Prospective CT confirms differences between vascular and Alzheimer's dementia

Association evaluations of oral anticoagulants with dementia risk based on genomic and real-world data

BACKGROUND

Several observational studies have suggested that oral anticoagulants (OACs) might reduce the risk of dementia in the elderly, but the evidence is inconclusive. And the consistency of this relationship across different OAC classes and dementia subtypes is still uncertain.

METHODS

To comprehensively evaluate this association, we applied Mendelian randomization (MR) combined with pharmacovigilance analysis. MR was used to assess the associations between genetic proxies for three target genes of OACs (VKORC1, F2, and F10) and dementia, including Alzheimer's disease (AD) and vascular dementia (VaD). This genetic analysis was supplemented with real-world pharmacovigilance data, employing disproportionality analysis for more reliable causal inference.

RESULTS

Increased expression of the VKORC1 gene was strongly associated with increased risk of dementia, especially for AD (OR = 1.28, 95% CI = 1.14-1.43; p value < 0.001). Based on pharmacovigilance data, vitamin K antagonists (VKAs, inhibitors targeting VKORC1) exhibited a protective effect against dementia risk (ROR = 0.43, 95% CI = 0.28-0.67). Additional sensitivity analyses, including different MR models and cohorts, supported these results. Conversely, no strong causal associations of genetically proxied F2 and F10 target genes with dementia and its subtypes were found.

CONCLUSIONS

This study reveals that the inhibition of genetically proxied VKORC1 expression or VKAs exposure is associated with a reduced risk of Alzheimer's dementia. However, there is little evidence to support similar associations with direct oral anticoagulants (F2 inhibitors and F10 inhibitors). Further research is warranted to clinically validate our findings.

Elevated Homocysteine Level and Brain Atrophy Changes as Markers to Screen the Alzheimer Disease: Case Series

Alzheimer disease (AD) is the most common cause of dementia worldwide. Its clinical manifestations include a progressive loss of memory and other cognitive domains, as well as brain atrophy. An elevated homocysteine level (>15 µmol/L), known as hyperhomocysteinemia, is also an attributing risk factor for AD, vascular pathologies, and brain atrophy. Neuroimaging studies including T2-weighted magnetic resonance imaging scans revealed white matter hyperintensities in the periventricular and deep white matter, enlarged ventricles, widened sulci, and decreased white matter mass, which are features of aging, as well as cerebrovascular changes. This case series investigated changes in biochemical marker levels including serum homocysteine, folate, and vitamin B12, and the degree of atrophic variations in cortical-subcortical white matter in AD. The present study hypothesized that serum homocysteine levels might be used as a surrogate marker to screen for AD at an earlier stage.

The Electrophysiological Phenomenon of Alzheimer's Disease: A Psychopathology Theory

The current understanding of Alzheimer's disease (AD) is based on the Aβ and tau pathology and the resulting neuropathological changes, which are associated with manifested clinical symptoms. However, electrophysiological brain changes may provide a more expansive understanding of AD. Hence, the objective of this systematic review is to propose a theory about the electrophysiological phenomenon of Alzheimer's disease (EPAD). The review of literature resulted from an extensive search of PubMed and MEDLINE databases. One-hundred articles were purposively selected. They provided an understanding of the concepts establishing the theory of EPAD (neuropathological changes, neurochemical changes, metabolic changes, and electrophysiological brain changes). Changes in the electrophysiology of the brain are foundational to the association or interaction of the concepts. Building on Berger's Psychophysical Model, it is evident that electrophysiological brain changes occur and affect cortical areas to generate or manifest symptoms from onset and across the stages of AD, which may be prior to pathological changes. Therefore, the interaction of the concepts demonstrates how the psychopathology results from affected electrophysiology of the brain. The theory of the EPAD provides a theoretical foundation for appropriate measurements of AD without dependence on neuropathological changes. Future research is warranted to further test this theory. Ultimately, this theory contributes to existing knowledge because it shows how electrophysiological changes are useful in understanding the risk and progression of AD across the stages.

