Long-term Multidomain Patterns of Change After Traumatic Brain Injury: A TRACK-TBI LONG Study

Blood-Based Protein Biomarkers in the Chronic Phase of Traumatic Brain Injury: A Systematic Review

There has been limited exploration of blood-based biomarkers in the chronic period following traumatic brain injury (TBI). Our objective was to conduct a systematic review of studies examining blood-based protein biomarkers with at least one sample collected 12 months post-TBI in adults (≥16 years). Database searches were conducted in Embase, MEDLINE, and Science Citation Index-Expanded on July 24, 2023. Risk of bias was assessed using modified Joanna Briggs Institute critical appraisal tools. Only 30 of 12,523 articles met inclusion criteria, with samples drawn from 12 months to 48 years. Higher quality evidence (low risk of bias; large samples) identified promising inflammatory biomarkers at 12 months post-injury in both moderate-severe TBI (GFAP) and mild TBI (eotaxin-1, IFN-y, IL-8, IL-9, IL-17A, MCP-1, MIP-1β, FGF-basic, and TNF-α). Studies with low risk of bias but smaller samples also suggest NSE, MME, and CRP may be informative, alongside protein variants for α-syn (10H, D5), amyloid-β (A4, C6T), TDP-43 (AD-TDP 1;2;3;9;11), and tau (D11C). Findings for NfL were inconclusive. Longitudinal data were mostly available for acute samples followed until 12 months post-injury, with limited evaluation of changes beyond 12 months. Associations of some blood-based biomarkers with cognitive, sleep, and functional outcomes were reported. The overall strength of the evidence in this review was limited by the risk of bias and small sample sizes. Replication is required within prospective longitudinal studies that move beyond 12 months post-injury. Novel efforts should be guided by promising neurodegenerative-disease markers and use panels to model polypathology.

Cognitive Performance is Associated With 1-Year Participation and Life Satisfaction Outcomes: A Traumatic Brain Injury Model Systems Study

OBJECTIVE

To determine, in persons with traumatic brain injury (TBI), the association between cognitive change after inpatient rehabilitation discharge and 1-year participation and life satisfaction outcomes.

DESIGN

Secondary analysis of prospectively collected TBI Model Systems (TBIMS) data.

SETTING

Inpatient rehabilitation and community.

PARTICIPANTS

499 individuals with TBI requiring inpatient rehabilitation who completed the Brief Test of Adult Cognition by Telephone (BTACT) at inpatient rehabilitation discharge (ie, baseline) and 1-year postinjury.

MAIN OUTCOME MEASURES

Participation Assessment with Recombined Tools-Objective (PART-O) and Satisfaction with Life Scale (SWLS).

RESULTS

Of 2,840 TBIMS participants with baseline BTACT, 499 met inclusion criteria (mean [standard deviation] age = 45 [19] years; 72% male). Change in BTACT executive function (EF) was not associated with 1-year participation (PART-O; β = 0.087, 95% CI [-0.004, 0.178], P = .061) when it was the sole model predictor. Change in BTACT episodic memory (EM) was associated with 1-year participation (β = 0.096, [0.007, 0.184], P = .035), but not after adjusting for demographic, clinical, and functional status covariates (β = 0.067, 95% CI [-0.010, 0.145], P = .089). Change in BTACT EF was not associated with life satisfaction total scores (SWLS) when it was the sole model predictor (β = 0.091, 95% CI [-0.001, 0.182], P = .0503). Change in BTACT EM was associated with 1-year life satisfaction before (β = 0.114, 95% CI [0.025, 0.202], P = .012) and after adjusting for covariates (β = 0.103, [0.014, 0.191], P = .023). In secondary analyses, change in BTACT EF was associated with PART-O Social Relations and Out and About subdomains before (Social Relations: β = 0.127, 95% CI [0.036, 0.217], P = .006; Out and About: β = 0.141, 95% CI [0.051, 0.232], P = .002) and after (Social Relations: β = 0.168, 95% CI [0.072, 0.265], P < .002; Out and About: β = 0.156, 95% CI [0.061, 0.252], P < .002) adjusting for functional status and further adjusting for covariates (Social Relations: β = 0.127, 95% CI [0.040, 0.214], P = .004; Out and About: β = 0.136, 95% CI [0.043, 0.229], P = .004). However, only the models adjusting for functional status remained significant after multiple comparison correction (ie, Bonferroni-adjusted alpha level = 0.002).

