Peak Width Of Skeletonized Mean Diffusivity Research Articles

Macro- and microvascular contributions to cerebral structural alterations in patients with asymptomatic carotid artery stenosis.

Atherosclerosis can underly internal carotid artery stenosis (ICAS), a major risk factor for ischemic stroke, as well as small vessel disease (SVD). This study aimed to investigate hemodynamics and structural alterations associated with SVD in ICAS patients. 28 patients with unilateral asymptomatic ICAS and 30 age-matched controls underwent structural (T1-/T2-weighted and diffusion tensor imaging [DTI]) and hemodynamic (pseudo-continuous arterial spin labeling and dynamic susceptibility contrast) magnetic resonance imaging. SVD-related alterations were assessed using free water (FW), FW-corrected DTI, and peak-width of skeletonized mean diffusivity (PSMD). Furthermore, cortical thickness, cerebral blood flow (CBF), and capillary transit time heterogeneity (CTH) were analyzed. Ipsilateral to the stenosis, cortical thickness was significantly decreased in the posterior dorsal cingulate cortex (p = 0.024) and temporal pole (p = 0.028). ICAS patients exhibited elevated PSMD (p = 0.005), FW (p < 0.001), and contralateral alterations in FW-corrected DTI metrics. We found significantly lateralized CBF (p = 0.011) and a tendency for lateralized CTH (p = 0.067) in the white matter (WM) related to ICAS. Elevated PSMD and FW may indicate a link between SVD and WM changes. Contralateral alterations were seen in FW-corrected DTI, whereas hemodynamic and cortical changes were mainly ipsilateral, suggesting SVD might influence global brain changes concurrent with ICAS-related hemodynamic alterations.

Association Between Hippocampal Volumes and Cognition in Cerebral Amyloid Angiopathy.

Accumulating evidence suggests that gray matter atrophy, often considered a marker of Alzheimer disease (AD), can also result from cerebral small vessel disease (CSVD). Cerebral amyloid angiopathy (CAA) is a form of sporadic CSVD, diagnosed through neuroimaging criteria, that often co-occurs with AD pathology and leads to cognitive impairment. We sought to identify the role of hippocampal integrity in the development of cognitive impairment in a cohort of patients with possible and probable CAA. Patients were recruited from an ongoing CAA study at Massachusetts General Hospital. Composite scores defined performance in the cognitive domains of memory, language, executive function, and processing speed. Hippocampal subfields' volumes were measured from 3T MRI, using an automated method, and multivariate linear regression models were used to estimate their association with each cognitive domain and relationship to CAA-related neuroimaging markers. One hundred twenty patients, 36 with possible (age mean [range]: 75.6 [65.6-88.9]), 67 with probable CAA (75.9 [59.0-94.0]), and 17 controls without cognitive impairment and CSVD (72.4 [62.5-82.7]; 76.4% female patients), were included in this study. We found a positive association between all investigated hippocampal subfields and memory and language, whereas specific subfields accounted for executive function (CA4 [Estimate = 5.43; 95% CI 1.26-9.61; p = 0.020], subiculum [Estimate = 2.85; 95% CI 0.67-5.02; p = 0.022]), and processing speed (subiculum [Estimate = 1.99; 95% CI 0.13-3.85; p = 0.036]). These findings were independent of other CAA-related markers, which did not have an influence on cognition in this cohort. Peak width of skeletonized mean diffusivity (PSMD), a measure of white matter integrity, was negatively associated with hippocampal subfields' volumes (CA3 [Estimate = -0.012; 95% CI -0.020 to -0.004; p = 0.034], CA4 [Estimate = -0.010; 95% CI -0.020 to -0.0007; p = 0.037], subiculum [Estimate = -0.019; 95% CI -0.042 to -0.0001; p = 0.003]). These results suggest that hippocampal integrity is an independent contributor to cognitive impairment in patients with CAA and that it might be related to loss of integrity in the white matter. Further studies exploring potential causes and directionality of the relationship between white matter and hippocampal integrity may be warranted.

White matter injury mediates the effects of PS1 mutation position on clinical measures in late disease stage

