Context. Traumatic brain injury (TBI) is a common, acquired, childhood disability that may be used as a model to understand more completely the impact of early brain injury on both brain structure and day-to-day function. Contrary to previously held views of the "plasticity" of the young brain, recent research suggests that such early insults may have a profound impact on development. To date, these suggestions remain largely untested. Objectives. To plot changes in cognitive abilities after childhood TBI over the 30 months after injury and to examine the impact of age at injury on cognitive outcomes. Design. Prospective longitudinal study. Setting. Royal Children's Hospital, Victoria, Australia. Main Outcome Measures. Global intellectual ability, verbal and nonverbal skills, attention, and processing speed. Participants. A total of 122 children admitted to the hospital with a diagnosis of TBI were divided according to injury age, ie, young (age: 3-7 years) or old (age: 8-12 years), and injury severity (mild, moderate, or severe) and were evaluated acutely and at 12 and 30 months after injury. An additional sample of children injured before 3 years of age (n = 27) was compared with these groups with respect to global intellectual ability only. Results. A clear relationship was documented between injury severity and cognitive performance. For children who sustained severe injury, younger age at injury was associated with minimal, if any, recovery after injury, but better outcomes were observed after severe TBI among older children. Age at injury was not predictive of outcomes for children with mild or moderate TBI, although infants (age: 0-2.11 years) with moderate TBI showed poorer outcomes than did older children with injury of similar severity. Conclusions. Findings support a "double-hazard" model for severe and early brain insults and add to the ongoing debate regarding cerebral plasticity, suggesting that, contrary to traditional views, young children who sustain severe TBI in early childhood or moderate or severe TBI in infancy may be particularly vulnerable to significant residual cognitive impairment. From a clinical perspective, results indicate that long-term follow-up monitoring and management should be targeted to this high-risk group.
