Abstract
Background: Traumatic brain injury (TBI) is the most common cause of death in children in the U.S. One may not see immediate consequences of TBI on cognition in children however the effects may become visible as the child gets older. This can create lifetime deficits in children as well as affect their families. This paper investigates whether mild traumatic brain injuries (MTBI) in children have an effect on executive function.
Hypothesis: It is hypothesized that children with MTBI have lower school performance as compared to those who do not have any MTBI.
Methods: The electronic database pubmed.gov was searched for primary literature using key search terms including “mild traumatic brain injury”, “concussion”, “children”, “kids”, “executive functions”, “sports”, “cognition”.
Results: 7 out of the 9 studies analyzed showed significant deficits in various aspects of executive function for up to 2 years post injury.
Conclusion: These findings suggest that deficits in executive function may have debilitating long-term consequences on a child’s performance at school.
Word count: 162
Keywords: mild traumatic brain injury, children, concussion, executive function, school, performance
Ultra mini abstract: Deficits in executive function following mild traumatic brain injury in children can be seen as long as 2 years post injury and thus can negatively impact their performance in school.
Introduction:
Accidents and injuries are the most common cause of death in kids and teenagers in the United States (Hung et. al., 2014). Of these, traumatic brain injury (TBI), or concussion is a very common type of injury in children and youth younger than 18 years of age. TBI is caused by traumatic biomechanical forces to the brain via a direct or indirect blow to the head, neck (Lax et al., 2015). Statistics show that approximately 3.8 million TBI occur annually in the United States, majority in children and young adults (Langlois, 2006). The annual incidence of TBI is about 180 per 100,000 children (Altermatt, 2002).
TBI can have short and long term effects on brain function such as cognitive impairment, behavioral changes, motor deficits, and headache, sleep disturbance, fatigue, irritability, memory and concentration problems etc. (Hung et al, 2014). One may not see immediate consequences of TBI on cognition in children however the effects may become visible as the child gets older. This can create lifetime deficits in children as well as affect their families. (Brain injury association of America, 2017). Some children may have debilitating physical and cognitive deficits throughout their life.
Executive functions can be defined as “a complex group of cognitive processes of control and integration involved in the implementation of goal-directed behavior” (Chan, Shum, Toulopoulou & Chen, 2008). Thus, executive function is a broad umbrella term that encompasses other cognitive components such as attention, decision-making, and reasoning, cognitive flexibility, initiating a task and inhibiting unwanted information. (Chan et al., 2008). Damage to frontal brain structures can lead to impairment of executive functions and can directly affect performance at school and every day life. The frontal and temporal cerebral structures, due to their vicinity to bony structures such as the anterior and middle fossa, are more susceptible to impact from TBI (Bigler, 2007). Executive functions have shown to be an important determinant for performance at school including being prepared for school and achievements at school (Blair and Razza, 2007). In 2000, Miyake, Friedman, Emerson, Witzki and Howerter investigated the executive functions and found three separate components to these executive functions: working memory, inhibition and switching/shifting. This model is widely accepted and useful for research in children (Lehto, Juujarvi, Kooistra and Pulkkinen, 2003). According to Miyake et al., working memory is important for decision-making, problem solving and proper reasoning. It the ability to continuously manipulate newly acquired memory to aid in decision-making processes. Inhibition is the ability to successfully suppress distractors or impulses or knowledge that is irrelevant to the task at hand in order to complete it successfully. Switching refers to the ability to flexibly switch attention between different tasks i.e. to not be fixated on a particular task. Although this model is highly used in research, other factors included in the umbrella term of “executive functions” include language, learning, memory, motor coordination, problem solving, thought, planning, etc. (Loher et. al., 2014). Development of executive function begins in infancy and extends into adolescence but complete development is not reached until late adolescence. However, noticeable development is observed in childhood in the primary school years (Diamond, 2006). Therefore, the executive function development time from childhood to adolescence is particularly important for research on pediatric acquired brain injuries like TBI because the injury happens at a time when the development of these brain structures is still ongoing. Because childhood and adolescence are periods during which the brain has the greatest plasticity and growth, it is now thought that the young brain may be more susceptible to TBI causing delayed recovery and deficits (Anderson et. al., 2005). In 2004, the World Health Organization (WHO) reported a good prognosis for children with mild TBI (Carroll et. al., 2004). The WHO found that post concussion symptoms were temporary and resolved within 3 months. The study showed that very few kids have short or long term cognitive deficits and that children with mTBI did not subsequently have a higher rate of behavioral or school problems than children with other type of injuries. However, little information exists specific to the long-term cognitive outcomes of mTBI in children and their performance in school. The purpose of this study was to evaluate whether children, ages 1-18 years, with mild traumatic brain injury have lower school performances compared to children with no traumatic brain injury by measuring their executive function outcomes over 2 years. It was hypothesized that children with mTBI will have long-term deficits in executive function and thus lower school performance as compared to children with no mTBI.
