Cognitive impairment after traumatic brain injury: The role of MRI and possible pathological basis

Transcutaneous Cervical Vagus Nerve Magnetic Stimulation in Patients With Traumatic Brain Injury: A Feasibility Study

OBJECTIVES

Transcutaneous vagus nerve stimulation has shown promising results in improving cognitive and motor function after stroke. However, to our knowledge, there have been no studies in the modulation of the cervical vagus nerve using repetitive transcranial magnetic stimulation (rTMS) in patients with traumatic brain injury (TBI) with cognitive dysfunction. Thus, we conducted a single-arm feasibility trial to assess the safety and effectiveness of rTMS of the vagus nerve in patients with TBI.

MATERIALS AND METHODS

We enrolled ten patients with TBI and administered half-hour vagus nerve magnetic stimulation (VNMS) sessions for ten days to evaluate the feasibility of the treatment. The Montreal cognitive assessment-Beijing (MoCA-B), the Digit Span Test, and the Auditory Verbal Learning Test (AVLT) were used to measure cognitive function before and after the VNMS treatment. Physiological parameters of all subjects were assessed by electrocardiogram.

RESULTS

The findings showed that daily half-hour VNMS for ten days was feasible in patients with TBI, with minimal side effects and no clinically significant effects on physiological parameters. Eight patients showed improvement in MoCA-B, and five patients showed improvement in immediate memory as measured by AVLT.

CONCLUSIONS

We conclude that VNMS is a safe and feasible treatment option for patients with TBI with cognitive dysfunction. However, further controlled studies are necessary to establish the efficacy of VNMS in promoting cognitive recovery after TBI.

SIGNIFICANCE

This study is, to our knowledge, the first study to investigate the feasibility of VNMS for cognitive dysfunction in patients with TBI. Our findings offer the possibility of rTMS applied to the vagus nerve in clinical practice.

MRI volumetry and diffusion tensor imaging for diagnosis and follow-up of late post-traumatic injuries

BACKGROUND

Traumatic Brain Injury (TBI) is a major cause of acquired disability and can cause devastating and progressive post-traumatic encephalopathy. TBI is a dynamic condition that continues to evolve over time. A better understanding of the pathophysiology of these late lesions is important for the development of new therapeutic strategies.

OBJECTIVES

The primary objective was to compare the ability of fluid-attenuated reversion recovery (FLAIR) and diffusion tensor imaging (DTI) magnetic resonance imaging (MRI) markers to identify participants with a Glasgow outcome scale extended (GOS-E) score of 7-8, up to 10 years after their original TBI. The secondary objective was to study the brain regionalization of DTI markers. Finally, we analyzed the evolution of late-developing brain lesions using repeated MRI images, also taken up to 10 years after the TBI.

METHODS

In this retrospective study, participants were included from a cohort of people hospitalized following a severe TBI. Following their discharge, they were followed-up and clinically assessed, including a DTI-MRI scan, between 2012 and 2016. We performed a cross-sectional analysis on 97 participants at a median (IQR) of 5 years (3-6) post-TBI, and a further post-TBI longitudinal analysis over 10 years on a subpopulation (n = 17) of the cohort.

RESULTS

Although the area under the curve (AUC) of FLAIR, fractional anisotropy (FA), and mean diffusivity (MD) were not significantly different, only the AUC of FA was statistically greater than 0.5. In addition, only the FA was correlated with clinical outcomes as assessed by GOS-E score (P<10-4). On the cross-sectional analysis, DTI markers allowed study post-TBI white matter lesions by region. In the longitudinal subpopulation analysis, the observed number of brain lesions increased for the first 5 years post-TBI, before stabilizing over the next 5 years.

CONCLUSIONS

This study has shown for the first time that post-TBI lesions can present in a two-phase evolution. These results must be confirmed in larger studies. French Data Protection Agency (Commission nationale de l'informatique et des libertés; CNIL) study registration no: 1934708v0.

Associations of MRI-Derived Glymphatic System Impairment With Global White Matter Damage and Cognitive Impairment in Mild Traumatic Brain Injury: A DTI-ALPS Study

BACKGROUND

Assessing the glymphatic function using diffusion tensor image analysis along the perivascular space (DTI-ALPS) may be helpful for mild traumatic brain injury (mTBI) management.

