Central cholinergic dysfunction could be associated with oropharyngeal dysphagia in early Parkinson's disease

Short-latency afferent inhibition and its relationship to covert sensory and motor hand impairment in multiple sclerosis

OBJECTIVE

To investigate sensorimotor integration by quantifying short-latency afferent inhibition (SAI) in people with MS who experience manual dexterity problems compared to controls.

METHODS

22 people with MS with self-reported manual dexterity problems and 10 sex and age-matched controls were assessed using various upper extremity clinical tests. SAI was assessed by a transcranial magnetic stimulation pulse over the primary motor cortex preceded by peripheral nerve stimulation to the median nerve at 6 interstimulus intervals 2 - 8 ms longer than individualized N20 latencies.

RESULTS

Although within normal limits, persons with MS exhibited significantly slower Nine Hole Peg Test performance and pinch strength in the dominant hand. They also exhibited greater sensory impairment (monofilament test) in the dominant hand. Persons with MS showed significantly greater disinhibition of SAI in the dominant hand compared to controls, which was significantly correlated with weaker pinch strength.

CONCLUSION

Reduced SAI in people with MS, particularly in the dominant hand, signifies disruptions in cortical cholinergic inhibitory activity and is associated with lower pinch strength.

SIGNIFICANCE

Evaluating changes in SAI may offer insight into the disrupted cortical cholinergic inhibitory activity that contributes to sensorimotor disintegration, potentially advancing disease management in persons with MS.

Transcranial magnetic stimulation neurophysiology in patients with non-Alzheimer's neurodegenerative diseases: A systematic review and meta-analysis

Non-Alzheimer's dementia (NAD) accounts for 30% of all neurodegenerative conditions and is characterized by cognitive decline beyond mere memory dysfunction. Diagnosing NAD remains challenging due to the lack of established biomarkers. Transcranial magnetic stimulation (TMS) is a non-invasive neurophysiological tool that enables the investigation of cortical excitability in the human brain. Paired-pulse TMS paradigms include short- and long-interval intracortical inhibition (SICI/LICI), intracortical facilitation (ICF), and short-latency afferent inhibition (SAI), which can assess neurophysiological functions of GABAergic, glutamatergic, and cholinergic neural circuits, respectively. We conducted the first systematic review and meta-analysis to compare these TMS indices among patients with NAD and healthy controls. Our meta-analyses indicated that TMS neurophysiological examinations revealed decreased glutamatergic function in patients with frontotemporal dementia (FTD) and decreased GABAergic function in patients with FTD, progressive supranuclear palsy, Huntington's disease, cortico-basal syndrome, and multiple system atrophy-parkinsonian type. In addition, decreased cholinergic function was found in dementia with Lewy body and vascular dementia. These results suggest the potential of TMS as an additional diagnostic tool to differentiate NAD.

Reduced Short-Latency Afferent Inhibition in Parkinson's Disease Patients with L-dopa-Unresponsive Freezing of Gait

BACKGROUND

Freezing of gait (FOG) in Parkinson's disease (PD), especially the "L-dopa-unresponsive" subtype, is associated with the dysfunction of non-dopaminergic circuits.

OBJECTIVE

We sought to determine whether cortical sensorimotor inhibition evaluated by short-latency afferent inhibition (SAI) related to cholinergic and gamma-aminobutyric acid (GABA)-ergic activities is impaired in PD patients with L-dopa-unresponsive FOG (ONOFF-FOG).

METHODS

SAI protocol was performed in 28 PD patients with ONOFF-FOG, 15 PD patients with "off" FOG (OFF-FOG), and 25 PD patients without FOG during medication "on" state. Additionally, 10 ONOFF-FOG patients underwent SAI testing during both "off" and "on" states. Twenty healthy controls participated in this study. Gait was measured objectively using a portable Inertial Measurement Unit system, and participants performed 5-meter Timed Up and Go single- and dual-task conditions. Spatiotemporal gait characteristics and their variability were determined. FOG manifestations and cognition were assessed with clinical scales.

