Vascular cognitive impairment

Impact of regional white matter lesions on cognitive function in subcortical vascular cognitive impairment

OBJECTIVES

Exact characterization and localization of white matter lesions (WMLs) as they relate and contribute to vascular cognitive impairment is highly debated. The purpose of this study was to investigate the impact of WML on cognitive function by using a new anatomy-based classification method.

METHODS

We detected WML accurately by using a three-dimensional fluid-attenuated inversion recovery (3D FLAIR) imaging technique and subsequently segmented WMLs by using an anatomy-based method. Participants included 56 consecutive patients diagnosed with subcortical vascular cognitive impairment (SubVCI). The volume of WMLs in different anatomic regions was measured. The volume of the hippocampus, the corpus callosum (CC), any lacunar infarcts, total gray matter (GM), and total brain volumes were also calculated.

RESULTS

Hippocampal (P  =  0.005) as well as temporal WML volumes (P  =  0.039) were both independently associated with mini-mental state examination (MMSE) score. Only the parietal WML volume (P  =  0.000) was independently associated with Montreal Cognitive Assessment (MoCA) score. Frontal WMLs were independently correlated with executive function. Occipital WMLs were independently associated with visuospatial and recall function. Language impairment was independently correlated with both parietal GM and parietal WML volume. Functions related to orientation were independently associated with parietal WML volume.

DISCUSSION

The volume of WMLs in the temporal region as well as in the hippocampus were both independently associated with MMSE score. For the MoCA score, however, only parietal WML volumes were independently correlated. White matter lesions within different anatomic regions were separately correlated with different subdomains of cognitive function.

Mild cognitive impairment, risk factors and magnetic resonance volumetry: role of probable Alzheimer's disease in the family

BACKGROUND/AIMS

Late-onset Alzheimer's disease (LOAD) comprises sporadic LOAD and familial LOAD. We wanted to determine whether total plasma homocysteine (Hcy), cardiovascular risk factors and volumetric analyses of cerebral magnetic resonance imaging (MRI) were differently associated with mild cognitive impairment (MCI) in subjects from families with aggregation of LOAD (probable familial LOAD) and MCI in subjects from families without LOAD (probable sporadic LOAD).

METHODS

A total of 103 subjects with MCI without known stroke or other apparent causative diseases were included as cases together with 58 controls. The cases were stratified into 3 groups according to the number of biological relatives with probable LOAD on one side of the family. Cerebral MRI was obtained from all. The case groups were compared to the control group in sex-specific analyses of covariance.

RESULTS

Hcy was significantly elevated in all cases compared to controls, except for women with probable familial LOAD. These women also had significantly smaller hippocampal volume and significantly larger lateral ventricles, unlike the women in the other case groups.

CONCLUSIONS

Our findings suggest that research on Hcy, cardiovascular risk factors and other potential risk factors for LOAD might benefit from distinguishing between sporadic and familial LOAD.

Abnormal intrinsic brain activity patterns in patients with subcortical ischemic vascular dementia

Objectives

To investigate the amplitude of low-frequency fluctuations (ALFF) alteration of whole brain in patients with subcortical ischemic vascular dementia (SIVD).

Materials and Methods

Thirty patients with SIVD and 35 control subjects were included in this study. All of them underwent structural MRI and rs-fMRI scan. The structural data were processed using the voxel-based morphometry 8 toolbox (VBM8). The rs-fMRI data were processed using Statistical Parametric Mapping (SPM8) and Data Processing Assistant for Resting-State fMRI (DPARSF) software. Within-group analysis was performed with a one-sample Student's t-test to identify brain regions with ALFF value larger than the mean. Intergroup analysis was performed with a two-sample Student's t-test to identify ALFF differences of whole brain between SIVD and control subjects. Partial correlations between ALFF values and Montreal Cognitive Assessment (MoCA) and Mini-Mental State Examination (MMSE) scores were analyzed in the SIVD group across the parameters of age, gender, years of education, and GM volume.

Results

Within-group analysis showed that the bilateral anterior cingulate cortex (ACC), posterior cingulate cortex, medial prefrontal cortex (MPFC), inferior parietal lobe (IPL), occipital lobe, and adjacent precuneus had significantly higher standardized ALFF values than the global mean ALFF value in both groups. Compared to the controls, patients with SIVD presented lower ALFF values in the bilateral precuneus and higher ALFF values in the bilateral ACC, left insula and hippocampus. Including GM volume as an extra covariate, the ALFF inter-group difference exhibited highly similar spatial patterns to those without GM volume correcting. Close negative correlations were found between the ALFF values of left insula and the MoCA and MMSE scores of SIVD patients.

Conclusion

SIVD is associated with a unique spontaneous aberrant activity of rs-fMRI signals, and measurement of ALFF in the precuneus, ACC, insula, and hippocampus may aid in the detection of SIVD.

Vascular cognitive impairment, dementia, aging and energy demand. A vicious cycle

To a great extent, cognitive health depends on cerebrovascular health and a deeper understanding of the subtle interactions between cerebrovascular function and cognition is needed to protect humans from one of the most devastating affliction, dementia. However, the underlying biological mechanisms are still not completely clear. Many studies demonstrated that the neurovascular unit is compromised in cerebrovascular diseases and also in other types of dementia. The hemodynamic neurovascular coupling ensures a strong increase of the cerebral blood flow (CBF) and an acute increase in neuronal glucose uptake upon increased neural activity. Dysfunction of cerebral autoregulation with increasing age along with age-related structural and functional alterations in cerebral blood vessels including accumulation of amyloid-beta (Aβ) in the media of cortical arterioles, neurovascular uncoupling due to astrocyte endfeet retraction, impairs the CBF and increases the neuronal degeneration and susceptibility to hypoxia and ischemia. A decreased cerebral glucose metabolism is an early event in Alzheimer's disease (AD) pathology and may precede the neuropathological Aβ deposition associated with AD. Aβ accumulation in turn leads to further decreases in the CBF closing the vicious cycle. Alzheimer, aging and diabetes are also influenced by insulin/insulin-like growth factor-1 signaling, and accumulated evidence indicates sporadic AD is associated with disturbed brain insulin metabolism. Understanding how vascular and metabolic factors interfere with progressive loss of functional neuronal networks becomes essential to develop efficient drugs to prevent cognitive decline in elderly.

