Fig. (1) Virtual graph (*) of the possible effects of a symptomatic treatment. *: In reality, the natural evolution of impairment is not lineal and varies according to the stage of the disease; however, the lineal diagram facilitates the conceptual understanding of the action of the drugs. 1: Cognitive decline related to ageing. 2: Cognitive and functional loss due to an untreated progressive disease. 3: The optimum effect of a solely symptomatic treatment is maintained throughout. 4: Symptomatic treatment may produce a transitory beneficial action (4a) or a long-lasting benefit but to a progressively lower degree (4b).