RESULTS

Compared to controls, PD patients without FOG and with OFF-FOG, ONOFF-FOG PD patients showed significantly reduced SAI. Further, dopaminergic therapy had no remarkable effect on this SAI alterations in ONOFF-FOG. Meanwhile, OFF-FOG patients presented decreased SAI only relative to controls. PD patients with ONOFF-FOG exhibited decreased gait speed, stride length, and increased gait variability relative to PD patients without FOG and controls under both walking conditions. For ONOFF-FOG patients, significant associations were found between SAI and FOG severity, gait characteristics and variability.

CONCLUSION

Reduced SAI was associated with severe FOG manifestations, impaired gait characteristics and variability in PD patients with ONOFF-FOG, suggesting the impaired thalamocortical cholinergic-GABAergic SAI pathways underlying ONOFF-FOG.

Cardiac sympathetic denervation could be associated with dysphagia in Parkinson's disease

Background

Dysphagia is an important non-motor symptom that is closely associated with quality of living and mortality in Parkinson's disease (PD). However, the pathophysiology of dysphagia in PD remains inconclusive. We tried to confirm whether the occurrence of dysphagia could be related to sympathetic degeneration using cardiac 123I-metaiodobenzylguanidine (MIBG) scintigraphy.

Methods

We prospectively recruited 27 PD patients and classified them into two groups (PD with dysphagia vs. PD without dysphagia) by Swallowing Disturbance Questionnaire (SDQ) score and compared the clinical characteristics, videofluoroscopic swallowing study (VFSS) findings and parameters from cardiac MIBG scintigraphy.

Results

The mean early and late H/M ratios were significantly lower in the PD with dysphagia group than those in the PD without dysphagia group (1.39 ± 0.21 vs. 1.86 ± 0.21, p < 0.01; 1.26 ± 0.18 vs. 1.82 ± 0.29, p < 0.01). In the correlation analysis, both the early and late H/M ratios were negatively correlated with the SDQ score and total VDS score (r = −0.65, p < 0.01; r = −0.53, p < 0.01; r = −0.65, p < 0.01, r = −0.58, p < 0.01).

Conclusion

We confirmed that cardiac sympathetic denervation might be associated with the presence and severity of dysphagia. This finding indicates that dysphagia in PD could be associated with a nondopaminergic mechanism.

The prevalence and associated factors of dysphagia in Parkinson's disease: A systematic review and meta-analysis

Background

The prevalence and associated factors of dysphagia in Parkinson's disease (PD) are different in studies conducted in different countries. The purpose of our systematic review and meta-analysis was to evaluate the prevalence of dysphagia in PD and to clarify its associated factors.

Methods

Two researchers systematically searched PubMed, Embase, Web of Science, Cochrane Library, CNKI, Wanfang Database, SinoMed and VIP databases and manually searched references in the retrieved articles to identify potential research subjects. The last search was conducted on June 28, 2022. Finally, a total of 58 studies including 60 observations with 20,530 PD patients were included in our meta-analysis.

Results

The meta-analysis estimated that the pooled prevalence rate of dysphagia in PD was 36.9% (95% CI: 30.7–43.6%) and instrumental examination showed a higher prevalence (57.3%, 95% CI: 44.3–69.1%). Oceania showed the highest prevalence of dysphagia in PD (56.3%) compared to Africa (39.5%), Asia (38.6%), Europe (36.1%) and America (28.9%). Dysphagia in PD was associated with older age, lower body mass index, longer disease duration, higher Hoehn and Yahr stage and levodopa equivalent daily dose, PIGD subtype, severe motor symptoms, drooling and higher levels of depression, and lower quality of life.

Conclusions

In conclusion, our meta-analysis showed that dysphagia occurs in more than one-third of PD patients and was associated with several demographic characteristics and PD-related characteristics, motor symptoms, non-motor symptoms, as well as decreased quality of life. It deserves early screening, diagnosis, and treatment in clinical practice to prevent serious complications from dysphagia.

