Chapter 2 Subcortical Ischemic Cerebrovascular Dementia

[Cognitive impairment in patients with arterial hypertension]

Arterial hypertension (AH) is a leading risk factor for cardiovascular diseases including cerebrovascular complications. Strokes and/or vascular cognitive impairment (VCI) are considered as a clinical sign of brain damage as a target organ in hypertension. To identify and assess the severity of VCI, patients with hypertension should undergo a neuropsychological assessment. Neuroimaging confirm the vascular origin of cognitive impairment. Patient management should include antihypertensive therapy along with neuroprotection. Among different neuroprotective therapy, ethylmethylhydroxypyridine succinate (mexidol) is one of medication with serious evidence of clinical efficacy.

Habituation of Somatosensory Evoked Potentials in Patients with Alzheimer’s Disease and Those with Vascular Dementia

Background and Objectives: The most prevalent dementia are Alzheimer’s disease and vascular dementia. There is evidence that cortical synaptic function may differ in these two conditions. Habituation of cortical responses to repeated stimuli is a well-preserved phenomenon in a normal brain cortex, related to an underlying mechanism of synaptic efficacy regulation. Lack of habituation represents a marker of synaptic dysfunction. The purpose of this study was to assess the habituation of somatosensory evoked potentials (SEPs) in 29 patients affected by mild-to-moderate Alzheimer’s disease (AD-type) or vascular (VD-type) dementia. Materials and Methods: All patients underwent a clinical history interview, neuropsychological evaluation, and neuroimaging examination. SEPs were elicited by electrical stimulation of the right median nerve at the wrist. Six-hundred stimuli were delivered, and cortical responses divided in three blocks of 200. Habituation was calculated by measuring changes of N20 amplitude from block 1 to block 3. SEP variables recorded in patients were compared with those recorded in 15 age- and gender-matched healthy volunteers. Results: SEP recordings showed similar N20 amplitudes in AD-type and VD-type patients in block 1, that were higher than those recorded in controls. N20 amplitude decreased from block 1 to block 3 (habituation) in normal subjects and in VD-type patients, whereas in AD-type patients it remained unchanged (lack of habituation). Conclusions: The findings suggest that neurophysiologic mechanisms of synaptic efficacy that underneath habituation are impaired in patients with AD-type dementia but not in patients with VD-type dementia. SEPs habituation may contribute to early distinction of Alzheimer’s disease vs. vascular dementia.

The Role of Cerebrovascular Disease in Amyloid Deposition

BACKGROUND

Some patients clinically diagnosed with subcortical vascular cognitive impairment (SVCI) have co-morbidity with AD pathology.

OBJECTIVE

We investigated topographical differences in amyloid burden between SVCI and Alzheimer's disease type cognitive impairment (ADCI) using [11C] Pittsburgh compound B (PiB) positron emission tomography (PET). The purpose of this study was to investigate the role of cerebrovascular disease (CVD) in amyloid deposition.

METHODS

We recruited 44 patients with SVCI and 44 patients with ADCI (amnestic mild cognitive impairment or Alzheimer's disease) with absent or minimal white matter hyperintensities, all with PiB-positive PET scans [PiB+]. As controls, we included 13 participants with normal cognition and PiB-negative scans. We divided the SVCI and ADCI patients into three groups according to global PiB retention ratio of SVCI, and then compared the tertiles in terms of the distribution of PiB retention using statistical parametric mapping analyses. Lobar to global PiB retention ratio and asymmetry indices were also compared between SVCI and ADCI groupsResults: Compared to PiB+ ADCI patients, PiB+ SVCI patients exhibited: 1) increased left-right asymmetry, and increased anterior-posterior difference; and 2) increased PiB retention in the parietal cortex, the occipital cortex and the precuneus-posterior cingulate cortex. In contrast, ADCI patients showed increased PiB retention in the striatum. When stratified by level of PiB retention, each group showed different characteristics.

CONCLUSION

Our results showed that the distribution of amyloid deposition differed between patients with PiB+ SVCI and ADCI. These suggest that CVD contribute to and alter the known progression pattern in amyloid deposition in Alzheimer's disease.

