Can we clinically diagnose dementia with Lewy bodies yet?

On gaps of clinical diagnosis of dementia subtypes: A study of Alzheimer's disease and Lewy body disease

Introduction

Alzheimer's disease (AD) and Lewy body disease (LBD) are the two most common neurodegenerative dementias and can occur in combination (AD+LBD). Due to overlapping biomarkers and symptoms, clinical differentiation of these subtypes could be difficult. However, it is unclear how the magnitude of diagnostic uncertainty varies across dementia spectra and demographic variables. We aimed to compare clinical diagnosis and post-mortem autopsy-confirmed pathological results to assess the clinical subtype diagnosis quality across these factors.

Methods

We studied data of 1,920 participants recorded by the National Alzheimer's Coordinating Center from 2005 to 2019. Selection criteria included autopsy-based neuropathological assessments for AD and LBD, and the initial visit with Clinical Dementia Rating (CDR) stage of normal, mild cognitive impairment, or mild dementia. Longitudinally, we analyzed the first visit at each subsequent CDR stage. This analysis included positive predictive values, specificity, sensitivity and false negative rates of clinical diagnosis, as well as disparities by sex, race, age, and education. If autopsy-confirmed AD and/or LBD was missed in the clinic, the alternative clinical diagnosis was analyzed.

Findings

In our findings, clinical diagnosis of AD+LBD had poor sensitivities. Over 61% of participants with autopsy-confirmed AD+LBD were diagnosed clinically as AD. Clinical diagnosis of AD had a low sensitivity at the early dementia stage and low specificities at all stages. Among participants diagnosed as AD in the clinic, over 32% had concurrent LBD neuropathology at autopsy. Among participants diagnosed as LBD, 32% to 54% revealed concurrent autopsy-confirmed AD pathology. When three subtypes were missed by clinicians, "No cognitive impairment" and "primary progressive aphasia or behavioral variant frontotemporal dementia" were the leading primary etiologic clinical diagnoses. With increasing dementia stages, the clinical diagnosis accuracy of black participants became significantly worse than other races, and diagnosis quality significantly improved for males but not females.

Discussion

These findings demonstrate that clinical diagnosis of AD, LBD, and AD+LBD are inaccurate and suffer from significant disparities on race and sex. They provide important implications for clinical management, anticipatory guidance, trial enrollment and applicability of potential therapies for AD, and promote research into better biomarker-based assessment of LBD pathology.

Characterisation of functional deficits induced by AAV overexpression of alpha-synuclein in rats

Background

In the last decades different preclinical animal models of Parkinson's disease (PD) have been generated, aiming to mimic the progressive neuronal loss of midbrain dopaminergic (DA) cells as well as motor and non-motor impairment. Among all the available models, AAV-based models of human alpha-synuclein (h-aSYN) overexpression are promising tools for investigation of disease progression and therapeutic interventions.

Objectives

The goal with this work was to characterise the impairment in motor and non-motor domains following nigrostriatal overexpression of h-aSYN and correlate the behavioural deficits with histological assessment of associated pathology.

Methods

Intranigral injection of an AAV9 expressing h-aSYN was compared with untreated animals, 6-OHDA and AAV9 expressing either no transgene or GFP. The animals were assessed on a series of simple and complex behavioural tasks probing motor and non-motor domains. Post-mortem neuropathology was analysed using immunohistochemical methods.

Results

Overexpression of h-aSYN led to progressive degeneration of DA neurons of the SN and axonal terminals in the striatum (STR). We observed extensive nigral and striatal pathology, resembling that of human PD brain, as well as the development of stable progressive deficit in simple motor tasks and in non-motor domains such as deficits in motivation and lateralised neglect.

Conclusions

In the present work we characterized a rat model of PD that closely resembles human PD pathology at the histological and behavioural level. The correlation of cell loss with behavioural performance enables the selection of rats which can be used in neuroprotective or neurorestorative therapies.

Revisiting the specificity and ability of phospho-S129 antibodies to capture alpha-synuclein biochemical and pathological diversity

Antibodies against phosphorylated alpha-synuclein (aSyn) at S129 have emerged as the primary tools to investigate, monitor, and quantify aSyn pathology in the brain and peripheral tissues of patients with Parkinson's disease and other neurodegenerative diseases. Herein, we demonstrate that the co-occurrence of multiple pathology-associated C-terminal post-translational modifications (PTMs) (e.g., phosphorylation at Tyrosine 125 or truncation at residue 133 or 135) differentially influences the detection of pS129-aSyn species by pS129-aSyn antibodies. These observations prompted us to systematically reassess the specificity of the most commonly used pS129 antibodies against monomeric and aggregated forms of pS129-aSyn in mouse brain slices, primary neurons, mammalian cells and seeding models of aSyn pathology formation. We identified two antibodies that are insensitive to pS129 neighboring PTMs. Although most pS129 antibodies showed good performance in detecting aSyn aggregates in cells, neurons and mouse brain tissue containing abundant aSyn pathology, they also showed cross-reactivity towards other proteins and often detected non-specific low and high molecular weight bands in aSyn knock-out samples that could be easily mistaken for monomeric or high molecular weight aSyn species. Our observations suggest that not all pS129 antibodies capture the biochemical and morphological diversity of aSyn pathology, and all should be used with the appropriate protein standards and controls when investigating aSyn under physiological conditions. Finally, our work underscores the need for more pS129 antibodies that are not sensitive to neighboring PTMs and more thorough characterization and validation of existing and new antibodies.

A NAC domain mutation (E83Q) unlocks the pathogenicity of human alpha-synuclein and recapitulates its pathological diversity

The alpha-synuclein mutation E83Q, the first in the NAC domain of the protein, was recently identified in a patient with dementia with Lewy bodies. We investigated the effects of this mutation on the aggregation of aSyn monomers and the structure, morphology, dynamic, and seeding activity of the aSyn fibrils in neurons. We found that it markedly accelerates aSyn fibrillization and results in the formation of fibrils with distinct structural and dynamic properties. In cells, this mutation is associated with higher levels of aSyn, accumulation of pS129, and increased toxicity. In a neuronal seeding model of Lewy body (LB) formation, the E83Q mutation significantly enhances the internalization of fibrils into neurons, induces higher seeding activity, and results in the formation of diverse aSyn pathologies, including the formation of LB-like inclusions that recapitulate the immunohistochemical and morphological features of brainstem LBs observed in brains of patients with Parkinson's disease.

