The influence of coincidental vascular pathology on symptomatology and course of Alzheimer's disease

Steroid hormones: risk and resilience in women's Alzheimer disease

More women have Alzheimer disease (AD) than men, but the reasons for this phenomenon are still unknown. Including women in clinical research and studying their biology is key to understand not just their increased risk but also their resilience against the disease. In this sense, women are more affected by AD than men, but their reserve or resilience mechanisms might delay symptom onset. The aim of this review was to explore what is known about mechanisms underlying women's risk and resilience in AD and identify emerging themes in this area that merit further research. We conducted a review of studies analyzing molecular mechanisms that may induce neuroplasticity in women, as well as cognitive and brain reserve. We also analyzed how the loss of steroid hormones in aging may be linked to AD. We included empirical studies with human and animal models, literature reviews as well as meta-analyses. Our search identified the importance of 17-b-estradiol (E2) as a mechanism driving cognitive and brain reserve in women. More broadly, our analysis revealed the following emerging perspectives: (1) the importance of steroid hormones and their effects on both neurons and glia for the study of risk and resilience in AD, (2) E2's crucial role in women's brain reserve, (3) women's verbal memory advantage as a cognitive reserve factor, and (4) E2's potential role in linguistic experiences such as multilingualism and hearing loss. Future directions for research include analyzing the reserve mechanisms of steroid hormones on neuronal and glial plasticity, as well as identifying the links between steroid hormone loss in aging and risk for AD.

Identification of pivotal markers in vascular dementia based on proteomics data

OBJECTIVE

The aim of this study was to analyze protein expression profiles of vascular dementia (VaD) subjects for investigating the underlying therapeutic markers.

METHODS

Protein expression profile data were acquired from a quantitative clinical proteomic study, including 10 nondemented elderly controls and 10 age-matched VaD subjects. Differentially expressed proteins (DEPs) were identified between VaD subjects and controls, followed by function prediction using DAVID (Database for Annotation, Visualization, and Integrated Discovery). Then, a protein-protein interaction (PPI) network was constructed by comparing it with the STRING (Search Tool for the Retrieval of Interacting Genes) database, and the pathway crosstalk analysis was conducted based on overlapping PPI network and enriched pathways. Furthermore, the subpathway was screened and analyzed by the iSubpathwayMiner package in R.

RESULTS

A total of 144 DEPs were screened from VaD subjects and the controls. They were significantly enriched in many pathways. High-degree proteins were detected in the PPI network, such as ATP5B (ATP synthase subunit β). Furthermore, 'metabolic pathways' and 'Alzheimer's disease' were the significant pathways screened in the crosstalk analysis. At last, upregulated proteins were enriched in 2 subpathways of 1 pathway, while downregulated proteins were enriched in 162 subpathways of 36 pathways.

CONCLUSION

By analyzing the differential expressions of proteins, the potential underlying therapeutic markers and mechanism of VaD might be elucidated.

Hemodynamic effects of cholinesterase inhibition in mild Alzheimer's disease

PURPOSE

To evaluate the spatiotemporal progression of perfusion changes in early stages of Alzheimer's disease (AD), we imaged the perfusion response to pharmacological treatment in a group of mild AD patients and contrasted it to the perfusion of age-, sex-, and education-matched healthy volunteers over the same time interval.

MATERIALS AND METHODS

We used pseudo continuous arterial spin labeling (PCASL) MRI for quantitative three-dimensional mapping of perfusion immediately before and 6 months after cholinesterase inhibitor treatment.

RESULTS

Before treatment, patients were found hypoperfused relative to their healthy counterparts in the gray matter of lateral temporal lobe, posterior cingulate, and anterior cingulate as well as in the white matter of the posterior cingulate. Most of the cortical regions investigated and the white matter of posterior cingulate and prefrontal regions showed treatment-elicited increases in perfusion, which were not secondary to changes in regional tissue volume nor were they associated with improvement in either MMSE or ADAS-Cog scores, although lack of deterioration suggested a cognitive benefit.

CONCLUSION

This study provides a hemodynamic profile of mild AD and sheds light on the perfusion changes related to prolonged cholinesterase inhibition in this early disease stage.

