Vascular dementia. A clinicopathological study

Complement C3a Receptor (C3aR) Mediates Vascular Dysfunction, Hippocampal Pathology, and Cognitive Impairment in a Mouse Model of VCID

Vascular contributions to cognitive impairment and dementia (VCID) secondary to chronic mild-moderate cerebral ischemia underlie a significant percentage of cases of dementia. We previously reported that either genetic deficiency of the complement C3a receptor (C3aR) or its pharmacological inhibition protects against cerebral ischemia in rodents, while others have implicated C3aR in the pathogenesis seen in rodent transgenic models of Alzheimer's disease. In the present study, we evaluated the role of complement C3a-C3aR signaling in the onset and progression of VCID. We utilized the bilateral common carotid artery stenosis (BCAS) model to induce VCID in male C57BL/6 wild-type and C3aR-knockout (C3aR-/-) mice. Cerebral blood flow (CBF) changes, hippocampal atrophy (HA), white matter degeneration (WMD), and ventricular size were assessed at 4 months post-BCAS using laser speckle contrast analysis (LSCI) and magnetic resonance imaging (MRI). Cognitive function was evaluated using the Morris water maze (MWM), and novel object recognition (NOR), immunostaining, and western blot were performed to assess the effect of genetic C3aR deletion on post-VCID outcomes. BCAS resulted in decreased CBF and increased HA, WMD, and neurovascular inflammation in WT (C57BL/6) compared to C3aR-/- (C3aR-KO) mice. Moreover, C3aR-/- mice exhibited improved cognitive function on NOR and MWM relative to WT controls. We conclude that over-activation of the C3a/C3aR axis exacerbates neurovascular inflammation leading to poor VCID outcomes which are mitigated by C3aR deletion. Future studies are warranted to dissect the role of cell-specific C3aR in VCID.

Alzheimer's Disease Neuropathological Comorbidities are Common in the Younger-Old

BACKGROUND

Clinicopathological studies have demonstrated that Alzheimer's disease dementia (ADD) is often accompanied by clinically undetectable comorbid neurodegenerative and cerebrovascular disease that alter the rate of cognitive decline. Aside from causing increased variability in clinical response, it is possible that the major ADD comorbidities may not respond to ADD-specific molecular therapeutics.

OBJECTIVE

As most reports have focused on comorbidity in the oldest-old, its extent in younger age groups that are more likely to be involved in clinical trials is largely unknown; our objective is to provide this information.

METHODS

We conducted a survey of neuropathological comorbidities in sporadic ADD using data from the US National Alzheimer's Coordinating Center. Subject data was restricted to those with dementia and meeting National Institute on Aging-Alzheimer's Association intermediate or high AD Neuropathological Change levels, excluding those with known autosomal dominant AD-related mutations.

RESULTS

Highly prevalent ADD comorbidities are not restricted to the oldest-old but are common even in early-onset ADD. The percentage of cases with ADD as the sole major neuropathological diagnosis is highest in the under-60 group, where "pure" ADD cases are still in the minority at 44%. After this AD as a sole major pathology in ADD declines to roughly 20%in the 70s and beyond. Lewy body disease is the most common comorbidity at younger ages but actually is less common at later ages, while for most others, their prevalence increases with age.

CONCLUSION

Alzheimer's disease neuropathological comorbidities are highly prevalent even in the younger-old.

The Neuropathological Diagnosis of Alzheimer's Disease-The Challenges of Pathological Mimics and Concomitant Pathology

The definitive diagnosis of Alzheimer's disease (AD) rests with post-mortem neuropathology despite the advent of more sensitive scanning and the search for reliable biomarkers. Even though the classic neuropathological features of AD have been known for many years, it was only relatively recently that more sensitive immunohistochemistry for amyloid beta (Aβ) and hyperphosphorylated tau (HP-tau) replaced silver-staining techniques. However, immunohistochemistry against these and other proteins has not only allowed a more scientific evaluation of the pathology of AD but also revealed some mimics of HP-tau pathological patterns of AD, including age-related changes, argyrophilic grain disease and chronic traumatic encephalopathy. It also highlighted a number of cases of AD with significant additional pathology including Lewy bodies, phosphorylated TDP-43 (p-TDP-43) positive neuronal cytoplasmic inclusions and vascular pathology. This concomitant pathology can cause a number of challenges including the evaluation of the significance of each pathological entity in the make-up of the clinical symptoms, and the threshold of each individual pathology to cause dementia. It also raises the possibility of underlying common aetiologies. Furthermore, the concomitant pathologies could provide explanations as to the relative failure of clinical trials of anti-Aβ therapy in AD patients.

Vascular cognitive impairment: A preventable component of dementia

For many decades during the 20th century, the common belief was that the slow strangulation of the brains' blood supply from hardening of the brain arteries led to chronic brain ischemia and neuronal death. Not surprisingly, to counter this, vasodilators rapidly became one of the most commonly used and profitable medications worldwide; however, no clinical benefits were ever proven. In the 1970s and early 1980s cerebral blood flow studies strongly disproved the idea of brain failure due to chronic ischemia. It was also shown that infarcts and not chronic ischemia caused dementia, leading to the concept of multiinfarct dementia. In addition to infarcts, it was then realized that other vascular lesions can also cause cognitive decline. Gradually, as "atherosclerotic dementia" lost ground, Alzheimer's disease (AD) that once had been considered a presenile dementia and rare, became almost synonymous with dementia. Subsequent memory-based definitions and evaluations of dementia led to a bias in favor of diagnosing AD, overshadowing vascular contributions. The widespread use of brain imaging in the 1980s and 1990s contributed to the resurgence of evidence of cerebrovascular diseases. Moreover, it was shown that most cognitive impairment of the elderly results from mixed pathologies, emphasizing the need for a change in the traditional categorical diagnosis of dementia, e.g., AD vs vascular dementia. The alternative diagnostic method was named the vascular cognitive impairment approach, meaning identifying any impairment caused by or associated with vascular factors. The importance of this approach is that vascular lesions are currently the most important treatable and preventable components of dementia, even before any symptoms manifest, i.e., at the brain at risk stage. This chapter provides a summary of the vascular cognitive impairment approach to diagnosis, treatment, and prevention of cognitive decline.

Association of cortical microinfarcts and cerebral small vessel pathology in the ageing brain

AIMS

Cortical microinfarcts (CMI) are frequently observed in the ageing brain independent of cognitive decline, but their aetiology is not fully elucidated. To examine the potential role of different vessel pathologies, including cerebral amyloid angiopathy (CAA), arteriolosclerosis-hyalinosis and thromboembolism in the development of CMI, we examined 80 autopsy cases with more than one CMI on routine neuropathological examination.

