury in the cerebellar pathway. In order to measure swallowing capacity and risk of aspiration a routine clinical assessment used in the speech therapy clinic was performed and two valid clinical tests were used: Massey Bedside Swallowing Screen (MBSS) and Gugging Swallowing Screen (GUSS). After evaluation with the clinical tests, it was observed that the patient had reduced swallowing capacity, performance characterized as pathological, 100% dysfunction in the water swallowing test (MBSS), presence of choking, coughing, change in vocal quality and anterior escape. In the assessment of risk of aspiration with the GUSS, the patient presented moderate dysphagia and risk of laryngotracheal aspiration.This case report demonstrated that moderate dysphagia is found in a stroke patient with lesions that affect the cerebellum. Standardized and validated clinical tests such as GUSS and MBSS should also be used to assess the risk of dysphagia after stroke at ambulatory care.

Cerebellar Prediction and Feeding Behaviour

Given the importance of the cerebellum in controlling movements, it might be expected that its main role in eating would be the control of motor elements such as chewing and swallowing. Whilst such functions are clearly important, there is more to eating than these actions, and more to the cerebellum than motor control. This review will present evidence that the cerebellum contributes to homeostatic, motor, rewarding and affective aspects of food consumption.Prediction and feedback underlie many elements of eating, as food consumption is influenced by expectation. For example, circadian clocks cause hunger in anticipation of a meal, and food consumption causes feedback signals which induce satiety. Similarly, the sight and smell of food generate an expectation of what that food will taste like, and its actual taste will generate an internal reward value which will be compared to that expectation. Cerebellar learning is widely thought to involve feed-forward predictions to compare expected outcomes to sensory feedback. We therefore propose that the overarching role of the cerebellum in eating is to respond to prediction errors arising across the homeostatic, motor, cognitive, and affective domains.

Graph network measures reveal distinct white matter abnormalities in motor and extra-motor brain regions of two UMN-predominant ALS subtypes

BACKGROUND

Routine clinical magnetic resonance imaging (MRI) shows bilateral corticospinal tract (CST) hyperintensity in some patients with upper motor neuron (UMN)-predominant ALS (ALS-CST+) but not in others (ALS-CST-). Although, similar in their UMN features, the ALS-CST+ patient group is significantly younger in age, has faster disease progression and shorter survival than the ALS-CST- patient group. Reasons for the differences are unclear.

METHOD

In order to evaluate more objective MRI measures of these ALS subgroups, we used diffusion tensor images (DTI) obtained using single shot echo planar imaging sequence from 1.5 T Siemens MRI Scanner. We performed an exploratory whole brain white matter (WM) network analysis using graph theory approach on 45 ALS patients (ALS-CST+) (n = 21), and (ALS-CST-) (n = 24) and neurological controls (n = 14).

RESULTS

Significant (p < 0.05) differences in nodal degree measure between ALS patients and controls were observed in motor and extra motor regions, supplementary motor area, subcortical WM regions, cerebellum and vermis. Importantly, WM network abnormalities were significantly (p < 0.05) different between ALS-CST+ and ALS-CST- subgroups. Compared to neurologic controls, both ALS subgroups showed hubs in the right superior occipital gyrus and cuneus as well as significantly (p < 0.05) reduced small worldness supportive of WM network damage.

CONCLUSIONS

Significant differences between ALS-CST+ and ALS-CST- subgroups of WM network abnormalities, age of onset, symptom duration prior to MRI, and progression rate suggest these patients represent distinct clinical phenotypes and possibly pathophysiologic mechanisms of ALS.

Evaluating the Therapeutic Application of Neuromodulation in the Human Swallowing System

In the last two decades, the focus of neurogenic dysphagia management has moved from passive compensatory strategies to evidence-based rehabilitative approaches. Advances in technology have enabled the development of novel treatment approaches such as neuromodulation techniques, which target the promotion of neurological reorganization for functional recovery of swallowing. Given the rapid pace of development in the field, this review aims to summarize the current findings on the effects of neuromodulation techniques on the human swallowing system and evaluate their therapeutic potential for neurogenic dysphagia. Implications for future clinical research and practical considerations for using neuromodulation in clinical practice will also be discussed.

Effect of cerebellar transcranial magnetic stimulation with double-cone coil on dysphagia after subacute infratentorial stroke: A randomized, single-blinded, controlled trial

BACKGROUND

A 10-Hz cerebellar repetitive transcranial magnetic stimulation (rTMS) could increase corticobulbar tract excitability in healthy individuals. However, its clinical efficacy for poststroke dysphagia (PSD) remains unclear.

OBJECTIVE

To investigate the effectiveness of 10-Hz cerebellar rTMS in PSD patients with infratentorial stroke (IS).

