Diagnosis of cerebral amyloid angiopathy. Sensitivity and specificity of cortical biopsy.

Examination of cortical tissue obtained surgically is an important tool for diagnosis of cerebral amyloid angiopathy (CAA) during life. Analysis of a single sample of cortical tissue, however, might lead to conclusions that are either falsely positive (because of the high frequency of CAA in the healthy elderly) or falsely negative (because of the patchy distribution of CAA pathology). We therefore attempted to estimate the sensitivity and specificity of cortical biopsy for diagnosis of CAA as the cause of intracerebral hemorrhage. To simulate biopsy in CAA, we took biopsy-sized cortical samples from postmortem brains with known extents of CAA: either CAA-related hemorrhage or mild to severe CAA without hemorrhage. Samples were stained with the use of methods routinely available in surgical pathology laboratories and blindly examined for vascular amyloid and amyloid-related vasculopathic changes. The presence of vascular amyloid was a sensitive marker for CAA-related hemorrhage, occurring in all 28 specimens from brains with hemorrhage. Conversely, the appearance of fibrinoid necrosis in amyloid-laden vessels was relatively specific for CAA-related hemorrhage. This finding occurred in 13 of the 28 specimens (46%) from brains with hemorrhage but in none of 27 sections from brains with mild CAA and in only 4 of 42 specimens with moderate to severe CAA without hemorrhage. These data help to define criteria for the diagnosis of CAA-related hemorrhage from surgical specimens.