Educational scope notice: This is a study note for medical students, not medical advice, diagnosis, or treatment guidance. Clinical management should follow local protocols and current guidelines.
Amyloid-beta deposits in the walls of small and medium-sized cortical and leptomeningeal arteries. The protein accumulates along the perivascular drainage pathways by which the cortex normally clears amyloid, which is why the disease affects outer-brain vessels and spares the deep perforating arteries supplying the basal ganglia.
Why the vessel wall fails
Amyloid deposition replaces the smooth muscle layer of the vessel wall. The wall loses both structural support and the ability to autoregulate in response to blood pressure changes, becoming stiff and fragile. Small leaks appear first as microbleeds, detectable only on blood-sensitive MRI sequences. Larger lobar haemorrhages follow when a weakened wall gives way completely. Severely affected vessels can develop fibrinoid necrosis, a destructive wall change associated with a higher risk of rupture.
The shared biology with Alzheimer disease
Both conditions involve the same protein deposited in different compartments: Alzheimer disease deposits amyloid-beta as parenchymal plaques, while amyloid angiopathy deposits it in vessel walls. Overlap is common, and many patients carry elements of both diseases. The APOE ε4 allele raises the risk of each, consistent with impaired amyloid clearance from the brain as a shared mechanism.
Evidence anchors
- Romero JR, et al. Cerebral amyloid angiopathy in the elderly: https://pmc.ncbi.nlm.nih.gov/articles/PMC4004372/
- Charidimou A, et al. The Boston criteria version 2.0 for cerebral amyloid angiopathy. Lancet Neurol. 2022: https://pubmed.ncbi.nlm.nih.gov/35841910/