Benign versus malignant Parkinson disease: the unexpected silver lining of motor complications

On the Optimal Diagnosis and the Evolving Role of Pimavanserin in Parkinson's Disease Psychosis

Parkinson's disease (PD) is associated with the development of psychosis (PDP), including hallucinations and delusions, in more than half of the patient population. Optimal PD management must therefore involve considerations about both motor and non-motor symptoms. Often, clinicians fail to diagnosis psychosis in patients with PD and, when it is recognized, treat it suboptimally, despite the availability of multiple interventions. In this paper, we provide a summary of the current guidelines and clinical evidence for treating PDP with antipsychotics. We also provide recommendations for diagnosis and follow-up. Finally, an updated treatment algorithm for PDP that incorporates the use of pimavanserin, the only US FDA-approved drug for the treatment of PDP, was developed by extrapolating from a limited evidence base to bridge to clinical practice using expert opinion and experience. Because pimavanserin is only approved for the treatment of PDP in the US, in other parts of the world other recommendations and algorithms must be considered.

Evaluating the Diagnostic Potential of Combined Salivary and Skin Biomarkers in Parkinson's Disease

Oligomeric alpha-synuclein (α-syn) in saliva and phosphorylated α-syn deposits in the skin have emerged as promising diagnostic biomarkers for Parkinson's disease (PD). This study aimed to assess and compare the diagnostic value of these biomarkers in discriminating between 38 PD patients and 24 healthy subjects (HSs) using easily accessible biological samples. Additionally, the study sought to determine the diagnostic potential of combining these biomarkers and to explore their correlations with clinical features. Salivary oligomeric α-syn levels were quantified using competitive ELISA, while skin biopsies were analyzed through immunofluorescence to detect phosphorylated α-syn at Ser129 (p-S129). Both biomarkers individually were accurate in discriminating PD patients from HSs, with a modest agreement between them. The combined positivity of salivary α-syn oligomers and skin p-S129 aggregates differentiated PD patients from HSs with an excellent discriminative ability with an AUC of 0.9095. The modest agreement observed between salivary and skin biomarkers individually suggests that they may reflect different aspects of PD pathology, thus providing complementary information when combined. This study's results highlight the potential of utilizing a multimodal biomarker approach to enhance diagnostic accuracy in PD.

The Body, the Brain, the Environment, and Parkinson's Disease

The brain- and body-first models of Lewy body disorders predict that aggregated alpha-synuclein pathology usually begins in either the olfactory system or the enteric nervous system. In both scenarios the pathology seems to arise in structures that are closely connected to the outside world. Environmental toxicants, including certain pesticides, industrial chemicals, and air pollution are therefore plausible trigger mechanisms for Parkinson's disease and dementia with Lewy bodies. Here, we propose that toxicants inhaled through the nose can lead to pathological changes in alpha-synuclein in the olfactory system that subsequently spread and give rise to a brain-first subtype of Lewy body disease. Similarly, ingested toxicants can pass through the gut and cause alpha-synuclein pathology that then extends via parasympathetic and sympathetic pathways to ultimately produce a body-first subtype. The resulting spread can be tracked by the development of symptoms, clinical assessments, in vivo imaging, and ultimately pathological examination. The integration of environmental exposures into the brain-first and body-first models generates testable hypotheses, including on the prevalence of the clinical conditions, their future incidence, imaging patterns, and pathological signatures. The proposed link, though, has limitations and leaves many questions unanswered, such as the role of the skin, the influence of the microbiome, and the effects of ongoing exposures. Despite these limitations, the interaction of exogenous factors with the nose and the gut may explain many of the mysteries of Parkinson's disease and open the door toward the ultimate goal -prevention.

Parkinson's Disease and Dementia with Lewy Bodies: One and the Same

The question whether Parkinson's disease dementia (PDD) and dementia with Lewy bodies (DLB) are expressions of the same underlying disease has been vigorously debated for decades. The recently proposed biological definitions of Lewy body disease, which do not assign any particular importance to the dopamine system over other degenerating neurotransmitter systems, has once more brought the discussion about different types of Lewy body disease to the forefront. Here, we briefly compare PDD and DLB in terms of their symptoms, imaging findings, and neuropathology, ultimately finding them to be indistinguishable. We then present a conceptual framework to demonstrate how one can view different clinical syndromes as manifestations of a shared underlying Lewy body disease. Early Parkinson's disease, isolated RBD, pure autonomic failure and other autonomic symptoms, and perhaps even psychiatric symptoms, represent diverse manifestations of the initial clinical stages of Lewy body disease. They are characterized by heterogeneous and comparatively limited neuronal dysfunction and damage. In contrast, Lewy body dementia, an encompassing term for both PDD and DLB, represents a more uniform and advanced stage of the disease. Patients in this category display extensive and severe Lewy pathology, frequently accompanied by co-existing pathologies, as well as multi-system neuronal dysfunction and degeneration. Thus, we propose that Lewy body disease should be viewed as a single encompassing disease entity. Phenotypic variance is caused by the presence of individual risk factors, disease mechanisms, and co-pathologies. Distinct subtypes of Lewy body disease can therefore be defined by subtype-specific disease mechanisms or biomarkers.

