School of Psychology & Psychiatry, Monash University, Melbourne, Australia
Head of Psychology, Royal Childrens Hospital Mental Health; Director, Clinical Sciences Research, MCRI; Professorial Fellow, University of Melbourne
Traumatic Brain Injury (TBI) affects 1 in 5 children by 15 years of age, and accounts for over 3% of all hospital admissions. 1-3 Moreover, children under the age of five years are particularly over-represented in TBI statistics due to falls. 4, 5 Given the number of children affected, any residual deficits associated with TBI represent a major health and social problem. 6 However, despite the high prevalence of TBI during the pre-school period, the effects of TBI in this age group are very rarely studied. Indeed, the potential negative outcomes associated with early TBI are often overlooked because of a general assumption that younger children will spontaneously recover due to the plasticity of the developing brain. 7-9
Researchers have long debated the issue of early neuroplasticity (greater capacity of the brain to adjust to changes following injury) versus increased vulnerability following early TBI. But the prevailing view, particularly following very early injury, has been that the rapid developmental change that characterises the preschool period will be reflected in unlimited neuroplasticity. 10, 11 Further, this neuroplasticity will be reflected in greater recovery in children following TBI when compared to an adult with an injury of the same level of severity. In support of this line of thought, it has been observed that lesions in the adult brain are more likely to result in specific deficits compared to the infant brain. 12, 13 Increased sparing of function in the infant has been suggested as occurring either as a result of anatomical restructuring of the brain, or from a greater capacity of the child to develop compensatory skills. 14 However, as Giza and Prins 15 point out, the pathophysiology of TBI results in a multitude of processes that are disrupted, and while the developing brain may be more malleable, this is not universal to all areas of function. 15 Further, the effect of injury is influenced by the type of injury i.e. focal, unilateral, location of injury, severity and age at injury. Indeed, rather than being protective, early injury may lead to increased problems. Children who sustain severe injury at an early age have been reported to have greater deficits in cognitive and behavioural functioning when compared to older children. 16, 17 Taylor and Alden suggest the following moderate approach to the question of neuroplasticity; “The critical issue, therefore, is not whether there are sequelae, but the extent to which normal development is possible in spite of early brain insult.” 11
- While there is considerable capacity to recover following TBI in early childhood, this capacity is not universal to all functions.
- Neuroplasticity should not be interpreted as the ability to return to pre-injury function.
- Recovery will be influenced by the type and severity of injury, and the child’s environment.
- Early injury may lead to greater deficits in some areas of functioning.
Difficulties Assessing Normal Development for Pre-school TBI
While the position suggested by Taylor and Alden 11 is a reasonable response to the issues of neuroplasticity, there are a number of inherent difficulties that relate specifically to the pre-school population. For example, how will normal development be defined? Will it be variation from the “normal” population? Alternatively, will deficits be defined as a decrease in the child’s pre-injury potential? A major difficulty in assessing deficits in pre-school children is that unlike their older school aged counterpart, there is often no objective information regarding how the young person functioned prior to the injury. Further, with pre-school children, what is often being evaluated are deficits in potential, not decline in existing function. Indeed, a particular deficit may not be developmentally expected to emerge for some years following the injury, and it is only when the skill fails to emerge that the deficit is identified. For example, we would not expect a normally developing 2 year old to be able to appropriately plan their day, but it would be expected that this skill would begin to emerge along with the development of the pre-frontal cortex during the pre-adolescent period. This is problematic, because if there is a lapse in time between injury and when the skill would normally be expected to emerge, the deficit may not be recognised as being associated with the original injury event. 18-20
- Young children often have no objective pre-injury information on which to base an assessment of “deficits”.
- It is important to remember that with young children, what is being assessed is a reduction in potential not a reduction in existing skills.
- Absence of deficits at the time of injury does not mean that the pre-school child may not require rehabilitative support in the longer term. Deficits may become apparent over time as the skill fails to emerge.
- A long term approach and follow up assessment is required in the case of a pre-school child, with a particular emphasis on times of developmental transition (e.g., preschool – to – school).
Deficits associated with Pre-school TBI
Early childhood TBI is associated with a number of cognitive outcomes including deficits in memory, 21, 22 attention, 23, 24 intellectual functioning 23 and language acquisition 25, 26. For example, in a recent study, Catroppa and colleagues 27 examined adaptive functioning 10 years post-injury for a group of children with early TBI, and found evidence of poorer adaptive skills for those with more severe injury, regardless of injury severity, and behavioural difficulties. 27 Post-injury arithmetic skills were the most compromised in the longer term. Behavioural outcomes have also been reported, including difficulties with psychosocial functioning and evidence of increased psychiatric problems later in life.17, 28, 29
For example, in a recent study children who had been hospitalised for a mild TBI between ages 0-5 years were significantly more likely to have symptoms of ADHD (odds ratios 4.2), Conduct Disorder (odds ratio 6.2) and substance abuse (odds ratios 3.6) during adolescence. 29
The reported level of deficits following TBI varies depending on the severity of injury, and also for different skills. A number of factors potentially contribute to these differences. For example, it has been suggested that deficits following early injury are more likely to be associated with disruption to the skills that are in the process of development at the time of injury. 28, 30 Further, as mentioned earlier, particular skills may not be fully developed at the time of assessment, and deficits may only emerge when the skill fails to develop at the appropriate time, or if it develops more slowly. 31 In addition, as there are few standardized measures appropriate for the pre-school period, the majority of the scales used for assessing problems were developed for older children or even adults. Therefore, careful consideration is required when interpreting results of any testing for pre-school children including: a) age at injury; b) time since injury; c) developmental stage at time of injury; and d) developmental stage at time of assessment. Also, a major difficulty in assessing children during the pre-school period is difficulties with communication, particularly for very young pre-verbal children.