METHODS

Pial and intracortical vessels around CMI were assessed for their integrity with haematoxylin-eosin staining and antibodies against amyloid-β protein and fibrinogen using a semiquantitative four-level rating scale (absent to severe) in the hippocampus, and the frontal, temporal and occipital cortex. Four histological categories of changes were defined: CAA, vessel pathology other than CAA, thromboembolism and absence of vessel pathology near CMI.

RESULTS

A differential distribution of microvascular pathology was observed depending on brain regions. In the occipital cortex, CAA was commonly associated with CMI. In contrast, in the hippocampus and the frontal cortex, cases without any vascular pathology in pial and intracortical vessels were significantly more frequent.

CONCLUSIONS

The aetiology of CMI differs depending on brain location. CAA may play a role principally in the occipital cortex. The large number of intact vessels around the CMI (mainly in the frontal cortex and hippocampus) raises the possibility that pathologies other than structural microangiopathy, including hypoperfusion/arterial hypotension or large vessel atherosclerosis, play a role in the development of microvascular lesions. These results are relevant in the context of aetiopathogenesis of vascular changes associated with conditions like vascular dementia.

The impact of cerebrovascular aging on vascular cognitive impairment and dementia

As human life expectancy rises, the aged population will increase. Aging is accompanied by changes in tissue structure, often resulting in functional decline. For example, aging within blood vessels contributes to a decrease in blood flow to important organs, potentially leading to organ atrophy and loss of function. In the central nervous system, cerebral vascular aging can lead to loss of the integrity of the blood-brain barrier, eventually resulting in cognitive and sensorimotor decline. One of the major of types of cognitive dysfunction due to chronic cerebral hypoperfusion is vascular cognitive impairment and dementia (VCID). In spite of recent progress in clinical and experimental VCID research, our understanding of vascular contributions to the pathogenesis of VCID is still very limited. In this review, we summarize recent findings on VCID, with a focus on vascular age-related pathologies and their contribution to the development of this condition.

Neuropathological diagnosis of vascular cognitive impairment and vascular dementia with implications for Alzheimer's disease

Vascular dementia (VaD) is recognised as a neurocognitive disorder, which is explained by numerous vascular causes in the general absence of other pathologies. The heterogeneity of cerebrovascular disease makes it challenging to elucidate the neuropathological substrates and mechanisms of VaD as well as vascular cognitive impairment (VCI). Consensus and accurate diagnosis of VaD relies on wide-ranging clinical, neuropsychometric and neuroimaging measures with subsequent pathological confirmation. Pathological diagnosis of suspected clinical VaD requires adequate postmortem brain sampling and rigorous assessment methods to identify important substrates. Factors that define the subtypes of VaD include the nature and extent of vascular pathologies, degree of involvement of extra and intracranial vessels and the anatomical location of tissue changes. Atherosclerotic and cardioembolic diseases appear the most common substrates of vascular brain injury or infarction. Small vessel disease characterised by arteriolosclerosis and lacunar infarcts also causes cortical and subcortical microinfarcts, which appear to be the most robust substrates of cognitive impairment. Diffuse WM changes with loss of myelin and axonal abnormalities are common to almost all subtypes of VaD. Medial temporal lobe and hippocampal atrophy accompanied by variable hippocampal sclerosis are also features of VaD as they are of Alzheimer’s disease. Recent observations suggest that there is a vascular basis for neuronal atrophy in both the temporal and frontal lobes in VaD that is entirely independent of any Alzheimer pathology. Further knowledge on specific neuronal and dendro-synaptic changes in key regions resulting in executive dysfunction and other cognitive deficits, which define VCI and VaD, needs to be gathered. Hereditary arteriopathies such as cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy or CADASIL have provided insights into the mechanisms of dementia associated with cerebral small vessel disease. Greater understanding of the neurochemical and molecular investigations is needed to better define microvascular disease and vascular substrates of dementia. The investigation of relevant animal models would be valuable in exploring the pathogenesis as well as prevention of the vascular causes of cognitive impairment.

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.

Cerebral microinfarcts: the invisible lesions

The association between small but still visible lacunar infarcts and cognitive decline has been established by population-based radiological and pathological studies. Microscopic examination of brain sections shows even smaller but substantially more numerous microinfarcts, the focus of this Review. These lesions often result from small vessel pathologies such as arteriolosclerosis or cerebral amyloid angiopathy. They typically go undetected in clinical-radiological correlation studies that rely on conventional structural MRI, although the largest acute microinfarcts can be detected by diffusion-weighted imaging. In view of their high numbers and widespread distribution, microinfarcts could directly disrupt important cognitive networks and thus account for some of the neurological dysfunction associated with lesions visible on conventional MRI such as lacunar infarcts and white matter hyperintensities. Standardised neuropathological assessment criteria and the development of non-invasive means of detection during life would be major steps towards understanding the causes and consequences of otherwise macroscopically invisible microinfarcts.

Staging and natural history of cerebrovascular pathology in dementia

OBJECTIVE

Most pathologic studies indicate that significant vascular changes are found in the majority of elderly persons, either alone or in association with neurodegenerative processes such as Alzheimer disease (AD) or dementia with Lewy bodies (DLB). Cumulative burden of cerebrovascular lesions can explain cognitive decline described as vascular cognitive impairment, but because there is a lack of consensus in the best way to quantify vascular pathology, the relationship between cognitive decline and cerebrovascular disease remains uncertain. We developed a rating scheme for cerebrovascular lesions using postmortem brains from patients with dementia from 2 European tertiary care memory clinics.

METHODS

A total of 135 brains with a neuropathologic diagnosis of vascular dementia (VaD) (n = 26), AD + VaD (n = 39), DLB + VaD (n = 21), AD + DLB + VaD (n = 9), AD (n = 19), and DLB (n = 21) were investigated in this study. Cerebrovascular lesions were rated on large sections from the hippocampus, the temporal lobe, the frontal lobe, and basal ganglia.

RESULTS

In patients with dementia, vessel wall modifications such as arteriolosclerosis or amyloid angiopathy are the most common and presumably the earliest changes. Modifications in perivascular spaces and myelin loss are the next most common. Lacunar or regional infarcts may occur as a consequence of an independent process or in the final phase of small vessel diseases.

CONCLUSION

A staging system based on this conceptual model of cerebrovascular pathology could enable the neuropathologic quantification of the cerebrovascular burden in dementia. Further studies are needed to determine whether this system can be used in large-scale studies to understand clinical-cerebrovascular pathologic correlations.

Prevention of dementia

Dementia is a neurological condition that is characterized by decline in multiple cognitive domains and is accompanied by a functional impairment. It is important to identify the factors that may delay the onset, slow the progression, or prevent cognitive decline. This review highlights the protective and risk factors of dementia, suggesting that physical activity, intellectual activity, and social engagement may reduce Alzheimer disease and cognitive decline and may be also helpful for enhancing quality of life.

