Serial susceptibility weighted MRI measures brain iron and microbleeds in dementia

Cerebral Amyloid Angiopathy in Patients with Cognitive Impairment: Cerebrospinal Fluid Biomarkers

INTRODUCTION

Cerebral amyloid angiopathy (CAA) is characterized by amyloid β (Aβ) deposition in brain vessels, leading to hemorrhagic phenomena and cognitive impairment. Magnetic resonance imaging (MRI)-based criteria allow a diagnosis of probable CAA in vivo, but such a diagnosis cannot predict the eventual development of CAA.

METHODS

We conducted a retrospective cohort study of 464 patients with cognitive disorders whose data were included in a brain health biobank. De-identified parameters including sex, age, cognitive score, APOE status, and cerebrospinal fluid (CSF) levels of Aβ 1-40, Aβ 1-42, phosphorylated tau, and total tau were assessed in those with and without CAA. Odds ratios (ORs) and 95% confidence intervals (CIs) were determined.

RESULTS

CAA was present in 53 of 464 (11.5%) patients. P-tau level was significantly higher in those with CAA (115 vs. 84.3 pg/mL p = 0.038). In univariate analyses, the risk of developing CAA was higher with increased age (OR, 1.036; 95% CI: 1.008, 1.064; p = 0.011) and decreased CSF level of Aβ 1-40 (OR, 0.685; 95% CI: 0.534, 0.878; p = 0.003). In multivariate analyses, the risk of CAA remained higher with a decreased CSF level of Aβ 1-40 (OR, 0.681; 95% CI: 0.531, 0.874; p = 0.003).

CONCLUSION

These findings suggest that Aβ 1-40 levels in the CSF might be a useful molecular biomarker of CAA in patients with dementia.

CD59 Protects Primary Human Cerebrovascular Smooth Muscle Cells from Cytolytic Membrane Attack Complex

Cerebral amyloid angiopathy is characterized by a weakening of the small- and medium-sized cerebral arteries, as their smooth muscle cells are progressively replaced with acellular amyloid β, increasing vessel fragility and vulnerability to microhemorrhage. In this context, an aberrant overactivation of the complement system would further aggravate this process. The surface protein CD59 protects most cells from complement-induced cytotoxicity, but expression levels can fluctuate due to disease and varying cell types. The degree to which CD59 protects human cerebral vascular smooth muscle (HCSM) cells from complement-induced cytotoxicity has not yet been determined. To address this shortcoming, we selectively blocked the activity of HCSM-expressed CD59 with an antibody, and challenged the cells with complement, then measured cellular viability. Unblocked HCSM cells proved resistant to all tested concentrations of complement, and this resistance decreased progressively with increasing concentrations of anti-CD59 antibody. Complete CD59 blockage, however, did not result in a total loss of cellular viability, suggesting that additional factors may have some protective functions. Taken together, this implies that CD59 plays a predominant role in HCSM cellular protection against complement-induced cytotoxicity. The overexpression of CD59 could be an effective means of protecting these cells from excessive complement system activity, with consequent reductions in the incidence of microhemorrhage. The precise extent to which cellular repair mechanisms and other complement repair proteins contribute to this resistance has yet to be fully elucidated.

CD59 Protects Primary Human Cerebrovascular Smooth Muscle Cells from Cytolytic Membrane Attack Complex

Cerebral amyloid angiopathy is characterized by a weakening of the small and medium sized cerebral arteries, as their smooth muscle cells are progressively replaced with acellular amyloid β, increasing vessel fragility and vulnerability to microhemorrhage. In this context, an aberrant overactivation of the complement system would further aggravate this process. The surface protein CD59 protects most cells from complement-induced cytotoxicity, but expression levels can fluctuate due to disease and vary between cell types. The degree to which CD59 protects human cerebral vascular smooth muscle (HCSM) cells from complement-induced cytotoxicity has not yet been determined. To address this shortcoming, we selectively blocked the activity of HCSM-expressed CD59 with an antibody and challenged the cells with complement, then measured cellular viability. Unblocked HCSM cells proved resistant to all tested concentrations of complement, and this resistance decreased progressively with increasing concentrations of anti-CD59 antibody. Complete CD59 blockage, however, did not result in total loss of cellular viability, suggesting that additional factors may have some protective functions. Taken together, this implies that CD59 plays a predominant role in HCSM cellular protection against complement-induced cytotoxicity. Over-expression of CD59 could be an effective means of protecting these cells from excessive complement system activity, with consequent reduction in the incidence of microhemorrhage. The precise extent to which cellular repair mechanisms and other complement repair proteins contribute to this resistance has yet to be fully elucidated.

Prevalence of cerebral microbleeds in Alzheimer's disease, dementia with Lewy bodies and Parkinson's disease dementia: A systematic review and meta-analysis

Cerebral microbleeds (CMB) are often associated with vascular risk factors and/or cerebral amyloid angiopathy and are frequently identified in people with dementia. The present study therefore aimed to estimate the pooled prevalence and associations of CMB in Alzheimer's disease (AD), dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD), using meta-analytic methods. Sixty-five MRI studies were included after a systematic search on major electronic databases. We found that the prevalence of CMB was comparable across the three dementia subtypes (31-36%) and was highly influenced by the MRI techniques used. CMB in AD were associated with a history of hypertension and amyloid-β burden. In contrast, CMB in DLB, despite being predominantly lobar, were associated with hypertension, but not amyloid-β burden. These findings suggest that the underlying pathophysiology of CMB in DLB might differ from that of AD. There was substantially larger number of AD studies identified and more studies evaluating CMB in Lewy body dementias are warranted.

Imaging spectrum of amyloid-related imaging abnormalities associated with aducanumab immunotherapy

Alzheimer's Disease (AD) is a leading cause of morbidity. Management of AD has traditionally been aimed at symptom relief rather than disease modification. Recently, AD research has begun to shift focus towards disease-modifying therapies that can alter the progression of AD. In this context, a class of immunotherapy agents known as monoclonal antibodies target diverse cerebral amyloid-beta (Aβ) epitopes to inhibit disease progression. Aducanumab was authorized by the US Food and Drug Administration (FDA) to treat AD on June 7, 2021. Aducanumab has shown promising clinical and biomarker efficacy but is associated with amyloid-related imaging abnormalities (ARIA). Neuroradiologists play a critical role in diagnosing ARIA, necessitating familiarity with this condition. This pictorial review will appraise the radiologic presentation of ARIA in patients on aducanumab.

Amyloid-related Imaging Abnormalities in Alzheimer Disease Treated with Anti-Amyloid-β Therapy

Alzheimer disease (AD) is the most common form of dementia worldwide. Treatment of AD has mainly been focused on symptomatic treatment until recently with the advent and approval of monoclonal antibody (MAB) immunotherapy. U.S. Food and Drug Administration-approved drugs such as aducanumab, as well as upcoming newer-generation drugs, have provided an exciting new therapy focused on reducing the amyloid plaque burden in AD. Although this new frontier has shown benefits for patients, it is not without complications, which are mainly neurologic. Increased use of MABs led to the discovery of amyloid-related imaging abnormalities (ARIA). ARIA has been further classified into two categories, ARIA-E and ARIA-H, representing edema and/or effusion and hemorrhage, respectively. ARIA is thought to be caused by increased vascular permeability following an inflammatory response, leading to the extravasation of blood products and proteinaceous fluid. Patients with ARIA may present with headaches, but they are usually asymptomatic and ARIA is only diagnosable at MRI; it is essential for the radiologist to recognize and monitor ARIA. Increased incidence and investigation into this concern have led to the creation of grading scales and monitoring guidelines to diagnose and guide treatment using MABs. Cerebral amyloid angiopathy has an identical pathogenesis to that of ARIA and is its closest differential diagnosis, with imaging findings being the same for both entities and only a history of MAB administration allowing differentiation. The authors discuss the use of MABs for treating AD, expand on ARIA and its consequences, and describe how to identify and grade ARIA to guide treatment properly. ©RSNA, 2023 Quiz questions for this article are available through the Online Learning Center See the invited commentary by Yu in this issue.

Epidemiology of Motoric Cognitive Risk Syndrome in the Kerala Einstein Study: Protocol for a Prospective Cohort Study

BACKGROUND

The southern India state of Kerala has among the highest proportion of older adults in its population in the country. An increase in chronic age-related diseases such as dementia is expected in the older Kerala population. Identifying older individuals early in the course of cognitive decline offers the best hope of introducing preventive measures early and planning management. However, the epidemiology and pathogenesis of predementia syndromes at the early stages of cognitive decline in older adults are not well established in India.

