Profiles of neuropsychological impairment in autopsy-defined Alzheimer's disease and cerebrovascular disease

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.

Understanding White Matter Disease

Most strokes are covert and observed incidentally on brain scans, but their presence increases risk of overt stroke and dementia. Amyloid angiopathy, associated with Alzheimer Disease (AD) causes stroke, and when even small strokes coexist with AD, they lower the threshold for dementia. Diffuse ischemic white matter disease impairs executive functioning, information processing speed, and gait. Neuroimaging techniques, such as tissue segmentation, Diffusion Tensor Imaging, MR Spectroscopy, functional MRI and amyloid PET, probe microstructural integrity, molecular biology, and activation patterns, providing new insights into brain-behavior relationships. MR-pathological studies of periventricular hyperintensity (leukoaraiosis) in aging and dementia reveal arteriolar tortuosity, reduced vessel density, and occlusive venous collagenosis which causes venous insufficiency and vasogenic edema. Activated microglia, oligodendroglial apoptosis, clasmatodendritic astrocytosis, and upregulated hypoxia-markers are seen on immunohistochemistry. Further research is needed to understand and treat this chronic subcortical vascular disease, which is epidemic in our aging population.

Neuropsychological assessment of dementia

Neuropsychological studies show that cognitive deficits associated with Alzheimer's disease (AD) are distinct from age-associated cognitive decline. Quantitative and qualitative differences are apparent across many cognitive domains, but are especially obvious in episodic memory (particularly delayed recall), semantic knowledge, and some aspects of executive functions. The qualitatively distinct pattern of deficits is less salient in very old AD patients than in younger AD patients. Although decline in episodic memory is usually the earliest cognitive change that occurs prior to the development of the AD dementia syndrome, asymmetry in cognitive abilities may also occur in this "preclinical" phase of the disease and predict imminent dementia. Discrete patterns of cognitive deficits occur in AD and several neuropathologically distinct age-associated neurodegenerative disorders. Knowledge of these differences helps to clinically distinguish among various causes of dementia and provides useful models for understanding brain-behavior relationships that mediate cognitive abilities affected in various neurodegenerative diseases.

Prevalence and cognitive impact of cerebrovascular findings in Alzheimer's disease: a retrospective, naturalistic study

AIMS

Cerebrovascular disease (CVD) is a major risk factor for cognitive decline associated with progression to Alzheimer's disease (AD) and dementia. The objective of this study was to retrospectively assess the prevalence of CVD and its cognitive impact in patients with AD in everyday clinical practice.

METHODS

Medical notes were retrospectively reviewed for all individuals who presented at East Sussex Memory Clinic (2004-2008) for investigation of cognitive impairment and had brain magnetic resonance imaging (MRI) as part of their clinical work-up. Global cognitive status was assessed with Mini-Mental State Examination (MMSE) and Cambridge Cognitive Examination. The extent of cerebrovascular abnormalities was qualitatively evaluated with MRI.

RESULTS

Notes were reviewed for 232 patients (109 males, 123 females), mean age 76 years (range 62-93), who underwent MRI. Of these, 167 (72%) patients were diagnosed with AD. CVD was present in 89% of AD patients and 47% of patients had moderate to severe cerebrovascular abnormalities. The majority of patients (57%) had MMSE scores in the 21-26 range, indicative of mild AD. There was a trend towards worse cognitive status in patients with more severe CVD, which did not reach significance. Hachinski Ischaemic score indicated these patients did not have vascular dementia (VaD) (mean +/- standard deviation 1.1 +/- 1.3).

CONCLUSION

These findings, based on qualitative MRI, indicate that cerebrovascular pathology is a very common associated feature in patients with mild to moderate AD, without VaD. Although the study suggests that CVD does not contribute to cognitive decline, and is not associated with the development of VaD, a non-significant trend was observed towards worsening cognitive status with increasing severity of CVD. The finding of this trend suggests a need for additional research, especially a prospective quantitative method of assessing CVD, to improve our understanding of how CVD contributes to cognitive impairment in AD.

Regional white matter integrity differentiates between vascular dementia and Alzheimer disease

BACKGROUND AND PURPOSE

Considerable clinical and radiological overlap between vascular dementia (VaD) and Alzheimer disease (AD) often makes the diagnosis difficult. Diffusion-tensor imaging studies showed that fractional anisotropy (FA) could be a useful marker for white matter changes. This study aimed to identify regional FA changes to identify a biomarker that could be used to differentiate VaD from AD.

