Memory and learning in pediatric traumatic brain injury: a review and examination of moderators of outcome

Psychologists' Role in Concussion Assessments for Children and Adolescents in Pediatric Practice

An estimated 1.1 to 1.9 million children and adolescents in the United States are treated for a sports- or recreationally-related concussion each year. The importance of formalized assessment and measurement of concussion symptoms has been widely recognized as a component of best-practice treatment. The present paper reviews a sample of the most commonly used measures of concussion symptomology and explores psychologists' role in their application in a pediatric practice. In addition, other issues such as accessibility and the appropriateness of application with child and adolescent patients are discussed. Literature is reviewed from journals pertaining to pediatric and adolescent medicine, sports medicine, neuropsychology, and testing and measurement.

Pediatric traumatic brain injury and abusive head trauma

Childhood traumatic brain injury (TBI) commonly occurs during brain development and can have direct, immediately observable neurologic, cognitive, and behavioral consequences. However, it can also disrupt subsequent brain development, and long-term outcomes are a combination of preinjury development and abilities, consequences of brain injury, as well as delayed impaired development of skills that were immature at the time of injury. There is a growing number of studies on mild TBI/sport-related concussions, describing initial symptoms and their evolution over time and providing guidelines for effective management of symptoms and return to activity/school/sports. Mild TBI usually does not lead to long-term cognitive or academic consequences, despite reports of behavioral/psychologic issues postinjury. Regarding moderate to severe TBI, injury to the brain is more severe, with evidence of a number of detrimental consequences in various domains. Patients can display neurologic impairments (e.g., motor deficits, signs of cerebellar disorder, posttraumatic epilepsy), medical problems (e.g., endocrine pituitary deficits, sleep-wake abnormalities), or sensory deficits (e.g., visual, olfactory deficits). The most commonly reported deficits are in the cognitive-behavioral field, which tend to be significantly disabling in the long-term, impacting the development of autonomy, socialization and academic achievement, participation, quality of life, and later, independence and ability to enter the workforce (e.g., intellectual deficits, slow processing speed, attention, memory, executive functions deficits, impulsivity, intolerance to frustration). A number of factors influence outcomes following pediatric TBI, including preinjury stage of development and abilities, brain injury severity, age at injury (with younger age at injury most often associated with worse outcomes), and a number of family/environment factors (e.g., parental education and occupation, family functioning, parenting style, warmth and responsiveness, access to rehabilitation and care). Interventions should identify and target these specific factors, given their major role in postinjury outcomes. Abusive head trauma (AHT) occurs in very young children (most often <6 months) and is a form of severe TBI, usually associated with delay before appropriate care is sought. Outcomes are systematically worse following AHT than following accidental TBI, even when controlling for age at injury and injury severity. Children with moderate to severe TBI and AHT usually require specific, coordinated, multidisciplinary, and long-term rehabilitation interventions and school adaptations, until transition to adult services. Interventions should be patient- and family-centered, focusing on specific goals, comprising education about TBI, and promoting optimal parenting, communication, and collaborative problem-solving.

Controlled Cortical Impact Leads to Cognitive and Motor Function Deficits that Correspond to Cellular Pathology in a Piglet Traumatic Brain Injury Model