OBJECTIVE

The Kerala Einstein Study (KES) is a community-based cohort study that was established in 2008 and is based in the Kozhikode district in Kerala state. KES aims to establish risk factors and brain substrates of motoric cognitive risk syndrome (MCR), a predementia syndrome characterized by the presence of slow gait and subjective cognitive concerns in individuals without dementia or disability. This protocol describes the study design and procedures for this KES project.

METHODS

KES is proposing to enroll a sample of 1000 adults ≥60 years old from urban and rural areas in the Kozhikode district of Kerala state: 200 recruited in the previous phase of KES and 800 new participants to be recruited in this project. MCR is the cognitive phenotype of primary interest. The associations between previously established risk factors for dementia as well as novel risk factors (apathy and traumatic brain injury) and MCR will be examined in KES. Risk factor profiles for MCR will be compared between urban and rural residents as well as with individuals who meet the criteria for mild cognitive impairment (MCI). Cognitive and physical function, medical history and medications, sociodemographic characteristics, lifestyle patterns, and activities of daily living will be evaluated. Participants will also undergo magnetic resonance imaging and electrocardiogram investigations. Longitudinal follow-up is planned in a subset of participants as a prelude to future longitudinal studies.

RESULTS

KES (2R01AG039330-07) was funded by the US National Institutes of Health in September 2019 and received approval from the Indian Medical Council of Research to start the study in June 2021. We had recruited 433 new participants from urban and rural sites in Kozhikode as of May 2023: 41.1% (178/433) women, 67.7% (293/433) rural residents, and 13.4% (58/433) MCR cases. Enrollment is actively ongoing at all the KES recruitment sites.

CONCLUSIONS

KES will provide new insights into risk factors and brain substrates associated with MCR in India and will help guide future development of regionally specific preventive interventions for dementia.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/49933.

Cell specificity of Manganese-enhanced MRI signal in the cerebellum

Magnetic Resonance Imaging (MRI) resolution continues to improve, making it important to understand the cellular basis for different MRI contrast mechanisms. Manganese-enhanced MRI (MEMRI) produces layer-specific contrast throughout the brain enabling in vivo visualization of cellular cytoarchitecture, particularly in the cerebellum. Due to the unique geometry of the cerebellum, especially near the midline, 2D MEMRI images can be acquired from a relatively thick slice by averaging through areas of uniform morphology and cytoarchitecture to produce very high-resolution visualization of sagittal planes. In such images, MEMRI hyperintensity is uniform in thickness throughout the anterior-posterior axis of sagittal sections and is centrally located in the cerebellar cortex. These signal features suggested that the Purkinje cell layer, which houses the cell bodies of the Purkinje cells and the Bergmann glia, is the source of hyperintensity. Despite this circumstantial evidence, the cellular source of MRI contrast has been difficult to define. In this study, we quantified the effects of selective ablation of Purkinje cells or Bergmann glia on cerebellar MEMRI signal to determine whether signal could be assigned to one cell type. We found that the Purkinje cells, not the Bergmann glia, are the primary of source of the enhancement in the Purkinje cell layer. This cell-ablation strategy should be useful for determining the cell specificity of other MRI contrast mechanisms.

Do cerebral microbleeds increase the risk of dementia? A systematic review and meta-analysis

Background

Dementia is a neurological disorder that commonly affects the elderly. Cerebral microbleeds (CMBs) are small, tiny lesions of the cerebral blood vessels and have been suggested as a possible risk factor for dementia. However, data about the association between CMBs and dementia risk are inconsistent and inconclusive. Therefore, we conducted this systematic review and meta-analysis to investigate the association between CMBs and dementia and highlight the possible explanations.

Methods

We followed the standard PRISMA statement and the Cochrane Handbook guidelines to conduct this study. First, we searched medical electronic databases for relevant articles. Then, we screened the retrieved articles for eligibility, extracted the relevant data, and appraised the methodological quality using the Newcastle-Ottawa Scale. Finally, the extracted data were pooled as risk ratios (RR) and hazard ratios (HR) in the random-effects meta-analysis model using the Review Manager software.

Results

We included nine studies with 14,221 participants and follow-up periods > 18 months. Overall, CMBs significantly increased the risk of developing dementia (RR 1.84, 95% CI [1.27-2.65]). This association was significant in the subgroups of studies on high-risk populations (RR 2.00, 95% CI [1.41-2.83], n = 1657 participants) and those in the general population (RR 2.30, 95% CI [1.25-4.26], n = 12,087 participants) but not in the memory clinic patients. Further, CMBs increased the risk of progressing to incident dementia over time (HR 2, 95% CI [1.54-2.61]).

Conclusion

Individuals with CMBs have twice the risk of developing dementia or progressing to MCI than those without CMBs. The detection of CMBs will help identify the population at higher risk of developing dementia. Physicians should educate individuals with CMBs and their families on the possibility of progressing to dementia or MCI. Regular cognitive assessments, cognitive training, lifestyle modifications, and controlling other dementia risk factors are recommended for individuals with CMBs to decrease the risk of cognitive decline and dementia development.

Vascular contributions to Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of dementia and is characterized by progressive neurodegeneration and cognitive decline. Understanding the pathophysiology underlying AD is paramount for the management of individuals at risk of and suffering from AD. The vascular hypothesis stipulates a relationship between cardiovascular disease and AD-related changes although the nature of this relationship remains unknown. In this review, we discuss several potential pathological pathways of vascular involvement in AD that have been described including dysregulation of neurovascular coupling, disruption of the blood brain barrier, and reduced clearance of metabolite waste such as beta-amyloid, a toxic peptide considered the hallmark of AD. We will also discuss the two-hit hypothesis which proposes a 2-step positive feedback loop in which microvascular insults precede the accumulation of Aß and are thought to be at the origin of the disease development. At neuroimaging, signs of vascular dysfunction such as chronic cerebral hypoperfusion have been demonstrated, appearing early in AD, even before cognitive decline and alteration of traditional biomarkers. Cerebral small vessel disease such as cerebral amyloid angiopathy, characterized by the aggregation of Aß in the vessel wall, is highly prevalent in vascular dementia and AD patients. Current data is unclear whether cardiovascular disease causes, precipitates, amplifies, precedes, or simply coincides with AD. Targeted imaging tools to quantitatively evaluate the intracranial vasculature and longitudinal studies in individuals at risk for or in the early stages of the AD continuum could be critical in disentangling this complex relationship between vascular disease and AD.

Iron Deposition in Brain: Does Aging Matter?

The alteration of iron homeostasis related to the aging process is responsible for increased iron levels, potentially leading to oxidative cellular damage. Iron is modulated in the Central Nervous System in a very sensitive manner and an abnormal accumulation of iron in the brain has been proposed as a biomarker of neurodegeneration. However, contrasting results have been presented regarding brain iron accumulation and the potential link with other factors during aging and neurodegeneration. Such uncertainties partly depend on the fact that different techniques can be used to estimate the distribution of iron in the brain, e.g., indirect (e.g., MRI) or direct (post-mortem estimation) approaches. Furthermore, recent evidence suggests that the propensity of brain cells to accumulate excessive iron as a function of aging largely depends on their anatomical location. This review aims to collect the available data on the association between iron concentration in the brain and aging, shedding light on potential mechanisms that may be helpful in the detection of physiological neurodegeneration processes and neurodegenerative diseases such as Alzheimer's disease.

Monitoring mild cognitive impairment of workers exposed to occupational aluminium based on quantitative susceptibility mapping

AIM

To investigate the diagnostic value of quantitative susceptibility mapping (QSM) in mild cognitive impairment (MCI) of aluminium (Al) workers.

MATERIALS AND METHODS

The basic data of 53 workers in an Al factory were collected and divided into the MCI group and normal control (NC) group by Montreal Cognitive Assessment (MoCA) scores. All participants were tested for plasma Al concentration and had magnetic resonance imaging (MRI). The QSM values of many areas of the brain were delineated and measured. Independent two-sample t-tests or non-parametric tests were used to compare the parameter values between the two groups. Spearman's correlation analysis was performed between QSM values, MoCA scores, and plasma Al concentration. The receiver operating characteristic curve and z test were performed to assess diagnostic efficacy and the best parameter.

RESULTS

There was no difference in age and educational level. Plasma Al concentration of the MCI group was higher than that of NC group (p=0.057). QSM values of the left hippocampus, left dentate nucleus, right substantia nigra, and left putamen in MCI group were higher than that of NC group (p<0.05), and the left hippocampus had the best diagnostic efficacy. QSM values correlated negatively with MoCA scores. No correlation was found between QSM values and plasma Al concentration (p>0.05).

CONCLUSION

QSM might be a neuroimaging marker for the diagnosis of MCI. The left hippocampus showed the best diagnostic efficacy. Plasma Al concentration of the MCI group was higher than that of the NC group. A correlation between QSM and plasma Al concentration was not found.

