Impairment In Dementia With Lewy Bodies Research Articles

Multidimensional assessment of social cognition using non-immersive virtual reality in dementia with Lewy bodies and Alzheimer’s disease: an exploratory study

ABSTRACT Introduction Few studies have focused on social cognition in dementia with Lewy bodies (DLB), even though some brain structures being well known as underlying social cognitive processes are directly impacted in this disease. Furthermore, social cognition processes have been mostly studied independently using evaluations with poor ecological validity. We aimed at studying the ability of a new naturalistic and multidimensional social cognition task to reveal impairments in DLB patients. We chose to compare the profile of these patients with that of Alzheimer’s disease (AD) patients, for which social cognition is better preserved. Method Fifteen patients (DLB: n = 7; AD: n = 8) and 28 healthy controls underwent the REALSoCog task. They encountered several social situations (e.g. control versus transgressions) in a non-immersive virtual city environment allowing the assessment of moral cognition, cognitive and affective theory of mind (ToM), emotional empathy and behavioral intentions. Results The main results showed (i) a lower ability to detect transgressions in DLB patients, particularly conventional ones, whereas moral cognition seemed better preserved in AD patients; (ii) a cognitive ToM impairment in both DLB and AD patients, while affective ToM is impaired only in DLB patients; (iii) a decreased emotional empathy specifically observed in DLB patients; (iv) more inappropriate behavioral intentions, mainly in DLB patients, but also in some AD patients. Conclusions This study suggests the feasibility and potential interest of the REALSoCog task in revealing social cognition deficits, particularly for DLB patients by showing different social patterns as compared to AD patients. These results offer interesting clinical perspectives to develop more naturalistic tasks in such populations and for clinical differential diagnosis. Limitations and future perspectives are discussed.

Diagnosis and Treatment of Cognitive and Neuropsychiatric Symptoms in Parkinson Disease and Dementia With Lewy Bodies.

This article summarizes the underlying biology and current diagnostic and treatment strategies for the cognitive and neuropsychiatric features of Parkinson disease (PD) and dementia with Lewy bodies (DLB). Cognitive impairment and neuropsychiatric symptoms have been increasingly recognized in PD and DLB, leading to improved diagnosis and treatment strategies. While PD is most associated with and diagnosed by the presence of motor symptoms, nonmotor symptoms can often be the most debilitating for patients. Neuropsychiatric symptoms are highly prevalent nonmotor features and include cognitive impairment, depression, anxiety, psychosis, impulse control disorders, and apathy. Neuropsychiatric symptoms can be difficult to recognize and diagnose in patients with PD, in part because of comorbidity and symptom overlap with core PD features. Treatment strategies are a combination of pharmacologic and nonpharmacologic interventions used in the general population and those specific to PD. DLB is a clinical dementia syndrome, often with similar cognitive, behavioral, autonomic, and motor features as PD. Moreover, DLB has shared underlying pathophysiology with PD, as both are associated with postmortem findings of α-synuclein neuropathology at autopsy and have shared genetic risk and prodromal symptoms. DLB is clinically differentiated from PD by the presenting features of cognitive impairment in DLB, compared with the variable onset of cognitive impairment occurring 1 year or more after established motor onset in PD. Thus, diagnosis and treatment of cognitive impairment and neuropsychiatric symptoms in DLB are similar to that of PD and have important implications for maintaining patient independence and providing support for caregivers because motor, cognitive, and neuropsychiatric symptoms have an additive effect on patient functional disability. A careful history and physical examination are often needed to accurately diagnose and treat the heterogeneous cognitive and behavioral symptoms of PD and DLB. Accurate diagnosis and treatment of neuropsychiatric symptoms and cognitive impairment in PD and DLB are important, as these are a considerable source of patient disability and caregiver burden.

