Dissociation between delayed alternation and memory after pediatric head injury: relationship to MRI findings

Neuroimaging Correlates of Functional Outcome Following Pediatric TBI

Neuroimaging plays an important role in assessing the consequences of TBI across the postinjury period. While identifying alterations to the brain is important, associating those changes to functional, cognitive, and behavioral outcomes is an essential step to establishing the value of advanced neuroimaging for pediatric TBI. Here we highlight research that has revealed links between advanced neuroimaging and outcome after TBI and point to opportunities where neuroimaging could expand our ability to prognosticate and potentially uncover opportunities to intervene.

Sport Contact Level Affects Post-Concussion Neurocognitive Performance in Young Athletes

OBJECTIVE

Contact level affects the incidence of sports-related concussion. However, the effects of contact level on injury severity and recovery are less clear and are the focus of this study.

METHOD

Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) for athletes aged 12-22 was performed at baseline (n = 10,907 for 7,058 athletes), after suspected concussion determined by physicians or athletic trainers (n = 5,062 for 4,419 athletes), and during follow-up visits (n = 3,264 for 2,098 athletes). Athletes played contact/collision (CC), limited contact (LC), and noncontact (NC) sports. Injury incidence, severity, and recovery were measured using raw and change from baseline neurocognitive test scores. Comparisons between groups used univariate analysis and multivariable regression controlling for demographic variables.

RESULTS

Compared to CC athletes, LC and NC athletes showed decreased suspected concussion incidence. At initial post-injury testing, all neurocognitive test scores were similar between groups except changes from baseline for processing speed were improved for LC compared to CC athletes. Upon follow-up testing, raw neurocognitive scores were better for NC compared to the contact collision athletes in verbal memory, processing speed, total symptom score, migraine cluster, cognitive cluster, and neuropsychiatric cluster scores. For change from baseline scores, LC athletes exhibited better performance on verbal memory, processing speed, and reaction time but also showed higher neuropsychiatric scores than CC athletes.

CONCLUSION

Neurocognitive scores between contact levels were similar at the first post-injury test. However, follow up showed many improved scores and symptoms for limited and NC sports compared to CC sports, which may indicate faster recovery.

Cognitive predictors of academic achievement in young children 1 year after traumatic brain injury

OBJECTIVE

To examine cognitive predictors of academic achievement in young children with traumatic brain injury (TBI) and orthopedic injury (OI) shortly after injury and 1 year postinjury.

METHODS

Participants included 3- to 6-year-old children, 63 with TBI (46 with moderate TBI and 17 with severe TBI) and a comparison group of 80 children with OI. Academic achievement was assessed approximately 1 and 12 months postinjury using three subtests from the Woodcock-Johnson Tests of Achievement-Third Edition and the School Readiness Composite from the Bracken Basic Concepts Scale-Revised. General intellectual functioning, memory, and executive functions were measured at the initial assessment using standardized tests.

RESULTS

Hierarchical linear regression was used to predict academic achievement at the initial and 1-year follow-up assessments. Memory and executive functions were significant predictors of academic achievement at both assessments after controlling for group membership and demographic variables. Executive function remained a significant predictor of some outcomes after taking general intellectual functioning into account. Predictive relationships did not vary across the TBI and OI groups. Similar results were obtained when regression analyses were completed with only TBI participants using the Glasgow Coma Scale score as a predictor, although memory and executive functioning were somewhat less robust in predicting academic achievement than before.

CONCLUSION

Memory and executive function predict academic achievement after TBI in preschool children, although some of the associations may be accounted for by general intellectual functioning.

Impairments in learning, memory, and metamemory following childhood head injury

OBJECTIVE

To assess postinjury changes in learning, memory, and metamemory abilities following childhood traumatic brain injury.

DESIGN

Prospective, longitudinal with 5 assessments made from baseline to 24 months postinjury.

PARTICIPANTS

A total of 167 children (aged 5-15 years) with traumatic brain injury (TBI; 64 severe, 55 moderate, and 48 mild).

METHODS

Children completed a judgment of learning task with 4 recall trials and made 3 metamemory judgments.