Systematic Review on the Role of Lobar Cerebral Microbleeds in Cognition

BACKGROUND

Cerebral microbleeds (CMBs) are small round/oval lesions seen in MRI-specific sequences. They are divided in deep and lobar according to their location. Lobar CMBs (L-CMBs) are commonly associated with amyloid angiopathy. Although CMBs have been considered clinically silent for a long time, a growing body of evidence has shown that they could play a crucial role in cognitive functioning.

OBJECTIVE

The aim of this systematic review was to estimate the role of L-CMBs in cognitive performance.

METHODS

We selected, from the Cochrane Library, Embase, PubMed, and ScienceDirect databases, clinical studies, published from January 2000 to January 2020 and focused on the association between L-CMBs and cognitive functions. The inclusion criteria were: 1) participants grouped according to presence or absence of CMBs, 2) extensive neuropsychological examination, 3) CMBs differentiation according to topographical distribution, and 4) MRI-based CMB definition (< 10 mm and low signal in T2*/SWI). The impact of L-CMBs was separately assessed for executive functions, visuospatial skills, language, and memory.

RESULTS

Among 963 potentially eligible studies, six fulfilled the inclusion criteria. Four studies reported a greater reduction in executive performances in participants with L-CMB and two studies showed a statistically significant association between visuospatial dysfunction and L-CMBs. No association was found between hippocampal memory or language abilities and L-CMBs.

CONCLUSION

Lobar CMBs are associated with a reduction of processing speed and visuospatial performances, thus suggesting the contribution of vascular amyloid deposition to this cognitive profile. This occurrence enables us to suspect an underlying Alzheimer's disease pathology even in absence of typical hippocampal memory impairment.

Disrupted White Matter Integrity and Cognitive Functions in Amyloid-β Positive Alzheimer's Disease with Concomitant Lobar Cerebral Microbleeds

BACKGROUND

Lobar cerebral microbleeds (CMBs), which can impair white matter (WM), are often concomitant with definite Alzheimer's disease (AD).

OBJECTIVE

To explore the features of cognitive impairments and WM disruptions due to lobar CMBs in patients with AD.

METHODS

There were 310 participants who underwent Florbetapir F18 (AV45) amyloid PET and susceptibility-weighted imaging. Participants with cognitive impairment and amyloid-β positive (ADCI) were included into three groups: ADCI without CMBs, with strictly lobar CMBs (SL-CMBs), and with mixed CMBs (M-CMBs). Tract-based spatial statistics were performed to detect the group differences in WM integrity.

RESULTS

There were 82 patients and 29 healthy controls finally included. A decreasing tendency in memory and executive performance can be found among HCs > no CMBs (n = 16) >SL-CMBs (n = 41) >M-CMBs (n = 25) group. Compared to no CMBs, M-CMBs group had significantly decreased fractional anisotropy in left anterior thalamic radiation (ATR), forceps major, forceps minor and inferior longitudinal fasciculus, bilateral inferior fronto-occipital fasciculus (IFOF), and superior longitudinal fasciculus. M-CMBs group also had lower fractional anisotropy in left ATR, IFOF, uncinate fasciculus, and forceps minor compared with SL-CMBs. Furthermore, analysis of Pearson correlation indicated damages in discrepant WMs were positively associated with impairment of memory, executive function, and attention.

CONCLUSION

This study showed lobar CMBs had intensively aggravated cognitive impairments associated with extensive WM damages in definite AD. These findings highlight that lobar CMBs play an important role in AD progression and need to be taken into consideration for the early detection of AD.

Emerging Applications for Quantitative Susceptibility Mapping in the Detection of Traumatic Brain Injury Pathology

Traumatic brain injury (TBI) is a common but heterogeneous injury underpinned by numerous complex and interrelated pathophysiological mechanisms. An essential trace element, iron is abundant within the brain and involved in many fundamental neurobiological processes, including oxygen transportation, oxidative phosphorylation, myelin production and maintenance, as well as neurotransmitter synthesis and metabolism. Excessive levels of iron are neurotoxic and thus iron homeostasis is tightly regulated in the brain, however, many details about the mechanisms by which this is achieved are yet to be elucidated. A key mediator of oxidative stress, mitochondrial dysfunction and neuroinflammatory response, iron dysregulation is an important contributor to secondary injury in TBI. Advances in neuroimaging that leverage magnetic susceptibility properties have enabled increasingly comprehensive investigations into the distribution and behaviour of iron in the brain amongst healthy individuals as well as disease states such as TBI. Quantitative Susceptibility Mapping (QSM) is an advanced neuroimaging technique that promises quantitative estimation of local magnetic susceptibility at the voxel level. In this review, we provide an overview of brain iron and its homeostasis, describe recent advances enabling applications of QSM within the context of TBI and summarise the current state of the literature. Although limited, the emergent research suggests that QSM is a promising neuroimaging technique that can be used to investigate a host of pathophysiological changes that are associated with TBI.

Ex vivo MRI facilitates localization of cerebral microbleeds of different ages during neuropathology assessment

Cerebral microbleeds (CMBs) identified by in vivo magnetic resonance imaging (MRI) of brains of older persons may have clinical relevance due to their association with cognitive impairment and other adverse neurologic outcomes, but are often not detected in routine neuropathology evaluations. In this study, the utility of ex vivo MRI in the neuropathological identification, localization, and frequency of CMBs was investigated. The study included 3 community dwelling elders with Alzheimer's dementia, and mild to severe small vessel disease (SVD). Ex vivo MRI was performed on the fixed hemisphere to identify CMBs, blinded to the neuropathology diagnoses. The hemibrains were then sliced at 1 cm intervals and 2, 1 or 0 microhemorrhages (MH) were detected on the cut surfaces of brain slabs using the routine neuropathology protocol. Ex vivo imaging detected 15, 14 and 9 possible CMBs in cases 1, 2 and 3, respectively. To obtain histological confirmation of the CMBs detected by ex vivo MRI, the 1 cm brain slabs were dissected further and MHs or areas corresponding to the CMBs detected by ex vivo MRI were blocked and serially sectioned at 6 µm intervals. Macroscopic examination followed by microscopy post ex vivo MRI resulted in detection of 35 MHs and therefore, about 12 times as many MHs were detected compared to routine neuropathology assessment without ex vivo MRI. While microscopy identified previously unrecognized chronic MHs, it also showed that MHs were acute or subacute and therefore may represent perimortem events. Ex vivo MRI detected CMBs not otherwise identified on routine neuropathological examination of brains of older persons and histologic evaluation of the CMBs is necessary to determine the age and clinical relevance of each hemorrhage.

Quantitative susceptibility mapping in β-Amyloid PET-stratified patients with dementia and healthy controls - A hybrid PET/MRI study

PURPOSE

Post-mortem and in-vivo MRI data suggest an accumulation of iron in the brain of Alzheimer's disease (AD) patients. The majority of studies in clinically diagnosed AD patients found an increase of iron-sensitive MRI signals in the putamen. As the clinical diagnosis shows only a moderate sensitivity, Aβ-PET was used to further stratify patients with the clinical diagnosis of AD. Aim of this exploratory study was to examine whether Aβ-positive (AD) and Aβ-negative (non-AD) patients differ in their regional magnetic susceptibility compared to healthy controls (HCs) and whether regional susceptibility values correlate with mini mental state examination (MMSE) scores or global Aβ-load.

METHODS

We retrospectively analyzed [¹¹C]PiB PET/MRI data of 11 HCs, 16 AD and 10 non-AD patients. We used quantitative susceptibility mapping (QSM) as iron-sensitive MRI signal measured at the 3 T PET/MR scanner. Global cerebral Aβ-load was determined by composite [¹¹C]PiB SUV ratios.

RESULTS

Compared to HCs, AD patients showed higher QSM values in putamen (0.049 ± 0.033 vs. 0.002 ± 0.031; p = 0.006), while non-AD patients showed lower QSM values in caudate nucleus (0.003 ± 0.027 vs. 0.051 ± 0.039; p = 0.006). There was a trend towards a significant correlation between putaminal QSM and MMSE values (ρ=-0.340, p = 0.053). In AD patients, global Aβ-load and putaminal QSM values were significantly correlated (ρ=-0.574, p = 0.020).

CONCLUSIONS

These data indicate that AD and non-AD patients may show different cerebral iron pathologies which might be detectable by QSM MRI, and might be linked to neurodegeneration. Overall, the data encourage further investigations in well-defined patient cohorts to clarify the value of QSM/magnetic susceptibility in the course of neurodegenerative diseases and its potential as diagnostic biomarker.

