Overlap between pathology of Alzheimer disease and vascular dementia

There is overwhelming evidence to suggest that the neuropathology of Alzheimer disease (AD) extends beyond amyloid plaques and neurofibrillary tangles. Review of various consortium data shows that more than 30% of AD cases exhibit cerebrovascular pathology. However, certain vascular lesions such as cerebral amyloid angiopathy, microvascular degeneration, and periventricular white matter lesions are evident in almost all cases of AD. Whether these vascular lesions are coincidental or causal in the pathogenetic processes of AD remains to be defined. Although systemic vascular influences such as hypertension, coronary artery disease, and other cardiovascular disturbances may be responsible for such pathology in AD, it is equally intriguing that about one third of patients diagnosed with vascular dementia (VaD) will have AD-type pathology at autopsy. Moreover, previous studies have revealed that deficits in cholinergic indices related to the basal forebrain neurones are apparent in multi-infarct dementia. In this short review, we evaluate cerebrovascular pathology of AD in light of peripheral vascular pathophysiology implicated in the etiopathogenesis of the dementia. We also consider pathological findings in relation to genetic influences such as apolipoprotein E that may shed light on the link between AD and VaD. In view of these commonalties, it is reasonable to consider the same treatment strategies for both AD and VaD.     

Vascular dementia and Alzheimer's disease: is there a difference? A comparison of symptoms by disease duration

This study examined differences between vascular dementia (VaD) by the NINDS/AIRENS criteria and Alzheimer's disease (AD) on clinical grounds. A consecutive series of 517 patients with probable and possible VaD or AD were evaluated for cognitive, functional, and behavioral symptoms and separated into three subgroups by duration of dementia. These AD and VaD subgroups were then compared on a series of standardized clinical measures. The only consistent trends were for VaD patients to be more depressed, more functionally impaired, and less cognitively impaired within each disease duration subgroup. The authors conclude that there are few differences between clinically diagnosed VaD and AD. Subclassification of VaD into subgroups will improve the clinical utility of this nosologic entity.     

Vascular and Alzheimer-type pathology in an autopsy study of African-Americans

The authors studied 13 autopsy brains from a larger cohort of 270 African-Americans with a clinical diagnosis of Alzheimer disease (AD), vascular dementia (VaD), or stroke without dementia. Two subjects exhibited changes of pure VaD, 5 had pure AD, and 6 showed a mixture of AD pathology and strokes. Overall, there was good agreement between the pathologic diagnoses and the clinical diagnoses.     

Differentiation of vascular dementia from AD on neuropsychological tests.

BACKGROUND: The concept of vascular dementia (VaD) is currently in a state of evolution. Memory impairment is emphasized as a primary criterion, reflecting the influence of AD on the concept of dementia. We have systematically reviewed whether the nature of neuropsychological dysfunction is distinct in AD and VaD, and whether similar defining criteria for the concept of dementia in both disorders can be supported. METHODS: We searched five bibliographic databases (Medline, Biological Abstracts, EMBASE, PsychINFO, PsychLIT) for research articles in which VaD and AD had been compared using neuropsychological tests and that met criteria for scientific merit. RESULTS: Of the 45 studies, 18 were excluded because of inadequacies, and the remaining 27 were analyzed. There were a number of similarities of dysfunction between VaD and AD. However, when matched for age, education, and severity of dementia, VaD patients had relatively superior function in verbal long-term memory and more impairment in frontal executive functioning compared with AD patients. Interpretation of the results is limited by uncertainty in diagnostic criteria for VaD, possible inclusion bias due to use of clinical diagnosis alone, possible overlap of AD and VaD, and the methodologic shortcomings of some studies. CONCLUSIONS: The neuropsychological differentiation of VaD from AD was consistent with the different neuroimaging findings in the two disorders, and argues for differential criteria for the definition of the syndromes. The simple application of Alzheimer's dementia criteria to VaD, with the inclusion of cerebrovascular disease etiology, may not be sufficient to capture the uniqueness of VaD.     