Vascular aspects of cognitive impairment and dementia

Hypertension and stroke are highly prevalent risk factors for cognitive impairment and dementia. Alzheimer's disease (AD) and vascular dementia (VaD) are the most common forms of dementia, and both conditions are preceded by a stage of cognitive impairment. Stroke is a major risk factor for the development of vascular cognitive impairment (VCI) and VaD; however, stroke may also predispose to AD. Hypertension is a major risk factor for stroke, thus linking hypertension to VCI and VaD, but hypertension is also an important risk factor for AD. Reducing these two major, but modifiable, risk factors-hypertension and stroke-could be a successful strategy for reducing the public health burden of cognitive impairment and dementia. Intake of long-chain omega-3 polyunsaturated fatty acids (LC-n3-FA) and the manipulation of factors involved in the renin-angiotensin system (e.g. angiotensin II or angiotensin-converting enzyme) have been shown to reduce the risk of developing hypertension and stroke, thereby reducing dementia risk. This paper will review the research conducted on the relationship between hypertension, stroke, and dementia and also on the impact of LC-n3-FA or antihypertensive treatments on risk factors for VCI, VaD, and AD.

The changing landscape of voltage-gated calcium channels in neurovascular disorders and in neurodegenerative diseases

It is a common belief that voltage-gated calcium channels (VGCC) cannot carry toxic amounts of Ca²⁺ in neurons. Also, some of them as L-type channels are essential for Ca²⁺-dependent regulation of prosurvival gene-programs. However, a wealth of data show a beneficial effect of drugs acting on VGCCs in several neurodegenerative and neurovascular diseases. In the present review, we explore several mechanisms by which the “harmless” VGCCs may become “toxic” for neurons. These mechanisms could explain how, though usually required for neuronal survival, VGCCs may take part in neurodegeneration. We will present evidence showing that VGCCs can carry toxic Ca²⁺ when: a) their density or activity increases because of aging, chronic hypoxia or exposure to β-amyloid peptides or b) Ca²⁺-dependent action potentials carry high Ca²⁺ loads in pacemaker neurons. Besides, we will examine conditions in which VGCCs promote neuronal cell death without carrying excess Ca²⁺. This can happen, for instance, when they carry metal ions into the neuronal cytoplasm or when a pathological decrease in their activity weakens Ca²⁺-dependent prosurvival gene programs. Finally, we will explore the role of VGCCs in the control of nonneuronal cells that take part to neurodegeneration like those of the neurovascular unit or of microglia.

Cognitive impairment and "invisible symptoms" are not associated with CCSVI in MS

BACKGROUND

We investigated the association between chronic cerebrospinal venous insufficiency (CCSVI) and cognitive impairment (CI) in multiple sclerosis (MS). Moreover, we evaluated the association between CCSVI and other frequent self-reported MS symptoms.

METHODS

We looked at the presence of CI in incident MS patients with CCVSI in a population-based cohort of Catania, Italy. All subjects were group-matched by age, sex, disease duration and EDSS score with MS patients without CCSVI, serving as controls. CI was assessed with the Brief Repeatable Battery (BRB) and the Stroop Test (ST) and it was defined by the presence of at least three impaired tests. Fatigue and depressive symptoms were assessed with Fatigue Severity Scale (FSS) and Hamilton Depressive Rating Scale (HDRS), respectively. Bladder and sexual symptoms were assessed with the respective items of the Italian version of Guy's Neurological Disability Scale (GNDS). Quality of life was evaluated with Multiple Sclerosis Quality of Life-54 Instrument (MSQOL-54).

RESULTS

Out of 61 MS patients enrolled in the study, 27 were CCSVI positive and 34 were CCSVI negative. Of them, 43 were women (70.5%); the mean age was 43.9 ± 11.8 years; the mean disease duration was 159.7 ± 113.7 months; mean EDSS was 3.0 ± 2.6. Of them, 36 (59.0%) were classified relapsing-remitting (RR), 12 (19.7%) secondary progressive (SP), seven (11.5%) primary progressive (PP) and six (9.3%) Clinically Isolated Syndrome (CIS). Overall, CI was detected in 29/61 (47.5%) MS patients; particularly 13/27 (48.1%) in the CCSVI positive group and 16/34 (47.0%) in the CCSVI negative group. Presence of CCSVI was not significantly associated with the presence of CI (OR 1.04; 95% CI 0.37-2.87; p-value = 0.9). Not significant differences were found between the two groups regarding the other MS symptoms investigated.

CONCLUSIONS

Our findings suggest a lack of association between CCSVI and CI in MS patients. Fatigue, depressive, bladder/sexual symptoms and self-reported quality of life are not associated with CCSVI.

Pathology and pathogenesis of vascular cognitive impairment-a critical update

Vascular cognitive impairment (VCI) [vascular cognitive disorder (VCD), vascular dementia] describes a continuum of cognitive disorders ranging from mild cognitive impairment (MCI) to dementia, in which vascular brain injury involving regions important for memory, cognition and behavior plays an important role. Clinical diagnostic criteria show moderate sensitivity (ca 50%) and variable specificity (range 64-98%). In Western clinical series, VaD is suggested in 8-10% of cognitively impaired elderly subjects. Its prevalence in autopsy series varies from 0.03 to 58%, with means of 8 to 15% (in Japan 22-35%). Major types of sporadic VaD are multi-infarct encephalopathy, small vessel and strategic infarct type dementias, subcortical arteriosclerotic leukoencephalopathy (SAE) (Binswanger), multilacunar state, mixed cortico-subcortical type, granular cortical atrophy (rare), postischemic encephalopathy, and a mixture of cerebrovascular lesions (CVLs). They result from systemic, cardiac and local large or small vessel disease (SVD); their pathogenesis is multifactorial. Hereditary forms of VaD caused by gene mutations are rare. Cognitive decline is commonly associated with widespread small ischemic vascular lesions involving subcortical brain areas (basal ganglia and hemispheral white matter). The lesions affect neuronal networks involved in cognition, memory, and behavior (thalamo-cortical, striato-subfrontal, cortico-subcortical, limbic systems). CVLs often coexist with Alzheimer-type lesions and other pathologies; 25-80% of elderly demented show mixed pathologies. The lesion pattern of "pure" VaD differs from that in mixed dementia (AD + CVLs) suggesting different pathogenesis of both phenotypes. Minor CVLs, except for severe amyloid angiopathy, appear not essential for cognitive impairment in full-blown AD, while both mild AD-type pathology and SVD may interact synergistically in promoting dementia. However, in a large percentage of non-demented elderly individuals, both AD-related and vascular brain pathologies have been reported. Despite recent suggestions for staging and grading CVLs in specific brain areas, due to the high variability of CVLs associated with cognitive impairment, no validated neuropathological criteria are currently available for VaD and mixed dementia. Further clinico-pathological studies and harmonization of neuropathological procedures are needed to validate the diagnostic criteria for VaD and mixed dementia in order to clarify the impact of CVLs and other coexistent pathologies on cognitive impairment as a basis for further successful therapeutic options.

