There is increasing evidence for the role of central and peripheral inflammation across neurodegenerative disorders, with animal models and post-mortem studies identifying T-cell infiltration in the brain associated with pathology and neurodegeneration. Peripheral T-cell changes have been measured in Alzheimer’s disease (AD), dementia with Lewy bodies (DLB), frontotemporal dementia (FTD) and progressive supranuclear palsy (PSP). This study examines a unique cohort of blood-based T-cell profiles across a range of neurodegenerative dementias including AD, DLB, FTD, corticobasal syndrome (CBS), PSP, and aged-matched healthy controls. Then it also explores their associations with dementia-relevant plasma biomarkers and clinical outcomes. Freshly prepared peripheral blood mononuclear cells (PBMCs) from 174 participants (AD = 20, DLB = 24, FTD = 19, CBS = 18, PSP = 58, controls = 35) were studied using a flow-cytometry panel designed to analyse major T-cell subpopulations, including memory and T-helper subtypes. Neurodegeneration-relevant biomarkers (p-tau217, p-tau231, GFAP, NfL, and A-beta42/40) were measured in plasma samples. T-cell populations were compared between groups and in association with biomarkers, and principal components analysis (PCA) was used to identify T-cell profiles and their association with dementia-relevant biomarkers in diagnostic classification and survival prediction. There was a significant reduction in the fraction of CD3+ cells in patients with DLB compared to other diagnostic groups, and an increase in relative Th1/17-like cell levels in patients with FTD compared to controls. This increase in Th1/17-like cells correlated with NfL and GFAP plasma levels in patients with FTD. PCA identified five components primarily representing CD4+ memory cell population subsets. After sex and age adjustments, component 4 marked by effector memory types including Th2-like, Th-like1 and Th1/17-like cells was a significant predictor of FTD, however was not as accurate as plasma NfL. Higher scores in specific T-cell components (1 and 3) were associated with reduced mortality across all diseases, with component 3 remaining a significant predictor even when controlling for traditional neurodegenerative biomarkers like NfL and p-tau217. This study provides evidence that T-cell dysregulation is not unified in patients with neurodegenerative diseases. We observe different involvement across different dementia types establishing adaptive immunity as a key contributor to disease heterogeneity. However, although plasma biomarkers such as NfL and p-tau217 exhibit superior diagnostic accuracy for clinical classification, peripheral T-cell signature were associated with survival outcomes across diagnostic groups, highlighting their promise for prognostic applications and disease monitoring. The characterisation of T-cell populations across neurodegenerative conditions may inform target development and patient stratification for new interventional trials.

Abstract INTRODUCTION Dementia with Lewy bodies (DLB) or Parkinson's disease dementia (PDD), collectively termed Lewy body dementia (LBD), show heterogenous progression across cognitive, motor, and neuropsychiatric symptom domains, yet disease‐specific endpoints are lacking. We evaluated whether a composite clinical endpoint using validated scales across different symptom domains could sensitively track disease progression and align with functional and caregiver outcomes. METHODS One hundred sixteen participants (DLB = 72; PDD = 44) were assessed at baseline, 3, and 6 months in a cluster‐randomized trial comparing usual care versus management informed by an evidence‐based toolkit. The Lewy Body Symptom Severity (LBSS) index was constructed by summing rescaled Mini‐Mental State Examination, Movement Disorder Society Unified Parkinson's Disease Rating Scale (Part III), Dementia Cognitive Fluctuations Scale, and Neuropsychiatric Inventory 4‐item subscore (including hallucinations). Linear mixed‐effects models tested change over time. Validity was examined against caregiver Clinical Rating of Change (CRC), Bristol Activities of Daily Living (ADL) Scale, and caregiver Zarit Burden Interview. RESULTS Over 6 months, LBSS increased significantly (β = 0.0307; P = 0.0006). Simulation‐based power analyses indicated greater statistical efficiency for LBSS than for any individual component. LBSS also detected a significant intervention effect (P = 0.0365) not observed with single‐domain measures. LBSS correlated with caregiver burden (Zarit; ρ = 0.53, P < 0.001), functional dependence (Bristol ADL; ρ = 0.57, P < 0.001), and CRC (ρ = −0.33, P = 0.002), permitting derivation of a minimal clinically important difference. DISCUSSION A simple composite spanning cognition, parkinsonism, cognitive fluctuations, and neuropsychiatric symptoms sensitively detected short‐interval progression, with improved statistical efficiency over single‐domain measures, and was aligned with functional/caregiver outcomes. These findings support composite endpoints for LBD trials and can inform the design of disease‐specific scales.