RESULTS

Relative to those with mild TBI, children with moderate or severe TBI performed worse at earlier times postinjury and had a greater change in performance over time. Performance for moderate and severe groups peaked at 12 months and the performance gap between them and mild TBI group increased slightly from 12 to 24 months. Traumatic brain injury severity did not affect initial study-recall trial performance, but groups did diverge in performance with repeated study. Greater TBI severity was associated with poorer performance on prospective metamemory judgments, but not retrospective judgments.

CONCLUSIONS

Traumatic brain injury severity affected prospective judgments of memory performance and learning strategies, but did not appear to affect either word retention or the forgetting of words over a delay. Implications for rehabilitation are discussed.

Deficits in analogical reasoning in adolescents with traumatic brain injury

Individuals with traumatic brain injury (TBI) exhibit deficits in executive control, which may impact their reasoning abilities. Analogical reasoning requires working memory and inhibitory abilities. In this study, we tested adolescents with moderate to severe TBI and typically developing (TD) controls on a set of picture analogy problems. Three factors were varied: complexity (number of relations in the problems), distraction (distractor item present or absent), and animacy (living or non-living items in the problems). We found that TD adolescents performed significantly better overall than TBI adolescents. There was also an age effect present in the TBI group where older participants performed better than younger ones. This age effect was not observed in the TD group. Performance was affected by complexity and distraction. Further, TBI participants exhibited lower performance with distractors present than TD participants. The reasoning deficits exhibited by the TBI participants were correlated with measures of executive function that required working memory updating, attention, and attentional screening. Using MRI-derived measures of cortical thickness, correlations were carried out between task accuracy and cortical thickness. The TD adolescents showed negative correlations between thickness and task accuracy in frontal and temporal regions consistent with cortical maturation in these regions. This study demonstrates that adolescent TBI results in impairments in analogical reasoning ability. Further, TBI youth have difficulty effectively screening out distraction, which may lead to failures in comprehension of the relations among items in visual scenes. Lastly, TBI youth fail to show robust cortical–behavior correlations as observed in TD individuals.

Neurocognitive outcomes and recovery after pediatric TBI: meta-analytic review of the literature

Traumatic Brain Injury (TBI) continues to be one of the leading causes of death and disability in the pediatric population. Although the literature on neurocognitive outcomes is relatively rich, studies vary significantly in the methods used to group subjects on several moderating variables, including age at injury, injury severity, and time since injury, making it difficult to combine and summarize the data for comparison. Further complicating this effort is the wide range of measures used to document functional outcomes in key neurocognitive domains. In this meta-analytic review, 28 publications (1988 to 2007) that met inclusion criteria were summarized based on three distinct injury severity and time post injury groups for 14 key neurocognitive domains. Effect sizes were calculated to reflect the extent to which the above groups differed in case-control and case-case studies, as well as address recovery based on longitudinal studies. To the best of our knowledge, this is the first published quantitative summary of the literature on neurocognitive outcomes after pediatric TBI. Limitations of the current state of the literature as well as recommendations for future studies are discussed.

Working memory and new learning following pediatric traumatic brain injury

Working memory (WM), the ability to monitor, process and maintain task relevant information on-line to respond to immediate environmental demands, is controlled by frontal systems (D'Esposito et al., 2006), which are particularly vulnerable to damage from a traumatic brain injury (TBI). This study employed the adult-based Working Memory model of Baddeley and Hitch (1974) to examine the relationship between working memory function and new verbal learning in children with TBI. A cross-sectional sample of 36 school-aged children with a moderate to severe TBI was compared to age-matched healthy Controls on a series of tasks assessing working memory subsystems: the Phonological Loop (PL) and Central Executive (CE). The TBI group performed significantly more poorly than Controls on the PL measure and the majority of CE tasks. On new learning tasks, the TBI group consistently produced fewer words than Controls across the learning and delayed recall phases. Results revealed impaired PL function related to poor encoding and acquisition on a new verbal learning task in the TBI group. CE retrieval deficits in the TBI group contributed to general memory dysfunction in acquisition, retrieval and recognition memory. These results suggest that the nature of learning and memory deficits in children with TBI is related to working memory impairment.