Investigating the potential effects of α-synuclein aggregation on susceptibility to chronic stress in a mouse Parkinson's disease model

BACKGROUND

Parkinson's disease (PD) is a motor disorder characterized by the degeneration of dopaminergic neurons, putatively due to the accumulation of α-synuclein (α-syn) in Lewy bodies (LBs) in Substantia Nigra. PD is also associated with the formation of LBs in brain areas responsible for emotional and cognitive regulation such as the amygdala and prefrontal cortex, and concurrent depression prevalence in PD patients. The exact link between dopaminergic cell loss, α-syn aggregation, depression, and stress, a major depression risk factor, is unclear. Therefore, we aimed to explore the interplay between sensitivity to chronic stress and α-syn aggregation.

METHODS

Bilateral injections of α-syn preformed fibrils (PFFs) into the striatum of C57Bl/6 J mice were used to induce α-syn aggregation. Three months after injections, animals were exposed to chronic social defeat stress.

RESULTS

α-syn aggregation did not affect stress susceptibility but independently caused increased locomotor activity in the open field test, reduced anxiety in the light-dark box test, and increased active time in the tail suspension test. Ex vivo analysis revealed modest dopaminergic neuron loss in the substantia nigra and reduced dopaminergic innervation in the dorsal striatum in PFFs injected groups. α-Syn aggregates were prominent in the amygdala, prefrontal cortex, and substantia nigra, with minimal α-syn aggregation in the raphe nuclei and locus coeruleus.

CONCLUSIONS

Progressive bilateral α-syn aggregation might lead to compensatory activity increase and alterations in emotionally regulated behavior, without affecting stress susceptibility. Understanding how α-syn aggregation and degeneration in specific brain structures contribute to depression and anxiety in PD patients requires further investigation.

Prevalence of hallucinations in Parkinson's patients: meta-analysis of International studies

BACKGROUND

Parkinson's disease (PD) is one of the common causes of disability in the elderly. This study aims to estimate the prevalence of hallucinations in Parkinson's patients in the world.

METHODS

A systematic review of PubMed/Medline, ISI Web of Knowledge, and Google Scholar was conducted from 2017 to 2022. This study investigated the prevalence of hallucinations in Parkinson's patients. Point prevalence was analyzed with a 95% confidence interval. The variances of each study were calculated using the binomial distribution formula The researcher used Cochrane Q-test with a significance level of less than 0.1 to check the heterogeneity between studies and the change index assigned to heterogeneity I2. Due to the heterogeneity between the studies, the random effects model was used to combine the results of the studies. All statistical analyses were performed by STATA version 14 software using meta-analysis commands.

RESULTS

Reports indicated that the prevalence of hallucinations in Parkinson's patients in 32 studies was 28% (0.22-0.34 = 95%CI). The highest prevalence was 34% and 95% CI = 0.07- 0.61 in developing countries and 27% with CI = 0.33-0.21 in developed countries. Reports showed the prevalence in men was 30% (CI = 0.22-0.38) and in women 23% (95% CI = 0.14-0.31).

CONCLUSIONS

Considering the relatively high prevalence of hallucinations in these patients, checking up for the presence of hallucinations on every visit of Parkinson's patients is recommended, and providing appropriate treatment for that is necessary.