Dementia with Lewy bodies (DLB) is the second most common cause of neurodegenerative dementia, pathologically defined by the presence of Lewy bodies. Peripheral and central inflammation are increasingly recognized in DLB in clinical, post-mortem and animal studies. Finding clinically relevant biomarkers of inflammation in DLB will support the identification of novel pathways for disease-modifying therapies or use in clinical trials of immunomodulatory agents. Whilst there are cross-sectional studies of inflammation markers in DLB, there is limited evidence on the association between these markers and cognitive decline over time. Twenty participants with DLB underwent blood sampling for serum inflammatory markers, paired with PET imaging of the translocator protein (TSPO) and up to 4 years of longitudinal cognitive testing. Thirty participants with Alzheimer's disease-comprising both Alzheimer's dementia and/or mild cognitive impairment with biomarker evidence of amyloid pathology (AD/MCI+)-and 28 controls were also recruited for group comparisons. Data from 42 baseline cytokine immunoassays and TSPO PET were used as predictors of longitudinal cognitive scores in linear mixed-effects models. Partial least squares regression was used to test the association between peripheral and central inflammation. Using peripheral inflammatory markers as single predictors, we identified 14 associated with either a slower or faster rate of cognitive decline in DLB, whilst no single marker was predictive of decline in AD/MCI+. As many inflammatory markers were highly correlated, we used principal component analysis to identify a cytokine component associated with reduced cognitive decline in both DLB and AD/MCI+, that overlapped with the single markers identified in the previous analysis. A separate component was associated with cognitive decline in AD/MCI+ or DLB with Alzheimer's dementia co-pathology (ascertained by amyloid PET). Widespread TSPO binding was associated with reduced cognitive decline in DLB, whilst a fronto-temporal pattern was associated with more rapid cognitive decline in both DLB and AD/MCI+. There were associations between peripheral cytokines and TSPO PET in AD/MCI+, but these were not significant in DLB. Overall, peripheral and central inflammation predicted cognitive decline in DLB. Specific patterns associated with both faster and slower rates of decline were identified. These profiles had both overlapping and contrasting associations when compared to AD/MCI+. Collectively, these data add to a body of evidence suggesting clinically relevant levels of inflammation in DLB. Future studies in larger, multi-site cohorts with multiple biomarker sampling points are required to understand the impact and dynamics of inflammation across all stages of the disease.