Evidence-Based Evaluation and Management of Cognitive Impairment in Dementia With Lewy Bodies

Dementia is a functional decline due to cognitive impairment, and its presence is required to make a diagnosis of dementia with Lewy bodies (DLB). Evaluation and management of cognitive impairment in DLB is complex and requires consideration of cognitive fluctuations as well as motor and behavioral symptoms. This article reviews the literature surrounding evaluation and management of cognitive impairment in DLB, highlighting the specific cognitive profile typically seen in early DLB as well as the available evidence for management of these symptoms. There are several pharmacological and nonpharmacological treatment strategies that are currently under investigation, and these are reviewed as well. [ Psychiatr Ann. 2022;52(10):404–409.]

Neural basis of impaired narrative discourse comprehension in prodromal and mild dementia with lewy bodies.

Narrative discourse (ND) comprehension is a complex task that implies not only linguistic abilities but also other cognitive abilities, including efficient executive functioning. An executive dysfunction has been described in dementia with Lewy bodies (DLB) from the early stage. Here, we question the link between executive dysfunction in DLB and narrative comprehension. The aim of our study was to evaluate ND comprehension and to investigate the neuroanatomical basis for its impairment in the early stage of DLB. DLB patients (N = 26) and controls (N = 19) underwent the ND comprehension test of the Montreal Protocol for Evaluation of Communication (MEC). An additional, qualitative analysis was conducted on their verbal productions. Cognitive tests assessing verbal episodic memory, executive functions, naming and oral syntactic comprehension were also performed. Brain gray matter correlates of the ND comprehension test were examined using voxel-based morphometry (VBM). An ND comprehension impairment was found for prodromal and mild DLB patients as compared to controls. These difficulties were correlated with the Frontal Assessment Battery (FAB) score. ND comprehension impairment in DLB was further characterized by a deficit in the organization and the logic of the discourse. Moreover, VBM analysis revealed a correlation between striatal gray matter volumes and DLB patients’ ability to extract and organize relevant information (p < 0.05, FDR correction, cluster level). The ND comprehension impairment in DLB patients could be related to their executive dysfunction through a deficit of information selection and organization that correlates with the volumetric reduction of striatal gray matter.

An Adaptive Measure of Visuospatial Impairment in Dementia with Lewy Bodies.

ABSTRACTBackgroundDementia with Lewy bodies (DLB) is a common cause of dementia with poor prognosis and high hospitalization rates. DLB is frequently misdiagnosed, with clinical features that overlap significantly with other diseases including Parkinson's disease (PD). Clinical instruments that discriminate and track the progression of cognitive impairment in DLB are needed.ObjectivesThe current study was designed to assess the utility of a mental rotation (MR) task for assessing visuospatial impairments in early DLB.MethodsAccuracy of 22 DLB patients, 22 PD patients and 22 age‐matched healthy controls in the MR task were compared at comparing shapes with 0°, 45° and 90° rotations.ResultsHealthy controls and PD patients performed at similar levels while the DLB group were significantly impaired. Further, impairment in the visuospatial and executive function measures correlated with MR poor outcomes.ConclusionThese findings support the MR task as an objective measure of visuospatial impairment with the ability to adjust difficulty to suit impairments in a DLB population. This would be a useful tool within clinical trials.

Effects of Lanthionine Ketimine-5-Ethyl Ester on the α-Synucleinopathy Mouse Model.

Potentially druggable mechanisms underlying synaptic deficits seen in Parkinson's disease (PD) and dementia with Lewy bodies (DLB) are under intense interrogations. In addition to defective synaptic vesicle trafficking, cytoskeletal disruption, autophagic perturbation, and neuroinflammation, hyperphosphorylation of microtubule-associated protein collapsin response mediator protein 2 (CRMP2, also known as DPYSL2) is newly determined to correlate with synaptic deficits in human DLB. The small molecule experimental therapeutic, lanthionine ketimine-5-ethyl ester (LKE), appears to interact with CRMP2 in a host of neurodegenerative mouse models, normalizing its phosphorylation level while promoting healthful autophagy in cell culture models and suppressing the proinflammatory phenotype of activated microglia. Accordingly, this study examined the effect of LKE on α-synuclein A53T transgenic (Tg) mice which were employed as a DLB model. We found that chronic administration of LKE to A53T mice suppressed (1) the accumulation of LBs, (2) neuroinflammatory activation of microglia, (3) impairment of contextual fear memory, and (4) CRMP2 phosphorylation at Thr509 in A53T Tg mice. These results suggest that CRMP2 phosphorylation by GSK3β in the hippocampus is related to pathology and memory impairment in DLB, and LKE may have clinical implications in the treatment of α-synucleinopathy.