Microhemorrhage in a Rat Model of Neonatal Shaking Brain Injury: Correlation between MRI and Iron Histochemistry

Previous studies have shown that neonatal shaking brain injury (SBI) causes transient microhemorrhages (MHs) in the gray matter of the cerebral cortex and hippocampus. Iron deposits and iron-uptake cells are observed surrounding MHs in this SBI model, suggesting local hypoxic-ischemic conditions. However, whether the shaken pups suffered systemic hypoxic-ischemic conditions has remained uncertain. Further, histopathological correlations of MHs on magnetic resonance imaging (MRI) are still unclear. The present study examined MHs after neonatal SBI using a combination of histochemical and susceptibility-weighted imaging (SWI) analyses. Systemic oxygen saturation analyses indicated no significant difference between shaken and non-shaken pups. MHs on postnatal day 4 (P4) pups showed decreased signal intensity on SWI. Iron histochemistry revealed that these hypointense areas almost completely comprised red blood cells (RBCs). MHs that appeared on P4 gradually disappeared by P7-12 on SWI. These resolved areas contained small numbers of RBCs, numerous iron-positive cells, and punctate regions with iron reaction products. Perivascular iron products were evident after P12. These changes progressed faster in the hippocampus than in cortical areas. These changes in MHs following neonatal SBI may provide new insights into microvascular pathologies and impacts on brain functions as adults.

Deep Gray Matter Iron Deposition and Its Relationship to Clinical Features in Cerebral Autosomal Dominant Arteriopathy With Subcortical Infarcts and Leukoencephalopathy Patients

Background and Purpose—

Distribution patterns of iron deposition in deep gray matter and their association with clinical characteristics in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) remain unclear. We aimed to evaluate iron deposition in deep gray matter in patients with CADASIL using 7.0-T susceptibility-weighted imaging and mapping and to explore its correlations with clinical characteristics.

Methods—

Thirty-nine patients with CADASIL, confirmed via genetic analysis or skin biopsy, were enrolled. We examined patients using the Mini-Mental State Examination, modified Rankin Scale, and brain 7.0-T magnetic resonance imaging and obtained magnetic resonance imaging lesion loads, small vessel disease scores, and susceptibility mapping. The following regions of interest were selected: caudate nucleus, putamen, globus pallidus, thalamus, substantia nigra, and red nucleus. The quantitative differences in the susceptibility of deep gray matter between the CADASIL and control groups and the correlations between deep gray matter susceptibility and clinical characteristics were identified.

Results—

Compared with the control group, the CADASIL group showed significantly increased susceptibility of caudate nucleus, putamen, thalamus, substantia nigra, and red nucleus. The susceptibility of deep gray matter in basal ganglia region, including caudate nucleus, putamen, and thalamus, significantly increased with age or disease duration and positively correlated with small vessel disease scores in patients with CADASIL. Moreover, the susceptibility of thalamus positively correlated with modified Rankin Scale scores after adjusting for age and disease duration and that of putamen negatively correlated with Mini-Mental State Examination scores in patients with CADASIL after adjusting for age.

Conclusions—

Our findings indicate an association between abnormal iron deposition in deep gray matter of patients with CADASIL and their clinical characteristics. Therefore, excess iron deposition in deep gray matter, as indicated by 7.0-T susceptibility-weighted imaging and mapping, might not only be a novel magnetic resonance imaging feature but also a potential biomarker for CADASIL severity.

Atypical Clinical Manifestations of Cerebral Amyloid Angiopathy

PURPOSE

Cerebral amyloid angiopathy is a vasculopathy caused by β-amyloid deposition in cerebral arterioles and capillaries. It is closely linked to Alzheimer's disease and predisposes elderly patients to intracerebral hemorrhage, transient focal neurological episodes, and cognitive impairment. Because of a predilection for symptomatic hemorrhage, particularly in the frontal lobes, cerebral amyloid angiopathy may also cause a dysexecutive syndrome.

RECENT FINDINGS

In this case series, we describe presentations of classic clinical dementia syndromes which are not are widely thought to be associated with cerebral amyloid angiopathy, namely logopenic variant primary progressive aphasia (n = 3), normal pressure hydrocephalus (n = 3), and Lewy body dementia (n = 2). In every case, after a clinical diagnosis was established, neuroimaging, brain biopsy, and/or autopsy confirmed the presence of cerebral amyloid angiopathy. Cerebral amyloid angiopathy has significant clinical implications, and its ability to mimic and/or contribute to other clinical dementia syndromes can complicate its diagnosis. This series of cases broadens the range of clinical scenarios associated with cerebral amyloid angiopathy.

Quantitative Susceptibility Mapping of Amyloid-β Aggregates in Alzheimer's Disease with 7T MR

BACKGROUND

PET imaging is an established technique to detect cerebral amyloid-β (Aβ) plaques in vivo. Some preclinical and postmortem data report an accumulation of redox-active iron near Aβ plaques. Quantitative susceptibility mapping (QSM) at high-field MRI enables iron deposits to be depicted with high spatial resolution.

OBJECTIVE

Aim of this study was to examine whether iron and Aβ plaque accumulation is related and thus, whether 7T MRI might be an additive diagnostic tool to Aβ PET imaging.

METHODS

Postmortem human Alzheimer's disease (AD) and healthy control (HC) frontal gray matter (GM) was imaged with 7T MRI which resulted in T1 maps and QSM. Aβ plaque load was determined by histopathology. In vivo, 10 Aβ PET-positive AD patients (74.1±6.0a) and 10 Aβ PET-negative HCs (67.1±4.4a) underwent 7T MR examination and QSM maps were analyzed. Severity of cognitive deficits was determined by MMSE.

RESULTS

Postmortem, the susceptibility of Aβ plaque-containing GM were higher than those of Aβ plaque-free GM (0.011±0.002 versus - 0.008±0.003 ppm, p < 0.001). In vivo, only the bilateral globus pallidus showed significantly higher susceptibility in AD patients compared to HCs (right: 0.277±0.018 versus - 0.009±0.009 ppm; left: 0.293±0.014 versus - 0.007±0.012 ppm, p < 0.0001). The pallidal QSM values were negatively correlated with those of the MMSE (r = - 0.69, p = 0.001).

CONCLUSION

The postmortem study revealed significant susceptibility differences between the Aβ plaque-containing and Aβ plaque-free GM, whereas in vivo only the QSM values of the globus pallidus differed significantly between AD and HC group. The pallidal QSM values correlated with the severity of cognitive deficits. These findings encourage efforts to optimize the 7T-QSM methodology.

Increased Plasma VEGF Levels in Patients with Cerebral Large Artery Disease Are Associated with Cerebral Microbleeds

Background/Purpose

Because atherosclerotic factors and antithrombotic agents sometimes induce cerebral microbleeds (CMBs), patients with cerebral large artery disease (CLAD) tend to have more CMBs than control subjects. On the other hand, VEGF contributes to the disruption of the blood-brain barrier, and it may induce parenchymal edema and bleeding. We conducted a study to evaluate the role of vascular endothelial growth factor (VEGF) in the occurrence of CMBs in patients with CLAD.

Methods

CLAD is defined as stenosis or occlusion of either the carotid artery or the middle cerebral artery of 50% or more. We prospectively registered patients with CLAD who were hospitalized in our neurocenter. Biological backgrounds, atherosclerotic risk factors, administration of antithrombotics before hospitalization, and levels of cytokines and chemokines were evaluated. Susceptibility-weighted imaging or T2*-weighted MR angiography was used to evaluate CMBs. The Brain Observer MicroBleed Scale (BOMBS) was used for CMB assessments. Images were analyzed with regard to the presence or absence of CMBs. We also examined plasma VEGF concentrations using a commercial ELISA kit. Because more than half showed plasma VEGF levels below assay detection limits (3.2 pg/mL), the patients were dichotomized by plasma VEGF levels into two groups (above and below the detection limit). After univariate analyses, logistic regression analysis was conducted to determine the factors associated with the CMBs after adjustment for age, sex, the presence of hypertension, and administration of antithrombotic agents. A similar analysis with CMBs separated by location (cortex, subcortex, or posterior circulation) was also conducted.

Results

Sixty-six patients (71.1 ± 8.9 years, 53 males and 13 females) were included in this study. Plasma VEGF levels were not correlated with age, sex, and atherosclerotic risk factors; however, patients with VEGF levels >3.2 pg/mL tended toward more frequent CMBs (60.0 vs. 32.6%, in the presence and absence of CMBs, p = 0.056). With regard to the location of CMBs, those in the cortex and/or at the gray-white junction were observed more frequently in the patients with VEGF levels >3.2 pg/mL after multivariable analyses (odds ratio: 3.80; 95% confidence interval: 1.07–13.5; p = 0.039).

