[Morphology of Alzheimer disease]

During the course of Alzheimer's disease, considerable amounts of abnormal proteins accumulate within the brain, in particular in the cortex. Some of this material is extracellular (amyloid), some within the neurons (neurofibrillary changes). The extent of the pathological deposits is variable, some regions being particularly severely involved. The entorhinal cortex is already destroyed in the initial phase, followed, in a stepwise fashion, by the hippocampus and the association areas in the isocortex. The undisturbed transfer of information from the isocortical association areas to the hippocampus via the entorhinal area is of importance for mnestic functions. The destructive cortical changes of Alzheimer's disease lead to early and severe impairment or complete blockage of this information pathways.