METHODS

In this single-blinded, randomized controlled trial, 42 PSD patients with subacute IS were allocated to three groups: bilateral cerebellar rTMS (biCRB-rTMS), unilateral cerebellar rTMS (uniCRB-rTMS), or sham-rTMS. The stimulation parameters were 5 trains of 50 stimuli at 10 Hz with an interval of 10 s at 90% of the thenar resting motor threshold (RMT). The Functional Oral Intake Scale (FOIS) was assessed at T0 (baseline), T1 (day 0 after intervention), and T2 (day 14 after intervention), whereas the Dysphagia Outcome and Severity Scale (DOSS), Penetration Aspiration Scale (PAS), and neurophysiological parameters were evaluated at T0 and T1.

RESULTS

Significant time and intervention interaction effects were observed for the FOIS score (F = 3.045, p = 0.022). The changes in the FOIS scores at T1 and T2 were both significantly higher in the biCRB-rTMS group than in the sham-rTMS group (p < 0.05). The uniCRB-rTMS and biCRB-rTMS groups demonstrated greater changes in the DOSS and PAS at T1, compared with the sham-rTMS group (p < 0.05). Bilateral corticobulbar tract excitability partly increased in the biCRB-rTMS and uniCRB-rTMS groups at T1, compared with T0. The percent changes in corticobulbar tract excitability parameters at T1 showed no difference among three groups.

CONCLUSIONS

A 10-Hz bilateral cerebellar rTMS is a promising, noninvasive treatment for subacute infratentorial PSD.

Use of the EXOPULSE Mollii for severe ataxia in an adult male 4 months after cardiac arrest

The EXOPULSE Mollii is designed to reduce spasticity through low-current electrical stimulation of major muscle groups. The effect on severe cerebellar ataxia has not been investigated. This case describes the use of the EXOPULSE Mollii in an adult male with severe cerebellar ataxia 4 months after cardiac arrest and ischaemic stroke. The patient used the suit in 15 of 19 possible sessions (78.9%). He improved in the sit-to-stand test, arm function test and 10 m walking test. He described improved visual focus, ability to speak and swallow. Improvements were maintained for 1 week after the last session. The EXOPULSE Mollii is relevant to consider in the early stages of inpatient rehabilitation for patients with severe ataxia, but further research is warranted.

Connecting the Pipes: Agricultural Tile Drains and Elevated Imidacloprid Brain Concentrations in Juvenile Northern Leopard Frogs (Rana pipiens)

Neonicotinoids are neurotoxic insecticides and are often released into nearby wetlands via subsurface tile drains and can negatively impact nontarget organisms, such as amphibians. Previous studies have indicated that imidacloprid, a commonly used neonicotinoid, can cross the amphibian blood-brain barrier under laboratory conditions; however, little is known about the impact of low concentrations in a field-based setting. Here, we report aqueous pesticide concentrations at wetland production areas that were either connected or not connected to agricultural tile drains, quantified imidacloprid and its break down products in juvenile amphibian brains and livers, and investigated the relationship between imidacloprid brain concentration and brain size. Imidacloprid concentrations in brain and water samples were nearly 2.5 and 5 times higher at tile wetlands (brain = 4.12 ± 1.92 pg/mg protein; water = 0.032 ± 0.045 μg/L) compared to reference wetlands, respectively. Tile wetland amphibians also had shorter cerebellums (0.013 ± 0.001 mm), depicting a negative relationship between imidacloprid brain concentration and cerebellum length. The metabolite, desnitro-imidacloprid, had liver concentrations that were 2 times higher at tile wetlands (2 ± 0.3 μg/g). Our results demonstrate that imidacloprid can cross the amphibian blood-brain barrier under ecological conditions and may alter brain dimensions and provide insight into the metabolism of imidacloprid in amphibians.

The therapeutic effect of capsaicin on oropharyngeal dysphagia: A systematic review and meta-analysis

Objectives

Capsaicin is a specific agonist of TRPV1 (multimodal sensory receptor), which improves oropharyngeal dysphagia by increasing sensory input from the oropharynx and hypopharynx and by increasing repetitive stimulation of the cerebral cortex. The aim of this systematic review was to evaluate the therapeutic effect of capsaicin on swallowing disorders in stroke patients and the elderly.

Method

We searched Medline, Embase, PubMed, and Cochrane Library databases. We used the Mesh terms search database to screen all clinical trials that complied with the inclusion criteria. Studies were subjected to literature screening, quality assessment, and data extraction to remove studies that did not meet the inclusion criteria. After literature screening, quality assessment, and data extraction, a systematic review and meta-analysis of the included study were performed.

Results

This systematic review and meta-analysis were prospectively registered on PROSPERO under registration number CRD42022313958. Five high-quality randomized controlled trials were ultimately included. The results of our meta-analysis showed a more significant reduction in swallowing function score change in the capsaicin group compared to the control group [SMD = -1.30, 95% CI: (-2.35, -0.25), P = 0.01] and on the Water swallowing test the improvement was significantly higher in the capsaicin group [RR = 2.46, 95% CI: (1.73, 3.50), P < 0.0001].

Conclusions

Although the results of our meta-analysis showed that capsaicin improved swallowing function, most studies had an unclear bias and included few studies. More studies are needed to support this in the future.