Pharmacological modulation of dietary lipid-induced cerebral capillary dysfunction: Considerations for reducing risk for Alzheimer's disease

An increasing body of evidence suggests that cerebrovascular dysfunction and microvessel disease precede the evolution of hallmark pathological features that characterise Alzheimer's disease (AD), consistent with a causal association for onset or progression. Recent studies, principally in genetically unmanipulated animal models, suggest that chronic ingestion of diets enriched in saturated fats and cholesterol may compromise blood-brain barrier (BBB) integrity resulting in inappropriate blood-to-brain extravasation of plasma proteins, including lipid macromolecules that may be enriched in amyloid-β (Aβ). Brain parenchymal retention of blood proteins and lipoprotein bound Aβ is associated with heightened neurovascular inflammation, altered redox homeostasis and nitric oxide (NO) metabolism. Therefore, it is a reasonable proposition that lipid-lowering agents may positively modulate BBB integrity and by extension attenuate risk or progression of AD. In addition to their robust lipid lowering properties, reported beneficial effects of lipid-lowering agents were attributed to their pleiotropic properties via modulation of inflammation, oxidative stress, NO and Aβ metabolism. The review is a contemporary consideration of a complex body of literature intended to synthesise focussed consideration of mechanisms central to regulation of BBB function and integrity. Emphasis is given to dietary fat driven significant epidemiological evidence consistent with heightened risk amongst populations consuming greater amounts of saturated fats and cholesterol. In addition, potential neurovascular benefits associated with the use of hypolipidemic statins, probucol and fenofibrate are also presented in the context of lipid-lowering and pleiotropic properties.

Exercise Capacity and Aging

A growing body of literature suggests that regular exercise among older individuals regardless of the degree of frailty, with or without underlying chronic disease, may attenuate the consequences of age-related changes on exercise capacity. The purpose of this article is to review the effects of age-related changes on exercise capacity and the benefits of prescribing exercise to older persons.

Pathogenesis and treatment of vascular cognitive impairment

SUMMARY 

Vascular cognitive impairment (VCI) defines a continuum of disorders ranging from mild cognitive impairment to full-blown dementia, attributable to cerebrovascular causes. Major morphological types – multi-infarct encephalopathy, strategic infarct type, subcortical arteriosclerotic leukoencephalopathy, multilacunar state, postischemic encephalopathy – result from systemic, cardiac and local large or small vessel disease. Cognitive decline is commonly caused by widespread small cerebrovascular lesions (CVLs) affecting regions/networks essential for cognition, memory and behavior. CVLs often coexist with Alzheimer-type and other pathologies, which interact in promoting dementia, but in many nondemented elderly individuals, mixed brain pathologies are also present. Due to the high variability of CVLs, no validated clinical and neuropathological criteria for VCI are available. Cholinesterase inhibitors and memantine produce small cognitive improvement but without essential effect. Antihypertensive treatment, cardiovascular control and lifestyle modifications reducing vascular risk factors are essential. Given its growing health, social and economic burden, prevention and treatment of VCI are a major challenge of neuroscience.

The link between cardiovascular risk, Alzheimer's disease, and mild cognitive impairment: support from recent functional neuroimaging studies

OBJECTIVE

To review functional neuroimaging studies about the relationship between cardiovascular risk factors (CVRFs), Alzheimer's disease (AD), and mild cognitive impairment (MCI).

METHODS

We performed a comprehensive literature search to identify articles in the neuroimaging field addressing CVRF in AD and MCI. We included studies that used positron emission tomography (PET), single photon emission computerized tomography (SPECT), or functional magnetic resonance imaging (fMRI).

RESULTS

CVRFs have been considered risk factors for cognitive decline, MCI, and AD. Patterns of AD-like changes in brain function have been found in association with several CVRFs (both regarding individual risk factors and also composite CVRF measures). In vivo assessment of AD-related pathology with amyloid imaging techniques provided further evidence linking CVRFs and AD, but there is still limited information resulting from this new technology.

CONCLUSION

There is a large body of evidence from functional neuroimaging studies supporting the hypothesis that CVRFs may play a causal role in the pathophysiology of AD. A major limitation of most studies is their cross-sectional design; future longitudinal studies using multiple imaging modalities are expected to better document changes in CVRF-related brain function patterns and provide a clearer picture of the complex relationship between aging, CVRFs, and AD.

