Mild traumatic brain injury: the elusive timing of "recovery"

Classification Criteria and Rates of Persistent Postconcussive Symptoms in Children: A Systematic Review and Meta-Analysis

OBJECTIVE

To provide a systematic review of studies examining the proportion of children with persistent postconcussive symptoms (PPCS) and to examine potential moderators of prevalence.

STUDY DESIGN

Searches were conducted in MEDLINE, Embase, PsycINFO, Scopus, and Cochrane Central Register of Controlled Trials on April 16, 2020. Criteria for study inclusion were children aged <18 years with concussion or mild traumatic brain injury, operational definition of PPCS, assessment of postconcussive symptoms at least 4 weeks postinjury, sample sizes and proportion with PPCS available, and study published in English. Definition of PPCS, sample size, proportion of participants identified with PPCS, child sex and age at injury, time postinjury, premorbid symptoms, diagnosis (concussion or mild traumatic brain injury), and study publication year were extracted from each article. Study quality was assessed using the Newcastle-Ottawa Scale.

RESULTS

Thirteen studies, with a total of 5307 participants, were included in our analysis. The proportion of children identified with PPCS was 35.1% (weighted average; 95% CI, 26.3%-45.0%). The prevalence of PPCS was higher in older and female children who presented for care at concussion clinics, and in more recent publications.

CONCLUSIONS

Approximately one-third of children with concussion/mild traumatic brain injury will experience PPCS. Age, sex, and point of care could help identify children at high risk for PPCS.

Persistent symptoms and activity changes three months after mild traumatic brain injury

BACKGROUND/AIM

Approximately, 80% of traumatic brain injuries are considered mild in severity. Mild traumatic brain injury (mTBI) may cause temporary or persisting impairments that can adversely affect an individual's ability to participate in daily occupations and life roles. This study aimed to identify symptoms, factors predicting level of symptoms and functional and psycho-social outcomes for participants with mTBI three months following injury.

METHOD

Patients discharged from the Emergency Department of a major metropolitan hospital with a diagnosis of mTBI were contacted by telephone three months after injury. An interview with two questionnaires was administered: The Concussion Symptom Inventory (CSI) Scale and the Rivermead Head Injury Follow-Up Questionnaire (RHIFUQ). Data obtained were used to determine the type and prevalence of post-concussion symptoms and their impact on activity change.

RESULTS

Sixty-three people with mTBI participated in the study. The majority of participants (81%) reported that all symptoms had resolved within the three-month time frame. Of those still experiencing symptoms, workplace fatigue (22%) and an inability to maintain previous workload/standards (17%) were reported.

CONCLUSION

There is a small, but clinically significant, subgroup of patients who continue to experience symptoms three-month post-mTBI. Symptoms experienced beyond the expected three-month recovery timeframe have the potential to adversely affect an individual's ability to participate in daily occupation and return to work.

Heart Rate Variability of Athletes Across Concussion Recovery Milestones: A Preliminary Study

OBJECTIVE

To assess heart rate variability (HRV) in athletes with concussion across three phases of recovery.

DESIGN

A prospective matched control group design included the collection of HRV and symptoms measured by the Rivermead Post-Concussion Questionnaire. These measures were taken at 3 phases of recovery [(1) symptomatic; (2). asymptomatic; and (3) one-week after return-to-play (RTP)]. The same protocol was completed by noninjured athletes.

SETTING

Interuniversity sports teams at a single institution.

PARTICIPANTS

11 athletes, across 7 sports, diagnosed with concussion, and 11 matched-athlete controls volunteered for the study.

INTERVENTION

Physician diagnosed concussion and a sitting to standing protocol for HRV monitoring.

MAIN OUTCOME MEASURES

The frequency, time, and nonlinear domains of HRV were assessed along with the absolute difference between sitting and standing for each.