Vascular basis for brain degeneration: faltering controls and risk factors for dementia

The integrity of the vascular system is essential for the efficient functioning of the brain. Aging-related structural and functional disturbances in the macro- or microcirculation of the brain make it vulnerable to cognitive dysfunction, leading to brain degeneration and dementing illness. Several faltering controls, including impairment in autoregulation, neurovascular coupling, blood-brain barrier leakage, decreased cerebrospinal fluid, and reduced vascular tone, appear to be responsible for varying degrees of neurodegeneration in old age. There is ample evidence to indicate vascular risk factors are also linked to neurodegenerative processes preceding cognitive decline and dementia. The strongest risk factor for brain degeneration, whether it results from vascular or neurodegenerative mechanisms or both, is age. However, several modifiable risks such as cardiovascular disease, hypertension, dyslipidemia, diabetes, and obesity enhance the rate of cognitive decline and increase the risk of Alzheimer's disease in particular. The ultimate accumulation of brain pathological lesions may be modified by genetic influences, such as the apolipoprotein E ε4 allele and the environment. Lifestyle measures that maintain or improve cardiovascular health, including consumption of healthy diets, moderate use of alcohol, and implementation of regular physical exercise are important factors for brain protection.

Galantamine treatment in Alzheimer's disease with cerebrovascular disease: responder analyses from a randomized, controlled trial (GAL-INT-6)

Alzheimer's disease combined with cerebrovascular disease (AD with CVD) is associated with progressive decline, with CVD impacting AD onset and severity of progression. Subjects with confirmed diagnosis of AD with CVD were treated with galantamine during a six-month, randomized, placebo-controlled trial (N = 285). Responder analyses were performed for cognitive, behavioural and functional outcome measures. Galantamine treatment resulted in significantly greater cognitive and functional improvements compared with placebo at six months, and a significantly higher percentage of treatment responders. The proportion of responders demonstrating improved or maintained cognition on the 11-item AD assessment scale-cognitive subscale (ADAS-cog/11) was 60.5% for galantamine versus 46.0% for placebo (P = 0.013). The proportion of patients responding by at least four-points on the ADAS-cog/11 was significantly greater for the galantamine group compared with placebo (33.6% versus 17.2%; P = 0.003). Seventy-five percent of galantamine-treated subjects improved or remained stable as assessed by CIBIC-plus compared with 53.6% on placebo (P = 0.0006). Significantly higher responder rates were observed with galantamine for behaviour (64.9% versus 56.6%; P = 0.024), and numerically favourable responder rates were seen with galantamine for activities of daily living. Treatment-emergent adverse events were generally related with the gastrointestinal system (nausea 20% versus 10%; vomiting 12% versus 5%; galantamine and placebo groups, respectively). Three deaths occurred during double-blind treatment: 2 of 188 subjects receiving galantamine, and 1 of 97 subjects receiving placebo. These findings are consistent with a broad range of cognitive, functional and behavioural benefits with galantamine across the spectrum of AD and AD with CVD.

Rethinking the dementia diagnoses in a population-based study: what is Alzheimer's disease and what is vascular dementia? A study from the kungsholmen project

OBJECTIVE

To explore the hypothesis that older adults often are affected by more than one disease, making the differential diagnosis between Alzheimer's disease (AD) and vascular dementia (VaD) difficult.

METHODS

Incident dementia cases (n = 308) from a population-based longitudinal study of people 75+ years were investigated. The DSM-III-R criteria were used for the clinical diagnosis of dementia. Data on vascular disorders (hypertension, cerebrovascular and ischemic heart diseases, heart failure, atrial fibrillation, diabetes) as well as type of onset/course of dementia were used retrospectively to reclassify dementias.

RESULTS

Only 47% of the AD cases were reclassified as pure AD without any vascular disorder. Among subjects with AD and with a vascular component, cerebrovascular disease was the most common (41%). Only 25% of VaD were reclassified as pure VaD. Further, 26% of the pure AD subjects developed a vascular disorder in the following 3 years.

CONCLUSIONS

Both vascular and degenerative mechanisms may often contribute to the expression of dementia among the elderly. Most of the AD cases have vascular involvements, and pure dementia types in very old subjects constitute only a minority of dementia cases.

