Association of β-Amyloid and Basal Forebrain With Cortical Thickness and Cognition in Alzheimer and Lewy Body Disease Spectra

Objective:Cholinergic degeneration and β-amyloid contribute to brain atrophy and cognitive dysfunction in Alzheimer’s disease (AD) and Lewy body disease (LBD), but their relationship has not been comparatively evaluated.Methods:In this cross-sectional study, we recruited 28 normal controls (NC), 55 patients with AD mild cognitive impairment (MCI), 34 patients with AD dementia, 28 patients with LBD MCI, and 51 patients with LBD dementia. The subjects underwent cognitive evaluation, brain magnetic resonance imaging to measure the basal forebrain (BF) volume and global cortical thickness (CTh), and 18F-Florbetaben (FBB) positron emission tomography to measure the standardized uptake value ratio (SUVR). Using general linear models and path analyses, the association of FBB-SUVR and BF volume with the CTh and/or cognitive dysfunction were evaluated in AD spectrum (AD and NC) and LBD spectrum (LBD and NC), respectively. Covariates included age, sex, education, deep and periventricular white matter hyperintensities, intracranial volume, hypertension, diabetes mellitus, and hyperlipidemia.Results:BF volume mediated the association between FBB-SUVR and CTh both in AD and LBD spectra, while FBB-SUVR was associated with CTh independently of BF volume only in LBD spectrum. Significant correlation between voxel-wise FBB-SUVR and CTh was observed only in LBD group. FBB-SUVR was independently associated with widespread cognitive dysfunction both in AD and LBD spectra, especially in the memory domain [standardized beta (B) for AD spectrum = -0.60, B for LBD spectrum = -0.33]. In AD spectrum, BF volume was associated with memory dysfunction (B = 0.18), and CTh was associated with language (B = 0.21) and executive (B = 0.23) dysfunction. In LBD spectrum, however, BF volume and CTh were independently associated with widespread cognitive dysfunction.Conclusions:There is a common β-amyloid-related degenerative mechanism with or without the mediation of BF in AD and LBD spectra, while the association of BF atrophy with cognitive dysfunction is more profound and there is localized β-amyloid-cortical atrophy interaction in LBD spectrum.

Cerebrovascular disease associated with Parkinson’s disease in Moldovan cohort study

Background: Parkinson’s disease (PD) is frequently associated with brain vascular lesions (BVLs), which may influence the severity of the disease. Material and methods: BVLs on MRI were determined in 78.4% of 111 consecutive PD patients (mean age 64.87 ± 7.69 y.o.; disease duration 50.21 ± 38.61 mo.; 48 women (43.2%), 63 men (56.8%)). Results: White matter lesions were present in 73 patients (p.) (65.77%): 61p. (54.95%) – deep white matter, 46p. (41.44%) – periventricular white matter, and 41p. (36.94%) – both locations. Lacunas were determined in 19p. (17.12%), cerebral fissures deepening – 52p. (46.85) %), perivascular spaces dilation – 34p. (30.63%), ventricular system dilation – 29p. (26.13%). Patients with and without BVLs had similar ages, ages at PD onset and disease duration. They had insignificantly higher Beck (7.26 ± 5.62 vs 6.86 ± 4.34), PDQ39 (Parkinson’s Disease Questionnaire) (59.71 ± 20.38 vs 51.94 ± 27.69) and NMS (Non-Motor Symptoms) (75.06 ± 45.21 vs 71.67 ± 26.35) scores; and lower MoCA (Montreal Cognitive Assessment) scores (21.92 ± 4.25 vs 22.38 ± 4.57). QRISK3 scores (19.68 ± 16.16 vs 12.90 ± 6.58) and levodopa equivalent daily dose (639.98 ± 223.05 vs. 439.69 ± 404.87) were significantly higher in patients with BVLs. Conclusions: Brain vascular lesions were common in our PD patients, and were associated with higher QRISK3 scores and higher levodopa equivalent daily dose, suggesting more disease severity

State of intra- and extracranial arteries, white matter and cerebral cortex in asymptomatic hypertensive patients

Aim. To assess the state of intra- and extracranial arteries, white matter and cerebral cortex in asymptomatic hypertensive (HTN) patients according to multimodal examination.Material and methods. The study included data from 147 asymptomatic individuals (without prior ischemic stroke) with an established HTN (n=43; 29,3%) and without it. All participants underwent extracranial duplex ultrasound, transcranial duplex sonography, detection of middle cerebral artery microembolism, and brain magnetic resonance imaging. We performed a statistical analysis of the data obtained, adjusted for age and body mass index.Results. In patients with HTN, atherosclerotic plaques were more often detected — 37,2 vs 14,4% on the right (p=0,027) and 41,9 vs 13,5% on the left (p=0,001). In these patients, intima-media abnormalities and common carotid artery narrowing were also more common. Regional temporal lobe atrophy (p=0,044 on the right and p=0,046 on the left), central atrophy (p=0,045), focal periventricular white matter abnormalities (p=0,004) were more pronounced in hypertensive patients. There was no association between HTN and the presence of cerebral microbleeds, as well as the Montreal Cognitive Assessment (MoCA) score.Conclusion. In asymptomatic hypertensive patients relative to those without HTN, with comparable body mass index and age, head arterial abnormalities are more pronounced, but this regards only large ones — the common carotid artery. In these patients, more pronounced white matter and cerebral cortex changes were revealed.

