Eighty-three brains obtained at autopsy from nondemented and demented individuals were examined for extracellular amyloid deposits and intraneuronal neurofibrillary changes. The distribution pattern and packing density of amyloid deposits turned out to be of limited significance for differentiation of neuropathological stages. Neurofibrillary changes occurred in the form of neuritic plaques, neurofibrillary tangles and neuropil threads. The distribution of neuritic plaques varied widely not only within architectonic units but also from one individual to another. Neurofibrillary tangles and neuropil threads, in contrast, exhibited a characteristic distribution pattern permitting the differentiation of six stages. The first two stages were characterized by an either mild or severe alteration of the transentorhinal layer Pre-alpha (transentorhinal stages I-II). The two forms of limbic stages (stages III-IV) were marked by a conspicuous affection of layer Pre-alpha in both transentorhinal region and proper entorhinal cortex. In addition, there was mild involvement of the first Ammon's horn sector. The hallmark of the two isocortical stages (stages V-VI) was the destruction of virtually all isocortical association areas. The investigation showed that recognition of the six stages required qualitative evaluation of only a few key preparations.

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Assessment of Alzheimer’s disease (AD)-related neurofibrillary pathology requires a procedure that permits a sufficient differentiation between initial, intermediate, and late stages. The gradual deposition of a hyperphosphorylated tau protein within select neuronal types in specific nuclei or areas is central to the disease process. The staging of AD-related neurofibrillary pathology originally described in 1991 was performed on unconventionally thick sections (100 μm) using a modern silver technique and reflected the progress of the disease process based chiefly on the topographic expansion of the lesions. To better meet the demands of routine laboratories this procedure is revised here by adapting tissue selection and processing to the needs of paraffin-embedded sections (5–15 μm) and by introducing a robust immunoreaction (AT8) for hyperphosphorylated tau protein that can be processed on an automated basis. It is anticipated that this revised methodological protocol will enable a more uniform application of the staging procedure.

Abeta-deposition in the entire brain follows a distinct sequence in which the regions are hierarchically involved. Abeta-deposition, thereby, expands anterogradely into regions that receive neuronal projections from regions already exhibiting Abeta. There are also indications that clinically proven AD cases with full-blown beta-amyloidosis may be preceded in early stages by nondemented cases exhibiting AD-related Abeta pathology.