Cholesterol as a risk factor for Alzheimer's disease - epidemiological evidence

Although dementia is usually a late-life syndrome, it is now well known that pathological changes begin quite early in adulthood, outside the classical age borders of geriatric specialties. In order to design effective preventive strategies, adequate information can only be gathered by taking a life-long view of Alzheimer's disease (AD). Dementia risk is the result of exposure to both harmful and protective factors along the life course, and these factors, as well as their impact on the individual's health status, change over time. This review aims at presenting current epidemiological data on serum cholesterol levels and dietary fat intake as risk factors for dementia/AD, and at discussing the reasons and significance of contradictions between various studies. Reducing dementia risk may be possible by influencing the serum lipid profile. A more detailed characterization of the mechanisms behind the association of cholesterol (in both serum and brain) with dementia/AD, mechanisms about which little is currently known, would allow a better translation of research findings into clinical practice.

Protective Effects of Breviscapine on Ischemic Vascular Dementia in Rats

Breviscapine, a traditional Chinese medicine, is extensively used in clinic to treat cardiovascular diseases and cerebrovascular injury. In this study, we demonstrated the effects of breviscapine on vascular dementia (VD) rats, which were mimicked by permanent occlusion of bilateral common carotid arteries. Breviscapine (2 mg/kg for 14 d) improved the performance of learning and memory of VD rats in Morris water maze, decreased the level of lipid peroxidation and free radicals, and attenuated the pathological alterations, such as nuclear shrink, cellular edema and irregular arrangement of pyramidal layer in the hippocampal CA(1) area. In vitro experiment, breviscapine (50 microg/l) protected cortical neuron from injury and decreased intracellular calcium overloading induced by H2O2 (10 mM). The results suggest that breviscapine has therapeutic effect on cerebral ischemia and vascular dementia.

Interactions between Alzheimer's disease and cerebral ischemia--focus on inflammation

Progressive memory impairment, beta-amyloid (Abeta) plaques associated with local inflammation, neurofibrillary tangles, and loss of neurons in selective brain areas are hallmarks of Alzheimer's disease (AD). Although beta-amyloid precursor protein (APP) and Abeta have a central role in the etiology of AD, it is not clear which forms of APP or Abeta are responsible for the neuronal vulnerability in AD brain. Brain ischemia, another cause of dementia in the elderly, has recently been recognized to contribute to the pathogenesis of AD and individuals with severe cognitive decline and possibly underlying AD are at increased risk for ischemic events in the brain. Moreover, the epsilon4 allele of apolipoprotein E (ApoE) is a risk factor for both AD and poor outcome following brain ischemia and hemorrhage. Several factors and molecular mechanisms that lower the threshold of neuronal death in models of AD have recently been described. Among these neuroinflammation seems to play an important role. The development and maturation of both AD neuropathology and ischemic lesions in the central nervous system are characterized by activation of glial cells and upregulation of inflammatory mediators. Indeed, anti-inflammatory approaches have proven to be beneficial in the prevention and treatment of AD-like neuropathology and ischemic injuries in vivo. This review summarizes some of the findings suggesting that neuronal overexpression of human APP renders the brain more vulnerable to ischemic injury and describes the factors that are involved in increased neuronal susceptibility to ischemic stroke.

Effect of vascular lesions on cognition in Alzheimer's disease: a community-based study

OBJECTIVES

To investigate whether clinical and neuropathological differences exist between Alzheimer's disease (AD) cases with and without vascular lesions neuropathologically diagnosed using Consortium to Establish a Registry for Alzheimer's Disease (CERAD) criteria.

DESIGN

Descriptive observational study.

SETTING

A community-based registry that identified incident dementia cases.

PARTICIPANTS

Of the 124 subjects with available clinical and neuropathological assessments, 30 had AD lesions alone, and 18 had AD with vascular lesions. Patients with other neuropathological findings were excluded.

MEASUREMENTS

Dependent measures included demographic, clinical, and neuropathological characteristics. Neuropathological diagnoses were made using the CERAD criteria and Braak and Braak staging.

RESULTS

Of the 124 autopsied cases, 85 cases were diagnosed with neuropathological AD. Of these, 30 had pathology consistent with "pure" AD, whereas 18 had AD pathology with significant vascular lesions (AD/V). There were no differences in age, sex, or education between groups. AD/V cases had higher baseline and final Mini-Mental State Examination (MMSE) scores than pure AD cases, but after adjusting for education, differences in MMSE scores were not statistically significant. The AD/V group had significantly lower Braak staging than the pure AD group, after adjusting for education and final MMSE scores.