Brain inflammation is an important pathogenic mechanism in many dementias, occurring early in the disease and being predictive of clinical decline. However, data on blood markers of inflammation across different dementia subtypes are limited. Here we assess inflammatory patterns of serum cytokines from patients with Alzheimer’s disease (AD), Lewy-body dementia (DLB), frontotemporal dementia (FTD), progressive supranuclear palsy (PSP), corticobasal syndrome (CBS) and motor neurone disease (MND). Blood samples were obtained from 422 participants (29 controls, 46 patients with AD, 35 with mild cognitive impairment (MCI), 38 with DLB, 52 with behavioural variant FTD, 51 with primary progressive aphasia, 58 with PSP, 53 with CBS, 60 with MND. Serum assays for 41 inflammatory markers used the MesoScale Discovery V-Plex-Human Cytokine 36 plex panel plus five additional cytokine assays. A Principal Component Analysis (PCA) across all participants was used to identify leading multivariate components, or profiles, of inflammation. Analysis of variance and Bayesian pairwise t-tests were performed on the resulting components to compare each patient cohort to controls. Fifteen cytokines were undetectable in the majority (>50%) of participants and were thus excluded. The PCA of remaining 26 cytokines identified 3 components (explaining 18.3%, 8.5% and 6.4% variance, respectively). Component 1 was strongly represented by pro-inflammatory cytokines (Figure 1, left). Kruskal–Wallis one-way analyses of variance on the first component detected significant differences across the groups (χ 2 (8) = 24.3, p = 0.0021), and the Bayesian pairwise t-tests identified significant differences between each patient cohort and controls, except for people with MCI (Figure 1, right). Component 2 did not differ between patients and controls. Component 3 split the cytokines into two subgroups, and was mainly loaded by patients with MCI, AD and MND (χ 2 (8) = 64.6, p<0.0001). This data-driven approach identified similar profiles of pro-inflammatory responses across multiple neurodegenerative dementia types. Further analyses will clarify differences between diagnoses, relationships of the pro-inflammatory patterns with clinical severity and brain changes captured by neuroimaging (PET and MRI).

Dementia with Lewy bodies (DLB) is the second most common neurodegenerative cause of dementia, behind Alzheimer's disease (AD). The profile of inflammation in AD has been extensively researched in recent years, with evidence that chronic peripheral inflammation in midlife increases the risk of late-onset AD, and data supporting inflammation being associated with disease progression. In contrast, our understanding of the role of inflammation in DLB is less developed. Most research to date has examined inflammation in related disorders, such as Parkinson's disease, but there is now a growing range of literature examining inflammation in DLB itself. We present a review of the literature in this field, exploring a range of research methodologies including those quantifying markers of inflammation in cerebrospinal fluid, peripheral blood, post-mortem brain tissue, and using neuroimaging and preclinical data. Our review reveals evidence from PET imaging and peripheral blood analysis to support an increase in cerebral and peripheral inflammation in mild or prodromal DLB, that dissipates with disease progression. We present evidence from post-mortem brain tissue and pre-clinical studies that indicate α-synuclein directly promotes inflammation, but that also support the presence of AD co-pathology as an important factor in the profile of neuroinflammation in DLB. We propose that specific markers of inflammation may play a sentinel role in the mild stage of the disease, particularly when combined with AD pathology. We advocate further examination of the profile of inflammation in DLB through robust longitudinal studies, to enhance our understanding of the pathogenesis of the disease. The goal should be to utilise future results to develop a composite biomarker to aid diagnosis of DLB, and to potentially identify novel therapeutic targets.

Neuroinflammation is implicated in the pathogenesis of neurodegenerative disorders including dementia with Lewy bodies (DLB), but its relationship with disease progression, including cognitive decline, is less well understood. We investigated the predictive value of microglial activation, assessed in vivo using positron emission tomography (PET) imaging with [11C]PK11195, on the rate of annual cognitive decline in patients with DLB. We hypothesised a detrimental effect of inflammation on cognition over time.

ABSTRACTBackgroundLewy body dementia, comprising both dementia with Lewy bodies and Parkinson's disease dementia, is challenging to manage because of a complex symptom profile and lack of clear evidence‐based management guidelines.ObjectivesWe assessed the feasibility of undertaking a cluster randomized study of the introduction of an evidence‐based management toolkit for Lewy body dementia, assessing the outcomes for patients and carers as secondary measures.MethodsWe randomized 23 memory/dementia, movement disorder, or nonspecialist secondary care services to the management toolkit or usual care. People with dementia with Lewy bodies or Parkinson's disease dementia underwent assessments of cognition, motor and neuropsychiatric symptoms, and global outcome at baseline and 3 and 6 months. Healthcare, personal and social care costs, and carer‐related outcomes of carer stress, depression, and anxiety were also examined.ResultsA total of 131 participants were recruited (target 120), for whom 6‐month data were available on 108 (83%). There was a benefit of being in the intervention arm for carers (reduced Zarit Burden Scale [P < 0.01], reduced depressive symptoms [P < 0.05]), who also reported less marked patient deterioration on the global outcome measure (P < 0.05). There were no significant differences in other outcomes or in costs between groups.ConclusionsThe introduction of an evidence‐based management toolkit for Lewy body dementia was feasible and associated with some benefits, especially for carers. © 2020 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