The brain-first vs. body-first model of Parkinson's disease with comparison to alternative models

The ultimate origin of Lewy body disorders, including Parkinson's disease (PD) and Dementia with Lewy bodies (DLB), is still incompletely understood. Although a large number of pathogenic mechanisms have been implicated, accumulating evidence support that aggregation and neuron-to-neuron propagation of alpha-synuclein may be the core feature of these disorders. The synuclein, origin, and connectome (SOC) disease model of Lewy body disorders was recently introduced. This model is based on the hypothesis that in the majority of patients, the first alpha-synuclein pathology arises in single location and spreads from there. The most common origin sites are the enteric nervous system and the olfactory system. The SOC model predicts that gut-first pathology leads to a clinical body-first subtype characterized by prodromal autonomic symptoms and REM sleep behavior disorder. In contrast, olfactory-first pathology leads to a brain-first subtype with fewer non-motor symptoms before diagnosis. The SOC model further predicts that body-first patients are older, more commonly develop symmetric dopaminergic degeneration, and are at increased risk of dementia-compared to brain-first patients. In this review, the SOC model is explained and compared to alternative models of the pathogenesis of Lewy body disorders, including the Braak staging system, and the Unified Staging System for Lewy Body Disorders. Postmortem evidence from brain banks and clinical imaging data of dopaminergic and cardiac sympathetic loss is reviewed. It is concluded that these datasets seem to be more compatible with the SOC model than with those alternative disease models of Lewy body disorders.

15-Year Subthalamic Deep Brain Stimulation outcome in a Parkinson's disease patient with Parkin gene mutation: a case report

INTRODUCTION

Parkinson's Disease (PD) patients with Parkin gene (PRKN) mutations show good response to subthalamic deep brain stimulation (STN-DBS). Currently, the longest follow-up available of these patients is 6 years. We report a very long-term outcome (more than 15 years) of a STN-DBS-treated patient with a compound heterozygous deletion of exons 3 and 11 of the PRKN gene.

CASE REPORT

In 1993, a 39-year-old male was diagnosed with PD after the onset of resting tremor. Levodopa was started, and during the following 10 years, he reported good motor symptoms control, with only mild modification of levodopa intake and pramipexole introduction. In 2005, he developed disabling motor fluctuations and dyskinesia. In 2007, he underwent bilateral STN-DBS, with a marked improvement of motor symptoms and fluctuations during the following years. After 6 years, he reported mild motor fluctuations, improved after stimulation and treatment modifications. After 10 years he showed diphasic dyskinesias, feet dystonia, postural instability, and gambling (resolved after pramipexole discontinuation). In 2018, he developed a non-amnestic single-domain mild cognitive impairment (MCI). In 2023, after more than 15 years of STN-DBS, motor symptoms and fluctuations are still well controlled. He reports mild dysphagia, mild depression, and multiple-domain MCI. His quality of life is better than before surgery, and he still reports a subjective significant improvement from STN-DBS.

CONCLUSION

Confirming the very long-term efficacy of STN-DBS in PRKN-mutated patients, our case report underlines their peculiar suitability for surgical treatment.

Two-year clinical progression in focal and diffuse subtypes of Parkinson's disease

Heterogeneity in Parkinson's disease (PD) presents a barrier to understanding disease mechanisms and developing new treatments. This challenge may be partially overcome by stratifying patients into clinically meaningful subtypes. A recent subtyping scheme classifies de novo PD patients into three subtypes: mild-motor predominant, intermediate, or diffuse-malignant, based on motor impairment, cognitive function, rapid eye movement sleep behavior disorder (RBD) symptoms, and autonomic symptoms. We aimed to validate this approach in a large longitudinal cohort of early-to-moderate PD (n = 499) by assessing the influence of subtyping on clinical characteristics at baseline and on two-year progression. Compared to mild-motor predominant patients (42%), diffuse-malignant patients (12%) showed involvement of more clinical domains, more diffuse hypokinetic-rigid motor symptoms (decreased lateralization and hand/foot focality), and faster two-year progression. These findings extend the classification of diffuse-malignant and mild-motor predominant subtypes to early-to-moderate PD and suggest that different pathophysiological mechanisms (focal versus diffuse cerebral propagation) may underlie distinct subtype classifications.

How should future clinical trials be designed in the search for disease-modifying therapies for Parkinson's disease?

INTRODUCTION

Although there has been substantial progress in research and innovations in symptomatic treatments, similar success has not been achieved in disease-modifying therapy (DMT) for Parkinson's disease (PD). Considering the enormous motor, psychosocial and financial burden associated with PD, safe and effective DMT is of paramount importance.

AREAS COVERED

One of the reasons for the lack of progress in DMT for PD is poor or inappropriate design of clinical trials. In the first part of the article, the authors focus on the plausible reasons why the previous trials have failed and in the latter part, they provide their perspectives on future DMT trials.