Comparisons of cardiovascular dysautonomia and cognitive impairment between de novo Parkinson\u2019s disease and de novo dementia with Lewy bodies

BackgroundCognitive impairment may be correlated with cardiovascular dysautonomia, including blood pressure (BP) dysregulation, in Parkinson’s disease (PD), but the association between these factors in dementia with Lewy bodies (DLB) is uncertain. This study aimed to clarify whether cardiovascular dysautonomia had an influence on cognitive function in Lewy body disease or not.MethodsNinty-nine patients with de novo PD (n = 75) and DLB (n = 24) were evaluated using the Mini-Mental State Examination (MMSE) and Frontal Assessment Battery (FAB). Cardiac 123I-metaiodobenzylguanidine (MIBG) scintigraphy, orthostatic hypotension (OH), supine hypertension (SH), postprandial hypotension (PPH), nocturnal BP fall in 24-h ambulatory blood pressure monitoring (ABPM) and constipation were estimated. Associations of these factors with cognitive and executive dysfunction were examined.ResultsIn DLB, MIBG uptake was reduced and OH, PPH and SH were severely disturbed, compared to PD. The nocturnal BP fall in ABPM was lower in DLB, and the failure of nocturnal BP fall in PD was associated with MMSE, after adjustment for other clinical features. FAB was significantly associated nocturnal BP fall, age and SH in PD, but no significant correlations among factors were found for DLB.ConclusionThe significant association between nocturnal BP dysregulation and cognitive or executive decline in PD might be due to impaired microvascular circulation or invasion of α-synuclein in the CNS. The lack of a correlation of BP insufficiency with cognitive impairment in DLB suggests initial involvement of Lewy body pathology in the neocortex, regardless of Lewy body invasion of the autonomic nervous system.

Improvement of Visuo-spatial Function Assessed by Raven's Colored Progressive Matrices in Dementia with Lewy Bodies by Donepezil Treatment.

ObjectiveDonepezil is used to improve cognitive impairment of dementia with Lewy bodies (DLB). Visuo-spatial dysfunction is a well-known symptom of DLB. Non-verbal Raven’s Colored Progressive Matrices (RCPM) were used to assess both visual perception and reasoning ability in DLB subjects treated with donepezil.MethodsTwenty-one DLB patients (mean age, 78.7±4.5 years) were enrolled. RCPM assessment was performed at the time of starting donepezil and within one year after starting donepezil.ResultsThere were significant improvements of RCPM in the total scores between one year donepezil treatment (p=0.013), in both Set A score (p=0.002) and Set AB score (p=0.015), but trend in the Set B score (p=0.083).ConclusionDonepezil is useful for improving visuo-spatial impairment in DLB, but not for problem-solving impairment.

Differences in responses to the Rorschach test between patients with dementia with Lewy bodies and Alzheimer's disease -from the perspective of visuoperceptual impairment

Patients with Dementia with Lewy bodies (DLB) tend to perform worse in tasks on visuoperception than patients with Alzheimer's disease (AD). The Rorschach inkblot test has its utility for assessing perceptual and visuospatial abilities. In this study, we examined the differences in responses to the Rorschach test between patients with DLB and those with AD in terms of visuoperception, and investigated the utility of the test for assessing visuoperceptual impairment in DLB. Using the comprehensive system of Rorschach test, six variables were significantly higher, and three variables were significantly lower in DLB patients compared to AD patients. Among those variables, PTI showed high sensitivity and specificity for differentiating DLB from AD. Furthermore, when the PTI score was combined with the Dd score and a number of times a patient saw an eye in a shading part of an inkblot, the sensitivity and specificity reached 90.6% and 73.1%, respectively. These results indicate that the patients with DLB perceive objects in the inkblot differently from patients with AD, and suggest that some variables of the Rorschach test could assist with neuropsychological examinations when differentiating DLB from AD.

