Alzheimer Disease

P-amyloid accumulates in the brain in Alzheimer’s disease both as plaques and in vessel walls as cerebral amyloid angiopathy (CAA). In this study we test the hypothesis that CAA is due to p-amyloid accumulation in the putative interstitial fluid (ISF) drainage pathways in penvascular spaces around arteries and arterioles in the cerebral cortex and overlying meninges. The distribution of amyloid was recorded in a total of % blocks from 10 bnins from patients with Alzheimets disease by thioflavin S staining and by immunocytochemistry for A4 protein. The results showed that (1) there was positive correlation between the number of amyloid plaques in the cortex and the extent of amyloid angiopathy in the overlying leptomeningeal vessels (2) arteries in the leptomeninges were affected 5 times more frequently than veins (3) arteries less than 60pm in diameter were affected twice as conii-nonly as arteries more than 60km in diameter (4) early deposits of p-ainyloid were in the adventitia and outer media. These results Suggest that 8-amyloid is translocated to vessel walls via putative ISF drainage pathways and thus accumulates predominantly in the adventitia and outer media of inmcortical and leptomeningeal arteries in CAA.