Alzheimer's disease
Deposits of beta-amyloid also form in the walls (in the tunica media, the middle layer, and  tunica adventitia or tunica externa, the outer layer) of small and mid-sized arteries (and sometimes veins) in the cerebral cortex and the leptomeninges (the leptomeninges are the two inner layers - pia mater and arachnoid - of the meninges, a protective 3-layer membrane covering the brain.)