Anodal Transcranial Direct Current Stimulation Could Modulate Cortical Excitability and the Central Cholinergic System in Akinetic Rigid-Type Parkinson's Disease: Pilot Study

Background

Transcranial direct current stimulation (tDCS) is a non-invasive technique that has been widely studied as an alternative treatment for Parkinson's disease (PD). However, its clinical benefit remains unclear. In this study, we aimed to investigate the effect of tDCS on the central cholinergic system and cortical excitability in mainly akinetic rigid-type patients with PD.

Methods

In total, 18 patients with PD were prospectively enrolled and underwent 5 sessions of anodal tDCS on the M1 area, which is on the contralateral side of the dominant hand. We excluded patients with PD who had evident resting tremor of the hand to reduce the artifact of electrophysiologic findings. We compared clinical scales reflecting motor, cognitive, and mood symptoms between pre- and post-tDCS. Additionally, we investigated the changes in electrophysiologic parameters, such as short latency afferent inhibition (SAI) (%), which reflects the central cholinergic system.

Results

The United Parkinson's Disease Rating Scale Part 3 (UPDRS-III), the Korean-Montreal Cognitive Assessment (MoCA-K), and Beck Depression Inventory (BDI) scores were significantly improved after anodal tDCS (p < 0.01, p < 0.01, and p < 0.01). Moreover, motor evoked potential amplitude ratio (MEPAR) (%) and integrated SAI showed significant improvement after tDCS (p < 0.01 and p < 0.01). The mean values of the change in integrated SAI (%) were significantly correlated with the changes in UPDRS-III scores; however, the MoCA-K and BDI scores did not show differences.

Conclusions

Anodal tDCS could influence the central cholinergic system, such as frontal cortical excitability and depression in PD. This mechanism could underlie the clinical benefit of tDCS in patients with PD.

Gastrointestinal Dysfunction in Parkinson’s Disease: Current and Potential Therapeutics

Abnormalities in the gastrointestinal (GI) tract of Parkinson’s disease (PD) sufferers were first reported over 200 years ago; however, the extent and role of GI dysfunction in PD disease progression is still unknown. GI dysfunctions, including dysphagia, gastroparesis, and constipation, are amongst the most prevalent non-motor symptoms in PD. These symptoms not only impact patient quality of life, but also complicate disease management. Conventional treatment pathways for GI dysfunctions (i.e., constipation), such as increasing fibre and fluid intake, and the use of over-the-counter laxatives, are generally ineffective in PD patients, and approved compounds such as guanylate cyclase C agonists and selective 5-hyroxytryptamine 4 receptor agonists have demonstrated limited efficacy. Thus, identification of potential targets for novel therapies to alleviate PD-induced GI dysfunctions are essential to improve clinical outcomes and quality of life in people with PD. Unlike the central nervous system (CNS), where PD pathology and the mechanisms involved in CNS damage are relatively well characterised, the effect of PD at the cellular and tissue level in the enteric nervous system (ENS) remains unclear, making it difficult to alleviate or reverse GI symptoms. However, the resurgence of interest in understanding how the GI tract is involved in various disease states, such as PD, has resulted in the identification of novel therapeutic avenues. This review focuses on common PD-related GI symptoms, and summarizes the current treatments available and their limitations. We propose that by targeting the intestinal barrier, ENS, and/or the gut microbiome, may prove successful in alleviating PD-related GI symptoms, and discuss emerging therapies and potential drugs that could be repurposed to target these areas.

