[Brain aging. The problem of differential diagnosis between normal and pathologic].

The author reports three cases of pseudodementia and discuss the difficulties in establishing limits between normality and illness in the elderly. The mental and neuropathological changes that accompany the normal ageing of the brain are similar to those of early Alzheimer's dementia (AD). These similarities often lead to difficulties in the differential diagnosis, hence the search for consensus criteria. The decline of working and secondary memory is greater than that of primary and tertiary memory, as is found in AD. On the other hand, tests of delayed recall of 10 to 15 unrelated words, logical memory, categorical thinking, visuo-motor-spatial skills, and Boston Naming Test have been pointed out as the most discriminative. Neuroimaging findings of atrophy or hypoperfusion in the entorhinal-hippocampal or temporo-parietal regions are suggestive of DA, but they can be lacking in the early stages of this disease. In the conclusion, the author suggests the diagnostic process should be based on a comprehensive neuropsychological and behavioral evaluation (including a survey of the subject's premorbid level of cognitive and socio-occupational functioning), supplemented by neuroimaging and laboratory tests. If inconclusive, the whole evaluation can be repeated after 4 to 6 months, to check the consistency of the findings.