Alzheimer's disease: mismatch between amyloid plaques and neuritic plaques.

Isocortical amyloid deposits and neurofibrillary changes were studied using selective silver staining methods. Amyloid was found in plaque-like formations varying in size and shape. The distribution pattern of these plaques as seen in the silver-stained preparations was identical to that recognized by A4 protein (amyloid) immunostaining. Consecutive sections stained for amyloid and neurofibrillary changes revealed the absence of intraneuronal cytoskeleton abnormalities within the boundaries of many of the amyloid plaques. Congo red preparations did not show these plaques and the tissue within the range of the plaques did not reveal any conspicuous neuropil distortions and/or glial cell accumulations. Hence, a considerable proportion of the amyloid plaques do not correspond to and should carefully be distinguished from 'primitive', 'mature', and 'burned out' types of neuritic (senile) plaques.