Service de physiologie et d’explorations fonctionnelles, Hôpital Lariboisière, 75475 Paris cedex 10, Service d’angiohématologie, Institut des Vaisseaux et du Sang, InsermU689, Hôpital Lariboisière, 75475 Paris cedex 10
Sickle cell disease (SCD) is due to a mutation (GAG to GTG) of the gene of the β-globin chain resulting in a hemoglobinopathy SS. Stroke is a severe complication of SCD in term of mobidity and mortality and 75% of the neurologic events are ischemic. Stroke is a common complication of SCD with a lifetime risk of 25-40% and a peak of incidence before 8 years old. The increased adhesion of sickled red cells to the endothelium contributes to a cascade of activated endothelial cells, activated inflammatory cells and a prethrombotic state. Anemia with the resultant cerebral hyperemia results in hemodynamic insufficiency. These two mechanisms induce the vascular lesion with intimal proliferation and vascular occlusion. The vascular stenosis leads to the development of a collateral vascularisation (Moyamoya) with an hemorrhagic risk. Measurements of cerebral blood flow velocity by transcranial Doppler (TCD) ultrasonography is a useful tool to predict the risk of stroke. TCD values ≤ 170cm/s are normal, but TCD values ≥ 200cm/s are significant predictors of stroke with a risk of 40% in 3 years, in the absence of therapy. A program of blood transfusion therapy in order to maintain a level of hemoglobin below 30% reduces the risk of recurrent stroke from 10 to 2%. Patients with TCD values ≥ 200cm/s have to be treated. Although neurological complications have been mainly described in children, with the prolonged survival of the SCD patients, the prevalence of stroke has to be evaluated in adults.