Sequential or Simultaneous Injection of Preformed Fibrils and AAV Overexpression of Alpha-Synuclein Are Equipotent in Producing Relevant Pathology and Behavioral Deficits

BACKGROUND

Preclinical rodent models for Parkinson's disease (PD) based on viral human alpha-synuclein (h-αSyn) overexpression recapitulate some of the pathological hallmarks as it presents in humans, such as progressive cell loss and additional synucleinopathy in cortical and subcortical structures. Recent studies have combined viral vector-based overexpression of human wild-type αSyn with the sequential or simultaneous inoculation of preformed fibrils (PFFs) derived from human αSyn.

OBJECTIVE

The goal of the study was to investigate whether sequential or combined delivery of the AAV vector and the PFFs are equipotent in inducing stable neurodegeneration and behavioral deficits.

METHODS

Here we compare between four experimental paradigms (PFFs only, AAV-h-αSyn only, AAV-h-αSyn with simultaneous PFFs, and AAV-h-αSyn with sequential PFFs) and their respective GFP control groups.

RESULTS

We observed reduction of TH expression and loss of neurons in the midbrain in all AAV (h-αSyn or GFP) injected groups, with or without additional PFFs inoculation. The overexpression of either h-αSyn or GFP alone induced motor deficits and dysfunctional dopamine release/reuptake in electrochemical recordings in the ipsilateral striatum. However, we observed a substantial formation of insoluble h-αSyn aggregates and inflammatory response only when h-αSyn and PFFs were combined. Moreover, the presence of h-αSyn induced higher axonal pathology compared to control groups.

CONCLUSION

Simultaneous AAV and PFFs injections are equipotent in the presented experimental setup in inducing histopathological and behavioral changes. This model provides new and interesting possibilities for characterizing PD pathology in preclinical models and means to assess future therapeutic interventions.

Clinico-pathological comparison of patients with autopsy-confirmed Alzheimer's disease, dementia with Lewy bodies, and mixed pathology

INTRODUCTION

Patients with Alzheimer's disease (AD) and dementia with Lewy bodies (DLB) frequently demonstrate coexistent AD neuropathological change (ADNC) and Lewy body pathology (LBP) at autopsy. We investigated the effects of ADNC and LBP on the clinical presentation of these patients.

METHODS

We retrospectively compared clinical and pathological features of patients with different severity of ADNC and LBP. We also compared the burden of medullary LBP between patients with and without autonomic dysfunction.

RESULTS

Compared to pure ADNC, patients with AD/LBP have higher prevalence of DLB symptoms. Autonomic dysfunction strongly predicted the presence of LBP in patients with clinically diagnosed AD, but was not associated with increased LBP burden in the medulla. Severity of ADNC, but not LBP, was associated with cerebral atrophy.

DISCUSSION

Clinical presentation of patients with AD/LBP differs from patients with pure ADNC or LBP. Autonomic dysfunction is a useful marker of otherwise unsuspected LBP.

Alpha-synuclein seeds in olfactory mucosa and cerebrospinal fluid of patients with dementia with Lewy bodies

In patients with suspected dementia with Lewy bodies, the detection of the disease-associated α-synuclein in easily accessible tissues amenable to be collected using minimally invasive procedures remains a major diagnostic challenge. This approach has the potential to take advantage of modern molecular assays for the diagnosis of α-synucleinopathy and, in turn, to optimize the recruitment and selection of patients in clinical trials, using drugs directed at counteracting α-synuclein aggregation. In this study, we explored the diagnostic accuracy of α-synuclein real-time quaking-induced conversion assay by testing olfactory mucosa and CSF in patients with a clinical diagnosis of probable (n = 32) or prodromal (n = 5) dementia with Lewy bodies or mixed degenerative dementia (dementia with Lewy bodies/Alzheimer's disease) (n = 6). Thirty-eight patients with non-α-synuclein-related neurodegenerative and non-neurodegenerative disorders, including Alzheimer's disease (n = 10), sporadic Creutzfeldt-Jakob disease (n = 10), progressive supranuclear palsy (n = 8), corticobasal syndrome (n = 1), fronto-temporal dementia (n = 3) and other neurological conditions (n = 6) were also included, as controls. All 81 patients underwent olfactory swabbing while CSF was obtained in 48 participants. At the initial blinded screening of olfactory mucosa samples, 38 out of 81 resulted positive while CSF was positive in 19 samples out of 48 analysed. After unblinding of the results, 27 positive olfactory mucosa were assigned to patients with probable dementia with Lewy bodies, five with prodromal dementia with Lewy bodies and three to patients with mixed dementia, as opposed to three out 38 controls. Corresponding results of CSF testing disclosed 10 out 10 positive samples in patients with probable dementia with Lewy bodies and six out of six with mixed dementia, in addition to three out of 32 for controls. The accuracy among results of real-time quaking-induced conversion assays and clinical diagnoses was 86.4% in the case of olfactory mucosa and 93.8% for CSF. For the first time, we showed that α-synuclein real-time quaking-induced conversion assay detects α-synuclein aggregates in olfactory mucosa of patients with dementia with Lewy bodies and with mixed dementia. Additionally, we provided preliminary evidence that the combined testing of olfactory mucosa and CSF raised the concordance with clinical diagnosis potentially to 100%. Our results suggest that nasal swabbing might be considered as a first-line screening procedure in patients with a diagnosis of suspected dementia with Lewy bodies followed by CSF analysis, as a confirmatory test, when the result in the olfactory mucosa is incongruent with the initial clinical diagnosis.

Significant Overlap of α-Synuclein, Amyloid-β, and Phospho-Tau Pathologies in Neuropathological Diagnosis of Lewy-related Pathology: Evidence from China Human Brain Bank

BACKGROUND

Lewy-related pathology (LRP), primarily comprised of α-synuclein, is a typical neuropathological change that has been identified in many neurodegenerative disorders such as Parkinson's disease (PD), PD with dementia, and dementia with Lewy bodies.

OBJECTIVE

To investigate the distribution of LRP in the China Human Brain Bank, the co-occurrence of neuropathologic features of Alzheimer's disease (AD) in LRP cases, and LRP-related cognitive dysfunction.

METHODS

LRP neuropathological diagnosis was performed in 180 postmortem brains. AD neuropathological diagnosis was then performed in the 21 neuropathologically-diagnosed LRP cases. Antemortem cognitive functioning evaluation (Everyday Cognitive, ECog) was assessed for brain donors by the immediate kin of the donor within 24 hours after death.

RESULTS

12% (21 in 180) postmortem brains were neuropathologically diagnosed as LRP cases. 86% (18 in 21) aged above 80, 81% (17 in 21) LRP cases combined with AD neuropathology, and 62% (13 in 21) combined with both the intermediate or high-level amyloid-β and phospho-tau pathologies. ECog scores showed significant differences between the groups of LRP brainstem-predominant type and LRP diffuse neocortical type, and between groups of AD and the combined LRP (diffuse neocortical type)-AD.