COLOR VISION IMPAIRMENT IN DEMENTIA WITH LEWY BODIES: A NOVEL AND HIGHLY SPECIFIC DISTINGUISHING FEATURE FROM ALZHEIMER DEMENTIA

Dementia with Lewy Bodies (DLB) is frequently misdiagnosed for Alzheimer dementia (AD), especially in its earlier stages. Identification of clinical features that lend to accurate and earlier diagnosis remains paramount. We characterized the prevalence of color vision impairment (CVI) in DLB vs. AD patients and investigated how CVI is associated with other features of DLB. We retrospectively reviewed charts of patients with AD, DLB, and patients with mild cognitive impairment suspected to be in the prodromal phase of DLB (pro-DLB) or AD (pro-AD). All patients underwent an online 15-hue color vision arrangement test as part of the clinical assessment. The median age of the 47 included patients was 76 years and 47% were female. No significant differences in age or gender existed between patients with AD (n=14 patients) and pro-AD (n=6) versus pro-DLB (n=7) and DLB patients (n=20). Three patients (2 AD, 1 DLB) had CVI history from young age. New-onset CVI prevalence was: pro-AD patients (0%), AD patients (8%), pro-DLB patients (29%), and DLB patients (79%). CVI type was as follows: AD (1 protanopia), pro-DLB (2 deutanopia), DLB (10 protanopia, 3 deutanopia, and 2 tritanopia). The clinical signs and symptoms of patients with DLB were analyzed to evaluate factors associated with color vision impairment. In the 20 DLB patients, the symptom prevalence was: visual hallucinations (90%), tremor (80%), REM-behavior disorder (75%), postural instability (65%), bradykinesia (55%), rigidity (55%), and autonomic instability (50%). Normal mixtures iterative clustering analysis identified two DLB patient groups. While Cluster1 (n=10) and Cluster2 (n=8) had similar total number of Parkinsonian symptoms (2.4 vs. 2.0) and autonomic instability (50% vs. 38%), compared to Cluster2, Cluster1 patients were more likely to have CVI (100% vs. 50%), lower MOCA scores (14 vs. 19), lower visuospatial scores (1.4 vs. 2.5), and REM behavior disturbances (100% vs. 38%). Color vision impairment in DLB patients showed prevalence similar to the core features of DLB (∼80%) and was highly specific for DLB versus AD. Further larger scale investigation will determine if incorporation of color vision tests improve the accuracy of earlier diagnosis of DLB.

Hippocampal α-Synuclein in Dementia with Lewy Bodies Contributes to Memory Impairment and Is Consistent with Spread of Pathology.