Diagnostic contribution and therapeutic perspectives of transcranial magnetic stimulation in dementia

Transcranial magnetic stimulation (TMS) is a powerful tool to probe in vivo brain circuits, as it allows to assess several cortical properties such asexcitability, plasticity and connectivity in humans. In the last 20 years, TMS has been applied to patients with dementia, enabling the identification of potential markers of thepathophysiology and predictors of cognitive decline; moreover, applied repetitively, TMS holds promise as a potential therapeutic intervention. The objective of this paper is to present a comprehensive review of studies that have employed TMS in dementia and to discuss potential clinical applications, from the diagnosis to the treatment. To provide a technical and theoretical framework, we first present an overview of the basic physiological mechanisms of the application of TMS to assess cortical excitability, excitation and inhibition balance, mechanisms of plasticity and cortico-cortical connectivity in the human brain. We then review the insights gained by TMS techniques into the pathophysiology and predictors of progression and response to treatment in dementias, including Alzheimer's disease (AD)-related dementias and secondary dementias. We show that while a single TMS measure offers low specificity, the use of a panel of measures and/or neurophysiological index can support the clinical diagnosis and predict progression. In the last part of the article, we discuss the therapeutic uses of TMS. So far, only repetitive TMS (rTMS) over the left dorsolateral prefrontal cortex and multisite rTMS associated with cognitive training have been shown to be, respectively, possibly (Level C of evidence) and probably (Level B of evidence) effective to improve cognition, apathy, memory, and language in AD patients, especially at a mild/early stage of the disease. The clinical use of this type of treatment warrants the combination of brain imaging techniques and/or electrophysiological tools to elucidate neurobiological effects of neurostimulation and to optimally tailor rTMS treatment protocols in individual patients or specific patient subgroups with dementia or mild cognitive impairment.

A multinational consensus on dysphagia in Parkinson's disease: screening, diagnosis and prognostic value

Background

Parkinson’s disease (PD) is a neurodegenerative disorder characterized by a combination of motor and non-motor dysfunction. Dysphagia is a common symptom in PD, though it is still too frequently underdiagnosed. Consensus is lacking on screening, diagnosis, and prognosis of dysphagia in PD.

Objective

To systematically review the literature and to define consensus statements on the screening and the diagnosis of dysphagia in PD, as well as on the impact of dysphagia on the prognosis and quality of life (QoL) of PD patients.

Methods

A multinational group of experts in the field of neurogenic dysphagia and/or PD conducted a systematic revision of the literature published since January 1990 to February 2021 and reported the results according to PRISMA guidelines. The output of the research was then analyzed and discussed in a consensus conference convened in Pavia, Italy, where the consensus statements were drafted. The final version of statements was subsequently achieved by e-mail consensus.

Results

Eighty-five papers were used to inform the Panel’s statements even though most of them were of Class IV quality. The statements tackled four main areas: (1) screening of dysphagia: timing and tools; (2) diagnosis of dysphagia: clinical and instrumental detection, severity assessment; (3) dysphagia and QoL: impact and assessment; (4) prognostic value of dysphagia; impact on the outcome and role of associated conditions.

Conclusions

The statements elaborated by the Consensus Panel provide a framework to guide the neurologist in the timely detection and accurate diagnosis of dysphagia in PD.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-021-10739-8.

Impact of Progression of Parkinson's Disease on Swallowing Ability and Oral Environment

This study investigated the impact of the severity and treatment of Parkinson's disease (PD) on the swallowing ability and oral environment of patients. Swallowing dysfunction increases the aspiration risk and may lead to poor oral health among patients with PD. We investigated the influences of PD progression and drug treatment on the swallowing ability and oral environment using simple noninvasive screening measurements. We recruited 87 patients with PD (mean age, 71.9 ± 8.0 years; mean Hoehn and Yahr score, 2.9 ± 0.9). The PD condition was assessed in each patient using the unified Parkinson's disease rating scale (UPDRS) part III, diet type and oropharyngeal function using the swallowing disturbances questionnaire (SDQ), maximum bite force (MBF), tongue pressure (TP), and oral bacterial count (OBC). Levodopa equivalent daily dose (LEDD) was also calculated for 56 participants. Based on an SDQ score of ≥11, 29.5% of patients were dysphagic, but almost all were still on a regular diet. The SDQ score was positively correlated with disease duration (rho = 0.228, p=0.047) and UPDRS part III score (rho = 0.307, p=0.007) but was negatively correlated with OBC (rho = -0.289, p=0.012). OBC was significantly higher among patients with an SDQ score of <11 (nondysphagic) (p=0.01), and the SDQ score was lower in patients with higher OBC requiring professional oral care (p=0.03). However, OBC was also negatively correlated with LEDD (rho = -0.411, p=0.004). These results indicated low self-awareness of dysphagia among the participants and an association between dysphagia and PD progression. Moreover, the oral environment could have deteriorated with swallowing dysfunction. Patients and clinicians should be aware that higher LEDD can increase xerostomia and associated deficits in oral health.

