Cognitive Speed in Neurodegenerative Disease: Comparing Mean Rate and Inconsistency Within and Across the Alzheimer's and Lewy Body Spectra in the COMPASS-ND Study.

Background: Alzheimer's disease (AD) and Lewy body disease (LBD) are characterized by early and gradual worsening perturbations in speeded cognitive responses.

Objective: Using simple and choice reaction time tasks, we compared two indicators of cognitive speed within and across the AD and LBD spectra: mean rate (average reaction time across trials) and inconsistency (within person variability).

Methods: The AD spectrum cohorts included subjective cognitive impairment (SCI, n = 28), mild cognitive impairment (MCI, n = 121), and AD (n = 45) participants.

Quantifying cerebral microbleeds using quantitative susceptibility mapping from magnetization-prepared rapid gradient-echo.

T1-weighted magnetization-prepared rapid gradient-echo (MPRAGE) is commonly included in brain studies for structural imaging using magnitude images; however, its phase images can provide an opportunity to assess microbleed burden using quantitative susceptibility mapping (QSM). This potential application for MPRAGE-based QSM was evaluated using in vivo and simulated measurements. Possible factors affecting image quality were also explored.

Gray matter loss relates to dual task gait in Lewy body disorders and aging.

Background: Within the spectrum of Lewy body disorders (LBD), both Parkinson's disease (PD) and dementia with Lewy bodies (DLB) are characterized by gait and balance disturbances, which become more prominent under dual-task (DT) conditions. The brain substrates underlying DT gait variations, however, remain poorly understood in LBD.

Objective: To investigate the relationship between gray matter volume loss and DT gait variations in LBD.

Identifying key multi-modal predictors of incipient dementia in Parkinson's disease: a machine learning analysis and Tree SHAP interpretation.

Background: Persons with Parkinson's disease (PD) differentially progress to cognitive impairment and dementia. With a 3-year longitudinal sample of initially non-demented PD patients measured on multiple dementia risk factors, we demonstrate that machine learning classifier algorithms can be combined with explainable artificial intelligence methods to identify and interpret leading predictors that discriminate those who later converted to dementia from those who did not.

Method: Participants were 48 well-characterized PD patients ( = 71.

Brain iron content in cerebral amyloid angiopathy using quantitative susceptibility mapping.

Introduction: Cerebral amyloid angiopathy (CAA) is a small vessel disease that causes covert and symptomatic brain hemorrhaging. We hypothesized that persons with CAA would have increased brain iron content detectable by quantitative susceptibility mapping (QSM) on magnetic resonance imaging (MRI), and that higher iron content would be associated with worse cognition.

Methods: Participants with CAA ( = 21), mild Alzheimer's disease with dementia (AD-dementia; = 14), and normal controls (NC; = 83) underwent 3T MRI.

Subcortical volumes in cerebral amyloid angiopathy compared with Alzheimer's disease and controls.

Background: Previous reports have suggested that patients with cerebral amyloid angiopathy (CAA) may harbor smaller white matter, basal ganglia, and cerebellar volumes compared to age-matched healthy controls (HC) or patients with Alzheimer's disease (AD). We investigated whether CAA is associated with subcortical atrophy.

Methods: The study was based on the multi-site Functional Assessment of Vascular Reactivity cohort and included 78 probable CAA (diagnosed according to the Boston criteria v2.

Dementia Risk Prediction in a Longitudinal Geriatric Parkinson's Disease Cohort: Evaluation and Application of the Montreal Parkinson Risk of Dementia Scale.

Background: Parkinson's disease (PD) increases risk for dementia and cascading adverse outcomes. The eight-item Montreal Parkinson Risk of Dementia Scale (MoPaRDS) is a rapid, in-office dementia screening tool. We examine predictive validity and other characteristics of the MoPaRDS in a geriatric PD cohort by testing a series of alternative versions and modelling risk score change trajectories.

Quantitative Susceptibility Mapping Changes Relate to Gait Issues in Parkinson's Disease.