CONCLUSION

The overlap of neocortical α-synuclein, amyloid-β, phospho-tau, and neuritic plaques in LRP suggested the potential interplay among the common characteristics of proteinopathies in the late stage of neuropathological development of LRP in human brains. The anatomic progression of LRP, the process of α-synuclein spreading from the brainstem to limbic and neocortical regions, might aggravate the deterioration of cognitive function in addition to that effect of AD.

Reverse engineering Lewy bodies: how far have we come and how far can we go?

Lewy bodies (LBs) are α-synuclein (α-syn)-rich intracellular inclusions that are an important pathological hallmark of Parkinson disease and several other neurodegenerative diseases. Increasing evidence suggests that the aggregation of α-syn has a central role in LB formation and is one of the key processes that drive neurodegeneration and pathology progression in Parkinson disease. However, little is known about the mechanisms underlying the formation of LBs, their biochemical composition and ultrastructural properties, how they evolve and spread with disease progression, and their role in neurodegeneration. In this Review, we discuss current knowledge of α-syn pathology, including the biochemical, structural and morphological features of LBs observed in different brain regions. We also review the most used cellular and animal models of α-syn aggregation and pathology spreading in relation to the extent to which they reproduce key features of authentic LBs. Finally, we provide important insights into molecular and cellular determinants of LB formation and spreading, and highlight the critical need for more detailed and systematic characterization of α-syn pathology, at both the biochemical and structural levels. This would advance our understanding of Parkinson disease and other neurodegenerative diseases and allow the development of more-reliable disease models and novel effective therapeutic strategies.

The combined effect of amyloid-β and tau biomarkers on brain atrophy in dementia with Lewy bodies

BACKGROUND

Alzheimer's disease (AD)-related pathology is frequently found in patients with dementia with Lewy bodies (DLB). However, it is unknown how amyloid-β and tau-related pathologies influence neurodegeneration in DLB. Understanding the mechanisms underlying brain atrophy in DLB can improve our knowledge about disease progression, differential diagnosis, drug development and testing of anti-amyloid and anti-tau therapies in DLB.

OBJECTIVES

We aimed at investigating the combined effect of CSF amyloid-β42, phosphorylated tau and total tau on regional brain atrophy in DLB in the European DLB (E-DLB) cohort.

METHODS

86 probable DLB patients from the E-DLB cohort with CSF and MRI data were included. Random forest was used to analyze the association of CSF biomarkers (predictors) with visual rating scales for medial temporal lobe atrophy (MTA), posterior atrophy (PA) and global cortical atrophy scale-frontal subscale (GCA-F) (outcomes), including age, sex, education and disease duration as extra predictors.

RESULTS

DLB patients with abnormal MTA scores had abnormal CSF Aβ42, shorter disease duration and older age. DLB patients with abnormal PA scores had abnormal levels of CSF Aβ42 and p-tau, older age, lower education and shorter disease duration. Abnormal GCA-F scores were associated with lower education, male sex, and older age, but not with any AD-related CSF biomarker.

CONCLUSIONS

This study shows preliminary data on the potential combined effect of amyloid-β and tau-related pathologies on the integrity of posterior brain cortices in DLB patients, whereas only amyloid-β seems to be related to MTA. Future availability of α-synuclein biomarkers will help us to understand the effect of α-synuclein and AD-related pathologies on brain integrity in DLB.

Case series of dementia with Lewy bodies: consensus criteria in practice

OBJECTIVES

This case series considers three patients newly diagnosed with dementia with Lewy bodies (DLB) whilst under the care of mental health services. The cases demonstrate that the difficulties in diagnosing DLB as early symptoms may resemble other neurodegenerative disorders or psychiatric illnesses.

CONCLUSION

The role of consensus criteria in diagnosis is explored. The use of screening and assessment tools in early identification of DLB is also considered.

Topography of cortical thinning in the Lewy body diseases

Objective

Regional cortical thinning in dementia with Lewy bodies (DLB) and Parkinson disease dementia (PDD) may underlie some aspect of their clinical impairments; cortical atrophy likely reflects extensive Lewy body pathology with alpha-synuclein deposits, as well as associated Alzheimer's disease co-pathologies, when present. Here we investigated the topographic distribution of cortical thinning in these Lewy body diseases compared to cognitively normal PD and healthy non-PD control subjects, explored the association of regional thinning with clinical features and evaluated the impact of amyloid deposition.

Methods

Twenty-one participants with dementia with Lewy bodies (DLB), 16 with Parkinson disease (PD) - associated cognitive impairment (PD-MCI and PDD), and 24 cognitively normal participants with PD underwent MRI, PiB PET, and clinical evaluation. Cortical thickness across the brain and in regions of interest (ROIs) was compared across diagnostic groups and across subgroups stratified by amyloid status, and was related to clinical and cognitive measures.

Results

DLB and PD-impaired groups shared a similar distribution of cortical thinning that included regions characteristic of AD, as well as the fusiform, precentral, and paracentral gyri. Elevated PiB retention in DLB and PD-impaired but not in PD-normal participants was associated with more extensive and severe cortical thinning, in an overlapping topography that selectively affected the medial temporal lobe in DLB participants. In DLB, greater thinning in AD signature and fusiform regions was associated with greater cognitive impairment.

Conclusions

The pattern of cortical thinning is similar in DLB and PD-associated cognitive impairment, overlapping with and extending beyond AD signature regions to involve fusiform, precentral, and paracentral regions. Cortical thinning in AD signature and fusiform regions in these diseases reflects cognitive impairment and is markedly accentuated by amyloid co-pathology. Further work will be required to determine whether the distinct topography of cortical thinning in DLB and PD-associated cognitive impairment might have value as a diagnostic and/ or outcome biomarker in clinical trials.

Cardiac sympathetic denervation and synucleinopathy in Alzheimer's disease with brain Lewy body disease