EXPERT OPINION

There are several potential reasons why previous trials have failed, including broad clinical and etiopathogenic heterogeneity of PD, poor definition and documentation of target engagement, lack of appropriate biomarkers and outcome measures, and short duration of follow-up. To address these deficiencies, future trials may consider- (i) a more customized approach to select the most suitable participants and therapeutic approaches, (ii) explore combination therapies that would target multiple pathogenetic mechanisms, and (iii) moving beyond targeting only motor symptoms to also assessing non-motor features of PD in well-designed longitudinal studies.

Pesticides and the Microbiome-Gut-Brain Axis: Convergent Pathways in the Pathogenesis of Parkinson's Disease

The increasing global burden of Parkinson's disease (PD), termed the PD pandemic, is exceeding expectations related purely to population aging and is likely driven in part by lifestyle changes and environmental factors. Pesticides are well recognized risk factors for PD, supported by both epidemiological and experimental evidence, with multiple detrimental effects beyond dopaminergic neuron damage alone. The microbiome-gut-brain axis has gained much attention in recent years and is considered to be a significant contributor and driver of PD pathogenesis. In this narrative review, we first focus on how both pesticides and the microbiome may influence PD initiation and progression independently, describing pesticide-related central and peripheral neurotoxicity and microbiome-related local and systemic effects due to dysbiosis and microbial metabolites. We then depict the bidirectional interplay between pesticides and the microbiome in the context of PD, synthesizing current knowledge about pesticide-induced dysbiosis, microbiome-mediated alterations in pesticide availability, metabolism and toxicity, and complex systemic pesticide-microbiome-host interactions related to inflammatory and metabolic pathways, insulin resistance and other mechanisms. An overview of the unknowns follows, and the role of pesticide-microbiome interactions in the proposed body-/brain-first phenotypes of PD, the complexity of environmental exposures and gene-environment interactions is discussed. The final part deals with possible further steps for translation, consisting of recommendations on future pesticide use and research as well as an outline of promising preventive/therapeutic approaches targeted on strengthening or restoring a healthy gut microbiome, closing with a summary of current gaps and future perspectives in the field.

The dilemma between milestones of progression versus clinical scales in Parkinson's disease

There are significant challenges in accurately documenting the progression of Parkinson's disease (PD). The disease course is highly heterogeneous, there are no validated biomarkers, and we are reliant on repeated clinical measures to assess disease state over time. Yet, the ability to chart disease progression accurately is vital in both observational and interventional study designs, where reliable measures are critical to determine whether an outcome has been met. In this chapter, we first discuss the natural history of PD, including the spectrum of clinical presentation and expected developments through the course of the disease. We then explore in detail the current strategies for measuring disease progression, which can be broadly divided into: (i) the use of quantitative clinical scales; and (ii) determination of the onset time of key milestones. We discuss the strengths and limitations of these approaches for use in clinical trials, with a particular focus on disease modification trials. The selection of outcome measures for a particular study will depend on multiple factors, but trial duration is an important determinant. Milestones are reached over a course of years rather than months, and hence clinical scales with sensitivity to change are needed for short-term studies. However, milestones represent important markers of disease stage which are not confounded by symptomatic therapies and are of critical relevance to the patient. Prolonged but low intensity follow-up beyond a limited period of treatment with a putative disease-modifying agent may allow milestones to be incorporated into evaluation of efficacy in a practical and cost-effective way.

A postmortem study suggests a revision of the dual-hit hypothesis of Parkinson's disease

The dual-hit hypothesis of Parkinson's disease (PD) originally postulated that a neurotropic pathogen leads to formation of α-synuclein pathology in the olfactory bulb (OB) and dorsal motor nucleus of the vagus (DMV) and then invades the brain from these two entry points. Little work has been conducted to validate an important underlying premise for the dual-hit hypothesis, namely that the initial Lewy pathology does arise simultaneously in the OB and the enteric nervous system (ENS) plexuses and DMV at the earliest disease stage. We conducted a focused re-analysis of two postmortem datasets, which included large numbers of mild Lewy body disease (LBD) cases. We found that cases with α-synuclein pathology restricted to the peripheral autonomic nervous system and/or lower brainstem (early body-first LBD cases) very rarely had any OB pathology, suggesting that Lewy pathology commonly arises in the ENS without concomitant involvement of the OB. In contrast, cases with mild amygdala-predominant Lewy pathology (early brain-first LBD cases) nearly always showed OB pathology. This is compatible with the first pathology being triggered in the OB or amygdala followed by secondary spreading to connected structures, but without early involvement of the ENS or lower brainstem. These observations support that the pathologic process starts in either the olfactory bulb or the ENS, but rarely in the olfactory bulb and gut simultaneously. More studies on neuropathological datasets are warranted to reproduce these findings. The agreement between the revised single-hit hypothesis and the recently proposed brain-first vs. body-first model of LBD is discussed.