Facts, myths, and controversies in vascular dementia

Significant progress in the field of VaD resulted from publication of the NINIDS-AIREN Diagnostic Criteria for VaD (G.C. Roman, T.K. Tatemichi, T. Erkinjuntti, et al., Vascular dementia (VaD): diagnostic criteria for research studies. Report of the NINDS-AIREN International Workshop. Neurology 43 (1993) 250-260). Epidemiological studies confirmed the importance of VaD as the second most common cause of dementia in the elderly, representing 15-20% of all cases of dementia. In Europe and North America, Alzheimer's disease (AD) predominates over VaD in a 2:1 ratio; in contrast, in Japan and China VaD accounts for almost 50% of all dementias. Case-control studies have identified risk factors for VaD including ageing, hypertension, diabetes mellitus, hyperlipidemia, recurrent stroke, cardiac disease, smoking, sleep apnea, and more recently, hyperhomocysteinemia, among others. Hypertension treatment may prevent VaD and AD. This finding has enormous importance from the Public Health viewpoint to decrease the future number of patients with dementia in the elderly. Along with advances in the field of VaD came a number of controversies and damaging misconceptions and myths. Myth no. 1--Vascular dementia is a non-entity: The false idea that VaD does not exist is particularly destructive because it creates the perspective that VaD is unworthy of study or research. A condition that either does not exist or represents only a minute proportion of all cases of dementia in the elderly, lacks public health relevance and becomes a low priority for research by funding agencies and industry. In fact, vascular brain lesions are the commonest and most important component of dementia in the elderly. Myth no. 2--Vascular dementia is so difficult to diagnose that only experts can recognize and identify it accurately: VaD does exist and the diagnosis of post-stroke VaD, in particular is straightforward. Most cases fulfill NINDS-AIREN criteria for probable VaD; i.e., (1) there is acute onset of dementia demonstrated by impairment of memory and two other cognitive domains, such as orientation, praxis or executive dysfunction; (2) relevant cerebrovascular lesions are demonstrated by neuroimaging; and (3) a temporal relation between stroke and cognitive loss is evident. In the donepezil trials on VaD, post-stroke dementia represented about 75% of the >1,200 patients enrolled. Myth no. 3--Improvement in clinical trials of cholinergics in VaD is due to underlying AD, not to the vascular lesions. Experimental, clinical and pathological evidence has demonstrated cholinesterase deficits in VaD (independently of any concomitant AD pathology), including low acetylcholine in cerebrospinal fluid, and reduced choline acetyltransferase (ChAT) in the brain.     

The ABC of Alzheimer's disease: cognitive changes and their management in Alzheimer's disease and related dementias

Cognitive decline, commonly first recognized as memory impairment, is a typical feature of Alzheimer's disease (AD). Neuropathological changes in the cerebral cortex and limbic system lead to deficits in learning, memory, language, and visuospatial skills. The precise nature of cognitive dysfunction reflects the distribution of pathological changes in AD. These will vary along the disease severity continuum and may also depend on where the disease sits in the spectrum of dementia. For example, AD-related disorders such as Lewy body dementia (LBD) and Parkinson's disease dementia (PDD) also show symptoms of cognitive decline and share several pathological features, including degeneration of cortical cholinergic and striatal dopaminergic neurons. In vascular dementia (VaD), there is often an unequal distribution of cognitive deficit, with severe impairment in some functions and relative sparing of others. Cholinesterase (ChE) inhibitors, which help restore acetylcholine levels in the brain, are licensed for the symptomatic treatment of AD and have shown additional benefit in related dementias. Physiological correlates of cholinergic function/dysfunction in the brain include regional cerebral blood flow, glucose metabolism, and cerebrospinal fluid levels of ChE enzymes. These variables represent valuable markers of the clinical efficacy of ChE inhibitors. However, direct assessment of cognitive improvement, stabilization or decline is usually considered the key efficacy parameter in clinical studies of ChE inhibitors in AD and related dementias. Large-scale, placebo-controlled clinical studies of ChE inhibitors have demonstrated efficacy in treating the cognitive impairments associated with AD. Randomized comparative studies of ChE inhibitors are now under way to directly compare symptomatic efficacy and effects on disease progression. Clinical trial data of the cognitive effects of ChE inhibitors in AD, LBD, PDD, and VaD are discussed in detail in this article. The benefits of long-term treatment on symptomatic improvement in cognition and further potential disease-modifying effects are highlighted.     