Greater body mass index is associated with poorer cognitive functioning in male heart failure patients

BACKGROUND

Heart failure (HF) and obesity are associated with cognitive impairment. However, few studies have investigated the relationship between adiposity and cognitive functioning in HF for each sex, despite observed sex differences in HF prognosis. We tested the hypothesis that greater body mass index (BMI) would be associated with poorer cognitive functioning, especially in men, in sex-stratified analyses.

METHODS AND RESULTS

Participants were 231 HF patients (34% female, 24% nonwhite, average age 68.7 ± 7.3 years). Height and weight were used to compute BMI. A neuropsychology battery tested global cognitive function, memory, attention, and executive function. Composites were created using averages of age-adjusted scaled scores. Regressions adjusting for demographic and medical factors were conducted. The sample was predominantly overweight/obese (76.2%). For men, greater BMI predicted poorer attention (ΔR(2) = 0.03; β = -0.18; P = .01) and executive function (ΔR(2) = 0.02; β = -0.13; P = .04); these effects were largely driven by men with severe obesity (BMI ≥40 kg/m(2)). BMI did not predict memory (P = .69) or global cognitive functioning (P = .08). In women, greater BMI was not associated with any cognitive variable (all P ≥ .09).

DISCUSSION

Higher BMI was associated with poorer attention and executive function in male HF patients, especially those with severe obesity. These patients may therefore have more difficulties with the HF treatment regimen and may have poorer outcomes.

Cardiovascular risk in cognitively preserved elderlies is associated with glucose hypometabolism in the posterior cingulate cortex and precuneus regardless of brain atrophy and apolipoprotein gene variations

Cardiovascular risk factors (CVRF) possibly contribute to the emergence of Alzheimer's disease (AD). Fluorodeoxyglucose-positron emission tomography (FDG-PET) has been widely used to demonstrate specific patterns of reduced cerebral metabolic rates of glucose (CMRgl) in subjects with AD and in non-demented carriers of the apolipoprotein ε4 (APOE ε4) allele, the major genetic risk factor for AD. However, functional neuroimaging studies investigating the impact of CVRF on cerebral metabolism have been scarce to date. The present FDG-PET study investigated 59 cognitively preserved elderlies divided into three groups according to their cardiovascular risk based on the Framingham 10-year risk Coronary Heart Disease Risk Profile (low-, medium-, and high-risk) to examine whether different levels of CVRF would be associated with reduced CMRgl, involving the same brain regions affected in early stages of AD. Functional imaging data were corrected for partial volume effects to avoid confounding effects due to regional brain atrophy, and all analyses included the presence of the APOE ε4 allele as a confounding covariate. Significant cerebral metabolism reductions were detected in the high-risk group when compared to the low-risk group in the left precuneus and posterior cingulate gyrus. This suggests that findings of brain hypometabolism similar to those seen in subjects with AD can be detected in association with the severity of cardiovascular risk in cognitively preserved individuals. Thus, a greater knowledge about how such factors influence brain functioning in healthy subjects over time may provide important insigths for the future development of strategies aimed at delaying or preventing the vascular-related triggering of pathologic brain changes in the AD.

Diagnosis of vascular cognitive impairment and its main categories

OBJECTIVE

A review of current criteria for the diagnosis of categories related with vascular cognitive impairment, in particular the nomenclature, diagnostic criteria, and differential clinical-radiological findings.

DEVELOPMENT

The criteria for the diagnosis of vascular cognitive impairment have evolved, but available criteria were designed basically for differentiating between vascular dementia and dementia due to Alzheimer disease, and for research purposes. Nevertheless, in clinical practice precise elements are required for: 1) Clinical diagnosis of dementia and mild cognitive impairment; 2) Clinical and neuroimaging criteria for identification of the various cerebrovascular lesions associated with cognitive dysfunction, and 3) A formulation of the aetiogenic-pathogenic relationship between cognitive impairment and cerebrovascular lesions. For this reason, a review was carried out on the diagnostic elements of vascular cognitive impairment categories, classification, and their most relevant characteristics. It highlights the characteristic for the diagnosis of multi-infarction dementia, strategic single infarct dementia, small vessel disease with dementia, mixed dementia, and vascular mild cognitive impairment.