The impairment of large-scale brain networks has been observed in dementia with Lewy bodies (DLB) using functional connectivity, but the potential for an analogous effect on structural covariance patterns has not been determined. Twenty-four probable DLB subjects (mean age 74.3 ± 6.7 years, 16.7% female) and 23 similarly aged Controls were included. All participants underwent 3T MRI imaging with high-resolution T1-weighted magnetization-prepared rapid gradient echo (MPRAGE) sequence. Graph theoretical analyses were performed using variation in regional cortical thickness to construct a structural association matrix with pairwise Pearson correlations. Global and nodal graph parameters were computed to assess between-group differences and community structure was studied in order to quantify large-scale brain networks in both groups. In comparison to Controls, DLB subjects had decreased global efficiency, clustering, modularity and small-worldness of structural networks (all p < 0.05). Nodal measures showed that DLB subjects also had decreased clustering in bilateral temporal regions and decreased closeness centrality in extensive areas including right middle frontal, left cingulate and bilateral occipital lobe (all false-discovery rate (FDR)-corrected q < 0.05). Whereas four distinct modules could be clearly identified in Controls, DLB showed extensively disorganized modules, including default-mode network and dorsal attentional network. Our results suggest a marked impairment in large-scale brain structural networks in DLB, mirroring functional connectivity networks disruption.