Tissue-specific sparse deconvolution for brain CT perfusion

Enhancing perfusion maps in low-dose computed tomography perfusion (CTP) for cerebrovascular disease diagnosis is a challenging task, especially for low-contrast tissue categories where infarct core and ischemic penumbra usually occur. Sparse perfusion deconvolution has been recently proposed to effectively improve the image quality and diagnostic accuracy of low-dose perfusion CT by extracting the complementary information from the high-dose perfusion maps to restore the low-dose using a joint spatio-temporal model. However the low-contrast tissue classes where infarct core and ischemic penumbra are likely to occur in cerebral perfusion CT tend to be over-smoothed, leading to loss of essential biomarkers. In this paper, we propose a tissue-specific sparse deconvolution approach to preserve the subtle perfusion information in the low-contrast tissue classes. We first build tissue-specific dictionaries from segmentations of high-dose perfusion maps using online dictionary learning, and then perform deconvolution-based hemodynamic parameters estimation for block-wise tissue segments on the low-dose CTP data. Extensive validation on clinical datasets of patients with cerebrovascular disease demonstrates the superior performance of our proposed method compared to state-of-art, and potentially improve diagnostic accuracy by increasing the differentiation between normal and ischemic tissues in the brain.

Differences in functional impairment across subtypes of dementia

BACKGROUND

Dementia is a cause of disability in later life. Despite the importance of functional status to the diagnosis of dementia, limited information exists on differences in functional limitations by dementia subtype. We conducted a cross-sectional analysis using the Aging, Demographics, and Memory Study (ADAMS) to determine the extent of functional impairment among older adults with dementia due to different etiologies.

METHODS

The ADAMS sample consisted of 856 individuals aged 71 years and older originally surveyed as part of the Health and Retirement Study. Based on a comprehensive in-person cognitive evaluation, respondents were assigned to diagnostic categories of normal cognition, cognitive impairment not demented, and demented. Dementia subtypes were grouped into three categories: vascular dementia (VaD), Alzheimer's dementia (AD), and dementia due to other etiologies. For 744 of the 856 respondents, a proxy informant completed a questionnaire asking whether the respondent had difficulty completing instrumental activities of daily living and activities of daily living (ADLs).

RESULTS

Of 744 ADAMS participants, 263 had dementia: 199 (70.5%) with AD, 42 (16.9%) with VaD, and 22 (12.6%) were demented due to other etiologies. After adjustment for demographics, chronic illnesses, and dementia severity, participants with VaD (odds ratio [OR] 5.74; 95% confidence interval [CI] 2.60-12.69) and other etiologies of dementia (OR 21.23; 95% CI 7.25-62.16) were more likely to have greater than or equal to four ADL limitations compared with those with AD.

CONCLUSIONS

VaD is associated with significantly more ADL limitations than AD. These physical limitations should be considered when designing adult day care programs, which adequately accommodate the needs of non-AD patients.

Investigational treatment for vascular cognitive impairment

Cognitive impairment of any severity associated with cerebrovascular damage is defined as vascular cognitive impairment as proposed by O'Brien. This is a heterogeneous syndrome with many subtypes, the most prevalent being vascular cognitive impairment without dementia. Neuropathological studies confirm that cerebrovascular disease and Alzheimer's disease frequently coexist. Diagnosis depends on criteria for dementia and vascular pathologies. Brain imaging is an important diagnostic tool. Although there is no approved intervention specifically for vascular cognitive impairment, general treatments (such as antiplatelet and antihypertensives) aimed at the prevention and management of stroke are used. Evidence from randomised, placebo-controlled studies of cholinesterase inhibitors for vascular dementia suggests that there may be beneficial effects for cognitive function, and clinical global impression is more favourable for the cholinesterase inhibitors compared with placebo. The effect of memantine also seems to be modest and similar to the effect that is demonstrated in patients with Alzheimer's disease. The accumulated evidence is not as comprehensive as that which exists for Alzheimer's disease. The cholinesterase inhibitors and memantine have not been extensively studied in vascular cognitive impairment without dementia. For the purposes of this review, the authors focus on interventions that have been evaluated by randomised controlled trials.

Neuroradiological findings in vascular dementia

INTRODUCTION

There are multiple diagnostic criteria for vascular dementia (VaD) that may define different populations. Utilizing the criteria of the National Institute of Neurological Disorders and Stroke and Association Internationale pour la Recherche et l'Enseignement en Neurosciences (NINDS-AIREN) has provided improved consistency in the diagnosis of VaD. The criteria include a table listing brain imaging lesions associated with VaD.

METHODS

The different neuroradiological aspects of the criteria are reviewed based on the imaging data from an ongoing large-scale clinical trial testing a new treatment for VaD. The NINDS-AIREN criteria were applied by a centralized imaging rater to determine eligibility for enrollment in 1,202 patients using brain CT or MRI.

