The relation between vascular risk factors and flow in cerebral perforating arteries. A 7 Tesla MRI study.

INTRODUCTION: Cerebral perforating arteries provide blood supply to the deep regions of the brain. Recently, it became possible to measure blood flow velocity and pulsatility in these small arteries. It is unknown if vascular risk factors are related to these measures. METHODS: We measured perforating artery flow with 2D phase contrast 7 Tesla MRI at the level of the centrum semiovale (CSO) and the basal ganglia (BG) in seventy participants from the Heart Brain Connection study with carotid occlusive disease (COD), vascular cognitive impairment (VCI), or no actual cerebrovascular disease. Vascular risk factors included hypertension, diabetes, hyperlipidemia and smoking. RESULTS: No consistent relations were found between any of the vascular risk factors and either flow velocity or flow pulsatility, although there was a relation between lower diastolic blood pressure and higher pulse pressure and higher cerebral perforator pulsatility (p=0,045 and p=0,044, respectively) at the BG level. Results were similar in stratified analyses for patients with and without a history of cardiovascular disease, or only COD or VCI. CONCLUSION: We conclude that, cross-sectionally, cerebral perforating artery flow velocity and pulsatility are largely independent of the presence of common vascular risk factors in a population with a mixed vascular burden.

Association Between Cerebral Cortical Microinfarcts and Perilesional Cortical Atrophy on 3T MRI.

BACKGROUND AND OBJECTIVES: Cerebral cortical microinfarcts (CMIs) are a novel MRI marker of cerebrovascular disease (CeVD) that predicts accelerated cognitive decline. Presence of CMIs is known to be associated with global cortical atrophy, although the mechanism linking the two is unclear. Our primary objective was to examine the relation between CMIs and cortical atrophy and to establish possible perilesional atrophy surrounding CMIs. Our secondary objective was to examine the role of cortical atrophy in CMI-associated cognitive impairment. METHODS: Patients were recruited from 2 Singapore memory clinics between December 2010 and September 2013 and included if they received the diagnosis no objective cognitive impairment, cognitive impairment (with or without a history of stroke), or Alzheimer or vascular dementia. Cortical thickness, chronic CMIs, and MRI markers of CeVD were assessed on 3T MRI. Patients underwent cognitive testing. Cortical thickness was compared globally between patients with and without CMIs, regionally within individual patients with CMIs comparing brain regions with CMIs to the corresponding contralateral region without CMIs, and locally within individuals patients in a 50-mm radius of CMIs. Global cortical thickness was analyzed as mediator in the relation between CMI and cognitive performance. RESULTS: Of the 238 patients (mean age 72.5 years, SD 9.1 years) enrolled, 75 had ≥1 CMIs. Patient with CMIs had a 2.1% lower global cortical thickness (B = -0.049 mm, 95% confidence interval [CI] 0.091 to -0.007, p = 0.022) compared to patients without CMIs, after correction for age, sex, education, and intracranial volume. In patients with CMIs, cortical thickness in brain regions with CMIs was 2.2% lower than in contralateral regions without CMIs (B = -0.048 mm [95% CI -0.071 to -0.026], p < 0.001). In a 20-mm radius area surrounding the CMI core, cortical thickness was lower than in the area 20 to 50 mm from the CMI core (mean difference -0.06 mm [-0.10 to -0.02], p = 0.002). Global cortical thickness was a significant mediator in the relationship between CMI presence and cognitive performance as measure with the Mini-Mental State Examination (B = -0.12 [-0.22 to -0.01], p = 0.025). DISCUSSION: We found cortical atrophy surrounding CMIs, suggesting a perilesional effect in a cortical area many times larger than the CMI core. Our findings support the notion that CMIs affect brain structure beyond the actual lesion site.

Cerebral cortical microinfarcts in patients with internal carotid artery occlusion.