Neuronal degeneration in locus ceruleus and cortical correlates of Alzheimer disease

Relationships were examined between neuronal degeneration in the nucleus locus ceruleus (nLC), a parameter of central noradrenergic impairment, and neocortical markers of Alzheimer disease (AD). The loss of nLC neurons was found to correlate significantly with norepinephrine concentration, choline acetyltransferase (ChAT) activity, and numbers of plaques and tangles on Brodmann area 24 (cingulate); ChAT and plaque counts in area 21 (temporal); and with ChAT activity in area 10 (frontal). In addition, nLC neuronal counts were correlated significantly with the severity and estimated duration of dementia. The number of neurofibrillary tangles in nLC, which did not correlate significantly with neocortical markers of AD, correlated with the estimated duration and severity of dementia. These data suggest that changes in central noradrenergic pathways are related to the pathophysiology of AD.     

Comparison between Alzheimer's disease and vascular dementia: implications for treatment

Virtually 90% of the elderly with late-onset dementia exhibit neuropathological features consistent with Alzheimer's disease (AD), vascular dementia (VaD) or dementia with Lewy bodies (DLB), alone or in combination. Both AD and DLB reveal extensive senile plaques containing amyloid beta whereas neurofibrillary tangles evident as tau pathology are fewer in DLB, which also bears diffuse cortical Lewy bodies. Interestingly, however, there is considerable overlap between AD and VaD in terms of both risk factors and pathology. Cholinergic deficits are also encountered in VaD, which like AD may respond to cholinergic therapy. Cerebrovascular pathology, ischemic brain damage and autonomic dysregulation resulting in cerebral hypoperfusion appears fundamental in the pathogenesis of late-onset dementias.     

Neuropsychiatric symptoms in 921 elderly subjects with dementia: a comparison between vascular and neurodegenerative types

Objective: i) to describe the neuropsychiatric profile of elderly subjects with dementia by comparing vascular (VaD) and degenerative dementias, i.e. dementia with Lewy bodies (DLB) and Alzheimer’s disease (AD); ii) to assess whether the severity and type of dementia are associated with clinically relevant neuropsychiatric symptoms (CR‐NPS). Method: One hundred and thirty‐one out‐patients with VaD, 100 with DLB and 690 with AD were studied. NPS were evaluated by the neuropsychiatric inventory (NPI). Results: Vascular dementia had lower total and domain‐specific NPI scores and a lower frequency of CR‐NPS than AD and DLB, for which frequency of CR‐NPS increased significantly with disease severity, particularly in AD. Logistic regression analysis showed that a higher CDR score and a diagnosis of degenerative dementia were independently associated with CR‐NPS. Conclusion: Vascular dementia is associated less with CR‐NPS than AD and DLB. Frequency of CR‐NPS increases with disease severity in AD and, to a lesser extent, in DLB.     

CT brain findings in clinical dementia investigation--underestimation of mixed dementia

Dementia has been found to display a more heterogeneous clinical picture than previously recognized. We investigated brain changes on computed tomography (CT) in a clinical dementia population consisting of 67 cases with Alzheimer's disease (AD), 13 with mixed dementia (AD and vascular dementia, VaD), 71 with VaD, and 12 cases that were not demented. Temporal cortical atrophy and atrophy around the temporal horns were more common in patients with mixed dementia compared to patients with VaD and the non-demented, respectively. Frontal white matter changes were present in 64% of AD, in 85% of mixed dementia and in 79% of VaD cases, but there were no differences between the dementia groups. Lacunes were present in almost 40% of AD cases and in 80 and 85% of VaD and mixed dementia cases, respectively. Only 14% of the VaD cases had large infarcts on the CT. We conclude that large infarcts were rare, even in VaD cases. The increased incidence of white matter changes and lacunes in AD patients strongly indicates an underestimation of the mixed dementia diagnosis. More distinct criteria for this diagnostic category are warranted.     