Axial impairment and falls in Parkinson’s disease: 15 years of subthalamic deep brain stimulation

In this retrospective study, we longitudinally analyzed axial impairment and falls in people with Parkinson’s disease (PD) and subthalamic nucleus deep brain stimulation (STN-DBS). Axial scores and falling frequency were examined at baseline, and 1, 10, and 15 years after surgery. Preoperative demographic and clinical data, including PD duration and severity, phenotype, motor and cognitive scales, medications, and vascular changes on neuroimaging were examined as possible risk factors through Kaplan–Meier and Cox regression analyses. Of 302 individuals examined before and at 1 year after surgery, 102 and 57 were available also at 10 and 15 years of follow-up, respectively. Axial scores were similar at baseline and at 1 year but worsened at 10 and 15 years. The prevalence rate of frequent fallers progressively increased from baseline to 15 years. Preoperative axial scores, frontal dysfunction and age at PD onset were risk factors for axial impairment progression after surgery. Axial scores, akinetic/rigid phenotype, age at disease onset and disease duration at surgery predicted frequent falls. Overall, axial signs progressively worsened over the long-term period following STN-DBS, likely related to the progression of PD, especially in a subgroup of subjects with specific risk factors.

Smoking is associated with age at disease onset in Parkinson's disease

BACKGROUND

Previous studies linked disease-progression variables such as age at onset or survival to both genetic, and non-genetic factors in Parkinson's disease (PD) patients.

OBJECTIVE

The aim of this study was to assess how genetic and non genetic factors act as modifiers of age at onset and survival and in a cohort of 753 PD patients, and to determine how these variables interact to define the overall risk.

METHODS

We analyzed the effect of gender, tobacco, alcohol, type of PD (genetic, gPD or idiopathic, iPD) and three genetic variants rs5848- GRN, rs1042522- TP53 and APOE. We studied two cohorts (PPMI and IPDGC) to replicate positive results.

RESULTS

Regarding age at onset, male smokers PD had a significantly lower mean age compared to non-smoker (p = 0.001). APOE-Ɛ4 carriers had a younger onset-age compared to non-carriers (p = 0.03) in the Spanish cohort, but these results were not replicated in the other cohorts. Concerning survival, PD patients with an early onset (below 50 years) had an increased survival rate (p < 0.001).

CONCLUSIONS

Our study showed how several genetic and non-genetic risk factors influenced the age at onset and survival in PD.

Minor hallucinations in isolated rapid eye movement sleep behavior disorder indicative of early phenoconversion: A preliminary study

OBJECTIVES

Minor hallucinations (MH) are psychotic symptoms that can occur anywhere between prodromal to early Parkinson's disease and after onset of motor problems. MH include visual illusions, presence hallucinations, and passage hallucinations. Isolated rapid eye movement sleep behavior disorder (RBD) is a harbinger of neurodegenerative diseases. We conducted a retrospective cohort study to investigate the clinical characteristics of isolated RBD with MH and the risk of phenoconversion.

MATERIALS AND METHODS

We retrospectively analyzed the data of 36 patients with isolated RBD (four females; median age, 75.0 years). We defined cases reporting at least one minor hallucination as RBD with MH. Demographic data and cognitive function were compared between patients with and without MH, and Cox proportional hazards models estimated the risk of phenoconversion.

RESULTS

We included 10 (27.8%) patients with MH and 26 (72.2%) without MH. Patients with MH were older, had less dopamine transporter accumulation, more severe autonomic dysfunction, more depressive symptoms, and lower verbal fluency and symbol coding test scores than patients without MH. After follow-up (median, 2.50 years), 13.9% (5/36) of all patients developed phenoconversion (Parkinson's disease, two patients; dementia with Lewy bodies, three patients). The rate of phenoconversion was significantly higher in patients with MH (40.0% vs. 3.8%, p = .005). The Cox proportional hazards model adjusted for age, sex, and disease duration revealed that MH was a significant risk factor for phenoconversion (hazard ratio, 14.72; 95% confidence interval, 1.35-160.5).

CONCLUSIONS

Minor hallucinations may be utilized as early clinical markers for prodromal estimation of neurodegenerative diseases.