Oligodendrocyte precursors induce early blood-brain barrier opening after white matter injury

Oligodendrocyte precursor cells (OPCs) are thought to maintain homeostasis and contribute to long-term repair in adult white matter; however, their roles in the acute phase after brain injury remain unclear. Mice that were subjected to prolonged cerebral hypoperfusion stress developed white matter demyelination over time. Prior to demyelination, we detected increased MMP9 expression, blood-brain barrier (BBB) leakage, and neutrophil infiltration in damaged white matter. Notably, at this early stage, OPCs made up the majority of MMP9-expressing cells. The standard MMP inhibitor GM6001 reduced the early BBB leakage and neutrophil infiltration, indicating that OPC-derived MMP9 induced early BBB disruption after white matter injury. Cell-culture experiments confirmed that OPCs secreted MMP9 under pathological conditions, and conditioned medium prepared from the stressed OPCs weakened endothelial barrier tightness in vitro. Our study reveals that OPCs can rapidly respond to white matter injury and produce MMP9 that disrupts the BBB, indicating that OPCs may mediate injury in white matter under disease conditions.

Transient neurological symptoms in the older population: report of a prospective cohort study--the Medical Research Council Cognitive Function and Ageing Study (CFAS)

OBJECTIVE

Transient ischaemic attack (TIA) is a recognised risk factor for stroke in the older population requiring timely assessment and treatment by a specialist. The need for such TIA services is driven by the epidemiology of transient neurological symptoms, which may not be caused by TIA. We report prevalence and incidence of transient neurological symptoms in a large UK cohort study of older people.

DESIGN

Longitudinal cohort study

SETTING

The Medical Research Council Cognitive Function and Aging Study (CFAS) is a population representative study based on six centres across England and Wales.

PARTICIPANTS

Random samples of people in their 65th year were obtained from Family Health Service Authority lists. The participation rate was 80% (n=13 004). Interview at baseline included questions about stroke and three transient neurological symptoms, repeated in a subsample after 2 years. Patients were flagged for mortality.

MAIN OUTCOME MEASURES

Prevalence and 2-year incidence of transient neurological symptoms.

RESULTS

In 11 903 participants without a history of stroke, 271 (2.3%) reported transient problems with speech, 872 (7.6%) with sight and 596 (5.1%) weakness in a limb with 1456 (12.7%) reporting at least one symptom. Of those reinterviewed (n=6748), 675 (9.8%) reported at least one symptom over 2 years.

CONCLUSIONS

Lifetime prevalence and incidence of transient neurological symptoms in people aged 65 years and over is high and is substantially greater than the incidence of TIA in hospital-based and population-based studies. These high rates of transient neurological symptoms in the community in the older population should be considered when planning TIA services.

National Institute on Aging-Alzheimer's Association guidelines for the neuropathologic assessment of Alzheimer's disease

A consensus panel from the United States and Europe was convened recently to update and revise the 1997 consensus guidelines for the neuropathologic evaluation of Alzheimer's disease (AD) and other diseases of brain that are common in the elderly. The new guidelines recognize the pre-clinical stage of AD, enhance the assessment of AD to include amyloid accumulation as well as neurofibrillary change and neuritic plaques, establish protocols for the neuropathologic assessment of Lewy body disease, vascular brain injury, hippocampal sclerosis, and TDP-43 inclusions, and recommend standard approaches for the workup of cases and their clinico-pathologic correlation.

Microvascular brain damage with aging and hypertension: pathophysiological consideration and clinical implications

Loss of cognitive function and hypertension are two common conditions in the elderly and both significantly contribute to loss of personal independency. Microvascular brain damage - the result of age-associated alteration in large arteries and the progressive mismatch of their cross-talk with small cerebral arteries - represents a potent risk factor for cognitive decline and for the onset of dementia in older individuals. The present review discusses the complexity of factors linking large artery to microvascular brain disease and to cognitive decline and the evidence for possible clinical markers useful for prevention of this phenomenon. The possibility of dementia prevention by cardiovascular risk factors control has not been demonstrated. In the absence of research clinical trials specifically and primarily designed to demonstrate the antihypertensive treatment efficacy for reducing the risk of dementia, further evidence demonstrating that it is possible to limit the progression of microvascular brain damage is needed.

Pathologic lesions in neurodegenerative diseases

This chapter will discuss two of the most widely used approaches to assessing brain structure: neuroimaging and neuropathology. Whereas neuropathologic approaches to studying the central nervous system have been utilized for many decades and have provided insights into morphologic correlates of dementia for over 100 years, accurate structural imaging techniques "blossomed" with the development and refinement of computerized tomographic scanning and magnetic resonance imaging (MRI), beginning in the late 1970s. As Alzheimer disease progresses over time, there is progressive atrophy of the hippocampus and neocortex--this can be quantified and regional accentuation of the atrophy can be evaluated using quantitative MRI scanning. Furthermore, ligands for amyloid proteins have recently been developed--these can be used in positron emission tomography studies to localize amyloid proteins, and (in theory) study the dynamics of their deposition (and clearance) within the brain over time. Neuropathologic studies of the brain, using highly specific antibodies, can demonstrate synapse loss and the deposition of proteins important in AD progression--specifically ABeta and phosphor-tau. Finally, neuropathologic assessment of (autopsy) brain specimens can provide important correlation with sophisticated neuroimaging techniques.

