Differentiation of hemorrhagic infarction from primary intracerebral hemorrhage in the chronic period

•Regarding incidentally found old hemorrhagic foci on GRE, it is uncertain whether it is from hemorrhagic infarct or primary intracerebral hemorrhage.•Perilesional high signal on T-2 weighted MRI is more commonly observed in hemorrhagic infarct than in primary intracerebral hemorrhage.•The dark hemosiderin rim which is partially encasing the hemorrhagic old lesion more suggests hemorrhagic infarct than primary intracerebral hemorrhage. Regarding incidentally found old hemorrhagic foci on gradient-echo magnetic resonance imaging (GRE), it is difficult to distinguish whether the foci are the consequence of hemorrhagic infarction (HI) or primary intracerebral hemorrhage (PICH). We analyzed the radiological characteristics of patients with a definite history of HI or PICH by reviewing long-term follow-up GRE. We retrospectively enrolled patients with HI or PICH, verified by clinical history and radiological findings, who had undergone follow-up GRE at least 3 months after the first imaging. The shape of the hemorrhagic lesion was classified as “cavitation” or “no cavitation.” The shape of the hemosiderin rim was classified as total dark rim and partial dark rim. Hyperintense perilesional signal was determined when an obvious hyperintensity on T2-weighted image was present. Further, we compared the radiological characteristics between HI and PICH. In total, 69 patients (38 with HI and 31 with PICH) were enrolled, of whom 45 (65%) were men. The mean patient age was 65.5 ± 12.7 years. The mean time interval from the initial stroke onset to the follow-up image was 56.2 months. Hyperintense perilesional signal was observed in 38 patients; it was associated with HI (33/38 vs. 5/31, p