Chronic motor performance following different traumatic brain injury severity-A systematic review

Neuroinflammatory Response in the Traumatic Brain Injury: An Update

The central nervous system (CNS) comprises membranes and barriers that are vital to brain homeostasis. Membranes form a robust shield around neural structures, ensuring protection and structural integrity. At the same time, barriers selectively regulate the exchange of substances between blood and brain tissue, which is essential for maintaining homeostasis. Another highlight is the glymphatic system, which cleans metabolites and waste from the brain. Traumatic brain injury (TBI) represents a significant cause of disability and mortality worldwide, resulting from the application of direct mechanical force to the head that results in a primary injury. Therefore, this review aims to elucidate the mechanisms associated with the secondary injury cascade, in which there is intense activation of glial cells, dysfunction of the glymphatic system, glutamatergic neurotoxicity, additional molecular and biochemical changes that lead to a neuroinflammatory process, and oxidative stress and in which way they can be associated with cognitive damage that is capable of lasting for an extended period.

Aerobic performance in rats subjected to incremental-speed running exercise: A multiple regression analysis study emphasizing thermoregulation-related variables

Single-variable analyses have limited ability to explain complex phenomena such as the regulation of prolonged physical (aerobic) performance. Our study aimed to identify predictors of performance in rats subjected to incremental-speed running exercise. Notably, most variables assessed were associated with rats' thermoregulation. We extracted data from 355 records obtained in 216 adult Wistar rats. Hierarchical multiple linear regression analyses were conducted to identify the predictive power of eight variables. The distance traveled, a performance index, was the dependent variable. The independent variables included body mass, biological sex, body core temperature (TCORE) measurement site, and the following thermoregulation-related variables: ambient temperature (TAMB), initial TCORE, exercise-induced change in TCORE (ΔTCORE), ΔTCORE from 0 to 10 min (ΔTCORE 0-10; when TCORE increase is fastest), and heat loss index (HLI). This analysis with eight variables revealed an adjusted R2 of 0.495; TAMB, ΔTCORE, body mass, and ΔTCORE 0-10 had the highest predictive powers (β values: -0.700, 0.463, -0.353, and -0.130, respectively). Additional analyses consisted of separate regressions for each TCORE index measured: abdominal (TABD), brain (TBRAIN), and colonic (TCOL) temperature. These analyses yielded adjusted R2 values of 0.608 (TABD), 0.550 (TBRAIN), and 0.437 (TCOL). Again, the distance traveled was primarily predicted by body mass and thermoregulation-related variables (TAMB, ΔTCORE, and ΔTCORE 0-10). Among these four variables, ΔTCORE was the only one with a positive β value (directly predicted performance), while the others had negative values. Collectively, these findings advance our understanding of performance regulation in rats, especially regarding the role of thermoregulation-related variables.

Lower extremity muscle activity during reactive balance differs between adults with chronic traumatic brain injury and controls

Background

Control of reactive balance is key to achieving safe independent walking and engagement in life activities. After traumatic brain injury (TBI), motor impairments and mobility challenges are persistent sequelae. To date, no studies have explored muscle activity of individuals with chronic TBI during a task that requires reactive control of balance.

Objective

To investigate lower extremity muscle activity during a reactive balance test performed by adults with chronic severe TBI and matched controls. We hypothesized that abnormal activity of lower extremity muscles would be related with poorer reactive balance performance. Also, we performed an exploratory analysis for those with TBI investigating the impact of unilateral versus bilateral lower extremity involvement in the control of reactive balance.

Methods

Ten adults with chronic severe TBI who were independent community ambulators and ten matched controls performed the computerized reactive balance test (Propriotest®) while lower extremity muscle activity was recorded. Electromyographic (EMG) activity was contrasted (Mann-Whitney U Test) between groups across each 10 s epoch of the 120 s test. Additionally, test scores were correlated (Spearman) with lower extremity composite EMG activity to distinguish muscle activity patterns related with reactive balance performance. Lastly, reactive balance test scores were correlated with reactive balance test scores and clinical functional measures only for the TBI group.

Results

Although the TBI group exhibited greater EMG activity across the entire test compared with the control group, significant differences were not observed. Greater composite EMG activity correlated significantly with poorer reactive balance performance across most of the 10 s windows of the test.

Conclusion

Greater muscle activity exhibited during the reactive balance test by individuals with chronic severe TBI compared to those without disabilities, particularly at small unexpected perturbations, highlights the greater physiologic effort required to control reactive balance even after independent ambulation is achieved.

Longitudinal Assessment of Selective Motor Dysfunction in Service Members With Combat-Related Mild TBI

INTRODUCTION

Evaluations of clinical outcomes in service members with mild traumatic brain injury (TBI) sustained in combat have largely focused on neurobehavioral and somatic symptoms, neurocognitive functioning, and psychological/psychiatric health. Questions remain regarding other domains, such as gross or fine motor abilities, that could be impacted and are mission-critical to functional warfighters.