CONCLUSION

In this comparison study of AD cases with and without vascular lesions, AD/V cases had less severe AD pathology than those with AD alone, indicating that cerebrovascular disease likely contributes to the severity of cognitive impairment in those with AD. Controlling for vascular risk factors in patients with AD may have a significant effect on severity of dementia.

Cholinesterase inhibitors and vascular dementia: another string to their bow?

Two of the four licensed cholinesterase inhibitors, galantamine and donepezil, have recently featured in published work showing how they act in dementia associated with cerebrovascular disease (CVD). It is timely to review this new evidence and place it within the current consensus understanding of what makes up a clearly heterogeneous dementia population. To do this, the current review explores the relationship between Alzheimer's disease, for which this group of compounds originally received licensing approval, and vascular pathology within the brain, highlighting the significant overlap in risk factors and the frequent coexistence of the two conditions in the patients that are studied. Whether they are inter-related or separate entities is discussed, followed by a description of the current classifications of Alzheimer's disease with CVD, and the three subtypes of 'pure' vascular dementia - subcortical, cortical and strategic infarct. Understanding these entities allows more accurate diagnostic and prognostic information to be given to patients, and leads towards matching the published clinical evidence discussed with more predictable clinical syndromes. This distinction is particularly relevant in terms of the studies conducted thus far. Galantamine has been studied in a placebo-controlled study of patients with Alzheimer's disease and CVD as well as patients with vascular dementia, whereas donepezil was studied exclusively in patients with vascular dementia. Differences in the way the placebo groups acted in these studies confirmed the fact that these actually are two distinct groups. Galantamine showed efficacy across the combined groups studied, with placebo deterioration similar to previous Alzheimer's disease studies, while donepezil produced a positive effect in vascular dementia - with this placebo group relatively unchanged. The symptomatic improvements seen were not really surprising, as cholinergic deficits are a common factor across all of these syndromes. Wherever this is the predominant biological finding, it would be expected that cholinesterase inhibitors would have a similar effect, whatever the condition causing it.

Galantamine in the treatment of cognitive decline in patients with vascular dementia or Alzheimer's disease with cerebrovascular disease

INTRODUCTION

Alzheimer's disease and vascular dementia are the two most common types of dementia, with significant overlap of clinical symptoms and pathology. Previous results from a 6-month, double-blind, placebo-controlled, international, multicentre study of the cholinomimetic galantamine in patients with probable vascular dementia or mixed dementia (Alzheimer's disease with cerebrovascular disease) showed significant cognitive, behavioural and functional benefits in these patients. Furthermore, results of a 6-month, open-label extension of this study confirmed that patients with vascular dementia or Alzheimer's disease with cerebrovascular disease may benefit from galantamine therapy for at least 1 year. The objective of the current analysis was to determine if the long-term cognitive benefits of galantamine seen in the above-mentioned study are influenced by dementia type (probable vascular dementia vs Alzheimer's disease with cerebrovascular disease).

STUDY DESIGN

A post hoc sub-analysis of a 6-month, multicentre, randomised, double-blind, placebo-controlled study and a subsequent 6-month, open-label extension.

PATIENTS AND METHODS

Patients diagnosed with probable vascular dementia or Alzheimer's disease with cerebrovascular disease were treated with galantamine (Reminyl) 24 mg/day for 12 months (6 months double-blind and 6 months open-label) or placebo for 6 months (double-blind) followed by galantamine 24 mg/day for 6 months (open-label). Changes in scores on the 11-item Alzheimer's Disease Assessment Scale cognitive subscale (ADAS-cog/11) were assessed at months 6, 7.5 and 12. Mean changes from baseline were analysed.

RESULTS

Patients with probable vascular dementia treated with galantamine for 6 or 12 months showed significant improvements in ADAS-cog/11 scores versus baseline, which were maintained at the end of the 12-month study. Patients who had Alzheimer's disease with cerebrovascular disease continuously treated with galantamine maintained the cognitive abilities seen at baseline for at least 12 months. Additionally, patients who had Alzheimer's disease with cerebrovascular disease who were switched from placebo to open-label galantamine therapy for 6 months demonstrated cognitive benefits, but these benefits were significantly less than those observed in patients treated with galantamine continuously for the 12-month period. Galantamine was well tolerated throughout the entire 12-month study.