PURPOSE

To assess glymphatic function using DTI-ALPS and its associations with global white matter damage and cognitive impairment in mTBI.

STUDY TYPE

Prospective.

POPULATION

Thirty-four controls (44.1% female, mean age 49.2 years) and 58 mTBI subjects (43.1% female, mean age 48.7 years), including uncomplicated mTBI (N = 32) and complicated mTBI (N = 26).

FIELD STRENGTH/SEQUENCE

3-T, single-shot echo-planar imaging sequence.

ASSESSMENT

Magnetic resonance imaging (MRI) was done within 1 month since injury. DTI-ALPS was performed to assess glymphatic function, and peak width of skeletonized mean diffusivity (PSMD) was used to assess global white matter damage. Cognitive tests included Auditory Verbal Learning Test and Digit Span Test (forward and backward).

STATISTICAL TESTS

Neuroimaging findings comparisons were done between mTBI and control groups. Partial correlation and multivariable linear regression assessed the associations between DTI-ALPS, PSMD, and cognitive impairment. Mediation effects of PSMD on the relationship between DTI-ALPS and cognitive impairment were explored. P-value <0.05 was considered statistically significant, except for cognitive correlational analyses with a Bonferroni-corrected P-value set at 0.05/3 ≈ 0.017.

RESULTS

mTBI showed lower DTI-ALPS and higher PSMD, especially in complicated mTBI. DTI-ALPS was significantly correlated with verbal memory (r = 0.566), attention abilities (r = 0.792), executive function (r = 0.618), and PSMD (r = -0.533). DTI-ALPS was associated with verbal memory (β = 8.77, 95% confidence interval [CI] 5.00, 12.54), attention abilities (β = 5.67, 95% CI 4.56, 6.97), executive function (β = 2.34, 95% CI 1.49, 3.20), and PSMD (β = -0.79, 95% CI -1.15, -0.43). PSMD mediated 46.29%, 20.46%, and 24.36% of the effects for the relationship between DTI-ALPS and verbal memory, attention abilities, and executive function.

DATA CONCLUSION

Glymphatic function may be impaired in mTBI reflected by DTI-ALPS. Glymphatic dysfunction may cause cognitive impairment related to global white matter damage after mTBI.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 2.

Application of Delayed Contrast Extravasation Magnetic Resonance Imaging for Depicting Subtle Blood-Brain Barrier Disruption in a Traumatic Brain Injury Model

The blood-brain barrier (BBB) is composed of brain microvasculature that provides selective transport of solutes from the systemic circulation into the central nervous system to protect the brain and spinal microenvironment. Damage to the BBB in the acute phase after traumatic brain injury (TBI) is recognized as a major underlying mechanism leading to secondary long-term damage. Because of the lack of technological ability to detect subtle BBB disruption (BBBd) in the chronic phase, however, the presence of chronic BBBd is disputable. Thus, the dynamics and course of long-term BBBd post-TBI remains elusive. Thirty C57BL/6 male mice subjected to TBI using our weight drop closed head injury model and 19 naïve controls were scanned by magnetic resonance imaging (MRI) up to 540 days after injury. The BBB maps were calculated from delayed contrast extravasation MRI (DCM) with high spatial resolution and high sensitivity to subtle BBBd, enabling depiction and quantification of BBB permeability. At each time point, 2-6 animals were sacrificed and their brains were extracted, sectioned, and stained for BBB biomarkers including: blood microvessel coverage by astrocyte using GFAP, AQP4, ZO-1 gaps, and IgG leakage. We found that DCM provided depiction of subtle yet significant BBBd up to 1.5 years after TBI, with significantly higher sensitivity than standard contrast-enhanced T1-weighted and T2-weighted MRI (BBBd volumes main effect DCM/T1/T2 p < 0.0001 F(2,70) = 107.3, time point p < 0.0001 F(2,133, 18.66) = 23.53). In 33% of the cases, both in the acute and chronic stages, there was no detectable enhancement on standard T1-MRI, nor detectable hyperintensities on T2-MRI, whereas DCM showed significant BBBd volumes. The BBBd values of TBI mice at the chronic stage were found significantly higher compared with age matched naïve animals at 30, 60, and 540 days. The calculated BBB maps were histologically validated by determining significant correlation between the calculated levels of disruption and a diverse set of histopathological parameters obtained from different brain regions, presenting different components of the BBB. Cumulative evidence from recent years points to BBBd as a central component of the pathophysiology of TBI. Therefore, it is expected that routine use of highly sensitive non-invasive techniques to measure BBBd, such as DCM with advanced analysis methods, may enhance our understanding of the changes in BBB function after TBI. Application of the DCM technology to other CNS disorders, as well as to normal aging, may shed light on the involvement of chronic subtle BBBd in these conditions.

