A Case Series: Chiari Malformation and Sickle Cell Disease

Abstract Abstract 4772 Introduction: Chiari type I malformation is defined as tonsillar herniation of at least 3 to 5 mm below the foramen magnum. The prevalence of Chiari type I malformation in the general population is estimated to be 0.1 to 0.5%. In the SIT (Silent Infarct Transfusion) Trial in children with sickle cell disease, Chiari type I malformation was found as an incidental finding in 22 of 953 (2.3%) of the individuals imaged. Thus, the incidence of Chiari type I malformation in the SIT Trial appeared to be about five times greater than in the general population (Jordan et al Pediatrics 2010). Recently, four hemoglobin SS patients aged 6–17 years with and Chiari type I malformation were reported from one institution (Chonat el al J Pediatr Hematol Oncol 2011). Here we describe six sickle cell disease patients aged 17–24 years with Chiari type I malformation from two institutions. Discussion: All of the cases had severe sickling phenotype, either hemoglobin SS or sickle/B°thalassemia. The majority of the patients were experiencing neurologic symptoms that were subsequently attributed to Chiari type I malformation. Five of the six cases were eventually evaluated by neurosurgery. Neurosurgical intervention with posterior fossa decompression was recommended in four of these individuals. To date one patient has undergone surgery with relief of symptoms. Although Chiari type I malformation is thought to be primarily a congenital disorder, it has also been associated with disorders that are non-congenital. Individuals with sickle cell disease may have a thick calvarium as a result of erythroid hyperplasia and expansion of the diploe of the skull bones. Other conditions with severe anemia and thalassemia have been associated with increased thickness of the calvarium caused by diploic erythroid hyperplasia. One can question whether the increased thickness of the calvarium in some sickle cell patients results in craniocephalic disproportion with a subsequent acquired cerebellar ectopia, hence the increased Chiari type I malformation in patients with sickle cell disease. Central nervous system involvement in sickle cell disease is common. Any patient with sickle cell disease presenting with symptoms indicative of an ongoing or impending neurological event requires an in depth investigation and entails a broad differential. Chiari malformations may need to be part of this differential diagnosis. Disclosures: No relevant conflicts of interest to declare.