Thomas J. Farrer

Prevalence of Traumatic Brain Injury in the General Adult Population: A Meta-Analysis

Traumatic brain injury (TBI) is a significant public-health concern. To understand the extent of TBI, it is important to assess the prevalence of TBI in the general population. However, the prevalence of TBI in the general population can be difficult to measure because of differing definitions of TBI, differing TBI severity levels, and underreporting of sport-related TBI. Additionally, prevalence reports vary from study to study. In this present study, we used meta-analytic methods to estimate the prevalence of TBI in the adult general population. Across 15 studies, all originating from developed countries, which included 25,134 adults, 12% had a history of TBI. Men had more than twice the odds of having had a TBI than did women, suggesting that male gender is a risk factor for TBI. The adverse behavioral, cognitive and psychiatric effects associated with TBI coupled with the high prevalence of TBI identified in this study indicate that TBI is a considerable public and personal-health problem.

Prevalence of traumatic brain injury in incarcerated groups compared to the general population: A meta-analysis

Traumatic brain injury can cause numerous behavioral abnormalities including aggression, violence, impulsivity, and apathy, factors that can be associated with criminal behavior and incarceration. To better characterize the association between traumatic brain injury and incarceration, we pooled reported frequencies of lifetime traumatic brain injury of any severity among incarcerated samples and compared the pooled frequency to estimates of the lifetime prevalence of traumatic brain injury in the general population. We found a significantly higher prevalence of traumatic brain injury in the incarcerated groups compared to the general population. As such, there appears to be an association between traumatic brain injury and incarceration.

Heterogeneity of Brain Lesions in Pediatric Traumatic Brain Injury

OBJECTIVE Magnetic resonance imaging (MRI) provides a method to identify and quantify abnormalities resulting from traumatic brain injury (TBI). MRI abnormalities in children with TBI have not been fully characterized according to the frequency, location, and quantitative measurement of a range of pathologies critical for studies of neuropsychological outcome. Here, we report MRI findings from a large, multicenter study of childhood TBI, the Social Outcomes of Brain Injury in Kids (SOBIK) study, which compared qualitative and quantitative neuroimaging findings in 72 children with complicated mild-to-severe TBI to 52 children with orthopedic injury (OI). METHOD Qualitative analyses of MRI scans coded white matter hyperintensities (WMHs), hemosiderin deposits reflecting prior hemorrhagic lesions, regions of encephalomalacia and/or atrophy, and corpus callosum atrophy and traumatic shear lesions. Two automated quantitative analyses were conducted: (a) FreeSurfer methods computed volumes for total brain, white matter (WM), gray matter (GM), corpus callosum, ventricles, amygdala, hippocampus, basal ganglia, and thalamus along with a ventricle-to-brain ratio (VBR); and (b) voxel-based morphometry (VBM) to identify WM, GM, and cerebrospinal fluid. We also examined performance on the Processing Speed Index (PSI) from the Wechsler Intelligence Scale for Children, Fourth Edition, in relation to the above-mentioned neuroimaging variables. RESULTS WMHs, hemosiderin deposits, and focal areas of encephalomalacia or atrophy were common in children with TBI, were related to injury severity, and were mostly observed within a frontotemporal distribution. Quantitative analyses showed volumetric changes related to injury severity, especially ventricular enlargement and reduced corpus callosum volume. VBM demonstrated similar findings, but, in addition, GM reductions in the inferior frontal, basal forebrain region, especially in the severe TBI group. The complicated mild TBI group showed few differences from the OI group. PSI was significantly associated with global atrophy, as measured by VBR. CONCLUSION MRI findings after childhood TBI are diverse and particularly influenced by injury severity, and they involve common features, group heterogeneity, and individual variability.

Improving post-intensive care unit neuropsychiatric outcomes: understanding cognitive effects of physical activity.