Background: Quantitative susceptibility mapping (QSM) demonstrates elevated iron content in Parkinson's disease (PD) patients within the basal ganglia, though it has infrequently been studied in relation to gait difficulties including freezing of gait (FOG). Our purpose was to relate QSM of basal ganglia and extra-basal ganglia structures with qualitative and quantitative gait measures in PD.

Methods: This case-control study included PD and cognitively unimpaired (CU) participants from the Comprehensive Assessment of Neurodegeneration and Dementia study.

Gait in Cerebral Amyloid Angiopathy.

Background Gait is a complex task requiring coordinated efforts of multiple brain networks. To date, there is little evidence on whether gait is altered in cerebral amyloid angiopathy (CAA). We aimed to identify impairments in gait performance and associations between gait impairment and neuroimaging markers of CAA, cognition, and falls.

Pedunculopontine Nucleus Dysconnectivity Correlates With Gait Impairment in Parkinson's Disease: An Exploratory Study.

Background: Gait impairment is a debilitating and progressive feature of Parkinson's disease (PD). Increasing evidence suggests that gait control is partly mediated by cholinergic signaling from the pedunculopontine nucleus (PPN).

Objective: We investigated whether PPN structural connectivity correlated with quantitative gait measures in PD.

Mediators of cognitive impairment in cerebral amyloid angiopathy.

Background: Cerebral amyloid angiopathy (CAA) is associated with cognitive decline. CAA has diverse impacts on brain structure and function; however, the brain lesions that mediate the association of CAA with cognition are not understood well.

Aims: To determine the degree to which CAA neuroimaging biomarkers mediate the association of CAA with cognitive dysfunction.

Diffusion tensor tractography of the fornix in cerebral amyloid angiopathy, mild cognitive impairment and Alzheimer's disease.

Purpose: Cerebral amyloid angiopathy (CAA) is a common neuropathological finding and clinical entity that occurs independently and with co-existent Alzheimer's disease (AD) and small vessel disease. We compared diffusion tensor imaging (DTI) metrics of the fornix, the primary efferent tract of the hippocampus between CAA, AD and Mild Cognitive Impairment (MCI) and healthy controls.

Methods: Sixty-eight healthy controls, 32 CAA, 21 AD, and 26 MCI patients were recruited at two centers.

Cerebrovascular Reactivity Across the Entire Brain in Cerebral Amyloid Angiopathy.

Background And Objectives: Reduced cerebrovascular reactivity is proposed to be a feature of cerebral amyloid angiopathy (CAA) but has not been measured directly. Employing a global vasodilatory stimulus (hypercapnia), this study assessed the relationships between cerebrovascular reactivity and MRI markers of CAA and cognitive function.

Methods: In a cross-sectional study, individuals with probable CAA, mild cognitive impairment, or dementia due to Alzheimer disease and healthy controls underwent neuropsychological testing and an MRI that included a 5% carbon dioxide challenge.

Association of Orthostatic Hypotension With Cerebral Atrophy in Patients With Lewy Body Disorders.

Objective: To evaluate whether orthostatic hypotension (OH) or supine hypertension (SH) is associated with brain atrophy and white matter hyperintensities (WMH), we analyzed clinical and radiologic data from a large multicenter consortium of patients with Parkinson disease (PD) and dementia with Lewy bodies (DLB).

Methods: Supine and orthostatic blood pressure (BP) and structural MRI data were extracted from patients with PD and DLB evaluated at 8 tertiary-referral centers in the United States, Canada, Italy, and Japan. OH was defined as a systolic/diastolic BP fall ≥20/10 mm Hg within 3 minutes of standing from the supine position (severe ≥30/15 mm Hg) and SH as a BP ≥140/90 mm Hg with normal sitting BP.

Cognitive and motor correlates of grey and white matter pathology in Parkinson's disease.

Introduction: Previous studies have found associations between grey matter atrophy and white matter hyperintensities (WMH) of vascular origin with cognitive and motor deficits in Parkinson's disease (PD). Here we investigate these relationships in a sample of PD patients and age-matched healthy controls.

Methods: Data included 50 PD patients and 45 age-matched controls with T1-weighted and FLAIR scans at baseline, 18-months, and 36-months follow-up.

Regional volumetric change in Parkinson's disease with cognitive decline.