AbstractBackgroundClinical presentation of dominantly inherited Alzheimer disease (DIAD) varies across individuals with Presenilin‐1 (PS1) pathogenic mutations. Previous findings suggest that individuals with a PS1 mutation after codon 200 have more small vessel disease (SVD) pathology (Mann et al., 2001; Ryan et al., 2015). We investigated the effect of mutation position on clinical measures, including indirect effects via SVD as estimated by imaging markers of white matter injury.MethodWe evaluated 393 individuals with DIAD family history of PS1 mutations who underwent clinical and imaging assessments from the DIAN study. Among them, 245 carried a mutation before (Pre‐200MC, n = 83) or after codon‐200 (Post‐200MC, n = 162) and the remaining were non‐carriers (NC, n = 148). We assessed clinical disease stage with the Clinical Dementia Rating® Sum of Boxes (CDR®‐SB) scale and the estimated years to symptoms onset (EYO). White matter injury metrics included periventricular white matter hyperintensity (PVWMH) volumes from T2‐FLAIR and the peak width of skeletonized mean diffusivity (PSMD) from DTI (Shirzadi et al., 2022). Accounting for age of onset, sex, education, and APOE‐ɛ4 status, linear mixed‐effects models evaluated mutation position by EYO effect on SVD and on dementia in all participants. Further mediation analysis evaluated these effects within the carrier groups. Missing values were imputed using random forest algorithm.ResultPost‐200MC had more white matter injury with advanced EYO compared to Pre‐200MC (estimatesPVWMH = 65.3±31.8, P‐value&lt;.05, estimatesPSMD = 0.01±0.003, P‐value&lt;.0005) and to non‐carriers (estimatesPVWMH = 61.5±27.4, P‐value&lt;.05, estimatesPSMD = 0.01±0.003, P‐value&lt;.0005; Figure 1A). Post‐200MC presented higher CDR‐SB scores with advanced EYO compared to Pre‐200MC (estimatesCDR‐SB = 0.08±0.03, P‐value&lt;.005) and to non‐carriers (estimatesCDR‐SB = 0.19±0.02, P‐value&lt;.0001; Figure 1B). When EYO&gt;0, the effects of mutation position on CDR‐SB were significantly mediated by PVWMH (e.g., average causal mediation effect at EYO = 0.5: estimatesCDR‐SB = 0.06[0.;0.14], P‐value&lt;.05) or PSMD (e.g., average causal mediation effect at EYO = 0.5: estimatesCDR‐SB = 0.2[0.05;0.37], P‐value&lt;.05; Table1).ConclusionThese findings give further insights on how mutation position within the PS1 gene influences clinical disease presentation in DIAD. This characterization may inform future clinical trials in this population as the presence of small vessel disease contributes to a more severe disease course, which may influence treatment outcome and decisions. Funding: AARFD‐20‐681815; U19AG032438.

Influence of education level on domain‐specific MOCA performance in the MarkVCID cohort

AbstractBackgroundEducation level is a well‐recognized co‐factor for cognitive performance and a potential confounder in the application of cognitive evaluations in diverse populations. The Montreal Cognitive Assessment (MoCA) is a widely utilized screening tool for Mild Cognitive Impairment (MCI) composed of 6 domains of cognition: Executive Function (EFC), Attention and Concentration (AC), Language (LANG), Visuospatial (VIS), Memory (MEM), and Orientation (ORIEN). Education is currently accounted for globally by adding 1 point to the total MoCA score. This study considers the impact of education level on a domain‐specific scoring of the MoCA.MethodWe utilized longitudinal subject level data from one site within the MarkVCID Consortium (UCSF) composed of 578 subjects (59.5% female; 82.9% white), mean age 71.5 (+/‐ 8.7). Mean educational level was 15.3 (+/‐4.7) years. Within the cohort, 37 subjects lacked educational level and were omitted (final n = 541). Multivariate linear regression models were used to relate educational level with total and domain specific MoCA score performance at baseline while controlling for the influence of age, sex, and recognized MarkVCID biomarkers that impact cognitive performance including white matter hyperintensity (logWMH), fractional anisotropy (FA), free water (FW), and peak width of skeletonized mean diffusivity (PSMD).ResultsAn age‐, sex‐adjusted model replicated a significant association of education level with MoCA total score (p&lt;0.001, b = .336). Among the MoCA domains, EFC was most affected by education level (p&lt;.001, b = .412), followed by AC (p&lt;.001, b = .352). Other MoCA domains were not significantly associated with educational level. Several MoCA domains, namely MEM and ORIEN, showed an association with MarkVCID biomarkers including WMH and FW (p‐values &lt;.001). In regression models controlled for MarkVCID imaging biomarkers, educational level remained significantly associated with total and domain‐specific MoCA performance.ConclusionEducation does not equally contribute to all cognitive domains assessed by the MoCA, mostly affecting EFC and AC. These findings suggest that considering education level in a domain‐specific manner could provide a more accurate interpretation of the cognitive impairment.

