Dementia With Lewy Bodies: A Clinicopathologic Series of False-positive Cases

Substantia nigra hyperechogenicity and brain ventricular size as biomarkers of early dementia with Lewy bodies

BACKGROUND

Diagnosis of dementia with Lewy bodies (DLB) is challenging, especially in the earlier stages of the disease, owing to the clinical overlap with other neurodegenerative diseases such as Alzheimer's (AD) and Parkinson's disease (PD). We aimed to identify the transcranial sonography (TCS) parameters that can help us to detect early DLB patients.

METHODS

In this cross-sectional study, we prospectively recruited newly diagnosed DLB patients with less than 3 years from the onset of cognitive symptoms. For comparison purposes, we also included AD and PD patients, with a disease duration of less than 3 years, and a control group. TCS was performed to assess the substantia nigra (SN) echogenicity, the width of the third ventricle, and the frontal horns of the lateral ventricles. Subsequently, TCS images were analyzed with the medical image viewer Horos in order to quantify the intensity of the echogenicity of the SN. Univariate analysis and a logistic regression model were used to identify which variables can predict the diagnosis of DLB.

RESULTS

One hundred and seven participants were included (23 DLB, 26 AD, 27 PD and 31 controls). The median age of DLB patients was 75(72-77) years, with a disease duration of 2 years. DLB and PD patients showed higher SN hyperechogenicity rates (72.73% and 81.82%, respectively) and a greater area of the SN compared to AD patients and controls (p < 0.001). DLB and AD patients had wider ventricular systems than the other study groups. The SN hyperechogenicity predicted a diagnosis of DLB with an odds ratio of 22.67 (95%CI 3.98; 129.12, p < 0.001) when compared to AD patients. Unilateral and bilateral widened frontal horns predicted diagnosis of DLB compared to PD with an odds ratio of 9.5 (95%CI 0.97; 92.83, p = 0.053) and 5.7 (95%CI 0.97; 33.6, p = 0.054), respectively.

CONCLUSIONS

Echogenicity of the SN and widening of the frontal horns of lateral ventricles can predict the diagnosis of early DLB in this cohort of newly diagnosed patients, when compared to AD and PD patients. Transcranial sonography, a non-invasive tool, could be helpful for the diagnosis of DLB at its earlier stages.

A Systematic Review on the Evidence of Misdiagnosis in Dementia and Its Impact on Accessing Dementia Care

BACKGROUND

Whilst there is a drive to increase diagnosis rates in dementia, there is a lack of attention on getting a correct and timely subtype diagnosis. For people with a rarer subtype of dementia, getting the correct diagnosis, and subsequent care, might be more difficult than for people aged 65+ presenting with the more common symptoms of Alzheimer's disease dementia. Thus, the aim of this mixed-method systematic review was to synthesise the evidence base on misdiagnosis of dementia.

METHODS

Misdiagnosis in dementia was defined as either receiving an initial incorrect dementia subtype diagnosis or receiving an incorrect non-dementia diagnosis. Post-mortem assessments of subtype diagnosis were excluded. Nine databases were searched in June 2023, with screening of titles and abstracts and consequent full texts completed independently by two researchers. Findings were synthesised using narrative synthesis.

RESULTS

Twenty studies were included. Studies were categorised into four themes: (i) Factors associated with delayed diagnosis or misdiagnosis; (ii) Difficulties related to the diagnostic process; (iii) Economic consequences of misdiagnosis; and (iv) Experiences of delayed diagnosis or help-seeking. People with Lewy Body dementia or behavioural variant fronto-temporal dementia were found to experience longer diagnosis times and often incorrect initial diagnoses. Whilst evidence is limited regarding the economic impacts, evidence from the US points towards increased economic costs of misdiagnosis.

CONCLUSIONS

There is an urgent need to investigate the rates and emotional and economic impacts of misdiagnosis on people with dementia, their carers, and the health and social care system. Advancing the evidence base is crucial to reduce misdiagnosis and inform clinical practice.