CONCLUSION

EF gains during the first year after TBI were related to 1-year social and community participation. Gains in EM were associated with 1-year life satisfaction. These results highlight the potential benefit of cognitive rehabilitation after inpatient rehabilitation discharge and the need for interventions targeting specific cognitive functions that may contribute to participation and life satisfaction after TBI.

Ageing with Traumatic Brain Injury: Long-Term Cognition and Wellbeing

Whether and how traumatic brain injury (TBI) impacts ageing in the decades post-injury remains a matter of debate, partly due to a lack of controlled studies. This study examined the long-term impact of TBI on cognition and wellbeing in middle-aged and older adults and explored the relationship between age, cognition, and wellbeing, compared with a non-TBI control group. Cross-sectional data from 143 participants aged ≥40 with moderate-severe TBI (6-33 years post-injury; mean age 59.64) were compared with 71 non-TBI controls (mean age 62.10) group matched on age, gender, and premorbid IQ. Individuals with significant confounding comorbidities were excluded. A battery of neuropsychological tests and wellbeing measures (emotional distress, sleep, health-related quality of life [HRQoL]) was administered. Older age and TBI were each independently associated with poorer cognition across multiple domains (p < 0.05). The relationship between verbal learning and memory impairment post-TBI differed between age groups: individuals with TBI in their 40s-60s performed significantly worse than same-aged controls on verbal story acquisition (B = 0.09, p = 0.040, 95% confidence interval [CI] [0.004, 0.17]) and recall (B = 0.12, p = 0.009, 95% CI [0.03, 0.21]), and verbal wordlist recall (B = 0.11, p = 0.007, 95% CI [0.03, 0.19]). In comparison, no significant group differences in verbal memory emerged for ages 70-90. The TBI group reported greater emotional distress (B = 3.55, p < 0.001, 95% CI [1.73, 5.37]), poorer sleep quality (B = 1.07, p = 0.016, 95% CI [0.20, 1.94]), and poorer physical HRQoL (B = -4.26, p = 0.003, 95% CI [-7.08, -1.43]) than controls at all ages. Poorer physical HRQoL was related to poorer cognition post-TBI (p < 0.05). Our results challenge the notion that TBI exacerbates ageing. Moderate-severe TBI resulted in significant long-term impairments in cognition and wellbeing, with verbal learning and memory more impaired during middle-adulthood but not older adulthood compared to controls. TBI was not associated with changes to wellbeing with ageing. Intervention for verbal memory deficits in middle-aged adults with TBI is important, along with wider long-term supports for cognition, wellbeing, and activity participation in all individuals with TBI.

Disparities between native americans and white individuals in global outcome trajectories over the 5 years after traumatic brain injury: A model systems study

PURPOSE

Traumatic brain injury (TBI) can lead to a host of challenges and negatively impacts Native Americans more than any other ethnic group in the U.S. Despite this, little research exists on Native Americans with TBI. The current study examined disparities in global outcome trajectories (overall level of function post-injury) between Native Americans and White individuals in the 5 years following TBI and whether sociodemographic or injury-related characteristics could account for this disparity.

METHOD

The current study used a sample of 75 Native Americans demographically matched by sex, age, and injury severity to 75 White individuals from the U.S. Traumatic Brian Injury Model Systems (TBIMS) database (n =  150). A series of hierarchical linear models (HLMs) was used to examine longitudinal global outcome trajectories between the two groups.

RESULTS

Native Americans showed lower global outcome scores than their White counterparts with this difference worsening (i.e., growing larger) over time. The difference in scores and the differential movement over time were associated with differences between the ethnic groups in employment at the time of injury, substance use patterns, and type of insurance.

CONCLUSION

This study highlights the need for identification of and early intervention for risk factors that predict disparities in rehabilitation outcomes and points to the need for greater access to culturally informed care for Native Americans with TBI.

Natural history of recovery and long-term outcome in critically ill patients with brain injury

PURPOSE OF REVIEW

To increase knowledge of the natural history of recovery and long-term outcome following severe traumatic brain injury (sTBI).