Role of vascular risk factors and vascular dysfunction in Alzheimer's disease

Recent findings indicate that vascular risk factors and neurovascular dysfunction play integral roles in the pathogenesis of Alzheimer's disease. In addition to aging, the most common risk factors for Alzheimer's disease are apolipoprotein e4 allele, hypertension, hypotension, diabetes, and hypercholesterolemia. All of these can be characterized by vascular pathology attributed to conditions such as cerebral amyloid angiopathy and subsequent blood-brain barrier dysfunction. Many epidemiological, clinical, and pharmacotherapeutic studies have assessed the associations between such risk factors and Alzheimer's disease and have found positive associations between hypertension, hypotension, and diabetes mellitus. However, there are still many conflicting results from these population-based studies, and they should be interpreted carefully. Recognition of these factors and the mechanisms by which they contribute to Alzheimer's disease will be beneficial in the current treatment regimens for Alzheimer's disease and in the development of future therapies. Here we discuss vascular factors with respect to Alzheimer's disease and dementia and review the factors that give rise to vascular dysfunction and contribute to Alzheimer's disease.

The impact of vascular burden on late-life depression

Small vessel pathology and microvascular lesions are no longer considered as minor players in the fields of cognitive impairment and mood regulation. Although frequently found in cognitively intact elders, both neuroimaging and neuropathological data revealed the negative impact on cognitive performances of their presence within neocortical association areas, thalamus and basal ganglia. Unlike cognition, the relationship between these lesions and mood dysregulation is still a matter of intense debate. Early studies focusing on the role of macroinfarct location in the occurrence of post-stroke depression (PSD) led to conflicting data. Later on, the concept of vascular depression proposed a deleterious effect of subcortical lacunes and deep white matter demyelination on mood regulation in elders who experienced the first depressive episode. More recently, the chronic accumulation of lacunes in thalamus, basal ganglia and deep white matter has been considered as a strong correlate of PSD. We provide here a critical overview of neuroimaging and neuropathological sets of evidence regarding the affective repercussions of vascular burden in the aging brain and discuss their conceptual and methodological limitations. Based on these observations, we propose that the accumulation of small vascular and microvascular lesions constitutes a common neuropathological platform for both cognitive decline and depressive episodes in old age.

The enigma of vascular cognitive disorder and vascular dementia

The prevalence, morphology and pathogenesis of vascular dementia (VaD), recently termed vascular cognitive impairment, are a matter of discussion, and currently used clinical diagnostic criteria show moderate sensitivity (average 50%) and variable specificity (range 64-98%). In Western clinic-based series, VaD is suggested in 8-10% of cognitively impaired aged subjects. Its prevalence in autopsy series varies from 0.03 to 58%, with reasonable values of 8-15%, while in Japan it is seen in 22-35%. Neuropathologic changes associated with cognitive impairment include multifocal and/or diffuse disease and focal lesions: multi-infarct encephalopathy, white matter lesions or arteriosclerotic subcortical (leuko)encephalopathy, multilacunar state, mixed cortico-subcortical type, borderline/watershed lesions, rare granular cortical atrophy, post-ischemic encephalopathy and hippocampal sclerosis. They result from systemic, cardiac and local large or small vessel disease. Recent data indicate that cognitive decline is commonly associated with widespread small ischemic/vascular lesions (microinfarcts, lacunes) throughout the brain with predominant involvement of subcortical and functionally important brain areas. Their pathogenesis is multifactorial, and their pathophysiology affects neuronal networks involved in cognition, memory, behavior and executive functioning. Vascular lesions often coexist with Alzheimer disease (AD) and other pathologies. Minor cerebrovascular lesions, except for severe amyloid angiopathy, appear not essential for cognitive decline in full-blown AD, while both mild Alzheimer pathology and small vessel disease may interact synergistically. The lesion pattern of "pure" VaD, related to arteriosclerosis and microangiopathies, differs from that in mixed-type dementia (AD with vascular encephalopathy), more often showing large infarcts, which suggests different pathogenesis of both types of lesions. Due to the high variability of cerebrovascular pathology and its causative factors, no validated neuropathologic criteria for VaD are available, and a large variability across laboratories still exists in the procedures for morphologic examination and histology techniques.

Assessing the cognitive impact of Alzheimer disease pathology and vascular burden in the aging brain: the Geneva experience

The progressive development of Alzheimer disease (AD)-related lesions, such as neurofibrillary tangles (NFT), amyloid deposits and synaptic loss, and the occurrence of microvascular and small macrovascular pathology within the cerebral cortex are conspicuous neuropathologic features of brain aging. Recent neuropathologic studies strongly suggested that the clinical diagnosis of dementia depends more on the severity and topography of pathological changes than on the presence of a qualitative marker. However, several methodological problems, such as selection biases, case-control design, density-based measures and masking effects, of concomitant pathologies persisted. In recent years, we performed several clinicopathologic studies using stereological counting of AD lesions. In order to define the cognitive impact of lacunes and microvascular lesions, we also analyzed pure vascular cases without substantial AD pathology. Our data revealed that total NFT numbers in the CA1 field, cortical microinfarcts and subcortical gray matter lacunes were the stronger determinants of dementia. In contrast, the contribution of periventricular and subcortical white matter demyelinations had a modest cognitive effect even in rare cases with isolated microvascular pathology. Importantly, in cases with pure AD pathology, more than 50% of Clinical Dementia Rating scale variability was not explained by NFT, amyloid deposits and neuronal loss in the hippocampal formation. In cases with microvascular pathology or lacunes, this percentage was even lower. The present review summarizes our data in this field and discusses their relevance within the theoretical framework of the functional neuropathology of brain aging and with particular reference to the current efforts to develop standardized neuropathological criteria for mixed dementia.

Vascular cognitive impairment

Cognitive impairment commonly accompanies clinical syndromes associated with vascular disease of the brain. Because of evolving definitional criteria, however, the frequency of cognitive impairment attributable to cerebrovascular disease is difficult to determine. Dementia occurs in up to one-third of elderly patients with stroke, a subset of whom have Alzheimer's disease (AD) rather than a pure vascular dementia syndrome. In fact, pure vascular dementia has been shown to be uncommon in most large autopsy series. A mixed etiology of AD and cerebrovascular disease is thought to become more common with increasing age, although no clinical criteria for the diagnosis of AD with cerebrovascular disease are currently available. Epidemiological studies have implicated subcortical small-vessel disease as a risk factor for cognitive impairment and dementia, but the cognitive expression and clinical significance of MRI white matter changes in individual patients is difficult to establish. The frequency of specific neuropathologic features of vascular cognitive impairment depends largely on study inclusion criteria. Cerebral meningocortical microangiopathies with distinctive clinicopathological profiles are associated with dementia in both sporadic cases and familial syndromes. In patients with AD, the contribution of amyloid-beta protein to the degree of cognitive impairment has not been clearly defined.