Comorbid Lewy body pathology is very common in Alzheimer’s disease and may confound clinical trial design, yet there is no in vivo test to identify patients with this. Tissue (and/or radioligand imaging) studies have shown cardiac sympathetic denervation in Parkinson’s disease and dementia with Lewy bodies, but this has not been explored in Alzheimer’s subjects with Lewy bodies not meeting dementia with Lewy bodies clinicopathological criteria. To determine if Alzheimer’s disease with Lewy bodies subjects show sympathetic cardiac denervation, we analysed epicardial and myocardial tissue from autopsy-confirmed cases using tyrosine hydroxylase and neurofilament immunostaining. Comparison of tyrosine hydroxylase fibre density in 19 subjects with Alzheimer’s disease/dementia with Lewy bodies, 20 Alzheimer’s disease with Lewy bodies, 12 Alzheimer’s disease subjects without Lewy body disease, 19 Parkinson’s disease, 30 incidental Lewy body disease and 22 cognitively normal without Alzheimer’s disease or Lewy body disease indicated a significant group difference (P < 0.01; Kruskal–Wallis analysis of variance) and subsequent pair-wise Mann–Whitney U tests showed that Parkinson’s disease (P < 0.05) and Alzheimer’s disease/dementia with Lewy bodies (P < 0.01) subjects, but not Alzheimer’s disease with Lewy bodies subjects, had significantly reduced tyrosine hydroxylase fibre density as compared with cognitively normal. Both Parkinson’s disease and Alzheimer’s disease/dementia with Lewy bodies subjects also showed significant epicardial losses of neurofilament protein-immunoreactive nerve fibre densities within the fibre bundles as compared with cognitively normal subjects (P < 0.01) and both groups showed high pathologic alpha-synuclein densities (P < 0.0001). Cardiac alpha-synuclein densities correlated significantly with brain alpha-synuclein (P < 0.001), while cardiac tyrosine hydroxylase and neurofilament immunoreactive nerve fibre densities were negatively correlated with the densities of both brain and cardiac alpha-synuclein, as well as Unified Parkinson’s Disease Rating Scale scores (P < 0.05). The clear separation of Alzheimer’s disease/dementia with Lewy bodies subjects from Alzheimer’s disease and cognitively normal, based on cardiac tyrosine hydroxylase fibre density, is the first report of a statistically significant difference between these groups. Our data do not show significant sympathetic cardiac denervation in Alzheimer’s disease with Lewy bodies, but strongly confirm that cardiac nuclear imaging with a noradrenergic radioligand is worthy of further study as a potential means to separate Alzheimer’s disease from Alzheimer’s disease/dementia with Lewy bodies during life.

Investigating the Association Between Verbal Forgetting and Pathological Markers of Alzheimer's and Lewy Body Diseases

BACKGROUND

The percentage of verbal forgetting (VF%) measure of the Rey Auditory Verbal Learning Test (RAVLT) has been proposed to differentiate patients diagnosed clinically with Alzheimer's disease (AD) and dementia with Lewy bodies (DLB).

OBJECTIVE

To determine if VF% aligns with gold-standard biomarker and autopsy evidence of AD and DLB neuropathology.

METHODS

Clinical, cognitive, sociodemographic, and biomarker data were collected from 315 patients with baseline cognitive impairment and 485 normal controls from the Alzheimer's Disease Neuroimaging Initiative (ADNI). AD markers included reduced cerebrospinal fluid (CSF) amyloid-β, elevated total-tau and phosphorylated-tau, hippocampal atrophy, and the presence of amyloid plaques and neurofibrillary tangles at autopsy. DLB markers included reduced CSF α-synuclein, preserved hippocampus, atrophied putamen, occipital glucose metabolism, and the presence of Lewy bodies at autopsy. Cognitively impaired participants were classified as ADVF% (n = 190) or DLBVF% (n = 125) based on their RAVLT VF% scores using a 75% cut-off (≥75%  = ADVF%, <75%  = DLBVF%). Postmortem data were available for 13 ADVF% participants, 13 DLBVF% patients, and six healthy controls.

RESULTS

ADVF% and DLBVF% participants did not differ on CSF or neuroimaging biomarkers, with the exception of total tau levels which were higher in ADVF%. In the subset of participants with autopsy data, comorbid AD and DLB pathology was most frequent in ADVF% participants, and pure DLB pathology was most frequent in DLBVF% participants, however, these differences were not statistically significant.

CONCLUSION

The RAVLT VF% measure does not reliably align with AD and DLB neuropathology in ADNI participants.

The genetics of dementia with Lewy bodies

Dementia with Lewy bodies (DLB), the most common non-AD neurodegenerative disease has in the past several decades attracted the attention of the neurological scientific community due to its highly negative impact on the quality of life of both the affected individuals and those caring for them. The strong hereditary component in related conditions such as PD and AD and the description of a number of DLB families suggest that genetic factors may play a role in the pathogenesis of DLB. This chapter focuses on currently proposed causal and risk genes and their role in the pathophysiology of DLB, discusses the feasibility of genetic therapy and genetic testing in the diagnostic and treatment of DLB and provides directions for future research. While no single mutation is specific enough to support its regular use in the diagnosis/treatment of DLB, identification of combinations of causative gene or single-gene point mutations and risk genes interfering with the pathogenesis of DLB may help elucidate the genetic mechanisms involved in DLB and inform development of gene-specific therapies.

Are we missing dementia with Lewy bodies?: a case report

OBJECTIVES

We aim to explore the importance of early diagnosis of dementia with Lewy bodies in order to facilitate effective psychiatric management. We present a case where delayed diagnosis stemming from an atypical presentation illustrates the complex issues involved in identifying and treating this type of dementia.

CONCLUSIONS

We discuss the difficulty of diagnosis of this disorder in the absence of obvious memory dysfunction or parkinsonian symptoms. We use the case to draw attention to the limited availability of certain investigations and treatment options in Australia.

Minor Hallucinations in Alzheimer's Disease

BACKGROUND

Hallucinations may have a broad spectrum and include so-called minor hallucinations (MHs). MHs include passage hallucinations (PHs), visual illusions, and presence hallucinations (PrHs).

OBJECTIVE

To determine the prevalence and characteristics of MHs in Alzheimer's disease (AD) and amnestic mild cognitive impairment (aMCI) patients, and to describe their potential relationship with cognition, behavioral symptoms, and use of psychoactive drugs.

METHODS

We have recruited prospectively and consecutively 268 subjects (90 AD mild-moderate drug-naïve patients, 78 aMCI, and 100 controls). All patients responded to a semi-structured questionnaire in order to rate psychotic phenomena. Clinical, neuropsychological, and demographic data of patients with and without MH were compared with those of age, sex, and education-matched controls.

RESULTS

The prevalence of MHs was 21.1% (19) in AD, 12.8% (10) in aMCI, and 3% (3) in controls (p < 0.01). The most frequent MH was PrH (9.3%), followed by PH (4.9%) and illusion (0.7%). Eight (27.8%) patients had more than one MH. After adjusting for age and gender, there was a negative correlation between the presence of MHs and MMSE score (r = -0.261; p < 0.01) and a positive correlation between MHs and Neuropsychiatric Inventory score (r = 0.237; p < 0.01). We did not observe a significant relationship between presence of MHs and the consumption of psychoactive drugs (p > 0.05).

CONCLUSION

We have shown that the presence of MHs in patients with newly diagnosed, untreated AD and aMCI is more than controls. MHs were correlated with other behavioral symptoms and a worse cognitive performance. We suggest the specific interrogation for MHs as a clinical feature for this population.