Methods:
The electronic database pubmed.gov was searched. The search terms used included “mild traumatic brain injury”, “concussion”, “children”, “kids”, “executive functions”, “sports”, “cognition”.
The inclusion criteria included publications from the last 15 years. Most recent publications were preferred. Primary literature was the main type of evidence used. Only studies with subjects that were children between the ages of 1-18 years were considered. Large cohorts were preferred.
The exclusion criteria involved meta-analysis or peer reviews. Literature past 15 years was not included. Studies looking at subjects with prior history of mental health problems were excluded. Studies analyzing effects of multiple or recurrent concussions or mTBIs in children were excluded. Studies looking at adult populations i.e. greater than 18 years of age were excluded. Studies on subjects with a Glasgow Coma Scale of less than 13 (i.e. moderate and severe TBI) with visible structural changes on MRI excluded.
Definitions:
mTBI was defined as an “acute brain injury resulting from mechanical energy to the head from external forces.” (Carroll LJ, 2004). mTBI was identified via a fixed criteria. The symptoms should include disorientation or loss of consciousness for 30 minutes or less. Other symptoms such as focal neurological signs, seizures, or amnesia for less than 24 hours can also be seen (Carroll LJ, 2004). Clinically, a Glasgow Coma scale score of 13-15 after 30 minutes post injury or later upon presentation to the hospital is suggestive of mTBI. These symptoms of mTBI must not be caused by drugs, alcohol, and medications or caused by other injuries or treatment of other injuries (Carroll LJ, 2004).
Results:
The studies that were analyzed, assessed the course of post concussion symptoms, specifically different aspects of executive functions for varying length of times post injury. All of the studies were prospective cohort studies that looked at the children within varying age groups. The youngest age group analyzed was 5 years and the oldest was 17 years. Participants were included in the study under the mild TBI category if they had a Glasgow Coma Scale of 13-15 or loss of consciousness for 30 min or less. Some studies further subcategorized mTBI as complicated (i.e. some structural changes were seen on MRI) and non complicated (i.e. no structural changes seen on MRI). Most studies analyzed the executive functions via standardized neuropsychiatric assessment tests such as Wechsler Intelligence Scale for Children –III (WISC-III); Intellectual functioning (Wechsler Abbreviated Scale of intelligence (WASI); Stroop Color-Word Interference Task, behavior rating inventory of executive function (BRIEF) etc. The control groups were either healthy children matched for demographic variables such as age and sex (Moore et. al., 2016). Some studies used children with other orthopedic injuries without any trauma to the brain as control groups (Shultz E.L. et al., 2016). Some studies used pre-injury parent ratings of executive function as controls (Anderson et. al., 2012). The shortest study analyzed children for 1 month (Crowe et. al., 2015), while the longest study was 2.5 years (Shultz et. al., 2016).
The following table (Table 1) shows the studies that were analyzed, their study design, study population, type of outcome assessments chosen, and their conclusion along with statistics in order of longest to shortest time post injury.