Association of short- and long-latency afferent inhibition with human behavior

Transcranial magnetic stimulation (TMS) paired with nerve stimulation evokes short-latency afferent inhibition (SAI) and long-latency afferent inhibition (LAI), which are non-invasive assessments of the excitability of the sensorimotor system. SAI and LAI are abnormally reduced in various special populations in comparison to healthy controls. However, the relationship between afferent inhibition and human behavior remains unclear. The purpose of this review is to survey the current literature and synthesize observations and patterns that affect the interpretation of SAI and LAI in the context of human behavior. We discuss human behaviour across the motor and cognitive domains, and in special and control populations. Further, we discuss future considerations for research in this field and the potential for clinical applications. By understanding how human behavior is mediated by changes in SAI and LAI, this can allow us to better understand the neurophysiological underpinnings of human motor control.

A new swallowing supplement for dysphagia in patients with Parkinson's disease

Dysphagia associated with Parkinson's disease (PD) affects the mortality and quality of life of patients with PD. Avoiding aspiration and maintaining swallowing ability are among the concerns regarding PD care. Therefore, we developed a swallowing supplement for easier swallowing and tolerability in patients with PD. Thirty patients with PD and 50 healthy controls were enrolled and their swallowing function measured using the videofluoroscopic swallowing study (VFSS) and several dysphagia scales. The Unified Parkinson's Disease Rating Scale motor scores, Hoehn and Yahr stage, and levodopa doses were evaluated in patients with PD. The VFSS and survey were used to assess the viscosity, color, taste, nutrition, safety, and tolerability of the swallowing supplement. The MMSE score, serum albumin, and hemoglobin levels, and oral conditions were worse in the PD group than in the control group. Compared with controls, patients with PD had significantly lower total and sub-item scores of the swallowing quality of life (swal-QoL). Using commercialized yogurt, the pharyngeal delay time (PDT) and the modified penetration aspiration scale were higher in the PD group than in the control group. The swallowing supplement significantly shortened the PDT and pharyngeal transit time (PTT). Moreover, compared with commercialized yogurt, it improved pharyngeal wall coating, PTT, and aspiration in the videofluoroscopic dysphagia subscales. The survey scores were above average to good in the "easy swallowing" and "pharyngeal residual sense" items and tolerable in the remaining 6 preference items. This swallowing supplement could prevent aspiration and dysphagia complications in patients with PD.

A Review on Tramiprosate (Homotaurine) in Alzheimer's Disease and Other Neurocognitive Disorders

Alzheimer's disease (AD) is the most prevalent neurodegenerative condition, especially among elderly people. The presence of cortical β-amyloid deposition, together with tau phosphorylation and intracellular accumulation of neurofibrillary tangles (NFT) is the main neuropathologic criteria for AD diagnosis. Additionally, a role of inflammatory, mitochondrial, and metabolic factors has been suggested. Tramiprosate binds to soluble amyloid, thus inhibiting its aggregation in the brain. It reduced oligomeric and fibrillar (plaque) amyloid, diminished hippocampal atrophy, improved cholinergic transmission, and stabilized cognition in preclinical and clinical studies. In this narrative review, current information on the efficacy and safety of tramiprosate, both in AD and in other neurocognitive disorders, is presented. Possible directions for future studies with tramiprosate are also discussed.

