It must be emphasized that Alzheimer's disease is not the only type of dementia. Two other forms are dementia with Lewy bodies and Parkinson's disease dementia.
In both forms, the diagnosis is of vital importance because the treatment for these dementias differs from that for Alzheimer's dementia, as Brit Mollenhauer and co-authors explain in the dementia theme issue of Deutsches Ärzteblatt International
(Dtsch Arztebl Int 2010; 107: 684-91).
In more than 75% of patients, the memory impairments are due to Alzheimer's disease. In Lewy body dementia, which is accompanied by cognitive and/or further psychiatric symptoms, and in Parkinson's disease dementia, these develop only after the motor symptoms of the disorder have fully developed.
Gerhard Eschweiler and co-authors (Dtsch Arztebl Int 2010; 107: 677-83) in their article introduce biomarkers that raise the probability of identifying Alzheimer's disease at the stage of mild cognitive impairment and up to five years before full-blown dementia to 80%.
Richard Mahlberg in an introductory editorial emphasizes that the attempts to find an exact differential diagnosis are not merely academic exercises, but that new developments of diagnosis-specific, differentiated interventions for the future depend crucially on a correct initial diagnosis.