Cerebral cortical microinfarcts (CMI) are small ischemic lesions that are associated with cognitive impairment and probably have multiple etiologies. Cerebral hypoperfusion has been proposed as a causal factor. We studied CMI in patients with internal carotid artery (ICA) occlusion, as a model for cerebral hemodynamic compromise. We included 95 patients with a complete ICA occlusion (age 66.2 ± 8.3, 22% female) and 125 reference participants (age 65.5 ± 7.4, 47% female). Participants underwent clinical, neuropsychological, and 3 T brain MRI assessment. CMI were more common in patients with an ICA occlusion (54%, median 2, range 1-33) than in the reference group (6%, median 0; range 1-7; OR 14.3; 95% CI 6.2-33.1; p<.001). CMI were more common ipsilateral to the occlusion than in the contralateral hemisphere (median 2 and 0 respectively; p<.001). In patients with CMI compared to patients without CMI, the number of additional occluded or stenosed cervical arteries was higher (p=.038), and cerebral blood flow was lower (B -6.2 ml/min/100 ml; 95% CI -12.0:-0.41; p=.036). In conclusion, CMI are common in patients with an ICA occlusion, particularly in the hemisphere of the occluded ICA. CMI burden was related to the severity of cervical arterial compromise, supporting a role of hemodynamics in CMI etiology.

The Effects of Intracranial Stenosis on Cerebral Perfusion and Cognitive Performance.

BACKGROUND: Intracranial stenosis (ICS) may contribute to cognitive dysfunction by decreased cerebral blood flow (CBF) which can be measured quantitatively by arterial spin labelling (ASL). Interpretation of CBF measurements with ASL, however, becomes difficult in patients with vascular disease due to prolonged arterial transit time (ATT). Recently, spatial coefficient of variation (sCoV) of ASL signal has been proposed that approximates ATT and utilized as a proxy marker for assessment of hemodynamic status of cerebral circulation. OBJECTIVE: We investigate the association of ICS with CBF and sCoV parameters and its eventual effects on cognition in a memory clinic population. METHODS: We included 381 patients (mean age = 72.3±7.9 years, women = 53.7%) who underwent 3T MRI and detailed neuropsychological assessment. ICS was defined as≥50% stenosis in any intracranial vessel on 3D Time-of-Flight MR Angiography. Gray matter sCoV and CBF were obtained from 2D EPI pseudo-continuous ASL images. RESULTS: ICS was present in 58 (15.2%) patients. Patients with ICS had higher gray matter sCoV and lower CBF. The association with sCoV remained statistically significant after correction for cardiovascular risk factors. Moreover, ICS was associated with worse performance on visuoconstruction, which attenuated with higher sCoV. Mediation analysis showed that there was an indirect effect of ICS on visuoconstruction via sCoV. CONCLUSION: These findings suggest that compromised CBF as detected by higher sCoV is related to cognitive impairment among individuals diagnosed with ICS. We also showed that sCoV partially mediates the link between ICS and cognition. Therefore, sCoV may provide valuable hemodynamic information in patients with vascular disease.

Cerebral cortical microinfarcts: A novel MRI marker of vascular brain injury in patients with heart failure.

BACKGROUND: Patients with heart failure (HF) are at risk for vascular brain injury. Cerebral cortical microinfarcts (CMIs) are a novel MRI marker of vascular brain injury. This study aims to determine the occurrence of CMIs in patient with HF and their clinical correlates, including haemodynamic status. METHODS: From the Heart-Brain Study, a multicenter prospective cohort study, 154 patients with clinically stable HF without concurrent atrial fibrillation (mean age 69.5 ± 10.1, 32% female) and 124 reference participants without HF (mean age 65.6 ± 7.4, 47% females) were evaluated for CMIs on 3 T MRI. CMI presence in HF was tested for associations with vascular risk profile, cardiac function and history, MRI markers of vascular brain injury and cognitive profile. RESULTS: CMI occurrence was higher in patient with HF (17%) than reference participants (7%); after correction for age and sex OR 2.5 [95% CI 1.1-6.0] p = .032; after additional correction for vascular risk factors OR 2.7 [1.0-7.1] p = .052. In patients with HF, CMI presence was associated with office hypertension (OR 2.7 [1.2-6.5] p = .021) and a lower cardiac index (B = -0.29 [-0.55--0.04] p = .023 independent of vascular risk factors), but not with cause or duration of HF. Presence of CMIs was not associated with cognitive performance in patients with HF. CONCLUSIONS: CMIs are a common occurrence in patients with HF and related to an adverse vascular risk factor profile and severity of cardiac dysfunction. CMIs thus represent a novel marker of vascular brain injury in these patients.

Cortical microinfarcts in memory clinic patients are associated with reduced cerebral perfusion.