Evolving concepts on bradykinesia

Bradykinesia is one of the cardinal motor symptoms of Parkinson's disease and other parkinsonisms. The various clinical aspects related to bradykinesia and the pathophysiological mechanisms underlying bradykinesia are, however, still unclear. In this article, we review clinical and experimental studies on bradykinesia performed in patients with Parkinson's disease and atypical parkinsonism. We also review studies on animal experiments dealing with pathophysiological aspects of the parkinsonian state. In Parkinson's disease, bradykinesia is characterized by slowness, the reduced amplitude of movement, and sequence effect. These features are also present in atypical parkinsonisms, but the sequence effect is not common. Levodopa therapy improves bradykinesia, but treatment variably affects the bradykinesia features and does not significantly modify the sequence effect. Findings from animal and patients demonstrate the role of the basal ganglia and other interconnected structures, such as the primary motor cortex and cerebellum, as well as the contribution of abnormal sensorimotor processing. Bradykinesia should be interpreted as arising from network dysfunction. A better understanding of bradykinesia pathophysiology will serve as the new starting point for clinical and experimental purposes.

Autonomic dysfunction in Parkinson's disease: Implications for pathophysiology, diagnosis, and treatment

Parkinson's disease (PD) is a neurodegenerative disease with a 200 year-long research history. Our understanding about its clinical phenotype and pathogenesis remains limited, although dopaminergic replacement therapy has significantly improved patient outcomes. Autonomic dysfunction is an essential category of non-motor phenotypes that has recently become a cutting edge field that directs frontier research in PD. In this review, we initially describe the epidemiology of dysautonomic symptoms in PD. Then, we perform a meticulous analysis of the pathophysiology of autonomic dysfunction in PD and propose that the peripheral autonomic nervous system may be a key route for α-synuclein pathology propagation from the periphery to the central nervous system. In addition, we recommend that constipation, orthostatic hypotension, urinary dysfunction, erectile dysfunction, and pure autonomic failure should be viewed as prodromal dysautonomic markers in PD prediction and diagnosis. Finally, we summarize the strategies currently available for the treatment of autonomic dysfunction in PD and suggest that high-quality, better-designed, randomized clinical trials should be conducted in the future.

Fast Intracortical Sensory-Motor Integration: A Window Into the Pathophysiology of Parkinson's Disease

Parkinson's Disease (PD) is a prototypical basal ganglia disorder. Nigrostriatal dopaminergic denervation leads to progressive dysfunction of the cortico-basal ganglia-thalamo-cortical sensorimotor loops, causing the classical motor symptoms. Although the basal ganglia do not receive direct sensory input, they are important for sensorimotor integration. Therefore, the basal ganglia dysfunction in PD may profoundly affect sensory-motor interaction in the cortex. Cortical sensorimotor integration can be probed with transcranial magnetic stimulation (TMS) using a well-established conditioning-test paradigm, called short-latency afferent inhibition (SAI). SAI probes the fast-inhibitory effect of a conditioning peripheral electrical stimulus on the motor response evoked by a TMS test pulse given to the contralateral primary motor cortex (M1). Since SAI occurs at latencies that match the peaks of early cortical somatosensory potentials, the cortical circuitry generating SAI may play an important role in rapid online adjustments of cortical motor output to changes in somatosensory inputs. Here we review the existing studies that have used SAI to examine how PD affects fast cortical sensory-motor integration. Studies of SAI in PD have yielded variable results, showing reduced, normal or even enhanced levels of SAI. This variability may be attributed to the fact that the strength of SAI is influenced by several factors, such as differences in dopaminergic treatment or the clinical phenotype of PD. Inter-individual differences in the expression of SAI has been shown to scale with individual motor impairment as revealed by UPDRS motor score and thus, may reflect the magnitude of dopaminergic neurodegeneration. The magnitude of SAI has also been linked to cognitive dysfunction, and it has been suggested that SAI also reflects cholinergic denervation at the cortical level. Together, the results indicate that SAI is a useful marker of disease-related alterations in fast cortical sensory-motor integration driven by subcortical changes in the dopaminergic and cholinergic system. Since a multitude of neurobiological factors contribute to the magnitude of inhibition, any mechanistic interpretation of SAI changes in PD needs to consider the group characteristics in terms of phenotypical spectrum, disease stage, and medication.