- Assessment of deficit should be based on the developmental stage of the child using information from the parents to determine loss of pre-injury function or deviation from population norms. Assessment at multiple time points post injury may be necessary to detect the full range of deficits – a longitudinal approach should be adopted.
- Skills in the process of development at the time of injury may show greatest deficit.
- Select tests appropriate for pre-school population.
- Communication skills may complicate assessment.
Difficulties with Communication
A major reason for the general lack of information regarding the effects of TBI in pre-school children may be because many children in this population are pre-verbal, making it difficult to assess injury severity and any post injury symptoms that might be predictive of ongoing problems. Further, because of their immaturity, younger children lack the cognitive and linguistic capacity to process and understand changes that may occur following injury, and have limited coping skills which may exacerbate any difficulties. When symptoms are not reported, it is relatively easy to assume that they do not exist.
One solution often used to overcome the difficulty in communicating with very young children is to employ assessments that are based on parental report. However, using parental report creates its own problems. For example, a recent study using parental report of concussive symptoms found that pre-school children were less likely than their school-aged counterparts to report symptoms such as dizziness, blurred vision, loss of memory and confusion, and were more likely to report loss of consciousness, fatigue, vomiting, feeling sick and feeling sleepy (McKinlay et al., In Press). However, the differences in symptom report were most likely due to the fact that only easily observed or overtly communicated symptoms were reported for the younger children. Research suggests that significant others are more likely to report easily observed symptoms 5 for example aggression andimpulsivity than more internalized symptoms of anxiety or depression. Further, it is important to note that observable symptoms reported by the parents are not necessarily the most relevant in terms of predicting which children will have continuing problems.
Another solution might be to include objective measure such as behaviour, particularly in the early stages of recovery, which could be used to predict children at risk of ongoing problems. However, this approach allows only a very narrow range of deficits to be assessed.
- Communication skills are still developing in the pre-school period.
- A lack of communication skills may make symptoms and deficits difficult to assess.
- Clinicians need to be aware that parental report to support their assessment, may be biased and it may not provide accurate information.
- Inclusion of objective or observational measures may overcome problems of relying on parental report, but limits the skills that can be assessed.
Parental Reaction to the Injury Event:
An area that has received considerable attention in the general injury literature, but relatively little in the area of TBI, is the impact of the parental reaction on the outcomes of the injury event. 32, 33 The quality of parent-child interaction is a major predictor of emotional and social development of children in the first years of life. 34 This relationship may be disrupted by an injury event whereby the parent may become more protective, or react punitively. 35 For example, Patterson and colleagues of the Oregon Social Learning Centre have demonstrated that parents under stress are more likely to respond punitively to ‘acting out’ behaviours in their child. This in turn develops and maintains children's ‘acting out’ behaviours, and the parents’ critical or coercive responses. 35, 36 In children who have experienced a TBI, the initial symptoms are commonly an increase in irritability and lack of compliant behaviour (acting out). 37-39 The parents themselves have experienced a stressful event, increasing the likelihood of a punitive response, and thereby beginning a negative parent-child interactive style that may result in unnecessary ongoing or exacerbated negative outcomes.
Negative Cycle developed Following Injury
Figure 1: Schematic showing the potential pathways for the development of negative behaviour following mTBI (represented by red lines).
- Children, particularly very young children, are immersed in the family system and rely on parental coping for aspects of their recovery.
- It is important to assess the parents’ reaction to their child’s injury event.
- Parental stress may negatively impact on the injury outcome.
Recovery from TBI that occurs during the preschool period poses challenges that are not present in older children and adults. While the pre-school period is a time of rapid neuronal change, the neuroplasticity associated with early development is not universal to all functions, nor should it be interpreted as the ability to return to pre-injury state. Recovery will be influenced by the type and severity of injury. Evaluating deficits for young children can be complicated by communication difficulties and the fact that young children often have no objective pre-injury information on which to base an assessment of “deficits”. Further, an absence of deficits during the acute period should be interpreted cautiously, as the extent of problems may only become apparent over time as expected skills fail to emerge. Children, particularly very young children, are immersed in the family system and rely on parental coping for aspects of their recovery. It is important to be aware that when one member of the system is compromised the entire system may be placed under strain, requiring interventions and rehabilitation plans that take into account not only the injured child’s needs, but also those of the siblings and parents.
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