Cerebral cortical microinfarcts (CMIs) are small ischemic lesions associated with cognitive impairment and dementia. CMIs are frequently observed in cortical watershed areas suggesting that hypoperfusion contributes to their development. We investigated if presence of CMIs was related to a decrease in cerebral perfusion, globally or specifically in cortex surrounding CMIs. In 181 memory clinic patients (mean age 72 ± 9 years, 51% male), CMI presence was rated on 3-T magnetic resonance imaging (MRI). Cerebral perfusion was assessed from cortical gray matter of the anterior circulation using pseudo-continuous arterial spin labeling parameters cerebral blood flow (CBF) (perfusion in mL blood/100 g tissue/min) and spatial coefficient of variation (CoV) (reflecting arterial transit time (ATT)). Patients with CMIs had a 12% lower CBF (beta = -.20) and 22% higher spatial CoV (beta = .20) (both p < .05) without a specific regional pattern on voxel-based CBF analysis. CBF in a 2 cm region-of-interest around the CMIs did not differ from CBF in a reference zone in the contralateral hemisphere. These findings show that CMIs in memory clinic patients are primarily related to global reductions in cerebral perfusion, thus shedding new light on the etiology of vascular brain injury in dementia.

Cortical Microinfarcts and White Matter Connectivity in Memory Clinic Patients.

Background and purpose: Cerebral microinfarcts (CMIs) are associated with cognitive impairment and dementia. CMIs might affect cognitive performance through disruption of cerebral networks. We investigated in memory clinic patients whether cortical CMIs are clustered in specific brain regions and if presence of cortical CMIs is associated with reduced white matter (WM) connectivity in tracts projecting to these regions. Methods:164 memory clinic patients with vascular brain injury with a mean age of 72 ± 11 years (54% male) were included. All underwent 3 tesla MRI, including a diffusion MRI and cognitive testing. Cortical CMIs were rated according to established criteria and their spatial location was marked. Diffusion imaging-based tractography was used to reconstruct WM connections and voxel based analysis (VBA) to assess integrity of WM directly below the cortex. WM connectivity and integrity were compared between patients with and without cortical CMIs for the whole brain and regions with a high CMI burden. Results:30 patients (18%) had at least 1 cortical CMI [range 1-46]. More than 70% of the cortical CMIs were located in the superior frontal, middle frontal, and pre- and postcentral brain regions (covering 16% of the cortical surface). In these high CMI burden regions, presence of cortical CMIs was not associated with WM connectivity after correction for conventional neuroimaging markers of vascular injury. WM connectivity in the whole brain and WM voxels directly underneath the cortical surface did not differ between patients with and without cortical CMIs. Conclusion:Cortical CMIs displayed a strong local clustering in highly interconnected frontal, pre- and postcentral brain regions. Nevertheless, WM connections projecting to these regions were not disproportionally impaired in patients with compared to patients without cortical CMIs. Alternative mechanisms, such as focal disturbances in cortical structure and functioning, may better explain CMI associated cognitive impairment.

Clinical relevance of acute cerebral microinfarcts in vascular cognitive impairment.

OBJECTIVE: To determine the occurrence of acute cerebral microinfarcts (ACMIs) in memory clinic patients and relate their presence to vascular risk and cognitive profile, CSF and neuroimaging markers, and clinical outcome. METHODS: The TRACE-VCI study is a memory clinic cohort of patients with vascular brain injury on MRI (i.e., possible vascular cognitive impairment [VCI]). We included 783 patients (mean age 67.6 ± 8.5, 46% female) with available 3T diffusion-weighted imaging (DWI). ACMIs were defined as supratentorial DWI hyperintensities <5 mm with a corresponding hypo/isointense apparent diffusion coefficient signal and iso/hyperintense T2*-weighted signal. RESULTS: A total of 23 ACMIs were found in 16 of the 783 patients (2.0%). Patients with ACMIs did not differ in vascular risk or cognitive profile, but were more often diagnosed with vascular dementia (odds ratio [OR] 5.1; 95% confidence interval [CI] 1.4-18.9, p = 0.014). ACMI presence was associated with lower levels of ß-amyloid (p < 0.004) and with vascular imaging markers (lacunar infarcts: OR 3.5, CI 1.3-9.6, p = 0.015; nonlacunar infarcts: OR 4.1, CI 1.4-12.5, p = 0.012; severe white matter hyperintensities: OR 4.8, CI 1.7-13.8, p = 0.004; microbleeds: OR 18.9, CI 2.5-144.0, p = 0.0001). After a median follow-up of 2.1 years, the risk of poor clinical outcome (composite of marked cognitive decline, major vascular event, death, and institutionalization) was increased among patients with ACMIs (hazard ratio 3.0; 1.4-6.0, p = 0.005). CONCLUSION: In patients with possible VCI, ACMI presence was associated with a high burden of cerebrovascular disease of both small and large vessel etiology and poor clinical outcome. ACMIs may thus be a novel marker of active vascular brain injury in these patients.

Design of the ExCersion-VCI study: The effect of aerobic exercise on cerebral perfusion in patients with vascular cognitive impairment.

There is evidence for a beneficial effect of aerobic exercise on cognition, but underlying mechanisms are unclear. In this study, we test the hypothesis that aerobic exercise increases cerebral blood flow (CBF) in patients with vascular cognitive impairment (VCI). This study is a multicenter single-blind randomized controlled trial among 80 patients with VCI. Most important inclusion criteria are a diagnosis of VCI with Mini-Mental State Examination ≥22 and Clinical Dementia Rating ≤0.5. Participants are randomized into an aerobic exercise group or a control group. The aerobic exercise program aims to improve cardiorespiratory fitness and takes 14 weeks, with a frequency of three times a week. Participants are provided with a bicycle ergometer at home. The control group receives two information meetings. Primary outcome measure is change in CBF. We expect this study to provide insight into the potential mechanism by which aerobic exercise improves hemodynamic status.

Cortical Cerebral Microinfarcts on 3 Tesla MRI in Patients with Vascular Cognitive Impairment.

BACKGROUND: Cerebral microinfarcts (CMIs) are small ischemic lesions that are a common neuropathological finding in patients with stroke or dementia. CMIs in the cortex can now be detected in vivo on 3 Tesla MRI. OBJECTIVE: To determine the occurrence of CMIs and associated clinical features in patients with possible vascular cognitive impairment (VCI). METHOD: 182 memory-clinic patients (mean age 71.4±10.6, 55% male) with vascular injury on brain MRI (i.e., possible VCI) underwent a standardized work-up including 3 Tesla MRI and cognitive assessment. A control group consisted of 70 cognitively normal subjects (mean age 70.6±4.7, 60% male). Cortical CMIs and other neuroimaging markers of vascular brain injury were rated according to established criteria. RESULT: Occurrence of CMIs was higher (20%) in patients compared to controls (10%). Among patients, the presence of CMIs was associated with male sex, history of stroke, infarcts, and white matter hyperintensities. CMI presence was also associated with a diagnosis of vascular dementia and reduced performance in multiple cognitive domains. CONCLUSION: CMIs on 3 Tesla MRI are common in patients with possible VCI and co-occur with imaging markers of small and large vessel disease, likely reflecting a heterogeneous etiology. CMIs are associated with worse cognitive performance, independent of other markers of vascular brain injury.

The Effects of Physical Activity and Fitness in Adolescence on Cognition in Adulthood and the Role of Insulin-Like Growth Factor I.

BACKGROUND: Physical activity and fitness in adolescence may improve cognition in adulthood by increasing insulin-like growth factor I (IGF-I). METHODS: As part of the Amsterdam Growth and Health Longitudinal Study, following subjects from age 13 to 42 years, physical activity and fitness of 303 subjects were assessed annually between the ages 13 to 16. At mean age 36, physical activity, fitness and IGF-I were measured. At mean age 42, IGF-I and cognitive factors (ie, executive functioning and visual-spatial memory) were measured. The linear regression of physical activity and fitness in adolescence and IGF-I in adulthood on cognitive scores in adulthood was investigated. RESULTS: A significant association was found in males between physical activity in adolescence and executive function in adulthood (Spatial Working Memory Between Errors: ß = -.18, B = -.13, 95% CI = -.259 to -.010; Spatial Working Memory Strategy: ß = -.20, B = -.08, 95% CI = -.147 to -.014). No association between physical activity or fitness in adolescence and cognitive function in adulthood was found in females, nor any intermediate role for IGF-I in either sex. CONCLUSIONS: The results suggest a stimulating effect of adolescent physical activity in males on executive functions in adulthood, emphasizing the importance of an active lifestyle among adolescent males.