Treatment effects of N-acetyl cysteine on resting-state functional MRI and cognitive performance in patients with chronic mild traumatic brain injury: a longitudinal study

Mild traumatic brain injury (mTBI) is a significant public health concern, specially characterized by a complex pattern of abnormal neural activity and functional connectivity. It is often associated with a broad spectrum of short-term and long-term cognitive and behavioral symptoms including memory dysfunction, headache, and balance difficulties. Furthermore, there is evidence that oxidative stress significantly contributes to these symptoms and neurophysiological changes. The purpose of this study was to assess the effect of N-acetylcysteine (NAC) on brain function and chronic symptoms in mTBI patients. Fifty patients diagnosed with chronic mTBI participated in this study. They were categorized into two groups including controls (CN, n = 25), and patients receiving treatment with N-acetyl cysteine (NAC, n = 25). NAC group received 50 mg/kg intravenous (IV) medication once a day per week. In the rest of the week, they took one 500 mg NAC tablet twice per day. Each patient underwent rs-fMRI scanning at two timepoints including the baseline and 3 months later at follow-up, while the NAC group received a combination of oral and IV NAC over that time. Three rs-fMRI metrics were measured including fractional amplitude of low frequency fluctuations (fALFF), degree centrality (DC), and functional connectivity strength (FCS). Neuropsychological tests were also assessed at the same day of scanning for each patient. The alteration of rs-fMRI metrics and cognitive scores were measured over 3 months treatment with NAC. Then, the correlation analysis was executed to estimate the association of rs-fMRI measurements and cognitive performance over 3 months (p < 0.05). Two significant group-by-time effects demonstrated the changes of rs-fMRI metrics particularly in the regions located in the default mode network (DMN), sensorimotor network, and emotional circuits that were significantly correlated with cognitive function recovery over 3 months treatment with NAC (p < 0.05). NAC appears to modulate neural activity and functional connectivity in specific brain networks, and these changes could account for clinical improvement. This study confirmed the short-term therapeutic efficacy of NAC in chronic mTBI patients that may contribute to understanding of neurophysiological effects of NAC in mTBI. These findings encourage further research on long-term neurobehavioral assessment of NAC assisting development of therapeutic plans in mTBI.

Maximizing the Clinical Value of Blood-Based Biomarkers for Mild Traumatic Brain Injury

Mild traumatic brain injury (TBI) and concussion can have serious consequences that develop over time with unpredictable levels of recovery. Millions of concussions occur yearly, and a substantial number result in lingering symptoms, loss of productivity, and lower quality of life. The diagnosis may not be made for multiple reasons, including due to patient hesitancy to undergo neuroimaging and inability of imaging to detect minimal damage. Biomarkers could fill this gap, but the time needed to send blood to a laboratory for analysis made this impractical until point-of-care measurement became available. A handheld blood test is now on the market for diagnosis of concussion based on the specific blood biomarkers glial fibrillary acidic protein (GFAP) and ubiquitin carboxyl terminal hydrolase L1 (UCH-L1). This paper discusses rapid blood biomarker assessment for mild TBI and its implications in improving prediction of TBI course, avoiding repeated head trauma, and its potential role in assessing new therapeutic options. Although we focus on the Abbott i-STAT TBI plasma test because it is the first to be FDA-cleared, our discussion applies to any comparable test systems that may become available in the future. The difficulties in changing emergency department protocols to include new technology are addressed.