RESULTS

A 2 x 3 (group x phase) repeated-measures analysis of variance revealed significant interactions for sitting High Frequency (HF) norm, sitting Low Frequency (LF) norm, the difference between sitting and standing HF norm, and difference between sitting and standing LF norm. Acutely, athletes with concussion displayed increased LF norm and decreased HF norm while sitting and a decreased change in their HF and LF norm measures between sitting and standing. A significant group effect for sample entropy when standing was detected, with the concussed group displaying decreased values compared with the matched controls.

CONCLUSIONS

Athletes with concussion displayed autonomic dysfunction in some measures of HRV that persisted beyond RTP and were related to a previous history of concussion.

Blast Exposure, White Matter Integrity, and Cognitive Function in Iraq and Afghanistan Combat Veterans

The long-term effects of blast exposure are a major health concern for combat veterans returning from the recent conflicts in Iraq and Afghanistan. We used an optimized diffusion tensor imaging tractography algorithm to assess white matter (WM) fractional anisotropy (FA) in blast-exposed Iraq and Afghanistan veterans (n = 40) scanned on average 3.7 years after deployment/trauma exposure. Veterans diagnosed with a blast-related mild traumatic brain injury (mTBI) were compared to combat veterans with blast exposure but no TBI diagnosis. Blast exposure was associated with decreased FA in several WM tracts. However, total blast exposure did not correlate well with neuropsychological testing performance and there were no differences in FA based on mTBI diagnosis. Yet, veterans with mTBI performed worse on every neurocognitive test administered. Multiple linear regression across all blast-exposed veterans using a six-factor prediction model indicated that the amount of blast exposure accounted for 11–15% of the variability in composite FA scores such that as blast exposure increased, FA decreased. Education accounted for 10% of the variability in composite FA scores and 25–32% of FA variability in the right cingulum, such that as level of education increased, FA increased. Total blast exposure, age, and education were significant predictors of FA in the left cingulum. We did not find any effect of post-traumatic stress disorder on cognition or composite FA. In summary, our findings suggest that greater total blast exposure is a contributing factor to poor WM integrity. While FA was not associated with neurocognitive performance, we hypothesize that FA changes in the cingulum in veterans with multiple combat exposures and no head trauma prior to deployment may represent a marker of vulnerability for future deficits. Future work needs to examine this longitudinally.

Sports-related concussions: diagnosis, complications, and current management strategies

Sports-related concussions (SRCs) are traumatic events that affect up to 3.8 million athletes per year. The initial diagnosis and management is often instituted on the field of play by coaches, athletic trainers, and team physicians. SRCs are usually transient episodes of neurological dysfunction following a traumatic impact, with most symptoms resolving in 7-10 days; however, a small percentage of patients will suffer protracted symptoms for years after the event and may develop chronic neurodegenerative disease. Rarely, SRCs are associated with complications, such as skull fractures, epidural or subdural hematomas, and edema requiring neurosurgical evaluation. Current standards of care are based on a paradigm of rest and gradual return to play, with decisions driven by subjective and objective information gleaned from a detailed history and physical examination. Advanced imaging techniques such as functional MRI, and detailed understanding of the complex pathophysiological process underlying SRCs and how they affect the athletes acutely and long-term, may change the way physicians treat athletes who suffer a concussion. It is hoped that these advances will allow a more accurate assessment of when an athlete is truly safe to return to play, decreasing the risk of secondary impact injuries, and provide avenues for therapeutic strategies targeting the complex biochemical cascade that results from a traumatic injury to the brain.

Neuroimaging biomarkers in mild traumatic brain injury (mTBI)

Reviewed herein are contemporary neuroimaging methods that detect abnormalities associated with mild traumatic brain injury (mTBI). Despite advances in demonstrating underlying neuropathology in a subset of individuals who sustain mTBI, considerable disagreement persists in neuropsychology about mTBI outcome and metrics for evaluation. This review outlines a thesis for the select use of sensitive neuroimaging methods as potential biomarkers of brain injury recognizing that the majority of individuals who sustain an mTBI recover without neuroimaging signs or neuropsychological sequelae detected with methods currently applied. Magnetic resonance imaging (MRI) provides several measures that could serve as mTBI biomarkers including the detection of hemosiderin and white matter abnormalities, assessment of white matter integrity derived from diffusion tensor imaging (DTI), and quantitative measures that directly assess neuroanatomy. Improved prediction of neuropsychological outcomes in mTBI may be achieved with the use of targeted neuroimaging markers.