Despite considerable research to uncover them, the anatomic and neuropathologic correlates of memory impairment in dementia with Lewy bodies (DLB) remain unclear. While some studies have implicated Lewy bodies in the neocortex, others have pointed to α-synuclein pathology in the hippocampus. We systematically examined hippocampal Lewy pathology and its distribution in hippocampal subfields in 95 clinically and neuropathologically characterized human cases of DLB, finding that α-synuclein pathology was highest in two hippocampal-related subregions: the CA2 subfield and the entorhinal cortex (EC). While the EC had numerous classic somatic Lewy bodies, CA2 contained mainly Lewy neurites in presumed axon terminals, suggesting the involvement of the EC → CA2 circuitry in the pathogenesis of DLB symptoms. Clinicopathological correlations with measures of verbal and visual memory supported a role for EC Lewy pathology, but not CA2, in causing these memory deficits. Lewy pathology in CA1-the main output region for CA2-correlated best with results from memory testing despite a milder pathology. This result indicates that CA1 may be more functionally relevant than CA2 in the context of memory impairment in DLB. These correlations remained significant after controlling for several factors, including concurrent Alzheimer's pathology (neuritic plaques and neurofibrillary tangles) and the interval between time of testing and time of death. Our data suggest that although hippocampal Lewy pathology in DLB is predominant in CA2 and EC, memory performance correlates most strongly with CA1 burden.SIGNIFICANCE STATEMENT This study provides a detailed neuropathologic analysis of hippocampal Lewy pathology in human patients with autopsy-confirmed dementia with Lewy bodies. The approach-informed by regional molecular markers, concurrent Alzheimer's pathology analysis, and relevant clinical data-helps tease out the relative contribution of Lewy pathology to memory dysfunction in the disease. Levels of Lewy pathology were found to be highest in the hippocampal CA2 subregion and entorhinal cortex, implicating a potentially overlooked circuit in disease pathogenesis. However, correlation with memory performance was strongest with CA1. This unexpected finding suggests that Lewy pathology must reach a critical burden across hippocampal circuitry to contribute to memory dysfunction beyond that related to other factors, notably coexisting Alzheimer's disease tau pathology.

Cerebrospinal Fluid Alzheimer's Disease Biomarkers Across the Spectrum of Lewy Body Diseases: Results from a Large Multicenter Cohort.

Concomitant Alzheimer's disease (AD) pathology is observed in Lewy body diseases (LBD), but the clinical impact is unknown. Only a few biomarker studies in LBD exist and have included small cohorts from single centers. We aimed to evaluate the prevalence of abnormal cerebrospinal fluid (CSF) AD biomarkers across the spectrum of LBD in a large multicenter cohort and to assess whether an AD biomarker profile was associated with demographic and clinical differences in dementia with Lewy bodies (DLB). We included 375 DLB patients, 164 Parkinson's disease (PD) patients without dementia, and 55 PD patients with dementia (PDD) from 10 centers. CSF amyloid-beta42 (Aβ42), total tau (t-tau), and phosphorylated tau (p-tau) values were dichotomized as abnormal or normal according to locally available cut-off values. A CSF AD profile was defined as abnormal Aβ42 combined with abnormal t-tau and/or p-tau. A substantial proportion of DLB patients had abnormal values for CSF Aβ42, t-tau, and p-tau, while abnormal values were uncommon in PD without dementia. Patients with PDD had values in between. A CSF AD profile was observed in 25% of DLB patients, compared with only 9% of PDD and 3% of PD without dementia. Within DLB, patients with a CSF AD profile were older, more often female, performed worse on the Mini-Mental State Examination, and had shorter disease duration compared with patients with normal CSF. A CSF AD profile is more common in DLB compared with PDD and PD, and is associated with more severe cognitive impairment in DLB.

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.

Visuoperceptual assessments for differentiating dementia with Lewy bodies and Alzheimer's disease: illusory contours and other neuropsychological examinations.

We examined the utility of illusory contours (ICs) for the differentiation of dementia with Lewy bodies (DLB) from Alzheimer's disease (AD). Thirty-five probable DLB patients, 35 probable AD patients controlled by age, years of education, and Mini-Mental State Examination (MMSE) score, and 30 cognitively normal subjects controlled by age and years of education underwent visuoperceptual examinations including ICs, pentagon copying in MMSE, overlapping figures, clock drawing test, cube copying, and line orientation. Four items in ICs (ICs-4) were found to be significantly impaired in DLB compared with AD, and a sensitivity and a specificity of total score of ICs-4 were 88.6% and 37.1%, respectively. When a score of ICs-4 is combined with a 10-point scaled score of pentagon copying in MMSE, a sensitivity and a specificity were 77.1% and 82.9%, respectively. The present study suggests that ICs-4 can be included in neuropsychological examinations to assess visuoperceptual impairment in DLB.

