Preexisting SCIs. (A) Preexisting SCIs associated with subsequent neurological events in children with HbSS or HbSβ⁰ thalassemia. Time to first neurological event-stroke, seizure, TIA for children with normal or conditional TCD measurements (time averaged mean maximum velocity of <200 cm/s, nonimaging, or <185 cm/s imaging technique) and with (n = 68) and without SCIs on MRI (n = 353). (B) Associated with recurrent SCIs in adults with sickle cell anemia. A total of 54 adults with HbSS or HbSβ⁰ thalassemia had a minimum time of 6 months between at least 2 MRIs of the brain; in this group of adults, 43% (n = 23) had SCI at baseline and 57% (n = 31) had no SCI at baseline; individuals with overt stroke were excluded based on history and examination by a neurologist. Reprinted from Jordan et al¹⁵⁹  (A) and Jordan et al²⁶  (B) with permission.