Cerebral amyloid angiopathy (CAA)
General description
Cerebral amyloid angiopathy (CAA) is a cerebrovascular disorder caused by the accumulation of amyloid β (Aβ) protein within the walls of small- to medium-sized blood vessels in the brain and leptomeninges, particularly in the tunica media and adventitia. This deposition weakens the vessel walls, leading to vascular fragility, luminal narrowing, and occlusion, which often manifest as lobar intracerebral hemorrhage, particularly in normotensive elderly individuals and patients with Alzheimer’s disease. CAA is a major cause of recurrent hemorrhagic strokes in the occipital, temporal, and frontal lobes and can contribute to cognitive decline, including vascular dementia, due to small-vessel damage. Additionally, CAA may present with transient neurological symptoms, inflammatory encephalopathy, incidental microbleeds, or hemosiderosis visible on MRI. It is a significant form of cerebral amyloid deposition disease alongside Alzheimer’s disease.
Cerebral hemorrhage
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CerebrumCerebral cortex
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CerebrumCerebral white matterSubcortical white matter
CAA is characterized by multiple hemorrhages, typically located in the cortico-subcortical regions. These hemorrhages often occur at different times, which is a distinguishing feature. Importantly, they tend to spare the basal ganglia and pons, which are typically affected in hypertensive deep intracerebral hemorrhages.
Microbleedings
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CerebrumParietal lobeCerebral cortex
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CerebrumOccipital lobeCerebral cortex
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CerebrumParietal lobeCerebral white matterSubcortical white matter
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CerebrumOccipital lobeCerebral white matterSubcortical white matter
Cerebral microbleeds, defined as small round or ovoid hemorrhages measuring 2–10 millimeters, are often detected using T2*-weighted imaging. In elderly individuals, microbleeds located in the cortical or cortico-subcortical regions of the occipitaland temporal lobes, particularly near the grey-white matter junction, are highly suggestive of CAA.
Subarachnoid hemorrhage
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Subarachnoid space