What is the evidence for using hydroxyurea for secondary stroke prevention?

Abstract

A 10-year-old male patient with hemoglobin SS suffered a stroke at 7 years of age and was initially transfused at the time of presentation to lower the hemoglobin S concentration to < 30%. You are asked by the family if their child can be treated with oral hydroxyurea rather than monthly transfusions for the secondary prevention of strokes.