National Institute on Aging-Alzheimer's Association guidelines for the neuropathologic assessment of Alzheimer's disease: a practical approach

We present a practical guide for the implementation of recently revised National Institute on Aging-Alzheimer's Association guidelines for the neuropathologic assessment of Alzheimer's disease (AD). Major revisions from previous consensus criteria are: (1) recognition that AD neuropathologic changes may occur in the apparent absence of cognitive impairment, (2) an "ABC" score for AD neuropathologic change that incorporates histopathologic assessments of amyloid β deposits (A), staging of neurofibrillary tangles (B), and scoring of neuritic plaques (C), and (3) more detailed approaches for assessing commonly co-morbid conditions such as Lewy body disease, vascular brain injury, hippocampal sclerosis, and TAR DNA binding protein (TDP)-43 immunoreactive inclusions. Recommendations also are made for the minimum sampling of brain, preferred staining methods with acceptable alternatives, reporting of results, and clinico-pathologic correlations.

Vascular contributions to cognitive impairment and dementia: a statement for healthcare professionals from the american heart association/american stroke association

BACKGROUND AND PURPOSE

This scientific statement provides an overview of the evidence on vascular contributions to cognitive impairment and dementia. Vascular contributions to cognitive impairment and dementia of later life are common. Definitions of vascular cognitive impairment (VCI), neuropathology, basic science and pathophysiological aspects, role of neuroimaging and vascular and other associated risk factors, and potential opportunities for prevention and treatment are reviewed. This statement serves as an overall guide for practitioners to gain a better understanding of VCI and dementia, prevention, and treatment.

METHODS

Writing group members were nominated by the writing group co-chairs on the basis of their previous work in relevant topic areas and were approved by the American Heart Association Stroke Council Scientific Statement Oversight Committee, the Council on Epidemiology and Prevention, and the Manuscript Oversight Committee. The writing group used systematic literature reviews (primarily covering publications from 1990 to May 1, 2010), previously published guidelines, personal files, and expert opinion to summarize existing evidence, indicate gaps in current knowledge, and, when appropriate, formulate recommendations using standard American Heart Association criteria. All members of the writing group had the opportunity to comment on the recommendations and approved the final version of this document. After peer review by the American Heart Association, as well as review by the Stroke Council leadership, Council on Epidemiology and Prevention Council, and Scientific Statements Oversight Committee, the statement was approved by the American Heart Association Science Advisory and Coordinating Committee.

RESULTS

The construct of VCI has been introduced to capture the entire spectrum of cognitive disorders associated with all forms of cerebral vascular brain injury-not solely stroke-ranging from mild cognitive impairment through fully developed dementia. Dysfunction of the neurovascular unit and mechanisms regulating cerebral blood flow are likely to be important components of the pathophysiological processes underlying VCI. Cerebral amyloid angiopathy is emerging as an important marker of risk for Alzheimer disease, microinfarction, microhemorrhage and macrohemorrhage of the brain, and VCI. The neuropathology of cognitive impairment in later life is often a mixture of Alzheimer disease and microvascular brain damage, which may overlap and synergize to heighten the risk of cognitive impairment. In this regard, magnetic resonance imaging and other neuroimaging techniques play an important role in the definition and detection of VCI and provide evidence that subcortical forms of VCI with white matter hyperintensities and small deep infarcts are common. In many cases, risk markers for VCI are the same as traditional risk factors for stroke. These risks may include but are not limited to atrial fibrillation, hypertension, diabetes mellitus, and hypercholesterolemia. Furthermore, these same vascular risk factors may be risk markers for Alzheimer disease. Carotid intimal-medial thickness and arterial stiffness are emerging as markers of arterial aging and may serve as risk markers for VCI. Currently, no specific treatments for VCI have been approved by the US Food and Drug Administration. However, detection and control of the traditional risk factors for stroke and cardiovascular disease may be effective in the prevention of VCI, even in older people.

CONCLUSIONS

Vascular contributions to cognitive impairment and dementia are important. Understanding of VCI has evolved substantially in recent years, based on preclinical, neuropathologic, neuroimaging, physiological, and epidemiological studies. Transdisciplinary, translational, and transactional approaches are recommended to further our understanding of this entity and to better characterize its neuropsychological profile. There is a need for prospective, quantitative, clinical-pathological-neuroimaging studies to improve knowledge of the pathological basis of neuroimaging change and the complex interplay between vascular and Alzheimer disease pathologies in the evolution of clinical VCI and Alzheimer disease. Long-term vascular risk marker interventional studies beginning as early as midlife may be required to prevent or postpone the onset of VCI and Alzheimer disease. Studies of intensive reduction of vascular risk factors in high-risk groups are another important avenue of research.

Pumps, aqueducts, and drought management: vascular physiology in vascular cognitive impairment

Vascular cognitive impairment has been traditionally defined by structural pathology, an accumulation of infarcts, leading to progressive cognitive decline. Recent evidence, however, suggests that cognitive impairment may be independently mediated by hemodynamic dysfunction, including global and hemispheral hypoperfusion and altered cerebral blood flow regulation. In this review, we examine evidence for the contribution of hemodynamic impairment to cognitive dysfunction in the setting of large vessel disease, cardiac failure, and microvascular disease. If there is a hemodynamic component of vascular cognitive impairment, then treatments proposed to correct impaired vascular physiology may reasonably be expected to treat the cognitive dysfunction as well.

Synapse loss in dementias

Synaptic transmission is essential for nervous system function, and its dysfunction is a known major contributing factor to Alzheimer's-type dementia. Antigen-specific immunochemical methods are able to characterize synapse loss in dementia through the quantification of various synaptic proteins involved in the synaptic cycle. These immunochemical methods applied to the study of Alzheimer's disease (AD) brain specimens have correlated synaptic loss with particularly toxic forms of amyloid-beta protein and have also established synapse loss as the best correlate of dementia severity. A significant but comparatively circumscribed amount of literature describes synaptic decline in other forms of dementia. Ischemic vascular dementia (IVD) is quite heterogeneous, and synapse loss in IVD seems to be variable among IVD subtypes, probably reflecting its variable neuropathologic correlates. Loss of synaptic protein has been identified in vascular dementia of the Binswanger type and Spatz-Lindenberg's disease. Here we demonstrate a significant loss of synaptophysin density within the temporal lobe of frontotemporal dementia (FTD) patients.