Critical illness and its treatment often result in long-term neuropsychiatric morbidities. Consequently, there is a need to focus on means to prevent or ameliorate these morbidities. Animal models provide important data regarding the neurobiological effects of physical activity, including angiogenesis, neurogenesis, and release of neurotrophic factors that enhance plasticity. Studies in noncritically ill patients demonstrate that exercise is associated with increased cerebral blood flow, neurogenesis, and brain volume, which are associated with improved cognition. Clinically, research in both healthy and diseased human subjects suggests that exercise improves neuropsychiatric outcomes. In the critical care setting, early physical rehabilitation and mobilization are safe and feasible, with demonstrated improvements in physical functional outcomes. Such activity may also reduce the duration of delirium in the intensive care unit (ICU) and improve neuropsychiatric outcomes, although data are limited. Barriers exist regarding implementing ICU rehabilitation in routine care, including use of sedatives and lack of awareness of post-ICU cognitive impairments. Further research is necessary to determine whether prior animal and human research, in conjunction with preliminary results from existing ICU studies, can translate into improvements for neuropsychiatric outcomes in critically ill patients. Studies are needed to evaluate biological mechanisms, risk factors, the role of pre-ICU functional level, and the timing, duration, and type of physical activity for optimal patient outcomes.

Cognitive control in mild traumatic brain injury: Conflict monitoring and conflict adaptation

Recent studies suggest that individuals who have experienced a concussion or mild traumatic brain injury (TBI) show deficits in cognitive control. We tested the hypothesis that behavioral (response time [RT] and error rate) and electrophysiological (N450 and conflict SP components of the event-related potential [ERP]) reflections of conflict monitoring and conflict adaptation would be attenuated in 29 individuals with mild TBI compared to 36 control participants. Groups did not differ in age, sex, years of education, or neuropsychological test performance. Conflict monitoring and conflict adaptation can be seen when behavioral and ERP indices are reduced following high-conflict trials relative to low-conflict trials. Participants completed a Stroop task with 50% congruent and 50% incongruent trials. Behaviorally, both groups showed statistically significant conflict adaptation effects for RTs and error rates; these effects did not differ as a function of group. For ERPs, both groups showed more negative N450 and more positive conflict SP amplitudes on incongruent trials relative to congruent trials. Groups significantly differed in level of conflict adaptation for the conflict SP; controls showed significant conflict adaptation, whereas individuals with mild TBI did not. ERP amplitudes did not correlate with indices of injury severity or time since injury. Findings replicate and extend previous work that suggests the conflict SP is sensitive to conflict adaptation in healthy individuals, but is decreased in individuals across the range of TBI severity. Findings also suggest that mild TBI is associated with intact conflict monitoring, but altered conflict adaptation and adjustment processes.

Reaffirmed Limitations of Meta-Analytic Methods in the Study of Mild Traumatic Brain Injury: A Response to Rohling et al.

In 2009 Pertab, James, and Bigler published a critique of two prior meta-analyses by Binder, Rohling, and Larrabee (1997) and Frencham, Fox, and Maybery (2005) that showed small effect size difference at least 3 months post-injury in individuals who had sustained a mild traumatic brain injury (mTBI). The Binder et al. and Frencham et al. meta-analyses have been widely cited as showing no lasting effect of mTBI. In their critique Pertab et al. (2009) point out many limitations of these two prior meta-analyses, demonstrating that depending on how inclusion/exclusion criteria were defined different meta-analytic findings occur, some supporting the persistence of neuropsychological impairments beyond 3 months. Rohling et al. (2011) have now critiqued Pertab et al. (2009). Herein we respond to the Rolling et al. (2011) critique reaffirming the original findings of Pertab et al. (2009), providing additional details concerning the flaws in prior meta-analytic mTBI studies and the effects on neuropsychological performance.

Prevalence of traumatic brain injury in juvenile offenders: A meta-analysis

Studies of traumatic brain injury (TBI) among adult populations demonstrate that such injuries can lead to aggressive behaviors. Related findings suggest that incarcerated individuals have high rates of brain injuries. Such studies suggest that traumatic brain injury may be related to the etiology and recidivism of criminal behavior. Relatively few studies have examined the prevalence of TBI using a delinquent juvenile sample. In order to assess the relationship between TBI and juvenile offender status, the current study used meta-analytic techniques to examine the odds of having a TBI among juvenile offenders. Across 9 studies, we found that approximately 30% of juvenile offenders have sustained a previous brain injury. Across 5 studies that used a control group, a calculated summary odds ratio of 3.37 suggests that juvenile offenders are significantly more likely to have a TBI compared to controls. Results suggest that the rate of TBIs within the juvenile offender population is significant and that there may be a relationship between TBIs and juvenile criminal behavior.