Neuroanatomic correlates of CVLT-C performance following pediatric traumatic brain injury

Traumatic brain injury (TBI) frequently results in memory problems, and the degree of memory impairment is related to injury severity and is commonly associated with lesions in frontal and temporal brain areas. This study examined the relationship among injury severity, brain lesions, and memory in children with moderate to severe TBI using Donders' (1999) 5-factor model of performance on the California Verbal Learning Test-Children's Version (CVLT-C). Seventy-six children underwent magnetic resonance imaging (MRI) scans 3 months post-TBI and testing 1 year post-TBI. Results showed injury severity (Glasgow Coma Scale) was not predictive of performance on 4 of the 5 factors. Volume of frontal and/or temporal brain lesions was significantly predictive of performance on 3 of the 5 factors. Unexpectedly, lesion volume outside these areas (extra-frontotemporal) was predictive of performance on all 5 factors. In contrast, Verbal IQ at 1 year was most strongly associated with preinjury factors (socioeconomic status and special education involvement), although extra-frontotemporal lesions also contributed to the variability in this measure. Results suggest that in children with moderate to severe TBI, extra-frontal/temporal lesions are predictive of memory outcome 1 year postinjury above and beyond initial severity or frontal/temporal contusions. This finding may relate to widespread diffuse axonal injury, which potentially disconnects brain circuits mediating memory following moderate to severe TBI.

Using path analysis to understand executive function organization in preschool children

There continues to be no consensus definition of executive functions. One way to understand different executive function components is to study abilities at their emergence, that is, early in development, and use advanced statistical methods to understand the interrelations among executive processes. However, to fully determine the constructs of interest, these methods often require complete data on a large battery of tasks, which are difficult to obtain with young children. Path analysis is an alternative statistical technique that requires only a single measure of each construct, yet still allows researchers to investigate complex relations among measures, to compare nested models, and to compare model fit across groups. Therefore, 117 preschool children (ages 2 years 8 months to 6 years 0 months) completed several executive function tasks. Path analysis was used to determine the relations between complex problem solving and working memory, inhibition, and set shifting processes. The best-fitting model included paths from working memory and inhibition to problem solving, and a correlation between working memory and inhibition. Interestingly, in younger children, inhibition was the strongest predictor of problem solving, whereas working memory contributed more strongly in older children. Suggestions for useful statistical methods to investigate the relations among executive functions in children are discussed.

Porteus Maze performance following traumatic brain injury in children

To investigate planning in traumatically brain injured children, the authors gave the Porteus Maze Test (PMT; S. D. Porteus, 1959) to 276 pediatric patients who had sustained a traumatic brain injury (TBI) at least 3 years previously. Sensitivity of the PMT to TBI severity, age at test, and volume of focal brain lesions detected by magnetic resonance imaging was also studied. The Peabody Picture Vocabulary Test-Revised (L. M. Dunn & L. M. Dunn, 1981) was also administered as a control measure. Results indicated that the PMT was highly sensitive to TBI severity and to volume of circumscribed prefrontal lesions. In contrast to the PMT data, receptive vocabulary was related to injury severity but not to discrete prefrontal lesions. Implications for mechanisms of cognitive deficit after TBI in children are discussed.

Volume of focal brain lesions and hippocampal formation in relation to memory function after closed head injury in children

OBJECTIVES

(1) A study of verbal learning and memory in children who had sustained a closed head injury (CHI) at least 3 months earlier. (2) To relate memory function to focal brain lesion and hippocampal formation volumes using morphometric analysis of MRI.

METHODS

A group of 245 children who had been admitted to hospital for CHI graded by the Glasgow coma scale (GCS), including 161 patients with severe and 84 with mild CHI completed the California verbal learning test (CVLT) and underwent MRI which was analysed for focal brain lesion volume independently of memory test data. Brain MRI with 1.5 mm coronal slices obtained in subsets of 25 patients with severe and 25 patients with mild CHI were analysed for hippocampal formation volume. Interoperator reliability in morphometry was satisfactory.

