Avaliação de sistemas cognitivos na anemia falciforme: estudo comparativo de crianças e adolescentes com e sem infartos cerebrais silenciosos

Abstract

Sickle cell disease is a chronic illness, considered as one of the greatest public health problems in Brazil. It occurs because of a genetic modification caused by the presence of an abnormal type of hemoglobin called hemoglobin S. Many clinical events may happen as this disease evolves. As it is a systemic and chronic disease with possible neurologic repercussions caused by cerebral involvement, the evaluation of patients cognitive development becomes necessary. Some studies have concluded that there are asymptomatic lesions in the central nervous system even in children early treated and that show no apparent neurologic changes. This study sought to evaluate the cognitive systems of 64 children and adolescents with sickle cell anemia who have not presented previous episodes of clinically manifested cerebral infarction, had been screened by the Minas Gerais Newborn Screening Program and been followed by Hemominas Foundation in Belo Horizonte. They were compared with 64 matched controls with no disease. Additionally, the cognition of the group with the disease was tentatively associated with silent cerebral infarcts detected through nuclear magnetic resonance. The group of patients had the worst scores in all WISC-III cognitive measures when compared to the control group. The average Full Scale IQ, Verbal IQ and Performance IQ was, respectively, 90.95 for the group with the disease and 113.97 for the control-group (p<0.001); 91.41 for the group with sickle cell anemia and 112.31 for the control group; 92.34 for the group with the disease and 113.38 (p<0.001) for the other. A statistically significant direct correlation between the socioeconomic level and the cognitive scores was detected. When the simultaneous influence of the disease by itself and of the socioeconomic level on those scores was evaluated, it was found that for the same socioeconomic level, children from the patients group had on average a total IQ of 21.2 points lower than the average of the control group children (p<0.001). This shows that the disease adjusted for the socioeconomic effect is a strong predictor of the total IQ. The incidence of silent cerebral infarcts in the patients group was of 31.2%. There was no statistically significant difference in the evaluation of cognitive systems between patients with infarcts and patients with no change detected through magnetic resonance imaging. In other words, children with sickle cell anemia without silent infarcts have showed much lower levels of cognitive scores than the control group. The magnitude of the effect was similar to that detected when comparing the whole group of patients with the control group. There was no statistically significant association between the basal average values of total hemoglobin, fetal hemoglobin, leukocyte count and reticulocyte count and the cognitive tests (P = 0.23; 0.58; 0.53 e 0.84, respectively). Patients who co-inherited a3.7 thalassemia (one of two HBA deleted genes) showed significantly lower cognitive scores than the children without the a3.7 thalassemia. In conclusion, cognitive loss of children with sickle cell anemia is remarkable and is present even in patients without silent infarcts. Therefore, it seems that an early preventive approach would be required for all children with sickle cell anemia so that innate levels of cognitive systems are preserved.