Voxel-based morphometry demonstrates reduced grey matter density on brain MRI in patients with diabetic retinopathy

AIMS/HYPOTHESIS

In addition to nephropathy, retinopathy and peripheral neuropathy, a microvascular complication of type 1 diabetes that may be tentatively referred to as 'diabetic encephalopathy' has gained increasing attention. There is growing evidence that lowered cognitive performance in patients with type 1 diabetes is related to chronic hyperglycaemia rather than recurrent episodes of severe hypoglycaemia, as previously speculated. The aim of our study was to use magnetic resonance imaging (MRI) to establish whether long-term hyperglycaemia, resulting in advanced retinopathy, contributes to structural changes in the brain (reduced grey matter).

SUBJECTS, MATERIALS AND METHODS

We applied voxel-based morphometry on magnetic resonance images to compare grey matter density (GMD) between three groups of participants. GMD is used as a marker of cortical atrophy. We compared 13 type 1 diabetic patients with a microvascular complication (i.e. proliferative retinopathy) with 18 type 1 diabetic patients who did not have retinopathy in order to assess the effects of microvascular changes on GMD. Both patient groups were compared with 21 healthy control subjects to assess the effect of diabetes in itself.

RESULTS

Patients with diabetic retinopathy showed reduced GMD in the right inferior frontal gyrus and right occipital lobe compared both with patients without retinopathy and with healthy controls (p<0.05).

CONCLUSIONS/INTERPRETATION

Our data show that patients with type 1 diabetes, who, as a consequence of chronic hyperglycaemia, had developed advanced retinopathy, also showed increased focal cortical atrophy on brain MRI.

The effects of Choto-san on the mRNA expression of Alzheimer's disease related factors in the permanent ischemic rat brain

Choto-san is a Kampo medicines that has been used clinically for the treatment of dementia. We measured the mRNA expressions of some factors related to Alzheimer's disease in a dementia model rat brain. The expressions of beta-amyloid precursor protein, gamma-secretase, alpha7 nicotinic acetylcholine receptor, neprilysin, and insulin degrading enzyme (IDE) were significantly increased on day 4 after permanent occlusion of the bilateral common carotid arteries (2VO). Choto-san inhibited the enhancement of IDE expression caused by 2VO, although it failed to show any effects on the expressions of the other molecules. These results suggest that Choto-san may produce a state in which it is not necessary to induce IDE expression to demonstrate the anti-dementia effects.

Understanding the pathology of vascular cognitive impairment

The prevalence, morphology and pathogenesis of vascular dementia (VaD), recently termed vascular cognitive impairment (VCI), and of mixed dementia (Alzheimer disease+vascular encephalopathy) are a matter of discussion and no validated neuropathologic criteria for these disorders are currently available. In Western memory clinic-based series, VaD/CVI is suggested in 8-10% of cognitively impaired elderly; its prevalence in autopsy series ranges from 0.03% to 58% (mean 5-15%). Fairly unusual as an isolated nosological entity, CVI appears to correlate with focal, multifocal or diffuse cortical and/or subcortical microinfarcts and lacunes often affecting strategically important brain areas (thalamus, frontobasal, limbic system), hemispheric white matter and, less often, large brain areas. They result from systemic, cardiac or local large or small vessel disease. The lesion pattern in "pure" VCI with predominant multiple small (subcortical) lesions related to microangiopathies differs from that in "mixed dementia" (AD+VaD), more often associated with large infarcts, suggesting different pathogenesis. In very old subjects, selective hippocampal sclerosis may be accompanied by multiple other vascular pathologies. Minor cerebrovascular lesions (CVL), except for severe amyloid angiopathy, appear not essential for cognitive decline in full-blown AD, while both mild AD-type pathology and small vessel disease may interact synergistically in "unmasking" or promoting dementia. AD pathology is significantly less severe in the presence of cerebrovascular lesions. Further studies are needed to validate diagnostic criteria for VCI and to clarify the impact of vascular lesions on cognitive impairment.

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.

Diagnosis, risk factors, and treatment of vascular dementia

Although the introduction of modern neuroimaging techniques and standardized clinical evaluations has improved the identification of cerebrovascular disease, the clinical diagnosis of vascular dementia (VaD) is still problematic. Neuropathologic studies have found the current clinical criteria for VaD had low sensitivity with high specificity, suggesting that cerebrovascular disease of sufficient severity to cause cognitive deficits is frequently associated with other disease processes (eg, Alzheimer's disease). The critical factors about the diagnosis of VaD are centered on two issues: definition of dementia and determination of vascular disease. The current clinical criteria for VaD have different definitions of dementia, which are mainly based on an Alzheimer's disease-like presentation, and severe vascular disease can present with or without history of clinical strokes. Therefore, there is a need for a better definition of VaD. This is extremely important to better understand its risk factors, as well as to create homogenous cohorts suitable for drug trials.

Cortical Microinfarcts and Demyelination Significantly Affect Cognition in Brain Aging

Background and Purpose— Microvascular lesions are common in brain aging, but their clinical impact is debated. Methodological problems such as the masking effect of concomitant pathologies may explain discrepancies among previous studies. To evaluate the cognitive consequences of such lesions, we prospectively investigated elderly individuals with various degrees of cognitive impairment but without significant neurofibrillary tangle pathology or macrovascular lesions.

Methods— This was a clinicopathological study of 45 elderly individuals. Cognitive status was assessed prospectively with the Clinical Dementia Rating (CDR) scale; neuropathological evaluation included Aβ-protein deposition staging and bilateral semiquantitative assessment of cortical microinfarcts, focal cortical and white matter glioses, and diffuse white matter and periventricular demyelination.

Results— In a univariate logistic regression model, cortical microinfarcts explained 36.1% of the variability in CDR; periventricular demyelination, 10.6%; and diffuse white matter demyelination, 4.6%. After controlling for age and Aβ-protein deposition, cortical microinfarcts were the best predictor of cognitive status (19.9% of CDR variability), whereas periventricular and diffuse white matter demyelination accounted for 9.7% and 5.4% of CDR variability, respectively. Altogether, these 3 types of microvascular lesions explained 27.9% of the clinical variability. Focal cortical and white matter glioses were not related to clinical outcome.

Conclusions— Our data imply that cortical microinfarcts and both periventricular and deep white matter demyelination contribute significantly to the progression of cognitive deficits in brain aging. In contrast, the neuropathological evaluation of focal cortical and white matter gliosis has no clinical validity.