RESULTS

Based on the above data set, the neuroradiological features that are associated with VaD and that can result from cerebral small-vessel disease with extensive leukoencephalopathy or lacunae (basal ganglia or frontal white matter), or may be the consequence of single strategically located infarcts or multiple infarcts in large-vessel territories, are illustrated. These features may also be the consequence of global cerebral hypoperfusion, intracerebral hemorrhage, or other mechanisms such as genetically determined arteriopathies.

CONCLUSION

Neuroimaging confirmation of cerebrovascular disease in VaD provides information about the topography and severity of vascular lesions. Neuroimaging may also assist with the differential diagnosis of dementia associated with normal pressure hydrocephalus, chronic subdural hematoma, arteriovenous malformation or tumoral diseases.

Progressive expression of vascular endothelial growth factor (VEGF) and angiogenesis after chronic ischemic hypoperfusion in rat

Cerebrovascular stenosis caused by arteriosclerosis induces failure of the cerebral circulation. Even if chronic cerebral hypoperfusion does not induce acute neuronal cell death, cerebral hypoperfusion may be a risk factor for neurodegenerative diseases. The purpose of this study was to determine if vasodilation, expression of VEGF, and neovascularization are homeostatic signs of cerebral circulation failure after permanent common carotid artery occlusion (CCAO) in the rat. Neuronal cell death in neocortex was observed 2 weeks after CCAO and gradually increased in a time-dependent manner. The diameter of capillaries and expression of VEGF also increased progressively after CCAO. Moreover, we observed unusual irregular angiogenic vasculature at 4 weeks. In conclusion, chronic hypoperfusion results in mechanisms to compensate for insufficiency in blood flow including vasodilation, VEGF expression, and neovascularization in the ischemic region. These results suggest that angiogenesis might be induced in adult brain through the support of growth factors and transplantation of vascular progenitor cells, and that neovascularization might be a therapeutic strategy for children and adults with diseases such as vascular dementia.

Ultrasonographic measurement of cerebral blood flow, cerebral circulation time and cerebral blood volume in vascular and Alzheimer's dementia

Vascular dementia (VD) and Alzheimer's dementia (AD) are the most common differential diagnoses in patients with cognitive impairment. Although of different etiology, small vessel disease is postulated to be present in both conditions. We investigated global cerebral blood flow (CBF), global cerebral circulation time (CCT) and global cerebral blood volume (CBV) in VD and AD patients using a multimodal ultrasound (US) approach. 20 VD and 20 AD patients were included and compared with 12 age-matched controls. Duplex US of both internal carotid and vertebral arteries was performed to measure CBF. CCT was defined as the time delay of an echo-contrast bolus arrival between the internal carotid artery and internal jugular vein using extracranial Doppler. CBV was calculated as the product of CBF and CCT. CBF was significantly lower (VD: 570 +/- 61; AD: 578 +/- 77; controls: 733 +/- 54 ml/min) and CCT significantly longer (8.8 +/- 2.6; 8.2 +/- 1.4; 6.4 +/- 0.8 s) in both patient groups compared with controls (p < 0.003). No difference in CBF and CCT was found between the two patient groups. CBV was similar in all three groups (82 +/- 20; 79 +/- 19; 78 +/- 9 ml). The equally reduced CBF and prolonged CCT in VD and AD support the hypothesis, that small vessel disease is a relevant factor in both types of dementia. The presented multimodal US approach helps to assess the extent of changes in the global cerebral hemodynamics in patients with dementia but does not allow a differentiation between VD and AD.

Cognitive performance after first ever stroke related to progression of vascular brain damage: a 2 year follow up CT scan study

BACKGROUND

Stroke is one of the most common causes of cognitive impairment in the elderly. Ischaemic brain damage (white matter lesions and silent infarcts) progresses in a substantial number of stroke patients. The aim of this study was to investigate whether the progression of ischaemic brain damage is associated with cognitive functioning after first ever stroke.

METHODS

A total of 101 stroke patients were followed up for 2 years. Neuropsychological functioning was assessed at 1, 6, 12, and 24 months after stroke. Computed tomography was performed on all patients at baseline and 2 years after stroke. Progression in white matter lesions and (silent) infarcts was recorded.

RESULTS

Patients with progressive vascular brain damage performed worse on cognitive tasks, both 1 and 24 months after stroke, yet change in cognitive functioning was not different from that of patients without progressive vascular damage. During the follow up, improvement was noticed on most cognitive domains.

