The close cooperation of clinical and laboratory research has helped to clarify the etiology of some of the dementing processes of the senium. However, the necessary investigations are complicated, laborious, expensive and can be carried out only in well equipped centres in larger cities. This restricts the number of patients who eventually may benefit from these investigations to a small number. What is needed for the psychogeriatric practice particularly in rural areas and smaller cities are simple diagnostic guidelines for the psychiatrist to answer the question whether the patient suffers from a dementia and if so whether the dementia is in all probability due to a primary degenerative process of the brain parenchyma or of the cerebral vasculature or is it due to another cause.
If degeneration of the brain parenchyma seems the prevalent pathogenetic mechanism one would like to establish in a given case which of the known degenerative processes is most probably present in order to avoid mistakes in clinical judgement with their often life threatening consequences.