The patient was diagnosed with sickle cell anemia complicated by a right-sided cerebral stroke. Stroke is one of the leading causes of morbidity and mortality among children with sickle cell anemia. Stroke can affect as many as 30% of children with this condition and can manifest clinically in 11% of all patients with sickle cell anemia. Stroke also manifests as silent cerebral infarction on MRI in another 17%-22% of patients. The risk for overt stroke for children with sickle cell anemia without primary stroke prophylaxis is more than 200-fold higher than in the general population; this risk may be even higher in adults.
Silent cerebral infarct can occur as early as the first year of life, and its prevalence increases with age. Approximately 40% of adolescents with sickle cell anemia have silent cerebral infarcts, and adults are likely continue to acquire new or enlarged silent cerebral infarcts. Cerebral infarcts tend to be ischemic in children and hemorrhagic in adult patients.
Well-documented risk factors for ischemic stroke in sickle cell anemia include prior transient ischemic attack, low steady-state hemoglobin levels, high white blood cell counts, hypertension, and a history of acute chest syndrome. However, the etiology of stroke in sickle cell anemia remains unclear. Aside from the absence of lipid deposition and plaque formation, many of the histopathologic findings in cerebrovascular lesions in sickle cell anemia resemble those found in stroke patients in the general population.
Cerebral infarcts in patients with sickle cell anemia are best detected by transcranial Doppler (TCD) ultrasonography, MRI, and magnetic resonance angiography (MRA). TCD ultrasonography is a reproducible and noninvasive method that aims to find narrowed internal carotid or middle cerebral arteries in asymptomatic children by detecting a signature high-flow pattern. Children with elevated blood flow velocities (≥ 200 cm/sec) have an astonishingly high rate of stroke: approximately 10,000 per 100,000 patient-years. TCD can reveal areas of high flow across the internal carotid artery and middle cerebral arteries that correspond to areas of stenosis; these are risk factors for stroke. Patients with abnormal MRA findings and higher blood-flow velocity on TCD ultrasonography are at an even higher risk for stroke.
Cerebral infarcts in patients with sickle cell anemia should be treated by exchange transfusion on diagnosis, with lifelong transfusion therapy. Exchange transfusion is an effective but possibly underutilized therapy in the acute and chronic treatment of sickle cell anemia. The aim is to maintain or reduce the hemoglobin S level to below 30%. It can provide needed oxygen-carrying capacity while reducing the overall viscosity of blood and thus reducing complications. It is mainly indicated in acute infarcted stroke, acute chest syndrome, multiorgan failure syndrome, the right upper quadrant syndrome, and possibly priapism.
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