Age

≥50 required for probable/possible CAA.

Pathology (if available)

Definite CAAFull brain post-mortem: severe CAA, no other lesion

Probable CAA with supporting pathologyEvacuated hematoma or cortical biopsy showing CAA

Qualifying presentation

Spontaneous ICH, transient focal neurological episodes (TFNE), or cognitive impairment/dementia.

Strictly lobar hemorrhagic lesions (T2*)

ICH, microbleeds, cortical superficial siderosis, or convexity SAH; multiple foci count as multiple. Cerebellar not counted as lobar or deep.

White matter feature

Severe centrum semiovale perivascular spaces (>20 in one hemisphere) OR multispot WMH (>10 subcortical FLAIR dots bilaterally).

Present

Deep hemorrhagic lesions on T2*

Basal ganglia, thalamus, brainstem, deep white matter. Absence required for probable/possible CAA (improves specificity); ~15% of pathologically proven CAA can have deep microbleeds.

Present (excludes probable/possible per strict criteria)

Other cause of hemorrhagic lesions

Head trauma, hemorrhagic transformation of ischemic stroke, AVM, hemorrhagic tumor, warfarin INR >3, vasculitis. If any present, CAA criteria are excluded.

Present (excludes CAA diagnosis by criteria)

Boston Criteria 2.0 for Cerebral Amyloid Angiopathy Calculator