Seun Jeon

Anatomical heterogeneity of Alzheimer disease Based on cortical thickness on MRIs

Objective: Because the signs associated with dementia due to Alzheimer disease (AD) can be heterogeneous, the goal of this study was to use 3-dimensional MRI to examine the various patterns of cortical atrophy that can be associated with dementia of AD type, and to investigate whether AD dementia can be categorized into anatomical subtypes. Methods: High-resolution T1-weighted volumetric MRIs were taken of 152 patients in their earlier stages of AD dementia. The images were processed to measure cortical thickness, and hierarchical agglomerative cluster analysis was performed using Wards clustering linkage. The identified clusters of patients were compared with an age- and sex-matched control group using a general linear model. Results: There were several distinct patterns of cortical atrophy and the number of patterns varied according to the level of cluster analyses. At the 3-cluster level, patients were divided into (1) bilateral medial temporal–dominant atrophy subtype (n = 52, ∼34.2%), (2) parietal-dominant subtype (n = 28, ∼18.4%) in which the bilateral parietal lobes, the precuneus, along with bilateral dorsolateral frontal lobes, were atrophic, and (3) diffuse atrophy subtype (n = 72, ∼47.4%) in which nearly all association cortices revealed atrophy. These 3 subtypes also differed in their demographic and clinical features. Conclusions: This cluster analysis of cortical thickness of the entire brain showed that AD dementia in the earlier stages can be categorized into various anatomical subtypes, with distinct clinical features.

Longitudinal changes of cortical thickness in early- versus late-onset Alzheimer's disease

Early-onset Alzheimers disease (EOAD) has been shown to progress more rapidly than late-onset Alzheimers disease (LOAD). However, no studies have compared the topography of brain volume reduction over time. The purpose of this 3-year longitudinal study was to compare EOAD and LOAD in terms of their rates of decline in cognitive testing and topography of cortical thinning. We prospectively recruited 36 patients with AD (14 EOAD and 22 LOAD) and 14 normal controls. All subjects were assessed with neuropsychological tests and with magnetic resonance imaging at baseline, Year 1, and Year 3. The EOAD group showed more rapid decline than the LOAD group in attention, language, and frontal-executive tests. The EOAD group also showed more rapid cortical thinning in widespread association cortices. In contrast, the LOAD group presented more rapid cortical thinning than the EOAD group only in the left parahippocampal gyrus. Our study suggests that patients with EOAD show more rapid cortical atrophy than patients with LOAD, which accounts for faster cognitive decline on neuropsychological tests.

Effects of cerebrovascular disease and amyloid beta burden on cognition in subjects with subcortical vascular cognitive impairment

Cerebrovascular disease (CVD) and amyloid burden are the most frequent pathologies in subjects with cognitive impairment. However, the relationship between CVD, amyloid burden, and cognition are largely unknown. We aimed to evaluate whether CVD (lacunes, white matter hyperintensities, and microbleeds) and amyloid burden (Pittsburgh compound B [PiB] retention ratio) contribute to cognitive impairment independently or interactively. We recruited 136 patients with subcortical vascular cognitive impairment who underwent magnetic resonance imaging, PiB-positron emission tomography, and neuropsychological testing. The number of lacunes was associated with memory, frontal dysfunctions, and disease severity. The volume of white matter hyperintensities and the PiB retention ratio were associated only with memory dysfunction. There was no direct correlation between CVD markers and PiB retention ratio except that the number of lacunes was negatively correlated with the PiB retention ratio. In addition, there were no interactive effects of CVD and PiB retention ratio on cognition. Our findings suggest that CVD and amyloid burden contribute independently and not interactively to specific patterns of cognitive dysfunction in patients with subcortical vascular cognitive impairment.

Fully automated pipeline for quantification and localization of white matter hyperintensity in brain magnetic resonance image

Automated white matter hyperintensity (WMH) segmentation on magnetic resonance imaging is greatly advantageous for various clinical studies using large‐sample data. Accurate localization of WMH can provide more beneficial information for clinical studies, as differences of regional WMH existence may be linked to clinical symptoms. We suggest a fully automated method for WMH quantification and localization without human interaction using T1‐weighted and fluid‐attenuated inversion‐recovery (FLAIR) images. The known sources of false‐positive results in the subarachnoid space and brain‐cerebrospinal fluid (CSF) interface were removed by applying a WMH candidate‐region mask. WMH segmentation was performed based on the Markov random field model. The intensity‐substitution method was developed for the accurate localization of WMH, with proper tissue classification and nonlinear registration. The performance of the method was evaluated via comparison with manual delineation; the similarity index and the overlap ratio were 89.94 and 81.90, respectively.