Aging and cerebrovascular dysfunction: contribution of hypertension, cerebral amyloid angiopathy, and immunotherapy

Age-related cerebrovascular dysfunction contributes to ischemic stroke, intracerebral hemorrhages (ICHs), microbleeds, cerebral amyloid angiopathy (CAA), and cognitive decline. Importantly, there is increasing recognition that this dysfunction plays a critical secondary role in many neurodegenerative diseases, including Alzheimer's disease (AD). Atherosclerosis, hypertension, and CAA are the most common causes of blood-brain barrier (BBB) lesions. The accumulation of amyloid beta (Aβ) in the cerebrovascular system is a significant risk factor for ICH and has been linked to endothelial transport failure and blockage of perivascular drainage. Moreover, recent anti-Aβ immunotherapy clinical trials demonstrated efficient clearance of parenchymal amyloid deposits but have been plagued by CAA-associated adverse events. Although management of hypertension and atherosclerosis can reduce the incidence of ICH, there are currently no approved therapies for attenuating CAA. Thus, there is a critical need for new strategies that improve BBB function and limit the development of β-amyloidosis in the cerebral vasculature.

The overlap between neurodegenerative and vascular factors in the pathogenesis of dementia

There is increasing evidence that cerebrovascular dysfunction plays a role not only in vascular causes of cognitive impairment but also in Alzheimer's disease (AD). Vascular risk factors and AD impair the structure and function of cerebral blood vessels and associated cells (neurovascular unit), effects mediated by vascular oxidative stress and inflammation. Injury to the neurovascular unit alters cerebral blood flow regulation, depletes vascular reserves, disrupts the blood-brain barrier, and reduces the brain's repair potential, effects that amplify the brain dysfunction and damage exerted by incident ischemia and coexisting neurodegeneration. Clinical-pathological studies support the notion that vascular lesions aggravate the deleterious effects of AD pathology by reducing the threshold for cognitive impairment and accelerating the pace of the dementia. In the absence of mechanism-based approaches to counteract cognitive dysfunction, targeting vascular risk factors and improving cerebrovascular health offers the opportunity to mitigate the impact of one of the most disabling human afflictions.

The science of stroke: mechanisms in search of treatments

This review focuses on mechanisms and emerging concepts that drive the science of stroke in a therapeutic direction. Once considered exclusively a disorder of blood vessels, growing evidence has led to the realization that the biological processes underlying stroke are driven by the interaction of neurons, glia, vascular cells, and matrix components, which actively participate in mechanisms of tissue injury and repair. As new targets are identified, new opportunities emerge that build on an appreciation of acute cellular events acting in a broader context of ongoing destructive, protective, and reparative processes. The burden of disease is great, and its magnitude widens as a role for blood vessels and stroke in vascular and nonvascular dementias becomes more clearly established. This review then poses a number of fundamental questions, the answers to which may generate new directions for research and possibly new treatments that could reduce the impact of this enormous economic and societal burden.

The diagnosis of young-onset dementia

A diagnosis of dementia is devastating at any age but diagnosis in younger patients presents a particular challenge. The differential diagnosis is broad as late presentation of metabolic disease is common and the burden of inherited dementia is higher in these patients than in patients with late-onset dementia. The presentation of the common degenerative diseases of late life, such as Alzheimer's disease, can be different when presenting in the fifth or sixth decade. Moreover, many of the young-onset dementias are treatable. The identification of causative genes for many of the inherited degenerative dementias has led to an understanding of the molecular pathology, which is also applicable to later-onset sporadic disease. This understanding offers the potential for future treatments to be tailored to a specific diagnosis of both young-onset and late-onset dementia.

Cerebrospinal fluid biomarkers in mild cognitive impairment and dementia

Given the magnitude of the public health problem of dementia in the elderly, there is a pressing need for research, development, and timely application of biomarkers that will identify latent and prodromal illness as well as dementia. Although identification of risk factors and neuroimaging measures will remain key to these efforts, this review focuses on recent progress in the discovery, validation, and standardization of cerebrospinal fluid (CSF) biomarkers, small molecules and macromolecules whose CSF concentration can aid in diagnosis at different stages of disease as well as in assessment of disease progression and response to therapeutics. A multimodal approach that brings independent information from risk factor assessment, neuroimaging, and biomarkers may soon guide physicians in the early diagnosis and management of cognitive impairment in the elderly.

Neuropathology in the adult changes in thought study: a review

The neuropathology underlying dementia syndromes in older populations is complex. The contributions of Alzheimer's and Lewy body pathology are well appreciated. Recent studies with brain autopsies have highlighted the high prevalence of vascular disease as an independent, but often co-morbid contributor to dementia. The Adult Changes in Thought Study is a community-based, longitudinal study of brain aging and cognitive decline which has recently confirmed cerebral microinfarcts as a strong correlate of cognitive impairment and dementia. This study examines correlations between clinical characteristics including extensive, longitudinal medication histories, and longitudinal cognitive testing against structural and biochemical features of disease.

Serum inflammatory proteins and frontal lobe dysfunction in patients with cardiovascular risk factors

BACKGROUND

Recent studies have shown that the levels of circulating inflammatory markers are associated with cognitive decline and cerebral small-vessel disease. Frontal lobe dysfunction is believed to be a relatively characteristic neuropsychological symptom in vascular cognitive impairment caused by cerebral small-vessel disease. The purpose of this study was to investigate whether the levels of serum inflammatory markers are associated with frontal lobe dysfunction, particularly executive dysfunction.

METHODS

Between January 2003 and September 2007, 388 patients who had one or more atherosclerotic risk factors and subsequently underwent brain MRI and neuropsychological testing including mini-mental state examination (MMSE), frontal assessment battery (FAB), and modified Stroop test were enrolled in this study. We evaluated the effect of serum levels of inflammatory markers and white matter lesions on frontal lobe function.

RESULTS

The FAB score was negatively correlated with serum inflammatory marker levels (hsCRP; r = -0.170, IL-6; r = -0.143, IL-18; r = -0.175) and white matter lesions. In the modified Stroop test, interference measure was positively correlated with the levels of hsCRP (r = -0.198), and IL-18 (r = -0.152), and white matter lesions. However, the MMSE score was not correlated with either inflammatory marker levels. The association between hsCRP and FAB score or interference measure remained significant when controlling for other confounding factors and MRI findings.

CONCLUSIONS

The circulating level of hsCRP is associated with frontal lobe dysfunction in patients with cardiovascular risk factors independent of white matter lesions in brain MRI.

