Plasticity is an intrinsic property of the central nervous system, reflecting its capacity to respond in a dynamic manner to the environment and experience via modification of neural circuitry. In the context of healthy development, plasticity is considered beneficial, facilitating adaptive change in response to environmental stimuli and enrichment, with research documenting establishment of new neural connections and modification to the mapping between neural activity and behaviour. Less is known about the impact of this plasticity in the context of the young, injured brain. This review seeks to explore plasticity processes in the context of early brain insult, taking into account historical perspectives and building on recent advances in knowledge regarding ongoing development and recovery following early brain insult, with a major emphasis on neurobehavioural domains. We were particularly interested to explore the way in which plasticity processes respond to early brain insult, the implications for functional recovery and how this literature contributes to the debate between localization of brain function and neural network models. To this end we have provided an overview of normal brain development, followed by a description of the biological mechanisms associated with the most common childhood brain insults, in order to explore an evidence base for considering the competing theoretical perspectives of early plasticity and early vulnerability. We then detail these theories and the way in which they contribute to our understanding of the consequences of early brain insult. Finally, we examine evidence that considers key factors (e.g. insult severity, age at insult, environment) that may act, either independently or synergistically, to influence recovery processes and ultimate outcome. We conclude that neither plasticity nor vulnerability theories are able to explain the range of functional outcomes from early brain insult. Rather, they represent extremes along a ‘recovery continuum’. Where a child’s outcome falls along this continuum depends on injury factors (severity, nature, age) and environmental influences (family, sociodemographic factors, interventions).

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.

Until recently, the impact of early brain insult (EBI) has been considered to be less significant than for later brain injuries, consistent with the notion that the young brain is more flexible and able to reorganize in the context of brain insult. This study aimed to evaluate this notion by comparing cognitive and behavioural outcomes for children sustaining EBI at different times from gestation to late childhood. Children with focal brain insults were categorized according to timing of brain insult, represented by six developmental periods: (i) Congenital (n = 38): EBI: first–second trimester; (ii) Perinatal (n = 33); EBI: third trimester to 1 month post-natal; (iii) Infancy (n = 23): EBI: 2 months–2 years post-birth; (iv) Preschool (n = 19): EBI: 3–6 years; (v) Middle Childhood (n = 31): EBI: 7–9 years; and (vi) Late Childhood (n = 19): EBI: after age 10. Groups were similar with respect to injury and demographic factors. Children were assessed for intelligence, academic ability, everyday executive function and behaviour. Results showed that children with EBI were at increased risk for impairment in all domains assessed. Furthermore, children sustaining EBI before age 2 years recorded global and significant cognitive deficits, while children with later EBI performed closer to normal expectations, suggesting a linear association between age at insult and outcome. In contrast, for behaviour, children with EBI from 7 to 9 years performed worse than those with EBI from 3 to 6 years, and more like those with younger insults, suggesting that not all functions share the same pattern of vulnerability with respect to age at insult.

BACKGROUND AND OBJECTIVES: Childhood traumatic brain injury (TBI) has implications for functional outcomes, but few studies have documented long-term outcomes. The purpose of this study was to plot recovery of cognitive and functional skills after early childhood TBI to 10 years postinjury and to identify the contribution of injury, environment, preinjury characteristics, and acute functional recovery. METHODS: Subjects were recruited consecutively to this prospective, longitudinal study, which used a between-factor design, with injury severity as the independent variable. Forty children with TBI aged 2 and 7 years were recruited on admission to a tertiary pediatric hospital, divided according to injury severity, and compared with 16 healthy controls acutely and 12 and 30 months and 10 years postinjury. Cognition, adaptive ability, executive function, and social/behavioral skills were examined. RESULTS: Children with severe TBI had poorest outcomes, with deficits greatest for cognition. Recovery trajectories were similar across severity groups but with significant gains in verbal skills from 12 and 30 months to 12 months and 10 years. Predictors of outcome included preinjury ability (for adaptive function) and family function (social/behavioral skills). CONCLUSIONS: Results confirm a high risk of persisting deficits after severe TBI in early childhood. Children with less severe TBI appear to recover to function normally. Contrary to speculation about “growing into deficits,” after protracted recovery to 30 months, young children make age-appropriate progress at least to 10 years postinsult. Environmental factors were found to contribute to adaptive and social/behavioral recovery.

Only a handful of studies have attempted to explore very long-term outcomes from childhood traumatic brain injury (TBI). These studies have generally failed to fully consider the impact of injury severity or employ measures sensitive to the survivor's day-to-day function. This study examined outcomes in adulthood, with a focus on functional abilities including education, employment, and quality of life (QOL), and employed predictors including injury severity, age at injury, socioeconomic factors, intelligence, and personality. The study was retrospective and cross-sectional and included 50 adult survivors of child TBI (31 males), aged 19-30 years at evaluation (M = 24.2, SD = 3.6), with injury on average 13.3 years prior to evaluation. Participants were divided according to injury severity-mild (n = 20), moderate (n = 12), and severe (n = 18)-completed an intellectual evaluation and questionnaires regarding educational and employment status, personality, and quality of life. Intellectual and personality measures indicated good outcomes, with mean scores for all groups in the average range and few severity-based findings. In contrast, those with more severe TBI were more likely to have educational and employment problems. QOL was significantly reduced in the context of severe insult, with lower IQ and personality factors most predictive of outcome in this domain. Mild and moderate TBI were generally more benign. Findings suggest that, while TBI is a lifelong problem, its impact is most dramatic in the domain of QOL, where a complex interaction occurs between injury factors, cognition, and personality.