RECENT FINDINGS

Recovery of consciousness and complex behaviors that presage subsequent functional recovery frequently occurs well beyond the first 7 days after injury, which is typically the time period widely used in the ICU for prognostic decision-making and establishing goals of care for. Similarly, recovery of functional independence occurs between 1 and 10 years postinjury in a substantial proportion of patients who do not recover command-following during the acute hospitalization. Data from large, multicenter studies that systematically conduct long-term follow-up with well validated measures consistently indicate that the most common trajectory of recovery after 1 year postinjury is characterized by changes, not stability, in functional status.

SUMMARY

Evidence from large multicenter studies with well characterized samples focusing on recovery trajectories beyond 1 year postinjury challenge conventional beliefs about outcome after sTBI. Signs of consciousness frequently emerge following discharge from the ICU setting and prediction of death and dependency within the first few weeks after injury is unreliable. Clinician knowledge of the frequency and time course to recovery of key behavioral milestones is central to evidence-based prognostic counseling.

Timing of neuroprognostication in the ICU

PURPOSE OF REVIEW

Neuroprognostication after acute brain injury (ABI) is complex. In this review, we examine the threats to accurate neuroprognostication, discuss strategies to mitigate the self-fulfilling prophecy, and how to approach the indeterminate prognosis.

RECENT FINDINGS

The goal of neuroprognostication is to provide a timely and accurate prediction of a patient's neurologic outcome so treatment can proceed in accordance with a patient's values and preferences. Neuroprognostication should be delayed until at least 72 h after injury and/or only when the necessary prognostic data is available to avoid early withdraw life-sustaining treatment on patients who may otherwise survive with a good outcome. Clinicians should be aware of the limitations of available predictors and prognostic models, the role of flawed heuristics and the self-fulfilling prophecy, and the influence of surrogate decision-maker bias on end-of-life decisions.

SUMMARY

The approach to neuroprognostication after ABI should be systematic, use highly reliable multimodal data, and involve experts to minimize the risk of erroneous prediction and perpetuating the self-fulfilling prophecy. Even when such standards are rigorously upheld, the prognosis may be indeterminate. In such cases, clinicians should engage in shared decision-making with surrogates and consider the use of a time-limited trial.

Cell-Specific Gene Expressions Underlie Selective White Matter Loss Vulnerability in Mild Traumatic Brain Injury

Traumatic brain injury (TBI), a risk factor for later-life dementia, leads to salient brain atrophy, particularly in the white matter. It is not clear how white matter atrophy progresses or why some brain regions are damaged while others are spared. We hypothesized that spatial variations of cell-specific gene expression contributed to the selective white matter loss vulnerability following mild TBI (mTBI). Gene expression data were sourced from the publicly available Allen Human Brain Atlas, which comprises microarray data spanning nearly the entire brain, derived from six neurologically normal adult donors. A total of 100 patients with acute stage (within 7 days post-injury) mTBI were enrolled. Of these, 60 patients were followed up at 3 months post-injury and 37 were followed up at 6-12 months post-injury. In addition, 59 healthy controls (HCs), matched for age, gender, and education, were included for comparative analysis. White matter volume changes were analyzed at both the acute stage, 3 months, and 6-12 months follow-up in mTBI patients compared with HCs. Patients with mTBI exhibited significant white matter atrophy in the frontal, parietal, and temporal cortices at 3 months post-injury, which even persisted at 6-12 months follow-up. In addition, mTBI patients with cognitive deficits showed more severe brain atrophy compared with those without cognitive deficits. Crucially, the gene expression marking endothelial cells and S1 pyramidal neurons were associated with increased brain atrophy, whereas the gene expression marking microglia and CA1 pyramidal neurons were associated with decreased brain atrophy in mTBI patients at 3 months post-injury. Microglia and endothelial cells can explain 23.6% of regional variations in the white matter atrophy. These findings suggested that modulating cellular activation, especially by promoting microglial activation at 3 months post-injury, might be a promising approach to prevent white matter atrophy, enhance cognitive outcomes, and reduce the risk of later-life dementia.