Confused and disturbed behavior in the elderly following silent frontal lobe infarction

It is unclear whether silent frontal lobe infarction is truly asymptomatic; frontal behavioral syndromes following strokes have rarely been reported. We studied 12 elderly patients with silent frontal lobe infarction who were exhibiting confused and disturbed behavior. Ten were male and two female; their ages ranged from 68 to 79 (mean 78). Three groups of symptom clusters emerged: changes in mood and emotional behavior, cognitive deterioration with minor psychiatric symptoms, and a confusional state. When related to the CT scan location, three regions were identified: predominantly orbitofrontal, deep white matter and caudate, and border-zones, respectively. These findings were related to what is known about the neuroanatomic location of the lesions and the role of the frontal subcortical circuitry in relation to behavior. The different manifestations could be explained by damage to the frontal lobe or interruption of the complex frontal subcortical circuits.

Validation study of a CT-based weighted rating scale for subcortical ischemic vascular disease in patients with mild cognitive deterioration

OBJECTIVES

Subcortical ischemic vascular disease (SIVD) is frequently associated with cognitive impairment. Rating scales to grade cerebrovascular disease are available, but their sensitivity to the clinical features of mild SIVD is unclear. The aim of the study is to devise and validate a computed tomography (CT)-based visual rating scale sensitive to SIVD in patients with mild cognitive deterioration.

METHODS

Subjects were 122 consecutive outpatients of a memory clinic (mean age +/- SD 77 +/- 8 years, 71% females, mean +/- SD score of mental state exam 22 +/- 3, 61% with clinical dementia rating of 0.5 and 39% of 1). Diffuse leukoaraiosis, fuzzy and patchy lesions, and lacunes were assessed on ordinary CT films and weights were computed based on clinical indicators of SIVD. A continuous score and an ordinal class (0-3) with higher values indicating higher vascular damage were derived.

RESULTS

Intraclass correlation coefficients for intra- and interrater reliability of the subcortical vascular score and class ranged from 0.84 to 0.88. Convergent validity versus the scale of Wahlund et al. was good (Spearman's correlation coefficient between 0.53 and 0.73, p < 0.0005). Known-group validity was assessed versus clinical diagnoses of degenerative (mild cognitive impairment determined by Petersen et al. and NINCDS-ADRDA probable Alzheimer's disease; n = 58), mixed (possible Alzheimer's disease with cerebrovascular disease; n = 21), and vascular cognitive impairment (criteria of Erkinjuntti et al. for subcortical vascular dementia and cognitive impairment; n = 43). Patients with degenerative cognitive impairment were more often in the lower subcortical vascular classes (43% in class 0, 43% in class 1, 14% in class 2, and 0% in class 3), while patients with mixed (0, 24, 24, and 52%) and vascular cognitive impairment were in increasingly higher subcortical vascular classes (0, 12, 35, 53%; p < 0.00005). Criterion-related validity was assessed versus clinical indicators of cerebrovascular disease. Hypertension, platelet aggregation inhibitor use, balance, gait, and bradykinesia increased linearly with increasing subcortical vascular class (p for trend <0.02).

CONCLUSIONS

This rating scale is valid and sensitive to capture different degrees of SIVD associated with mild cognitive deterioration.

The vascular lesions in vascular and mixed dementia: the weight of functional neuroanatomy

Vascular dementia appears rarer than previously thought, but the contribution of vascular lesions to cognitive impairment in Alzheimer's disease (AD) affected patients (mixed dementias) is now recognized as frequent. The role of strategic areas of the brain involved in the cognitive decline induced by vascular lesions and their relative contributions to the severity of the dementing process remain poorly understood. We determined the relationship between the severity of clinical dementia and the volume of different brain areas affected by infarcts in a prospective clinicopathological study in elderly patients. A volumetric study of the functional zones of Mesulam's human brain map affected by vascular lesions was made and correlations between quantified neuropathological data and the severity of dementia were performed in cases with large vascular lesions only, pure AD, and both lesions. The severity of cognitive impairment was significantly correlated with the total volume of infarcts but in a multi-variate model the volume destroyed in the limbic and heteromodal association areas, including the frontal cortex and in the white matter explained 50% of the variability in MMSE and GDS. The total volume of ischemic lesions explained only 0.1-5% of the variability in MMSE and GDS. Age only explained an extra of 0.1-1.6%. This study confirms that infarcts located in strategic areas have a role in the mechanism of cognitive impairment and brings a key for their quantification. It may be useful for developing neuropathological criteria in multi-infarct and mixed dementias.

Vascular-ischemic dementia: an update

Both the clinical criteria and morphologic substrates of dementia resulting from cerebrovascular disease and its relation to Alzheimer disease and other age-related brain changes are controversial. In clinical and autopsy studies in the Western world the prevalence of vascular-ischemic dementia (VID) is around 7-10%, while vascular cognitive impairment without dementia is much more frequent and the risk of poststroke dementia is increased in patients with prestroke cognitive decline. In contrast to previous suggestions that VID was largely the result of large hemispheral infarcts, according to recent studies, it is most commonly associated with widespread small ischemic or vascular lesions (microinfarcts, lacunes) throughout the CNS with predominant subcortical lesions in the basal ganglia and white matter or in strategically important brain regions (thalamus, hippocampus). The lesion pattern of rare "pure" VID, which is related to arteriolosclerotic and hypertensive microangiopathy, differs from that in mixed type dementia (Alzheimer disease and cerebrovascular lesions) that more often shows larger hemispheral infarcts. Another form of VID that is not infrequent in very old subjects is hippocampal sclerosis, a selective damage to the hippocampus that is often accompanied by multiple other cerebrovascular lesions. Both, mild Alzheimer type pathology and small vessel disease-associated subcortical vascular pathology appear to be common and may interact in causing cognitive decline, but the impact of cerebrovascular lesions on cognitive impairment and dementia needs to be further elucidated.

Epidemiology: identifying vascular cognitive impairment

There has been a move in recent years to recognize that the most effective treatment for vascular dementia, and for the mixed component of mixed vascular dementia and Alzheimer's disease, lies not in treatment but in prevention. This requires that cases be identified before the onset of vascular damage (a stage termed "brain-at-risk") or, failing this, as soon as possible but certainly before dementia has developed. These early stages are termed vascular cognitive impairment (VCI). No criteria exist for this early stage of cognitive loss due to cerebrovascular disease and relatively little data exist to indicate how such cases might be identified. The data that do exist suggest that many of the traditional "vascular" features of sudden onset and stepwise progression, etc., are not common in VCI and new criteria will be needed to identify cases. This paper summarizes the data that describe the clinical, neuropsychological, and radiological features that are to be expected in VCI.