Conclusions

In patients with CLAD, elevated plasma VEGF might be associated with CMBs, especially those located in the cortex and/or at the gray-white junction.

Multivariate MR biomarkers better predict cognitive dysfunction in mouse models of Alzheimer's disease

To understand multifactorial conditions such as Alzheimer's disease (AD) we need brain signatures that predict the impact of multiple pathologies and their interactions. To help uncover the relationships between pathology affected brain circuits and cognitive markers we have used mouse models that represent, at least in part, the complex interactions altered in AD, while being raised in uniform environments and with known genotype alterations. In particular, we aimed to understand the relationship between vulnerable brain circuits and memory deficits measured in the Morris water maze, and we tested several predictive modeling approaches. We used in vivo manganese enhanced MRI traditional voxel based analyses to reveal regional differences in volume (morphometry), signal intensity (activity), and magnetic susceptibility (iron deposition, demyelination). These regions included hippocampus, olfactory areas, entorhinal cortex and cerebellum, as well as the frontal association area. The properties of these regions, extracted from each of the imaging markers, were used to predict spatial memory. We next used eigenanatomy, which reduces dimensionality to produce sets of regions that explain the variance in the data. For each imaging marker, eigenanatomy revealed networks underpinning a range of cognitive functions including memory, motor function, and associative learning, allowing the detection of associations between context, location, and responses. Finally, the integration of multivariate markers in a supervised sparse canonical correlation approach outperformed single predictor models and had significant correlates to spatial memory. Among a priori selected regions, expected to play a role in memory dysfunction, the fornix also provided good predictors, raising the possibility of investigating how disease propagation within brain networks leads to cognitive deterioration. Our cross-sectional results support that modeling approaches integrating multivariate imaging markers provide sensitive predictors of AD-like behaviors. Such strategies for mapping brain circuits responsible for behaviors may help in the future predict disease progression, or response to interventions.

Cerebral Microbleeds: Imaging and Clinical Significance

Cerebral microbleeds (CMBs), also referred to as microhemorrhages, appear on magnetic resonance (MR) images as hypointense foci notably at T2*-weighted or susceptibility-weighted (SW) imaging. CMBs are detected with increasing frequency because of the more widespread use of high magnetic field strength and of newer dedicated MR imaging techniques such as three-dimensional gradient-echo T2*-weighted and SW imaging. The imaging appearance of CMBs is mainly because of changes in local magnetic susceptibility and reflects the pathologic iron accumulation, most often in perivascular macrophages, because of vasculopathy. CMBs are depicted with a true-positive rate of 48%-89% at 1.5 T or 3.0 T and T2*-weighted or SW imaging across a wide range of diseases. False-positive "mimics" of CMBs occur at a rate of 11%-24% and include microdissections, microaneurysms, and microcalcifications; the latter can be differentiated by using phase images. Compared with postmortem histopathologic analysis, at least half of CMBs are missed with premortem clinical MR imaging. In general, CMB detection rate increases with field strength, with the use of three-dimensional sequences, and with postprocessing methods that use local perturbations of the MR phase to enhance T2* contrast. Because of the more widespread availability of high-field-strength MR imaging systems and growing use of SW imaging, CMBs are increasingly recognized in normal aging, and are even more common in various disorders such as Alzheimer dementia, cerebral amyloid angiopathy, stroke, and trauma. Rare causes include endocarditis, cerebral autosomal dominant arteriopathy with subcortical infarcts, leukoencephalopathy, and radiation therapy. The presence of CMBs in patients with stroke is increasingly recognized as a marker of worse outcome. Finally, guidelines for adjustment of anticoagulant therapy in patients with CMBs are under development. ^© RSNA, 2018.

Incident Cerebral Microbleeds Detected by Susceptibility Weight-Imaging Help to Identify Patients with Mild Cognitive Impairment Progressing to Alzheimer's Disease

BACKGROUND

The relationship between cerebral microbleeds (CMB) and Alzheimer's disease (AD) has not yet been clearly determined, particularly with susceptibility weight-imaging (SWI).

OBJECTIVE

To evaluate the SWI sequence using 3T MRI for the detection of CMB, and its ability to differentiate elderly control subjects (CS), stable mild cognitive impairment patients (MCI-s), MCI patients progressing to AD (MCI-p), and AD patients.

METHODS

It was a prospective, monocentric, observational study that took place in Toulouse, France. Participants were 65 years and older, enrolled in three groups: CS, MCI, and AD. Based on the longitudinal analysis of cognitive decline, MCI subjects were retrospectively classified as MCI-s or MCI-p. Each patient had a 4-year follow-up with MRI at baseline (MRI#1) and during the fourth year (MRI#3). CMB were counted on native SWI images juxtaposed to minIP reformatted images.

RESULTS

150 patients were enrolled: 48 CS, 25 MCI-s, 18 MCI-p, 59 AD. At MRI#1 and at MRI#3, there was no significant difference in the prevalence of CMB between groups (p = 0.75 and p = 0.87). In the MCI-p + AD group, significantly more subjects had≥4 incident CMB compared to the CS + MCI-s group (p = 0.016). In the MCI-p + AD group, the prevalence of patients with >4 CMB was significantly higher at MRI#3 than at MRI#1 (p = 0.008).

CONCLUSION

Using SWI, AD and MCI-p patients had developed significantly more new CMB than CS and MCI-s patients during the follow-up. Incident CMB might be suggested as a potential imaging marker of AD progression.

Fibrinogen in neurological diseases: mechanisms, imaging and therapeutics

The blood coagulation protein fibrinogen is deposited in the brain in a wide range of neurological diseases and traumatic injuries with blood-brain barrier (BBB) disruption. Recent research has uncovered pleiotropic roles for fibrinogen in the activation of CNS inflammation, induction of scar formation in the brain, promotion of cognitive decline and inhibition of repair. Such diverse roles are possible in part because of the unique structure of fibrinogen, which contains multiple binding sites for cellular receptors and proteins expressed in the nervous system. The cellular and molecular mechanisms underlying the actions of fibrinogen are beginning to be elucidated, providing insight into its involvement in neurological diseases, such as multiple sclerosis, Alzheimer disease and traumatic CNS injury. Selective drug targeting to suppress the damaging functions of fibrinogen in the nervous system without affecting its beneficial effects in haemostasis opens a new fibrinogen therapeutics pipeline for neurological disease.

Considerations on accuracy, pattern and possible underlying factors of brain microbleed progression in older adults with absence or mild presence of vascular pathology

Objective To analyse brain microbleed (BMB) progression, its possible underlying factors, and the influence of inter-observer differences, in older individuals with none or mild vascular pathology. Methods This study analysed magnetic resonance images, cognitive, demographic and laboratory data from all individuals from the Alzheimer's Disease (AD) Neuroimaging Initiative database who had the required sequences for identifying BMBs over three consecutive years at the time the database was accessed (January 2016). BMBs were assessed independently by two observers with similar levels of experience. Results A total of 291 patients were included in the study. The number of individuals with BMBs and the number of BMBs per individual slightly and nonsignificantly increased across three consecutive years (Y1: 55/291 [19%]; Y2: 61/291 [21%]; Y3: 66/291 [23%]) with 1-2 BMBs and (Y1: 11/291 [4%]; Y2: 12/291 [4%]; Y3: 14/291 [5%]) with ≥ 3 BMBs. Both observers identified a similar pattern of BMB prevalence and progression in each cognitive group (normal < early/late mild cognitive impairment (MCI) > AD patients) despite inter-observer differences (1.5 BMBs, 95% confidence interval -3.7, 6.2], κ=0.543), which were mainly in the cortex. Serum cholesterol was the main predictor of change in BMB count between time-points but did not predict overall progression. Conclusions Inter-observer differences are always present and it is difficult to ascertain their influence in the analysis of BMB progression, which was observed in cognitively normal and MCI individuals, but not in AD patients. This should be confirmed in further studies.

