Jin San Lee

Gray and white matter changes linking cerebral small vessel disease to gait disturbances

Objective: To investigate the topographic changes of white matter (WM) integrity and cortical thickness related to gait disturbances and determine whether these neural correlates mediate the association between cerebral small vessel disease (CSVD) and gait disturbances. Methods: A total of 129 patients with subcortical vascular cognitive impairment were included. CSVD severity was quantified as global and regional WM hyperintensities (WMH) volume and lacune and microbleed numbers. Amyloid burdens were assessed using Pittsburgh compound B (PiB)–PET scanning. Gait score was measured using a standardized scale. WM integrity was assessed by applying tract-based spatial statistics. Cortical thickness was measured using surface-based methods. Path analysis for gait score was performed using regional CSVD markers as predictors and fractional anisotropy (FA) and cortical thickness as mediators. Results: Periventricular WMH (PWMH) volume was associated with gait score, regardless of other CSVD. PiB retention ratio was not associated with gait score. Gait score was correlated with FA in the frontal and parietal WM and bilateral corpus callosum and with cortical thinning in the bilateral frontal and lateral temporo-parieto-occipital regions. Path analysis for gait score showed that PWMH contributed to gait disturbances with the mediation of mean FA or cortical thickness. Conclusions: Our findings suggest that WMH-related cortical thinning as well as disrupted integrity of periventricular WM is linked to gait disturbances.

Head to head comparison of [18F] AV-1451 and [18F] THK5351 for tau imaging in Alzheimer’s disease and frontotemporal dementia

PurposeTau accumulation is a core pathologic change in various neurodegenerative diseases including Alzheimer’s disease and frontotemporal lobar degeneration-tau. Recently, tau positron emission tomography tracers such as [18F] AV-1451 and [18F] THK5351 have been developed to detect tau deposition in vivo. In the present study, we performed a head to head comparison of these two tracers in Alzheimer’s disease and frontotemporal dementia cases and aimed to investigate which tracers are better suited to image tau in these disorders.MethodsA cross-sectional study was conducted using a hospital-based sample at a tertiary referral center. We recruited eight participants (two Alzheimer’s disease, four frontotemporal dementia and two normal controls) who underwent magnetic resonance image, amyloid positron emission tomography with [18F]-Florbetaben and tau positron emission tomography with both THK5351 and AV-1451. To measure regional AV1451 and THK5351 uptakes, we used the standardized uptake value ratios by dividing mean activity in target volume of interest by mean activity in the cerebellar hemispheric gray matter.ResultsAlthough THK5351 and AV-1451 uptakes were highly correlated, cortical uptake of AV-1451 was more striking in Alzheimer’s disease, while cortical uptake of THK5351 was more prominent in frontotemporal dementia. THK5351 showed higher off-target binding than AV-1451 in the white matter, midbrain, thalamus, and basal ganglia.ConclusionsAV-1451 is more sensitive and specific to Alzheimer’s disease type tau and shows lower off-target binding, while THK5351 may mirror non-specific neurodegeneration.

Early- vs late-onset subcortical vascular cognitive impairment

Objective: To evaluate the differences between early-onset subcortical vascular cognitive impairment (EO-SVCI) and late-onset subcortical vascular cognitive impairment (LO-SVCI) with regard to pathologic burden, structural changes, and cognitive function. Methods: We prospectively recruited 142 patients from a single referral center. Patients were divided into EO-SVCI (n = 30, age at onset <65 years) and LO-SVCI (n = 112, age at onset ≥65 years) groups. All patients underwent neuropsychological tests, 3T brain MRI, and [11C] Pittsburgh compound B (PiB)–PET. We compared pathologic burden such as small vessel disease and amyloid burden; structural changes such as structural network, cortical thickness, and hippocampal volume; and cognitive function between EO-SVCI and LO-SVCI. Results: EO-SVCI patients had more lacunes, while LO-SVCI patients had higher PiB standardized uptake value ratios. EO-SVCI patients exhibited more severe structural network disruptions in the frontal area, while LO-SVCI patients exhibited more severe cortical and hippocampal atrophy. Although disease severity did not differ between the 2 groups, frontal-executive dysfunction was more severe in EO-SVCI patients. Conclusions: EO-SVCI patients showed more vascular related factors, while LO-SVCI patients exhibited more Alzheimer disease–related characteristics. The greater number of lacunes in EO-SVCI might account for the more severe frontal network disruption and frontal-executive dysfunction, while the greater amyloid burden in LO-SVCI might account for the more severe cortical and hippocampal atrophy. Our findings suggest that the age at onset is a crucial factor that determines distinct features in SVCI patients, such as pathologic burden, structural changes, and cognitive function.

Albuminuria, Cerebrovascular Disease and Cortical Atrophy: among Cognitively Normal Elderly Individuals.