Quantitative electroencephalography as a marker of cognitive fluctuations in dementia with Lewy bodies and an aid to differential diagnosis

•

EEG slowing was evident in dementia with Lewy bodies (DLB) and Parkinson’s disease dementia (PDD) and less in Alzheimer’s disease (AD) patients compared to controls.

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Dominant rhythm variability was larger in AD but only correlated with cognitive fluctuations in DLB.

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QEEG variables classified DLB and AD patients with high sensitivity and specificity.

Objective

We investigated for quantitative EEG (QEEG) differences between Alzheimer’s disease (AD), dementia with Lewy bodies (DLB) and Parkinson’s disease dementia (PDD) patients and healthy controls, and for QEEG signatures of cognitive fluctuations (CFs) in DLB.

Methods

We analysed eyes-closed, resting state EEGs from 18 AD, 17 DLB and 17 PDD patients with mild dementia, and 21 age-matched controls. Measures included spectral power, dominant frequency (DF), frequency prevalence (FP), and temporal DF variability (DFV), within defined EEG frequency bands and cortical regions.

Results

DLB and PDD patients showed a leftward shift in the power spectrum and DF. AD patients showed greater DFV compared to the other groups. In DLB patients only, greater DFV and EEG slowing were correlated with CFs, measured by the clinician assessment of fluctuations (CAF) scale. The diagnostic accuracy of the QEEG measures was 94% (90.4–97.9%), with 92.26% (80.4–100%) sensitivity and 83.3% (73.6–93%) specificity.

Conclusion

Although greater DFV was only shown in the AD group, within the DLB group a positive DFV – CF correlation was found. QEEG measures could classify DLB and AD patients with high sensitivity and specificity.

Significance

The findings add to an expanding literature suggesting that EEG is a viable diagnostic and symptom biomarker in dementia, particularly DLB.

Are dementia with Lewy bodies and Parkinson's disease dementia the same disease?

BACKGROUND

Dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD), which share many clinical, neurochemical, and morphological features, have been incorporated into DSM-5 as two separate entities of major neurocognitive disorders with Lewy bodies. Despite clinical overlap, their diagnosis is based on an arbitrary distinction concerning the time of onset of motor and cognitive symptoms, namely as early cognitive impairment in DLB and later onset following that of motor symptoms in PDD. Their morphological hallmarks - cortical and subcortical α-synuclein/Lewy body plus β-amyloid and tau pathologies - are similar, but clinical differences at onset suggest some dissimilar profiles. Based on recent publications, including the fourth consensus report of the DLB Consortium, a critical overview is provided herein.

DISCUSSION

The clinical constellations of DLB and PDD include cognitive impairment, parkinsonism, visual hallucinations, and fluctuating attention. Intravitam PET and postmortem studies have revealed a more pronounced cortical atrophy, elevated cortical and limbic Lewy body pathologies, higher Aβ and tau loads in cortex and striatum in DLB compared to PDD, and earlier cognitive defects in DLB. Conversely, multitracer PET studies have shown no differences in cortical and striatal cholinergic and dopaminergic deficits. Clinical management of both DLB and PDD includes cholinesterase inhibitors and other pharmacologic and non-drug strategies, yet with only mild symptomatic effects. Currently, no disease-modifying therapies are available.

CONCLUSION

DLB and PDD are important dementia syndromes that overlap in many clinical features, genetics, neuropathology, and management. They are currently considered as subtypes of an α-synuclein-associated disease spectrum (Lewy body diseases), from incidental Lewy body disease and non-demented Parkinson's disease to PDD, DLB, and DLB with Alzheimer's disease at the most severe end. Cognitive impairment in these disorders is induced not only by α-synuclein-related neurodegeneration but by multiple regional pathological scores. Both DLB and PDD show heterogeneous pathology and neurochemistry, suggesting that they share important common underlying molecular pathogenesis with Alzheimer's disease and other proteinopathies. While we prefer to view DLB and PDD as extremes on a continuum, there remains a pressing need to more clearly differentiate these syndromes and to understand the synucleinopathy processes leading to either one.

Dementia with Lewy bodies and Parkinson's disease-dementia: current concepts and controversies

Dementia with Lewy bodies (DLB) and Parkinson's disease-dementia (PDD), although sharing many clinical, neurochemical and morphological features, according to DSM-5, are two entities of major neurocognitive disorders with Lewy bodies of unknown etiology. Despite considerable clinical overlap, their diagnosis is based on an arbitrary distinction between the time of onset of motor and cognitive symptoms: dementia often preceding parkinsonism in DLB and onset of cognitive impairment after onset of motor symptoms in PDD. Both are characterized morphologically by widespread cortical and subcortical α-synuclein/Lewy body plus β-amyloid and tau pathologies. Based on recent publications, including the fourth consensus report of the DLB Consortium, a critical overview is given. The clinical features of DLB and PDD include cognitive impairment, parkinsonism, visual hallucinations, and fluctuating attention. Intravitam PET and post-mortem studies revealed more pronounced cortical atrophy, elevated cortical and limbic Lewy pathologies (with APOE ε4), apart from higher prevalence of Alzheimer pathology in DLB than PDD. These changes may account for earlier onset and greater severity of cognitive defects in DLB, while multitracer PET studies showed no differences in cholinergic and dopaminergic deficits. DLB and PDD sharing genetic, neurochemical, and morphologic factors are likely to represent two subtypes of an α-synuclein-associated disease spectrum (Lewy body diseases), beginning with incidental Lewy body disease-PD-nondemented-PDD-DLB (no parkinsonism)-DLB with Alzheimer's disease (DLB-AD) at the most severe end, although DLB does not begin with PD/PDD and does not always progress to DLB-AD, while others consider them as the same disease. Both DLB and PDD show heterogeneous pathology and neurochemistry, suggesting that they share important common underlying molecular pathogenesis with AD and other proteinopathies. Cognitive impairment is not only induced by α-synuclein-caused neurodegeneration but by multiple regional pathological scores. Recent animal models and human post-mortem studies have provided important insights into the pathophysiology of DLB/PDD showing some differences, e.g., different spreading patterns of α-synuclein pathology, but the basic pathogenic mechanisms leading to the heterogeneity between both disorders deserve further elucidation. In view of the controversies about the nosology and pathogenesis of both syndromes, there remains a pressing need to differentiate them more clearly and to understand the processes leading these synucleinopathies to cause one disorder or the other. Clinical management of both disorders includes cholinesterase inhibitors, other pharmacologic and nonpharmacologic strategies, but these have only a mild symptomatic effect. Currently, no disease-modifying therapies are available.

