Loss of vessel wall viability in cerebral amyloid angiopathy.

Cerebral amyloid angiopathy (CAA) is a neuropathological feature of Alzeheimer's disease and an important cause of cerebral haemorrhage in the elderly. CAA is characterized by the deposition of Alzheimer amyloid beta protein (A beta) in cerebral and leptomeningeal vessel walls. In order to study the effect of cerebrovascular A beta deposits in vivo, living canine leptomeninges obtained from old dogs affected by CAA were analysed by confocal laser scanning microscopy after immunofluorescence staining for A beta and viability staining with fluorescein diacetate (FDA). Simultaneous detection of the two signals showed a segmental loss of leptomeningeal vessel wall viability at some site of A beta deposition. Many of the non-viable vessels segments were also dilated, suggesting that A beta-induced vascular cell death creates the loci minores resistentiae for the development of cerebral haemorrhage in CAA.