Traumatic brain injury (TBI) accounts for substantial morbidity in children and adolescents in the United States [1
]. Approximately 1,000,000 children sustain TBI annually, with an overall incidence of 200–300 per 100,000 children. Incidence varies as a function of injury severity, with 80 to 90 % of TBI being classified as mild[3
]. Despite its common occurrence in the pediatric population, controversy persists regarding the outcomes of mild TBI in children [4
]. Reviews of the literature [4
] find little evidence for long-term adverse cognitive outcomes. However, important conceptual and methodological shortcomings characterize much of the existing research on pediatric mild TBI [6
Executive dysfunction is one of the hallmark outcomes of TBI [1
]. Executive functions involve a complex, environmentally sensitive set of interrelated processes that are responsible for purposeful, goal-directed, problem-solving behavior [10
]. They also refer to the ability to consciously control one's cognitive activities and to monitor and regulate one's affect and behavior. These functions are important for success in “real world” environments, including school. A deficit in the executive domain following TBI is likely to affect cognitive, social, and emotional functioning [8
Although executive dysfunction has been well described following moderate to severe TBI in childhood [8
], less is known about mild TBI. Although a number of studies of various aspects of executive functions (e.g. flexibility, inhibition, goal setting, planning, working memory) did not report significant deficits following mild TBI in children [16
], others did find noticeable executive difficulties, particularly on measures of working memory [21
]. Working memory is an aspect of executive function often considered sensitive to TBI [1
]. It refers to the process of holding information in mind for the purpose of completing a related task and involves both the storage and manipulation of information [17
]. Levin et al [22
] documented reduced working memory in children with mild TBI and abnormal CT findings relative to children without abnormal CT findings during the first year post-injury. Thus, mild TBI in children may be associated with deficits in executive functions, at least for so-called “complicated” injuries.
All of the above studies have typically used performance-based tests to examine executive functioning [24
]. The ecological validity of such tests may be limited, in that they may not be predictive of day-to-day functioning. Indeed, the nature of standardized testing (i.e., distraction free, highly structured) may mask executive dysfunction, thereby reducing the opportunities to observe critical processes associated with executive functions [25
]. Thus, performance-based tasks may overestimate the child's competence in everyday tasks [1
]. Despite the apparent absence of deficits on cognitive measures of executive functions following mild TBI, patients and parents often report post-concussive symptoms such as distractibility, inattention, and forgetfulness, suggestive of executive deficits [26
Rating scales provide an alternative approach to assessing executive functions that may tap everyday behavior more readily [8
]. The Behavior Rating Inventory of Executive Function (BRIEF;[30
]) is a standardized rating scale that was developed with ecological validity in mind, because it was meant to assess children's everyday executive behaviors in natural settings (e.g., behavioral inhibition, emotional regulation, working memory and planning). The questionnaire enables parents to rate their children's executive behaviors at home and in the community. Studies have found the BRIEF to be valid and reliable both in typically developing and children with TBI [10
]. Mangeot et al [8
] found that children with moderate to severe TBI displayed more deficits in executive functions on the BRIEF relative to children with orthopedic injuries approximately 5 years after injury. The magnitude of group differences did not vary across the BRIEF subscales, suggesting a generalized pattern of executive deficits. In their study, standardized cognitive tests of executive function demonstrated modest but significant associations with parent ratings on the BRIEF.
Very little research using the BRIEF has been conducted with children with mild TBI. We could find only one previous study, by Sesma et al [1
], which showed that children with mild, moderate and severe TBI were all rated by parents as having significantly more executive dysfunction on the BRIEF General Executive composite, Behavioral Regulation, and Metacognition summary scores 12 months after injury as compared to children with orthopedic injuries. The working memory subscale was the only domain that demonstrated significant differences between the control group and all three TBI severity groups at 3 and 12 months after injury. The proportion of children with mild TBI who were rated as having significant executive dysfunction doubled by 3 months after injury and remained at a similar level 12 months after injury. Although the results are noteworthy, they may not be representative of the broader population of children with mild TBI, because all of the participants were hospitalized.
The overall goal of the present study was to examine cognitive and behavioral aspects of executive functioning in children with mild TBI up to 1 year post-injury. We relied on data collected as part of a larger prospective, longitudinal study of children injured between the ages of 8 and 15. Participants included children with mild TBI and a comparison group of children with orthopedic injuries (OI) not involving the head who were recruited prospectively from admissions to emergency departments at two large children's hospitals. They were administered two subtests from the Cambridge Neuropsychological Testing Automated Battery (CANTAB [31
]) to assess cognitive aspects of executive functions (i.e., working memory and planning) and the BRIEF to assess executive functions in everyday life.
Our primary aim in this study was to determine whether the mild TBI and OI groups differed on cognitive or behavioral aspects of executive function. Because the differentiation of complicated versus uncomplicated mild TBI has been related to outcomes in the adult and pediatric populations [32
], we also wanted to determine whether indices of severity (i.e., loss of consciousness or MRI abnormalities) were related to executive dysfunction in our sample of children with mild TBI. Our second aim was to determine whether cognitive tests of executive function were predictive of behavior ratings of executive functions. Previous research has demonstrated a modest but significant relationship between standardized cognitive tests and behavior ratings, suggesting that the two types of measures tap related but distinct constructs [8