Systemic vascular risk, white matter injury, and relative cerebral blood flow independently contribute to cognitive decline beyond amyloid and tau burden

AbstractBackgroundAge, systemic vascular risk factors, white matter injury, cerebral blood flow, amyloid, and tau burden are well‐established contributors to late‐life cognitive decline. Given the strong relationship among these measures, we proposed a model to extract latent factors and isolate domain‐specific measures that underlie cognitive decline in preclinical AD.MethodData were available for 166 cognitively unimpaired older adults from Harvard Aging Brain Study (Table1). We used the following measures: 1) cortical amyloid burden from PiB‐PET; 2) inferior temporal cortex FTP‐PET; 3) relative cerebral blood flow (R1) from dynamically‐acquired PiB‐PET; 4) white matter hyperintensities (WMH) from FLAIR‐MRI; 5) Peak width of skeletonized mean diffusivity (PSMD) from DTI‐MRI; 6) gray matter volume (GMV) from MPRAGE‐MRI; 7) Framingham Heart Study cardiovascular disease risk (CVD); 8) Preclinical Alzheimer Cognitive Composite‐5 (PACC). We extracted slopes using linear mixed effect models for longitudinal PACC decline and GMV atrophy (follow‐up = 7.4±2.8 years). The remaining data were obtained from baseline. We used exploratory factor analysis (varimax rotations) to extract orthogonal factors. These factors were used in a regression model to explain PACC decline. We next examined whether GMV atrophy acts as a mediator of factors and PACC decline. Subsequently, we investigated whether factors interact to further explain PACC decline.ResultsOriginal variables were highly interrelated (Figure1A) and correlated with PACC decline (Figure1B). Scree test showed 6 factors were sufficient (cumulative variance:96%, Figure2A). All factors except Factor5 (age) independently explained PACC decline (Figure2B, r2 = 0.44). Including GMV atrophy removed effect of Factor1 (white matter injury, Figure2B, r2 = 0.51). Factor3 (amyloid) interacted with Factor1 and Factor4 (tau) in explaining PACC decline (Figure2C, r2 = 0.58).ConclusionLatent factors of systemic vascular risk, white matter injury, and relative cerebral blood flow (but not age) independently explain cognitive decline beyond amyloid and tau burden in this preclinical AD cohort. GMV atrophy mediates these associations with the strongest effect on white matter injury suggesting a strong link between white matter injury and neurodegeneration. These results suggest that current markers of cerebrovascular injury contribute to cognitive decline beyond systemic vascular risk (CVD), amyloid, and tau burden. The mechanism by which systemic vascular risk impacts cognition requires further explication.

Microstructural white matter integrity in relation to vascular reactivity in Dutch-type hereditary cerebral amyloid angiopathy

Cerebral Amyloid Angiopathy (CAA) is characterized by cerebrovascular amyloid-β accumulation leading to hallmark cortical MRI markers, such as vascular reactivity, but white matter is also affected. By studying the relationship in different disease stages of Dutch-type CAA (D-CAA), we tested the relation between vascular reactivity and microstructural white matter integrity loss. In a cross-sectional study in D-CAA, 3 T MRI was performed with Blood-Oxygen-Level-Dependent (BOLD) fMRI upon visual activation to assess vascular reactivity and diffusion tensor imaging to assess microstructural white matter integrity through Peak Width of Skeletonized Mean Diffusivity (PSMD). We assessed the relationship between BOLD parameters – amplitude, time-to-peak (TTP), and time-to-baseline (TTB) – and PSMD, with linear and quadratic regression modeling. In total, 25 participants were included (15/10 pre-symptomatic/symptomatic; mean age 36/59 y). A lowered BOLD amplitude (unstandardized β = 0.64, 95%CI [0.10, 1.18], p = 0.02, Adjusted R2 = 0.48), was quadratically associated with increased PSMD levels. A delayed BOLD response, with prolonged TTP (β = 8.34 × 10−6, 95%CI [1.84 × 10−6, 1.48 × 10−5], p = 0.02, Adj. R2 = 0.25) and TTB (β = 6.57 × 10−6, 95%CI [1.92 × 10−6, 1.12 × 10−5], p = 0.008, Adj. R2 = 0.29), was linearly associated with increased PSMD. In D-CAA subjects, predominantly in the symptomatic stage, impaired cerebrovascular reactivity is related to microstructural white matter integrity loss. Future longitudinal studies are needed to investigate whether this relation is causal.

Cerebral small vessel disease burden is associated with decreased abundance of gut Barnesiella intestinihominis bacterium in the Framingham Heart Study