CONCLUSIONS

These findings suggest that the drug is efficacious for such common forms of dementia as vascular dementia and Alzheimer's disease with cerebrovascular disease. Moreover, some patients benefit from galantamine therapy that is initiated early, soon after diagnosis, and continued for at least 1 year.

The role of neuroimaging in the diagnosis of vascular dementia

Vascular dementia (VaD) and Alzheimer's disease share many pathological and clinical characteristics. Whereas clinical criteria can help differentiate VaD from other types of dementia, neuroimaging is required for confirmation of vascular lesions. Neuroimaging also provides information about location and size of vascular lesions that can lead to a better understanding of symptoms and may help guide therapy.

Vascular factors in Alzheimer's disease

Vascular involvement in Alzheimer disease (AD) is not necessarily coincident. Current evidence suggests the neuropathology of Alzheimer type of dementia comprises more than amyloid plaques and neurofibrillary tangles. At least a third of recognized AD cases may exhibit cerebrovascular pathology, which also constitutes distinct small vessel disease. Cerebral amyloid angiopathy, microvascular degeneration affecting the cerebral endothelium and smooth muscle cells, basal lamina alterations, hyalinosis, and fibrosis are frequently evident in AD. These changes may be accompanied by perivascular denervation that is causal in the cognitive decline of AD. In addition, amyloid beta protein appears directly involved in the degeneration of both the larger perforating arterial vessels as well as cerebral capillaries, which represent the blood-brain barrier. The cerebrovascular pathology in AD also encompasses macro- and micro-infarctions, hemorrhages, lacunas, and ischemic white-matter changes. An interaction of both perivascular mediators and derived factors would perturb the brain vasculature. Peripheral vascular factors such as long-standing hypertension, atrial fibrillation, coronary or carotid artery disease, and diabetes mellitus are also apparent in AD. These factors would modify the cerebral circulation such that a sustained hypoperfusion or oligemia is impacted upon the aging processes to induce the characteristic pathology.

Similarities between Alzheimer's disease and vascular dementia

Alzheimer's disease (AD) and vascular dementia (VaD) are the two most common forms of dementia. In Europe, 800,000 people have a diagnosis of VaD out of 3.7 million people with clinical dementia. These two dementia types share many common pathological, symptomatic and neurochemical features, and cholinergic treatments that have demonstrated robust, broad-ranging and long-term efficacy in AD are now being assessed for the treatment of dementia related to cerebrovascular disease (CVD). There has been recent recognition that dementia in the elderly is a continuum of pathologies, with pure AD and VaD representing the two extremes, and 'mixed' dementia (AD with CVD) in between and perhaps comprising the majority of cases. 'Mixed' dementia is rarely diagnosed in the clinic, however, as the majority of diagnostic procedures are biased toward a diagnosis of AD. Here, the risk factors, pathophysiological mechanisms and clinical symptoms of AD and VaD are described, identifying their overlap as well as some of the differences in both cognitive and noncognitive symptoms. Important findings indicating the high prevalence of 'mixed' dementia in the clinical dementia population are also discussed. In particular, evidence of a causal connection between stroke or CVD and AD is addressed. Regarding effective therapeutic management of dementia patients, further concerted epidemiological study of these related dementia types should aid in clinical decisions on the applicability of cholinergic treatments.

Hypertension and hypercholesterolaemia as risk factors for Alzheimer's disease: potential for pharmacological intervention

This paper focuses on hypertension and hypercholesterolaemia as risk factors for Alzheimer's disease and, as such, subjects for prevention. The long-term, prospective, population-based studies regarding the relationship between hypertension or hypercholesterolaemia and Alzheimer's disease, and the clinical studies regarding the association between antihypertensive or lipid-lowering medications and the risk of Alzheimer's disease, are reviewed. These studies provide evidence to suggest that elevated blood pressure and cholesterol levels earlier in life may have an important role in the development and expression of late-life Alzheimer's disease. Based on these data, we propose that proper, early interventions aimed at reducing these cardiovascular risk factors may have an impact on the future incidence and prevalence of Alzheimer's disease.

