Cerebral [Amyloid] Angiopathy (Caa) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
Cerebral amyloid angiopathy (CAA) is a cerebrovascular disorder characterized by the progressive deposition of [Amyloid-Beta[/proteins/[Amyloid-Beta[/proteins/[Amyloid-Beta[/proteins/[Amyloid-Beta[/proteins//proteins/[Amyloid-Beta--TEMP--/proteins/)--FIX-- peptide in the walls of small- to medium-sized cerebral blood vessels, leptomeningeal arteries, and arterioles. This accumulation weakens vessel walls and leads to lobar intracerebral hemorrhage, microbleeds, cognitive decline, and white matter injury.<a href="#references">1
CAA is one of the most common cerebrovascular pathologies in older adults, with moderate to severe CAA found in 30–40% of individuals over age 80 at autopsy. It is a major cause of spontaneous lobar hemorrhage and an important contributor to [Vascular Dementia[/diseases/[vascular-dementia[/diseases/[vascular-dementia[/diseases/[vascular-dementia--TEMP--/diseases)--FIX--. CAA frequently co-occurs with [Alzheimer's disease[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers--TEMP--/diseases)--FIX--, sharing [Amyloid-Beta[/proteins/[Amyloid-Beta[/proteins/[Amyloid-Beta[/proteins/[Amyloid-Beta[/proteins//proteins/[Amyloid-Beta--TEMP--/proteins/)--FIX-- as the central pathogenic protein.<a href="#references">2
CAA results from the failure to clear [Amyloid-Beta[/proteins/[Amyloid-Beta[/proteins/[Amyloid-Beta[/proteins/[Amyloid-Beta[/proteins//proteins/[Amyloid-Beta--TEMP--/proteins/)--FIX-- from the brain via perivascular drainage pathways. As amyloid deposits accumulate in vessel walls, they cause structural damage including smooth muscle cell loss, vessel wall thickening, fibrinoid necrosis, and microaneurysm formation. This progressive vasculopathy renders cerebral blood vessels fragile and prone to rupture, causing hemorrhagic and non-hemorrhagic brain injury.
The disease is strongly age-dependent, uncommon before age 60, and its prevalence increases substantially with each decade of life. It represents a significant convergence between cerebrovascular disease and neurodegeneration.
- Autopsy studies: Moderate to severe CAA is present in 10–40% of unselected elderly brains and in up to 80% of brains with concurrent [Alzheimer's disease[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers--TEMP--/diseases)--FIX--<a href="#references">2
- Clinical incidence: CAA accounts for approximately 12–20% of spontaneous intracerebral hemorrhages in individuals over age 55
- Age dependence: Prevalence increases sharply after age 60; rare before age 50
- No sex predilection: CAA affects men and women equally in most studies
- Advanced age: The single strongest risk factor for CAA6
- [APOE[/entities/[apoe[/entities/[apoe[/entities/[apoe--TEMP--/entities)--FIX-- ε4 allele: Strong genetic risk factor, particularly associated with capillary-type CAA (Type 1)8
- Anticoagulant use: Significantly increases hemorrhage risk in CAA patients
- Previous hemorrhage: History of lobar intracerebral hemorrhage is major risk for recurrence
- Perivascular drainage failure: [Amyloid-Beta[/proteins/[Amyloid-Beta[/proteins/[Amyloid-Beta[/proteins/[Amyloid-Beta[/proteins//proteins/[Amyloid-Beta--TEMP--/proteins/)--FIX-- is normally cleared from the brain via perivascular (glymphatic) drainage along basement membranes of capillaries and arteries. Age-related stiffening of vessel walls impairs this drainage
- Vessel wall infiltration: [Amyloid-Beta[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta--TEMP--/entities)--FIX-- accumulates in the tunica media and adventitia, replacing smooth muscle cells
- Progressive vasculopathy: Smooth muscle cell loss leads to vessel wall weakening, fibrinoid necrosis, and microaneurysm formation
- Rupture and hemorrhage: Weakened vessels are prone to spontaneous rupture, causing lobar intracerebral hemorrhage
