Silent infarction as a risk factor for overt stroke in children with sickle cell anemia: A report from the Cooperative Study of Sickle Cell Disease

Objective: To determine whether children with homozygous sickle cell anemia (SCD) who have silent infarcts on magnetic resonance imaging (MRI) of the brain are at increased risk for overt stroke. Methods: We selected patients with homozygous SCD who (1) enrolled in the C ooperative Study of Sickle Cell Disease (CSSCD) before age 6 months, (2) ha d at least I study-mandated brain MRI at age 6 years or older, and (3) had no overt stroke before a first MRI. MRI results and clinical and laboratory parameters were tested as predictors of stroke. Results: Among 248 eligible patients, mean age at first MRI was 8.3 +/- 1.9 years, and mean follow-up after baseline MRI was 5.2 +/- 2.2 years. Five ( 8.1%) of 62 patients with silent infarct had strokes compared with 1 (0.5%) of 186 patients without prior silent infarct; incidence per 100 patient-ye ars of follow-up was increased 14-fold (1.45 per 100 patient-years vs 0.11 per 100 patient-years, P = .006). Of several clinical and laboratory parame ters examined, silent infarct was the strongest independent predictor of st roke (hazard ratio = 7.2, P = .0277). Conclusions: Silent infarct identified at age 6 years or older is associate d with increased stroke risk.