Background: Lewy body dementia, comprising both dementia with Lewy bodies and Parkinson’s disease dementia, is the second commonest cause of neurodegenerative dementia. Existing evidence suggests that it is underdiagnosed and without a consistent approach to management. Objectives: To improve the diagnosis and management of Lewy body dementia by (1) understanding current diagnostic practice for dementia with Lewy bodies and Parkinson’s disease dementia; (2) identifying barriers to and facilitators of diagnosis and management; (3) developing evidence-based assessment toolkits to improve diagnosis of dementia with Lewy bodies and Parkinson’s disease dementia; (4) producing a management toolkit to facilitate management; and (5) undertaking a pilot cluster randomised clinical trial. Design: Work package 1 assessed clinical diagnostic rates from case notes for dementia with Lewy bodies and Parkinson’s disease dementia before and after (work package 1 repeated) introduction of an assessment toolkit. In work package 2, we developed a management toolkit for Lewy body dementia. In work package 3, we developed assessment toolkits for dementia with Lewy bodies and Parkinson’s disease dementia and piloted these and the management toolkit in a clinical service. In work package 4, we undertook a pilot study of 23 services in nine NHS trusts that were cluster randomised to receiving and using the management toolkit or standard care. Work package 5 comprised a series of qualitative studies, examining barriers to and facilitators of diagnosis and management. Setting: Secondary care memory assessment and movement disorder services in England. Interventions: Assessment toolkits for Lewy body dementia consisted of questions for diagnostic symptoms, and management toolkits comprised 161 guidance statements grouped under five symptom domains. Review methods: The systematic reviews of pharmacological and non-pharmacological management were based on published literature, with meta-analysis when possible, following a search of several electronic databases and the grey literature using terms related to Lewy body dementia, without restriction on time or language. Participants: Participants aged ≥ 50 years diagnosed with dementia with Lewy bodies or Parkinson’s disease dementia and, for work package 1 and work package 1 repeated, non-dementia with Lewy bodies and non-Parkinson’s disease dementia controls. The qualitative studies included people with Lewy body dementia, carers and professionals. Main outcome measures: For work packages 1 and 1 repeated, diagnostic rates for dementia with Lewy bodies and Parkinson’s disease dementia as a proportion of all dementia or Parkinson’s disease. For work packages 2 and 3, the production of diagnostic and management toolkits. For work package 4, feasibility of undertaking a cluster randomised trial of the toolkits, measured by number of participants recruited and use of the toolkits, assessed qualitatively. Results: Work package 1 – 4.6% of dementia cases in secondary care received a dementia with Lewy bodies diagnosis (with significant differences in diagnostic rates between services) and 9.7% of those with Parkinson’s disease had a diagnosis of Parkinson’s disease dementia. There was evidence of delays in diagnosis for both dementia with Lewy bodies and Parkinson’s disease dementia compared with control patients, and the costs of dementia with Lewy bodies and Parkinson’s disease dementia were also greater than those for matched controls (p < 0.01 for both). Work package 2 – we produced 252 statements regarding Lewy body dementia management and, following a Delphi process, 161 statements were included in a management toolkit. Work package 3 – piloting indicated that separate assessment toolkits for use in memory clinic and movement disorder services were preferred, but a single toolkit for Lewy body dementia management was suitable. Work package 4 – we were able to recruit Lewy body dementia patients to target and recruited 131 patients within 6 months (target n = 120), of whom > 80% were retained in the study at 6 months. Work package 5 – barriers to diagnosis and management of Lewy body dementia were complex. Managing Lewy body dementia often requires input from a range of specialties and, therefore, care pathways may be fragmented. Positive attitudes to diagnosing Lewy body dementia, working with a team with expertise in Lewy body dementia and opportunities for cross-specialty discussion of patients with complex needs facilitated diagnosis and management. The toolkits were generally well received, particularly the management toolkit. Implementation, however, varied, reflecting differences in attitudes, skills, time and local leadership. Work package 1 repeated – following introduction of the assessment toolkit, we found that 9.7% of dementia cases had dementia with Lewy bodies (a significant increase from baseline; p = 0.0019), but Parkinson’s disease dementia rates were similar (8.2%) to baseline. Limitations: We included only two geographical regions and evidence informing the management toolkit was limited. Work package 4 was a pilot study and, therefore, we did not set out to assess the extent to which use of the management toolkit altered outcomes at the individual patient level. We noted implementation of the toolkits was variable. The increase in diagnostic rates in dementia with Lewy bodies following introduction of the assessment toolkits cannot be necessarily causally attributed to them. Conclusions: Dementia with Lewy bodies and Parkinson’s disease dementia were diagnosed in secondary care NHS services, with a lower frequency (around half) than that expected from known prevalence rates. The introduction of assessment toolkits for dementia with Lewy bodies and Parkinson’s disease dementia was associated with increased diagnostic rates of dementia with Lewy bodies, but not Parkinson’s disease dementia. Qualitative studies indicated inherent complexities of the disease itself, with treatment requiring input from different specialties and the potential for fragmented services, a workforce with variable training and confidence in Lewy body dementia, and negative attitudes towards diagnosis. The cluster randomised pilot trial demonstrated that patients could be successfully recruited, and provided preliminary evidence that the toolkits could be implemented in clinical services. Future work: The evidence base informing the management of Lewy body dementia is limited, especially for non-pharmacological interventions. More well-designed randomised controlled trials for both cognitive and non-cognitive symptoms are needed. Trial registration: Current Controlled Trials ISRCTN11083027. Funding: This project was funded by the National Institute for Health Research (NIHR) Programme Grants for Applied Research programme and will be published in full in Programme Grants for Applied Research; Vol. 9, No. 7. See the NIHR Journals Library website for further project information.