The prevalence and characteristics of hallucinations, delusions and minor phenomena in a non-demented population sample aged 60 years and over

OBJECTIVE

Psychotic phenomena can occur in non-clinical subjects. The goals of this study were to assess the prevalence of delusions, hallucinations and minor 'psychotic' phenomena (visual illusions, feeling of presence and passage hallucinations) and to describe the characteristics of the latter in a non-clinical older population.

METHODS

Three hundred and thirteen individuals aged 60 years and older, without cognitive deficits (according to mini-mental state examination scores) or patent psychotic disease, answered a structured questionnaire focusing on delusions, hallucinations and minor phenomena that they had experienced in the previous month. The study sample was stratified by age and gender according to French demographic characteristics.

RESULTS

Twenty per cent of participants reported one or more psychotic phenomena. These subjects did not differ from those without psychotic symptoms as regards their age, mini-mental state examination scores or education. Minor phenomena were the most common (13%). Hallucinations, in any sensory modality, occurred in 9% of participants. No verbal auditory hallucinations or delusions were reported. The prevalence of minor phenomena increased with age and was associated with the use of psychoactive drugs.

CONCLUSION

By extending the spectrum of psychotic symptoms to minor phenomena, we found that psychotic symptoms were common in a non-clinical older population. Whether the increasing prevalence of minor phenomena with age is due to prodromal neurodegenerative disease or to other factors remains to be investigated. Copyright © 2016 John Wiley & Sons, Ltd.

Adequacy of Using Consensus Guidelines for Diagnosis of Dementia with Lewy Bodies in Clinical Trials for Drug Development

BACKGROUND/AIMS

To evaluate the adequacy of using the consensus diagnostic criteria for dementia with Lewy bodies (DLB) to recruit patients with homogeneous characteristics in future clinical trials, where multiple departments of multinational centres are expected to participate with a long enrolment period, and additionally, to contribute to the possible future criteria revision.

METHODS

Using data from 2 trials of donepezil for DLB, conducted 3 years apart, characteristics in patients with probable DLB were analysed and compared between studies and between psychiatric and neurological centres.

RESULTS

In 273 patients (phase II: 135, phase III: 138; psychiatric: 73, neurological: 184), clinical characteristics overall were very similar between studies, and between specialty centres, excluding distinctive parkinsonism in the neurological versus psychiatric centres: incidence of parkinsonism (91.8 vs. 71.2%, p < 0.001), Hoehn and Yahr stage (III: 55.0 vs. 21.2%, p < 0.001), and concomitant anti-Parkinson medication (24.5 vs. 11.0%, p = 0.017). Rapid eye movement sleep behaviour disorder, depression, and delusion, suggestive or supportive features, were observed in 35-40%. Additionally, a high prevalence (55.3%) of anxiety was observed.

CONCLUSION

Employing the consensus criteria is adequate to enrol homogeneous DLB patients into future clinical trials regardless of the specialty of centres and time. Further discussion could involve adding anxiety to future criteria.

Protein biomarkers in Parkinson's disease: Focus on cerebrospinal fluid markers and synaptic proteins

Despite extensive research, to date, no validated biomarkers for PD have been found. This review seeks to summarize studies approaching the detection of biomarker candidates for PD and introduce promising ones in more detail, with special attention to synaptic proteins. To this end, we performed a PubMed search and included studies using proteomic tools (2-dimensional difference in gel electrophoresis and/or mass spectrometry) for the comparison of samples from PD and control patients. We found 27 studies reporting more than 500 differentially expressed proteins in which a total of 28 were detected in 2 and 17 in 3 or more independent studies, including posttranslationally modified proteins. In addition, of these 500 proteins, 25 were found to be brain specific, and 14 were enriched in synapses. Special attention was given to the applicability of the biomarker regarding sampling procedures, that is, using CSF/serum material for diagnosis. Furthermore, presynaptic proteins involved in vesicle membrane fusion seem to be interesting candidates for future analyses. Nonetheless, even though such promising biomarker candidates for PD exist, validation of these biomarkers in large-scale clinical studies is necessary to evaluate the diagnostic potential. © 2016 International Parkinson and Movement Disorder Society.

Lewy Body Dementias: Dementia With Lewy Bodies and Parkinson Disease Dementia

PURPOSE OF REVIEW

This article provides an overview of the clinical features, neuropathologic findings, diagnostic criteria, and management of dementia with Lewy bodies (DLB) and Parkinson disease dementia (PDD), together known as the Lewy body dementias.

RECENT FINDINGS

DLB and PDD are common, clinically similar syndromes that share characteristic neuropathologic changes, including deposition of α-synuclein in Lewy bodies and neurites and loss of tegmental dopamine cell populations and basal forebrain cholinergic populations, often with a variable degree of coexisting Alzheimer pathology. The clinical constellations of DLB and PDD include progressive cognitive impairment associated with parkinsonism, visual hallucinations, and fluctuations of attention and wakefulness. Current clinical diagnostic criteria emphasize these features and also weigh evidence for dopamine cell loss measured with single-photon emission computed tomography (SPECT) imaging and for rapid eye movement (REM) sleep behavior disorder, a risk factor for the synucleinopathies. The timing of dementia relative to parkinsonism is the major clinical distinction between DLB and PDD, with dementia arising in the setting of well-established idiopathic Parkinson disease (after at least 1 year of motor symptoms) denoting PDD, while earlier cognitive impairment relative to parkinsonism denotes DLB. The distinction between these syndromes continues to be an active research question. Treatment for these illnesses remains symptomatic and relies on both pharmacologic and nonpharmacologic strategies.

SUMMARY

DLB and PDD are important and common dementia syndromes that overlap in their clinical features, neuropathology, and management. They are believed to exist on a spectrum of Lewy body disease, and some controversy persists in their differentiation. Given the need to optimize cognition, extrapyramidal function, and psychiatric health, management can be complex and should be systematic.

