Vascular dementia-Pathogenesis and relationship to Alzheimer's disease-

Cerebrovascular disease and Alzheimer's disease (AD) are the most frequent causes of dementia in the elderly. Pathological backgrounds for vascular dementia (VaD) are heterogenous. Cerebral white matter is mostly involved in dementia due to small-vessel disease and Binswanger's diease. In Binswanger's disease, a quantitative electron microscopic study showed the reduction of nerve fibers, oligodendrocytes and astrocytes in the white matter. These changes are associated mainly with lipohyalinosis (angionecrosis) of small intraparechymal arteries as well as atherosclerosis of main cerebral arteries. The changes in arterioles are believed to cause blood-brain barrier impairments, activation of microglia, and increased production of cytokines and free radicals, all of which may lead to white matter damage. Clinical, pathological and neuroimaging features are different between typical cases with VaD and AD. However, recent studies have reported that VaD has also characteristic features of AD, including hippocampal atrophy, the reduction in acetylcholine concentration in the bain, and possible beneficial effect of acetylcholine esterase inhibitors. Like VaD, AD also shows carebral white matter changes and changes in cerebral blood flow and oxygen metaboloism. Epidemiological studies have reported that almost all risk factors for cerebrovascular disease increased the risk of AD. Further clinicopathological investigation will enhance our understanding of the relation of VaD to AD and our capability to prevent and treat VaD and AD.