Recognition of Traumatic Brain Injury as a Chronic Condition: A Commentary

Many clinicians believe that residual impairments due to traumatic brain injury (TBI) are static once initial recovery has plateaued. That is, the effects of the injury are not expected to change significantly over the remainder of a person's life. This assumption has been called into question by several independent longitudinal studies showing that the long-term course of TBI may be better characterized as dynamic rather than static. Health care services that recognize brain injury as a chronic condition would encourage education on self-management to improve or protect health, as well as proactive health care that anticipates common co-morbidities. Those who have had a TBI would be encouraged to engage in lifestyles that optimize wellness. Almost all developed countries commit additional public health resources to addressing chronic conditions. In the United States, specific benefits are available from health insurance plans, particularly Medicare and Medicaid, for persons experiencing chronic health conditions. Potentially the most important benefit would derive from health care practitioners becoming aware of the dynamic nature of chronic brain injury and thus being more attentive to how their patients could be better served to optimize improvement and minimize decline. Recognition of TBI as a chronic condition would not only focus more resources on problems associated with living with brain injury but would also enhance both the public's and professionals' awareness of how to optimize the health and well-being of persons living with the effects of TBI.

Fluid biomarkers of chronic traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of long-term disability across the world. Evidence for the usefulness of imaging and fluid biomarkers to predict outcomes and screen for the need to monitor complications in the acute stage is steadily increasing. Still, many people experience symptoms such as fatigue and cognitive and motor dysfunction in the chronic phase of TBI, where objective assessments for brain injury are lacking. Consensus criteria for traumatic encephalopathy syndrome, a clinical syndrome possibly associated with the neurodegenerative disease chronic traumatic encephalopathy, which is commonly associated with sports concussion, have been defined only recently. However, these criteria do not fit all individuals living with chronic consequences of TBI. The pathophysiology of chronic TBI shares many similarities with other neurodegenerative and neuroinflammatory conditions, such as Alzheimer disease. As with Alzheimer disease, advancements in fluid biomarkers represent one of the most promising paths for unravelling the chain of pathophysiological events to enable discrimination between these conditions and, with time, provide prediction modelling and therapeutic end points. This Review summarizes fluid biomarker findings in the chronic phase of TBI (≥6 months after injury) that demonstrate the involvement of inflammation, glial biology and neurodegeneration in the long-term complications of TBI. We explore how the biomarkers associate with outcome and imaging findings and aim to establish mechanistic differences in biomarker patterns between types of chronic TBI and other neurodegenerative conditions. Finally, current limitations and areas of priority for future fluid biomarker research are highlighted.

Traumatic brain injury and cognitive change over 30 years among community-dwelling older adults

INTRODUCTION

There is limited evidence regarding the rate of long-term cognitive decline after traumatic brain injury (TBI) among older adults.

METHODS

In this prospective cohort study, time-varying TBI was defined by self-report and International Classification of Disease diagnostic codes. Cognitive testing was performed at five visits over 30 years and scores were combined into a global cognition factor score. Adjusted linear mixed-effects models estimated the association of TBI with cognitive change.

RESULTS

A total of 11,701 Atherosclerosis Risk in Communities (ARIC) Study participants (mean baseline age 58 years, 58% female, 25% Black) without TBI at baseline were included. Over follow-up, 18% experienced TBI. The adjusted average decline in cognition per decade (standard deviation units) was more than twice as fast among individuals with ≥ 2 incident TBIs (𝛽 = -0.158, 95% confidence interval [CI] = -0.253,-0.063), but not among individuals with 1 TBI (𝛽 = -0.052, 95% CI = -0.107, 0.002), compared to without TBI (𝛽 = -0.057, 95% CI = -0.095, -0.020).

DISCUSSION

This study provides robust evidence that TBIs fundamentally alter the trajectories of cognitive decline.

HIGHLIGHTS

The adjusted average decline in cognition per decade (standard deviation units) was more than twice as fast among individuals with ≥ 2 incident traumatic brain injuries (TBIs; 𝛽 = -0.158, 95% confidence interval [CI] = -0.253, -0.063), but not with 1 TBI (𝛽 = -0.052, 95% CI = -0.107, 0.002), compared to without TBI (𝛽 = -0.057, 95% CI = -0.095, -0.020). Over a period of 30 years, this difference in cognitive decline is equivalent to individuals with ≥ 2 TBIs being 9.7 years older at baseline. Associations of TBI were stronger among individuals with one or two apolipoprotein E (APOE) ε4 alleles than among individuals with zero APOE ε4 alleles (P interaction = 0.007).

Axonal injury, sleep disturbances, and memory following traumatic brain injury

OBJECTIVES

Traumatic brain injury (TBI) is associated with sleep deficits, but it is not clear why some report sleep disturbances and others do not. The objective of this study was to assess the associations between axonal injury, sleep, and memory in chronic and acute TBI.

