CT Diagnosis of Cerebral Amyloid Angiopathy

Accurate diagnosis of cerebral amyloid angiopathy (CAA) in living patients is a prerequisite for formulating treatment decisions and clinical trials for this common cerebral small vessel pathology. Although amyloid-PET imaging or CSF analysis can detect cerebrovascular β-amyloid deposits,^1,2 structural brain lesions, in particular CAA-related hemorrhagic lesions, remain the most specific markers of CAA. The modified Boston criteria for CAA³ hinge on hemorrhage number and location as detected by T2*-weighted MRI, requiring multiple, strictly lobar foci of intracerebral hemorrhages (ICH), microbleeding, or cortical superficial siderosis (cSS). The more recently proposed Edinburgh criteria for CAA⁴ take the complementary approach of focusing on ICH morphology on CT imaging. According to the original study of the “simplified” Edinburgh criteria (using CT features alone rather than in combination with APOE ε4 genotyping), the combination of subarachnoid hemorrhage (SAH) plus finger-like projections (defined as extensions from the ICH that are longer than wide) was highly specific for moderate/severe pathologic CAA and the presence of at least 1 of the 2 features was reasonably sensitive.⁴ These findings offered the exciting prospect of diagnosis of CAA-related ICH in settings without MRI.