Traumatic brain injury (TBI) is a leading cause of death and disability in the United States, with children who sustain a TBI having a greater risk of developing long-lasting cognitive, behavioral, and motor function deficits. This has led to increased interest in utilizing large animal models to study pathophysiologic and functional changes after injury in hopes of identifying novel therapeutic targets. In the present study, a controlled cortical impact (CCI) piglet TBI model was utilized to evaluate cognitive, motor, and histopathologic outcomes. CCI injury (4 m/sec velocity, 9 mm depression, 400 msec dwell time) was induced at the parietal cortex. Compared with normal pigs (n = 5), TBI pigs (n = 5) exhibited appreciable cognitive deficiencies, including significantly impaired spatial memory in spatial T-maze testing and a significant decrease in exploratory behaviors followed by marked hyperactivity in open field testing. Additionally, gait analysis revealed significant increases in cycle time and stance percent, significant decreases in hind reach, and a shift in the total pressure index from the front to the hind limb on the affected side, suggesting TBI impairs gait and balance. Pigs were sacrificed 28 days post-TBI and histological analysis revealed that TBI lead to a significant decrease in neurons and a significant increase in microglia activation and astrogliosis/astrocytosis at the perilesional area, a significant loss in neurons at the dorsal hippocampus, and significantly increased neuroblast proliferation at the subventricular zone. These data demonstrate a strong relationship between TBI-induced cellular changes and functional outcomes in our piglet TBI model that lay the framework for future studies that assess the ability of therapeutic interventions to contribute to functional improvements.

Improving cognitive outcomes for pediatric stroke

PURPOSE OF REVIEW

The past 20 years have seen a 35% increase in prevalence of pediatric stroke. Contrary to widely held views, children do not recover better than adults. This review explores the impact of pediatric stroke on cognitive domains, including intellectual and executive functions, memory and behavior, and the influence of age, lesion characteristics, and comorbidities on outcome.

RECENT FINDINGS

Cognitive problems occur in up to half of ischemic and hemorrhagic stroke survivors. Single-center studies have shown intelligence quotient scores skewed to the lower end of the average range, with greater impairment in performance than verbal domains. Executive function, such as attention and processing speed are particularly vulnerable to the effects of pediatric stroke. Age at stroke, larger infarct size, cortical/subcortical lesion location, epilepsy, and comorbid physical deficits are associated with poorer cognitive outcomes.

SUMMARY

Cognitive impairment occurs relatively frequently following pediatric stroke but the nature, severity, and predictors of specific deficits are not well defined. Improving understanding of outcomes following pediatric stroke is a key priority for families but a paucity of data limits the ability to develop targeted disease, and age-specific pediatric rehabilitation strategies to optimize cognitive outcomes following pediatric stroke.

Ongoing daytime behavioural problems in university students following childhood mild traumatic brain injury

Sleep is often disrupted in traumatic brain injury (TBI) and may be related to persistent behaviour problems; however, little is known about this relationship in young adults. This study explored associations between TBI, behavioural problems and sleep disturbances in 247 university students (197 non-TBI, 47 mild TBI, two moderate TBI, one severe TBI) aged 18-25 years, who completed validated measures for behaviour, sleep quality and history of TBI. Because of small group numbers, participants reporting moderate to severe TBI were excluded from the analyses. Results indicated that students with mild TBI reported higher levels of daytime dysfunction, somatic complaints, withdrawal, other behavioural complaints and internalizing behaviours compared with students with no TBI history. A correlational analysis indicated a moderate relationship between the above significant variables. Our results suggest that university students with a history of mild TBI are more likely to experience certain ongoing daytime behavioural problems, which are likely to negatively influence their academic functioning in tertiary education. This study highlights the importance of research on long-term problems following mild TBI in young adults aged 18-25 years--an age group often overlooked within the literature.

Evaluation of an attention and memory intervention post-childhood acquired brain injury: Preliminary efficacy, immediate and 6 months post-intervention

OBJECTIVE

Impairments in attention and memory are common sequelae following paediatric acquired brain injury (ABI). While it has been established that such impairments are long-term and, therefore, affect quality-of-life, there is a scarcity of evidence-based interventions to treat these difficulties. The current study aimed to pilot the efficacy of the Amsterdam Memory and Attention Training for Children (Amat-c: English version) using both neuropsychological and ecologically sensitive measures. It was expected that children with attention and memory difficulties post-ABI would show improved performance post-intervention on cognitive and ecological measures, with maintenance at 6 months post-intervention.

METHODS AND PROCEDURES

Ten children with an ABI, between the ages of 8-13 years at the time of recruitment were identified through audits of presentations to a metropolitan paediatric hospital. Each child underwent screening, the 18 week intervention programme, pre-intervention, immediate and 6 month post-intervention assessments.