CONCLUSIONS

Although patients with progressive vascular brain damage after a first stroke performed somewhat worse on cognitive tests than those without such damage, both groups showed an improved or stable performance 2 years later. Thus, there is not a simple relation between progression of ischaemic brain damage and decline in cognitive functioning after first ever stroke.

Clinical correlates of cognitive decline in vascular dementia

OBJECTIVE

To determine whether demographic data, dementia severity, functional status, whole brain volume (WBV), or subcortical hyperintensity volume (SH) predict subsequent cognitive decline in vascular dementia (VaD).

BACKGROUND

The identification of variables that accurately predict progressive cognitive decline in dementia has important clinical implications.

METHODS

A cohort of 30 patients with VaD completed neurologic and neuropsychologic examinations and magnetic resonance imaging of the brain at baseline and again after 12 months. All participants met clinical and research criteria for VaD according to standard guidelines. Change scores were computed for measures of verbal fluency, verbal learning, and visual learning. Potential correlates of cognitive change included age, education, score on the Hachinski scale, WBV, SH, and functional ability.

RESULTS

As a group, lower WBV and lower Hachinski score correlated with decline in verbal fluency and visual learning, whereas lower Hachinski score correlated with decline in verbal learning. However, when subdivided by disease type, this pattern held only for individuals with evidence of a cortical stroke at baseline. No clinical variables correlated with cognitive decline among individuals without a cortical infarction.

CONCLUSIONS

Assessment of cognitive decline in VaD should be guided by dementia subtype, with particular attention directed at severity of cerebral atrophy rather than classic symptoms of infarction.

Donepezil for vascular cognitive impairment

BACKGROUND

Vascular disease is the second commonest cause of dementia after Alzheimer's disease. There are difficulties in classifying patients with this type of cognitive impairment owing to varied clinical presentation and different types of arterial disease. There is some degree of overlap in the neuropathology of Alzheimer's and vascular dementia. Deficient cholinergic neurotransmission, a characteristic of Alzheimer's disease, has been postulated to contribute to the cognitive impairment of vascular disease of the brain. Cholinesterase inhibitors, such as donepezil, may therefore be a rational treatment.

OBJECTIVES

To assess the clinical efficacy and tolerability of donepezil on cognitive function, clinical global impression, activities of daily living and social functioning of people with vascular cognitive impairment.

SEARCH STRATEGY

Relevant randomized controlled trials were identified from a search of the Cochrane Dementia and Cognitive Improvement Group Specialized Register on 21 July 2003 using the terms donepezil, E2020 and Aricept. This Register consists of records from all major healthcare databases and many ongoing trials databases. Unpublished trials were requested from the drug company Eisai Inc and they provided us with the required data.

SELECTION CRITERIA

All unconfounded randomized double-blind trials comparing donepezil with placebo were eligible for inclusion. Trials using combinations of donepezil with other pharmacological interventions were excluded.

DATA COLLECTION AND ANALYSIS

Both reviewers assessed studies against the criteria for inclusion and extracted data. Data were pooled where appropriate, and weighted mean differences or Peto odds ratios with 95% confidence intervals calculated. Intention-to-treat analysis was undertaken when possible.

MAIN RESULTS

Two large-scale, randomized, double-blind, parallel-group controlled trials were identified for inclusion. A total of 1219 people with mild to moderate cognitive decline due to probable or possible vascular dementia (according to the NINCDS/AIREN criteria and the Hachinski Ischemia Scale) were recruited. Donepezil, at doses of 5 or 10 mg a day was compared with placebo for 24 weeks. For each outcome measure, mean change from baseline at weeks 12 and 24, using a last observation carried forward analysis, was calculated. Cognitive function: The donepezil groups showed statistically significantly better performance than the placebo groups on the cognitive subscale of the Alzheimer's Disease Assessment Scale (ADAS-Cog) at 12 and 24 weeks. The donepezil groups produced statistically significantly better scores than the placebo groups on the Mini-Mental State Examination (MMSE) at 12 and 24 weeks. Global function: The sum of the boxes of the Clinical Dementia Rating (CDR-SB) showed at 24 weeks a statistically significant benefit of 10 mg donepezil daily over both placebo and a 5 mg daily dosage. The Clinician's Interview-Based Impression of Change-plus version (CIBIC-plus) showed improved global function of participants taking 5 mg of donepezil daily compared with the placebo group but this was not seen in the higher dose group. Activities of daily living and social behaviour: On the Instrumental Activity of Daily Living (IADL) scale, there was no statistically significant difference between the groups taking donepezil 5mg per day donepezil and placebo, but the group taking 10 mg of donepezil a day showed benefit compared with placebo There were statistically significant benefit for donepezil at either dosage compared with placebo on the Alzheimer's Disease Functional Assessment and Change Scale (ADFACS). Tolerability and adverse effects: Broad range of adverse events were reported in the studies and data confirmed that donepezil was well tolerated, and most of the side effects were transient and were resolved by stopping the medication. Some of these events, especially nausea, diarrhoea, anorexia and cramp appeared more frequently on the 10 mg dose where there was a statistically significant difference compared with placebo. Drop-out: The drop-out rate was similar between the groups, 84.2% (330) patients completed the studies. The withdrawal rate was low and due mainly to side effects.