Constipation, deficit in colon contractions and alpha-synuclein inclusions within the colon precede motor abnormalities and neurodegeneration in the central nervous system in a mouse model of alpha-synucleinopathy

Background

Gastrointestinal dysfunction can affect Parkinson’s disease (PD) patients long before the onset of motor symptoms. However, little is known about the relationship between gastrointestinal abnormalities and the development of PD. Contrary to other animal models, the human A53T alpha-synuclein (αS) transgenic mice, Line G2–3, develops αS-driven neurological and motor impairments after 9 months of age, displaying a long presymptomatic phase free of central nervous system (CNS) dysfunction.

Methods

To determine whether this line can be suitable to study constipation as it occurs in prodromal PD, gastrointestinal functionality was assessed in young mice through a multidisciplinary approach, based on behavioral and biochemical analysis combined with electrophysiological recordings of mouse intestinal preparations.

Results

We found that the A53T αS mice display remarkable signs of gastrointestinal dysfunction that precede motor abnormalities and αS pathology in the CNS by at least 6 months. Young αS mice show a drastic delay in food transit along the gastrointestinal tract, of almost 2 h in 3 months old mice that increased to more than 3 h at 6 months. Such impairment was associated with abnormal formation of stools that resulted in less abundant but longer pellets excreted, suggesting a deficit in the intestinal peristalsis. In agreement with this, electrically evoked contractions of the colon, but not of the ileum, showed a reduced motor response in both longitudinal and circular muscle layers in αS mice already at 3 months of age, that was mainly due to an impaired cholinergic transmission of the underlying enteric nervous system. Interestingly, the presence of insoluble and aggregated αS was found in enteric neurons in both myenteric and submucosal plexi only in the colon of 3 months old αS mice, but not in the small intestine, and exacerbated with age, mimicking the increase in transit delay and the contraction deficit showed by behavioral and electrical recordings data.

Conclusions

Gastrointestinal dysfunction in A53T αS mice represents an early sign of αS-driven pathology without concomitant CNS involvement. We believe that this model can be very useful to study disease-modifying strategies that could extend the prodromal phase of PD and halt αS pathology from reaching the brain.

Electronic supplementary material

The online version of this article (10.1186/s40035-019-0146-z) contains supplementary material, which is available to authorized users.

Lingual Pressure as a Clinical Indicator of Swallowing Function in Parkinson's Disease

PURPOSE

Swallowing impairment, or dysphagia, is a known contributor to reduced quality of life, pneumonia, and mortality in Parkinson's disease (PD). However, the contribution of tongue dysfunction, specifically inadequate pressure generation, to dysphagia in PD remains unclear. Our purpose was to determine whether lingual pressures in PD are (a) reduced, (b) reflect medication state, or are (c) consistent with self-reported diet and swallowing function.

METHOD

Twenty-eight persons with idiopathic PD (PwPD) and 28 age- and sex-matched controls completed lingual pressure tasks with the Iowa Oral Performance Instrument. PwPD were tested during practically defined ON and OFF dopaminergic medication states. Participants were also stratified into three sex- and age-matched cohorts (7 men, 5 women): (a) controls, (b) PwPD without self-reported dysphagia symptoms or diet restrictions, and (c) PwPD with self-reported dysphagia symptoms with or without diet restrictions.

RESULTS

PwPD exhibited reduced tongue strength and used elevated proportions of tongue strength during swallowing compared with controls (p < .05) without an effect of medication state (p > .05). Reduced tongue strength distinguished PwPD with self-reported dysphagia symptoms from PwPD without reported symptoms or diet restrictions (p = .045) and controls (p = .002).