Dementia Rating Scale Performance: A Comparison of Vascular and Alzheimer's Dementia

Differences in the pattern of neuropsychological dysfunction associated with Alzheimer's disease (AD) and vascular dementia (VaD) were examined using the Dementia Rating Scale (DRS). We examined three groups of patients: (1) Patients with AD; (2) patients with single stroke (CVA); and (3) patients with multiple cerebral infarctions (MI). Comparisons of cognitive dysfunction were conducted on patients that met the DRS criteria for dementia. Dementia groups were similar in age, education, and severity of dementia. Comparisons of the AD and two VaD groups across the specific DRS-scales (Attention, Conceptualization, Construction, Initiation/Perseveration, and Memory) indicated that patients with AD were more impaired on the DRS-Memory while the patients with VaD were more impaired on the DRS-Construction. Additionally, patients with VaD related to MI scored lower on the DRS-Initiation/Perseveration as compared to patients with AD, and patients with AD scored lower on the DRS-Conceptualization as compared to patients with VaD related to CVA. These results are indicative of qualitative differences in the pattern of cognitive deficits associated with the two types of dementia.     

Dementia rating scale performance: a comparison of vascular and Alzheimer's dementia

Differences in the pattern of neuropsychological dysfunction associated with Alzheimer's disease (AD) and vascular dementia (VaD) were examined using the Dementia Rating Scale (DRS). We examined three groups of patients: (1) Patients with AD; (2) patients with single stroke (CVA); and (3) patients with multiple cerebral infarctions (MI). Comparisons of cognitive dysfunction were conducted on patients that met the DRS criteria for dementia. Dementia groups were similar in age, education, and severity of dementia. Comparisons of the AD and two VaD groups across the specific DRS-scales (Attention, Conceptualization, Construction, Initiation/Perseveration, and Memory) indicated that patients with AD were more impaired on the DRS-Memory while the patients with VaD were more impaired on the DRS-Construction. Additionally, patients with VaD related to MI scored lower on the DRS-Initiation/Perseveration as compared to patients with AD, and patients with AD scored lower on the DRS-Conceptualization as compared to patients with VaD related to CVA. These results are indicative of qualitative differences in the pattern of cognitive deficits associated with the two types of dementia.     

Neuropsychiatric symptoms and functional status in Alzheimer's disease and vascular dementia patients

Neuropsychiatric symptoms (NPS) are increasingly recognized as common in patients with dementia, both of degenerative (Alzheimer's disease, AD) or vascular origin (vascular dementia, VaD). In this study, 302 demented patients, 166 with AD and 136 with VaD, were evaluated for NPS according to the Neuropsychiatric Inventory (NPI) score at the Alzheimer's Evaluation Unit of Casa Sollievo della Sofferenza Hospital-IRCCS, San Giovanni Rotondo, Italy. A comprehensive geriatric assessment was also performed in all demented patients. The means of NPI scores did not differ in two groups. The overall prevalence of NPS was similar in both groups of patients (69.7% vs. 69.4%). Patients with AD had higher frequency in agitation/aggression and irritability/lability than VaD patients. Logistic analysis demonstrated a significant association between severity of the cognitive impairment and depression and eating disorders in both AD and VaD patients. The association with agitation/aggression, irritability/lability, and aberrant motor activity was found in AD only, and with apathy in VaD patients only. In both AD and VaD patients, there was a significant association between the impairment in activities of daily living (ADL) and the majority of NPI domains. A significant association was also found between the impairment of the instrumental activities of daily living (IADL) and agitation/aggression, anxiety, aberrant motor activity in AD and depression, apathy, irritability/lability, sleep disturbance and eating disorders in both AD and VaD patients. In particular, a causal mediation analysis was performed to better understand whether the relationship of NPS to functional impairment was direct or mediated by severity of cognitive dysfunction, i.e., Clinical dementia rating scale (CDR) score. Only agitation/aggression was mediated by the CDR score in affecting ADL status in VaD patients (OR: 1.12, 95% CI: 1.01-1.27). The NPI-Distress scores showed a significantly higher levels of distress in caregivers of AD than VaD. There were significant differences between AD and VaD patients with NPS, and these symptoms varied according to dementia subtype and severity and induced marked disability in ADL and IADL, increasing, prevalently, the distress of the caregivers of AD patients.     

