Structural and Functional Magnetic Resonance Imaging of Dementia With Lewy Bodies

Brain Glucose Hypometabolism and Brain Iron Accumulation as Therapeutic Targets for Alzheimer's Disease and Other CNS Disorders

Two common mechanisms contributing to multiple neurological disorders, including Alzheimer's disease, are brain glucose hypometabolism (BGHM) and brain iron accumulation (BIA). Currently, BGHM and BIA are both widely acknowledged as biomarkers that aid in diagnosing CNS disorders, distinguishing between disorders with similar symptoms, and tracking disease progression. Therapeutics targeting BGHM and BIA in Alzheimer's disease can be beneficial in treating neurocognitive symptoms. This review addresses the evidence for the therapeutic potential of targeting BGHM and BIA in multiple CNS disorders. Intranasal insulin, which is anti-inflammatory and increases brain cell energy, and intranasal deferoxamine, which reduces oxidative damage and inflammation, represent promising treatments targeting these mechanisms. Both BGHM and BIA are promising therapeutic targets for AD and other CNS disorders.

A systematic review of diffusion tensor imaging and tractography in dementia with Lewy bodies and Parkinson's disease dementia

We reviewed studies using diffusion tensor imaging (DTI) and tractography to characterise white matter changes in Dementia with Lewy Bodies (DLB) and Parkinson's Disease Dementia (PDD). The search included MEDLINE and EMBASE, and we used a narrative strategy to synthesise the evidence. Data was extracted from 57 studies, of which the majority were considered 'good quality'. Subjects with DLB and PDD had widespread white matter changes compared to healthy controls and Parkinson's disease without cognitive impairment, with a relative sparing of the hippocampus. Compared to subjects with Alzheimer's disease (AD), DLB had greater changes in thalamic connectivity and in the nigroputaminal tract, while AD had greater changes in the parahippocampal white matter and fornix. Cognition was associated with widespread white matter changes, visual hallucinations with thalamic and cholinergic connectivity, and parkinsonism with changes in structures involved in motor control. DTI and tractography may therefore be well suited for discriminating DLB and PDD from other types of dementia, and for studying the aetiology of common symptoms.

Executive dysfunction in Parkinson's disease: From neurochemistry to circuits, genetics and neuroimaging

Cognitive decline is one of the most significant non-motor symptoms of Parkinson's disease (PD), with executive dysfunction (EDF) being the most prominent characteristic of PD-associated cognitive deficits. Currently, lack of uniformity in the conceptualization and assessment scales for executive functions impedes the early and accurate diagnosis of EDF in PD. The neurobiological mechanisms of EDF in PD remain poorly understood. Moreover, the treatment of cognitive impairment in PD has progressed slowly and with limited efficacy. Thus, this review explores the characteristics and potential mechanisms of EDF in PD from multiple perspectives, including the concept of executive function, commonly used neuropsychological tests, neurobiochemistry, genetics, electroencephalographic activity and neuroimaging. The available evidence indicates that degeneration of the frontal-striatal circuit, along with mutations in the Catechol-O-methyltransferase (COMT) gene and Leucine-rich repeat kinase 2 (LRRK2) gene, may contribute to EDF in patients with PD. The increase in theta and delta waves, along with the decrease in alpha waves, offers potential biomarkers for the early identification and monitoring of EDF, as well as the development of dementia in patients with PD. The PD cognition-related pattern (PDCP) pattern may serve as a tool for monitoring and assessing cognitive function progression in these patients and is anticipated to become a biomarker for cognitive disorders associated with PD. The aim is to provide new insights for the early and precise diagnosis and treatment of EDF in PD.

Separating dementia with Lewy bodies from Alzheimer's disease dementia using a volumetric MRI classifier

OBJECTIVES

Distinguishing dementia with Lewy bodies (DLB) from Alzheimer's disease (AD) dementia, particularly in patients with DLB and concomitant AD pathology (DLB/AD+), can be challenging and there is no specific MRI signature for DLB. The aim of this study is to examine the additional value of MRI-based brain volumetry in separating patients with DLB (AD+/-) from patients with AD and controls.

METHODS

We included 1518 participants from four cohorts (ADC, ADNI, PDBP and PredictND); 147 were patients with DLB (n = 76, DLB/AD+; n = 71, DLB/AD-), 668 patients with AD dementia, and 703 controls. We used an automatic segmentation tool to compute volumes of 70 brain regions, for which age, sex, and head size-dependent z-scores were calculated. We compared individual regions between the diagnostic groups and evaluated whether combining multiple regions improves differentiation. To assess the diagnostic performance, we used the area under the receiver operating characteristic curve (AUC) and sensitivity.

RESULTS

The classifier using the combination of 70 volumetric brain regions correctly classified 60% of patients with DLB and 70% of patients with AD dementia. For DLB vs. AD, the classifier produced an AUC of 0.80 (0.77-0.83), which outperformed the best individual region, hippocampus (AUC: 0.73 [0.69-0.76], p < 0.01). For the comparison of DLB/AD+ vs. AD, the classifier increased the AUC to 0.74 (0.68-0.80), which was 0.70 (0.64-0.76) for the hippocampus, p = 0.25.

CONCLUSION

Using a combination of volumetric brain regions improved the classification accuracy, and thus the discrimination, of patients with DLB with and without concomitant AD pathology and AD.

KEY POINTS

Question No specific MRI signature for dementia with Lewy bodies (DLB) exists, making the differential diagnosis challenging, especially with dementia due to Alzheimer's disease (AD). Findings Volumes of individual brain regions defined by automatic MRI segmentation differed between DLB and AD patients and controls. Clinical relevance Automatic MRI segmentation can contribute to improving the discrimination of patients with DLB and AD, especially in non-specialized memory clinics.