Clinical and imaging evidence of brain-first and body-first Parkinson's disease

Braak's hypothesis has been extremely influential over the last two decades. However, neuropathological and clinical evidence suggest that the model does not conform to all patients with Parkinson's disease (PD). To resolve this controversy, a new model was recently proposed; in brain-first PD, the initial α-synuclein pathology arise inside the central nervous system, likely rostral to the substantia nigra pars compacta, and spread via interconnected structures - eventually affecting the autonomic nervous system; in body-first PD, the initial pathological α-synuclein originates in the enteric nervous system with subsequent caudo-rostral propagation to the autonomic and central nervous system. By using REM-sleep behavior disorder (RBD) as a clinical identifier to distinguish between body-first PD (RBD-positive at motor symptom onset) and brain-first PD (RBD-negative at motor symptom onset), we explored the literature to evaluate clinical and imaging differences between these proposed subtypes. Body-first PD patients display: 1) a larger burden of autonomic symptoms - in particular orthostatic hypotension and constipation, 2) more frequent pathological α-synuclein in peripheral tissues, 3) more brainstem and autonomic nervous system involvement in imaging studies, 4) more symmetric striatal dopaminergic loss and motor symptoms, and 5) slightly more olfactory dysfunction. In contrast, only minor cortical metabolic alterations emerge before motor symptoms in body-first. Brain-first PD is characterized by the opposite clinical and imaging patterns. Patients with pathological LRRK2 genetic variants mostly resemble a brain-first PD profile whereas patients with GBA variants typically conform to a body-first profile. SNCA-variant carriers are equally distributed between both subtypes. Overall, the literature indicates that body-first and brain-first PD might be two distinguishable entities on some clinical and imaging markers.

Cognitive Correlates of Visual and Minor Hallucinations in Parkinson's Disease

INTRODUCTION

Psychosis is one of the incapacitating nonmotor symptoms of Parkinson's disease (PD). Although several risk factors that include older age, rapid eye movement sleep behavior disorder, depression, and cognitive dysfunction have been identified, the exact neural correlates remain elusive. As cognitive impairment has a close association with psychosis in PD, it is useful to know the spectrum of cognitive impairment in PD patients with psychosis (PD-P).

METHODS

This cross-sectional study compared various cognitive parameters of PD-P (visual/minor hallucinations) and PD patients with no psychosis (PD-NP). A neuropsychological battery encapsulating several cognitive domains (executive, visuospatial, learning, and memory) was used for the cognitive assessment of 37 PD-P and 51 PD-NP patients who were matched for age, gender, education, and disease duration.

RESULTS

The two groups were comparable in terms of disease severity and stage. Although the groups had a comparable mean score on Montreal cognitive assessment, the PD-P group performed poorly in tests focused on executive function (color trail test, forward digit span), verbal learning and memory (Rey auditory and verbal learning test), and visuospatial functions (complex figure test, corsi block tapping test). Those with complex visual hallucinations performed poorly in the color trial test (part A) compared to those with minor hallucinations.

CONCLUSION

Psychosis is associated with a multidomain cognitive dysfunction in PD. All PD patients should undergo detailed cognitive assessment as cognitive dysfunction may be a marker of psychosis in the future. Additional longitudinal studies are warranted to obtain detailed insights into this issue.

Neuropathological evidence of body-first vs. brain-first Lewy body disease

Aggregation of alpha-synuclein into inclusion bodies, termed Lewy pathology, is a defining feature of Parkinson's disease (PD) and Dementia with Lewy bodies (DLB). In the majority of post mortem cases, the distribution of Lewy pathology seems to follow two overarching patterns: a caudo-rostral pattern with relatively more pathology in the brainstem than in the telencephalon, and an amygdala-centered pattern with the most abundant pathology in the "center of the brain", including the amygdala, entorhinal cortex, and substantia nigra, and relatively less pathology in the lower brainstem and spinal autonomic nuclei. The recent body-first versus brain-first model of Lewy Body Disorders proposes that the initial pathogenic alpha-synuclein in some patients originates in the enteric nervous system with secondary spreading to the brain; and in other patients originates inside the CNS with secondary spreading to the lower brainstem and peripheral autonomic nervous system. Here, we use two existing post mortem datasets to explore the possibility that clinical body-first and brain-first subtypes are equivalent to the caudo-rostral and amygdala-centered patterns of Lewy pathology seen at post mortem.