Huperzine A attenuates cognitive deficits and hippocampal neuronal damage after transient global ischemia in gerbils

The protective effects of huperzine A on transient global ischemia in gerbils were investigated. Five min of global ischemia in gerbils results in working memory impairments shown by increased escape latency in a water maze and reduced time spent in the target quadrant. These signs of dysfunction are accompanied by delayed degeneration of pyramidal hippocampal CA1 neurons and by decrease in acetylcholinesterase activity in the hippocampus. Subchronic oral administration of huperzine A (0.1 mg/kg, twice per day for 14 days) after ischemia significantly reduced the memory impairment, reduced neuronal degeneration in the CA1 region, and partially restored hippocampal choline acetyltransferase activity. The ability of huperzine A to attenuate memory deficits and neuronal damage after ischemia might be beneficial in cerebrovascular type dementia.

Structural neuroimaging of Alzheimer's disease and other dementias

This paper reviews the use of imaging techniques to aid in the clinical diagnosis of dementia. Two approaches are distinguished. One is the exclusionary approach in which imaging is used to rule out diseases that would mimic or cause dementia; based on the literature, this approach yields very little, if any, information that was not identified clinically. The more positive approach uses imaging as a diagnostic tool to identify changes specific for causes of dementia; any assessment of medial temporal lobe atrophy on Magnetic Resonance Imaging (MRI) will result in a reasonably high positive likelihood ratio distinguishing AD patients from non-demented individuals, but fails to distinguish AD patients from patients with other dementias. For a diagnosis of vascular dementia imaging is necessary, although not all vascular changes fulfill requirements of being relevant to dementia. Potentially of more importance, given the higher prevalence of AD, is the identification of concomitant vascular changes in AD that may be amenable to therapy, and may be used to identify subgroups. Structural and functional MRI techniques have great potential in identifying patients at risk for AD, which will allow for a very early treatment with drugs that slow or even halt progression.

Huperzine A improves cognitive deficits caused by chronic cerebral hypoperfusion in rats

The effects of (-)-huperzine A, a promising therapeutic agent for Alzheimer's disease, on learning behavior and on alterations of the cholinergic system, the oxygen free radicals and energy metabolites induced by permanent bilateral ligation of the common carotid arteries were investigated in rats. Daily oral administration of huperzine A produced a significant improvement of the deficit in the learning of the water maze task, beginning 28 days after ischemia, correlating to about 33-40% inhibition of acetylcholinesterase activity in cortex and hippocampus. Huperzine A significantly restored the decrease in choline acetyltransferase activity in hippocampus and significantly reduced the increases in superoxide dismutase, lipid peroxide, lactate and glucose to their normal levels. The present findings demonstrate that the improvement by huperzine A of the cognitive dysfunction in the late phase in chronically hypoperfused rats is due to its effects, not only on the cholinergic system, but also on the oxygen free radical system and energy metabolism. Our results strongly suggest that huperzine A has therapeutic potential for the treatment of dementia caused by cholinergic dysfunction and/or decrease of cerebral blood flow.

The blood-brain barrier and cerebrovascular pathology in Alzheimer's disease

The pathology of Alzheimer's disease (AD) is not limited to amyloid plaques and neurofibrillary tangles. Recent evidence suggests that more than 30% of AD cases exhibit cerebrovascular pathology, which involves the cellular elements that represent the blood-brain barrier. Certain vascular lesions such as microvascular degeneration affecting the cerebral endothelium, cerebral amyloid angiopathy and periventricular white matter lesions are evident in virtually all cases of AD. Furthermore, clinical studies have demonstrated blood-brain barrier dysfunction in AD patients who exhibit peripheral vascular abnormalities such as hypertension, cardiovascular disease and diabetes. Whether these vascular lesions along with perivascular denervation are coincidental or causal in the pathogenetic processes of AD remains to be defined. In this chapter, I review biochemical and morphological evidence in context with the variable but distinct cerebrovascular pathology described in AD. I also consider genetic influences such as apolipoprotein E in relation to cerebrovascular lesions that may shed light on the pathophysiology of the cerebral vasculature. The compelling vascular pathology associated with AD suggests that transient and focal breach of the blood-brain barrier occurs in late onset AD and may involve an interaction of several factors, which include perivascular mediators as well as peripheral circulation derived factors that perturb the endothelium. These vascular abnormalities are likely to worsen cognitive disability in AD.