A bidirectional communication exists between the brain and the gut, in which the gut microbiota influences cognitive function and vice-versa. Gut dysbiosis has been linked to several diseases, including Alzheimer's disease and related dementias (ADRD). However, the relationship between gut dysbiosis and markers of cerebral small vessel disease (cSVD), a major contributor to ADRD, is unknown. In this cross-sectional study, we examined the connection between the gut microbiome, cognitive, and neuroimaging markers of cSVD in the Framingham Heart Study (FHS). Markers of cSVD included white matter hyperintensities (WMH), peak width of skeletonized mean diffusivity (PSMD), and executive function (EF), estimated as the difference between the trail-making tests B and A. We included 972 FHS participants with MRI scans, neurocognitive measures, and stool samples and quantified the gut microbiota composition using 16S rRNA sequencing. We used multivariable association and differential abundance analyses adjusting for age, sex, BMI, and education level to estimate the association between gut microbiota and WMH, PSMD, and EF measures. Our results suggest an increased abundance of Pseudobutyrivibrio and Ruminococcus genera was associated with lower WMH and PSMD (p values < 0.001), as well as better executive function (p values < 0.01). In addition, in both differential and multivariable analyses, we found that the gram-negative bacterium Barnesiella intestinihominis was strongly associated with markers indicating a higher cSVD burden. Finally, functional analyses using PICRUSt implicated various KEGG pathways, including microbial quorum sensing, AMP/GMP-activated protein kinase, phenylpyruvate, and β-hydroxybutyrate production previously associated with cognitive performance and dementia. Our study provides important insights into the association between the gut microbiome and cSVD, but further studies are needed to replicate the findings.

Distinct cerebral small vessel disease impairment in early-and late-onset Alzheimer's disease.

This study investigated cerebral small vessel disease (CSVD) damage patterns in early-onset and late-onset Alzheimer's disease (EOAD and LOAD) and their effects on cognitive function. This study included 93 participants, 45 AD patients (14 EOAD and 31 LOAD), and 48 normal controls (13 YNC and 35 ONC) from the ADNI database. All participants had diffusion tensor imaging data; some had amyloid PET and plasma p-tau181 data. The study used peak width of skeletonized mean diffusivity (PSMD) to measure CSVD severity and compared PSMD between patients and age-matched controls. The effect of age on the relationship between PSMD and cognition was also examined. The study also repeated the analysis in amyloid-positive AD patients and amyloid-negative controls in another independent database (31 EOAD and 38 LOAD), and the merged database. EOAD and LOAD showed similar cognitive function and disease severity. PSMD was validated as a reliable correlate of cognitive function. In the ADNI database, PSMD was significantly higher for LOAD and showed a tendency to increase for EOAD; in the independent and merged databases, PSMD was significantly higher for both LOAD and EOAD. The impact of PSMD on cognitive function was notably greater in the younger group (YNC and EOAD) than in the older group (ONC and LOAD), as supported by the ADNI and merged databases. EOAD has less CSVD burden than LOAD, but has a greater impact on cognition. Proactive cerebrovascular prevention strategies may have potential clinical value for younger older adults with cognitive decline.

Associations of MRI-Derived Glymphatic System Impairment With Global White Matter Damage and Cognitive Impairment in Mild Traumatic Brain Injury: A DTI-ALPS Study.

Assessing the glymphatic function using diffusion tensor image analysis along the perivascular space (DTI-ALPS) may be helpful for mild traumatic brain injury (mTBI) management. To assess glymphatic function using DTI-ALPS and its associations with global white matter damage and cognitive impairment in mTBI. Prospective. Thirty-four controls (44.1% female, mean age 49.2 years) and 58 mTBI subjects (43.1% female, mean age 48.7 years), including uncomplicated mTBI (N = 32) and complicated mTBI (N = 26). 3-T, single-shot echo-planar imaging sequence. Magnetic resonance imaging (MRI) was done within 1 month since injury. DTI-ALPS was performed to assess glymphatic function, and peak width of skeletonized mean diffusivity (PSMD) was used to assess global white matter damage. Cognitive tests included Auditory Verbal Learning Test and Digit Span Test (forward and backward). Neuroimaging findings comparisons were done between mTBI and control groups. Partial correlation and multivariable linear regression assessed the associations between DTI-ALPS, PSMD, and cognitive impairment. Mediation effects of PSMD on the relationship between DTI-ALPS and cognitive impairment were explored. P-value <0.05 was considered statistically significant, except for cognitive correlational analyses with a Bonferroni-corrected P-value set at 0.05/3 ≈ 0.017. mTBI showed lower DTI-ALPS and higher PSMD, especially in complicated mTBI. DTI-ALPS was significantly correlated with verbal memory (r = 0.566), attention abilities (r = 0.792), executive function (r = 0.618), and PSMD (r = -0.533). DTI-ALPS was associated with verbal memory (β = 8.77, 95% confidence interval [CI] 5.00, 12.54), attention abilities (β = 5.67, 95% CI 4.56, 6.97), executive function (β = 2.34, 95% CI 1.49, 3.20), and PSMD (β = -0.79, 95% CI -1.15, -0.43). PSMD mediated 46.29%, 20.46%, and 24.36% of the effects for the relationship between DTI-ALPS and verbal memory, attention abilities, and executive function. Glymphatic function may be impaired in mTBI reflected by DTI-ALPS. Glymphatic dysfunction may cause cognitive impairment related to global white matter damage after mTBI. 2 TECHNICAL EFFICACY: Stage 2.

Association between periodontal disease and microstructural brain alterations in the Hamburg City Health Study.

