Infarct location has a critical effect on patient outcome after ischemic stroke, but the study of its role independent of overall lesion volume is challenging. We performed a retrospective, hypothesis-generating study of the effect of infarct location on three-month functional outcome in a pooled analysis of the EPITHET and DEFUSE studies.

Posttreatment MRI diffusion lesions were manually segmented and transformed into standard-space. A novel composite brain atlas derived from three standard brain atlases and encompassing 132 cortical and sub-cortical structures was used to segment the transformed lesion into different brain regions, and calculate the percentage of each region infarcted. Classification and Regression Tree (CART) analysis was performed to determine the important regions in each hemisphere associated with nonfavorable outcome at day 90 (modified Rankin score [mRS] > 1).

Overall, 152 patients (82 left hemisphere) were included. Median diffusion lesion volume was 37·0 ml, and median baseline National Institutes of Health Stroke Score was 13. In the left hemisphere, the strongest determinants of nonfavorable outcome were infarction of the uncinate fasciculus, followed by precuneus, angular gyrus and total diffusion lesion volume. In the right hemisphere, the strongest determinants of nonfavorable outcome were infarction of the parietal lobe followed by the putamen.

Assessment of infarct location using CART demonstrates regional characteristics associated with poor outcome. Prognostically important locations include limbic, default-mode and language areas in the left hemisphere, and visuospatial and motor regions in the right hemisphere.