Evidence for chronic ischaemia in the pathogenesis of vascular dementia: from neuroPATH to neuroPET.

Vascular dementia is actually considered as a ill-defined entity. The clinical and neuropathologic criteria of this multifactorial disorder remain uncertain. Although not widely accepted, the introduction of the concept of incomplete infarction in the brain can help to explain some particular types of vascular dementia. In the hypoxic-hypoperfusion dementia syndromes of cerebral cortex and white matter and in lacunar state dementia, which are the most common types of vascular dementia, areas of incomplete infarction co-exist with regions of complete infarction. Although initially rejected by early positron emission tomographic studies, it can now be demonstrated that these incomplete infarction areas reflect chronic ischaemia of the brain and that they are relevant to the pathogenesis of vascular dementia.