Traditional concepts of dementia focus on diseases primarily affecting cortical gray matter, most notably Alzheimer's disease. Another group of diseases, termed “subcortical,” is also believed to affect higher functions, but clinical distinction and neuropathological specificity of these syndromes have been problematic. We propose that the concept of white matter dementia may have a more specific meaning. A number of conditions demonstrate prominent white matter pathology—toluene-induced dementia, multiple sclerosis, Binswanger's disease, diffuse axonal injury, the AIDS dementia complex, alcoholic dementia, and normal pressure hydrocephalus—and even normal aging involves selective white matter loss. White matter dementias do not display characteristic cortical gray matter signs, such as prominent amnesia and aphasia, nor do they show the typical movement disorders of classical subcortical dementias. Attentional dysfunction may be the most salient neurobehavioral deficit in these diseases, although impaired learning, psychomotor function, and speed of information processing are commonly observed as well.
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