Evaluation of DSM-5 and IWG-2 criteria for the diagnosis of Alzheimer's disease and dementia with Lewy bodies

Despite differing target audiences and scope it is possible to compare the Fifth Edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) [American Psychiatric Association: Diagnostic and Statistical Manual of Mental Disorders, 5th ed. Arlington: American Psychiatric Association, 2013] and the Second International Working Group for New Research Criteria for the Diagnosis of Alzheimer's Disease (IWG-2) [Dubois B, Feldman HH, Jacova C, Hampel H, Molinuevo JL, Blennow K, et al. Advancing research diagnostic criteria for Alzheimer's disease: the IWG-2 criteria. Lancet Neurol 2014;13:614-29] diagnostic criteria for both Alzheimer's disease (AD) and dementia with Lewy bodies (DLB). With regard to the diagnosis of AD the principal difference is the inclusion of biomarkers in the IWG-2 diagnostic criteria for this condition. This creates a number of difficulties including a lack of regulatory approval, cultural and other objections to the collection of cerebrospinal fluid (CSF), and a lack of facilities for collection and analysis restricting analysis of CSF proteins to larger tertiary centres [Dubois B, Feldman HH, Jacova C, Hampel H, Molinuevo JL, Blennow K, et al. Advancing research diagnostic criteria for Alzheimer's disease: the IWG-2 criteria. Lancet Neurol 2014;13:614-29]. With regard to diagnostic criteria for DLB, IWG-2 research criteria designate the co-occurrence of AD and DLB as 'mixed AD'. However, Alzheimer's type pathology (ADTP) and Lewy body pathology frequently occur together rendering a separate 'mixed AD' category superfluous. The reality is that routine clinical diagnosis of AD and DLB will continue to be based on a thorough general and neurological examination indicating a preponderance of signs and symptoms for one or other of these conditions [Seeley WW, Miller BL. Alzheimer's disease and other dementias. In: Hauser SL, Josephson SA, editors. Harrison's neurology in clinical medicine, 3rd ed. New York: McGraw Hill, 2013]. Similarly, AD and DLB research will continue to primarily depend on clinically focussed DSM-5 criteria, making DSM-5 superior to IWG-2 in both clinical and research settings.

Dementia With Lew Body: Impacts of Surgery

Patients who have dementia with Lewy bodies (DLB) and undergo surgery may develop aggravated postoperative cognitive dysfunction or postoperative delirium. Many patients with DLB respond poorly to surgery and anesthesia, and their conditions may worsen if they have other medical complications along with dementia. They may also face high risk of prolonged hospital stay, increased medical problems and/or mortality, causing significant physical, psychosocial, and financial burdens on individuals, family members, and society. Anesthesia, pain medications, old age, and surgery-related stresses are usually held responsible for the complications; however, the exact causes are still not fully understood. Literature on surgery-related complications for patients with DLB appears to be inadequate, and hence the topic merits detailed and systematic research. This article reviews postoperative complications and various surgery-related risk factors for DLB in light of other dementias such as Alzheimer's disease, as their neuropathologic features overlap with those of DLB.

Accuracy of clinical diagnosis of Parkinson disease: A systematic review and meta-analysis

OBJECTIVE

To evaluate the diagnostic accuracy of clinical diagnosis of Parkinson disease (PD) reported in the last 25 years by a systematic review and meta-analysis.

METHODS

We searched for articles published between 1988 and August 2014. Studies were included if reporting diagnostic parameters regarding clinical diagnosis of PD or crude data. The selected studies were subclassified based on different study setting, type of test diagnosis, and gold standard. Bayesian meta-analyses of available data were performed.

RESULTS

We selected 20 studies, including 11 using pathologic examination as gold standard. Considering only these 11 studies, the pooled diagnostic accuracy was 80.6% (95% credible interval [CrI] 75.2%-85.3%). Accuracy was 73.8% (95% CrI 67.8%-79.6%) for clinical diagnosis performed mainly by nonexperts. Accuracy of clinical diagnosis performed by movement disorders experts rose from 79.6% (95% CrI 46%-95.1%) of initial assessment to 83.9% (95% CrI 69.7%-92.6%) of refined diagnosis after follow-up. Using UK Parkinson's Disease Society Brain Bank Research Center criteria, the pooled diagnostic accuracy was 82.7% (95% CrI 62.6%-93%).

CONCLUSION

The overall validity of clinical diagnosis of PD is not satisfying. The accuracy did not significantly improve in the last 25 years, particularly in the early stages of disease, where response to dopaminergic treatment is less defined and hallmarks of alternative diagnoses such as atypical parkinsonism may not have emerged. Misclassification rate should be considered to calculate the sample size both in observational studies and randomized controlled trials. Imaging and biomarkers are urgently needed to improve the accuracy of clinical diagnosis in vivo.

PET Radioligands Reveal the Basis of Dementia in Parkinson's Disease and Dementia with Lewy Bodies

BACKGROUND

Effective therapies for dementia with Lewy bodies (DLB) and Parkinson's disease (PD) dementia will require accurate diagnosis and an understanding of the contribution of distinct molecular pathologies to these diseases. We seek to use imaging biomarkers to improve diagnostic accuracy and to clarify the contribution of molecular species to cognitive impairment in DLB and PD.

SUMMARY

We have performed cross-sectional and prospective cohort studies in subjects with DLB, PD with normal cognition, PD with mild cognitive impairment and PD with dementia, contrasted with Alzheimer's disease (AD) and healthy control subjects (HCS). Subjects underwent formal neurological examination, detailed neuropsychological assessments, MRI and PET scans with the radioligands altropane (a dopamine transporter, DAT) and Pittsburgh compound B (PiB; β-amyloid). Putamen DAT concentrations were similar in DLB and PD and differentiated them from HCS and AD. Decreased caudate DAT concentration related to functional impairment in DLB but not PD. PiB uptake was greatest in DLB. However, cortical PiB retention was common in PD and predicted cognitive decline. PET imaging of tau aggregates holds promise both to clarify the contribution of tau to cognitive decline in these diseases and to differentiate DLB and PD from the parkinsonian tauopathies.

KEY MESSAGES

Together, DAT and amyloid PET imaging discriminate DLB from PD and from other disease groups and identify pathological processes that contribute to their course. Multimodal PET imaging has the potential to increase the diagnostic accuracy of DLB and PD in the clinic, improve cohort uniformity for clinical trials, and serve as biomarkers for targeted molecular therapies.

IMPROVING THE CLINICAL DETECTION OF LEWY BODY DEMENTIA WITH THE LEWY BODY COMPOSITE RISK SCORE

INTRODUCTION

Dementia with Lewy bodies (DLB) is a challenge to diagnose, particularly outside of expert centers with long delays in diagnosis leading to significant burden to patients and caregivers. While consensus criteria have excellent specificity, there is no standardized way to assess symptoms reducing sensitivity. We developed the Lewy Body Composite Risk Score (LBCRS) from autopsy-verified cases to improve the ability to detect DLB in clinic and research populations.

METHODS

The LBCRS was tested in a consecutive series of 256 patients compared with the Clinical Dementia Rating and gold standard measures of cognition, motor symptoms, function, and behavior. Psychometric properties including floor and ceiling effects; concurrent, construct, and known-groups validity, and internal consistency of the LBCRS were determined. Receiver operator characteristic (ROC) curves assessed the ability of LBCRS to differentiate: (a) DLB from Alzheimer's disease (AD); (b) DLB from all dementia, and (c) Mild cognitive impairment (MCI) due to DLB from MCI due to AD. The LBCRS was completed independent of the clinical evaluation.