We tested the hypothesis that decreased glomerular filtration rate and albuminuria have different roles in brain structure alterations. We enrolled 1,215 cognitively normal individuals, all of whom underwent high-resolution T1-weighted volumetric magnetic resonance imaging scans. The cerebral small vessel disease burdens were assessed with white matter hyperintensities (WMH), lacunes, and microbleeds. Subjects were considered to have an abnormally elevated urine albumin creatinine ratio if the value was ≥17 mg/g for men and ≥25 mg/g for women. Albuminuria, but not estimated glomerular filtration rate (eGFR), was associated with increased WMH burdens (p = 0.002). The data was analyzed after adjusting for age, sex, education, history of hypertension, diabetes mellitus, hyperlipidemia, ischemic heart disease, stroke, total cholesterol level, body mass index, status of smoking and alcohol drinking, and intracranial volume. Albuminuria was also associated with cortical thinning, predominantly in the frontal and occipital regions (both p < 0.01) in multiple linear regression analysis. However, eGFR was not associated with cortical thickness. Furthermore, path analysis for cortical thickness showed that albuminuria was associated with frontal thinning partially mediated by WMH burdens. The assessment of albuminuria is needed to improve our ability to identify individuals with high risk for cognitive impairments, and further institute appropriate preventive measures.

Combined effects of physical exercise and education on age-related cortical thinning in cognitively normal individuals

We investigated the association between self-reported physical exercise and cortical thickness in a large sample of cognitively normal individuals. We also determined whether a combination of physical exercise and education had more protective effects on age-related cortical thinning than either parameter alone. A total of 1,842 participants were included in this analysis. Physical exercise was assessed using a questionnaire regarding intensity, frequency, and duration. Cortical thickness was measured using a surface-based method. Longer duration of exercise (≥1 hr/day), but not intensity or frequency, was associated with increased mean cortical thickness globally (P-value = 0.013) and in the frontal regions (P-value = 0.007). In particular, the association of exercise with cortical thinning had regional specificity in the bilateral dorsolateral prefrontal, precuneus, left postcentral, and inferior parietal regions. The combination of higher exercise level and higher education level showed greater global and frontal mean thickness than either parameter alone. Testing for a trend with the combination of high exercise level and high education level confirmed this finding (P-value = 0.001–0.003). Our findings suggest that combined exercise and education have important implications for brain health, especially considering the paucity of known protective factors for age-related cortical thinning.

Assessment of Extent and Role of Tau in Subcortical Vascular Cognitive Impairment Using 18F-AV1451 Positron Emission Tomography Imaging

Importance Amyloid-&bgr; (A&bgr;), tau, and cerebral small vessel disease (CSVD), which occasionally coexist, are the most common causes of cognitive impairments in older people. However, whether tau is observed in patients with subcortical vascular cognitive impairment (SVCI), as well as its associations with A&bgr; and CSVD, are not yet established. More importantly, the role of tau underlying cognitive impairments in SVCI is unknown. Objective To investigate the extent and the role of tau in patients with SVCI using 18F-AV1451, which is a new ligand to detect neurofibrillary tangles in vivo. Design, Setting, and Participants This cross-sectional study recruited 64 patients with SVCI from June 2015 to December 2016 at Samsung Medical Center, Seoul, Korea. The patients had significant ischemia on brain magnetic resonance imaging, defined as periventricular white matter hyperintensity at least 10 mm and deep white matter hyperintensity at least 25 mm. We excluded 3 patients with SVCI owing to segmentation error during AV1451 positron emission tomography analysis. Main Outcomes and Measures We calculated CSVD scores based on the volumes of white matter hyperintensities, numbers of lacunes, and microbleeds using magnetic resonance imaging data. The presence of A&bgr; was assessed using fluorine 18–labeled (18F) florbetaben positron emission tomography. Tau was measured using 18F-AV1451 positron emission tomography. We determined the spreading order of tau by sorting the regional frequencies of cortical involvement. We evaluated the complex associations between A&bgr;, CSVD, AV1451 uptake, and cognition in patients with SVCI. Results Of the 61 patients with SVCI, 44 (72.1%) were women and the mean (SD) age was 78.7 (6.3) years. Patients with SVCI, especially patients with A&bgr;-negative SVCI, showed higher AV1451 uptake in the inferior temporal areas compared with normal control individuals. In patients with SVCI, A&bgr; positivity and CSVD score were each independently associated with increased AV1451 uptake in the medial temporal and inferior temporal regions, respectively. Involvement frequency of AV1451 uptake in the fusiform gyrus, inferior temporal, and precuneus regions were higher than that in the parahippocampal region. In patients with SVCI, higher AV1451 uptake in the inferior temporal and medial temporal regions correlated with worse language and general cognitive function. In patients with SVCI, A&bgr; positivity and CSVD score each correlated with worse general cognitive function, which was completely mediated by AV1451 uptake in the entorhinal cortex and inferior temporal gyrus, respectively. Conclusions and Relevance Our findings suggest that in SVCI, both A&bgr; and CSVD were independently associated with increased tau accumulation. Furthermore, tau burden played a pivotal role because it was the final common pathway for the cognitive impairment in patients with SVCI.