The concept of vascular cognitive impairment

Vascular dementia (VaD) is increasingly recognised to reflect an outmoded concept in that it identifies cases too late for preventive therapy to have an opportunity to prevent the development of dementia and uses a cognitive paradigm inappropriately based on Alzheimer's disease. A replacement is urgently required and a new concept, that of vascular cognitive impairment (VCI), has been proposed to meet this need. It is imperative that criteria for VCI are developed on the basis of knowledge and data rather than supposition and assumption, as was the case for VaD. This review details the state of knowledge that we have now reached concerning the fundamental points of severity and cognitive paradigm and also covers a number of other imaging-related essential points embracing atrophy, leukoaraiosis, infarct volume and infarct location. Finally, the increasingly important concept of mixed dementia (co-existent Alzheimer's disease and VCI) is discussed.

The pathology of ischemic-vascular dementia: an update

In Western memory clinic-based series, ischemic-vascular dementia (IVD) is seen in 8-10% of cognitively impaired elderly subjects. Its prevalence in autopsy series ranges from 0.03% to 58% with reasonable values of 4-10%, while in Japan, IVD is seen in 22-35% and mixed-type dementia (MTD) (Alzheimer disease/AD+IVD) in 6-11%. In a large Viennese autopsy series, "pure" IVD was observed in 9.4% of demented elderly and in 2.9% of those clinically diagnosed as possible/probable AD MTD was observed in 3.1% and 1.3% respectively. The major morphological types of IVD are multi-infarct encephalopathy (MIE), small vessel infarct type-strategic infarct dementia (SID), subcortical arteriosclerotic leukoencephalopathy (Binswanger), multilacunar state, mixed cortico-subcortical type, granular cortical atrophy, and post-ischemic encephalopathy. In contrast to previous suggestions that IVD is mainly the result of large hemispheral infarcts or losses of over 100 ml of brain tissue, recent data indicate that cognitive decline is commonly associated with widespread small ischemic or vascular lesions (microinfarcts, lacunes) throughout the brain with predominant involvement of the basal ganglia, white matter, and hippocampus. The lesion pattern of "pure" IVD, which is related to arteriolosclerosis and hypertensive microangiopathy, differs from that in mixed-type dementia, more often showing large infarcts. Although recent studies suggest that concomitant small cerebral infarcts do not significantly influence the overall rate of cognitive decline in AD patients or may be important for mental decline in early AD, both mild AD pathology and microvascular cerebral lesions appear to be common and may interact in "unmasking" or promoting dementia.

Stroke-related dementia

Three months after a stroke, one quarter to one third of patients meet operationalized criteria for dementia, and an even greater proportion have cognitive impairment short of dementia. A significant number of these patients had mental deterioration before the stroke, implying an underlying neurodegenerative process. Current diagnostic criteria do not reflect these facts, and in addition to artificially using cerebrovascular disease to differentiate Alzheimer's disease and vascular dementia, they do not allow researchers and clinicians to identify subjects at risk in the early stages of cognitive decline. To be clinically useful, a broader concept of cognitive impairment in the setting of vascular disease needs to be developed based on data collected prospectively using cohorts of stroke patients.

How can cerebral infarcts and hemorrhages lead to dementia?

The incidence of new onset dementias is increased after stroke. The objective of this review is to investigate how cerebral infarcts and hemorrhages can lead to dementia. Stroke subtypes, total volume of cerebral lesion and functional tissue loss, and location of the lesions are the major determinant of dementia in stroke patients. The causal relationship between stroke and dementia is clear: (1) in young patients who are unlikely to have associated Alzheimer pathology; (2) when the cognitive functioning was normal before stroke, impaired immediately after, and does not worsen over time; (3) when the lesions are located in strategic areas; and (4) when a well-defined vasculopathy known to be associated with dementia is proven. However, white matter changes and associated Alzheimer pathology may also contribute to the dementia syndrome in stroke patients.

The nosology of dementia

The nosology of dementia has evolved from the simple distinctions between senility, degenerative dementia, and vascular insults that existed a few decades ago. The differentiation of normal cognitive aging from very mild dementia has sharpened considerably; however, appreciation of the heterogeneity of Alzheimer's disease (AD) and its clinical and pathologic overlap with other dementing disorders has blurred previous classification systems. Rather than viewing AD and vascular dementia, for example, as dichotomous entities, it may be more relevant to consider their additive or synergistic interactions producing dementia. Further elucidation of the nature and contribution of genetic factors in AD and related disorders will accelerate the use of genotype-phenotype correlations in dementia classification.

Neuropathologic substrates of ischemic vascular dementia

Ischemic vascular dementia (IVD) is a relatively uncommon entity, in the course of which multiple ischemic brain lesions result in progressive cognitive and memory impairment. Ischemic brain lesions may also aggravate the neuropsychologic deficit of Alzheimer disease (AD). In this review we summarize our experience based upon autopsy examination of the central nervous system in 20 patients (age range 68-92 years) enrolled in a longitudinal investigation of structural, neurochemical, functional neuroimaging, and neuropsychologic components of IVD, especially dementia associated with cerebral microvascular disease. While cystic infarcts were present in the CNS of 5 patients, the most commonly observed neuropathologic abnormalities were lacunar infarcts and microinfarcts--both types of lesion were encountered in over half of patients' brains. Evidence of (remote) hippocampal injury was found in 11/20 patients. Severe atherosclerosis and arterio/ arteriolosclerosis were both associated with the occurrence of multiple lacunar infarcts. Pronounced cerebral amyloid angiopathy (CAA) was noted in a single patient, who also showed other microscopic changes of severe AD. While fairly unusual as a nosologic entity, IVD appears to correlate with widespread small ischemic lesions distributed throughout the CNS. We furthermore propose an approach to quantifying the burden of ischemic vascular and parenchymal disease that may be associated with a dementia syndrome. A brief review of neuropathologic features of vascular dementia (both familial and sporadic) is presented.

Status of risk factors for vascular dementia

The two most common causes of vascular dementia (VAD) are dementia evolving in connection with multiple small or large strokes and dementia related to ischemic white-matter lesions (WMLs) of the brain. The knowledge about risk factors for these disorders is still scarce. Besides sharing risk factors with stroke, dementia with multiple small or large brain infarcts is also associated with non-vascular risk factors such as high alcohol consumption, psychological stress in early life, lower formal education, blue collar occupation, and occupational exposures. Risk factors for dementia in stroke victims include stroke-related and non-stroke related risk factors. Non-stroke-related factors are similar to those found in Alzheimer's disease. The main risk factors for ischemic WMLs are hypertension or increased blood pressure, but WMLs have also been associated with a number of other vascular risk factors. In recent years, Alzheimer's disease (AD) has also been reported to be associated with vascular risk factors, including hypertension, coronary heart disease, atrial fibrillation, diabetes mellitus, and WMLs. Although these associations may reflect an overdiagnosis of AD in cases with silent cerebrovascular disease, or that cerebrovascular disease increases the possibility that individuals with Alzheimer lesions will express a dementia syndrome, there are also alternative explanations. AD and cerebrovascular disease may for instance share similar risk factors or etiologic pathways. The pathogenetic implications for the association between AD and vascular factors need to be further explored. There is also a need for more studies on risk factors for VAD and risk factors for dementia in stroke samples, as well as studies on non-vascular risk factors for ischemic WMLs.

