Mild Head Injuries in Preschool-Aged Children: Do Young Brains Really Bounce?

Abstract

This thesis investigates the effects of mild head injuries (MHls) on the cognitive development of young children. The epidemiology of children's head injuries and information concerning their early course are presented. Studies of the outcome of mild, moderate and severe childhood closed-head injuries (CHls) are reviewed and considered from a developmental perspective. Evidence for and against the hypothesis that young children are more resilient to brain injury than older children and adults is presented. Studies that have investigated age effects for the sequelae of childhood head injuries are reviewed. Some methodological issues inherent to the study of head injuries in children are identified and discussed. These include the difficulties faced when assessing young children, whether children who have head injuries differ premorbidly from those who do not, and defining the severity and outcome of head injuries in children. Seventy-eight children who sustained (MHls) between 2.5 and 4.5 years of age were studied prospectively and their cognitive development compared with 86 control children of similar ages who sustained accidental injuries not involving the head. The children were assessed within a month of injury, six and twelve months later and then at the age of 6.5 years. Outcome was generally very good with no differences detected between the groups in behaviour and expressive and receptive language. However, six and twelve months after injury, the MHI children had slipped significantly behind the control children in their performance on a Visual Closure task that involved the rapid analysis of visual information. Mildly head-injured girls had also lost their gender advantage over boys on a visual memory task that involved sequencing. Mildly head-injured children had an increased risk for repeat MHIs for 6 months after injury. By 6.5 years of age there was no difference between the groups for reading ability but 30% of the MHI children had received remedial assistance for reading compared with 12% of the control children. The delay on the Visual Closure task remained and performance on this task a years after injury was predictive of reading performance at 6.5 years of age for the MHI but not the control children. The MHI girls continued to perform poorly on the Visual Sequential Memory task compared to the MHI boys. There were no differences between the groups in parent or teacher ratings of behaviour or incidence of injuries. The findings are discussed developmentally and in terms of skills that may have been disturbed. It is concluded that young children are not resilient to the effects of MHIs. The effects, however, were not reflected in immediate deficits but instead in subtle changes to the rate of development that only became evident with long-term follow up.