METHODS

Data were acquired from two independent datasets which included 156 older adult veterans (69.8 years) from the Alzheimer's Disease Neuroimaging Initiative (ADNI) with prior moderate-to-severe TBIs and 90 (69.2 years) controls and 374 (39.6 years) from Transforming Research and Clinical Knowledge in TBI (TRACK-TBI) with a recent mild TBI (mTBI) and 87 controls (39.6 years), all who completed an MRI, memory assessment, and sleep questionnaire.

RESULTS

Older adults with a prior TBI had a significant association between axonal injury and sleep disturbances [β = 9.52, 95% CI (4.1, 14.9), p = 0.01]. Axonal injury predicted changes in memory over 1-year in TBI [β = -8.72, 95% CI (-18, -2.7), p = 0.03]. We externally validated those findings in TRACK-TBI where axonal injury within 2 weeks after mTBI was significantly associated with higher sleep disturbances in the TBI group at 2 weeks[β = -7.2, 95% CI (-14, -0.50), p = 0.04], 6 months [β = -16, 95% CI (-24, -7.6), p ≤ 0.01], and 12 months post-injury [β = -11, 95% CI (-19, -0.85), p = 0.03]. These associations were not significant in controls.

INTERPRETATIONS

Axonal injury, specifically to the left anterior internal capsule is robustly associated with sleep disturbances in multiple TBI populations. Early assessment of axonal injury following mTBI could identify those at risk for persistent sleep disturbances following injury.

Predicting recovery in patients with mild traumatic brain injury and a normal CT using serum biomarkers and diffusion tensor imaging (CENTER-TBI): an observational cohort study

Background

Even patients with normal computed tomography (CT) head imaging may experience persistent symptoms for months to years after mild traumatic brain injury (mTBI). There is currently no good way to predict recovery and triage patients who may benefit from early follow-up and targeted intervention. We aimed to assess if existing prognostic models can be improved by serum biomarkers or diffusion tensor imaging metrics (DTI) from MRI, and if serum biomarkers can identify patients for DTI.

Methods

We included 1025 patients aged >18 years with a Glasgow Coma Score >12 and normal CT from the Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) study which recruited between December 19,2014 and December 17, 2017 (NCT02210221). Biomarkers (GFAP, NFL, S100B) were obtained at a median of 8.8 h (Q1-Q3 4.2-16.7) and DTI at 13 days (3-19) after injury. DTI metrics were available in 153 patients for 48 white matter tracts (ICBM-DTI-81 atlas). Incomplete recovery at three months was defined as an extended Glasgow Outcome Scale score <8. Existing prognostic models were fitted with and without biomarkers, or with and without DTI, and internally validated using bootstrapping.

Findings

385 (38%) patients had incomplete recovery. Adding biomarkers did not improve performance beyond the best existing clinical prognostic model [optimism-corrected AUC 0.69 (95% CI 0.65-0.72) and R2 17% (11-22)]. Adding DTI metrics significantly enhanced all models [best optimism-corrected AUC 0.82 (0.79-0.85) and R2 75% (39-100)]. The top three prognostic tracts were the left posterior thalamic radiation, left superior cerebellar peduncle and right uncinate fasciculus. Serum biomarkers could have avoided 1 in 5 DTI scans, with GFAP <12 h and NFL 12-24 h from injury performing best.

Interpretation

DTI substantially improved existing prognostic models for functional outcome in patients with mTBI and a normal CT, and biomarkers could help select patients for MRI. If validated, DTI could allow for targeted follow-up and enrichment of clinical trials of early interventions to improve outcome.

Funding

EU Seventh Framework Programme, Hannelore Kohl Stiftung, One Mind, Integra LifeSciences, NeuroTrauma Sciences.

Exploring the challenges of avoiding collisions with virtual pedestrians using a dual-task paradigm in individuals with chronic moderate to severe traumatic brain injury

BACKGROUND

Individuals with a moderate-to-severe traumatic brain injury (m/sTBI), despite experiencing good locomotor recovery six months post-injury, face challenges in adapting their locomotion to the environment. They also present with altered cognitive functions, which may impact dual-task walking abilities. Whether they present collision avoidance strategies with moving pedestrians that are altered under dual-task conditions, however, remains unclear. This study aimed to compare between individuals with m/sTBI and age-matched control individuals: (1), the locomotor and cognitive costs associated with the concurrent performance of circumventing approaching virtual pedestrians (VRPs) while attending to an auditory-based cognitive task and; (2) gaze behaviour associated with the VRP circumvention task in single and dual-task conditions.

