Abstract WP553: Differentiation of Cortical Microinfarctions Due to Cerebral Amyloid Angiopathy From Those Caused by Microembolism on 3T MRI

Abstract

Background: Cortical microinfarctions (CMI) are often detected in patients with cerebral amyloid angiopathy (CAA) and cerebral microembolism. Purpose: To evaluate whether the size, location and distribution of CMIs differ between CAA and microembolism on 3T MRI. Methods: We retrospectively screened 657 patients who consulted our memory clinic from Jan 2011 to Mar 2018 and underwent detection protocol for CMIs (3-dimensional double inversion recovery (DIR), 3-dimensional fluid attenuated inversion recovery (FLAIR) and susceptibility-weighted imaging (SWI) on 3T MRI). There were 120 patients which had DIR-positive and SWI-negative lesion less than 10 mm in diameter. These patients were classified to embolic stroke group and CAA group which fulfilled the modified Boston criteria for possible or probable CAA. We analyzed the size, location and distribution of small cortical lesions on each group. Result: We enrolled 44 patients as embolic stroke group and 27 patients as CAA group. A total of 175 small cortical lesions were identified in the embolic stroke group and 63 in the CAA group. Mean number of small cortical lesions in the embolic stroke group was significantly higher than those of the CAA group (4.0 vs 2.3; p = 0.001). In the CAA group, the frequency of cortical lesions less than 5mm and localized in the cortical gray matter; ie. CMI, was higher than in the embolic stroke group (92% vs 69%; p < 0.001). By contrast, the frequency of cortical lesions larger than 5mm was significantly higher in the embolic stroke group than in the CAA group (21% vs 8%; p = 0.004). Furthermore, the frequency of cortical lesions involving subcortical area was significantly higher in the embolic stroke group than in the CAA group (30% vs 8%; p < 0.001). Regarding their distribution, the CAA group showed occipital lobe dominance compared to the embolic stroke group (30% vs 10%; p < 0.01). Conclusion: Our results suggest that CMIs caused by CAA tend to be less numerous, localized in the cortical gray matter and smaller than 5mm, and show occipital dominance compared to those by microembolism. These characteristics may be helpful for differentiating CMIs due to CAA from those caused by microembolism.