The Relevance of Iron in the Pathogenesis of Multiple System Atrophy: A Viewpoint

Iron is essential for cellular development and maintenance of multiple physiological processes in the central nervous system. The disturbance of its homeostasis leads to abnormal iron deposition in the brain and causes neurotoxicity via generation of free radicals and oxidative stress. Iron toxicity has been established in the pathogenesis of Parkinson's disease; however, its contribution to multiple system atrophy (MSA) remains elusive. MSA is characterized by cytoplasmic inclusions of misfolded α-synuclein (α-SYN) in oligodendrocytes referred to as glial cytoplasmic inclusions (GCIs). Remarkably, the oligodendrocytes possess high amounts of iron, which together with GCI pathology make a contribution toward MSA pathogenesis likely. Consistent with this observation, the GCI density is associated with neurodegeneration in central autonomic networks as well as olivopontocerebellar and striatonigral pathways. Iron converts native α-SYN into a β-sheet conformation and promotes its aggregation either directly or via increasing levels of oxidative stress. Interestingly, α-SYN possesses ferrireductase activity and α-SYN expression underlies iron mediated translational control via RNA stem loop structures. Despite a correlation between progressive putaminal atrophy and iron accumulation as well as clinical decline, it remains unclear whether pathologic iron accumulation in MSA is a secondary event in the cascade of neuronal degeneration rather than a primary cause. This review summarizes the current knowledge of iron in MSA and gives evidence for perturbed iron homeostasis as a potential pathogenic factor in MSA-associated neurodegeneration.

Mixed dementia: A review of the evidence

Mixed dementia is the coexistence of Alzheimer's disease and cerebrovascular disease (CVD) in the same demented patient. Currently, its diagnosis and treatment remains a challenge for practitioners. To provide an overview of the epidemiology, pathogenesis, natural history, diagnosis, and therapy of Mixed Vascular-Alzheimer Dementia (MVAD). The literature was reviewed for articles published between 1990-2016 by using the keywords linked to MVAD. Neuropathological studies indicate that MVAD is a very common pathological finding in the elderly with a prevalence about of 22%. The distinction between Alzheimer's dementia and vascular dementia (VD) is complex because their clinical presentation can overlap. There are international criteria for the MVAD diagnosis. The pharmacologic therapy shows modest clinical benefits that are similar among all drugs used in patients with Alzheimer's dementia and VD. The non-pharmacologic therapy includes the rigorous management of cardiovascular risk factors (especially hypertension) and the promotion of a healthy diet. The diagnosis and treatment of MVAD cannot be improved without further studies. Currently available medications provide only modest clinical benefits once a patient has developed MVAD. In subjects at risk, the antihypertensive therapy and healthy diet should be recommend for preventing or slowing the progression of MVAD.

Incident risk and progression of cerebral microbleeds in healthy adults: a multi-occasion longitudinal study

Decline in cerebrovascular health complicates brain aging, and development of cerebral microbleeds (CMBs) is one of its prominent indicators. In a large sample of healthy adults (N = 251, age 18-78 years at baseline, 70% women), the contributions of chronological age and vascular health indicators to the risk of developing a CMB, as well as the change in CMB size and iron content, were examined in a prospective 8-year longitudinal study using susceptibility weighted imaging. Twenty-six persons (10.4%), most of whom were 40 years of age or older, had at least 1 CMB during the study. Older age was associated with greater risk for developing a CMB (odds ratio 1.03). Elevation of combined metabolic syndrome indicators (b = 0.15, p = 0.001) conferred additional risk (odds ratio 1.02). High body mass index exacerbated the risk associated with poor vascular health (b = 0.75, p < 0.001) and frequent exercise mitigated it (b = -0.46, p = 0.03). CMBs persisted over time, yet their volume decreased (mean change = -0.32, p < 0.05), whereas their relative iron content remained stable (mean change = -0.14, p = 0.05). We conclude that although developing a CMB is unlikely during normal aging, risk increases with declining vascular health, which is modifiable via behavioral and pharmaceutical intervention.

Increased CSF levels of total Tau in patients with subcortical cerebrovascular pathology and cognitive impairment

Cognitive impairment includes mild cognitive decline and dementia, such as Alzheimer's disease (AD) and cerebrovascular-related pathologies.

OBJECTIVE

To investigate the profile of AD-related CSF biomarkers in a sample of cognitively impaired and unimpaired older adults with concomitant subcortical cerebrovascular burden.

METHODS

Seventy-eight older adults attending an outpatient psychogeriatric clinic were enrolled. Diagnoses were based on clinical, neuropsychological, laboratory, and neuroimaging data. Participants were classified into: cognitively normal (controls, n = 30), mild cognitive impairment (MCI, n = 34), and dementia (AD, n = 14). All subjects were submitted to CSF analyses for determination of amyloid-beta (Aβ1-42), total tau (t-tau), phosphorylated tau (p-tau) and Aβ1-42/p-tau ratio according to the Luminex method. MRI was performed in all individuals, and was scored independently by two experts according to Fazekas scale. Statistical analyses were conducted with the aid of general linear model procedures, and the Chi-squared test.

RESULTS

T-tau levels were significantly associated with subcortical lesion pattern when Fazekas was considered as a group factor. CSF biomarkers were not associated with MCI, AD, or controls when considered separately. There was a tendency for reduction in CSF Aβ1-42 together with increasing Fazekas scores, but without statistical significance. Comparisons of Aβ1-42 and t-tau with each clinical group or with each neuroimaging pattern did not reach statistical differences. Likewise, Fazekas scores had no impact on CAMCOG scores.

CONCLUSION

We found a significant association between t-tau levels and subcortical lesions when all Fazekas classifications were considered as a single group; comparisons of Fazekas subgroups and CSF biomarkers did not reach significance.

Disease progression and regression in sporadic small vessel disease-insights from neuroimaging

Cerebral small vessel disease (SVD) is considered the most important vascular contributor to the development of dementia. Comprehensive characterization of the time course of disease progression will result in better understanding of aetiology and clinical consequences of SVD. SVD progression has been studied extensively over the years, usually describing change in SVD markers over time using neuroimaging at two time points. As a consequence, SVD is usually seen as a rather linear, continuously progressive process. This assumption of continuous progression of SVD markers was recently challenged by several studies that showed regression of SVD markers. Here, we provide a review on disease progression in sporadic SVD, thereby taking into account both progression and regression of SVD markers with emphasis on white matter hyperintensities (WMH), lacunes and microbleeds. We will elaborate on temporal dynamics of SVD progression and discuss the view of SVD progression as a dynamic process, rather than the traditional view of SVD as a continuous progressive process, that might better fit evidence from longitudinal neuroimaging studies. We will discuss possible mechanisms and clinical implications of a dynamic time course of SVD, with both progression and regression of SVD markers.

Neuropsychological Effects of Cerebral Amyloid Angiopathy

Cerebral amyloid angiopathy is a condition of the cerebral arterioles and to a lesser extent capillaries and veins, wherein beta-amyloid is deposited. In arterioles, this preferentially targets vascular smooth muscle cells and in the later stages undermines the stability of the vessel. This condition is frequently comorbid with Alzheimer's disease and its role in cognitive impairment and dementia is a topic of considerable recent research. This article reviews recent literature which confirms that CAA independently contributes to cognitive impairment by potentiating the neurodegeneration of Alzheimer's disease, by predisposing to microhemorrhagic and microischemic injury to the brain parenchyma, and by interfering with the autoregulation of CNS blood flow. In this review, we discuss the clinical presentation of cerebral amyloid angiopathy, with a focus on the neuropsychological manifestations of this vasculopathy.

Cerebral amyloid angiopathy in Down syndrome and sporadic and autosomal-dominant Alzheimer's disease

INTRODUCTION

We aimed to investigate if cerebral amyloid angiopathy (CAA) is more frequent in genetically determined than in sporadic early-onset forms of Alzheimer's disease (AD) (early-onset AD [EOAD]).

METHODS

Neuroimaging features of CAA, apolipoprotein (APOE), and cerebrospinal fluid amyloid β (Aβ) 40 levels were studied in subjects with Down syndrome (DS, n = 117), autosomal-dominant AD (ADAD, n = 29), sporadic EOAD (n = 42), and healthy controls (n = 68).

RESULTS

CAA was present in 31%, 38%, and 12% of cognitively impaired DS, symptomatic ADAD, and sporadic EOAD subjects and in 13% and 4% of cognitively unimpaired DS individuals and healthy controls, respectively. APOE ε4 genotype was borderline significantly associated with CAA in sporadic EOAD (P = .06) but not with DS or ADAD. There were no differences in Aβ040 levels between groups or between subjects with and without CAA.

DISCUSSION

CAA is more frequently found in genetically determined AD than in sporadic EOAD. Cerebrospinal fluid Aβ40 levels are not a useful biomarker for CAA in AD.

Clinicoradiologic Correlations of Cerebral Microbleeds in Advanced Age

BACKGROUND AND PURPOSE

The presence of cerebral microbleeds has been associated with dementia and cognitive decline, although studies report conflicting results. Our aim was to determine the potential role of the presence and location of cerebral microbleeds in early stages of cognitive decline.