PRMT7 can prevent neurovascular uncoupling, blood-brain barrier permeability, and mitochondrial dysfunction in repetitive and mild traumatic brain injury

Mild traumatic brain injury (TBI) comprises the largest percentage of TBI-related injuries, with pathophysiological and functional deficits that persist in a subset of TBI patients. In our three-hit paradigm of repetitive and mild traumatic brain injury (rmTBI), we observed neurovascular uncoupling via decreased red blood cell velocity, microvessel diameter, and leukocyte rolling velocity 3 days post-rmTBI via intra-vital two-photon laser scanning microscopy. Furthermore, our data suggest increased blood-brain barrier (BBB) permeability (leakage), with corresponding decrease in junctional protein expression post-rmTBI. Mitochondrial oxygen consumption rates (measured via Seahorse XFe24) were also altered 3 days post-rmTBI, along with disrupted mitochondrial dynamics of fission and fusion. Overall, these pathophysiological findings correlated with decreased protein arginine methyltransferase 7 (PRMT7) protein levels and activity post-rmTBI. Here, we increased PRMT7 levels in vivo to assess the role of the neurovasculature and mitochondria post-rmTBI. In vivo overexpression of PRMT7 using a neuronal specific AAV vector led to restoration of neurovascular coupling, prevented BBB leakage, and promoted mitochondrial respiration, altogether to suggest a protective and functional role of PRMT7 in rmTBI.

Emergence delirium and postoperative delirium associated with high plasma NfL and GFAP: an observational study

Background

Neuroinflammation and neuronal injury have been reported to be associated with the development of postoperative delirium in both preclinical and clinical settings. This study aimed to investigate the potential correlation between biomarkers of neurofilament light chain and glial fibrillary acidic protein and emergence and postoperative delirium in elderly patients undergoing surgery.

Methods

Patients who developed emergence delirium (n = 30) and postoperative delirium (n = 32), along with their matched controls, were enrolled after obtaining ethics approval and written informed consent. Delirium was assessed using the Confusion Assessment Method for the Intensive Care Unit or Confusion Assessment Method scale, and blood samples were collected before and after surgery for plasma neurofilament light chain and glial fibrillary acidic protein measurements using a single-molecule array.

Results

The study found that in patients with emergence delirium, the increase in plasma neurofilament light chain protein levels during surgery was significantly higher than in non-delirium patients (P = 0.002). Additionally, in patients with postoperative delirium, both the increase in plasma neurofilament light chain protein levels (P < 0.001) and the increase in plasma glial fibrillary acidic protein levels during surgery (P = 0.008) were significantly higher than in non-delirium patients. Multivariate logistic regression analysis showed that the increase in plasma neurofilament light chain protein was associated with emergence delirium (adjusted OR = 1.872, P = 0.005), and the increase in plasma glial fibrillary acidic protein was associated with postoperative delirium (adjusted OR = 1.419, P = 0.016). Moreover, the American Society of Anesthesiologists Physical Status Classification and surgical duration were also found to be associated with delirium in elderly patients.

Conclusion

Our findings suggest that emergence delirium is linked to elevated levels of neurofilament light chain, a biomarker of axonal injury, during surgery. Furthermore, in addition to axonal injury, postoperative delirium was also associated with an increase in glial fibrillary acidic protein, a marker of astrocyte activation.

Astrocyte Endfeet in Brain Function and Pathology: Open Questions

Astrocyte endfeet enwrap the entire vascular tree within the central nervous system, where they perform important functions in regulating the blood-brain barrier (BBB), cerebral blood flow, nutrient uptake, and waste clearance. Accordingly, astrocyte endfeet contain specialized organelles and proteins, including local protein translation machinery and highly organized scaffold proteins, which anchor channels, transporters, receptors, and enzymes critical for astrocyte-vascular interactions. Many neurological diseases are characterized by the loss of polarization of specific endfoot proteins, vascular dysregulation, BBB disruption, altered waste clearance, or, in extreme cases, loss of endfoot coverage. A role for astrocyte endfeet has been demonstrated or postulated in many of these conditions. This review provides an overview of the development, composition, function, and pathological changes of astrocyte endfeet and highlights the gaps in our knowledge that future research should address.

Boswellia serrata extract shows cognitive benefits in a double-blind, randomized, placebo-controlled pilot clinical trial in individuals who suffered traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is a major cause of death and disability. TBI can result in neuropsychiatric and cognitive problems as well as neurodegenerative pathologies that can appear right after or develop and persist years after injury.