RESULTS

Mean LBCRS scores were significantly different between DLB and AD (6.1±2.0 vs. 2.4±1.3, p<.001) and between MCI-DLB vs MCI-AD (3.2±0.9 vs. 1.0±0.8, p<.001). The LBCRS was able to discriminate DLB from other causes of dementia. Using a cut-off score of 3, areas under ROC for DLB vs. AD = 0.93 (0.89-0.98), and for MCI-DLB vs. MCI-AD = 0.96 (0.91-1.0).

DISCUSSION

The LBCRS increases diagnostic probability that Lewy body pathology is contributing to the dementia syndrome and should improve clinical detection and enrollment for clinical trials.

Pure psychiatric presentation of the Lewy body disease is depression--an analysis of 60 cases verified with myocardial meta-iodobenzylguanidine study

OBJECTIVE

Parkinson's disease (PD), Parkinson's disease with dementia (PDD) and dementia with Lewy bodies (DLB) were collectively termed Lewy body disease (LBD). Pure psychiatric presentation (PPP) of the LBD may be the fourth subtype in which psychiatric symptoms without definite parkinsonism and cognitive disturbance lasted for many years. The aim of this study is to localize the presence of the PPP in subjects with low uptake of myocardial meta-iodobenzylguanidine (MIBG).

METHODS

Sixty MIBG-verified patients (28 women and 32 men) were classified into three psychiatric pictures; depression (Group D: 27 patients), isolated visual hallucinations (Group V: 16 patients) and psychosis (Group P: 17 patients). Fifty six cases were examined with single photon emission tomography (SPECT) study of the brains in which hypoperfusion lobes were identified in 37 cases and 19 cases showed no abnormality. After that, we determined final diagnoses; PD, PDD, DLB and PPP with an aid of the DSM-IV, the unified Parkinson's disease rating scale (UPDRS) and Mini-mental state examination (MMSE).

RESULTS

Of Group D patients 40% remained depressive without parkinsonism and about 50% had or developed typical parkinsonism. Most Group P patients developed clinical pictures of PDD or DLB. Statistics provided four combinations: Group V-DLB-occipital lobe hypoperfusion, Group D-PD without SPECT abnormality, Group P-PDD with temporal lobe hypoperfusion and Group D-PPP without SPECT abnormality.

CONCLUSIONS

PPP featured major depressive disorder and can be preparative of incidental LBD and prodromal depression of PD. Psychosis and dementia were of the same quality that characterizes the PDD.

Clinicians' ability to diagnose dementia with Lewy bodies is not affected by β-amyloid load

OBJECTIVE

To investigate whether an increasing load of β-amyloid and/or neuritic plaques influences the phenotype, and thus the clinical diagnostic accuracy, of dementia with Lewy bodies (DLB).

METHODS

A series of 64 subjects with autopsy-proven DLB was studied. Last diagnosis before death was used to determine the clinical diagnostic accuracy of DLB in relation to Lewy body distribution and extent of Alzheimer β-amyloid and/or neuritic pathology. DLB pathologic diagnosis was made according to consensus criteria, using α-synuclein immunostaining for Lewy body identification. β-Amyloid immunostaining was used for quantifying β-amyloid deposits. The Consortium to Establish a Registry for Alzheimer's Disease criteria and Braak stage were applied for semiquantitative grading of neuritic plaque and neurofibrillary tangle pathology.

RESULTS

Overall clinical diagnostic accuracy for the entire DLB cohort was high (80%), reflecting the high prevalence of core clinical features (fluctuations [81%], parkinsonism [77%], visual hallucinations [70%]). Lower frequencies of core clinical features of DLB, resulting in lower accuracy of its clinical diagnosis, were associated with decreasing Lewy body distribution (p < 0.0001) and with increasing neuritic plaque pathology (p = 0.035), but not with the number of β-amyloid plaque deposits.

CONCLUSIONS

The likelihood of occurrence of the DLB clinical syndrome is positively related to the extent of Lewy body pathology and negatively related to the severity of Alzheimer neuritic pathology, while β-amyloid load has no effect.

Mutations in RAB39B cause X-linked intellectual disability and early-onset Parkinson disease with α-synuclein pathology

Advances in understanding the etiology of Parkinson disease have been driven by the identification of causative mutations in families. Genetic analysis of an Australian family with three males displaying clinical features of early-onset parkinsonism and intellectual disability identified a ∼45 kb deletion resulting in the complete loss of RAB39B. We subsequently identified a missense mutation (c.503C>A [p.Thr168Lys]) in RAB39B in an unrelated Wisconsin kindred affected by a similar clinical phenotype. In silico and in vitro studies demonstrated that the mutation destabilized the protein, consistent with loss of function. In vitro small-hairpin-RNA-mediated knockdown of Rab39b resulted in a reduction in the density of α-synuclein immunoreactive puncta in dendritic processes of cultured neurons. In addition, in multiple cell models, we demonstrated that knockdown of Rab39b was associated with reduced steady-state levels of α-synuclein. Post mortem studies demonstrated that loss of RAB39B resulted in pathologically confirmed Parkinson disease. There was extensive dopaminergic neuron loss in the substantia nigra and widespread classic Lewy body pathology. Additional pathological features included cortical Lewy bodies, brain iron accumulation, tau immunoreactivity, and axonal spheroids. Overall, we have shown that loss-of-function mutations in RAB39B cause intellectual disability and pathologically confirmed early-onset Parkinson disease. The loss of RAB39B results in dysregulation of α-synuclein homeostasis and a spectrum of neuropathological features that implicate RAB39B in the pathogenesis of Parkinson disease and potentially other neurodegenerative disorders.

"Is dopamine involved in Alzheimer's disease?"

Alzheimer's Disease (AD) is a neurodegenerative disorder characterized by progressive cognitive decline and dementia. Recent advances indicate that AD pathogenesis appears more complex than its mere neuropathology. Changes in synaptic plasticity, neuronal disarray and cell death are pathways commonly recognized as pathogenic mechanisms of AD. It is thought that the altered metabolism of certain membrane proteins may lead to the production of amyloid (Aβ) oligomers that are characterized by an highly toxic effect on neurotransmission pathways, such as those mediated by Acetylcholine. The interaction of Aβ oligomers with these neurotansmitters systems would in turn induce cell dysfunction, neurotransmitters signaling imbalance and finally lead to the appearance of neurological signs. In this perspective, it is still debated how and if these mechanisms may also engage the dopaminergic system in AD. Recent experimental work revealed that the dopaminergic system may well be involved in the occurrence of cognitive decline, often being predictive of rapidly progressive forms of AD. However, a clear idea on the role of the dopamine system in AD is still missing. Here we review the more recent evidences supporting the notion that the dopaminergic dysfunction has a pathogenic role in cognitive decline symptoms of AD.