MATERIALS AND METHODS

Baseline 3T MR imaging examinations including SWI sequences of 328 cognitively intact community-dwelling controls and 72 subjects with mild cognitive impairment were analyzed with respect to the presence and distribution of cerebral microbleeds. A neuropsychological follow-up of controls was performed at 18 months post inclusion and identified cases with subtle cognitive deficits were referred to as controls with a deteriorating condition. Group differences in radiologic parameters were studied by using nonparametric tests, 1-way analysis of variance, and Spearman correlation coefficients.

RESULTS

Cerebral microbleed prevalence was similar in subjects with mild cognitive impairment and controls with stable and cognitively deteriorating conditions (25%-31.9%). In all diagnostic groups, lobar cerebral microbleeds were more common. They occurred in 20.1% of all cases compared with 6.5% of cases with deep cerebral microbleeds. None of the investigated variables (age, sex, microbleed number, location and depth, baseline Mini-Mental State Examination score, and the Fazekas score) were significantly associated with cognitive deterioration with the exception of education of >12 years showing a slight but significant protective effect (OR, 0.44; 95% CI, 0.22-0.92; P = .028). The Mini-Mental State Examination and the Buschke total score were correlated with neither the total number nor lobar-versus-deep location of cerebral microbleeds.

CONCLUSIONS

Cerebral microbleed presence, location, and severity are not related to the early stages of cognitive decline in advanced age.

Radiologic-Histopathologic Correlation of Cerebral Microbleeds Using Pre-Mortem and Post-Mortem MRI

Introduction

Cerebral microbleeds (CMB), also known as cerebral microhemorrhages, are small areas of susceptibility on brain magnetic resonance imaging (MRI), that are increasingly detected due to the higher availability of high-field MRI systems and dedicated pulse sequences. The prevalence of CMBs increases in cases with cognitive decline. The current investigation assessed the poorly investigated radiologic–histopathologic correlation of CMBs on MRI.

Methods

The local ethical committee approved the current investigation. We retrospectively assessed a consecutive series of 1303 autopsy cases hospitalized in Geneva University Hospitals between 2000–2014. Of 112 cases with pre-mortem T2* sequences, we included 25 cases (mean age 77.3 ± 9.6, 9 females) with at least one CMB. We compared pre-mortem CMBs with targeted histopathology and post-mortem MRI.

Results

25 cases had 31 CMB lesions detected by pre-mortem MRI. 25 additional CMB were detected on histopathology. 4 CMBs on pre-mortem MRI were false positives, resulting in a total of 52 CMBs. 27 CMBs on pre-mortem MRI were confirmed on histopathology, corresponding to a sensitivity or true positive rate of 51.9% (95% CI 37.6–66.0%). The false negative rate of pre-mortem MRI was 48.1% (95% CI 34.0–62.4%). Post-mortem MRI showed only 3 cases with additional CMBs. Overall, pre-mortem MRI significantly underestimated CMBs (p = 0.0001).

Conclusions

Routine clinical brain MRI underestimates the prevalence of CMBs by approximately 50%, and 12% of radiologic pre-mortem MRI CMBs were false positives. Post-mortem MRI confirmed that this discordance is not explained by microbleeds occurring after the pre-mortem MRI.

Interrelationships Among Neuroimaging Biomarkers, Neuropsychological Test Data, and Symptom Reporting in a Cohort of Retired National Football League Players

Background:

Structural brain changes, potentially resulting from repetitive brain trauma (RBT), have been correlated with neurocognitive decline and increased symptom reporting in retired athletes.

Hypothesis:

In a cohort of retired National Football League (NFL) players, the relationships between 3 neuroimaging parameters, neuropsychological testing, and symptom scores will be significantly correlated.

Study Design:

Cross-sectional study.

Level of Evidence:

Level 3.

Methods:

Comprehensive magnetic resonance imaging was performed in 45 retired NFL players. Three neuroanatomical parameters were assessed by board-certified radiologists blinded to the purpose of the study: (1) the absence or presence of small or large cavum septum pellucidum, (2) a global mean score of fractional anisotropy (FA), and (3) the presence or absence of microhemorrhages. The subjects underwent a battery of 9 paper-and-pencil neuropsychological tests, a computerized neurocognitive test, and multiple symptom and depression scales. The associations among the neuroimaging results with these outcome measures were assessed utilizing Pearson, Spearman rank, and point-biserial correlations.

Results:

The 45 subjects (mean age, 46.7 ± 9.1 years) reported a mean 6.9 (±6.2) concussions and 13.0 (±7.9) “dings” in the NFL. Ten (22%) did not have a cavum septum pellucidum, while 32 (71%) had a small and 3 (7%) had a large one. Four (9%) had microhemorrhages. Global FA mean was 0.459 (±0.035). The majority (50.8%) of correlations among the neuroimaging parameters and neurocognitive/symptom scores fell below the threshold of “small” effect size (r < 0.10). The remaining (49.2%) correlations were between “small” and “medium” effect sizes (0.1 < r < 0.3). However, all correlations were statistically nonsignificant.

Conclusion:

There were minimal and statistically nonsignificant correlations among the neuroimaging, neurocognitive, and symptom scores examined in this cohort of NFL retirees.

Clinical Relevance:

Associating the severity of structural brain changes to neurocognitive performance and symptom burden after RBT is complex may involve other moderating variables or biomarkers, and demands further study.

Colocalization of cerebral iron with Amyloid beta in Mild Cognitive Impairment

Quantitative Susceptibility Mapping (QSM) MRI at 7 Tesla and 11-Carbon Pittsburgh-Compound-B PET were used for investigating the relationship between brain iron and Amyloid beta (Aβ) plaque-load in a context of increased risk for Alzheimer's disease (AD), as reflected by the Apolipoprotein E ε4 (APOE-e4) allele and mild cognitive impairment (MCI) in elderly subjects. Carriers of APOE-e4 with normal cognition had higher cortical Aβ-plaque-load than non-carriers. In MCI an association between APOE-e4 and higher Aβ-plaque-load was observable both for cortical and subcortical brain-regions. APOE-e4 and MCI was also associated with higher cortical iron. Moreover, cerebral iron significantly affected functional coupling, and was furthermore associated with increased Aβ-plaque-load (R²-adjusted = 0.80, p < 0.001) and APOE-e4 carrier status (p < 0.001) in MCI. This study confirms earlier reports on an association between increased brain iron-burden and risk for neurocognitive dysfunction due to AD, and indicates that disease-progression is conferred by spatial colocalization of brain iron deposits with Aβ-plaques.

Microbleeds in Alzheimer's Disease: A Neuropsychological Overview and Meta-Analysis

The current literature on the role of brain microbleeds (MB) on the neuropsychological outcomes of Alzheimer's disease (AD) is heterogeneous. We therefore meta-analytically examined the neuropsychological literature pertaining to MBs in AD. Using a priori selected criteria, studies with cross-sectional neuropsychological assessment on MBs and AD were reviewed. Six of 122 studies met selection criteria and provided neuropsychological data on either AD with MB and without MB, or in contrast to healthy controls. The global neuropsychological difference between AD with MB and AD without MB based on random effect model was nonsignificant, heterogeneous, and small (Effect Size =-0.155; 95% confidence interval =-0.465 to 0.155; p value =0.326; Heterogenity: Q-value =12.744; degrees of freedom =5; p =0.026; I2 =61%). The contribution of MBs to cognitive deficits in AD remains unclear. Future studies of MB in AD should strive to use standardized neuroimaging techniques with high sensitivity for MB, a common standard for MB definition, and neuropsychological tests sensitive for detecting subtle cognitive impairment.

Effect of normal aging on the structure of marginal division of neostriatum as measured by MR phase imaging and diffusion tensor imaging

PURPOSE

To investigate the structural changes of marginal division (MrD) which is the high intensity zone between globus pallidus and putamen on phase image in the human brain.

MATERIALS AND METHODS

The structural changes of MrD were investigated based on MR phase imaging and diffusion tensor imaging (DTI) data at 3.0 Tesla (T) MR scanner in 72 volunteers. Phase value, including high iron components (HIC), low iron components (LIC), LIC ratio, and average iron components (AIC), were obtained using histogram analysis about the head of caudate nucleus (CA), globus pallidus (GP), putamen (PU), and MrD. The structural measurement of MrD was applied on corrected phase images (CPIs). Average apparent diffusion coefficient (ADC) values and fractional anisotropy (FA) values were calculated based on DTI data.