The aim of the PAROBRAIN study was to examine the association of periodontal health with microstructural white matter integrity and cerebral small vessel disease (CSVD) in the Hamburg City Health Study, a large population-based cohort with dental examination and brain magnetic resonance imaging (MRI). Periodontal health was determined by measuring clinical attachment loss (CAL) and plaque index. Additionally, the decayed/missing/filled teeth (DMFT) index was quantified. 3D-FLAIR and 3D-T1-weighted images were used for white matter hyperintensity (WMH) segmentation. Diffusion-weighted MRI was used to quantify peak width of skeletonized mean diffusivity (PSMD). Data from 2030 participants were included in the analysis. Median age was 65 years, with 43% female participants. After adjusting for age and sex, an increase in WMH load was significantly associated with more CAL, higher plaque index and higher DMFT index. PSMD was significantly associated with the plaque index and DMFT. Additional adjustment for education and cardiovascular risk factors revealed a significant association of PSMD with plaque index (p < .001) and DMFT (p < .01), whereas effects of WMH load were attenuated (p > .05). These findings suggest an adverse effect of periodontal health on CSVD and white matter integrity. Further research is necessary to examine whether early treatment of periodontal disease can prevent microstructural brain damage.

White Matter and Gray Matter Changes Related to Cognition in Community populations (P12-6.008)

<h3>Objective:</h3> To investigate the global and topographic changes of white matter integrity and cortical structure related to cognitive impairments in a community-based population. <h3>Background:</h3> Further studies in associations of cortical and subcortical changes with cognitive function would better explain the pathology of cognitive impairment. <h3>Design/Methods:</h3> A cross-sectional analysis was performed based on 995 subjects (aged 56.8±9.1 years, 34.8% males) from the Shunyi study, a community-dwelling cohort. Cognitive status was accessed by a series of neurocognitive tests including Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), category Verbal Fluency Test (VFT), Digit Span Test (DST), and Trail Making Tests A and B (TMT-A and TMT-B). Structural and diffusional MRI data were acquired. White matter integrity was assessed using fractional anisotropy (FA), mean diffusivity (MD), and peak width of skeletonized mean diffusivity (PSMD). Cortical surface area, thickness, and volume were measured using Freesurfer. Probabilistic tractography was further conducted to track the white matter fibers connecting to the cortical regions related to cognition. General linear models were used to investigate the association between brain structure and cognition. <h3>Results:</h3> Global mean FA and MD were associated with VFT performances (FA, β=0.119, p&lt;0.001; MD, β=−0.128, p&lt;0.001). Global cortical surface area, thickness, and volume were not related to cognitive scores. In tract-based spatial statistics, disrupted white matter integrity was related to cognitive impairment mainly in visuomotor processing speed and executive function (TMT-A and VFT), rather than short-term memory (DST). In the whole brain vertex-wise analysis, surface area in the left orbitofrontal cortex and left central sulcus were positively associated with MMSE and MoCA scores. These associations were independent of the connecting white matter tract. <h3>Conclusions:</h3> Disrupted white matter integrity and regional cortical surface area were related to cognition in community-dwelling populations. The associations of cortical surface area and cognition were independent of the connecting white matter tract. <b>Disclosure:</b> Mrs. Li has nothing to disclose. Jing Yuan has nothing to disclose. Fei Han has nothing to disclose. Lixin Zhou has nothing to disclose. Jun Ni has nothing to disclose. Ming Yao has nothing to disclose. Shuyang Zhang has nothing to disclose. Zhengyu Jin has nothing to disclose. Liying Cui has nothing to disclose. Feifei Zhai has nothing to disclose. Yi-Cheng Zhu has nothing to disclose.

Peak width of skeletonized mean diffusivity and cognitive performance in cerebral amyloid angiopathy.

Cerebral Amyloid Angiopathy (CAA) is a cerebral small vessel disease that can lead to microstructural disruption of white matter (WM), which can be measured by the Peak Width of Skeletonized Mean Diffusivity (PSMD). We hypothesized that PSMD measures would be increased in patients with CAA compared to healthy controls (HC), and increased PSMD is associated with lower cognitive scores in patients with CAA. Eighty-one probable CAA patients without cognitive impairment who were diagnosed with Boston criteria and 23 HCs were included. All subjects underwent an advanced brain MRI with high-resolution diffusion-weighted imaging (DWI). PSMD scores were quantified from a probabilistic skeleton of the WM tracts in the mean diffusivity (MD) image using a combination of fractional anisotropy (FA) and the FSL Tract-Based Spatial Statistics (TBSS) algorithm (www.psmd-marker.com). Within CAA cohort, standardized z-scores of processing speed, executive functioning and memory were obtained. The mean of age and sex were similar between CAA patients (69.6 ± 7.3, 59.3% male) and HCs (70.6 ± 8.5, 56.5% male) (p = 0.581 and p = 0.814). PSMD was higher in the CAA group [(4.13 ± 0.94) × 10-4 mm2/s] compared to HCs [(3.28 ± 0.51) × 10-4 mm2/s] (p < 0.001). In a linear regression model corrected for relevant variables, diagnosis of CAA was independently associated with increased PSMD compared to HCs (ß = 0.45, 95% CI 0.13-0.76, p = 0.006). Within CAA cohort, higher PSMD was associated with lower scores in processing speed (p < 0.001), executive functioning (p = 0.004), and memory (0.047). Finally, PSMD outperformed all other MRI markers of CAA by explaining most of the variance in models predicting lower scores in each cognitive domain. Peak Width of Skeletonized Mean Diffusivity is increased in CAA, and it is associated with worse cognitive scores supporting the view that disruption of white matter has a significant role in cognitive impairment in CAA. As a robust marker, PSMD can be used in clinical trials or practice.