REVIEWER'S CONCLUSIONS

Evidence from the available studies support the benefit of donepezil in improving cognition function, clinical global impression and activities of daily living in patients with probable or possible mild to moderate vascular cognitive impairment after 6 months treatment. Extending studies for longer periods would be desirable to establish the efficacy of donepezil in patients with advanced stages of cognitive impairment. Moreover, there is an urgent need for establishing specific clinical diagnostic criteria and rating scales for vascular cognitive impairment.

Cognitive and functional decline in African Americans with VaD, AD, and stroke without dementia

OBJECTIVE

To compare the rates of cognitive and functional decline in African American patients diagnosed at baseline with vascular dementia (VaD) (n = 79), AD (n = 113), or stroke without dementia (SWD) (n = 56) and followed for up to 7 years with annual neuropsychological and other examinations.

METHODS

Study patients were diagnosed using established criteria for dementia and were administered cognitive screening, functional screening, and neuropsychological measures. Baseline dementia severity was rated using the Clinical Dementia Rating Scale. Random effects modeling was used to examine rates of decline and to compare the rates of decline in the three groups.

RESULTS

Both patients with VaD and those with AD showed significant cognitive and functional decline during follow-up; patients with VaD declined at a slower rate than patients with AD; and patients diagnosed with SWD at baseline did not show cognitive or functional decline during follow-up.

CONCLUSIONS

Patients with VaD decline at a slower rate than patients with AD. Patients who do not meet criteria for dementia soon after stroke may not be at high risk for developing dementia. Future studies are needed to follow VaD patients with longitudinal, specialized MR protocols, concurrent neuropsychological examinations, and neuropathologic examination to determine possible neuroimaging predictors of progressive cognitive and functional decline and to assess the contribution of Alzheimer's pathology to decline in patients diagnosed with VaD.

Caracterização clínica da demência vascular: avaliação retrospectiva de uma amostra de pacientes ambulatoriais

OBJETIVO: analisar as características clínicas e as condições mórbidas (CM) associados em uma amostra de pacientes com demência vascular (DV). MÉTODOS: foram estudados retrospectivamente 25 pacientes com diagnóstico de DV, estabelecidos com base critérios do grupo State of California Alzheimer´s Disease Diagnostic and Treatment Centers (ADDTC). Os dados clínicos e de neuroimagem e os exames laboratoriais foram computados para caracterização da amostra. RESULTADOS: a média da faixa etária foi de 68,7 ± 14,6 anos (64,0% homens), com escolaridade média de 5,2 ± 4,4 anos. A instalação súbita do quadro foi observada em 48,0% dos pacientes e a evolução em degraus e o curso flutuante, em 4,0% e 16,0% dos casos, respectivamente. Apresentavam déficit neurológico focal como sintoma inicial 48,0%, sendo constatado déficit ao exame em 80,0%. As principais CM foram: hipertensão arterial sistêmica (92,0%); hipercolesterolemia (64,0%); insuficiência coronariana (40,0%); tabagismo (40,0%); hipertrigliceridemia (36,0%); diabete melito (32,0%); doença de Chagas (8,0%). CONCLUSÕES: observou-se forte correlação entre DV e hipertensão e hipercolesterolemia. A presença de dois pacientes com doença de Chagas sugere que esta doença possa constituir possível fator de risco regional.