Heterogeneity of Tau Deposition and Microvascular Involvement in MCI and AD

Background: Reduced cerebrovascular function and accumulation of tau pathology are key components of cognitive decline in Alzheimer’s disease (AD). Recent multimodal neuroimag- ing studies show a correlation between cortical tau accumulation and reduced cerebral perfusion. However, animal models predict that tau exerts capillary-level changes that may not be fully cap- tured by standard imaging protocols. Objective: Using newly-developed magnetic resonance imaging (MRI) technology to measure cap- illary-specific perfusion parameters, we examined a series of mild cognitive impairment (MCI) and AD patients with tau positron emission tomography (PET) to observe whole-brain capillary perfu- sion alterations and their association with tau deposition. Methods: Seven subjects with MCI or AD received Flortaucipir PET to measure tau deposition and spin-echo dynamic susceptibility contrast (SE-DSC) MRI to measure microvascular perfusion (<10μm radius vessels). Gradient-echo (GE) DSC and pseudocontinuous arterial spin labeling (P- CASL) MRI were also acquired to assess macrovascular perfusion. Tau PET, microvascular perfu- sion, and cortical thickness maps were visually inspected in volumetric slices and on cortical sur- face projections. Results: High tau PET signal was generally observed in the lateral temporal and parietal cortices, with uptake in the occipital cortex in one subject. Global blood flow measured by PCASL was re- duced with increasing tau burden, which was consistent with previous studies. Tau accumulation was spatially associated with variable patterns of microvascular cerebral blood flow (CBF) and oxy- gen extraction fraction (OEF) in the cortex and with increased capillary transit heterogeneity (C- TH) in adjacent periventricular white matter, independent of amyloid-β status. Conclusions: Although macrovascular perfusion generally correlated with tau deposition at the whole-cortex level, regional changes in microvascular perfusion were not uniformly associated with either tau pathology or cortical atrophy. This work highlights the heterogeneity of AD-related brain changes and the challenges of implementing therapeutic interventions to improve cerebrovas- cular function.

Lipopolysaccharide, Identified Using an Antibody and by PAS Staining, Is Associated With Corpora amylacea and White Matter Injury in Alzheimer's Disease and Aging Brain

Corpora amylacea (CA) increase in number and size with aging. Their origins and functions remain unknown. Previously, we found that Alzheimer's disease (AD) brains have more CA in the periventricular white matter (PVWM) compared to aging controls. In addition, CA is associated with neurodegeneration as indicated by colocalization of degraded myelin basic protein (dMBP) with periodic acid-Schiff (PAS), a CA marker. We also found that bacterial lipopolysaccharide is present in aging brains, with more LPS in AD compared with controls. Periodic acid-Schiff staining is used to identify CA by virtue of their high polysaccharide content. Despite the growing knowledge of CA as a contributor to AD pathology, the molecules that contribute to the polysaccharides in CA are not known. Notably, lipopolysaccharides (LPS) are important cell-surface polysaccharides found in all Gram-negative bacteria. However, it is unknown whether PAS could detect LPS, whether the LPS found in aging brains contribute to the polysaccharide found in CA, and whether LPS associate with myelin injury. In this study, we found that aging brains had a myelin deficit zone (MDZ) adjacent to the ventricles in PVWM. The MDZ contained vesicles, most of which were CA. LPS and dMBP levels were higher in AD than in control brains. LPS was colocalized with dMBP in the vesicles/CA, linking white matter injury with a bacterial pro-inflammatory molecule. The vesicles also contained oxidized fibers, C-reactive protein, NG2, and GALC, markers of oligodendrocyte precursor cells (OPCs) and oligodendrocyte cells (OLs), respectively. The vesicles/CA were surrounded by dense astrocyte processes in control and AD brains. LPS was co-localized with CA by double staining of PAS with LPS in aging brains. The relationship of LPS with PAS staining was confirmed by PAS staining of purified LPS on nitrocellulose membranes. These findings reveal that LPS is one of the polysaccharides found in CA which can be stained with PAS. In addition, vesicles/CA are associated with oxidized and damaged myelin. The LPS in these vesicles/CA may have contributed to this oxidative myelin damage and may have contributed to oxidative stress to OPCs and OLs which could impair the ability to repair damaged myelin in AD and control brains.