Background Dementia with Lewy bodies (DLB) and dementia in Parkinson’s disease (PDD) are recognised to be under-recognised in clinical practice in the UK, with only one third to a half of expected cases diagnosed. We aimed to assess whether clinical diagnostic rates could be increased by the introduction of a structured assessment toolkit for clinicians. Methods We established baseline diagnostic rates for DLB and PDD in four memory clinics and three movement disorder/Parkinson’s disease (PD) clinics in two separate geographical regions in the UK. An assessment toolkit specifically developed to assist with the recognition and diagnosis of DLB and PDD was then introduced to the same clinical teams and diagnostic rates for DLB and PDD were reassessed. For assessing DLB diagnosis, a total of 3820 case notes were reviewed before the introduction of the toolkit, and 2061 case notes reviewed after its introduction. For PDD diagnosis, a total of 1797 case notes were reviewed before the introduction of the toolkit and 3405 case notes after it. Mean values and proportions were analysed using Student’s t test for independent samples and χ 2 test, respectively. Results DLB was diagnosed in 4.6% of dementia cases prior to the introduction of the toolkit, and 6.2% of dementia cases afterwards, an absolute rise of 1.6%, equal to a 35% increase in the number of DLB cases diagnosed when using the toolkit ( χ 2 = 4.2, P = 0.041). The number of PD patients diagnosed with PDD was not found overall to be significantly different when using the toolkit: 9.6% of PD cases before and 8.2% of cases after its introduction ( χ 2 = 1.8, P = 0.18), though the ages of PD patients assessed after the toolkit’s introduction were lower (73.9 years vs 80.0 years, t = 19.2, p < 0.001). Conclusion Introduction of the assessment toolkit was associated with a significant increase in the rate of DLB diagnosis, suggesting that a structured means of assessing symptoms and clinical features associated with DLB can assist clinicians in recognising cases. The assessment toolkit did not alter the overall rate of PDD diagnosis, suggesting that alternate means may be required to improve the rate of diagnosis of dementia in Parkinson’s disease.

While [18F]-AV-1451 was developed as a PET radiotracer with high affinity for hyperphosphorylated tau, it has been proposed that loss of 'off-target' [18F]-AV-1451 binding to neuromelanin in the substantia nigra could be a surrogate marker of Lewy body diseases. [18F]-AV-1451 binding was measured in the substantia nigra of patients with Parkinson's disease (n = 35), dementia with Lewy bodies (n = 10) and separate control groups (n = 37; n = 14). Associations with motor symptoms, cognition and disease duration were evaluated using linear regression models. The dementia with Lewy bodies group had significantly reduced substantia nigra [18F]-AV-1451 binding compared to controls after adjusting for age (P < 0.05). However, there were no significant differences in substantia nigra [18F]-AV-1451 binding between Parkinson's disease and controls. Substantia nigra [18F]-AV-1451 binding was not associated with age, disease duration, Movement Disorders Society-Unified Parkinson's Disease Rating Scale and cognitive scores in dementia with Lewy bodies and Parkinson's disease groups. Despite the reduction of substantia nigra [18F]-AV-1451 binding in dementia with Lewy bodies, these findings suggest that substantia nigra [18F]-AV-1451 binding has no value as a diagnostic marker in early Parkinson's disease. Further investigations in longitudinal cohorts are warranted.

OBJECTIVE:This study aimed to quantify the trajectory and magnitude of change of the key clinical features and corresponding symptom domains of dementia with Lewy bodies (DLB) and Parkinson disease dementia (PDD), including global cognition, parkinsonism, recurrent visual hallucinations, cognitive fluctuations, and sleep disturbance.METHODS:One hundred sixteen patients with Lewy body dementia (DLB = 72, PDD = 44) underwent assessment at baseline and 3 and 6 months as part of a prospective multicenter randomized controlled trial. Linear mixed models were constructed for core outcome measures using the Mini-Mental State Examination (MMSE), motor section of the Unified Parkinson's Disease Rating Scale (UPDRS-III), Dementia Cognitive Fluctuations Scale (DCFS), and Neuropsychiatric Inventory (NPI).RESULTS:Within the time frame of our study (6 months), we were able to identify a significant cognitive decline of 1.3 points on the MMSE (p = 0.002) and significant worsening of motor parkinsonism with an increase in UPDRS-III score of 3.2 points (p = 0.018). Fluctuation severity also increased using the DCFS with a 6-month change in score of 1.3 points (p = 0.001). Uniquely, a signal for increased severity of sleep symptoms of 1.2 points (NPI-sleep) was also detectable (p = 0.04). Significant changes in neuropsychiatric symptoms were not detected. There was no difference in rates of change of scores between DLB and PDD.DISCUSSION:Clinically significant rates of change in core clinical features can be detected and quantified in Lewy body dementia over a relatively short period (6 months) using common clinical instruments and thus may be useful as clinical endpoints for therapeutic trials of disease-modifying and symptomatic agents.