CAA predominantly involves Aβ40 in vessel walls, unlike [Alzheimer's disease[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers--TEMP--/diseases)--FIX-- parenchymal plaques which are predominantly Aβ42. This distinction is important because:
- Aβ40 is more soluble and drains via perivascular pathways
- Aβ42 is more prone to form parenchymal aggregates
- The relative ratio of Aβ40/Aβ42 in CSF may help distinguish CAA from pure [Alzheimer's disease[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers--TEMP--/diseases)--FIX--
Recent research has revealed an important role for [Tau[/proteins/[tau[/proteins/[tau[/proteins/[tau--TEMP--/proteins)--FIX-- in CAA pathogenesis. In CAA mouse models, depletion of endogenous tau reduced vascular amyloid deposition, prevented vascular damage, ameliorated motor and synaptic impairments, and decreased [astrocytes[/cell-types/[astrocytes[/cell-types/[astrocytes[/cell-types/[astrocytes--TEMP--/cell-types)--FIX-- reactivity. This suggests that tau modulation could represent a therapeutic strategy for CAA6.<a href="#references">4
| Type |
Location |
Vessel Layer |
Characteristics |
| Type 1 |
Cortical capillaries + arteries |
Basement membrane, media |
More severe; associated with [APOE[/genes/[apoe[/genes/[apoe[/genes/[apoe--TEMP--/genes)--FIX-- rather than deep or infratentorial |
- High recurrence risk (~21% over 2 years) compared to hypertensive hemorrhage
Recurrent, stereotyped episodes lasting minutes:
- Motor weakness, sensory symptoms, visual disturbance, or language dysfunction
- Often preceded by cortical superficial siderosis or convexity subarachnoid hemorrhage
- Can be mistaken for TIA but are typically "spreading" rather than sudden onset
CAA contributes to cognitive decline through multiple mechanisms:
- Gradual decline: From cumulative microbleeds, white matter injury, and microinfarcts
- Stepwise decline: Following recurrent symptomatic hemorrhages
- Rapid decline: Associated with CAA-related inflammation (CAA-ri)
An inflammatory variant presenting with:
- Acute or subacute cognitive decline, headache, seizures, focal deficits
- MRI shows asymmetric white matter hyperintensities and leptomeningeal enhancement
- Responds to immunosuppressive therapy (corticosteroids, cyclophosphamide)
- May be triggered by autoantibodies against vascular [amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta--TEMP--/entities)--FIX--<a href="#references">7
The revised Boston criteria provide a standardized diagnostic framework:<a href="#references">8
Definite CAA: Full postmortem examination showing severe CAA with supporting vasculopathy
Probable CAA (age ≥50):
- Clinical presentation consistent with CAA, AND
- ≥2 strictly lobar hemorrhagic lesions (ICH, microbleeds, cortical superficial siderosis, convexity SAH), OR
- 1 lobar hemorrhagic lesion + 1 white matter feature (severe perivascular spaces >20/hemisphere or multispot white matter hyperintensity pattern)
Possible CAA (age ≥50):
- Single lobar hemorrhagic lesion, OR
- Isolated white matter feature consistent with CAA
- Gradient-echo MRI / SWI: Demonstrates microbleeds as small hypointense foci; lobar distribution supports CAA
- T2/FLAIR MRI: White matter hyperintensities, enlarged perivascular spaces
- Cortical superficial siderosis: Linear hemosiderin along cortical surface; highly suggestive of CAA
- [amyloid PET[/entities/[amyloid-pet[/entities/[amyloid-pet[/entities/[amyloid-pet--TEMP--/entities)--FIX--: Positive in CAA (binds vascular and parenchymal amyloid); cannot distinguish CAA from Alzheimer's alone
- Decreased Aβ40 (more specific for CAA6 than Aβ42 alone)
- Decreased Aβ40/Aβ42 ratio may help distinguish from pure [Alzheimer's disease[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers--TEMP--/diseases)--FIX--
¶ Treatment and Management
- Blood pressure control (target systolic <140 mmHg)
- Intracranial pressure monitoring and management