Striatal and extrastriatal dopamine transporter levels relate to cognition in Lewy body diseases: an (11)C altropane positron emission tomography study.

IntroductionThe biological basis of cognitive impairment in parkinsonian diseases is believed to be multifactorial. We investigated the contribution of dopamine deficiency to cognition in Parkinson disease (PD) and dementia with Lewy bodies (DLB) with dopamine transporter (DAT) imaging.MethodsWe acquired 11C altropane PET, magnetic resonance imaging and cognitive testing in 19 nondemented subjects with PD, 10 DLB and 17 healthy control subjects (HCS). We analyzed DAT concentration in putamen, caudate, anterior cingulate (AC), orbitofrontal and prefrontal regions, using the Standardized Uptake Volume Ratio with partial volume correction, and we related DAT concentration and global cortical thickness to neuropsychological performance.ResultsDAT concentration in putamen and in caudate were similar in PD and DLB groups and significantly lower than in HCS. Reduced caudate DAT concentration was associated with worse Clinical Dementia Rating Scale–sum of boxes (CDR-SB) scores and visuospatial skills in DLB but not in PD or HCS groups. Adjusting for putamen DAT concentration, as a measure of severity of motor disease, caudate DAT concentration was lower in DLB than in PD. Higher AC DAT concentration was associated with lower putamen DAT concentration in DLB and with higher putamen DAT concentration in PD. Higher AC DAT concentration in DLB correlated with greater impairment in semantic memory and language.ConclusionsCaudate and AC dopamine dysfunction contribute in opposing directions to cognitive impairment in DLB.

Testing Visual Perception in Dementia with Lewy Bodies and Alzheimer Disease

Visuoperceptual deficits are common in dementia with Lewy bodies (DLB) and Alzheimer disease (AD). Testing visuoperception in dementia is complicated by decline in other cognitive domains and extrapyramidal features. To overcome these issues, we developed a computerized test, the Newcastle visuoperception battery (NEVIP), which is independent of motor function and has minimal cognitive load.We aimed to test its utility to identify visuoperceptual deficits in people with dementia. We recruited 28 AD and 26 DLB participants with 35 comparison participants of similar age and education. The NEVIP was used to test angle, color, and form discrimination along with motion perception to obtain a composite visuoperception score. Those with DLB performed significantly worse than AD participants on the composite visuoperception score (Mann-Whitney U= 142, p= 0.01). Visuoperceptual deficits (defined as 2 SD below the performance of comparisons) were present in 71% of the DLB group and 40% of the AD group. Performance was not significantly correlated with motor impairment, but was significantly related to global cognitive impairment in DLB (rs=-0.689, p<0.001), but not in AD. Visuoperceptual deficits can be detected in both DLB and AD participants using the NEVIP, with the DLB group performing significantly worse than AD. Visuoperception scores obtained by the NEVIP are independent of participant motor deficits and participants are able to comprehend and perform the tasks.

Bed Rails—Be Vigilant, but Know the Rules and Guidelines

Visuoperceptual deficits are common in dementia with Lewy bodies (DLB) and Alzheimer disease (AD). Testing visuoperception in dementia is complicated by decline in other cognitive domains and extrapyramidal features. To overcome these issues, we developed a computerized test, the Newcastle visuoperception battery (NEVIP), which is independent of motor function and has minimal cognitive load.We aimed to test its utility to identify visuoperceptual deficits in people with dementia.We recruited 28 AD and 26 DLB participants with 35 comparison participants of similar age and education. The NEVIP was used to test angle, color, and form discrimination along with motion perception to obtain a composite visuoperception score.Those with DLB performed significantly worse than AD participants on the composite visuoperception score (Mann-Whitney U = 142, p = 0.01). Visuoperceptual deficits (defined as 2 SD below the performance of comparisons) were present in 71% of the DLB group and 40% of the AD group. Performance was not significantly correlated with motor impairment, but was significantly related to global cognitive impairment in DLB (rs = −0.689, p <0.001), but not in AD.Visuoperceptual deficits can be detected in both DLB and AD participants using the NEVIP, with the DLB group performing significantly worse than AD. Visuoperception scores obtained by the NEVIP are independent of participant motor deficits and participants are able to comprehend and perform the tasks.