Background: Parkinson's disease (PD), characterized by motor dysfunction and cognitive decline, may demonstrate specific patterns of brain atrophy. Although cross-sectional magnetic resonance imaging (MRI) studies show correlation between regional brain volume loss and cognitive impairment, there is only scarce evidence from longitudinal studies validating the link between cognition and brain anatomy in PD.

Objective: To test the relationship between magnitude and spatial extent of atrophy in PD patients with progressive, significant cognitive decline and dementia (PDD).

Freezing of gait in early Parkinson's disease: Nigral iron content estimated from magnetic resonance imaging.

Purpose: Freezing of gait is a major source of disability associated with the progression of Parkinson's disease (PD). Our objective was to determine whether evolving changes in nigral iron content in association with declining motor function in early PD differentiates subjects who develop freezing from those who do not.

Methods: A cohort of previously untreated individuals with early PD (n=19) was followed for 36 months clinically and with MRI.

Longitudinal midbrain changes in early Parkinson's disease: iron content estimated from R2*/MRI.

Objective: To determine whether, in patients with early Parkinson's disease (PD), longitudinal changes in midbrain iron content are associated with declining motor function over a period of three years.

Methods: Nineteen untreated subjects with early PD and 13 age- and sex-matched controls were followed clinically for 36 months. MRI with a 3 T magnet was performed at baseline, 18 months and 36 months with a multiple gradient echo sequence designed for rapid single-scan mapping of the proton transverse relaxation rate R2*.

Association of homocysteine with ventricular dilatation and brain atrophy in Parkinson's disease.

Parkinson's disease (PD) patients are treated with levodopa (L-dopa) to help stabilize their impaired motor abilities; however, L-dopa leads to increased homocysteine (Hcy) levels, which may have a deleterious effect on brain structure and function. The purpose of this study was to examine the impact of increased Hcy concentration on global brain atrophy as determined by magnetic resonance imaging in PD patients and controls. The effect of high Hcy level on ventricular dilatation (percentage of intracranial volume [%ICV]) and total tissue volume (%ICV) was examined at baseline and longitudinally at 36 months.

Intact limbic-prefrontal connections and reduced amygdala volumes in Parkinson's disease with mild depressive symptoms.

Background: Depression is very common in Parkinson's disease (PD). The neuropathological basis for this remains unclear; however, dysfunction in prefrontal and limbic regions may play a role.

Methods: We examined non-demented PD patients with and without depression and healthy controls (n = 6 per group) for differences in limbic structures and connections between these structures and the prefrontal cortex.

Ventricular dilatation and brain atrophy in patients with Parkinson's disease with incipient dementia.

Age-related ventricular enlargement is accelerated in Alzheimer's disease, but its relationship to cognitive decline in Parkinson's disease is less clear, even though dementia is common in Parkinson's disease. Our goals were to determine if greater enlargement of the ventricles and gray or white matter atrophy occurred in Parkinson's disease patients developing cognitive decline. Older nondemented patients with Parkinson's disease (33) and age- and sex-matched controls (39) were recruited and prospectively assessed for the development of significant cognitive decline over 36 months.

Corpus callosum and cingulum tractography in Parkinson's disease.

Background: In Parkinson's disease (PD) cell loss in the substantia nigra is known to result in motor symptoms; however widespread pathological changes occur and may be associated with non-motor symptoms such as cognitive impairment. Diffusion tensor imaging is a quantitative imaging method sensitive to the micro-structure of white matter tracts.

Objective: To measure fractional anisotropy (FA) and mean diffusivity (MD) values in the corpus callosum and cingulum pathways, defined by diffusion tensor tractography, in patients with PD, PD with dementia (PDD) and controls and to determine if these measures correlate with Mini-Mental Status Examination (MMSE) scores in parkinsonian patients.

Temporal lobe changes in early, untreated Parkinson's disease.

The purpose of this study was to determine if focal cortical abnormalities may occur in early Parkinson's disease (PD). We studied 26 untreated patients with early PD and 14 healthy control subjects, with cognitive screening and magnetic resonance imaging (MRI). Voxel-based morphometry was used to assess for the presence of localized cortical grey matter (GM) and/or subcortical white matter (WM) changes.