MATERIALS AND METHODS

The objective of the current study was to evaluate longitudinal motor function in U.S. Military personnel with and without mild TBI sustained in combat to assess the possible long-term impact. Data from the EValuation Of Longitudinal outcomes in mild TBI active duty military and VEterans (EVOLVE) study were leveraged for analysis. The EVOLVE study has evaluated and followed service members from combat and following medical evacuation with and without blast-related mild TBI, as well as blunt impact mild TBI, and noninjured combat-deployed service members, tracking 1-, 5-, and 10-year outcomes. Longitudinal demographic, neuropsychological, and motor data were leveraged. Cross-sectional differences in outcomes at each year among the 4 injury groups were assessed using rank regression, adjusting for age, education, sex, branch of service (Army vs. other), subsequent head injury exposure, and separation from service. To understand the possible performance impact of time on all the measures, mixed-effects rank regression was employed, assessing time with adjustments for group, age, education, subsequent head injury exposure, and service separation status, followed by Benjamini-Hochberg correction for multiple comparisons.

RESULTS

Evaluation for cognitive performance across 19 primary measures of interest at 1, 5, and 10 years did not identify any significant differences; however, gross motor function was found to be significantly different across groups at all time points (adjusted P < .001 at 1 year, P = .004 at 5 years, and P < .001 at 10 years) with both TBI groups consistently performing slower on the 25-Foot Walk and Grooved Pegboard than the nonblast control groups. While there were no cross-sectional differences across groups, many cognitive and motor measures were found to have significant changes over time, though not always in the direction of worse performance. Selective motor impairment in both TBI groups was identified compared to nonblast controls, but all groups were also found to exhibit a level of motor slowing when comparing performance at 1- to 10-year follow-ups.

CONCLUSIONS

Assessment of gross motor function reflected a consistent pattern of significantly slower performances for blast and nonblast TBI groups compared to controls, over all follow-up intervals. Fine motor function performance reflected a similar significant difference pattern at 1- and 5-year follow-up intervals, with a reduced difference from control groups at the 10-year follow-up. Maintenance of high-level motor functions, including overall motor speed, coordination, and reaction time, is a primary component for active warfighters, and any motor-related deficits could create an increased risk for the service member or unit. While the service members in this longitudinal study did not meet criteria for any specific clinical motor-related diagnoses or movement disorders, the finding of motor slowing may reflect a subclinical but significant change that could be a focus for intervention to return to preinjury levels.

Long Noncoding RNA VLDLR-AS1 Levels in Serum Correlate with Combat-Related Chronic Mild Traumatic Brain Injury and Depression Symptoms in US Veterans

More than 75% of traumatic brain injuries (TBIs) are mild (mTBI) and military service members often experience repeated combat-related mTBI. The chronic comorbidities concomitant with repetitive mTBI (rmTBI) include depression, post-traumatic stress disorder or neurological dysfunction. This study sought to determine a long noncoding RNA (lncRNA) expression signature in serum samples that correlated with rmTBI years after the incidences. Serum samples were obtained from Long-Term Impact of Military-Relevant Brain-Injury Consortium Chronic Effects of Neurotrauma Consortium (LIMBIC CENC) repository, from participants unexposed to TBI or who had rmTBI. Four lncRNAs were identified as consistently present in all samples, as detected via droplet digital PCR and packaged in exosomes enriched for CNS origin. The results, using qPCR, demonstrated that the lncRNA VLDLR-AS1 levels were significantly lower among individuals with rmTBI compared to those with no lifetime TBI. ROC analysis determined an AUC of 0.74 (95% CI: 0.6124 to 0.8741; p = 0.0012). The optimal cutoff for VLDLR-AS1 was ≤153.8 ng. A secondary analysis of clinical data from LIMBIC CENC was conducted to evaluate the psychological symptom burden, and the results show that lncRNAs VLDLR-AS1 and MALAT1 are correlated with symptoms of depression. In conclusion, lncRNA VLDLR-AS1 may serve as a blood biomarker for identifying chronic rmTBI and depression in patients.

A pre-existing Toxoplasma gondii infection exacerbates the pathophysiological response and extent of brain damage after traumatic brain injury in mice

Traumatic brain injury (TBI) is a key contributor to global morbidity that lacks effective treatments. Microbial infections are common in TBI patients, and their presence could modify the physiological response to TBI. It is estimated that one-third of the human population is incurably infected with the feline-borne parasite, Toxoplasma gondii, which can invade the central nervous system and result in chronic low-grade neuroinflammation, oxidative stress, and excitotoxicity-all of which are also important pathophysiological processes in TBI. Considering the large number of TBI patients that have a pre-existing T. gondii infection prior to injury, and the potential mechanistic synergies between the conditions, this study investigated how a pre-existing T. gondii infection modified TBI outcomes across acute, sub-acute and chronic recovery in male and female mice. Gene expression analysis of brain tissue found that neuroinflammation and immune cell markers were amplified in the combined T. gondii + TBI setting in both males and females as early as 2-h post-injury. Glutamatergic, neurotoxic, and oxidative stress markers were altered in a sex-specific manner in T. gondii + TBI mice. Structural MRI found that male, but not female, T. gondii + TBI mice had a significantly larger lesion size compared to their uninfected counterparts at 18-weeks post-injury. Similarly, diffusion MRI revealed that T. gondii + TBI mice had exacerbated white matter tract abnormalities, particularly in male mice. These novel findings indicate that a pre-existing T. gondii infection affects the pathophysiological aftermath of TBI in a sex-dependent manner, and may be an important modifier to consider in the care and prognostication of TBI patients.