Asymmetric Dopaminergic Dysfunction in Brain-First versus Body-First Parkinson's Disease Subtypes

BACKGROUND

We have hypothesized that Parkinson's disease (PD) comprises two subtypes. Brain-first, where pathogenic α-synuclein initially forms unilaterally in one hemisphere leading to asymmetric nigrostriatal degeneration, and body-first with initial enteric pathology, which spreads through overlapping vagal innervation leading to more symmetric brainstem involvement and hence more symmetric nigrostriatal degeneration. Isolated REM sleep behaviour disorder has been identified as a strong marker of the body-first type.

OBJECTIVE

To analyse striatal asymmetry in [18F]FDOPA PET and [123I]FP-CIT DaT SPECT data from iRBD patients, de novo PD patients with RBD (PD +RBD) and de novo PD patients without RBD (PD - RBD). These groups were defined as prodromal body-first, de novo body-first, and de novo brain-first, respectively.

METHODS

We included [18F]FDOPA PET scans from 21 iRBD patients, 11 de novo PD +RBD, 22 de novo PD - RBD, and 18 controls subjects. Also, [123I]FP-CIT DaT SPECT data from iRBD and de novo PD patients with unknown RBD status from the PPPMI dataset was analysed. Lowest putamen specific binding ratio and putamen asymmetry index (AI) was defined.

RESULTS

Nigrostriatal degeneration was significantly more symmetric in patients with RBD versus patients without RBD or with unknown RBD status in both FDOPA (p = 0.001) and DaT SPECT (p = 0.001) datasets.

CONCLUSION

iRBD subjects and de novo PD +RBD patients present with significantly more symmetric nigrostriatal dopaminergic degeneration compared to de novo PD - RBD patients. The results support the hypothesis that body-first PD is characterized by more symmetric distribution most likely due to more symmetric propagation of pathogenic α-synuclein compared to brain-first PD.

The α-Synuclein Origin and Connectome Model (SOC Model) of Parkinson's Disease: Explaining Motor Asymmetry, Non-Motor Phenotypes, and Cognitive Decline

A new model of Parkinson's disease (PD) pathogenesis is proposed, the α-Synuclein Origin site and Connectome (SOC) model, incorporating two aspects of α-synuclein pathobiology that impact the disease course for each patient: the anatomical location of the initial α-synuclein inclusion, and α-synuclein propagation dependent on the ipsilateral connections that dominate connectivity of the human brain. In some patients, initial α-synuclein pathology occurs within the CNS, leading to a brain-first subtype of PD. In others, pathology begins in the peripheral autonomic nervous system, leading to a body-first subtype. In brain-first cases, it is proposed that the first pathology appears unilaterally, often in the amygdala. If α-synuclein propagation depends on connection strength, a unilateral focus of pathology will disseminate more to the ipsilateral hemisphere. Thus, α-synuclein spreads mainly to ipsilateral structures including the substantia nigra. The asymmetric distribution of pathology leads to asymmetric dopaminergic degeneration and motor asymmetry. In body-first cases, the α-synuclein pathology ascends via the vagus to both the left and right dorsal motor nuclei of the vagus owing to the overlapping parasympathetic innervation of the gut. Consequently, the initial α-synuclein pathology inside the CNS is more symmetric, which promotes more symmetric propagation in the brainstem, leading to more symmetric dopaminergic degeneration and less motor asymmetry. At diagnosis, body-first patients already have a larger, more symmetric burden of α-synuclein pathology, which in turn promotes faster disease progression and accelerated cognitive decline. The SOC model is supported by a considerable body of existing evidence and may have improved explanatory power.

Prevalence of Non-Motor Symptoms and Non-Motor Fluctuations in Parkinson's Disease Using the MDS-NMS

Background

Non-motor symptoms (NMS) are frequent in Parkinson's disease (PD).

Objectives

To estimate the prevalence of NMS and of non-motor fluctuations (NMF) using the Movement Disorders Society-Non-Motor Rating Scale (MDS-NMS) and other scales assessing NMS, and their relationship with sex and PD severity.

Methods

Cross-sectional study with a sample of 402 PD patients. The Hoehn and Yahr staging system (HY), Clinical Impression of Severity Index for PD (CISI-PD), MDS-NMS (including NMF- subscale), Non-Motor Symptoms scale (NMSS), and MDS-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) were applied. A NMS was considered present when scored ≥1. Differences in scores by sex and HY, CISI-PD, and MDS-UPDRS severity levels were calculated using Fisher's exact and chi-squared tests.