Atrial fibrillation and cognitive disorders in older people

OBJECTIVES

To find a correlation between chronic nonrheumatic atrial fibrillation (CNRAF) and cognitive impairment in a group of older, nondemented patients.

SETTING

Acute Care Unit for the Elderly, Poliambulanza Hospital, Brescia (Italy).

METHODS

Two hundred fifty-five hospital in-patients older than 70 years (42 with CNRAF and 213 controls with normal sinus rhythm) were assessed by complete clinical history, physical examination, ECG, serum albumin levels, APACHE II score, mental status (Mini-Mental State Exam [MMSE] and Geriatric Depression Score [GDS]), functional status (Barthel Index and instrumental activities of daily living [IADL]), number of prescribed drugs, and comorbidity (Charlson Index).

RESULTS

The group of patients with CNRAF had MMSE scores significantly lower than that of the reference group with normal sinus rhythm. Chronic nonrheumatic atrial fibrillation retained an independent relation to cognitive impairment also after adjusting for those variables associated with mental decline in univariate models (GDS, IADL, and APACHE II scores).

CONCLUSIONS

The results of this study support the relationship between nonrheumatic atrial fibrillation and impaired cognitive function. Independent of etiopathogenetic mechanisms (thromboembolic or hemodynamic hypotheses), prevention of cognitive impairment in older persons should take into account the treatment of atrial fibrillation and its consequences.

Vascular dementia: a contemporary review of epidemiology, diagnosis, prevention, and treatment

The past decade has seen a renewed interest in vascular dementia. Key epidemiologic studies have examined the prevalence, incidence, course and risk factors of vascular dementia. New classification systems have been developed to improve the reliability of the diagnosis, and there have been advances in diagnostic methodology, such as neuroimaging and neuropsychological assessment. New treatments for vascular dementia are being developed to protect the brain from cerebral ischemia and to limit progression of cognitive impairment. Diagnostic criteria for vascular dementia remain to be validated by carefully designed, systematic, clinicopathologic study. Once such criteria are validated, meaningful study of subgroups of vascular dementia can be explored. Until the relationship between vascular dementia and Alzheimer's disease is better defined, the nosology for vascular dementia may be defined best as dementia associated with stroke.

Aging and cerebrovascular disease

Aging influences cerebrovascular disease expression by a variety of mechanisms. Age-related changes in cerebral autoregulation, cellular metabolism, the blood-brain barrier, and autonomic function may leave the cerebrovascular system vulnerable to injury. Certain cerebrovascular disease, such as atrial fibrillation, watershed infarctions, carotid artery atherosclerosis, cerebral hemorrhages, subdural hematomas, and transient global amnesia manifest in the elderly. Vascular dementia and white matter disease are better understood with newer neuroimaging studies, careful neuropsychological and histopathologic examinations. Atherosclerosis and cerebral amyloid angiopathy may have larger roles than previously understood in Alzheimer's disease.

Prevalence of Alzheimer plaques in AIDS

OBJECTIVES

Both genetic and environmental risk factors for Alzheimer's disease have been identified. The best established environmental risk factor, head trauma, is thought to act through the triggering of an inflammatory response. Another stimulus to an inflammatory response in the brain is AIDS. Whether there is an increased prevalence of beta/A4 amyloid deposits in the form of argyrophilic plaques in the brains of patients with AIDS has therefore been investigated.

METHODS

The prevalence of argyrophilic amyloid plaques in the cerebral cortex of frontal and temporal lobes was compared in 97 cases of AIDS dying at ages 30-69 years with that in 125 age matched, non-HIV infected controls.

RESULTS

In the control group, and in AIDS, the prevalence of plaques increased with age (p=0.005 and 0.048 respectively). There was a significantly greater prevalence of argyrophilic plaques in the AIDS group as a whole (29%) (p < 0.004) and in those in the fourth decade (18%) (p < 0.014) than in control subjects (13% and 0% respectively).

CONCLUSION

There is a predisposition to argyrophilic plaque formation in the brain in AIDS. The findings support the view that a stimulus to an inflammatory response in the brain favours argyrophilic plaque formation. The clinical relevance of our findings is, as yet, unclear.

The relationship between blood pressure and dementia: a review

Hypertension has been related to the development of dementia, including Alzheimer's disease, and cognitive dysfunction in middle-aged and elderly populations. One possible explanation is that hypertension is a risk factor for cerebral infarcts and ischaemic subcortical white-matter lesions. Hypertension may also give rise to a blood-brain barrier dysfunction, which has been suggested to be involved in the aetiology and pathogenesis of Alzheimer's disease. Other possible explanations for the association are shared risk factors, such as psychological stress, and the formation of free oxygen radicals. Low blood pressure has also been hypothesized to give rise to brain damage and dementia. However, the brain is involved in blood pressure regulation and dementia disorders may therefore influence the blood pressure. The findings of an association between hypertension and dementia may have implications for prevention and treatment.

Fallacies in the pathological confirmation of the diagnosis of Alzheimer's disease

OBJECTIVE

Necropsy confirmed clinical diagnostic accuracy for Alzheimer's disease is claimed to exceed 90%. This figure contains two fallacies; it includes cases in which Alzheimer's disease exists with other diseases affecting cognition and the studies that report these figures excluded cases without necropsy (verification bias). The effect of these errors is estimated.

METHODS

Data were taken from the University of Western Ontario Dementia Study, a registry of dementia cases with clinical and psychometric follow up to necropsy based in a university memory disorders clinic with secondary and tertiary referrals. Data were available on 307 patients; 200 (65%) had clinically diagnosed Alzheimer's disease, 12 (4%) vascular dementia, 47 (15%) mixed dementia, and 48 (16%) had other diagnoses. One hundred and ninety two of 307 cases (63%) died and 122 of 192 fatalities (64%) had necropsies. The pathological material was interpreted in two ways, allowing and disallowing coexistent disease in making a diagnosis of Alzheimer's disease. In cases without necropsy, progressive cognitive loss was used as a marker for degenerative dementia. The outcome measures of interest were the positive predictive value of a clinical diagnosis of Alzheimer's disease allowing and disallowing coexistent diseases and with and without correction for cases that were not necropsied.

RESULTS

The clinical diagnoses differed significantly between the population who died and those who did not. In cases without necropsy, 22% had no dementia on follow up, concentrated in early cases and men, showing considerable scope for verification bias. The positive predictive value of a diagnosis of Alzheimer's disease was 81% including coexistent diseases, falling to 44% when limited to pure cases. Combined, these factors reduce the positive predictive value to 38% for pure Alzheimer's disease.

