Re-evaluation of classic senile plaques by three-dimensional analysis.

We evaluated the proportion of classic plaques among all of the senile plaques in four Alzheimer brains (frontal, temporal, occipital and hippocampal areas) by the usual method of two-dimensional analysis using a single methenamine silver-stained section and three-dimensional analysis using a set of serial sections. Three-dimensional analysis showed the number and percentage of classic plaques to be 2-5 times greater than those revealed by two-dimensional analysis. In the hippocampal area of one case, no classic plaques were found by two-dimensional analysis but three-dimensional analysis showed that some classic plaques were present. From these findings, it is suggested that three-dimensional analysis using serial sections is indispensable for subclassifying senile plaques.