White matter and gray matter changes related to cognition in community populations.

Further studies are needed to improve the understanding of the pathological process underlying cognitive impairments. The purpose of this study is to investigate the global and topographic changes of white matter integrity and cortical structure related to cognitive impairments in a community-based population. A cross-sectional analysis was performed based on 995 subjects (aged 56.8 ± 9.1 years, 34.8% males) from the Shunyi study, a community-dwelling cohort. Cognitive status was accessed by a series of neurocognitive tests including Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), category Verbal Fluency Test (VFT), Digit Span Test (DST), and Trail Making Tests A and B (TMT-A and TMT-B). Structural and diffusional MRI data were acquired. White matter integrity was assessed using fractional anisotropy (FA), mean diffusivity (MD), and peak width of skeletonized mean diffusivity (PSMD). Cortical surface area, thickness, and volume were measured using Freesurfer. Probabilistic tractography was further conducted to track the white matter fibers connecting to the cortical regions related to cognition. General linear models were used to investigate the association between brain structure and cognition. Global mean FA and MD were significantly associated with performances in VFT (FA, β 0.119, p < 0.001; MD, β -0.128, p < 0.001). Global cortical surface area, thickness, and volume were not related to cognitive scores. In tract-based spatial statistics analysis, disruptive white matter integrity was related to cognition impairment, mainly in visuomotor processing speed, semantic memory, and executive function (TMT-A and VFT), rather than verbal short-term memory and working memory (DST). In the whole brain vertex-wise analysis, surface area in the left orbitofrontal cortex, right posterior-dorsal part of the cingulate gyrus, and left central sulcus were positively associated with MMSE and MoCA scores, and the association were independent of the connecting white matter tract. Disrupted white matter integrity and regional cortical surface area were related to cognition in community-dwelling populations. The associations of cortical surface area and cognition were independent of the connecting white matter tract.

Abstract 162: Molecular And Microstructural Alterations In Cerebral Amyloid Angiopathy-related Hemorrhagic Manifestations

Background and Purpose: We aimed to compare the amyloid load and degree of microstructural injury among Cerebral Amyloid Angiopathy (CAA) patients with either higher lobar cerebral microbleed (CMB) counts or higher cortical superficial siderosis (cSS) extent against CAA patients with lower hemorrhagic load. Methods: The study included 38 cognitively healthy probable CAA patients with lobar intracerebral hemorrhage (ICH) and 38 age, sex-matched healthy controls (HC) who underwent advanced MRI, and Pittsburgh Compound B (PiB) PET scans. Patients were categorized into CMB-Dominant (CMB-D) and cSS-Dominant (cSS-D) based on the number and extent of CMB and cSS using previously identified cutoffs (Figure). The mean global cortical amyloid load was calculated from PiB-PET scans and represented by PiB-DVR. Within the CAA cohort, the Peak Width of Skeletonized Mean Diffusivity (PSMD) was calculated from diffusion MRIs and used as a marker of microstructural integrity. Results: Patients with CAA had significantly higher PiB-DVR than HCs (1.40±0.24 vs. 1.19±0.22, p&lt;0.001). Both CMB-D and cSS-D CAA patients had significantly higher amyloid and increased (worse) PSMD compared to CAA patients with a non-dominant low hemorrhagic load (Figure). These results did not change in separate regression models corrected for age and sex. PiB-DVR significantly correlated with increased PSMD (r=0.346, p=0.033). Conclusions: Our findings support the view that vascular amyloid load drives higher CMB counts, more extensive cSS, and microstructural injury in patients with CAA. Furthermore, the correlations among these markers suggest that these MRI-based categorizations (CMB-D and cSS-D patients) can be used for disease staging and further research.

Association between Coffee Consumption and Brain MRI Parameters in the Hamburg City Health Study.

