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What is vascular dementia?
1Department of Psychiatry and Psychotherapy, Technische Universität München, Munich, Germany.
Insights
Cerebrovascular disease (CVD) can cause vascular dementia (VaD) through various mechanisms, including cortical lesions and white matter damage. Distinguishing VaD from other dementias requires understanding its diverse pathological and pathogenetic pathways.
Area of Science:
- Neurology
- Geriatrics
- Pathology
Background:
- Cerebrovascular disease (CVD) and dementia frequently co-occur in elderly individuals.
- Traditional dementia definitions focused on intellectual decline, while revised definitions emphasize global deficits and impact on activities of daily living (ADL).
- Applying revised dementia definitions to CVD presents challenges due to focal lesions and physical symptoms complicating ADL assessment.
Purpose of the Study:
- To explore the relationship between cerebrovascular disease (CVD) and dementia, specifically vascular dementia (VaD).
- To elucidate the pathogenetic mechanisms by which CVD can lead to global cognitive impairment.
- To highlight the need for distinguishing distinct VaD syndromes.
Main Methods:
- Review of existing literature on cerebrovascular disease and dementia.
- Analysis of pathogenetic mechanisms linking vascular lesions to cognitive deficits.
- Comparison of neurobehavioural symptoms in CVD with those in Alzheimer's disease.
Main Results:
- Focal cortical lesions in CVD cause location-specific deficits, not typically global intellectual decline.
- Subcortical lesions and white matter damage are common in CVD, leading to distinct neurobehavioural symptoms.
- Mechanisms like accumulated ischemic lesions, strategic infarcts, and white matter disconnection can cause global cognitive impairment and meet VaD criteria.
Conclusions:
- Vascular dementia (VaD) arises from diverse etiological factors, pathological changes, and pathogenetic mechanisms.
- Distinct VaD syndromes need to be identified to improve diagnosis and treatment.
- Further research is necessary to validate the concept of distinct VaD syndromes and their clinical utility.
Abstract:
Cerebrovascular disease (CVD) and dementia frequently coexist in elderly patients. The question of whether the CVD causes the dementia depends on how 'dementia' is defined. Traditional definitions specified that dementia involved a decline in intellectual ability as a core feature. However, revised definitions have since stipulated two key elements: 1) a global rather than focal neurobehavioural deficit and 2) impairment in activities of daily living (ADL). When applied to CVD, these latter concepts of dementia raise difficulty: Focal cerebrovascular lesions in the cortex generate location-specific neurobehavioural deficits that are part of the dementia syndrome, but, even in combination, do not represent a global intellectual decline. Most cerebrovascular lesions are associated with physical symptoms that make it difficult to evaluate whether cognitive impairments have an independent impact on ADL. The majority of neurobehavioural symptoms in CVD are caused by small-vessel-type subcortical lesions and are dissimilar to those seen in Alzheimer's disease. There are several pathogenetic mechanisms, however, by which large-vessel or small-vessel CVD can cause global cognitive and intellectual impairments, allowing a diagnosis of vascular dementia (VaD): An accumulation of ischaemic lesions in the cortex may produce global intellectual impairment, particularly if they affect important areas of the brain. Single small infarcts, or haemorrhages in strategic subcortical locations, may interfere with specific circuits connecting the prefrontal cortex to the basal ganglia, or with nonspecific thalamocortical projections. This may generate combinations of executive dysfunction, personality change or apathy, which are associated with hypoperfusion and hypometabolism predominantly in frontal cortical areas. Extensive white matter lesions probably affect cognitive function through a loss of axons, producing a functional disconnection of the cortex. This can manifest as significant reductions in blood flow and metabolism in frontal, temporal and parietal cortical areas, which do not show any structural damage. Given the diversity of aetiological factors, pathological changes and pathogenetic mechanisms associated with VaD, several distinct syndromes must be distinguished. Further study is needed to demonstrate that this emerging concept can improve diagnosis, guide treatment and stimulate research.