Introduction

Abstract

Considering only the points for which there is general consensus (see Henderson and Henderson, 1988; Jorm, 1990; Katzman and Jackson, 1991; Larson et al. 1992), the current knowledge about Alzheimer s disease (AD) can be summarized briefly as follows: 1. Dementia is a syndrome that is present in a range of disorders, characterized by memory deficits and impairment of other cognitive functions sufficient to impair social and occupational activity. Dementia is strongly associated with ageing. 2. AD is a dementing disorder with senile plaques and neurofibrillary tangles as neuropathological hallmarks. 3. Before the mid-1970s, the entity AD was reserved for presenile dementia and did not include senile dementia. Today, AD is commonly used to refer to all cases irrespective of age of onset. 4. The clinical diagnosis of AD involves two steps: the diagnosis of the dementia syndrome and the differentiation of other dementing disorders. The differential diagnosis of AD is largely carried out by exclusion. Slow onset, and slow, progressive, and irreversible course are the main clinical features. Even the pathology (loss of neurons and synapses, presence of senile plaque with a ~\xad amyloid core, and neurofibrillary tangles), is not specific as the differentiation from normal ageing is only quantitative. 5. The pathogenesis is unknown, but neuronal cell degeneration mainly affecting dendrites and synapses, dysfunction of the neurotransmitter system, and amyloid mismetabolism are good candidates for explaining at least some pathways. 6. The etiology is unknown, but genetic alterations seem to play a role, at least in some cases. 7. The course is irreversible and life is shortened. 8. No therapy is yet available that can positively modify the natural history of the disease.