Despite associations of regular coffee consumption with fewer neurodegenerative disorders, its association with microstructural brain alterations is unclear. To address this, we examined the association of coffee consumption with brain MRI parameters representing vascular brain damage, neurodegeneration, and microstructural integrity in 2316 participants in the population-based Hamburg City Health Study. Cortical thickness and white matter hyperintensity (WMH) load were measured on FLAIR and T1-weighted images. Microstructural white matter integrity was quantified as peak width of skeletonized mean diffusivity (PSMD) on diffusion-weighted MRI. Daily coffee consumption was assessed in five groups (<1 cup, 1-2 cups, 3-4 cups, 5-6 cups, >6 cups). In multiple linear regressions, we examined the association between brain MRI parameters and coffee consumption (reference group <1 cup). After adjustment for covariates, 3-4 cups of daily coffee were associated with lower PSMD (p = 0.028) and higher cortical thickness (p = 0.015) compared to <1 cup. Moreover, 1-2 cups per day was also associated with lower PSMD (p = 0.022). Associations with WMH load or other groups of coffee consumption were not significant (p > 0.05). The findings indicate that regular coffee consumption is positively associated with microstructural white matter integrity and cortical thickness. Further research is necessary to determine longitudinal effects of coffee on brain microstructure.

Peak Width of Skeletonized Mean Diffusivity: A Neuroimaging Marker for White Matter Injury.

A leading cause of white matter (WM) injury in older individuals is cerebral small vessel disease (SVD). Cerebral SVD is the most prevalent vascular contributor to cognitive impairment and dementia. Therapeutic progress for cerebral SVD and other WM disorders depends on the development and validation of neuroimaging markers suitable as outcome measures in future interventional trials. Diffusion-tensor imaging (DTI) is one of the best-suited MRI techniques for assessing the extent of WM damage in the brain. But the optimal method to analyze individual DTI data remains hindered by labor-intensive and time-consuming processes. Peak width of skeletonized mean diffusivity (PSMD), a recently developed fast, fully automated DTI marker, was designed to quantify the WM damage secondary to cerebral SVD and reflect related cognitive impairment. Despite its promising results, knowledge about PSMD is still limited in the radiologic community. This focused review provides an overview of the technical details of PSMD while synthesizing the available data on its clinical and neuroimaging associations. From a critical expert viewpoint, the authors discuss the limitations of PSMD and its current validation status as a neuroimaging marker for vascular cognitive impairment. Finally, they point out the gaps to be addressed to further advance the field.

Effect of corticosubcortical iron deposition on dysfunction in CADASIL is mediated by white matter microstructural damage

Iron dysregulation may attenuate cognitive performance in patients with CADASIL. However, the underlying pathophysiological mechanisms remain incompletely understood. Whether white matter microstructural changes mediate these processes is largely unclear. In the present study, 30 cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) patients were confirmed via genetic analysis and 30 sex- and age-matched healthy controls underwent multimodal MRI examinations and neuropsychological assessments. Quantitative susceptibility mapping and peak width of skeletonized mean diffusivity (PSMD) were analyzed. Mediation effect analysis was performed to explore the interrelationship between iron deposition, white matter microstructural changes and cognitive deficits in CADASIL. Cognitive deterioration was most affected in memory and executive function, followed by attention and working memory in CADASIL. Excessive iron in the temporal-precuneus pathway and deep gray matter specific to CADASIL were identified. Mediation analysis further revealed that PSMD mediated the relationship between iron concentration and cognitive profile in CADASIL. The present findings provide a new perspective on iron deposition in the corticosubcortical circuit and its contribution to disease-related selective cognitive decline, in which iron concentration may affect cognition by white matter microstructural changes in CADASIL.

The gut microbiome is associated with markers of cerebral small vessel disease

AbstractBackgroundCerebral small vessel disease (cSVD) is a major cause of cognitive impairment and dementia in the elderly. Dysregulation of the gut microbiome has been linked to cSVD, stroke, and dementia in human and animal studies. However, whether dysbiosis is associated with markers of cSVD is unclear. We aimed to assess the cross‐sectional association between the gut microbiome and MRI markers of cSVD and executive function in the Framingham Heart Study (FHS).MethodWe included FHS participants from the Third‐generation cohort without a history of stroke or dementia. We estimated the gut microbiota composition using 16S rRNA gene sequencing. MRI markers of cSVD included white matter hyperintensities (WMH) and peak width of skeletonized mean diffusivity (PSMD). Executive function was assessed as the difference between the Trail Making Test (TMT) part B and A. We used multivariable regression analysis to evaluate the association between the gut microbiota and WMH, PSMD, and TMT, adjusting for age, age2, sex, BMI, and education. Additionally, we used differential abundance analysis to explore extremes of cSVD markers dichotomized by their distribution with the upper quintile representing the least healthy group. Finally, we used PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) to gain insight into the functional profiles of the underlying microbial communities.ResultOur sample included 972 participants (age: 55 ± 10 years, 56% female). Using multivariable models, we found that greater abundance of genera Pseudobutyrivibrio and Ruminococcus were associated with lower (healthier) WMH and PSMD (p‐values &lt; 0.001), as well as better executive function (p‐values &lt; 0.01). Furthermore, the differential analysis indicated a lower abundance of the genus Prevotella in the group of participants with the highest (least healthy) PSMD and WHM (p‐values &lt; 0.05). Finally, functional analyses using PICRUSt implicated various KEGG pathways, including carbohydrate metabolism, glycosaminoglycan, and fatty acid biosynthesis previously associated with cognitive performance.ConclusionOur study suggests abundance of certain gut bacteria in genus Pseudobutyrivibrio, Ruminococcus, and Prevotella, that produce butyric acid and other metabolites used by the human brain, are associated with healthier brain vasculature and better cognitive function in middle‐aged healthy adults.