Prevalence of Traumatic Brain Injury in Intimate Partner Violence Offenders Compared to the General Population A Meta-Analysis

Intimate partner violence (IPV) is widespread. Several risk factors are associated with IPV perpetuation, including alcohol use and educational level. The aggression and violence associated with traumatic brain injury (TBI) suggest that brain trauma may also be a risk factor for IPV. To examine the association between TBI and IPV, the authors conducted a meta-analysis of peer-reviewed published studies reporting the prevalence of TBI in IPV perpetrators. The authors compared the frequency of TBI among IPV perpetuators to estimates of TBI in the general population using a single-sample test of proportions. Six studies containing a total of 222 subjects met inclusion criteria. Fifty-three percent (119) of the IPV perpetuators had a history of TBI, a prevalence significantly higher (p < .0001) than estimates of TBI in the general population. The prevalence of TBI among perpetuators of IPV appears significantly higher than the prevalence of TBI in the general population. To the extent that this association is causal, TBI may be a risk factor for interpersonal violence, although comparatively few source studies, lack of standardized information about TBI severity, and the inability to investigate potential confounding variables necessarily limit this conclusion.

Performance Monitoring and Cognitive Control in Individuals with Mild Traumatic Brain Injury

Literature suggests that individuals with mild traumatic brain injury (mTBI) show subtle abnormalities in the cognitive control process of performance monitoring. The neural bases of performance monitoring can be measured using the error-related negaitivity (ERN) and post-error positivity (Pe) components of the scalp-recorded event-related potential (ERP). Thirty-six individuals with mTBI and 46 demographically similar controls completed a modified color-naming Stroop task while ERPs were recorded. Separate repeated-measures analyses of variance were used to examine the behavioral (response times [RT] and error rates) and ERP (ERN and Pe amplitudes) indices of performance monitoring. Both groups showed slower RTs and increased error rates on incongruent trials relative to congruent trials. Likewise, both groups showed more negative ERN and more positive Pe amplitude to error trials relative to correct trials. Notably, there were no significant main effects or interactions of group for behavioral and ERP measures. Subgroup and correlational analyses with post-concussive symptoms and indices of injury severity were also not significant. Findings suggest comparable performance to non-injured individuals in some aspects of cognitive control in this sample. Neuropsychological implications and comparison with other cognitive control component processes in individuals with TBI are provided.

Predictors of performance monitoring abilities following traumatic brain injury: the influence of negative affect and cognitive sequelae.

Performance monitoring is a cognitive control process modulated by both cognitive and affective variables. This study examined the relative contributions of negative affect (NA) and cognitive sequelae to performance monitoring dysfunction following severe traumatic brain injury (TBI). We used the error-related negativity (ERN) and post-error positivity (Pe) components of the event-related potential (ERP) to test the hypothesis that NA and cognitive sequelae would predict performance monitoring dysfunction beyond time since injury, and injury severity. Nineteen survivors of severe TBI completed neuropsychological tests, measures of NA, and a computerized Stroop task. Scores on NA and neuropsychological measures were standardized to form magnitude of cognitive sequelae and negative affect composite scores. Separate hierarchical regression analyses with ERN and Pe amplitudes as dependent variables and injury severity, time since injury, magnitude of cognitive sequelae, and NA as independent variables indicated that NA and cognitive sequelae significantly predicted ERN amplitude, with a larger relative contribution of NA than cognitive sequelae. Increased levels of NA were associated with decreased amplitude ERN. Cognitive sequelae, but not NA, predicted Pe amplitude. Injury severity and time since injury were not significant predictors. Results suggest that both NA and cognitive sequelae play critical roles in performance monitoring decrements following TBI and indicate a possible dissociation between the ERN and Pe, with the ERN more related to affective processes and the Pe to cognitive processes.