Event-free interval of new overt or silent cerebral infarcts in children with SCD while on transfusion therapy for secondary stroke prevention. Participants with progressive overt and silent cerebral infarction were stratified for the absence (solid line) or the presence (dashed line) of progressive cerebral vasculopathy during chronic blood transfusion therapy. Vertical lines represent censored cases. Median event-free interval for new silent or overt infarction was 3.2 years for the group with progressive vasculopathy and was not reached in the group without progressive vasculopathy (Mantel-Cox log-rank, P = .001). (Reprinted with permission from Hulbert et al, 2011.²³ )