Longitudinal Changes in Global Cerebral Blood Flow in Cognitively Normal Older Adults: A Phase-Contrast MRI Study

Distribution of Silent Cerebral Infarcts in Adults With Sickle Cell Disease

BACKGROUND AND OBJECTIVES

Previously we demonstrated that 90% of infarcts in children with sickle cell anemia occur in the border zone regions of cerebral blood flow (CBF). We tested the hypothesis that adults with sickle cell disease (SCD) have silent cerebral infarcts (SCIs) in the border zone regions, with a secondary hypothesis that older age and traditional stroke risk factors would be associated with infarct occurrence in regions outside the border zones.

METHODS

Adults with SCD 18-50 years of age were enrolled in a cross-sectional study at 2 centers and completed a 3T brain MRI. Participants with a history of overt stroke were excluded. Infarct masks were manually delineated on T2-fluid-attenuated inversion-recovery MRI and registered to the Montreal Neurological Institute 152 brain atlas to generate an infarct heatmap. Border zone regions between anterior, middle, and posterior cerebral arteries (ACA, MCA, and PCA) were quantified using the Digital 3D Brain MRI Arterial Territories Atlas, and logistic regression was applied to identify relationships between infarct distribution, demographics, and stroke risk factors.

RESULTS

Of 113 participants with SCD (median age 26.1 years, interquartile range [IQR] 21.6-31.4 years, 51% male), 56 (49.6%) had SCIs. Participants had a median of 5.5 infarcts (IQR 3.2-13.8). Analysis of infarct distribution showed that 350 of 644 infarcts (54.3%) were in 4 border zones of CBF and 294 (45.6%) were in non-border zone territories. More than 90% of infarcts were in 3 regions: the non-border zone ACA and MCA territories and the ACA-MCA border zone. Logistic regression showed that older participants have an increased chance of infarcts in the MCA territory (odds ratio [OR] 1.08; 95% CI 1.03-1.13; p = 0.001) and a decreased chance of infarcts in the ACA-MCA border zone (OR 0.94; 95% CI 0.90-0.97; p < 0.001). The presence of at least 1 stroke risk factor did not predict SCI location in any model.

DISCUSSION

When compared with children with SCD, in adults with SCD, older age is associated with expanded zones of tissue infarction that stretch beyond the traditional border zones of CBF, with more than 45% of infarcts in non-border zone regions.

Association of Carotid Plaque and Flow Velocity With White Matter Integrity in a Middle-aged to Elderly Population

BACKGROUND AND OBJECTIVES

It is uncertain whether there is an association of carotid plaques (CPs) and flow velocities with peak width mean diffusivity (PSMD) and white matter hyperintensities (WMH) independent of shared risk factors. We aimed to study this association controlling for biomarkers of inflammation and cardiac dysfunction and typical cardiovascular risk factors and spatial distribution.

METHODS

We included participants from the population-based Hamburg City Health Study, recruiting citizens between 45 and 74 years of age. Medical history was obtained from structured interviews and extended laboratory tests, physical examinations, MRI of the head, echocardiography, and abdominal and carotid ultrasound were performed. We performed multivariable regression analysis with PSMD and periventricular, deep, and total volume of WMH (pWMH, dWMH, tWMH) as dependent variables. PSMD was calculated as the difference between the 95th and 5th percentiles of MD values on the white skeleton in standard space. Volumes of WMH were determined by the application of a manually trained k-nearest neighbor segmentation algorithm. WMH measured within a distance of 1 cm from the surface of the lateral ventricles were defined as pWMH and above 1 cm as dWMH.

RESULTS

Two thousand six hundred twenty-three participants were included. The median age was 65 years, and 56% were women. Their median tWMH was 946 mm3(IQR:419, 2,164), PSMD 2.24 mm2/s × 10-4 (IQR: 2.04, 2.47), peak systolic velocity (PSV) of internal carotid arteries 0.70m/second (IQR:0.60, 0.81), and 35% had CPs. Adjusted for age, sex, high-sensitive CRP, NT-proBNP, and commonly measured cardiovascular risk and systemic hemodynamic factors, both CPs (B = 0.15; CI: 0.04, 0.26; p = 0.006) and low PSV (B = -0.49; CI: -0.87, -0.11; p = 0.012) were significantly associated with a higher tWMH and PSMD. Low PSV (B = -0.48; CI: -0.87, -0.1; p = 0.013) was associated with pWMH and the presence of CP with pWMH (B = 0.15; CI: 0.04, 0.26; p = 0.008) and dWMH (B = 0.42; CI: 0.11, 0.74; p < 0.009).

DISCUSSION

Low PSV and CP are associated with WMH and PSMD independent of cardiovascular risk factors and biomarkers of inflammation and cardiac dysfunction. This points toward pathophysiologic pathways underlying both large and small vessel disease beyond the common cardiovascular risk profile.

TRIAL REGISTRATION INFORMATION

The trial was submitted at clinicaltrials.gov, under NCT03934957 on January 4, 2019. The first participant was enrolled in February 2016.

Associations between cerebral blood flow and progression of white matter hyperintensity in community-dwelling adults: a longitudinal cohort study

Background

White matter hyperintensity (WMH) is prevalent in elderly populations. Ischemia is characterized by a decline in cerebral blood flow (CBF) and may play a key role in the pathogenesis of WMH. However, the association between CBF reduction and WMH progression remains controversial. This study aimed to investigate the association between CBF and the progression of WMH at a 2-year follow-up of community-based, asymptomatic adults in a longitudinal cohort study across the lifespan.

Methods

Asymptomatic adults who participated in a community-based study were recruited and underwent brain structural and perfusion magnetic resonance imaging (MRI) at baseline and at a 2-year follow-up visit. The CBF was measured on pseudo-continuous arterial spin-labeling (pCASL) MRI. The WMH was evaluated on T2-weighted fluid-attenuated inversion recovery (T2-FLAIR) images. Tissue segmentation was conducted on T1-weighted (T1W) images to derive binary masks of gray matter and normal-appearing white matter. Linear mixed effect models were conducted to analyze the cross-sectional and longitudinal associations between CBF and WMH.

Results

A total of 229 adults (mean age 57.3±12.6 years; 94 males) were enrolled at baseline, among whom 84 participants (mean age 54.1±11.9 years; 41 males) completed a follow-up visit with a mean time interval of 2.77±0.44 years. At baseline, there was a decreasing trend in gray matter (GM) CBF with an increase of WMH burden (P=0.063), but this association was attenuated after adjusting for age (P=0.362). In the longitudinal analysis, baseline WMH volume was significantly associated with the reduction of perfusion in GM [coefficient =−1.96, 95% confidence interval (CI): −3.25 to −0.67; P=0.004] and normal appearing white matter (coefficient =−0.99, 95% CI: −1.66 to −0.31; P=0.005) during follow-up. On the contrary, neither baseline CBF in GM (P=0.888) nor normal appearing white matter (P=0.850) was associated with WMH progression. In addition, CBF changes within WMH were significantly associated with both baseline (coefficient =−0.014, 95% CI: −0.025 to −0.003; P=0.017) and progression (coefficient =−1.01, 95% CI: −1.81 to −0.20; P=0.015) of WMH volume.

Conclusions

A WMH burden was not found to be directly associated with cortex perfusion at baseline due to the effects of age on both CBF and WMH. However, baseline WMH volume could predict the reduction of perfusion.