Clinical and imaging characteristics of dementia in multiple system atrophy

BACKGROUND Recent reports show that dementia occurs in 5-26% of multiple system atrophy (MSA) patients. However, the structural or pathological correlates of dementia in MSA are unclear yet. METHODS Of 152 patients with MSA, 59 fulfilled the criteria of probable MSA and 9 (15%) had dementia. Six of those patients and 9 without dementia, in addition to 10 controls, were included. All subjects underwent clinical evaluation including UMSARS, neuropsychological examinations, 3T-MRI, and Pittsburgh Compound B (PIB) PET imaging. The cortical thickness was assessed using surface-based morphometry. RESULTS Age and disease duration were similar between MSA with dementia and without dementia, while motor disability was more severe in MSA with dementia. In neuropsychological tests, attention, visuospatial function, and language function were impaired in MSA with dementia. Mean PIB binding was similar among the three groups. Cortical thickness was reduced in precuneus/cuneus, uncus, and posterior cingulate in MSA with dementia compared to the controls, and in parahippocampal and lingual cortices compared to MSA without dementia. CONCLUSIONS Dementia was found in 15% of the probable MSA patients, which was similar to those reported in previous studies. It appears that amyloid pathology has limited role in dementia in MSA, although some patients had increased cortical amyloid burden. Cortical thinning in MSA-D was observed in areas where cortical thinning was reported in Alzheimer disease or Parkinson disease dementia, but its pathological relevance is unclear. The neuropathological processes leading to the development of dementia in MSA appears to be multifactorial and heterogenous.

Cortical asymmetries in normal, mild cognitive impairment, and Alzheimer's disease

There are functional and structural neocortical hemispheric asymmetries in people with normal cognition. These asymmetries may be altered in patients with Alzheimers disease (AD) because there is a loss of neuronal connectivity in the heteromodal cortex. The purpose of this study is to test the hypothesis that individuals with amnestic mild cognitive impairment (aMCI), mild AD, and moderate to severe AD have progressive reductions in thickness asymmetries of the heteromodal neocortex. Right-handed elderly volunteers including normal cognition (NC), aMCI, and AD underwent 3-D volume imaging for cortical thickness. Although the cortical asymmetry pattern observed in normal cognition brains was generally maintained in aMCI and AD, there was a progressive decrease in the degree of asymmetry, especially in the inferior parietal lobule. A reduction of neocortical asymmetries may be a characteristic sign that occurs in patients with AD. Future studies are needed to evaluate whether this loss is specific to AD and if measurements of asymmetry can be used as diagnostic markers and for monitoring disease progression.

The burden of white matter hyperintensities is a predictor of progressive mild cognitive impairment in patients with Parkinson's disease

To evaluate whether white matter hyperintensities (WMHs) may act as an independent predictor for progression of cognitive status, the authors analyzed the longitudinal effects of WMHs on cognitive dysfunction in non‐demented patients with Parkinsons disease (PD).

The effects of small vessel disease and amyloid burden on neuropsychiatric symptoms: A study among patients with subcortical vascular cognitive impairments

Neuropsychiatric symptoms (NPS) affect the quality of life of patients with dementia and increase the burden on caregivers. We aimed to evaluate how small vessel disease (SVD) such as lacunae or white matter hyperintensities (WMH), and amyloid burden affect NPS. We recruited 127 patients with subcortical vascular cognitive impairment who were assessed with brain magnetic resonance imaging, Pittsburgh compound-B (PiB) positron emission tomography and the neuropsychiatric inventory (NPI). To explore the association between lacunae, WMH, or PiB retention ratio and NPS, we performed multivariate regression analysis after controlling for possible confounders. Each additional lacuna, especially in the frontal region, was associated with higher odds of depression, apathy, aberrant motor behavior, nighttime behavior, appetite changes, and higher score of total NPI; larger WMH volume, especially in the frontal region, was associated with higher odds of apathy and higher score of total NPI. Furthermore, for the effects of lacunae or WMH on total NPI score we set Clinical Dementia Rating Sum of Boxes as the mediator. Greater PiB retention ratio was associated with higher odds of delusions and irritability. The SVD and amyloid pathologies did not show interactive effects on NPS. Our findings suggested that SVD and amyloid burden independently affected specific NPS.

Amyloid burden, cerebrovascular disease, brain atrophy, and cognition in cognitively impaired patients

We investigated the independent effects of Alzheimers disease (AD) and cerebrovascular disease (CVD) pathologies on brain structural changes and cognition.

Cortical thickness and hippocampal shape in pure vascular mild cognitive impairment and dementia of subcortical type

The progression pattern of brain structural changes in patients with isolated cerebrovascular disease (CVD) remains unclear. To investigate the role of isolated CVD in cognitive impairment patients, patterns of cortical thinning and hippocampal atrophy in pure subcortical vascular mild cognitive impairment (svMCI) and pure subcortical vascular dementia (SVaD) patients were characterized.