[Vascular dementias]

Abstract

Cerebrovascular disorders are the second most frequent cause of dementia in late life next to Alzheimer's disease. A recent community-based autopsy study has demonstrated that relevant cerebrovascular changes are much more prevalent in individuals aged 70+ years than previously assumed. Furthermore, the combination between cerebrovascular lesions and Alzheimer-type pathology is the most common neuropathological finding in elderly patients with dementia. There is still some uncertainty about which types of cerebrovascular changes are most likely to cause cognitive impairment including dementia and which pathogenetic mechanisms are involved. Without doubt, however, the vascular dementias are a heterogeneous group of diseases in terms of etiology, histopathology, and clinical appearance. According to the vessel calibres and perfusion territories that are preferentially affected a distinction is commonly made between the frequent subcortical small-vessel disease and the rare cortical large-vessel disease. With these morphological subtypes three major clinical variants are associated: dementia due to subcortical lacunes and white matter changes including Binswanger's disease, multi-infarct-dementia, and dementia due to singular strategic infarcts. In most cases of dementia of cerebrovascular origin the pattern of intellectual impairment is frontal or subcortical, in contrast to the typical cortical presentation of Alzheimer's disease. Deterioration of executive function and attention as well as changes in personality, rather than memory loss, are the predominant symptoms. Therefore the current diagnostic criteria for dementia are poorly suited for the detection of vascular dementias. None of the criteria that have been specifically proposed for the diagnosis of vascular dementias provide clear guidelines for evaluating the causal relationship between cerebrovascular lesions and psychopathological findings. Further research will reveal whether clinical diagnosis can be improved by taking into account the heterogeneity of cerebrovascular diseases. A large proportion of dementias of cerebrovascular origin may be preventable by treating the risk-factors for stroke. Once significant cognitive impairment has occurred, however, there is no established pharmacological treatment for the vascular dementias to date. Only recently results of placebo-controlled clinical trials have become available showing that cholinergic treatment strategies are effective in vascular dementia and in dementia due to combined vascular and neurodegenerative pathologies.