Heterogeneity in mild cognitive impairment: differences in neuropsychological profile and associated white matter lesion pathology

This study examined whether distinct neuropsychological profiles could be delineated in a sample with Mild Cognitive Impairment (MCI) and whether white matter lesion (WML) burden contributed to MCI group differences. A heterogeneous, clinical sample of 70 older adults diagnosed with MCI was assessed using cognitive scores, and WML was quantified using a semi-automated, volumetric approach on T2-weighted fluid-attenuated inversion recovery (FLAIR) images. Using cluster and discriminant analyses, three distinct groups (Memory/Language, Executive/Processing Speed, and Pure Memory) were empirically derived based on cognitive scores. Results also showed a dose dependent relationship of WML burden to MCI subgroup, with the Executive/Processing Speed subgroup demonstrating significantly higher levels of WML pathology when compared to the other subgroups. In addition, there was a dissociation of lesion type by the two most impaired subgroups (Memory/Language and Executive/Processing Speed) such that the Memory/Language subgroup showed higher periventricular lesion (PVL) and lower deep white matter lesion (DWML) volumes, whereas the Executive/Processing Speed demonstrated higher DWML and lower PVL volumes. Results demonstrate that distinct MCI subgroups can be empirically derived and reliably differentiated from a heterogeneous MCI sample, and that these profiles differ according to WML burden. Overall, findings suggest different underlying pathologies within MCI and contribute to our understanding of MCI subtypes.

Cerebral microinfarcts associated with severe cerebral beta-amyloid angiopathy

Cerebral amyloid angiopathy (CAA) is common in elderly individuals, especially those affected with Alzheimer's disease. Eighteen brains with severe SCAA (SCAA) were compared with 21 brains with mild CAA (MCAA) to investigate whether the presence of SCAA in the brains of demented patients was associated with a higher burden of old microinfarcts than those with MCAA. Immunohistochemistry for CD68 was employed to highlight old microinfarcts in tissue blocks from various brain regions. Old microinfarcts, manually counted by light microscopy, were present in 14 of 18 SCAA brains and in 7 of 21 MCAA brains (P = 0.01, two-tailed Fisher's exact test). The average number of old microinfarcts across geographic regions in each brain ranged from 0 to 1.95 (mean rank 24.94, sum of ranks 449) in the SCAA group, and from 0 to 0.35 (mean rank 15.76, sum of ranks 331) in the MCAA group (P = 0.008, two-tailed Mann-Whitney U-test). Frequent old microinfarcts in demented individuals with severe CAA may contribute a vascular component to the cognitive impairment in these patients.

Beyond mild cognitive impairment: vascular cognitive impairment, no dementia (VCIND)

Identifying the causes of dementia is important in the search for effective preventative and treatment strategies. The concept of mild cognitive impairment (MCI), as prodromal dementia, has been useful but remains controversial since in population-based studies it appears to be a limited predictor of progression to dementia. Recognising the relative contribution of neurodegenerative and vascular causes, as well as their interrelationship, may enhance predictive accuracy. The concept of vascular cognitive impairment (VCI) has been introduced to describe the spectrum of cognitive change related to vascular causes from early cognitive decline to dementia. A recent review of this concept highlighted the need for diagnostic criteria that encompass the full range of the VCI construct. However, very little is known regarding the mildest stage of VCI, generally termed 'vascular cognitive impairment, no dementia' (VCIND). Whether mild cognitive change in the context of neurodegenerative pathologies is distinct from that in the context of cerebrovascular diseases is not known. This is key to the definition of VCIND and whether it is possible to identify this state. Distinguishing between vascular (that is, VCIND) and non-vascular (that is, MCI) cognitive disorders and determining how well each might predict dementia may not be possible due to the overlap in pathologies observed in the older population. Here, we review the concept of VCIND in an effort to identify recent developments and areas of controversy in nosology and the application of VCIND for screening individuals at increased risk of dementia secondary to vascular disease and its risk factors.

Current Concepts in Vascular Cognitive Impairment and Pharmacotherapeutic Implications

Objective:

To review evolution of the vascular cognitive impairment (VCI) construct, including diagnosis, pharmacotherapeutic implications, and address challenges that will shape future developments.

Data Sources:

Literature retrieval was accessed through PubMed, from 1966 to December 2008, using the terms vascular cognitive impairment, vascular dementia, post-stroke dementia, vascular cognitive disorder, mild cognitive impairment, criteria, disease progression, outcomes, treatment, prevention, biomarkers, and neuroimaging.

Study Selection and Data Extraction:

All articles in published English identified from the data sources were evaluated for inclusion. Regarding pharmacotherapy, prospective double-blind, placebo-controlled studies were included as well as extensions or relevant post hoc analyses.

Data Synthesis:

In the 1970s, “senile dementia due to hardening of the arteries” was used to describe dementia due to vascular causes. This was a narrow view of what is now known to be a common form of cognitive impairment in older people. Multiple infarct dementia (MID) was first proposed to describe dementia attributable to multiple cerebral infarcts, followed by the vascular dementia (VaD) construct, itself meant to be an improvement over MID. The VaD construct had limitations, not the least of which was that, by the time a patient was diagnosed with VaD, the opportunity for prevention was lost. Thus arose the concept of VCI, representing a group of heterogeneous disorders that share presumed vascular causes. The importance of VCI is centered on the fact that vascular risk factors are treatable, and thus should lead to a reduction in the incidence of cognitive impairment due to vascular causes. There is evidence that treatment of hypertension can lead to a reduction in the incidence of cognitive impairment and dementia, and that treatment of VaD with acetylcholinesterase inhibitors may be beneficial.

Conclusions:

Careful attention needs to be given to controlling vascular risk factors in at-risk patients. Pharmacists should play an active role in this important area of geriatric pharmacotherapy.

Dementia and suicidal behavior: a review of the literature

BACKGROUND

While dementia is more common in older people and suicide rates in many countries are higher among the elderly, there is some doubt about the association between these two phenomena.

METHODS

A search of the major relevant databases was carried out to examine the evidence for this possible association.

