A QUANTITATIVE COMPARISON OF PLAQUE TYPES IN ALZHEIMERS-DISEASE AND SENILE DEMENTIA OF THE LEWY BODY TYPE

In a previous study we reported no difference in the overall beta-amyl oid protein (beta AP) load between Alzheimer's disease (AD) and senile dementia of the Lewy body type (SDLT). However, it is possible that d ifferences in the morphology of beta AP plaque types exist, analogous to the differences in cytoskeletal pathology found in these two disord ers. We have carried out a quantitative image analysis of plaque subty pes in the temporal lobe of AD (n = 8), SDLT (ii = 9) and control (n = 11) cases. Measurements of beta AP load and plaque density were consi stently higher in AD and SDLT than in controls. When AD and SDLT cases were compared no differences were seen in either the density or relat ive proportions of classic and diffuse plaques. Based on these results we suggest that the variation in the clinical course of these disease s reflects differences in the cytoskeletal pathology, whereas the fina l state of profound dementia common to both disorders is associated wi th the deposition of beta AP.