Methodological and statistical heterogeneity in studies combined in mTBI meta-analyses significantly limits the conclusions that can be drawn from small or non-significant overall effect sizes; clinically relevant information can be obscured by meta-analytic procedures. Recommendations for future meta-analytic studies of mTBI are offered.

Neural correlates of working memory (WM) based on the Sternberg Item Recognition Task (SIRT) were assessed in 40 children with moderate-to-severe traumatic brain injury (TBI) compared to 41 demographically-comparable children with orthopedic injury (OI). Multiple magnetic resonance imaging (MRI) methods assessed structural and functional brain correlates of WM, including volumetric and cortical thickness measures on all children; functional MRI (fMRI) and diffusion tensor imaging (DTI) were performed on a subset of children. Confirming previous findings, children with TBI had decreased cortical thickness and volume as compared to the OI group. Although the findings did not confirm the predicted relation of decreased frontal lobe cortical thickness and volume to SIRT performance, left parietal volume was negatively related to reaction time (RT). In contrast, cortical thickness was positively related to SIRT accuracy and RT in the OI group, particularly in aspects of the frontal and parietal lobes, but these relationships were less robust in the TBI group. We attribute these findings to disrupted fronto-parietal functioning in attention and WM. fMRI results from a subsample demonstrated fronto-temporal activation in the OI group, and parietal activation in the TBI group, and DTI findings reflected multiple differences in white matter tracts that engage fronto-parietal networks. Diminished white matter integrity of the frontal lobes and cingulum bundle as measured by DTI was associated with longer RT on the SIRT. Across modalities, the cingulate emerged as a common structure related to performance after TBI. These results are discussed in terms of how different imaging modalities tap different types of pathologic correlates of brain injury and their relationship with WM.

BACKGROUND:Recent evidence suggests that autonomic nervous dysfunction may be one of many potential factors contributing to persisting post-concussion symptoms.OBJECTIVE:This is the first systematic review to explore the impact of concussion on multiple aspects of autonomic nervous system functioning.METHODS:The methods employed are in compliance with the American Academy of Neurology (AAN) and PRISMA standards. Embase, MEDLINE, PsychINFO, and Science Citation Index literature searches were performed using relevant indexing terms for articles published prior to the end of December 2016. Data extraction was performed by two independent groups, including study quality indicators to determine potential risk for bias according to the 4-tiered classification scheme of the AAN.RESULTS:Thirty-six articles qualified for inclusion in the analysis. Only three studies (one Class II and two Class IV) did not identify anomalies in measures of ANS functioning in concussed populations.CONCLUSIONS:The evidence supports the conclusion that it is likely that concussion causes autonomic nervous system anomalies. An awareness of this relationship increases our understanding of the physical impact of concussion, partially explains the overlap of concussion symptoms with other medical conditions, presents opportunities for further research, and has the potential to powerfully inform treatment decisions.

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.

Previous research has reported lower cognitive test scores on baseline testing in athletes reporting multiple previous concussions or a history of learning disability (LD). Age also has an important influence on cognitive performance. While these factors have been considered individually in previous studies, the present study is the first to explore the interaction of age, self-reported LD, and history of concussion on baseline Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT®) in a nationwide study of adolescent athletes. ImPACT® was administered to 1823 Finnish male ice hockey players (aged 12-21 years old) prior to the 2015-2016 or 2016-2017 playing seasons. Linear regressions and simple slopes analyses were used for clarifying the impact of LD and previous concussion history on maturational trajectories. In comparison to typically developing athletes, athletes with LD had lower neurocognitive scores in all composites and differing maturational trajectory in verbal memory and visual motor speed. The number of previous concussions did not impair neurocognitive performance at baseline assessment. Application of standard age-based norms to adolescent athletes with a history of LD has the potential to negatively skew clinical decision-making. Separate reference values for LD athletes are warranted due to their unique developmental cognitive trajectories. The reference values for the Finnish participants in this study are presented.

The usefulness of on‐field signs in predicting concussion outcome is under debate. We studied the prevalence of these signs and analyzed the predictive value for post‐injury cognitive recovery in Finnish elite‐level youth ice hockey players. Of the 570 consecutive athletes, 52 were concussed during seasons 2015‐2017. After exclusion criterion analysis included 34 hockey players (14‐20 years‐old). Follow‐up assessment was performed seven days post‐injury and compared with pre‐injury baseline. Cognitive performance was assessed using the Immediate Post‐Concussion Assessment and Cognitive Testing (ImPACT®) battery. Hierarchical regression analyses were conducted to examine the relationship between on‐field signs of concussion and the post‐injury change in cognitive performance. The findings indicated that on‐field loss of consciousness, amnesia, and vacant look were associated with larger decrements in cognition. Loss of consciousness accounted for 22% of the variance in verbal memory scores; amnesia accounted for 15% of the variance in verbal memory scores, and the presence of vacant look accounted for 9% of the variance in visual memory performance. The presence of loss of consciousness, amnesia, or vacant look is risk factors for longer recovery times and predict the need for extended cognitive follow‐up.

Objective In sports concussion research, the importance of an individualized approach incorporating neuropsychological assessment data has been emphasized. This study examined the impact of acute signs of concussion on post-injury cognitive functioning using reliable change methodology in a sample of Finnish, elite-level, youth ice hockey players. Methods From a sample of 1,823 players (all male, 14–20 years old) who completed preseason baseline testing with the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT®) battery, two subgroups were identified. First, in total, 312 uninjured athletes, who completed baseline testing twice—1 year apart. The scores were contrasted to calculate reliable change indices (RCIs). Second, from a subsample of 570 athletes participating in an intensive follow-up arm of the project, the analysis included 32 concussed athletes. The RCIs were determined for the five ImPACT composite scores and used in identifying athletes with declined performance 3 days post-injury. Results Test-retest reliability ranged from .39 to .71. Athletes who had experienced an acute loss of consciousness, amnesia, or postural instability had increased odds for declines in two or more areas assessed by ImPACT (odds ratio = 7.67–8.00, p < .05). In contrast, acute disorientation or vacant look did not lead to cognitive change that met the reliable change threshold. Conclusions The reliability coefficients and RCIs differed from those published earlier emphasizing the importance of national reference values. The presence of acute loss of consciousness, amnesia, or postural instability may indicate a more severe injury and predict the need for more intensive cognitive follow-up.

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