RESULTS

Severity of CHI and age at study significantly affected memory performance. Regression analysis showed that bifrontal, left frontal, and right frontal lesion volumes incremented prediction of various learning and memory indices after entering the GCS score and age into the model. Extrafrontal lesion volume did not contribute to predicting memory performance.

CONCLUSIONS

Prefrontal lesions contribute to residual impairment of learning and memory after severe CHI in children. Although effects of CHI on hippocampal formation volume might be difficult to demonstrate in non-fatal paediatric CHI, further investigation using functional brain imaging could potentially demonstrate hippocampal dysfunction.

Neurobehavioral recovery after pediatric head trauma: injury, pre-injury, and post-injury issues

This article reviews the most significant demographic, neurological, and psychosocial factors affecting the occurrence of and recovery from traumatic head injury (THI) in children and adolescents. Review of the available literature suggests that, as with adults, there is no compelling evidence for persistent neurobehavioral deficits after mild THI in children. In contrast, neurobehavioral deficits are common in children who have sustained moderate to severe THI. This article emphasizes that a long-term developmental perspective that considers in concert injury, pre-injury, and post-injury variables is needed for a proper appreciation of possible sequelae of pediatric THI. Specific pitfalls in forensic assessments of these children are reviewed. Empirical findings are presented to support the position that neuropsychological evaluations of children with THI that do not consider pre-injury status are likely to lead to misattribution errors. Clinical implications are illustrated with a case example.

Executive functioning in preschool children: performance on A-not-B and other delayed response format tasks

The A-not-B (AB) task has been hypothesized to measure executive/frontal lobe function; however, the developmental and measurement characteristics of this task have not been investigated. Performances on AB and comparison tasks adapted from developmental and neuroscience literature was examined in 117 preschool children (ages 23-66 months). Age significantly predicted performance on AB, Delayed Alternation, Spatial Reversal, Color Reversal, and Self-Control tasks. A four-factor analytic model best fit task performance data. AB task indices loaded on two factors with measures from the Self-Control and Delayed Alternation tasks, respectively. AB indices did not load with those from the reversal tasks despite similarities in task administration and presumed cognitive demand (working memory). These results indicate that AB is sensitive to individual differences in age-related performance in preschool children and suggest that AB performance is related to both working memory and inhibition processes in this age range.

Prediction of neurobehavioral outcome 1-5 years post pediatric traumatic head injury

OBJECTIVE

To examine the neurobehavioral status of children with traumatic head injury (THI) and to identify variables that predict outcome.

DESIGN

Retrospective chart review, with follow-up 1-5 years after injury. Outcome predictor variables were identified through stepwise regression analysis.

SETTING

Level one trauma center and pediatric rehabilitation program.

PATIENTS

71 Children with THI, selected from a four-year series of consecutive admissions.

MEASURE

Vineland Adaptive Behavior Scales-Survey Edition.

RESULTS

Significant predictors of better neurobehavioral status at follow-up included absence of a premorbid learning problem (p <.01), older age at injury (p <.01), and normal pupillary response (p <.001) and higher cerebral perfusion pressure (p <.0001) during critical care management.

CONCLUSIONS

Neurobehavioral outcome after THI is influenced by premorbid psychosocial variables as well as by critical care management.

Head injury in children

Trauma in the United States is the leading cause of death and disability in the pediatric population. Differences of age and development affect recovery and outcome following head injury. Mechanisms and pathophysiology of head injury are varied in both the pediatric and adult populations. Assessments of injury are varied and some measurements are more sensitive than others as well as more specific with regard to certain types of injury. Treatment and management should be tailored to each case in order to effect a positive outcome with respect to brain functioning. Aggressive intervention for prevention of primary and secondary injury must be continued and understanding of the impact of these injuries should provide for a brighter future for these patients.