CONCLUSIONS

Standardisation is required, by a multidisciplinary expert team, as regards nomenclature and criteria for the diagnosis of the full spectrum associated with vascular cognitive impairment and especially for vascular dementia and its categories.

Vascular diseases and old age mental disorders: an update of neuroimaging findings

PURPOSE OF REVIEW

To review neuroimaging findings that have been reported in samples of patients with cardiovascular disorders and their association with the onset of Alzheimer's disease, vascular dementia, depression and bipolar disorder in the elderly and to highlight the implications of these findings to the knowledge about the pathophysiology of psychiatric disorders in old age, as well as their potential clinical implications.

RECENT FINDINGS

Vascular risk factors, such as hypertension, diabetes, dyslipidemia, smoking habits and heart failure, have all been associated with signs of cerebrovascular dysfunction, including structural MRI findings of signal hyperintensities, lacunes and stroke and functional imaging findings of brain regional hypoperfusion and hypometabolism. Such brain abnormalities have been found to increase the risk of onset of psychiatric disorder (depression, bipolar and dementia) in old age.

SUMMARY

As vascular risk factors are potentially modifiable when detected in midlife, the early characterization of brain changes associated with the presence of cardiovascular diseases holds promise to afford clinical applications in psychiatry, providing new perspectives for the prevention of old age psychiatric disorders.

Cognitive impairment of vascular origin: neuropathology of cognitive impairment of vascular origin

The term cognitive impairment of vascular origin is used to designate global cognitive deficits as well as focal neurological deficits such as aphasia, apraxia and agnosia of vascular/circulatory origin. It has been useful for identifying early clinical and neuroradiological alterations that might permit therapeutic strategies geared to curbing the progression of cerebrovascular disease. Multi-infarct encephalopathy, infarcts in strategic areas, lacunae and lacunar status, Binswanger's encephalopathy, hippocampal sclerosis, cortical granular atrophy and watershed infarcts are common lesions. Hypertension and vascular diseases such as arteriosclerosis, small blood vessel disease, inflammatory diseases of the blood vessels, Sneddon syndrome, cerebral amyloid angiopathies, cerebral autosomic dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), and Maeda's syndrome are causative of cognitive impairment of vascular origin. Other less common causes are hereditary endotheliopathy with retinopathy, neuropathy and strokes (HERNS), cerebro-retinian vasculopathy (CRV), hereditary vascular retinopathy (HVR) (all three linked to 3p21.1-p21.3), hereditary infantile hemiparesis with arteriolar retinopathy and leukoencephalopathy (HIHRATL) (not linked to 3p21), fibromuscular dysplasia, and moya-moya disease. Lack of uniformity of clinical manifestations, the variety of vascular diseases and circulatory factors, the diverse, but often convergent, neuropathological substrates, and the common association with unrelated neurodegenerative diseases in the elderly, make it hard to assume a single clinical approach in the diagnosis and treatment of cognitive impairment of vascular origin. Rather, environmental and genetic risk factors, underlying vascular diseases, associated systemic, metabolic and neurodegenerative diseases and identification of extent and distribution of lesions with morphological and functional neuroimaging methods should be applied in every individual patient.

Prevention and Care of Stroke in Low- and Middle-Income Countries; the Need for a Public Health Perspective

Stroke is a leading public health problem, causing significant disability and premature mortality, particularly in low- and middle-income countries (LMIC). A public health strategy is required for the prevention and care of stroke in LMIC. Although specific estimates are difficult to calculate, increasing cost-effective interventions that reduce cardiovascular risk in the population can have a substantial impact on stroke burden. Public health interventions that address tobacco use, unhealthy diet (salt and transfat), and physical inactivity of the population need to be complemented with equitable stroke services. The main components of an equitable stroke service include:

• assessment and management of cardiovascular risk in primary care,

• assessment and follow-up of transient ischaemic attack (TIA) patients,

• provision of secondary prevention through a primary health care approach,

• education of the public, health care staff and patients with stroke,

• equitable access to acute stroke care and stroke rehabilitation and

• community and family engagement for support to care givers and stroke patients.

Unless services for stroke care are complemented with prevention programmes to reduce stroke risk in the population, health care costs will continue to escalate due to increasing rates of stroke.