Systematic review registration

www.crd.york.ac.uk/prospero/display_record.php?RecordID=304061, identifier: 304061.

Neural Correlates of Oral Stereognosis—An fMRI Study

Oral stereognosis is the ability to recognize, discriminate and localize a bolus in the oral cavity. Clinical observation indicates deficits in oral stereognosis in patients with vascular or neurodegenerative diseases particularly affecting the parietal lobes. However, the precise neural representation of oral stereognosis remains unclear whereas the neural network of manual stereognosis has already been identified. We hypothesize that oral and manual stereognosis share common neuronal substrates whilst also showing somatotopic distribution. Functional magnetic resonance images (fMRI; Siemens Prisma 3 T) from 20 healthy right-handed participants (11 female; mean age 25.7 years) using a cross-modal task of oral and manual spatial object manipulation were acquired. Data were analyzed using FSL software using a block design and standard analytical and statistical procedures. A conjunction analysis targeted the common neuronal substrate for stereognosis. Activations associated with manual and oral stereognosis were found in partially overlapping fronto-parietal networks in a somatotopic fashion, where oral stereognosis is located caudally from manual stereognosis. A significant overlap was seen in the left anterior intraparietal sulcus. Additionally, cerebellar activations were shown particularly for the oral condition. Spatial arrangement of shaped boli in the oral cavity is associated with neuronal activity in fronto-parietal networks and the cerebellum. These findings have significant implications for clinical diagnostics and management of patients with lesions or atrophy in parietal lobule (e.g. Alzheimer’s disease, stroke). More studies are required to investigate the clinical effect of damage to these areas, such as loss of oral stereognosis or an impaired oral phase.

The Solitary Nucleus Connectivity to Key Autonomic Regions in Humans MRI and Literature based Considerations

The nucleus tractus solitarius (NTS), is a key brainstem structure relaying interoceptive peripheral information to the interrelated brain centers for eliciting rapid autonomic responses and for shaping longer-term neuroendocrine and motor patterns. Structural and functional NTS' connectivity has been extensively investigated in laboratory animals. But there is limited information about NTS' connectome in humans. Using MRI, we examined diffusion and resting state data from 20 healthy participants in the Human Connectome Project. The regions within the brainstem (n=8), subcortical (n=6), cerebellar (n=2) and cortical (n=5) parts of the brain were selected via a systematic review of the literature and their white matter NTS connections were evaluated via probabilistic tractography along with functional and directional (i.e., Granger-causality) analyses. The underlying study confirms previous results from animal models and provides novel aspects on NTS integration in humans. Two key findings can be summarized: (i) the NTS predominantly processes afferent input and (ii) a lateralization towards a predominantly left-sided NTS processing. Our results lay the foundations for future investigations into the NTS' tripartite role comprised of interoreceptors' input integration, the resultant neurochemical outflow and cognitive/affective processing. The implications of these data add to the understanding of NTS' role in specific aspects of autonomic functions.

Genotype-associated cerebellar profiles in ALS: focal cerebellar pathology and cerebro-cerebellar connectivity alterations

OBJECTIVE

Cerebellar disease burden and cerebro-cerebellar connectivity alterations are poorly characterised in amyotrophic lateral sclerosis (ALS) despite the likely contribution of cerebellar pathology to the clinical heterogeneity of the condition.

METHODS

A prospective imaging study has been undertaken with 271 participants to systematically evaluate cerebellar grey and white matter alterations, cerebellar peduncle integrity and cerebro-cerebellar connectivity in ALS. Participants were stratified into four groups: (1) patients testing positive for GGGGCC repeat expansions in C9orf72, (2) patients carrying an intermediate-length repeat expansion in ATXN2, (3) patients without established ALS-associated mutations and (4) healthy controls. Additionally, the cerebellar profile of a single patient with ALS who had an ATXN2 allele length of 62 was evaluated. Cortical thickness, grey matter and white matter volumes were calculated in each cerebellar lobule complemented by morphometric analyses to characterise genotype-associated atrophy patterns. A Bayesian segmentation algorithm was used for superior cerebellar peduncle volumetry. White matter diffusivity parameters were appraised both within the cerebellum and in the cerebellar peduncles. Cerebro-cerebellar connectivity was assessed using deterministic tractography.

RESULTS

Cerebellar pathology was confined to lobules I-V of the anterior lobe in patients with sporadic ALS in contrast to the considerable posterior lobe and vermis disease burden identified in C9orf72 mutation carriers. Patients with intermediate ATXN2 expansions did not exhibit significant cerebellar pathology.

CONCLUSIONS

Focal rather than global cerebellar degeneration characterises ALS. Pathognomonic ALS symptoms which are typically attributed to other anatomical regions, such as dysarthria, dysphagia, pseudobulbar affect, eye movement abnormalities and cognitive deficits, may be modulated, exacerbated or partially driven by cerebellar changes in ALS.