RESULTS

The association between dementia and suicide and also non-fatal self-harm did not appear strong but many studies have significant methodological limitations and there are few studies of suicide or self-harm in vascular, frontotemporal, Lewy body and HIV dementia where such behavior might be expected to be more common. Rates of self-harm may be increased in mild dementia and are higher before than after predictive testing for Huntington's disease. Overall, the risk of suicide in dementia appears to be the same or less than that of the age-matched general population but is increased soon after diagnosis, in patients diagnosed with dementia during hospitalization and in Huntington's disease. Putative risk factors for suicide in dementia include depression, hopelessness, mild cognitive impairment, preserved insight, younger age and failure to respond to anti-dementia drugs. Large, good quality prospective studies are needed to confirm these findings.

CONCLUSIONS

Further research should be undertaken to examine how rates of suicide and self-harm change during the course of the illness and vary according to the specific sub-type of dementia.

Effect of statins on a wide range of health outcomes: a cohort study validated by comparison with randomized trials

AIMS

To assess the effect of statins on a range of health outcomes.

METHODS

We undertook a population-based cohort study to assess the effect of statins on a range of health outcomes using a propensity score-based method to control for differences between people prescribed and not prescribed statins. We validated our design by comparing our results for vascular outcomes with the effects established in large randomized trials. The study was based on the United Kingdom Health Improvement Network database that includes the computerized medical records of over four and a half million patients.

RESULTS

People who initiated treatment with a statin (n = 129,288) were compared with a matched sample of 600,241 people who did not initiate treatment, with a median follow-up period of 4.4 years. Statin use was not associated with an effect on a wide range of outcomes, including infections, fractures, venous thromboembolism, gastrointestinal haemorrhage, or on specific eye, neurological or autoimmune diseases. A protective effect against dementia was observed (hazard ratio 0.80, 99% confidence interval 0.68, 0.95). There was no effect on the risk of cancer even after > or =8 years of follow-up. The effect sizes for statins on vascular end-points and mortality were comparable to those observed in large randomized trials, suggesting bias and confounding had been well controlled for.

CONCLUSIONS

We found little evidence to support wide-ranging effects of statins on health outcomes beyond their established beneficial effect on vascular disease.

Cerebral white matter: neuroanatomy, clinical neurology, and neurobehavioral correlates

Lesions of the cerebral white matter (WM) result in focal neurobehavioral syndromes, neuropsychiatric phenomena, and dementia. The cerebral WM contains fiber pathways that convey axons linking cerebral cortical areas with each other and with subcortical structures, facilitating the distributed neural circuits that subserve sensorimotor function, intellect, and emotion. Recent neuroanatomical investigations reveal that these neural circuits are topographically linked by five groupings of fiber tracts emanating from every neocortical area: (1) cortico-cortical association fibers; (2) corticostriatal fibers; (3) commissural fibers; and cortico-subcortical pathways to (4) thalamus and (5) pontocerebellar system, brain stem, and/or spinal cord. Lesions of association fibers prevent communication between cortical areas engaged in different domains of behavior. Lesions of subcortical structures or projection/striatal fibers disrupt the contribution of subcortical nodes to behavior. Disconnection syndromes thus result from lesions of the cerebral cortex, subcortical structures, and WM tracts that link the nodes that make up the distributed circuits. The nature and the severity of the clinical manifestations of WM lesions are determined, in large part, by the location of the pathology: discrete neurological and neuropsychiatric symptoms result from focal WM lesions, whereas cognitive impairment across multiple domains--WM dementia--occurs in the setting of diffuse WM disease. We present a detailed review of the conditions affecting WM that produce these neurobehavioral syndromes, and consider the pathophysiology, clinical effects, and broad significance of the effects of aging and vascular compromise on cerebral WM, in an attempt to help further the understanding, diagnosis, and treatment of these disorders.

A population-based study of the association between Trypanosoma cruzi infection and cognitive impairment in old age (the Bambuí Study)

BACKGROUND

Limited clinical data suggest that chronic Trypanosoma cruzi infection, which causes Chagas' disease (ChD), is associated with cognitive impairment. This study investigated this association in a large population-based sample of older adults.

METHODS

Participants in this cross-sectional study comprised 1,449 persons aged > or = 60 years from a Brazilian endemic area (Bambuí). Cognitive functioning was ascertained by the Mini-Mental State Examination (MMSE), considering its score in percentiles [< or =14 (<5th percentile), 15-22 (5th to <25th) and > or =23]. Hypothesized risk factors were T. cruzi infection, ChD-related electrocardiographic (ECG) abnormalities and use of digoxin medication. Potential confounders included depressive symptoms, smoking, stroke, hemoglobin, HDL cholesterol, blood glucose, systolic blood pressure, and use of psychoactive medication.

RESULTS

The prevalence of T. cruzi infection was 37.6%. There was a graded and independent association between infection and the MMSE score (adjusted odds ratios estimated by ordinal logistic regression = 1.99; 95% CI 1.43-2.76). No significant associations between the MMSE score and ECG abnormalities or digoxin medication use were found.

CONCLUSIONS

This study provides for the first time epidemiological evidence of an association between T. cruzi infection and cognitive impairment which was not mediated by either ChD-related ECG abnormalities or digoxin medication use.

A retrospective study of cholinesterase inhibitors for Alzheimer's disease: cerebrovascular disease as a predictor of patient outcomes

BACKGROUND

Dementia may be caused by Alzheimer's disease (AD), cerebrovascular disease (CVD), or a combination of both. When CVD is associated with dementia, survival is thought to be reduced. It is unclear whether treatment with cholinesterase inhibitors (ChEIs), which has been found to slow disease progression in AD patients, has similar benefits in vascular forms of dementia.

OBJECTIVES

The present study was designed to determine whether co-existing CVD is associated with survival or time to nursing home placement (NHP) among AD patients treated with ChEIs. Findings of poorer outcomes in patients with versus without CVD might argue against the use of ChEIs for AD patients in whom CVD co-exists.

METHODS

A retrospective cohort study was undertaken using the Régie de l'Assurance Maladie du Québec (RAMQ) databases to examine the time to NHP or death for AD patients aged 66+, with or without CVD, treated with ChEIs between July 1, 2000, and June 30, 2003. Because ChEIs are approved only for AD in Canada, a ChEI prescription was used as a surrogate for an AD diagnosis. Separate analyses were performed for patients with persistent ChEI use and those who discontinued ChEI therapy.