Synaptic pathology in Alzheimer's disease: Relation to severity of dementia,but not to senile plaques,neurofibrillary tangles,or the ApoE4 allele

Summary Alzheimer's disease (AD) is characterised by an increased number of senile plaques (SP) and neuroflbrillary tangles (NFT) as compared with that found in non-demented individuals of the same age, and a marked degeneration and loss of synapses. One of the main risk-factors for the disorder is inheritance of the apolipoprotein E4 (ApoE4) allele. To further study the relation between these pathogenetic substrates for AD, we quantified the synaptic vesicle membrane protein rab3a in brain tissue from 19 patients with AD and 9 age-matched control subjects. Rab3a levels were reduced in AD, both in the hippocampus (60% of control level, p < 0.0001), and in the frontal cortex (68% of control level, p < 0.01), but not in the cerebellum (92% of control level). Within the AD group, lower rab3a levels were found both with increasing duration and severity of dementia. These findings further support that synaptic pathology is closely correlated to the clinical dementia in AD. In contrast, no significant correlations were found between SP counts and duration or severity of dementia, while higher NFT counts in the frontal cortex were found with increasing severity of dementia (r=0.54, p < 0.05). There were no significant correlations between the rab3a level and SP or NFT counts, and by immunohistochemistry, reduced rab3a immunostaining was found throughout the neuropil in AD brain, without relation to SP or NFT. These findings suggest that the synaptic pathology in AD is not closely related to the presence of SP and NFT. No significant differences in rab3a levels were found in any brain region between AD patients possessing different numbers of the ApoE4 allele, suggesting that, although ApoE4 is a risk factor for earlier development of AD, the degree of synaptic pathology does not differ between patients with or without the ApoE4 allele.     

Cholinergic dysfunction in vascular dementia

Vascular dementia (VaD) is the second most common type of dementia in the elderly after Alzheimer’s disease (AD). Evidence is presented indicating the occurrence of cholinergic dysfunction in VaD, independent from AD. Controlled clinical trials of cholinesterase inhibitors (ChEIs) in VaD and in patients with AD plus cerebrovascular disease are reviewed. Compared with placebo, ChEI treatment improves cognition, behavior, and activities of daily living. Cholinergic deficits in patients with VaD may result from ischemia of basal forebrain cholinergic nuclei that are irrigated by penetrating arteries that are highly susceptible to arterial hypertension, or from ischemic lesions in basal ganglia or white matter that sever the extensive cholinergic cortical projections. Cholinergic stimulation produces increases in cortical cerebral blood flow that may be relevant to the therapeutic effect of ChEIs.     

Quantification of myelin loss in frontal lobe white matter in vascular dementia, Alzheimer’s disease, and dementia with Lewy bodies

The aim of this study was to characterize myelin loss as one of the features of white matter abnormalities across three common dementing disorders. We evaluated post-mortem brain tissue from frontal and temporal lobes from 20 vascular dementia (VaD), 19 Alzheimer’s disease (AD) and 31 dementia with Lewy bodies (DLB) cases and 12 comparable age controls. Images of sections stained with conventional luxol fast blue were analysed to estimate myelin attenuation by optical density. Serial adjacent sections were then immunostained for degraded myelin basic protein (dMBP) and the mean percentage area containing dMBP (%dMBP) was determined as an indicator of myelin degeneration. We further assessed the relationship between dMBP and glutathione S-transferase (a marker of mature oligodendrocytes) immunoreactivities. Pathological diagnosis significantly affected the frontal but not temporal lobe myelin attenuation: myelin density was most reduced in VaD compared to AD and DLB, which still significantly exhibited lower myelin density compared to ageing controls. Consistent with this, the degree of myelin loss was correlated with greater %dMBP, with the highest %dMBP in VaD compared to the other groups. The %dMBP was inversely correlated with the mean size of oligodendrocytes in VaD, whereas it was positively correlated with their density in AD. A two-tier regression model analysis confirmed that the type of disorder (VaD or AD) determines the relationship between %dMBP and the size or density of oligodendrocytes across the cases. Our findings, attested by the use of three markers, suggest that myelin loss may evolve in parallel with shrunken oligodendrocytes in VaD but their increased density in AD, highlighting partially different mechanisms are associated with myelin degeneration, which could originate from hypoxic–ischaemic damage to oligodendrocytes in VaD whereas secondary to axonal degeneration in AD.     

