White matter changes in dementia of Alzheimer's type. Biochemical and neuropathological correlates.

A correlative neuropathological-biochemical study was undertaken in order to characterize the selective incomplete white matter infarctions (SIWI) frequently found in dementia of Alzheimer's type. The brain tissue analysed represented white matter with incomplete infarction, complete infarcts and with histologically normal tissue, in cases with dementia, mainly of Alzheimer and multi-infarct type, in nondemented subjects with cerebral infarcts and in age-matched control cases. The biochemical results verify the existence of the white matter changes and agree on their regional distribution as they appear in the morphological analyses. The increasing severity of SIWI as assessed histologically was reflected in a proportional reduction of several biochemically quantified white matter components. The histological difference between incomplete and complete infarction was also expressed biochemically. Incomplete white matter infarction with and without associated complete infarcts were biochemically similar. The aetiological significance of the loss of different white matter components is discussed. The biochemical data support the concept of SIWI as being an independent white matter disorder of cerebrovascular, hypoperfusional/hypoxic origin.