[Alzheimer dementia. A clinical long-term study with quantitative neuropathology]

Alzheimer's disease causes about 80% of dementias in old age. The pathological hallmarks of Alzheimer's disease are senile plaques (SP) and neurofibrillary tangles (NFT), which to a lesser degree can also be found in the brains of mentally intact elderly. The question whether SP or NFT or any other process are primarily correlated to severity of dementia can only be answered in prospective longitudinal clinical and neuropsychological studies with quantitative neuropathological investigation. We report the correlations between mini-mental-state scores and lesion counts in 3 isocortical and 3 hippocampal areas in a consecutive series of 19 Alzheimer's patients studied prospectively in the Vienna Longitudinal Study on Dementia. Lesion counts increased at very late stages of dementia and were rather low in mild to moderate severity of dementia. Mildly demented patients with very slow progression of dementia also had rather high lesion counts. Neurofibrillary changes in NFT and neuritic plaques were correlated with severity of dementia, but diffuse plaques, i.e. SP without neuritic degeneration, were not at all correlated with severity of dementia. We speculate that NFT and SP do not represent the primary process which leads to dementia.