In addition to beta-amyloid accumulation, misfolded tau and activated microglia are also present in Alzheimer's disease (AD). It is important to study the relationship amongst these pathologies in vivo and their effects on the cognitive deficits for developing effective trails and future therapeutic or preventive strategies for AD. To investigate the relationships amongst different pathologies in AD, in particular how they interact resulting in cognitive impairments, we conducted a study of sixty-six subjects (15 AD, 24 Mild Cognitive Impairment (MCI) and 27 similarly aged healthy controls), who underwent standardised clinical and neuropsychological assessments followed by dynamic PET using [F-18]AV1451 (tau) and [C-11]PK11195 (activated microglia) and multi modal 3T MRI. MCI patients also underwent [C-11]PIB (beta-amyloid) PET. We compared regional PET binding and grey matter atrophy amongst AD, amyloid positive MCI and controls, as well as their spatial distribution across different brain areas. We also applied a mediation analysis to infer the direct and indirect effects of tau, neuroinflammation and grey matter atrophy on cognitive functioning. We found increased [F-18]AV1451 and [C-11]PK11195 binding as well as grey matter atrophy in AD, with a strong spatial overlap amongst these AD related biomarkers suggesting them interacting with each other. We demonstrated that both tau ([F-18]AV1451) and neuroinflammation ([C-11]PK11195) have significant effects on cognition however their effects were fully mediated by grey matter atrophy. No mediation effect between tau and neuroinflammation were found with respect to cognition. In conclusion, grey matter atrophy not only spatially overlapped with tau and microglia activity in AD, but also mediate them in affecting cognitive impairments. The mediation analysis enabled data fusion across multiple imaging modalities (PET and MRI) and multiple PET tracers. Our results have significant implications for trials targeting tau and inflammation, and future therapeutic or preventive strategies for AD.

Alzheimer's disease (AD) pathology is frequently observed as a comorbidity in people with dementia with Lewy bodies (DLB). Here, we evaluated the in vivo distribution of tau burden and its influence on the clinical phenotype of DLB. Tau deposition was quantified using [18F]-AV1451 positron emission tomography in people with DLB (n = 10), AD (n = 27), and healthy controls (n = 14). A subset of patients with Lewy body diseases (n = 4) also underwent [11C]-PK11195 positron emission tomography to estimate microglial activation. [18F]-AV1451 BPND was lower in DLB than AD across widespread regions. The medial temporal lobe [18F]-AV1451 BPND distinguished people with DLB from AD (AUC = 0.87), and negatively correlated with Addenbrooke's Cognitive Examination-Revised and Mini-Mental State Examination. There was a high degree of colocalization between [18F]-AV1451 and [11C]-PK11195 binding (p < 0.001). Our findings of minimal tau burden in DLB confirm previous studies. Nevertheless, the associations of [18F]-AV1451 binding with cognitive impairment suggest that tau may interact synergistically with other pathologic processes to aggravate disease severity in DLB.