CONCLUSIONS

Correction for dual pathology and verification bias halves the positive predictive value of the clinical diagnosis of Alzheimer's disease. Data derived from necropsy studies cannot be extrapolated to the whole population. This has important implications including uncertainty about diagnosis and prognosis and a dilution effect in therapeutic trials in Alzheimer's disease.

Neuropathological assessment of the lesions of significance in vascular dementia

OBJECTIVES

To better define the neuropathology of vascular dementia.

METHODS

The neuropathological findings in 18 elderly, undemented subjects free of cerebrovascular disease were compared with 19 elderly undemented subjects who had cerebrovascular disease (many of whom had had a "stroke") and 24 elderly demented subjects who had cerebrovascular disease, but no other pathology to account for dementia. Cases in all groups were selected for absence or no more than very mild Alzheimer type pathology.

RESULTS

Microvascular brain damage in the form of severe cribriform change and associated subcortical white matter damage and microinfarction were correlated with a history of dementia. Severe cribriform change was much more common and microinfarction somewhat more common in the demented group with vascular disease than the undemented group with vascular disease (P=0.0006 and P=0.031 respectively). Other findings of note were that congophilic angiopathy had a greater prevalence in the vascular dementia group than the control group, single cerebral infarcts were more common in the group who were undemented with vascular disease than in the group with dementia and vascular disease (P=0.0028), and the last group lacked evidence of macroscopic infarction more often than the first (P=0.034). There was a non-significant trend for the ratio of infarcted:uninfarcted tissue in one cerebral hemisphere to be higher in the group with dementia and vascular disease than in the group with vascular disease but no dementia.

CONCLUSIONS

Microvascular disease, not macroscopic infarction, was the chief substrate of vascular dementia in this series of cases.

Fundamental pathological lesions in vascular dementia

This review concerns the fundamental cerebral lesions in cases of vascular dementia. Extracerebral vascular alterations are dominated by atherosclerosis with or without thrombosis. In addition, occlusion of extracerebral arteries can be induced by thrombo-embolism and in rare cases by other vascular diseases, chiefly arteritis. Intracerebral microangiopathies are usually of arteriolosclerotic or hyalinotic types in which there is degeneration of smooth muscle cells of the media and deposition of components of extracellular matrix, chiefly collagens. Ageing, chronic hypertension, hyperlipidemias and diabetes are important factors inducing vascular lesions. The vascular lesions, often combined with systemic factors, may produce various ischemic and edematous alterations of the brain parenchyma. Occlusion and obliteration of arteries (macroangiopathy) are associated with large infarcts, whereas microangiopathy may cause lacunar infarcts and some forms of white matter degeneration. Cases of vascular dementia usually present many types of lesions in the brain parenchyma and its arterial supply. The extent and location of the injuries differ considerably from case to case. Location of the lesions, volume of destroyed tissue, multiplicity and bilateral occurrence are most important parameters underlying the clinical manifestations in vascular dementia. A strategic location of a small injury is in some cases of particular importance.

Vascular dementia of Binswanger's type: clinical, neuroradiological and 99mTc-HMPAO SPET study

In 24 patients with vascular dementia of Binswanger's type (VDBT) and 14 age-matched neurologically normal volunteers, we investigated the relationship between clinical features, white matter lesions (leuco-araiosis) and cerebral atrophy on computed tomographic (CT) scan, and regional cerebral blood flow. All subjects underwent the Mini-Mental State Examination of Taiwan, version 1 (MMSE-T1), for assessing the severity of cognitive impairment. The patients were subdivided into two groups, one with mild to moderate (group I, MMSE-T1 scores: 11-24, n=11), and the other with severe dementia (group II, MMSE-T1 scores: below 10, n=13). White matter degeneration was evaluated with densitometric methods. Loss of brain parenchyma was estimated with seven linear measurements (Evan's ratio, third ventricle ratio, width of temporal horn tip, anterior-posterior length of temporal horn, anterior-posterior length of Sylvian fissure and width of frontal interhemispheric fissure) by CT scans. Regional cerebral blood flow was determined with technetium-99m hexamethylpropylene amine oxime (HMPAO) single-photon emission tomography (SPET). In neuroimaging studies, subcortical leuco-araiosis was localized at the frontal region in group I patients and scattered diffusely in group II patients. 99mTc-HMPAO SPET analysis revealed reduction of regional cerebral blood flow in the frontal lobe in group I patients and widespread reduction of regional cerebral blood flow in group II patients. A correlation between frontal leuco-araiosis and perfusion defect of the frontal pole was demonstrated in group I patients, showing findings typical of subcortical dementia. There was no difference in frontal atrophic measurements between group I patients and controls. Ratios of volumes of lost brain parenchyma and leuco-araiosis were significantly higher in group II patients than in the age-matched controls, corresponding to a diffuse cerebral perfusion defect. These results suggest that patients with VDBT have early frontal lobe involvement with posterior progression. Patients with mild VDBT are more likely to show reduction of frontal cerebral blood flow and leuco-araiosis, while those with severe VDBT are more likely to have diffuse leuco-araiosis, cerebral hypoperfusion and brain atrophy.

15-year longitudinal study of blood pressure and dementia

BACKGROUND

Vascular causes of dementia may be more common than supposed. Vascular factors may also have a role in late-onset Alzheimer's disease, but the role of hypertension in the development of dementia is unclear.

METHODS

As part of the Longitudinal Population Study of 70-year-olds in Göteborg, Sweden, we analysed the relation between blood pressure and the development of dementia in the age intervals 70-75, 75-79, and 79-85 years in those non-demented at age 70 (n = 382). The sample was followed up for 15 years and examined repeatedly with a comprehensive investigation, including a psychiatric and physical examination. a

FINDINGS

Participants who developed dementia at age 79-85 had higher systolic blood pressure at age 70 (mean 178 vs 164 mm Hg, p = 0.034) and higher diastolic blood pressure at ages 70 (101 vs 92, p = 0.004) and 75 (97 vs 90, p = 0.022) than those who did not develop dementia. For subtypes of dementia, higher diastolic blood pressure was recorded at age 70 (101, p = 0.019) for those developing Alzheimer's disease and at age 75 (101, p = 0.015) for those developing vascular dementia than for those who did not develop dementia. Participants with white-matter lesions on computed tomography at age 85 had higher blood pressure at age 70 than those without such lesions. Blood pressure declined in the years before dementia onset and was then similar to or lower than that in non-demented individuals.

INTERPRETATION

Previously increased blood pressure may increase the risk for dementia by inducing small-vessel disease and white-matter lesions. To what extent the decline in blood pressure before dementia onset is a consequence or a cause of the brain disease remains to be elucidated.