RESULTS

MrD showed negative correlation for LIC with aging, with the highest HIC (left/right 2149.3 ± 19.6/2155.9 ± 17.9) and LIC (left/right 1996.6 ± 18.2/1999.6 ± 20.7), the lowest LIC ratio (left/right 21.5% ± 7.9%/19.4% ± 8.0%), and the highest AIC (left/right 2116.4 ± 21.4/2124.7 ± 21.0). The width (Head: left/right 2.01 ± 0.41 mm/1.86 ± 0.36 mm; Body: left/right 1.84 ± 0.38 mm/1.49 ± 0.29 mm; Tail: left/right 1.17 ± 0.36 mm/1.05 ± 0.23 mm) and area (left/right 49.44 ± 9.71 mm² /42.75 ± 8.80 mm² ) of MrD showed negative correlation with aging, presenting gradually narrower pattern based on CPIs. Average ADC value (left/right 0.69 ± 0.04 10^-3 mm² /s / 0.71 ± 0.03 10^-3 mm² /s) revealed negative correlation, while FA value (left/right 0.19 ± 0.03/0.22 ± 0.03) revealed positive correlation with aging.

CONCLUSION

The findings suggested that the structure measurements based on CPIs and DTI could provide a simple and effective tool for the evaluation of MrD in vivo in the human brain and for the assessment of the changes seen with aging.

LEVEL OF EVIDENCE

1 J. MAGN. RESON. IMAGING 2017;45:1343-1351.

Presence of cerebral microbleeds is associated with worse executive function in pediatric brain tumor survivors

BACKGROUND

A specific form of small-vessel vasculopathy-cerebral microbleeds (CMBs)-has been linked to various types of dementia in adults. We assessed the incidence of CMBs and their association with neurocognitive function in pediatric brain tumor survivors.

METHODS

In a multi-institutional cohort of 149 pediatric brain tumor patients who received cranial radiation therapy (CRT) between 1987 and 2014 at age <21 years and 16 patients who did not receive CRT, we determined the presence of CMBs on brain MRIs. Neurocognitive function was assessed using a computerized testing program (CogState). We used survival analysis to determine cumulative incidence of CMBs and Poisson regression to examine risk factors for CMBs. Linear regression models were used to assess effect of CMBs on neurocognitive function.

RESULTS

The cumulative incidence of CMBs was 48.8% (95% CI: 38.3-60.5) at 5 years. Children who had whole brain irradiation developed CMBs at a rate 4 times greater than those treated with focal irradiation (P < .001). In multivariable analysis, children with CMBs performed worse on the Groton Maze Learning test (GML) compared with those without CMBs (Z-score -1.9; 95% CI: -2.7, -1.1; P < .001), indicating worse executive function when CMBs are present. CMBs in the frontal lobe were associated with worse performance on the GML (Z-score -2.4; 95% CI: -2.9, -1.8; P < .001). Presence of CMBs in the temporal lobes affected verbal memory (Z-score -2.0; 95% CI: -3.3, -0.7; P = .005).

CONCLUSION

CMBs are common and associated with neurocognitive dysfunction in pediatric brain tumor survivors treated with radiation.

Evaluating the Role of Reduced Oxygen Saturation and Vascular Damage in Traumatic Brain Injury Using Magnetic Resonance Perfusion-Weighted Imaging and Susceptibility-Weighted Imaging and Mapping

The cerebral vasculature, along with neurons and axons, is vulnerable to biomechanical insult during traumatic brain injury (TBI). Trauma-induced vascular injury is still an underinvestigated area in TBI research. Cerebral blood flow and metabolism could be important future treatment targets in neural critical care. Magnetic resonance imaging offers a number of key methods to probe vascular injury and its relationship with traumatic hemorrhage, perfusion deficits, venous blood oxygen saturation changes, and resultant tissue damage. They make it possible to image the hemodynamics of the brain, monitor regional damage, and potentially show changes induced in the brain's function not only acutely but also longitudinally following treatment. These methods have recently been used to show that even mild TBI (mTBI) subjects can have vascular abnormalities, and thus they provide a major step forward in better diagnosing mTBI patients.

Brain microbleeds: Epidemiology and clinical implications

INTRODUCTION

Brain microbleeds (BMB) are haemosiderin deposits contained within macrophages, which are displayed as hypointense images in some T2-weighted magnetic resonance imaging sequences. There are still many questions to be answered about the pathophysiology and clinical relevance of BMB.

DEVELOPMENT

We conducted a literature review of the main epidemiological, clinical, and anatomical pathology studies of BMB performed in the general population, in patients at risk of or already suffering from a vascular disease, and in patients with cognitive impairment. We analysed the prevalence of BMB, risk factors, and potential pathophysiological mechanisms and clinical implications.

CONCLUSIONS

The prevalence of BMB is highly variable (3%-27% in the general population, 6%-80% in patients with vascular risk factors or vascular disease, and 16%-45% in patients with cognitive impairment). BMB are associated with ageing, Alzheimer disease (AD), and in particular haemorrhagic or ischaemic cerebrovascular disease. The pathological substrate of BMB is either lipohyalinosis (subcortical BMB) or cerebral amyloid angiopathy (lobar BMB). BMB exacerbate cognitive impairment, possibly through cortical-subcortical and intracortical disconnection, and increase the risk of death, mostly due to vascular causes. BMB also increase the risk of cerebral haemorrhage, particularly in patients with multiple lobar BMB (probable erebral amyloid angiopathy). Therefore, anticoagulant treatment may be contraindicated in these patients. In patients with lower risk of bleeding, the new oral anticoagulants and the combination of clinical and magnetic resonance imaging follow-up could be helpful in the decision-making process.

Amyloid-related imaging abnormalities-haemosiderin (ARIA-H) in patients with Alzheimer's disease treated with bapineuzumab: a historical, prospective secondary analysis

BACKGROUND

Amyloid-related imaging abnormalities due to haemosiderin deposition (ARIA-H) occur in patients with mild to moderate dementia due to Alzheimer's disease (AD) and have been reported with increased incidence in clinical trials of amyloid-lowering therapies under development for AD.

OBJECTIVE

Our objective was to explore the relationship between the incidences of ARIA-H during treatment with placebo and different doses of bapineuzumab, a humanised monoclonal antibody directed against amyloid β.

METHODS

Two neuroradiologists independently reviewed 2572 GRE/T2* MRI sequences from 262 participants in two phase two clinical trials of bapineuzumab and an open-label extension study. Readers were blinded to the participant's therapy, APOE ε4 genotype and medical history.

RESULTS

Several risk factors for small ARIA-H <10 mm (microhaemorrhages) were identified: APOE ε4, bapineuzumab treatment, pre-existing small ARIA-H and use of antithrombotics. The HR (95%CI) for incident ARIA-H <10 mm associated with the number of APOE ε4 alleles was 11.9 (3.3 to 42.5) for 2 versus no alleles and 3.5 (1.0 to 12.0) for 1 versus no allele. The HR for bapineuzumab therapy was 3.5 (1.0 to 12.0); for the presence of baseline ARIA-H <10 mm, it was 3.5 (1.6 to 7.8), and for the use of antithrombotic agents it was 2.2 (1.0 to 4.8). The incidence rate for ARIA-H <10 mm was elevated only in the initial 6 months of active treatment and declined after this interval to a rate similar to that observed in the group treated with placebo.

CONCLUSIONS

ARIA-H represents a spectrum of MRI findings due to haemosiderin deposition that appears to be related to impaired vascular integrity. The increased risk for ARIA-H associated with APOE ε4 allele frequency, pre-existing ARIA-H, treatment with bapineuzumab and use of antithrombotic agents provides additional support for this hypothesis of loss of integrity of cerebral vessels due to amyloid burden.

TRIAL REGISTRATION

NCT00112073 and NCT00606476.

Prevalence of Brain Microbleeds in Alzheimer Disease: A Systematic Review and Meta-Analysis on the Influence of Neuroimaging Techniques

BACKGROUND AND PURPOSE

The literature on the prevalence of Alzheimer disease-associated cerebral microbleeds assessed with MR imaging shows considerable heterogeneity in terms of imaging techniques and parameters. Our aim was to perform a meta-analysis of the role of imaging techniques, including image acquisition, field strength and scanner type, and clinical and demographic factors on the reported prevalence of microbleeds in Alzheimer disease.

MATERIALS AND METHODS

The prevalence of microbleeds was examined with respect to a priori-selected moderating variables via meta-analytic tools of literature reports.

RESULTS

Fourteen unique studies providing 15 microbleed prevalence rates met the selection criteria for inclusion. The aggregate prevalence of microbleeds was 24% (95% CI, 19%-28%). Scan (SWI = 40%, gradient echo = 18%, EPI = 19%) and field strength (slope = 0.39; standard error = 15, P < .01) influenced the prevalence of microbleeds. The associations between microbleeds and age, sex, and global cognitive status were not significant. After updating the literature, the aggregate prevalence remained in the 95% CI range.

CONCLUSIONS

Imaging technique and field strength are strongly associated with the prevalence of microbleeds over the global aggregate. Standardized imaging protocols for identification of microbleeds are recommended to minimize confounds.