The role of cerebral ischemia in Alzheimer's disease

The Alzheimer type of dementia and stroke are known to increase at comparable rates with age. Recent advances suggest that vascular risk factors linked to cerebrovascular disease and stroke in the elderly significantly increase the risk of developing Alzheimer's disease (AD). These include atherosclerosis, atrial fibrillation, coronary artery disease, hypertension, and diabetes mellitus. Moreover, review of various autopsy series shows that 60-90% of AD cases exhibit variable cerebrovascular pathology. Although some vascular lesions such as cerebral amyloid angiopathy, endothelial degeneration, and periventricular white matter lesions are evident in most cases of AD, a third will exhibit cerebral infarction. Despite the interpretation of pathological evidence, longitudinal clinical studies suggest that the co-existence of stroke and AD occurs more than by chance alone. Strokes known to occur in patients with Alzheimer syndrome and most frequently in the oldest old substantially worsen cognitive decline and outcome, implicating some interaction between the disorders. Nevertheless, the nature of a true relationship between the two disorders seems little explored. What predisposes to strokes in underlying cognitive decline or AD? Is it possible that cerebral ischemia is a causal factor for AD? I examined several vascular factors and the vascular pathophysiology implicated in stroke and AD, and propose that cerebral ischemia or oligemia may promote Alzheimer type of changes in the aging brain. Irrespective of the ultimate pathogenetic mechanism, these approaches implicate that management of peripheral vascular disease is important in the treatment or prevention of Alzheimer's disease or mixed dementia.

The analysis system COGITAT for the study of cognitive deficiencies in rodents

COGITAT is an automated hole board system that, following minimal experimental interventions, makes it possible to measure a variety of parameters associated with learning, memory, relearning, cognition, and cognitive shifts, but also changes in exploratory and sensorimotor performance in rodent models. The individual parameters--that is, overall exploratory activity, number of visits (deep in the hole) into or inspections of (at the upper surface) holes, number of baited, unbaited, or previously baited holes visited or inspected, reinspections of or revisits into any holes, number of pellets eaten, time to find pellets, serial order collection (without intermediate inspections or visits), and reference and working memory errors (visits, inspections, or total)--are obtained simultaneously, and the results are immediately available after the end of each experiment. The system appears to be well suited to neurophysiological, neuropharmacological, and gene-technological investigations in rodent models.

Diagnostic impact of cerebral transit time in the identification of microangiopathy in dementia: A transcranial ultrasound study

BACKGROUND AND PURPOSE

The diagnosis and quantification of microangiopathy in dementia is difficult. The assessment of small-vessel disease requires expensive and sophisticated nuclear medicine techniques. This study was performed to identify microangiopathy related to the integrity of cerebral microcirculation by sonographic measurements (arteriovenous cerebral transit time [cTT]).

METHODS

We performed transcranial color-coded duplex sonography in 40 patients with vascular dementia, 20 patients with Alzheimer's disease or Lewy body disease, and 25 age-matched controls. The clinical diagnosis was established by history of dementia and neuroimaging findings. Cognitive impairment was assessed by the Mini-Mental State Examination and Alzheimer's Disease Assessment Scale. cTT is defined as the time required by an ultrasound contrast agent to pass from a cerebral artery to a vein. This was measured by recording the power-Doppler intensity curves in the P2 segment of the posterior cerebral artery and the vein of Galen. Previous studies have shown a prolongation of cTT in patients with cerebral microangiopathy.

RESULTS

cTT was substantially prolonged in patients with vascular dementia (5.8 seconds; 25th percentile 4.5; 75th percentile 7.5; U test, P<0.001) compared with controls (3.1 seconds; 2.3; 3.4) but not in patients with degenerative dementia (3.7 seconds; 3.7; 4.2). In patients with vascular dementia, cTT was significantly correlated with cognitive impairment.

CONCLUSIONS

cTT may be useful tool to disclose small-vessel disease in demented patients. Examination is noninvasive and quickly performed. It may be also useful in follow-up examinations in patients undergoing therapy.