Childhood traumatic brain injury: neuropsychological status at the time of hospital discharge

The present study examined the status at the time of hospital discharge of 22 children who had sustained moderate to severe closed head injuries. Despite an average length of stay of 46 days, on average the children performed significantly below normal on cognitive, memory, and motor tests. The children who did the worst were those who sustained their injuries riding in a vehicle, as opposed to being hit by a vehicle while walking or riding a bicycle. No reliable associations were found between neuroimaging data and cognitive measures; however, children whose scans showed more diffuse severe injury (e.g. white matter hemorrhages) performed more poorly than those who did not. Of further importance were detailed morphometric analyses of tissue quantity and ventricular volume that showed significantly increased ventricle to brain ratios (VBR) over a 3 to 4 week period following injury.

Neuropsychological consequences of traumatic brain injury in children and adolescents

The study of the relationship between neuroscientific information and cognitive function and dysfunction is clearly a widely expanding field. In particular, there has been a growing body of research on traumatic brain injury (TBI) in children and adolescents. This article conveys recent findings concerning cognitive outcomes, with a particular focus on age differences with TBI, suggests a relationship between specific learning disorders and brain dysfunction, addresses differential hemisphere functioning with TBI, and alludes to recent developments in assessment of TBI.

Brain imaging and behavioral outcome in traumatic brain injury

Brain imaging studies have become an essential diagnostic assessment procedure in evaluating the effects of traumatic brain injury (TBI). Such imaging studies provide a wealth of information about structural and functional deficits following TBI. But how pathologic changes identified by brain imaging methods relate to neurobehavioral outcome is not as well known. Thus, the focus of this article is on brain imaging findings and outcome following TBI. The article starts with an overview of current research dealing with the cellular pathology associated with TBI. Understanding the cellular elements of pathology permits extrapolation to what is observed with brain imaging. Next, this article reviews the relationship of brain imaging findings to underlying pathology and how that pathology relates to neurobehavioral outcome. The brain imaging techniques of magnetic resonance imaging, computerized tomography, and single photon emission computed tomography are reviewed. Various image analysis procedures, and how such findings relate to neuropsychological testing, are discussed. The importance of brain imaging in evaluating neurobehavioral deficits following brain injury is stressed.

Comparison of three measures of injury severity in children with traumatic brain injury

Eighty-six traumatically brain-injured children aged 6 to 15 years who were consecutively admitted to a pediatric Level I trauma center were recruited for participation in the study. A comprehensive battery of behavioral, cognitive, communicative, social, motoric, and neurological tests was administered to the children from 12 to 36 months postinjury. The performance of three severity indices, the Glasgow Coma Scale (GCS), the ASCOT probability of survival, and the head injury component of the Anatomic Profile, was compared with respect to their association with long-term outcomes in five neurological domains, as assessed by linear regression models. The ASCOT probability of survival was correlated to test scores in all five domains. The GCS and the head injury component of the Anatomic Profile were each correlated to outcome in only one domain. The ASCOT probability of survival, which includes coded variables for the GCS, systolic blood pressure, and respiratory rates on admission, as well as a measure of multisystem anatomic injury, was the most sensitive indicator of head injury severity and was associated with outcomes beyond survival and death in this population. Probability of survival is a promising brain injury severity index that may be useful in efforts to assess new medical and rehabilitative therapies for children with traumatic brain injury.

Verbal learning and memory following pediatric closed-head injury

In this study, verbal learning and memory following pediatric closed-head injuries (CHI) using the children's version of the California Verbal Learning Test (CVLT). Participants included 47 children, ages 5-16 yr, with a history of CHI, and 47 matched, noninjured controls. Children with CHI performed more poorly than controls on the CVLT, although their deficits varied qualitatively as a function of injury severity. Those with mild/moderate injuries performed as well as controls on learning trials, but they recalled proportionally fewer words after a delay (although their recognition was intact). Severely injured children demonstrated deficits in learning, delayed recall, and recognition, compared to controls. The groups did not differ in learning characteristics, but children with severe CHI exhibited more intrusions than controls. Pediatric CHI are associated with specific disturbances in verbal learning and memory similar to those of adults with CHI but different from those of children with other developmental and neurological disorders.