Presynaptic α-Synuclein Aggregates, Not Lewy Bodies, Cause Neurodegeneration in Dementia with Lewy Bodies

Lewy bodies, the pathological hallmark of dementia with Lewy bodies (DLB), are large juxtanuclear inclusions of aggregated alpha-synuclein. However, the small number of cortical Lewy bodies relative to the total neuron count does not correlate with the extent of cognitive impairment. In contrast to dopaminergic neurons in Parkinson's disease, nerve cell loss is usually less prevalent in the cortex of DLB, suggesting a different mechanism of neurodegeneration. Because antibodies used for immunodetection per se do not generally differentiate the aggregated from the physiological and monomeric isoform of alpha-synuclein, we developed the paraffin-embedded tissue (PET) blot and the protein aggregate filtration (PAF) assay for the sensitive and selective detection of alpha-synuclein aggregates in tissue slides and brain homogenates, respectively. In contrast to common immunohistochemistry, the PET blot detected an enormous number of small alpha-synuclein aggregates, which, in contrast to the few Lewy bodies, may explain the cognitive impairment in DLB. Using the PAF assay, we demonstrate that the absolute majority of alpha-synuclein aggregates are located at presynaptic terminals, suggesting a severe pathological impact on synaptic function. Indeed, parallel to the massive presynaptic accumulation of alpha-synuclein aggregates, we observed significant synaptic pathology with almost complete loss of dendritic spines at the postsynaptic area. Our results provide strong evidence for a novel concept of neurodegeneration for DLB in which synaptic dysfunction is caused by presynaptic accumulation of alpha-synuclein aggregates. This concept may also be valid for Parkinson's disease.

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

The diagnosis of Parkinson's disease with dementia (PDD) or dementia with Lewy bodies (DLB) is based on an arbitary distinction between the time of onset of motor and cognitive symptoms. These syndromes share many neurobiological similarities, but there are also differences. Deposition of beta-amyloid protein is more marked and more closely related to cognitive impairment in DLB than PDD, possibly contributing to dementia at onset. The relatively more severe executive impairment in DLB than PDD may relate to the loss of frontohippocampal projections in DLB. Visual hallucinations and delusions associate with more abundant Lewy body pathology in temporal cortex in DLB. The differential involvement of pathology in the striatum may account for the differences in parkinsonism. Longitudinal studies with neuropathological and neurochemical evaluations will be essential to enable more robust comparisons and determine pathological substrates contributing to the differences in cognitive, motor, and psychiatric symptoms.

Accumulation of Insoluble α-Synuclein in Dementia with Lewy Bodies

The α-synuclein (αSN) protein is thought to play a central role in the pathogenesis of neurodegenerative diseases where it aggregates to form intracellular inclusions. We have used Western blotting to examine the expression levels and solubility of αSN in brain homogenates from dementia with Lewy bodies (DLB), Parkinson's disease (PD), Alzheimer's disease (AD), and normal controls using samples from the parahippocampus/transentorhinal cortex. Compared to controls, DLB brains accumulate significantly greater amounts of sodium dodecyl sulfate (SDS)-soluble and SDS-insoluble αSN but levels of TBS-soluble αSN did not change. Levels of synaptophysin, a marker of synaptic integrity, were significantly lower in DLB cases than in normal aged controls regardless of whether concurrent changes of AD were present. This limbic synaptic dysfunction may contribute to cognitive impairment in DLB. Whether aggregated αSN is a cause or effect of the disease process in DLB and PD remains to be determined, but the presence of aggregated αSN is consistent with a pathogenesis similar to that associated with aggregates of Aβ amyloid in AD.