Depression in vascular dementia is quantitatively and qualitatively different from depression in Alzheimer's disease

BACKGROUND/AIMS: To compare the prevalence and characteristics of depression in vascular dementia (VaD) and Alzheimer's disease (AD) after adjusting for dementia severity and gender. METHODS: One hundred and eight pairs of VaD and AD patients matched for dementia severity and gender were assessed. RESULTS: Major depressive disorder (MDD) was more prevalent in the VaD group than in the AD group (20.4% in VaD, 10.2% in AD, p = 0.04, Cochran-Mantel-Haenszel, CMH, test) regardless of the dementia severity and gender. The odds ratio for developing MDD in the VaD group versus the AD group was estimated to be 2.20 (95% confidence interval = 1.02-4.74). Neurovegetative symptoms such as 'felt tired and weak all the time' (30.6% in VaD, 13.9% in AD, p = 0.003, CMH test) and 'changed weight without trying' (16.7% in VaD, 6.5% in AD, p = 0.02, CMH test) were more prevalent in the VaD group than in the AD group. CONCLUSION: Depression in VaD was quantitatively and qualitatively different from that in AD regardless of the severity of dementia and gender; depression was more prevalent, severer and more retarded and vegetative in VaD than in AD.     

Decreasing myelin density reflected increasing white matter pathology in Alzheimer's disease--a neuropathological study

BACKGROUND: White matter disease (WMD) is frequently seen in Alzheimer's disease (AD) at neuropathological examination. It is defined as a subtotal tissue loss with a reduction of myelin, axons and oligodendrocytes as well as astrocytosis. Studies quantitatively defining the myelin loss in AD are scarce. The aim was to develop a method that could provide numerical values of myelin density in AD. The purpose was to compare the myelin contents in increasing grades of pathology of WMD, with age and cortical AD pathology as well as in different regions of the brain in AD. MATERIAL AND METHODS: Sixteen cases with AD and concomitant WMD were investigated with an in-house developed image analysis technique to determine the myelin attenuation with optical density (OD) in frontoparietal, parietal, temporal and occipital white matter on whole brain coronal sections stained for myelin with Luxol Fast Blue (LFB). The OD values in LFB were compared grouped according to Haematoxylin/Eosin (HE) evaluated mild, moderate and severe WMD or normal tissue. The OD values were also correlated with age and cortical AD pathology and compared between the different studied white matter regions. RESULTS: Increasing severity of WMD was associated with a statistically significant OD reduction. No correlation was seen between age and OD or overall cortical AD pathology. The OD values were significantly lower in frontoparietal-compared to occipital white matter. CONCLUSIONS: Myelin loss in AD with WMD is a marked morphologic component of the disease and it is possible to determine the reduction objectively in neuropathological specimens with quantitative measures. This may be of use for clinical diagnostics including brain imaging.     

Similar patterns of cognitive deficits in the preclinical phases of vascular dementia and Alzheimer's disease.

We investigated whether (1) cognitive deficits are present among persons who will be diagnosed with vascular dementia (VaD) 3 years later, and (2) the pattern of such deficits is similar to that observed in preclinical Alzheimer's disease (AD). The VaD diagnosis was a diagnosis of post-stroke dementia. Population-based samples of 15 incident VaD cases, 43 incident AD cases, and 149 normal controls were compared on tests of episodic and short-term memory, verbal fluency, and visuospatial skill. Both dementia groups showed preclinical impairment relative controls on tasks assessing episodic memory 3 years before diagnosis, and there were no differences between these groups on any cognitive measure. The existence of a preclinical phase in the present VaD cases suggests that circulatory disturbance may affect cognitive performance before the occurrence of stroke that leads to clinical VaD. These results extend previous findings of similar patterns of cognitive deficits in the early clinical phases of AD and VaD to the preclinical phases of these diseases.     

Cerebrospinal fluid pyruvate levels in Alzheimer's disease and vascular dementia

Increased amounts of CSF pyruvate and lactate were found in patients with AD and patients with vascular dementia (VaD). In the AD group, CSF pyruvate values did not show any overlap with those obtained in controls; within the VaD group, the highest values were observed in possible VaD cases. A significant correlation between the severity of dementia and these biochemical parameters was also observed in both AD and possible VaD. The similarities of CSF pyruvate patterns observed in AD and possible VaD patients implicate a neurodegenerative component in this VaD subgroup.