OUTCOMES/RESULTS

Findings supported the hypothesis that children would show post-intervention (immediate and 6 month) improvement in areas of attention and memory, with generalization to everyday life.

CONCLUSIONS/IMPLICATIONS

Preliminary results provide support for the efficacy of the Amat-c post-childhood ABI. A larger study is needed to confirm these findings, as a reduction in attention and memory difficulties will enhance everyday functioning.

Neuropsychological performance of youth with secondary attention-deficit/hyperactivity disorder 6- and 12-months after traumatic brain injury

The present study compared executive dysfunction among children with attention-deficit/hyperactivity disorder (ADHD) after traumatic brain injury (TBI), also called secondary ADHD (S-ADHD), pre-injury ADHD and children with TBI only (i.e., no ADHD). Youth aged 6-16 years admitted for TBI to five trauma centers were enrolled (n=177) and evaluated with a semi-structured psychiatric interview scheduled on three occasions (within 2 weeks of TBI, i.e., baseline assessment for pre-injury status; 6-months and 12-months post-TBI). This permitted the determination of 6- and 12-month post-injury classifications of membership in three mutually exclusive groups (S-ADHD; pre-injury ADHD; TBI-only). Several executive control measures were administered. Unremitted S-ADHD was present in 17/141 (12%) children at the 6-month assessment, and in 14/125 (11%) children at 12-months post-injury. The study found that children with S-ADHD exhibited deficient working memory, attention, and psychomotor speed as compared to children with pre-injury ADHD. Furthermore, the children with S-ADHD and the children with TBI-only were impaired compared to the children with pre-injury ADHD with regard to planning. No group differences related to response inhibition emerged. Age, but not injury severity, gender, or adaptive functioning was related to executive function outcome. Neuropsychological sequelae distinguish among children who develop S-ADHD following TBI and those with TBI only. Moreover, there appears to be a different pattern of executive control performance in those who develop S-ADHD than in children with pre-injury ADHD suggesting that differences exist in the underlying neural mechanisms that define each disorder, underscoring the need to identify targeted treatment interventions.

Evidence-based approaches to the management of cognitive and behavioral impairments following pediatric brain injury

Much is now known about the short- and long-term sequelae of pediatric acquired brain injury, with impairments found in general intellectual ability and in more specific domains, including attention, memory, executive functioning (e.g., planning and organization) and educational achievement (e.g., spelling and arithmetic). More recently, researchers have investigated behavioral, adaptive, social and mental health outcomes, and similarly, difficulties have been reported in these domains. While the availability of evidence-based treatments is currently limited, the need for the management of such sequelae has led to an emergence of research with a focus on the development and evaluation of management strategies and intervention programs in order to provide such treatment options.

Integration of synchronous synaptic input in CA1 pyramidal neuron depends on spatial and temporal distributions of the input

Highly synchronized neural firing has been discussed in relation to learning and memory, for instance sharp-wave activity in hippocampus. We were interested to study how a postsynaptic CA1 pyramidal neuron would integrate input of different levels of synchronicity. In previous work using computational modeling we studied how the integration depends on dendritic conductances. We found that the transient A-type potassium channel K(A) was able to selectively suppress input of high synchronicity. In recent years, compartmentalization of dendritic integration has been shown. We were therefore interested to study the influence of localization and pattern of synaptic input over the dendritic tree of the CA1 pyramidal neuron. We find that the selective suppression increases when synaptic inputs are placed on oblique dendrites further out from the soma. The suppression also increases along the radial axis from the apical trunk out to the end of oblique dendrites. We also find that the K(A) channel suppresses the occurrence of dendritic spikes. Moreover, recent studies have shown interaction between synaptic inputs. We therefore studied the influence of apical tuft input on the integration studied above. We find that excitatory input provides a modulatory influence reducing the capacity of K(A) to suppress synchronized activity, thus facilitating the excitatory drive of oblique dendritic input. Conversely, inhibitory tuft input increases the suppression by K(A) providing a larger control of oblique depolarizing factors on the CA1 pyramidal neuron in terms of what constitutes the most effective level of synchronicity. Furthermore, we show that the selective suppression studied above depends on the conductance of the K(A) channel. K(A) , as several other potassium channels, is modulated by several neuromodulators, for instance acetylcholine and dopamine, both of which have been discussed in relation to learning and memory. We suggest that dendritic conductances and their modulatory systems may be part of the regulation of processing of information, in particular for how network synchronicity affects learning and memory.