CONCLUSION

Tongue strength was significantly reduced in PwPD and did not differ by medication state. Tongue strength differentiated between PwPD with and without self-reported swallowing symptoms. Therefore, measures of tongue strength and swallowing pressures may serve as clinical indicators for further dysphagia evaluation and may promote early diagnosis and management of dysphagia in PD.

Olfactory dysfunction in early Parkinson's disease is associated with short latency afferent inhibition reflecting central cholinergic dysfunction

OBJECTIVE

Our study aimed to determine whether the short latency afferent inhibition (SAI) response could be associated with the severity of olfactory dysfunction in PD patients.

METHODS

A total of 71 PD patients and 20 controls were enrolled. All PD patients were classified into 3 groups by the severity of the olfactory deficit. Single-pulse transmagnetic stimulation (TMS) parameters and SAI were assessed.

RESULTS

The integrated SAI in the PD with anosmia and PD with hyposomia groups was significantly less inhibited than that in the PD with normosmia and control groups [64.79 {Interquartile range (IQR): 59.96, 71.33}, 84.79 {IQR: 75.03, 90.63} versus 36.72 {IQR: 32.28, 48.33}, 42.15 {IQR: 34.60, 44.96}, respectively]. In PD subjects, the severity of olfactory dysfunction also showed a significant negative correlation with the SAI response (r=-0.829, p<0.001).

CONCLUSIONS

Considering that the SAI response partly reflects central cholinergic dysfunction and that our study shows a relationship between the SAI response and the severity of olfactory dysfunction in PD, our findings indicate that cholinergic dysfunction could possibly contribute to the pathogenesis of olfactory dysfunction in early PD.

SIGNIFICANCE

SAI could be a useful marker to detect severe olfactory dysfunction in PD.

Gut dysfunction in Parkinson's disease

Early involvement of gut is observed in Parkinson’s disease (PD) and symptoms such as constipation may precede motor symptoms. α-Synuclein pathology is extensively evident in the gut and appears to follow a rostrocaudal gradient. The gut may act as the starting point of PD pathology with spread toward the central nervous system. This spread of the synuclein pathology raises the possibility of prion-like propagation in PD pathogenesis. Recently, the role of gut microbiota in PD pathogenesis has received attention and some phenotypic correlation has also been shown. The extensive involvement of the gut in PD even in its early stages has led to the evaluation of enteric α-synuclein as a possible biomarker of early PD. The clinical manifestations of gastrointestinal dysfunction in PD include malnutrition, oral and dental disorders, sialorrhea, dysphagia, gastroparesis, constipation, and defecatory dysfunction. These conditions are quite distressing for the patients and require relevant investigations and adequate management. Treatment usually involves both pharmacological and non-pharmacological measures. One important aspect of gut dysfunction is its contribution to the clinical fluctuations in PD. Dysphagia and gastroparesis lead to inadequate absorption of oral anti-PD medications. These lead to response fluctuations, particularly delayed-on and no-on, and there is significant relationship between levodopa pharmacokinetics and gastric emptying in patients with PD. Therefore, in such cases, alternative routes of administration or drug delivery systems may be required.

PET/MRI of central nervous system: current status and future perspective

Imaging plays an increasingly important role in the early diagnosis, prognosis prediction and therapy response evaluation of central nervous system (CNS) diseases. The newly emerging hybrid positron emission tomography/magnetic resonance imaging (PET/MRI) can perform "one-stop-shop" evaluation, including anatomic, functional, biochemical and metabolic information, even at the molecular level, for personalised diagnoses and treatments of CNS diseases. However, there are still several problems to be resolved, such as appropriate PET detectors, attenuation correction and so on. This review will introduce the basic physical principles of PET/MRI and its potential clinical applications in the CNS. We also provide the future perspectives for this field.

KEY POINTS

• PET/MRI can simultaneously provide anatomic, functional, biochemical and metabolic information. • PET/MRI has promising potential in various central nervous system diseases. • Research on the future implementation of PET/MRI is challenging and encouraging.