Toward a pathological definition of vascular dementia.

To date, there are no widely accepted neuropathological criteria for vascular dementia, although creating such a standard is ranked high on the wish list of all the researchers in this field. Such criteria would make it possible to perform large multicentre clinicopathological studies and, consequently, to better understand which, how, and where vascular brain lesions lead to cognitive decline, as it is possible to do in Alzheimer's disease or Parkinson's disease. However, a major obstacle in the standardization of diagnosis is the fact that vascular brain lesions are a large group comprising heterogeneous changes that have different pathogeneses. Although it is accepted that some kinds of vascular changes cause cognitive impairment, it is not uncommon to find reports of the assumed same histological changes in control subjects. An indispensable first step in the unequivocal establishment of neuropathological criteria is to uniform the definitions used for each one of the lesions, preferably based on its pathogenesis. In the present, non-standardized state of ambiguity, a given lesion is designated by different names between and within the clinical, radiological, and pathological settings, and several definitions simply overlap. Before attempting to create new criteria, a multidisciplinary group-task is urged to identify and minimize the uncontrolled proliferation of definitions. Only then, it will be possible to advance the understanding of how vascular brain changes affect cognition.