How does cerebrovascular disease cause dementia?

There are several factors that might be important in the development of dementia due to cerebrovascular disease. These include the volume of infarcted brain, the bilaterality and symmetry of lesions, the strategic location of small lesions, the number of lesions, the extent and density of white matter lesions and the coexistence of other pathologies, particularly Alzheimer's disease. No one factor is solely related to dementia and in most patients several of these factors combine to exceed the critical threshold for normal cognition. It is the extent of the disease which determines the development of dementia, rather than its etiology. Conversely, the possibility of treatment depends more on the etiology of the vascular disease than on the extent.