Cerebral Amyloid Angiopathy (CAA) is a cerebrovascular pathology characterized by the accumulation of amyloid-beta (Aβ) peptides in the walls of small to medium-sized blood vessels in the brain[@van2020]. This mechanism page explores how CAA contributes to neurodegenerative processes, particularly in Alzheimer's disease and related dementias.
CAA represents a critical intersection between vascular pathology and neurodegeneration, accounting for both hemorrhagic stroke risk and vascular contributions to cognitive decline[@charidimou2022]. Understanding CAA mechanisms is essential for developing therapeutic strategies that target the vascular component of neurodegenerative diseases.
Pathophysiology
Amyloid Deposition in Cerebral Vessels
CAA involves the progressive deposition of amyloid-beta peptides, predominantly Aβ40, in the media and adventitia of leptomeningeal and cortical blood vessels[@gregg2020]. This vascular amyloid accumulation differs fundamentally from the parenchymal plaque formation seen in Alzheimer's disease.
Cerebral Amyloid Angiopathy (CAA) is a cerebrovascular pathology characterized by the accumulation of amyloid-beta (Aβ) peptides in the walls of small to medium-sized blood vessels in the brain[@van2020]. This mechanism page explores how CAA contributes to neurodegenerative processes, particularly in Alzheimer's disease and related dementias.
CAA represents a critical intersection between vascular pathology and neurodegeneration, accounting for both hemorrhagic stroke risk and vascular contributions to cognitive decline[@charidimou2022]. Understanding CAA mechanisms is essential for developing therapeutic strategies that target the vascular component of neurodegenerative diseases.
Pathophysiology
Amyloid Deposition in Cerebral Vessels
CAA involves the progressive deposition of amyloid-beta peptides, predominantly Aβ40, in the media and adventitia of leptomeningeal and cortical blood vessels[@gregg2020]. This vascular amyloid accumulation differs fundamentally from the parenchymal plaque formation seen in Alzheimer's disease.
Aβ40 predominance: While Aβ42 is more aggregation-prone and forms parenchymal plaques, Aβ40 shows higher affinity for cerebral vessel walls due to its greater solubility and ability to travel further from production sites[@herzig2009]
Vascular wall transformation: Amyloid deposition replaces smooth muscle cells in the media layer, leading to:
Vessel wall thickening and rigidity
Loss of vascular smooth muscle cells
Decreased cerebral blood flow autoregulation
Increased risk of vessel rupture
Perivascular Drainage Failure
The brain's waste clearance system relies heavily on perivascular pathways that drain Aβ along the basement membranes of cerebral blood vessels[@iliff2013]. Several factors impair this drainage in CAA: