[2][3] The term congophilic is sometimes used because the presence of the abnormal aggregations of amyloid can be demonstrated by microscopic examination of brain tissue after staining with Congo red.

[14] CAA has been identified as occurring either sporadically (generally in elderly populations)[15] or in familial forms such as Flemish, Iowa, and Dutch types.

[19][20] In familial forms of CAA, the cause of Aβ build up is likely due to increased production rather than poor clearance.

In type 2 CAA pathology, amyloid deposits are present in leptomeningeal and cortical arteries and arterioles, but not in capillaries.

[28] When no tissue is available for biopsy, the Boston criteria are used to determine probable CAA cases from MRI or CT scan data.

The Boston Criteria require evidence of multiple lobar or cortical hemorrhages to label a patient as probably having CAA.

[24] MRI sequence of gradient echo and susceptibility weighted imaging (SWI) are useful in detecting microbleeds and deposition of iron on the brain cortex (cortical superficial siderosis).

[2] Gustav Oppenheim was the first to report vascular amyloid β deposits on the vasculature of the central nervous system in 1909.