One study found that nocturnal desaturation predicted neurological events in 95 patients with SCD (median age, 7.7 years; range, 1 to 23 years) followed up for a median of 6 years.564 There were 7 strokes among 19 individuals with events. Mean overnight oxygen saturation and TCD independently predicted events.564 Nocturnal oxygen desaturation appears to place children at risk for developing executive dysfunction, which was not associated with MRI- There is no proven therapy for the cognitive impairment associated with nocturnal desaturation. MRI has also been used to identify children with SCD who are at high risk of stroke. The Cooperative Study of Sickle Cell Disease, which preceded the use of TCD-based monitor- ing, found that 8.1% of children with an asymptomatic MRI lesion versus 0.5% of those with a normal MRI had a stroke during the ensuing 5 years.566 The Silent Cerebral Infarct Multicenter Clinical Trial (SIT), a randomized, controlled trial MRI-guided prophylactic transfusion, found that regular blood transfusion significantly reduced the incidence of the recurrence of cerebral infarction in children with sickle cell In a cohort of 67 patients with indication for cervi- cal internal carotid artery MRA, 15% of patients had occlu- sions or stenoses.568 The role of cervical MRA in stroke risk prediction remains undefined. Additional clinical features identify children at risk for devel- oping elevated TCD velocities and stroke. 