METHODOLOGY

Twelve individuals with m/sTBI (age = 43.3 ± 9.5 yrs; >6 mo. post injury) and 12 healthy controls (CTLs) (age = 41.8 ± 8.3 yrs) were assessed while walking in a virtual subway station viewed in a head-mounted display. They performed a collision avoidance task with VRPs, as well as auditory-based cognitive tasks (pitch discrimination and auditory Stroop), both under single and dual-task conditions. Dual-task cost (DTC) for onset distance of trajectory deviation, minimum distance from the VRP, maximum lateral deviation, walking speed, gaze fixations and cognitive task accuracy were contrasted between groups using generalized estimating equations.

RESULTS

In contrast to CTLs who showed locomotor DTCs only, individuals with m/sTBI displayed both locomotor and cognitive DTCs. While both groups walked slower under dual-task conditions, only individuals with m/sTBI failed to modify their onset distance of trajectory deviation and maintained smaller minimum distances and smaller maximum lateral deviation compared to single-task walking. Both groups showed shorter gaze fixations on the approaching VRP under dual-task conditions, but this reduction was less pronounced in the individuals with m/sTBI. A reduction in cognitive task accuracy under dual-task conditions was found in the m/sTBI group only.

CONCLUSION

Individuals with m/sTBI present altered locomotor and gaze behaviours, as well as altered cognitive performances, when executing a collision avoidance task involving moving pedestrians in dual-task conditions. Potential mechanisms explaining those alterations are discussed. Present findings highlight the compromised complex walking abilities in individuals with m/sTBI who otherwise present a good locomotor recovery.

Long-term pituitary function and functional and patient-reported outcomes in severe acquired brain injury

OBJECTIVE

Assessment of posttraumatic hypothalamic-pituitary dysfunctions is expected to be the most relevant assessment to offer patients with severe intracranial affection. In this study, we aim to investigate the prevalence of hypopituitarism in patients with severe acquired traumatic brain injury (TBI) compared with nontraumatic brain injury (NTBI) and to relate pituitary insufficiency to functional and patient-reported outcomes.

DESIGN

This is a prospective study.

METHODS

We included patients admitted for inpatient neurorehabilitation after severe TBI (N = 42) and NTBI (N = 18). The patients underwent a pituitary function assessment at a mean of 2.4 years after the injury. Functional outcome was assessed by using Functional Independence Measure and Glasgow Outcome Scale-Extended (both 1 year after discharge from neurorehabilitation) and patient-reported outcome was assessed by using Multiple Fatigue Inventory-20 and EQ-5D-3L.

RESULTS

Hypopituitarism was reported in 10/42 (24%) patients with TBI and 7/18 (39%) patients with NTBI (P = .23). Insufficiencies affected 1 axis in 14/17 (82%) patients (13 hypogonadotropic hypogonadism and 1 growth hormone [GH] deficiency) and 2 axes in 3/17 (18%) patients (1 hypogonadotropic hypogonadism and GH deficiency, and 2 hypogonadotropic hypogonadism and arginin vasopressin deficiency). None had central hypoadrenalism or central hypothyroidism. In patients with both TBI and NTBI, pituitary status was unrelated to functioning and ability scores at 1 year and to patient-reported outcome scores at a mean of 2.4 years after the injury.

CONCLUSION

Patients with severe acquired brain injury may develop long-term hypothalamus-pituitary insufficiency, with an equal occurrence in patients with TBI and NTBI. In both types of patients, mainly isolated deficiencies, most commonly affecting the gonadal axis, were seen. Insufficiencies were unrelated to functional outcomes and patient-reported outcomes, probably reflecting the complexity and heterogeneous manifestations in both patient groups.