- Surgical evacuation considered for accessible lobar hematomas with mass effect
- Reversal of anticoagulation if applicable
The PROGRESS trial demonstrated a 77% reduction in CAA-related intracerebral hemorrhage with blood pressure control using perindopril, making blood pressure management the most evidence-based preventive strategy.<a href="#references">9
- Anticoagulants generally avoided due to hemorrhage risk
- Left atrial appendage occlusion increasingly considered for patients with atrial fibrillation who cannot safely take anticoagulants
- Antiplatelet agents used cautiously; risk-benefit must be individually assessed
- First-line: High-dose corticosteroids (methylprednisolone or dexamethasone) with slow taper
- Second-line: Cyclophosphamide, azathioprine, mycophenolate mofetil, or methotrexate for severe or recurrent episodes<a href="#references">7
- Anti-amyloid immunotherapy: Concern about amyloid-related imaging abnormalities (ARIA), which may be more common/severe in patients with CAA
- Tranexamic acid (TXA): Antifibrinolytic agent being investigated in pilot trials to reduce hemorrhage risk
- [Tau[/entities/[tau-protein[/entities/[tau-protein[/entities/[tau-protein--TEMP--/entities)--FIX---targeting therapies: Based on evidence that tau depletion reduces vascular amyloid deposition<a href="#references">4
- Mortality from CAA-related ICH ranges from 10–30%
- Recurrence risk: ~21% over 2 years for lobar ICH, higher than hypertensive hemorrhage
- Prognostic factors: Worse outcomes with age ≥75, large hematoma volume (>50 mL), intraventricular hemorrhage, decreased consciousness
- Long-term: Progressive cognitive decline is common, even without symptomatic hemorrhage
- CAA is associated with both [Vascular Dementia[/diseases/[vascular-dementia[/diseases/[vascular-dementia[/diseases/[vascular-dementia--TEMP--/diseases)--FIX-- and [Alzheimer's disease[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers--TEMP--/diseases)--FIX--
- ARIA in anti-amyloid therapy: Understanding why patients with CAA are at higher risk for amyloid-related imaging abnormalities during anti-amyloid immunotherapy
- Biomarker development: Blood-based markers specific for CAA6 versus Alzheimer's Disease
- Perivascular drainage: Therapies to enhance glymphatic clearance of vascular amyloid
- Genetic studies: Large-scale GWAS to identify additional CAA susceptibility loci
- Iatrogenic CAA: Understanding [amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta--TEMP--/entities)--FIX-- transmissibility and clinical implications
The International CAA Association coordinates research efforts and in 2025 published a landmark scientific statement on CAA diagnosis and management in collaboration with the World Stroke Organization.<a href="#references">10
The study of Cerebral Amyloid Angiopathy (Caa) has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
- [Astrocytes[/cell-types/[astrocytes[/cell-types/[astrocytes[/cell-types/[astrocytes--TEMP--/cell-types)--FIX--
- [Amyloid-Beta (Aβ)[/proteins/[Amyloid-Beta[/proteins/[Amyloid-Beta[/proteins/[Amyloid-Beta[/proteins//proteins/[Amyloid-Beta--TEMP--/proteins/)--FIX--
- Viswanathan and Greenberg, Cerebral Amyloid Angiopathy in the Elderly (2011)
- Keage et al., Population studies of sporadic cerebral amyloid angiopathy: systematic review (2009)
- Charidimou et al., Emerging concepts in sporadic cerebral amyloid angiopathy (2017)
- Cordonnier et al., Diagnosis and management of cerebral amyloid angiopathy: a scientific statement from the International CAA Association and the World Stroke Organization (2025)
- Greenberg et al., Cerebral amyloid angiopathy and Alzheimer's Disease (2020)
- van Veluw et al., Cerebral amyloid angiopathy: from leak to hemorrhage (2017)
- Smith and Greenberg, Beta-amyloid angiopathy and cognitive impairment (2022)
- Banerjee et al., APOE ε4 and cerebral amyloid angiopathy (2017)