Ecological assessment of cognitive functions in children with acquired brain injury: a systematic review

BACKGROUND

Childhood acquired brain injury (ABI) often leads to impairment in cognitive functioning, resulting in disabilities in both the home and school environment. Assessing the impact of these cognitive deficits in everyday life using traditional neuropsychological tests has been challenging. This study systematically reviewed ecological measures of cognitive abilities available for children with ABI.

METHOD

Eight databases were searched (until October 2011) for scales: (1) focused on ecological assessment of cognitive functioning; (2) with published data in an ABI population; (3) applicable to children up to 17;11 years of age; and (4) in English. The title and abstract of all papers were reviewed independently by two reviewers.

RESULTS

Database searches yielded a total of 12 504 references, of which 17 scales met the inclusion criteria for the review, focusing on executive functions (n = 9), memory (n = 3), general cognitive abilities (n = 2), visuo-spatial skills (n = 2) and attention (n = 1). Four tasks used observation of actual performance in a natural environment, five were proxy-reports and six were functional paper and pencil type tasks, performed in an office.

CONCLUSION

Overall, few measures were found; eight were still experimental tasks which did not provide norms. Executive functions were better represented in ecological assessment, with relatively more standardized scales available.

Memory Disorders in Children With Central Nervous System Germ Cell Tumors

Memory disorders in children and adolescents with brain tumors are rare, but devastating to social, academic, and vocational development. Many pediatric patients with intracranial germ cell tumors (GCTs) complain of memory difficulties. This study investigated memory across a series of GCT patients. A total of 33 GCT patients were retrospectively examined for diagnosis, imaging results, intelligence quotient, treatment variables, evidence of increased intracranial pressure at diagnosis, and memory. The incidence of amnesia in GCT patients was 55%. Memory disturbance could not be predicted by intelligence quotient, treatment, location of lesion, or hydrocephalus at diagnosis. The high incidence of memory deficits in GCT patients suggests a risk to memory in patients with GCT. Formal memory assessment should be considered in all patients with central nervous system GCTs. Specific counseling and planning to assist in adjustment and to ensure safety should be considered standard care for those with memory deficits. The nurse should be instrumental in facilitating understanding of this specific injury in the brain tumor population.

Community integration following severe childhood traumatic brain injury

PURPOSE OF REVIEW

Severe childhood traumatic brain injury (TBI) is the leading cause of death and acquired disability in children, causing impairments in children's sensory-motor, cognitive and behavioural functioning, with devastating consequences on community integration. Community integration is the ultimate goal of rehabilitation; it is a complex outcome, with many variables contributing to it.

RECENT FINDINGS

Community integration and quality of life (QOL) are lower in children who sustained severe TBI at a younger age. Further, a wide range of injury-related, demographic and postinjury factors influence outcomes, and should serve as targets for specific interventions. An increasing number of interventions targeting cognitive, behavioural or family-related issues have been developed, with promising results.

SUMMARY

Children should benefit from early integrated patient and family-centred specific care, and receive long-term follow-up until early adulthood, with regular assessments, enabling detection and treatment of any emerging problem, and to ensure the acquisition of independent living skills and stable vocational outcome when this is possible. So far, few well conducted intervention studies are available, but their number is increasing with positive results on the trained skills. Well designed studies using large samples and looking at generalization of the skills in everyday life are needed.