Cerebrovascular injury markers explain the effect of systemic vascular risk on cognitive decline in older adults with lower amyloid burden

AbstractBackgroundSystemic vascular risk is a well‐established contributor to late‐life cognitive decline, yet the mechanism is not completely understood. We investigated whether neuroimaging‐based measures of vascular injury (white matter hyperintensity (WMH) volume, Peak width of Skeletonized Mean Diffusivity (PSMD), and relative cerebral blood flow (rCBF)) could explain the effect of systemic vascular risk on cognitive decline using longitudinal data from the Harvard Aging Brain Study.MethodWe used the Framingham Heart Study cardiovascular disease risk score (FHS‐CVD) as an index of systemic vascular risk. We extracted WMH from structural MRI (https://hypermapp3r.readthedocs.io/) and PSMD from diffusion MRI (http://www.psmdmarker.com). We performed kinetic modeling on dynamically‐acquired PiB‐PET data to extract 1) amyloid burden as the distribution volume ratio (PiB‐DVR) and 2) relative tracer delivery (PiB‐R1 via MRTM reference‐tissue analysis as a proxy of rCBF). Global cognition was assessed using Preclinical Alzheimer Cognitive Composite (PACC).We considered two linear mixed effect models to examine whether cerebrovascular injury markers could explain the FHS‐CVD effect on PACC change over time: 1) FHS‐CVD on PACC change controlling for age, sex, years of education, and PiB‐DVR; 2) the previous model including WMH, PSMD, and PIB‐R1. Analyses were stratified by high (PiB+) and low (PiB‐) baseline amyloid burden.ResultFigure 1 illustrates the relationships between demographics and neuroimaging measures at baseline. Table 1 shows the demographics and study information. We observed a significant effect of FHS‐CVD on PACC change (PiB‐: t=‐3.9, p&lt;0.001 (Table 2); PiB+: t=‐2.6, p=0.008). When the cerebrovascular injury markers were included in the model, the effect of FHS‐CVD was reduced in the PiB‐ group while PSMD and PiB‐R1 explained PACC change (Table 3; Figure 2). The second model fit was significantly better than the first model (L.ratio= 25.9, p&lt;0.001). The effects remained significant after controlling for gray matter volume. In contrast, cerebrovascular injury measures did not explain the effect of FHS‐CVD on PACC change in the PIB+ group.ConclusionThese results demonstrate that cerebrovascular injury largely explains the effect of systemic vascular risk on cognitive decline in older adults with lower amyloid burden suggesting mechanisms by which a higher systemic vascular risk impacts brain function.

Albuminuria, cognition, and MRI biomarkers of cerebrovascular disease in American Indians of the Zuni Pueblo.

Elevated urine albumin to creatinine ratio (UACR) is associated with cerebrovascular disease and cognitive impairment in older adults, though few studies have evaluated these relationships in midlife. This is particularly important to assess in American Indian populations, which are disproportionately impacted by diabetes and kidney disease. Additionally, evidence suggests that biomarkers may perform differently in underrepresented groups, thus, it is crucial to validate biomarkers in this unique population. Twenty-five participants from the Zuni Pueblo underwent neuropsychological assessment and an MRI that included fluid attenuated inversion recovery (FLAIR) and diffusion imaging to calculate recently developed MRI markers of cerebrovascular small vessel disease (Peak width of Skeletonized Mean Diffusivity (PSMD), mean free-water fraction (mFW), white matter hyperintensity (WMH)). Regression analyses indicated no significant associations between UACR, MRI biomarkers and cognitive outcomes. Analyses of covariance indicated that the Zuni Indian cohort exhibited reduced white matter damage relative to an existing cohort of older adults with vascular cognitive impairment when accounting for age, sex, and education. Slower processing speed was associated with greater white matter disease across all measures examined. Our pilot study validated the use of MRI biomarkers of cerebrovascular disease in this unique cohort of American Indians.