Cardiovascular and other risk factors for Alzheimer's disease and vascular dementia

Factors accelerating cerebral degenerative changes represent potentially modifiable risks for cognitive decline. Putative risks accelerating subtle cognitive decline and dementia were correlated with repeated measures of cerebral atrophy, CT densitometry, perfusions, and cognitive testing among 224 neurologically and cognitively normative aging volunteers. After age 60, cerebral atrophy, ventricular enlargement, polioaraiosis, and leukoaraiosis geometrically increased as perfusions declined. Risks accelerating perfusional decline, cerebral atrophy, polioaraiosis, and leukoaraiosis were: transient ischemic attacks (TIAs), hypertension, smoking, hyperlipidemia, male gender. At age 71.5 +/- 11.9, subtle cognitive decline began, accelerated by TIAs, hypertension, and heart disease. Leukoaraiosis began before cognitive decline. TIAs, hypertension, and hyperlipidemia correlated with vascular dementias. Excessive cortical perfusional decreases and cerebral atrophy correlated with cognitive decline. Family history of neurodegenerative disease correlated with Alzheimer's disease. We concluded that TIAs, hypertension, hyperlipidemia, smoking, and male gender accelerate cerebral degenerative changes, cognitive decline, and dementia.

Ameliorative effect of tacrine on spatial memory deficit in chronic two-vessel occluded rats is reversible and mediated by muscarinic M1 receptor stimulation

Our previous study demonstrated that permanent two-vessel occlusion (2VO)-induced working memory deficit was improved by daily administration of tacrine, a cholinesterase inhibitor. In this study, we investigated the mechanism underlying the effects of tacrine in 2VO rats using the eight-arm radial maze task. Daily administration of tacrine (0.1 or 0.3 mg/kg i.p.) started 5 weeks after the 2VO operation significantly improved the maze performance. In the delay-interposition task, a significant impairment of maze performance was observed in the tacrine (0.3 mg/kg, i.p.)-treated rats at a delay of 90 min but not delays of 5 or 30 min. Sham-operated rats were not affected by delay. After leaving animals with no further treatment for 4 weeks, the tacrine-pretreated 2VO rats showed significantly impaired performance compared to the sham-operated control animals. However, the performance of the tacrine-pretreated 2VO rats was significantly improved by restarting the daily administration of tacrine (0.3 mg/kg, i.p.). The effect of tacrine was reversed by the muscarinic antagonist scopolamine and the selective M1 antagonist pirenzepine. Moreover, a microdialysis study revealed that tacrine (1 or 3 mg/kg, i.p.) increased the extracellular acetylcholine (ACh) level for a period of over 3 h in the cerebral cortex of 2VO rats. These findings suggest that the ameliorative effect of tacrine on the spatial memory deficit in 2VO rats is reversible and may be mediated by stimulating the muscarinic M1 receptor via elevation of the extracellular ACh level in the brain.

Risk factors for cerebral hypoperfusion, mild cognitive impairment, and dementia

Putative risk factors accelerating mild cognitive decline and dementia were correlated with repeated measures of cerebral atrophy, CT, densitometry, perfusions, and cognitive testing among neurologically and cognitively normative aging volunteers. A total of 224 normative subjects at increased risk for cognitive decline were admitted to the study. Mean entry age was 59.5 +/- 15.8 years. Mean follow-up is 5.8 +/- 3.3 years. At follow-up, 22 developed mild cognitive impairment (41 CCSE >/= -3), 19 became demented-8 with Vascular type (VAD), 11 with Alzheimer's type (DAT)-and 183 remain cognitively unchanged. Cerebral atrophy, tissue densities, and perfusions were measured by Xe-CT. After age 60, cerebral atrophy, ventricular enlargement, and polio- and leuko-araiosis geometrically increased as perfusions declined. Risk factors accelerating perfusional decline, cerebral atrophy, polio-araiosis, and leuko-araiosis were: transient ischemic attacks (TIAs), hypertension, smoking, hyperlipidemia, and male gender. At age 71.5 +/- 11.9, mild cognitive impairment began accelerated by TIAs, hypertension and heart disease. Leuko-araiosis began before cognitive decline. TIAs, hypertension, and hyperlipidemia correlated with VAD. Excessive cortical perfusional decrease, gray and white matter hypodensities, and cerebral atrophy correlate with cognitive decline.

Risk factors accelerating cerebral degenerative changes, cognitive decline and dementia

OBJECTIVES

Factors accelerating cerebral degenerative changes represent potentially modifiable risks for cognitive decline. Putative risk factors accelerating subtle cognitive decline and dementia were correlated with repeated measures of cerebral atrophy, CT densitometry, perfusions and cognitive testing among neurologically and cognitively normative ageing volunteers.