High-mobility group box-1 impairs memory in mice through both toll-like receptor 4 and Receptor for Advanced Glycation End Products

High-mobility group box-1 (HMGB1) is a nuclear protein with cytokine-type functions upon its extracellular release. HMGB1 activates inflammatory pathways by stimulating multiple receptors, chiefly toll-like receptor 4 (TLR4) and Receptor for Advanced Glycation End Products (RAGE). TLR4 and RAGE activation has been implicated in memory impairments, although the endogenous ligand subserving these effects is unknown. We examined whether HMGB1 induced memory deficits using novel object recognition test, and which of the two receptor pathways was involved in these effects. Non-spatial long-term memory was examined in wild type, TLR4 knockout, and RAGE knockout mice. Recombinant HMGB1 (10μg, intracerebroventricularly, i.c.v.) disrupted memory encoding equipotently in wild type, TLR4 knockout and RAGE knockout animals, but affected neither memory consolidation, nor retrieval. Neither TLR4 knockout nor RAGE knockout mice per se, exhibited memory deficits. Blockade of TLR4 in RAGE knockout mice using Rhodobacter sphaeroides lipopolysaccharide (LPS-Rs; 20 μg, i.c.v.) prevented the detrimental effect of HMGB1 on memory. These data show that elevated brain levels of HMGB1 induce memory abnormalities which may be mediated by either TLR4, or RAGE. This mechanism may contribute to memory deficits under various neurological and psychiatric conditions associated with the increased HMGB1 levels, such as epilepsy, Alzheimer's disease and stroke.

Sensorimotor behavioral tests for use in a juvenile rat model of traumatic brain injury: assessment of sex differences

Modeling juvenile traumatic brain injury (TBI) in rodents presents several unique challenges compared to adult TBI, one of which is selecting appropriate sensorimotor behavioral tasks that enable the assessment of the extent of injury and recovery over time in developing animals. To address this challenge, we performed a comparison of common sensorimotor tests in Long-Evans rats of various sizes and developmental stages (postnatal days 16-45, 35-190 g). Tests were compared and selected for their developmental appropriateness, scalability for growth, pre-training requirements, and throughput capability. Sex differences in response to TBI were also assessed. Grid walk, automated gait analysis, rotarod, beam walk, spontaneous forelimb elevation test, and measurement of motor activity using the force-plate actometer were evaluated. Grid walk, gait analysis, and rotarod failed to meet one or more of the evaluation criteria. Beam walk, spontaneous forelimb elevation test, and measurement of motor activity using the force-plate actometer satisfied all criteria and were capable of detecting motor abnormalities in rats subjected to controlled cortical impact on postnatal day 17. No sex differences were detected in the acute effects of TBI or functional recovery during the 28 days after injury using these tests. This demonstrates the utility of these tests for the evaluation of sensorimotor function in studies using rat models of pediatric TBI, and suggests that pre-pubertal males and females respond similarly to TBI with respect to sensorimotor outcomes.

Regression-based pediatric norms for the brief visuospatial memory test: revised and the symbol digit modalities test

The Brief Visuospatial Memory Test - Revised (BVMTR) and the Symbol Digit Modalities Test (SDMT) oral-only administration are known to be sensitive to cerebral disease in adult samples, but pediatric norms are not available. A demographically balanced sample of healthy control children (N = 92) ages 6-17 was tested with the BVMTR and SDMT. Multiple regression analysis (MRA) was used to develop demographically controlled normative equations. This analysis provided equations that were then used to construct demographically adjusted z-scores for the BVMTR Trial 1, Trial 2, Trial 3, Total Learning, and Delayed Recall indices, as well as the SDMT total correct score. To demonstrate the utility of this approach, a comparison group of children with acute disseminated encephalomyelitis (ADEM) or multiple sclerosis (MS) were also assessed. We find that these visual processing tests discriminate neurological patients from controls. As the tests are validated in adult multiple sclerosis, they are likely to be useful in monitoring pediatric onset multiple sclerosis patients as they transition into adulthood.