Cerebral amyloid angiopathy and astrocytic gliosis in Alzheimer's disease.

Astrocytic reaction at amyloid infiltrated cortical vessels was studied using glial fibrillary acidic protein (GFAP) stain in two cases of Alzheimer's disease (AD). Sections from the visual and prefrontal cortex were stained with H&E, Bodian, Congo red, and thioflavin S in addition to GFAP. Senile plaques and neurofibrillary tangles were present in both cases. The density of astrocytes surrounding vessels infiltrated with amyloid was variable. In the same area, there were vessels with minimal perivascular astrocytic reaction as well as vessels displaying more pronounced perivascular gliosis; there was no constant excessive gliosis around vessels with severe amyloid deposits. However, if amyloid infiltrating the vessel wall protruded into the perivascular neuropil of the cortex, then prolific reaction of astroglia, similar to that seen at interstitial senile plaques was apparent, and a neuritic component was distinct. It appears that once amyloid of AD type is deposited in the neuropil, whether in form of interstitial plaque or perivascular plaque, it causes a similar astroglial and neuritic reaction.