Microstructural Periventricular White Matter Injury in Post-Hemorrhagic Ventricular Dilatation

Background and Objectives:The neurological deficits of neonatal post-hemorrhagic hydrocephalus (PHH) have been linked to periventricular white matter injury. To improve understanding of PHH-related injury, diffusion basis spectrum imaging (DBSI) was applied in neonates, modeling axonal and myelin integrity, fiber density, and extra-fiber pathologies. Objectives included characterizing DBSI measures in periventricular tracts, associating measures with ventricular size, and examining MRI findings in the context of post-mortem white matter histology from similar cases.Methods:A prospective cohort of infants born very preterm underwent term equivalent MRI, including infants with PHH, high-grade intraventricular hemorrhage without hydrocephalus (IVH), and controls (VPT). DBSI metrics extracted from the corpus callosum, corticospinal tracts, and optic radiations included fiber axial diffusivity, fiber radial diffusivity, fiber fractional anisotropy, fiber fraction (fiber density), restricted fractions (cellular infiltration), and non-restricted fractions (vasogenic edema). Measures were compared across groups and correlated with ventricular size. Corpus callosum postmortem immunohistochemistry in infants with and without PHH assessed intra- and extra-fiber pathologies.Results:Ninety-five infants born very preterm were assessed (68 VPT, 15 IVH, 12 PHH). Infants with PHH had the most severe white matter abnormalities and there were no consistent differences in measures between IVH and VPT groups. Key tract-specific white matter injury patterns in PHH included reduced fiber fraction in the setting of axonal and/or myelin injury, increased cellular infiltration, vasogenic edema, and inflammation. Specifically, measures of axonal injury were highest in the corpus callosum; both axonal and myelin injury were observed in the corticospinal tracts; and axonal and myelin integrity were preserved in the setting of increased extra-fiber cellular infiltration and edema in the optic radiations. Increasing ventricular size correlated with worse DBSI metrics across groups. On histology, infants with PHH had high cellularity, variable cytoplasmic vacuolation, and low synaptophysin marker intensity.Discussion:PHH was associated with diffuse white matter injury, including tract-specific patterns of axonal and myelin injury, fiber loss, cellular infiltration, and inflammation. Larger ventricular size was associated with greater disruption. Postmortem immunohistochemistry confirmed MRI findings. These results demonstrate DBSI provides an innovative approach extending beyond conventional diffusion MRI for investigating neuropathological effects of PHH on neonatal brain development.

Diffusion Tensor Imaging Along the Perivascular Space Index in Different Stages of Parkinson’s Disease

Background: The aim of this study was to evaluate the glymphatic system activity in patients with Parkinson’s disease (PD) using the diffusion tensor image analysis along the perivascular space (DTI-ALPS) methods.Methods: In total, 71 patients with idiopathic PD and 36 age- and sex-matched normal controls (NCs) were involved. Patients with PD were divided into early (n = 35) and late (n = 36) subgroups, based on Hoehn and Yahr (HY) stages. We calculated the diffusivity along the perivascular spaces (ALPS), as well as projection fibers and association fibers separately, to acquire the ALPS index. Enlarged perivascular spaces (EPVS) and periventricular white matter hyperintensities were also rated. Differences in ALPS index between the PD group and NCs and between two PD subgroups and NCs were compared. In addition, a multivariate logistic regression analysis was conducted to investigate the association between ALPS index and clinical variables.Results: Patients with PD revealed lower ALPS index than NCs (p = 0.010). The late PD group exhibited significantly lower ALPS index than NCs (p = 0.006). However, there were no marked differences noticed in ALPS index between NCs and early PD group and between the two PD subgroups. In the early PD group, there was a significantly positive correlation between ALPS index and Mini-Mental State Examination (MMSE) score (β = 0.021, p = 0.029) and a negative correlation between ALPS index and EPVS score (β = −0.050, p = 0.034), after controlling for multiple variables. In the late PD group, ALPS index was inversely associated with age (β = −0.012, p = 0.004).Conclusion: Impairment of the glymphatic system is involved in PD. DTI-ALPS index could be a promising biomarker of glymphatic system in PD.

Peak ependymal cell stretch overlaps with the onset locations of periventricular white matter lesions

Deep and periventricular white matter hyperintensities (dWMH/pvWMH) are bright appearing white matter tissue lesions in T2-weighted fluid attenuated inversion recovery magnetic resonance images and are frequent observations in the aging human brain. While early stages of these white matter lesions are only weakly associated with cognitive impairment, their progressive growth is a strong indicator for long-term functional decline. DWMHs are typically associated with vascular degeneration in diffuse white matter locations; for pvWMHs, however, no unifying theory exists to explain their consistent onset around the horns of the lateral ventricles. We use patient imaging data to create anatomically accurate finite element models of the lateral ventricles, white and gray matter, and cerebrospinal fluid, as well as to reconstruct their WMH volumes. We simulated the mechanical loading of the ependymal cells forming the primary brain-fluid interface, the ventricular wall, and its surrounding tissues at peak ventricular pressure during the hemodynamic cycle. We observe that both the maximum principal tissue strain and the largest ependymal cell stretch consistently localize in the anterior and posterior horns. Our simulations show that ependymal cells experience a loading state that causes the ventricular wall to be stretched thin. Moreover, we show that maximum wall loading coincides with the pvWMH locations observed in our patient scans. These results warrant further analysis of white matter pathology in the periventricular zone that includes a mechanics-driven deterioration model for the ventricular wall.