IMPORTANCE OF HEMODYNAMIC FACTORS IN THE PROGNOSIS OF STROKE IN PATIENT WITH SCD

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The goal of this project is to better define the physiologic basis for blood transfusion therapy to prevent strokes in sickle cell anemia (SCA) using Positron Emission Tomography (PET) scan of the brain. The most feared consequence of SCA is cerebral infarction, which occurs in 30% of children before their 18th birthday. Monthly blood transfusion therapy is the only secondary prevention for strokes in this patient population. However, the physiologic basis for the therapeutic benefit is not known, nor is the reason why 20% of the patients will have a second stroke. Changes in oxygen extraction fraction (OEF), which can be measured using PET studies of the brain, have been found to be a strong independent predictor of stroke risk in adults without SCA. PET studies have not been systematically performed in patients with SCA to determine the hemodynamic benefit of blood transfusion therapy and to assess whether a lack of change in OEF is an independent risk factor for strokes. In this project, we will test the primary hypothesis that: In patients with SCA and strokes, blood transfusion therapy results in a decrease in the OEF when compared to the patient's baseline. A total of six patients with SCA and strokes will have a PET scan of the brain before and after blood transfusion therapy. We will also identify six patients with SCA without strokes to compare these baseline physiologic measurements. We will test the three secondary hypotheses states above by using magnetic resonance imaging (MRI), magnetic resonance angiography (MRA), and trascranial doppler ultrasonography (TCD). After completion of this project, we will have a better understanding of the role of blood transfusion therapy in preventing strokes and will subsequently collect preliminary data on the physiologic basis for progressive neurological disease in this patient population. We will also gather preliminary data to assess the influence of cerebral hemodynamic on inhibitory control and resolution of cerebral vasculature using MRA.