METHODS

T1-weighted and diffusion-tensor imaging scans were obtained in 13 VaD patients, 16 AD patients, and 22 healthy elderly controls. We used tract-based spatial statistics to study regional changes in fractional anisotropy in AD, VaD, and elderly controls. We then used probabilistic tractography to parcel the corpus callosum in 7 regions according to its connectivity with major cerebral cortices using diffusion-tensor imaging data set. We compared the volume and mean FA in each set of transcallosal fibers between groups using ANOVA and then applied a discriminant analysis based on FA and T2-weighted imaging measures.

RESULTS

FA reduction in forceps minor was the most significant area of difference between AD and VaD. Segmentation of the corpus callosum using tractography and comparison of FA changes of each segment confirmed the FA changes in transcallosal prefrontal tracts of patients with VaD when compared to AD. The best discriminant model was the combination of transcallosal prefrontal FA and Fazekas score with 87.5% accuracy, 100% specificity, and 93% sensitivity (P<0.0001).

CONCLUSIONS

Integrating mean FA in the forceps minor to the Fazekas score provides a useful quantitative marker for differentiating AD from VaD.

Relationship between lesion location and cognitive domains in acute ischemic stroke patients

Localization of brain lesions in acute ischemic stroke has a significant effect on performance in various cognitive domains. The aim of the study was to determine whether there is association between different locations of ischemic brain lesions and different cognitive domains. The study included 40 acute ischemic stroke patients (26 male and 14 female, aged 45-78 years, with 8-16 years of education). Lesion location was visualized using brain computerized tomography, whereas performance in different cognitive domains was assessed using an extensive neuropsychological test battery. The following domains were evaluated: executive function, language, immediate recall, delayed recall, attention, divergent reasoning, and visual-constructive performance in two dimensions. A series of categorical regression analyses were applied. The results showed a significant association between the domains of executive function and language and a set of predictors related to lesion location. Global brain atrophy was found to be a significant partial predictor of performance in all cognitive domains, with higher degrees of global brain atrophy correlating with poorer performance in each of the studied domains. Combined (cortical-subcortical) lesions and unilateral lesions were both found to be significant partial predictors for language, with a higher lesion load being associated with poorer language performance. Combined lesions were also a significant partial predictor for delayed recall, with a higher lesion load correlating with poorer performance in the delayed recall domain.

White matter lesion severity is associated with reduced cognitive performances in patients with normal CSF Abeta42 levels

OBJECTIVE

To identify possible associations between white matter lesions (WML) and cognition in patients with memory complaints, stratified in groups with normal and low cerebrospinal fluid (CSF) Abeta42 values.

MATERIAL AND METHODS

215 consecutive patients with subjective memory complaints were retrospectively included. Patients were stratified into two groups with normal (n = 127) or low (n = 88) CSF Abeta42 levels (cut-off is 450 ng/l). Cognitive scores from the Mini-Mental State Examination (MMSE) and the Neurobehavioral Cognitive Status Examination (Cognistat) were used as continuous dependent variables in linear regression. WML load was used as a continuous independent variable and was scored with a visual rating scale. The regression model was corrected for possible confounding factors.

RESULTS

WML were significantly associated with MMSE and all Cognistat subscores except language (repetition and naming) and attention in patients with normal CSF Abeta42 levels. No significant associations were observed in patients with low CSF Abeta42.

CONCLUSIONS

WML were associated with affection of multiple cognitive domains, including delayed recall and executive functions, in patients with normal CSF Abeta42 levels. The lack of such associations for patients with low CSF Abeta42 (i.e. with evidence for amyloid deposition), suggests that amyloid pathology may obscure cognitive effects of WML.

Metal concentrations in plasma and cerebrospinal fluid in patients with Alzheimer's disease

BACKGROUND/AIMS

The homeostasis of essential metals such as copper, iron, selenium and zinc may be altered in the brain of subjects with Alzheimer's disease (AD).

METHODS

Concentrations of metals (magnesium, calcium, vanadium, manganese, iron, cobalt, nickel, copper, zinc, selenium, rubidium, strontium, molybdenum, cadmium, tin, antimony, cesium, mercury and lead) were determined in plasma and cerebrospinal fluid (CSF) by inductively coupled plasma mass spectrometry in 173 patients with AD and in 87 patients with the combination of AD and minor vascular components (AD + vasc). Comparison was made with 54 healthy controls.