Markov model combined with MR diffusion tensor imaging for predicting the onset of Alzheimer's disease

Alzheimer's disease (AD) affects cognition, behavior, and memory of brain. It causes 60-80% of dementia cases. Cross-sectional imaging investigations of AD show that magnetic resonance (MR) with diffusion tensor image (DTI)-detected lesion locations in AD patients are heterogeneous and distributed across the imaging area. This study suggested that Markov model (MM) combined with MR-DTI (MM + MR-DTI) was offered as a method for predicting the onset of AD. In 120 subjects (normal controls [NCs], amnestic mild cognitive impairment [aMCI] patients, and AD patients) from a discovery dataset and 122 subjects (NCs, aMCI, and AD) from a replicated dataset, we used them to evaluate the white matter (WM) integrity and abnormalities. We did this by using automated fiber quantification, which allowed us to identify 20 central WM tracts. Point-wise alterations in WM tracts were shown using discovery and replication datasets. The statistical analysis revealed a substantial correlation between microstructural WM alterations and output in the patient groups and cognitive performance, suggesting that this may be a potential biomarker for AD. The MR-based classifier demonstrated the following performance levels for the basis classifiers, with DTI achieving the lowest performance. The following outcomes were seen in MM + MR-DTI using multimodal techniques when combining two modalities. Finally, a combination of every imaging method produced results with an accuracy of 98%, a specificity of 97%, and a sensitivity of 99%. In summary, DTI performs better when paired with structural MR, despite its relatively weak performance when used alone. These findings support the idea that WM modifications play a significant role in AD.

The Key Role of Magnetic Resonance Imaging in the Detection of Neurodegenerative Diseases-Associated Biomarkers: A Review

Neurodegenerative diseases (NDs), including chronic disease such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and multiple sclerosis, and acute diseases like traumatic brain injury and ischemic stroke are characterized by progressive degeneration, brain tissue damage and loss of neurons, accompanied by behavioral and cognitive dysfunctions. So far, there are no complete cures for NDs; thus, early and timely diagnoses are essential and beneficial to patients' treatment. Magnetic resonance imaging (MRI) has become one of the advanced medical imaging techniques widely used in the clinical examination of NDs due to its non-invasive diagnostic value. In this review, research published in English in current decade from PubMed electronic database on the use of MRI to detect specific biomarkers of NDs was collected, summarized, and discussed, which provides valuable suggestions for the early diagnosis, prevention, and treatment of NDs in the clinic.

Microstructural changes in prodromal dementia with Lewy bodies compared to normal aging: multiparametric quantitative MRI evidences

Dementia with Lewy bodies (DLB) patients show few significant macroscopic structural changes, especially at the early stages of the disease, making quantitative MRI especially interesting to explore more subtle changes that are not detectable by conventional volumetric techniques. Microstructural alterations have been reported in DLB at the dementia stage, but no study to date was conducted in prodromal patients. Here, quantitative MRI data were collected from 46 DLB prodromal patients and 20 healthy elderly subjects, who also underwent a detailed clinical examination including the Mayo Clinic Fluctuation Scale. We conducted voxel-wise between-group comparisons in diffusion tensor imaging (DTI) metrics and in R2* mapping, along with a multivariate analysis combining the two modalities. We highlighted multiple grey matter and white matter microstructural changes in DLB patients at the prodromal stage, compared to control subjects. Our multivariate analysis identified three distinct regional patterns of DTI and R2* changes (anterior, anteromedial, posterior) in DLB patients, that could reflect different neuropathological processes across brain regions. We also observed an association between R2* alterations in the thalamus, and the severity of fluctuations, in the DLB group. These preliminary findings are promising and require future investigations to better understand the biological underpinnings of microstructural alterations.

Lewy Body Dementias: A Coin with Two Sides?

Lewy body dementias (LBDs) consist of dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD), which are clinically similar syndromes that share neuropathological findings with widespread cortical Lewy body deposition, often with a variable degree of concomitant Alzheimer pathology. The objective of this article is to provide an overview of the neuropathological and clinical features, current diagnostic criteria, biomarkers, and management of LBD. Literature research was performed using the PubMed database, and the most pertinent articles were read and are discussed in this paper. The diagnostic criteria for DLB have recently been updated, with the addition of indicative and supportive biomarker information. The time interval of dementia onset relative to parkinsonism remains the major distinction between DLB and PDD, underpinning controversy about whether they are the same illness in a different spectrum of the disease or two separate neurodegenerative disorders. The treatment for LBD is only symptomatic, but the expected progression and prognosis differ between the two entities. Diagnosis in prodromal stages should be of the utmost importance, because implementing early treatment might change the course of the illness if disease-modifying therapies are developed in the future. Thus, the identification of novel biomarkers constitutes an area of active research, with a special focus on α-synuclein markers.

Differentiating dementia with Lewy bodies from Alzheimer's disease and Parkinson's disease dementia: an update on imaging modalities

Dementia with Lewy bodies is the second most common cause of neurodegenerative dementia after Alzheimer's disease. Dementia with Lewy bodies can provide a diagnostic challenge due to the frequent overlap of clinical signs with other neurodegenerative conditions, namely Parkinson's disease dementia, and Alzheimer's disease. Part of this clinical overlap is due to the neuropathological overlap. Dementia with Lewy bodies is characterized by the accumulation of aggregated α-synuclein protein in Lewy bodies, similar to Parkinson's disease and Parkinson's disease dementia. However, it is also frequently accompanied by aggregation of amyloid-beta and tau, the pathological hallmarks of Alzheimer's disease. Neuroimaging is central to the diagnostic process. This review is an overview of both established and evolving imaging methods that can improve diagnostic accuracy and improve management of this disorder.