LARGE AMOUNTS OF NEOCORTICAL BETA-A4 DEPOSITS WITHOUT NEURITIC PLAQUES NOR TANGLES IN A PSYCHOMETRICALLY ASSESSED, NONDEMENTED PERSON

An 88-year-old mentally normal woman (Blessed test score=27) had very large amounts (397/mm2) of deposits stained by anti-βA4 serum in the first temporal gyrus. Senile plaques and neurofibrillary tangles were lacking on sections stained with the Bodian's silver method, with anti-tau and anti-paired helical filament (anti-PHF) antibodies. The following βA4 deposits were found in decreasing order of frequency: diffuse (64.8%), stellate (24.4%), primitive (10.2%), classic (0.6%) plaques. Compact plaques were not observed. Diffuse deposits predominated in layers I, III and IV. On the contrary, the rare classic plaques were located in layers II and III. No amyloid angiopathy was seen with Congo red stain although βA4 deposits were seen in vessel walls with immunocytochemistry. These data indicate that severe diffuse βA4 deposits in the neocortex do not induce dementia. They suggest that the development of senile plaques composed of βA4 amyloid and of degenerating neurites is not related solely to the density of the diffuse βA4 deposits. Nor does it depend on the regional susceptibility of the nervous tissue since βA4 deposits were seen in highly vulnerable cortical areas. Some other, as yet unknown, factors seem necessary. In addition, determination of βA4 level in the neocortex is not sufficient for the diagnosis of dementia of Alzheimer type. © 1990.