Slowing of Parameterized Resting-State Electroencephalography After Mild Traumatic Brain Injury

Reported changes in electroencephalography (EEG)-derived spectral power after mild traumatic brain injury (mTBI) remains inconsistent across existing literature. However, this may be a result of previous analyses depending solely on observing spectral power within traditional canonical frequency bands rather than accounting for the aperiodic activity within the collected neural signal. Therefore, the aim of this study was to test for differences in rhythmic and arrhythmic time series across the brain, and in the cognitively relevant frontoparietal (FP) network, and observe whether those differences were associated with cognitive recovery post-mTBI. Resting-state electroencephalography (rs-EEG) was collected from 88 participants (56 mTBI and 32 age- and sex-matched healthy controls) within 14 days of injury for the mTBI participants. A battery of executive function (EF) tests was collected at the first session with follow-up metrics collected approximately 2 and 4 months after the initial visit. After spectral parameterization, a significant between-group difference in aperiodic-adjusted alpha center peak frequency within the FP network was observed, where a slowing of alpha peak frequency was found in the mTBI group in comparison to the healthy controls. This slowing of week 2 (collected within 2 weeks of injury) aperiodic-adjusted alpha center peak frequency within the FP network was associated with increased EF over time (evaluated using executive composite scores) post-mTBI. These findings suggest alpha center peak frequency within the FP network as a candidate prognostic marker of EF recovery and may inform clinical rehabilitative methods post-mTBI.

Predictive Utility of Diffusion MRI After Mild Traumatic Brain Injury in Civilian Populations: A Systematic Review

OBJECTIVE

A considerable number of people experience persisting symptoms and functional limitations after mild traumatic brain injury (mTBI). It is unclear whether subtle white matter changes contribute to this phenomenon. In this systematic review, the authors evaluated whether microstructural white matter indices on advanced MRI are related to clinical dysfunction among patients without abnormalities on standard brain computed tomography (CT) or MRI (uncomplicated mTBI).

METHODS

A search of multiple databases was performed. Studies with individuals who experienced blast-related, sports-related, or multiple mTBIs were excluded. Diffusion tensor imaging (DTI) and susceptibility-weighted imaging (SWI) metrics and cognitive, neuropsychiatric, or functional outcome measures were extracted from each study.

RESULTS

Thirteen studies were selected (participants with mTBI, N=553; healthy control group, N=438). Seven DTI studies evaluated cognitive function, with five reporting significant correlations between reduced white matter integrity and deficits in attention, processing speed, and executive function at 6-12 months after injury (three studies included only individuals with uncomplicated mTBI). Four studies found significant correlations between DTI metrics and persistent postconcussive symptoms after 3-12 months (one study included only individuals with uncomplicated mTBI). Two SWI studies reported conflicting findings regarding the relationship between the presence of microbleeds and postconcussive symptoms.

CONCLUSIONS

The results revealed that indices of microstructural white matter integrity may relate to clinical presentation 3-12 months after injury in uncomplicated mTBI. However, analysis methods and brain regions studied varied across studies. Further research is needed to identify relationships between white matter indices in specific brain regions and symptom persistence beyond 12 months.

Late Blood Levels of Neurofilament Light Correlate With Outcome in Patients With Traumatic Brain Injury

Neurofilament light (NF-L) is an axonal protein that has shown promise as a traumatic brain injury (TBI) biomarker. Serum NF-L shows a rather slow rise after injury, peaking after 1-2 weeks, although some studies suggest that it may remain elevated for months after TBI. The aim of this study was to examine if plasma NF-L levels several months after the injury correlate with functional outcome in patients who have sustained TBIs of variable initial severity. In this prospective study of 178 patients with TBI and 40 orthopedic injury controls, we measured plasma NF-L levels in blood samples taken at the follow-up appointment on average 9 months after injury. Patients with TBI were divided into two groups (mild [mTBI] vs. moderate-to-severe [mo/sTBI]) according to the severity of injury assessed with the Glasgow Coma Scale upon admission. Recovery and functional outcome were assessed using the Extended Glasgow Outcome Scale (GOSE). Higher levels of NF-L at the follow-up correlated with worse outcome in patients with moderate-to-severe TBI (Spearman's rho = -0.18; p < 0.001). In addition, in computed tomography-positive mTBI group, the levels of NF-L were significantly lower in patients with GOSE 7-8 (median 18.14; interquartile range [IQR] 9.82, 32.15) when compared with patients with GOSE <7 (median 73.87; IQR 32.17, 110.54; p = 0.002). In patients with mTBI, late NF-L levels do not seem to provide clinical benefit for late-stage assessment, but in patients with initially mo/sTBI, persistently elevated NF-L levels are associated with worse outcome after TBI and may reflect ongoing brain injury.