RESULTS

The plasma concentrations of manganese and total mercury were significantly higher in subjects with AD (p < 0.001) and AD + vasc (p <or= 0.013) than in controls. In CSF, however, the concentrations of vanadium, manganese, rubidium, antimony, cesium and lead were significantly lower among subjects with AD (p <or= 0.010) and AD + vasc (p <or= 0.047) than in controls. Strong positive correlations were noted between plasma Cs versus CSF Cs in subjects with AD (r(s) = 0.50; p < 0.001), and AD + vasc (r(s) = 0.68; p < 0.001).

CONCLUSION

Besides the raised plasma mercury concentrations, no consistent metal pattern in plasma or CSF was observed in patients with AD.

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.

Patterns of neuropsychological impairment in MCI patients with small subcortical infarcts or hippocampal atrophy

We investigated whether MCI patients with hippocampal atrophy or multiple subcortical infarcts demonstrate neuropsychological patterns and markers considered typical of Alzheimer's disease (AD) and of vascular dementia (VD), respectively. An extensive neuropsychological battery, including tests of memory, visual-spatial and executive functions, language, attention, praxis and psychomotor speed, was administered to 36 mild cognitive impairment (MCI) patients with hippocampal atrophy and 41 MCI patients with multiple subcortical infarcts. Both groups of MCI patients were very mildly impaired and well matched in terms of MMSE scores. A clear, disproportionately severe, episodic memory disorder was observed in MCI patients with hippocampal atrophy. A less specific neuropsychological profile, consisting of impairment on an Action Naming task that is sensitive to frontal lobe lesions, was observed in MCI patients with multiple subcortical infarcts. In MCI patients, a disproportionately severe episodic memory impairment strongly points to an Alzheimer's type brain pathology, whereas the prevalence of executive deficits and other frontal lobe symptoms are a much weaker diagnostic marker of small vessel subcortical disease.

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.

Subcortical ischemic vascular disease and cognition: A systematic review

Subcortical Ischemic Vascular Disease (SIVD) is underdiagnosed. This review investigates the relationship among SIVD severity, cognitive status and neuroimaging markers.

METHODS

Cohort, cross-sectional and case control studies were searched on ISI, Medline, Scielo, PsychoInfo and LILACS databases published between 1995 and 2006.

RESULTS

The most impaired cognitive domains were executive, attentional and memory retrieval mechanisms. These cognitive features were frequently associated to White Matter Lesions (WML).

CONCLUSIONS

WML is an independent factor in cognitive decline. However, the threshold for this impact is not yet clearly established.

Neuropathological basis of magnetic resonance images in aging and dementia

OBJECTIVE

Magnetic resonance (MR) imaging is used widely for assessment of patients with cognitive impairment, but the pathological correlates are unclear, especially when multiple pathologies are present.

METHODS

This report includes 93 subjects from a longitudinally followed cohort recruited for the study of Alzheimer's disease (AD) and subcortical cerebrovascular disease (CVD). MR images were analyzed to quantify cortical gray matter volume, hippocampal volume, white matter hyperintensities, and lacunes. Neuropathological examination quantified CVD parenchymal pathology, AD pathology (defined as Consortium to Establish a Registry for Alzheimer's Disease scores and Braak and Braak stage), and hippocampal sclerosis. Subjects were pathologically classified as 12 healthy control subjects, 46 AD, 14 CVD, 9 mixed AD/CVD, and 12 cognitively impaired patients without significant AD/CVD pathology. Multivariate models tested associations between magnetic resonance and pathological findings across the entire sample.

RESULTS

Pathological correlates of cortical gray matter volume were AD, subcortical vascular pathology, and arteriosclerosis. Hippocampal volume was related to AD pathology and hippocampal sclerosis, and the effects of hippocampal sclerosis were greater for subjects with low levels of AD pathology. White matter hyperintensities were related to age and to white matter pathology. Number of MRI lacunes was related to subcortical vascular pathology.

INTERPRETATION

In this clinical setting, the presence of lacunes and white matter changes provide a good signal for vascular disease. The neuropathological basis of MR defined cerebral cortical and hippocampal atrophy in aging and dementia is complex, with several pathological processes converging on similar brain structures that mediate cognitive decline.

