[Can neurologic lesions explain memory disorders of the elderly?]

To answer the questions, where are the lesions responsible for memory disorders located in "normal" aged individuals and how can they be distinguished from those of organic diseases such as Alzheimer's, is not easy, and no currently available parameters enable us to differentiate qualitatively between the lesions in the normal aged brain susceptible to cause memory deficiencies from the more plentiful ones found in Alzheimer's disease. Perhaps it is merely a problem of technical difficulties. Indeed, interpreting the findings reported in the literature is difficult because, for a long time, certain elementary precautions were not taken in the determination of anatomic-clinical correlations. In addition, morphologists and biologists were unaware of the delayed expression of the neuropathological symptoms, the frequency of diseases capable of causing memory disorders, the importance of familial support, the frequency of false dementia, and the influence of the population evaluated: only prospective studies, clinical then neuropathological, will avoid these problems, but it is very difficult to study "benign" memory disorders in aging. Theoretical difficulties are rooted in the definition of "normalcy" in the adult and especially in the aged. Today, the tendency is towards the use of statistical criteria. Should a continuous approach to normality (the whole group is considered as a homogeneous populations) be used or a discontinuous one, more genetic, like that of Gallen and Gambino, distinguishing between several populations, normal and pathological? Neuropathologists and some clinicians prefer the latter.