The dementias: nosological and clinical factors related to diagnosis

There is no integrated nosological system for the classification of dementia. Four classification criteria in common use are site of pathology, histopathological changes, clinical features, and etiology. The use of these criteria, and the influence of other factors on diagnosis, are reviewed. Without a common comprehensive system, confusion has resulted when published studies have been compared. Since no single criterion is currently adequate, practical approaches for researchers and clinicians are suggested.