The overlap between Alzheimer's disease and vascular dementia: the role of white matter changes.

As there is some overlap between Alzheimer's disease (AD) and vascular dementia (VaD), it can be assumed that some particular features that they have in common are responsible for this overlap. One of the candidates is white matter changes whose presence in variants of the two entities is described in this paper. A common, although much debated, division of AD is into two types, type I usually with early and type II usually with late onset. As to VaD, the division can be based on neuropathological changes and vascular disease mechanisms. In one subtype, 'subcortical white matter dementia', white matter lesions are conspicuous features. The overlap between this subtype and AD type I is small, but the overlap is considerable between the same subcortical subtype and AD type II. In the latter, white matter changes and Alzheimer encephalopathy may interact to produce dementia.