Therapy insight: stroke risk and its management in patients with sickle cell disease.

Children with sickle cell disease, a chronic hemolytic anemia, present with a wide variety of neurological syndromes, including ischemic and hemorrhagic stroke, transient ischemic attacks, 'soft neurological signs', seizures, headache, coma, visual loss, altered mental status, cognitive difficulties, and covert or 'silent' infarction. Those with ischemic stroke usually have stenosis or occlusion of the distal internal carotid and proximal middle cerebral arteries. Indefinite transfusion prevents recurrence in most patients who have had a stroke, and can prevent first stroke in those with high transcranial Doppler velocities. High white cell count, low hemoglobin and oxyhemoglobin desaturation predict neurological complications. Other risk factors for overt ischemic stroke include hypertension, previous transient ischemic attack, covert infarction and chest crisis. For hemorrhagic stroke, aneurysms are common in adults but not children, who often present with hypertension after transfusion or corticosteroids. Seizures are particularly common in patients with cerebrovascular disease and covert infarction; the latter is also associated with hyposplenism and infrequent pain. Factors associated with cognitive difficulties include thrombocytosis, infarction, large-vessel disease, and perfusion abnormality on neuroimaging. As well as investigating the role of genes and the possibility that hydroxyurea or blood pressure control reduce neurological complications, we should explore the modifiable effects of poor nutrition, chronic infection, hemolysis and oxyhemoglobin desaturation on stroke risk.