Correlations between Gray Matter and White Matter Degeneration in Pure Alzheimer’s Disease, Pure Subcortical Vascular Dementia, and Mixed Dementia

Alzheimer’s disease dementia (ADD) and subcortical vascular dementia (SVaD) both show cortical thinning and white matter (WM) microstructural changes. We evaluated different patterns of correlation between gray matter (GM) and WM microstructural changes in pure ADD, pure SVaD, and mixed dementia. We enrolled 40 Pittsburgh compound B (PiB) positive ADD patients without WM hyperintensities (pure ADD), 32 PiB negative SVaD patients (pure SVaD), 23 PiB positive SVaD patients (mixed dementia), and 56 normal controls. WM microstructural integrity was quantified using fractional anisotropy (FA), axial diffusivity (DA), and radial diffusivity (DR) values. We used sparse canonical correlation analysis to show correlated regions of cortical thinning and WM microstructural changes. In pure ADD patients, lower FA in the frontoparietal area correlated with cortical thinning in the left inferior parietal lobule and bilateral paracentral lobules. In pure SVaD patients, lower FA and higher DR across extensive WM regions correlated with cortical thinning in bilateral fronto-temporo-parietal regions. In mixed dementia patients, DR and DA changes across extensive WM regions correlated with cortical thinning in the bilateral fronto-temporo-parietal regions. Our findings showed that the relationships between GM and WM degeneration are distinct in pure ADD, pure SVaD, and mixed dementia, suggesting that different pathomechanisms underlie their correlations.

Protective effects of APOE e2 against disease progression in subcortical vascular mild cognitive impairment patients: A three-year longitudinal study

Although the association between apolipoprotein E (APOE) genotype and disease progression is well characterized in patients with Alzheimer’s disease, such a relationship is unknown in patients with subcortical vascular cognitive impairment. We evaluated whether APOE genotype is associated with disease progression in subcortical vascular mild cognitive impairment (svMCI) patients. We prospectively recruited 72 svMCI patients (19 APOE4 carriers, 42 APOE3 homozygotes, and 11 APOE2 carriers). Patients were annually followed-up with brain MRI and neuropsychological tests for three years and underwent a second Pittsburgh compound B (PiB)-PET at a mean interval of 32.3 months. Amyloid-ß burden was quantified by PiB standardized uptake value ratio (SUVR), and the amount of small vessel disease was quantified by number of lacune and small vessel disease score on MRI. We also measured cortical thickness. During the three years of follow-up, compared to the APOE3 homozygotes, there was less increase in PiB SUVR among APOE2 carriers (p = 0.023), while the APOE genotype did not show significant effects on small vessel disease progression. APOE2 carriers also showed less cortical thinning (p = 0.023) and a slower rate of cognitive decline (p = 0.009) compared to those with APOE3 homozygotes. Our findings suggest that, in svMCI patients, APOE2 has protective effects against amyloid-ß accumulation, cortical thinning, and cognitive decline.

Classifying anatomical subtypes of subjective memory impairment

We aimed to categorize subjective memory impairment (SMI) individuals based on their patterns of cortical thickness and to propose simple models that can classify each subtype. We recruited 613 SMI individuals and 613 age- and gender-matched normal controls. Using hierarchical agglomerative cluster analysis, SMI individuals were divided into 3 subtypes: temporal atrophy (12.9%), minimal atrophy (52.4%), and diffuse atrophy (34.6%). Individuals in the temporal atrophy (Alzheimers disease-like atrophy) subtype were older, had more vascular risk factors, and scored the lowest on neuropsychological tests. Combination of these factors classified the temporal atrophy subtype with 73.2% accuracy. On the other hand, individuals with the minimal atrophy (non-neurodegenerative) subtype were younger, were more likely to be female, and had depression. Combination of these factors discriminated the minimal atrophy subtype with 76.0% accuracy. We suggest that SMI can be largely categorized into 3 anatomical subtypes that have distinct clinical features. Our models may help physicians decide next steps when encountering SMI patients and may also be used in clinical trials.

Distinctive Clinical Effects of Haemorrhagic Markers in Cerebral Amyloid Angiopathy

Restricted lobar cerebral microbleeds (CMBs) and cortical superficial siderosis (CSS) are the characteristic markers of cerebral amyloid angiopathy (CAA). However, their effects on clinical features has not been evaluated well. The purpose of this study is to investigate the clinical implication of these markers in clinical-radiologically diagnosed CAA. A total of 372 patients with possible or probable CAA who met the modified Boston criteria were recruited in a memory clinic setting. Cortical thickness was measured using surface based methods. Presence of restricted multiple lobar CMBs were independently associated with cortical thinning across the entire cortical regions while presence of CSS was independently associated with cortical thinning primarily in the bilateral frontal region. Presence of restricted multiple lobar CMBs was associated with impairment in all cognitive domains such as attention, language, visuospatial, memory and frontal executive functions while presence of CSS was associated with attention and frontal dysfunction. The relationships of restricted multiple lobar CMBs or CSS with cognitive impairment were partially mediated by thinning in the corresponding cortical regions. Our findings suggested that restricted multiple lobar CMBs and CSS affect distinctive clinical features, providing new insights into potential mechanisms in CAA.