OBJECTIVES:Dementia with Lewy bodies (DLB) is a major cause of degenerative dementia, yet the diagnosis is often missed or mistaken for Alzheimer's disease (AD). We assessed whether the revised Addenbrooke's Cognitive Examination (ACE-R), a brief test for dementia, differentiates DLB from AD. METHODS:We first compared baseline ACE-R performance in 76 individuals with DLB, 40 individuals with AD and 66 healthy controls. We then investigated the diagnostic accuracy of a simple standardised 'memory/visuospatial' ratio calculated from the ACE-R subscores. Finally, as a comparison a logistic regression machine learning algorithm was trained to classify between DLB and AD. RESULTS:Individuals with AD had poorer memory (p = 0.001) and individuals with DLB had poorer visuospatial function (p = 0.005). Receiver operating characteristics curves confirmed that the ACE-R total score could differentiate dementia from non-dementia cases with 98% accuracy, but could not discriminate between dementia types (50%, or chance-level accuracy). However, a 'memory/visuospatial' ratio ≥1.1 differentiated DLB from AD with 82% sensitivity, 68% specificity and 77% mean accuracy. The machine learning classifier did not improve the overall diagnostic accuracy (74%) of the simple ACE-R subscores ratio. CONCLUSIONS:The ACE-R-based 'memory/visuospatial' ratio, but not total score, demonstrates good clinical utility for the differential diagnosis of DLB from AD.

ABSTRACTDementia with Lewy bodies (DLB) is the second-leading degenerative dementia after Alzheimer’s disase. Neuropathologically, it is characterized by alpha-synuclein protein deposition with variable degree of concurrent Alzheimer pathology. Neuroinflammation is increasingly recognized as a significant contributor of degeneration.Objectiveto examine the relationship between microglial activation as measured with [11C]-PK11195 brain PET and MR diffusion tensor imaging (DTI) in DLB.Methodsnineteen clinically probable DLB and 20 similarly aged controls underwent structural MRI with T1-weighted and 3T DTI sequences. Eighteen DLB subjects also underwent [11C]-PK11195 PET imaging. Tract-Based Spatial Statistics (TBSS) were performed to compare DTI parameters in DLB relative to controls and identify associations of [11C]-PK11195 binding with white matter integrity.ResultsTBSS showed widespread changes in all DTI parameters in the DLB group compared to controls (Threshold Free Cluster Enhancement (TFCE) p < 0.05). [11C]-PK11195 binding in parietal cortices also correlated with widespread lower mean and radial diffusivity (TFCE p < 0.05).ConclusionOur study demonstrates that higher PK11195 binding is associated with a relative preservation of white matter, positioning neuroinflammation as a potential early marker in the DLB pathogenic cascade.

Background Lewy body dementia, consisting of both dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD), is considerably under-recognised clinically compared with its frequency in autopsy series. Aims This study investigated the clinical diagnostic pathways of patients with Lewy body dementia to assess if difficulties in diagnosis may be contributing to these differences. Method We reviewed the medical notes of 74 people with DLB and 72 with non-DLB dementia matched for age, gender and cognitive performance, together with 38 people with PDD and 35 with Parkinson's disease, matched for age and gender, from two geographically distinct UK regions. Results The cases of individuals with DLB took longer to reach a final diagnosis (1.2 v. 0.6 years, P = 0.017), underwent more scans (1.7 v. 1.2, P = 0.002) and had more alternative prior diagnoses (0.8 v. 0.4, P = 0.002), than the cases of those with non-DLB dementia. Individuals diagnosed in one region of the UK had significantly more core features (2.1 v. 1.5, P = 0.007) than those in the other region, and were less likely to have dopamine transporter imaging (P < 0.001). For patients with PDD, more than 1.4 years prior to receiving a dementia diagnosis: 46% (12 of 26) had documented impaired activities of daily living because of cognitive impairment, 57% (16 of 28) had cognitive impairment in multiple domains, with 38% (6 of 16) having both, and 39% (9 of 23) already receiving anti-dementia drugs. Conclusions Our results show the pathway to diagnosis of DLB is longer and more complex than for non-DLB dementia. There were also marked differences between regions in the thresholds clinicians adopt for diagnosing DLB and also in the use of dopamine transporter imaging. For PDD, a diagnosis of dementia was delayed well beyond symptom onset and even treatment.