METHODS

Two hundred and twenty-four normative subjects at increased risk for cognitive decline were admitted to the study. Mean entry age was 59. 5+/-15.8 years. Mean follow-up is 4.3+/-3.1 years. At follow-up, 22 developed subtle cognitive decline (deltaCCSE>/=-3), 19 became demented, eight with vascular type (VAD) and 11 with Alzheimer's type (DAT) and 183 remain cognitively unchanged. Standardized questionnaires, medical, neuropsychological, neurological and blood work examinations were obtained. Cerebral atrophy, tissue densities and perfusions were measured by xenon-enhanced CT.

RESULTS

After age 60, cerebral atrophy, ventricular enlargement, polio- and leuko-araiosis geometrically increased as perfusions declined. Risk factors accelerating perfusional decline, cerebral atrophy, polio-araiosis and leuko-araiosis (thinning of grey-white matter densities) were: transient ischaemic attacks (TIAs), hypertension, smoking, hyperlipidemia, male gender. At age 71.5+/-11.9, subtle cognitive decline began, accelerated by TIAs, hypertension and heart disease. Leuko-araiosis began before cognitive decline. TIAs, hypertension and hyperlipidemia correlated with VAD. Excessive cortical perfusional decreases and cerebral atrophy correlated with cognitive decline. Family history of neurodegenerative disease correlated with DAT.

CONCLUSION

TIAs, hypertension, hyperlipidemia, smoking and male gender accelerate cerebral degenerative changes, cognitive decline and dementia.

Vasodilator responses to acetazolamide tested in subtypes of vascular dementia

OBJECTIVES

Thirty seven vascular dementia (VAD) patients were categorized into eight subtypes based on clinical, radiological, and pathogenetic features. Cerebral vasodilator responses to acetazolamide were then compared with age-matched normal controls and stroke patients without dementia.

METHODS

VAD results were compared with 42 normals and 19 cognitively intact stroke patients. Regional cerebral vasodilator responses were quantitated utilizing xenon contrasted computed tomography measures of local cerebral blood flow (LCBF) before and after oral administration of acetazolamide. LCBF changes (DeltaLCBF) before and after acetazolamide were calculated within cortical and subcortical, gray and white matter. Clinical VAD subtypes were: type 1, multi-infarct dementia (MID); type 2, strategically placed infarcts; type 3, subcortical lacunar infarcts; type 4, Binswanger's subcortical arteriosclerotic leukoencephalopathy; type 5, subcortical infarctions due to cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), inflammatory angitis, or antiphospholipid antibodies; type 6, admixtures of above types; type 7, cerebral hemorrhagic lesions; and type 8, VAD combined with Alzheimer's disease (DAT). The group with subcortical VAD comprised types 3-5. The group with cortical VAD comprised the remainder (types 1, 2, and 6-8). Cerebral vasodilator responses were also compared between these two main groups.

RESULTS

Cerebral vasodilator responses identified differences between the two main groups of VAD patients, those with cortical and those with subcortical dementia. Leukoaraiosis was measurably greater in subcortical VAD compared with cortical VAD. Among subcortical VAD patients, cortical LCBF increases after administration of acetazolamide were greater compared with cortical VAD and with normal controls.

CONCLUSIONS

Cognitive impairments in subcortical VAD are attributable to cortical disconnection syndromes. This concept is supported by reduced perfusion in deactivated cortex. In patients with subcortical VAD, deactivated cortical LCBF becomes promptly activated by acetazolamide resulting in marked cortical LCBF increases. Leukoaraiosis is greater among VAD patients and leukoaraiosis contributes to cortical disconnections, confirmed by excessive cortical vasodilator responses to acetazolamide.

Dementias that present with and without posterior cortical features: an important clinical distinction

There are distinct qualitative differences between the dementias that present with and without posterior cortical features. These can be utilized in dementia assessment. This paper reviews the validity and potential utility of a dichotomy based on generalized cortical (Type 1) versus isolated frontal system pathology (Type 2). These syndromes are associated with distinct differentials and problem behaviors. They may also result in different caregiving burdens or treatment responses. Alzheimer's disease (AD) is by far the most common cause of the Type 1 syndrome. Type 2 presentations select for potentially reversible non-AD conditions. Common cognitive screening instruments are insensitive to Type 2 cases. However, the Type 1/Type 2 distinction can be made reliably using qualitative clinical rating scales. We will review these instruments and discuss their application in clinical settings.