Interpretation of Neurodegenerative GWAS Risk Alleles in Microglia and their Interplay with Other Cell Types

Microglia have been implicated in numerous neurodegenerative and neuroinflammatory disorders; however, the causal contribution of this immune cell type is frequently debated. Genetic studies offer a unique vantage point in that they infer causality over a secondary consequence. Genome-wide association studies (GWASs) have identified hundreds of loci in the genome that are associated with susceptibility to neurodegenerative disorders. GWAS studies implicate microglia in the pathogenesis of Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), and to a lesser degree suggest a role for microglia in vascular dementia (VaD), frontotemporal dementia (FTD), and amyotrophic lateral sclerosis (ALS), and other neurodegenerative and neuropsychiatric disorders. The contribution and function of GWAS risk loci on disease progression is an ongoing field of study, in which large genomic datasets, and an extensive framework of computational tools, have proven to be crucial. Several GWAS risk loci are shared between disorders, pointing towards common pleiotropic mechanisms. In this chapter, we introduce key concepts in GWAS and post-GWAS interpretation of neurodegenerative disorders, with a focus on GWAS risk genes implicated in microglia, their interplay with other cell types and shared convergence of GWAS risk loci on microglia.

Genetic insights into immune mechanisms of Alzheimer's and Parkinson's disease

Microglia, the macrophages of the brain, are vital for brain homeostasis and have been implicated in a broad range of brain disorders. Neuroinflammation has gained traction as a possible therapeutic target for neurodegeneration, however, the precise function of microglia in specific neurodegenerative disorders is an ongoing area of research. Genetic studies offer valuable insights into understanding causality, rather than merely observing a correlation. Genome-wide association studies (GWAS) have identified many genetic loci that are linked to susceptibility to neurodegenerative disorders. (Post)-GWAS studies have determined that microglia likely play an important role in the development of Alzheimer's disease (AD) and Parkinson's disease (PD). The process of understanding how individual GWAS risk loci affect microglia function and mediate susceptibility is complex. A rapidly growing number of publications with genomic datasets and computational tools have formulated new hypotheses that guide the biological interpretation of AD and PD genetic risk. In this review, we discuss the key concepts and challenges in the post-GWAS interpretation of AD and PD GWAS risk alleles. Post-GWAS challenges include the identification of target cell (sub)type(s), causal variants, and target genes. Crucially, the prediction of GWAS-identified disease-risk cell types, variants and genes require validation and functional testing to understand the biological consequences within the pathology of the disorders. Many AD and PD risk genes are highly pleiotropic and perform multiple important functions that might not be equally relevant for the mechanisms by which GWAS risk alleles exert their effect(s). Ultimately, many GWAS risk alleles exert their effect by changing microglia function, thereby altering the pathophysiology of these disorders, and hence, we believe that modelling this context is crucial for a deepened understanding of these disorders.

Novel Presenilin-1 Mutation (Ala275Ser) Associated With Clinical Features of Dementia With Lewy Bodies

We report a case of familial dementia having some clinical features characteristic of dementia with Lewy bodies, in which a novel mutation Ala275Ser within the presenilin-1 (PSEN1) gene was identified. We review the association of PSEN1 mutation with dementia with Lewy bodies features, noting this to be an uncommonly reported observation.

α-Synuclein RT-QuIC assay in cerebrospinal fluid of patients with dementia with Lewy bodies

We applied RT-QuIC assay to detect α-synuclein aggregates in cerebrospinal fluid (CSF) of patients with suspected Creutzfeldt-Jakob disease who had a neuropathological diagnosis of dementia with Lewy bodies (DLB) (n = 7), other neurodegenerative diseases with α-synuclein mixed pathology (n = 20), or without Lewy-related pathology (n = 49). The test had a sensitivity of 92.9% and specificity of 95.9% in distinguishing α-synucleinopathies from non-α-synucleinopathies. When performed in the CSF of patients with DLB (n = 36), RT-QuIC was positive in 17/20 with probable DLB, 0/6 with possible DLB, and 0/10 with Alzheimer disease. These results indicate that RT-QuIC for α-synuclein is an accurate test for DLB diagnosis.