H. ITO, A. HIRANO and S.-H. YEN (Bronx, U.S.A.)

The parkinsonism-dementia complex (PDC) on Guam is characterized histopathologically by neuronal loss in widespread areas and by the presence of numerous Alzheimer’s neurofibrillary tangles in certain neuron groups. It has been reported that in Guamanian PDC patients there is virtually no plaque formation. Prior to 1965, the existence of argentophilic plaques has been investigated in only a few Guamanian cases. However, from more recent studies, there is evidence on plaque formation in a relatively high proportion of Guamanian patients. To determine whether this change is due to differences in the detection techniques, we have re-evaluated with an immunoperoxidase method the archival material used in earlier studies.