An Immunohistochemical Study of Perivascular Plaque in Alzheimer's Disease and Cerebral Amyloid Angiopathy

Immunohistochemical study of perivascular plaques (PPs) in 7 patients with Alzheimer's disease (AD) and 4 with cerebral amyloid angiopathy (CAA)(CAA with dementia in 3 patients and CAA with massive cerebral hemorrhage in 1 patient) demonstrated that PPs were also a common form of amyloid P (AP) deposits, like SPs and CAAs, in both AD and CAA, and that they had similar immunostaining characteristics to mature senile plaques (SPs), manifesting as always positive for both A(342 and AP40 but predominant for A(342. In addition, PPs were always associated with AT8-positive degenerated neurites and GFAPpositive astrocytes and fibers. These findings suggest that PPs as mature plaques contribute to the development of dementia, especially in CAA with dementia which lack AD pathology. Moreover, semiquantitative analysis revealed no correlation between the number of PPs and that of SPs, but a good correlation between the number of PPs and that of CAAs, suggesting that there was a close relationship of the formation of PPs and the development of CAAs. PPs were also found around non-CAA arteries, although they were frequent around varying degrees of CAAs, suggesting that the initial A1342 deposits in PPs contribute to the development of CAAs.