RESULTS

A total of 4428 patients met inclusion criteria for AD with CVD; 13 512 were classified as having AD alone. For the composite endpoint of NHP or death, 1000-day survival rates were lower among AD patients with versus without CVD (p < 0.01), but absolute differences were very small (84 vs. 86% with continuous ChEI use; 77 vs. 78% with discontinuous ChEI therapy). Of the secondary endpoints, time to death was shorter for patients with versus without CVD, but time to NHP did not differ between groups.

LIMITATIONS

Results may have been affected by selection (misclassification) bias and between-group differences in smoking, body mass index, and duration of ChEI therapy.

CONCLUSIONS

Associations between co-existing CVD and time to NHP or death appeared to be of little clinical relevance among AD patients treated with ChEIs. The lack of difference between AD patients with and without CVD suggests that CVD should not be used as a reason to deny AD patients access to ChEI treatment.

Biomarkers for cognitive impairment and dementia in elderly people

The threat of a looming pandemic of dementia in elderly people highlights the compelling need for the development and validation of biomarkers that can be used to identify pre-clinical and prodromal stages of disease in addition to fully symptomatic dementia. Although predictive risk factors and correlative neuroimaging measures will have important roles in these efforts, this Review describes recent progress in the discovery, validation, and standardisation of molecular biomarkers--small molecules and macromolecules whose concentration in the brain or biological fluids can aid diagnosis at different stages of the more common dementing diseases and in the assessment of disease progression and response to therapeutics. An approach that efficiently combines independent information from risk-factor assessment, neuroimaging measures, and biomarkers might soon guide clinicians in the early diagnosis and management of cognitive impairment in elderly people.

Vascular cognitive impairment: current concepts and clinical developments

Vascular cognitive impairment (VCI) comprises a range of cognitive disorders related to cerebral vessel disease and has generally replaced the term multi-infarct dementia. Despite the heterogeneity of the VCI construct, some clinical patterns can be discerned, which enable subtypes, such as mixed dementia and VCI-no dementia, to be recognised. Diagnostic criteria for vascular dementia do not encompass the full range of the VCI construct, and clinical investigators now recognise the need for harmonised standards to study the many manifestations of VCI seen in daily practice and to inform the development of diagnostic criteria. Although executive dysfunction is a recognised feature of VCI, some data suggest a less exclusive role than was previously proposed. VCI might be preventable, although the evidence for this is not as complete as it is for the prevention of stroke. Future studies into specific therapies for VCI will need to consider the clinical features and outcomes carefully.

Alzheimer’s disease in late-life dementia: A minor toxic consequence of devastating cerebrovascular dysfunction

Alzheimer's disease (AD) is thought to be the most common cause of late-life dementia. But pure AD is infrequent whereas AD pathology is often insufficient to explain dementia in the elderly. Conversely, cerebrovascular disease is omnipresent and the crucial role of microvascular alterations increasingly recognized in late dementia or "Alzheimer syndrome". Pathomechanisms of vascular cognitive impairment are still debated but recent data indicate that the initial concept of chronic low grade cerebral hypoxia should not have been abandoned. Thus, it is proposed that windkessel dysfunction is the missing link between vascular and craniospinal senescence on the one hand, and chronic low grade cerebral hypoxia, "senile brain degeneration" and "Alzheimer syndrome" on the other hand. An age-related decrease in the buffering capacity of both the vessels and the craniospinal cavity favours cerebral hypoxia; due to increased capillary pulsatility with disturbances in capillary exchanges or due to a marked reduction in craniospinal compliance with a mechanical reduction in cerebral arterial inflow. "Invisible" windkessel dysfunction, most often related to "hardening of the arteries" may be the most frequent pathomechanism of late-onset dementia whereas associated mild or moderate AD may be merely a toxic manifestation of a primarily hypoxic disease. Structural patterns of arteriosclerotic dementia fit well with an underlying arterial windkessel dysfunction: with secondary mechanical damage to the cerebral small vessels and the brain and predominantly deep hypoxia. The clinical significance of leukoaraïosis, small foci of necrosis, ventricular dilatation, hippocampal and cortical atrophy is in good agreement with their value as indirect markers of windkessel dysfunction. An age-related "invisible" reduction in craniospinal compliance may also contribute to the associations between heart failure, arterial hypotension and cognitive impairment in the elderly and to the high percentage of dementia of unknown origin in the very old. Both neuropathological and clinical overlap between AD and windkessel dysfunction can explain that cerebrovascular dysfunction remains misdiagnosed for AD in the elderly. Evidence of the key role of cerebrovascular dysfunction should markedly facilitate and widen therapeutic research in late-life dementia. Routine MRI including direct assessment of intracranial dynamics should be increasingly used to define etiological subtypes of the "Alzheimer syndrome" and develop a well-targeted therapeutic strategy.

Pathological correlates of dementia in a longitudinal, population-based sample of aging

OBJECTIVE

Previously published community- or population-based studies of brain aging and dementia with autopsy were restricted to a single sex, a single ethnic group, Roman Catholic clergy, or focused pathological assessments. Our goal was to determine the independent pathological correlates associated with dementia in a typical US population.

METHODS

We evaluated autopsy data from the Adult Changes in Thought study, an ongoing longitudinal, population-based study of brain aging and dementia. Analyses were based on data collected from about 3,400 people 65 years or older who were cognitively intact at the time of enrollment in the Group Health Cooperative in King County, Washington. All consecutive autopsies (n = 221; 20% of deaths) from this cohort were evaluated and analyzed by weighted multivariate analysis to account for potential participation bias.

RESULTS

After adjusting for age, sex, education, and APOE, independent correlates of dementia (relative risk, 95% confidence interval; overall p value) included Braak stage (V/VI vs 0/I/II: 5.89, 1.62-17.60; p < 0.05), number of cerebral microinfarcts in standardized sections (>2 vs none: 4.80, 1.91-10.26; p < 0.001), and neocortical Lewy bodies (any vs none: 5.08, 1.37-18.96; p < 0.05). Estimates of adjusted population attributable risk for these three processes were 45% for Braak stage, 33% for microinfarcts, and 10% for neocortical Lewy bodies.

INTERPRETATION

Our results underscore the therapeutic imperative for Alzheimer's and Lewy body diseases, and provide evidence to support the immediate use of strategies that target cerebral microinfarcts as a means to partially prevent or delay the onset of dementia.