Normal human aging: factors contributing to cerebral atrophy

Factors that accelerate rates of 'normal' age-related cerebral atrophic and degenerative changes are important because they may predispose to cognitive declines. To determine characteristic patterns of normal aging, risk factors were correlated with serial neurological-neuropsychological examinations, CT measures of progressive cerebral atrophy, local tissue hypodensities, or perfusional declines. Both cross-sectional and longitudinal designs were utilized. Ninety-four cognitively and neurologically normal aging volunteers, 15 with a history of transient ischemic attacks (TIAs), were followed for mean intervals of 3.0+/-2.1 years. Results indicated that: (1) after age 60, cerebral atrophy, polio- and leuko-araiosis doubled and cerebral perfusion decreased, with marked individual variations; (2) risk factors independently accelerating cerebral atrophy and cortico-subcortical perfusional declines included TIAs, hypertension, smoking, hyperlipidemia, excessive alcohol consumption and male gender; (3) progressive leuko-araiosis correlated directly with cortical atrophy and cortical perfusional declines. We posit that: (1) cerebral atrophy and degenerative changes result from neuronal shrinkage and/or loss, which are accelerated by TIAs, hypertension, smoking, hyperlipidemia, excessive alcohol consumption and male gender; (2) accelerated cerebral atrophic and degenerative changes identified by neuroimaging should be considered as markers for depleted neuronal synaptic reserves, which predispose to cognitive declines. Interventions available for controlling some of these risk factors include control of TIAs, hypertension, and hyperlipidemia, as well as tobacco and alcohol withdrawal.

Vascular dementia: still a debatable entity?

Vascular dementia (VAD) is currently considered to be the second most common cause of dementia in Europe and the USA, second to dementia of the Alzheimer's type (DAT). However, in Asia and many developing countries the incidence of VAD exceeds that of DAT. The positive clinical diagnostic workup for VAD requires six steps: (1) clear-cut quantitative assessment of cognitive deficits utilizing standard neuropsychological tests to establish and quantify the dementia syndrome and rule out pseudo-dementia OF depression; (2) ascertaining the presence of risk factors for stroke; (3) identifying cerebral vascular lesions by neuroimaging (MRI, Iodine or Xenon contrasted CT, PET and SPECT); (4) exclusion of other causes of dementia; (5) differential diagnosis of possible, probable or definite VAD versus DAT and ascertaining when there are mixtures of the two; and (6) temporal identification of causality between onset and progression of the dementia with identified cerebral vascular lesions. There are eight subtypes of VAD: (1) multi-infarct dementias. These are due to large cerebral emboli, and are usually readily identifiable; (2) strategically placed infarctions causing dementia; (3) multiple subcortical lacunar lesions. Patients with these develop VAD at least five to twenty-five times more frequently than those in age-matched general population samples; (4) Binswanger's disease (arteriosclerotic subcortical leuko-encephalopathy). This form is rare. Neuroimaging confirms the diagnosis during life but the diagnosis can not be made by neuroimaging alone; (5) mixtures of two or more of above VAD subtypes; (6) hemorrhagic lesions causing dementia; (7) subcortical dementias due to cerebral autosomally dominant arteriolopathy with subcortical infarcts and leuko-encephalopathy (CADASIL), or to familial amyloid angiopathies and coagulopathies all of which present with multiple subcortical lacunar lesions similar to Binswanger's disease; (8) mixtures of DAT and VAD. The clinical significance of leukoaraiosis and its suspected relationships to VAD remains to be better established. The presence of ischemic infarctions, single or multiple large or multiple small (lacunar) by neuroimaging are necessary for the diagnosis of VAD, but identifying their presence, by neuroimaging alone, does not permit the diagnosis of dementia which can only be established by neuropsychological assessments. VAD is a clinical entity, identifiable in at least 30-70% of patients after strokes but mechanisms responsible for the cognitive impairments are complex. Some of these mechanisms are incompletely understood but provide subjects for important future research.

Quantitative computed tomography and magnetic resonance imaging in aging and Alzheimer's disease. A review

In recent aging research, quantitative techniques have been used to overcome limitations of qualitative interpretation of magnetic resonance and computed tomographic imaging. The purpose of this review is to summarize imaging results emphasizing quantitative studies using these two modalities in human aging. Magnetic resonance spectroscopy is viewed as an extension of imaging, and results of in vivo spectroscopic studies are included. Because Alzheimer's disease (AD) is closely related to aging, a discussion of quantitative imaging techniques that may distinguish normal elderly from patients with AD is included.