Effect of cortisol levels on working memory performance in elderly subjects with Alzheimer's disease

BACKGROUND: Subjects with Alzheimer's disease (AD) have elevated cortisol levels as a result of hypothalamic-pituitary-adrenal (HPA) axis dysfunction. Acute administration of hydrocortisone has been associated with working memory (WM) performance in young adults. OBJECTIVE: To investigate whether cortisol levels are associated with WM performance in subjects with AD. METHOD: Eighty subjects were included, comprising 40 patients with mild AD and 40 healthy elderly controls. WM was assessed using the Digit Span Backward test (DSB). Saliva samples were collected to determine cortisol levels. RESULTS: AD subjects had poorer performance on the DSB than controls (p=0.002) and also presented higher levels of cortisol than control group (p=0.04). No significant correlation was observed between the DSB and cortisol levels in both groups (r= -0.29). CONCLUSION: In this study, elevated cortisol levels were not associated with poorer WM performance in patients with AD or in healthy elderly subjects.

Cognitive-behavioral profiles of neurodegenerative dementias: beyond Alzheimer's disease

The neurocognitive and behavioral profiles of vascular dementia and vascular cognitive impairment, dementia with Lewy bodies and Parkinson's disease with dementia, and dementia syndromes associated with frontotemporal lobar degenerations are compared and contrasted with Alzheimer's dementia (AD). Vascular dementia/vascular cognitive impairment is characterized by better verbal memory performance, worse quantitative executive functioning, and prominent depressed mood. Dementia with Lewy bodies and Parkinson's disease with dementia are equally contrasted with AD by defective processing of visual information, better performance on executively supported verbal learning tasks, greater attentional variability, poorer qualitative executive functioning, and the presence of mood-congruent visual hallucinations. The frontal variant of frontotemporal lobar degeneration (frontotemporal dementia) differs from AD by better multimodal retention on learning tasks, different patterns of generative word fluency, defective qualitative executive functioning, and by markedly impairment of comportment. For temporal variants of frontotemporal lobar degenerations, progressive aphasia and semantic dementia, worse language performance relative to AD is typically characteristic.

The contribution of medial temporal lobe atrophy and vascular pathology to cognitive impairment in vascular dementia

BACKGROUND AND PURPOSE

Besides cerebrovascular disease, medial temporal lobe atrophy (MTA), a neuroimaging finding suggestive of degenerative pathology, has been shown in vascular dementia (VaD). However, it is unknown to what extent MTA contributes to the pattern of cognitive impairment observed in VaD. Therefore, our purpose was to investigate the relative contribution of cerebrovascular disease and MTA to cognitive impairment in patients fulfilling diagnostic criteria for VaD.

METHODS

We examined 590 patients (374 men; mean age, 73 years; standard deviation, 8) with probable VaD according to the National Institute of Neurological Disorders and Stroke-Association Internationale pour la Recherche et l'Enseignement en Neurosciences criteria at inclusion into a multicenter clinical trial. Cerebrovascular disease and the degree of MTA were evaluated by using MRI. Cognitive testing included the Mini-Mental State Examination, and the vascular dementia assessment scale.

RESULTS

On the basis of the operational definitions for the neuroimaging part of the National Institute of Neurological Disorders and Stroke-Association Internationale pour la Recherche et l'Enseignement en Neurosciences criteria, 485 (82.2%) patients had small vessel VaD and 153 (25.9%) had large vessel VaD. More than half (59.8%) of the patients had considerable MTA. Multiple linear regression analyses revealed that after correction for sex, age, education, and duration of dementia, neuropsychological tests showed that patients with higher grades of MTA or large vessel VaD had significantly worse general cognitive and executive functioning, whereas associations with small vessel disease were restricted to worse executive functioning.

CONCLUSIONS

Both MTA and large vessel disease contribute to global cognitive impairment in VaD. Small vessel disease contributes to executive dysfunction.

Subcortical ischemic vascular dementia

Subcortical ischemic vascular dementia (SIVD) has been proposed as a subtype of vascular cognitive impairment. MRI often discloses "silent" hyperintensities in 20% to 40% of community-dwelling elderly. Efforts to relate MRI-measured lacunes and white matter changes to cognitive impairment have not been straightforward. The possibility that Alzheimer's disease pathology contributes to cognitive impairment increases with age. A rare disorder known as cerebral autosomal dominant arteriopathy with subcortical infarctions and leukoencephalopathy (CADASIL) provides an opportunity to study SIVD in the absence of Alzheimer's disease. Lacunes and deep white matter changes are associated with dysexecutive syndrome. Hypertension, the leading risk factor for sporadic SIVD, is treatable. High priority must be given to reducing vascular risk profiles.