Proton MR spectroscopy correlates diffuse axonal abnormalities with post-concussive symptoms in mild traumatic brain injury

There are no established biomarkers for mild traumatic brain injury (mTBI), in part because post-concussive symptoms (PCS) are subjective and conventional imaging is typically unremarkable. To test whether diffuse axonal abnormalities quantified with three-dimensional (3D) proton magnetic resonance spectroscopic imaging (¹H-MRSI) correlated with patients' PCS, we retrospectively studied 26 mTBI patients (mean Glasgow Coma Scale [GCS] score of 14.7), 18- to 56-year-olds and 13 controls three to 55 days post-injury. All were scanned at 3 Tesla with T1- and T2-weighted MRI and 3D ¹H-MRSI (480 voxels over 360 cm³, ∼30% of the brain). On scan day, patients completed a symptom questionnaire, and those who indicated at least one of the most common subacute mTBI symptoms (headache, dizziness, sleep disturbance, memory deficits, blurred vision) were grouped as PCS-positive. Global gray matter and white matter (GM/WM) absolute concentrations of N-acetylaspartate (NAA), choline (Cho), creatine (Cr) and myo-inositol (mI) in PCS-positive and PCS-negative patients were compared to age- and gender-matched controls using two-way analysis of variance. The results showed that the PCS-negative group (n=11) and controls (n=8) did not differ in any GM or WM metabolite level. The PCS-positive patients (n=15) had lower WM NAA than the controls (n=12; 7.0 ± 0.6 versus 7.9 ± 0.5mM; p=0.0007). Global WM NAA, therefore, showed sensitivity to the TBI sequelae associated with common PCS in patients with mostly normal neuroimaging, as well as GCS scores. This suggests a potential biomarker role in a patient population in which objective measures of injury and symptomatology are currently lacking.

Treatment with an anti-CD11d integrin antibody reduces neuroinflammation and improves outcome in a rat model of repeated concussion

Background

Concussions account for the majority of traumatic brain injuries (TBI) and can result in cumulative damage, neurodegeneration, and chronic neurological abnormalities. The underlying mechanisms of these detrimental effects remain poorly understood and there are presently no specific treatments for concussions. Neuroinflammation is a major contributor to secondary damage following more severe TBI, and recent findings from our laboratory suggest it may be involved in the cumulative properties of repeated concussion. We previously found that an anti-CD11d monoclonal antibody that blocks the CD11d/CD18 integrin and adhesion molecule interaction following severe experimental TBI reduces neuroinflammation, oxidative activity, and tissue damage, and improves functional recovery. As similar processes may be involved in repeated concussion, here we studied the effects of the anti-CD11d treatment in a rat model of repeated concussion.

Methods

Rats were treated 2 h and 24 h after each of three repeated mild lateral fluid percussion injuries with either the CD11d antibody or an isotype-matched control antibody, 1B7. Injuries were separated by a five-day inter-injury interval. After the final treatment and either an acute (24 to 72 h post-injury) or chronic (8 weeks post-injury) recovery period had elapsed, behavioral and pathological outcomes were examined.

Results

The anti-CD11d treatment reduced neutrophil and macrophage levels in the injured brain with concomitant reductions in lipid peroxidation, astrocyte activation, amyloid precursor protein accumulation, and neuronal loss. The anti-CD11d treatment also improved outcome on tasks of cognition, sensorimotor ability, and anxiety.

Conclusions

These findings demonstrate that reducing inflammation after repeated mild brain injury in rats leads to improved behavioral outcomes and that the anti-CD11d treatment may be a viable therapy to improve post-concussion outcomes.