The severity of anaemia depletes cerebrovascular dilatory reserve in children with sickle cell disease: a quantitative magnetic resonance imaging study

Summary Overt ischaemic stroke is one of the most devastating complications in children with sickle cell disease ( SCD ). The compensatory response to anaemia in SCD includes an increase in cerebral blood flow ( CBF ) by accessing cerebrovascular dilatory reserve. Exhaustion of dilatory reserve secondary to anaemic stress may lead to cerebral ischaemia. The purpose of this study was to investigate CBF and cerebrovascular reactivity ( CVR ) using magnetic resonance imaging ( MRI ) in children with SCD and to correlate these with haematological markers of anaemia. Baseline CBF was measured using arterial spin labelling. Blood‐oxygen level‐dependent MRI in response to a CO 2 stimulus was used to acquire CVR . In total, 28 children with SCD (23 not on any disease‐modifying treatment, 5 on chronic transfusion) and 22 healthy controls were imaged using MRI . Transfusion patients were imaged at two time points to assess the effect of changes in haematocrit after a transfusion cycle. In children with SCD , CBF was significantly elevated compared to healthy controls, while CVR was significantly reduced. Both measures were significantly correlated with haematocrit. For transfusion patients, CBF decreased and CVR increased following a transfusion cycle. Lastly, a significant correlation was observed between CBF and CVR in both children with SCD and healthy controls.