Results

Using the MDS-NMS, NMS were present in 99.7% of patients and the mean number of NMS was 16.13 (SD: 9.36). The most prevalent NMS was muscle, joint or back pain (67.4% of the sample) and the least prevalent was dopamine dysregulation syndrome (2.2%). Feeling sad or depressed was significantly more prevalent in women. Using the MDS-NMS revealed more NMS than the other scales assessing NMS. NMF were present in 41% of the sample, with fatigue being the most prevalent symptom (68.5% patients with NMF), and no differences by sex. Patients with greater PD severity had higher prevalence of NMS than patients with lower severity.

Conclusions

Almost all patients with PD experience NMS, and many experience NMF. Prevalence rates for NMS using the MDS-NMS are higher than on other scales used and increase with higher disease severity.

Deep Brain Stimulation Selection Criteria for Parkinson's Disease: Time to Go beyond CAPSIT-PD

Despite being introduced in clinical practice more than 20 years ago, selection criteria for deep brain stimulation (DBS) in Parkinson's disease (PD) rely on a document published in 1999 called 'Core Assessment Program for Surgical Interventional Therapies in Parkinson's Disease'. These criteria are useful in supporting the selection of candidates. However, they are both restrictive and out-of-date, because the knowledge on PD progression and phenotyping has massively evolved. Advances in understanding the heterogeneity of PD presentation, courses, phenotypes, and genotypes, render a better identification of good DBS outcome predictors a research priority. Additionally, DBS invasiveness, cost, and the possibility of serious adverse events make it mandatory to predict as accurately as possible the clinical outcome when informing the patients about their suitability for surgery. In this viewpoint, we analyzed the pre-surgical assessment according to the following topics: early versus delayed DBS; the evolution of the levodopa challenge test; and the relevance of axial symptoms; patient-centered outcome measures; non-motor symptoms; and genetics. Based on the literature, we encourage rethinking of the selection process for DBS in PD, which should move toward a broad clinical and instrumental assessment of non-motor symptoms, quantitative measurement of gait, posture, and balance, and in-depth genotypic and phenotypic characterization.

Extended Study of NUS1 Gene Variants in Parkinson's Disease

Parkinson's disease (PD), is the second most common neurodegenerative disorder worldwide. Genetic, environmental factors, and aging are its primary development contributors. Recently the nuclear undecaprenyl pyrophosphate synthase 1 homolog (Saccharomyces cerevisiae) gene (NUS1) was reported as a candidate gene for PD, which raised our interest in the relationship between NUS1 and PD. This study was aimed to further explore the role of NUS1 variants in PD development. Genetic analysis for 308 Han-Chinese PD patients and 308 ethnically matched controls using whole exome sequencing was conducted. Additionally, a total of 60 articles involving in whole exome/whole genome sequencing or direct sequencing of the NUS1 gene from PubMed database between July 1, 2011 and August 26, 2020 were reviewed to evaluate PD-associated NUS1 variants. No potentially pathogenic NUS1 variant was found in 308 PD cases, and no frequency biases between 308 PD cases and 308 controls were observed for the only non-synonymous variant p.Asp179Glu (genotype: χ² = 0.093, P = 0.761; allele: χ² = 0.092, P = 0.762). No pathogenic or disease-associated NUS1 variant was reported in the 5,636 PD cases of the 60 articles. In summary, current findings indicate that NUS1 variant is not a common genetic factor contributing to PD.

Early autonomic and cognitive dysfunction in PD, DLB and MSA: blurring the boundaries between α-synucleinopathies

Differential diagnosis between Parkinson's disease, dementia with Lewy bodies and multiple system atrophy can be difficult, especially because in early phase they might present with overlapping clinical features. Notably, orthostatic hypotension and cognitive dysfunction are common nonmotor aspects of parkinsonian syndromes and can be both present from the earliest stages of all α-synucleinopathies, indicating a common neurobiological basis in their strong relationship. In view of the increasing awareness about the prevalence of mild cognitive dysfunction in multiple system atrophy, the relevance of autonomic dysfunction in demented parkinsonian patients, the critical role of non-motor symptoms in clustering Parkinson's disease patients and the shift to studying patients in the prodromal phase, we will discuss some intrinsic limitations of current clinical diagnostic criteria, even when applied by movement disorder specialists. In particular, we will focus on the early coexistence of autonomic and cognitive dysfunction in the setting of overt or latent parkinsonism as pitfalls in the differential diagnosis of α-synucleinopathies. As early and accurate diagnosis remains of outmost importance for counselling of patients and timely enrolment into disease-modifying clinical trials, a continuous effort of research community is ongoing to further improve the clinical diagnostic accuracy of α-synucleinopathies.