METHOD

We conducted a double-blind, randomized, placebo-controlled clinical trial on patients who suffered from TBI three months to three years ago. The patients were randomized to placebo (n = 34) or K-Vie™ group (n = 46) for a treatment period of 3 months. The main primary outcomes include cognitive assessment in the Rey Auditory Verbal Learning Test-Recognition Test (RAVLT), Wechsler adult intelligence Digit Symbol Substitution Test (DSST) and trail-making test part B (TMT-B). Assessments were performed at baseline and at the month 3 follow-up visit. Linear mixed models were carried out to evaluate cognitive changes from baseline across all cognitive assessment tests.

RESULT

The current study showed significant (p < 0.05) improvement in cognitive function of patients who were given K-Vie™ compared with placebo across the RAVLT, DSST and TMT-B performance assessments. A larger cohort would be beneficial to further confirm the clinical utility of K-Vie™ and assess its effects in acute phases of TBI.

Cognitive impairment in mild traumatic brain injury: a diffusion kurtosis imaging and volumetric study

BACKGROUND

A significant number of patients with mild traumatic brain injury (mTBI) would experience cognitive deficit.

PURPOSE

To investigate the brain structural changes in sub-acute mTBI by diffusion kurtosis imaging (DKI) and volumetric analysis, and to assess the relationship between brain structural changes and cognitive functions.

MATERIAL AND METHODS

A total of 23 patients with sub-acute mTBI and 24 control participants were recruited. All the participants underwent examinations of neuropsychological tests, DKI, and magnetic resonance imaging (MRI)-based morphological scans. Images were investigated using whole brain-based analysis and further regions of interest-based analysis for subcortical nuclei. The neuropsychological tests were compared between the mTBI and the control group. Correlation analysis was performed to examine the relationship between gray matter (GM) volume, DKI parameters, and cognitive functions.

RESULTS

Compared with control participants, mTBI patients performed worse in the domains of verbal memory, attention and executive function (P < 0.05). No regional GM volume differences were observed between the mTBI and control groups (P > 0.05). Using DKI, patients with mTBI showed lower mean kurtosis (MK) in widespread white matter (WM) regions and several subcortical nuclei (P < 0.05), and higher mean diffusivity (MD) in the right pallidum (P < 0.05). Lower MK value of multiple WM regions and several subcortical nuclei correlated with cognitive impairment (P < 0.05).

CONCLUSION

DKI was sensitive in detecting brain microstructural changes in patients with sub-acute mTBI showing lower MK value in widespread WM regions and several subcortical nuclei, which were statistically associated with cognitive deficits.

The Effect of Repetitive Transcranial Magnetic Stimulation (rTMS) on Cognition in Patients With Traumatic Brain Injury: A Protocol for a Randomized Controlled Trial

Cognitive impairment, defined as a decline in memory and executive function, is one of the most severe complications of traumatic brain injury (TBI). Patients with TBI are often unable to return to work due to cognitive impairment and their overall quality of life is reduced. TBI can bring a serious economic burden to patient's families and to society. Reported findings on the efficacy of repetitive transcranial magnetic stimulation (rTMS) in improving cognitive impairment following TBI are inconsistent. The purpose of the proposed study is to investigate whether rTMS can improve memory and executive function in patients with TBI. Herein, we propose a prospective randomized placebo-controlled (rTMS, sham rTMS, cognitive training), parallel-group, single-center trial. 36 participants with a TBI occurring at least 6 months prior will be recruited from an inpatient rehabilitation center. Participants will be randomly assigned to the real rTMS, sham rTMS, or cognitive training groups with a ratio of 1:1:1. A 20-session transcranial magnetic stimulation protocol will be applied to the left and right dorsolateral prefrontal cortices (DLPFC) at frequencies of 10 Hz and 1 Hz, respectively. Neuropsychological assessments will be performed at four time points: baseline, after the 10th rTMS session, after the 20th rTMS session, and 30 days post-intervention. The primary outcome is change in executive function assessed using the Shape Trail Test (STT). The secondary outcome measures are measures from neuropsychological tests: the Hopkins Verbal Learning Test (HVLT), the Brief Visuospatial Memory Test (BVMT), the Digit Span Test (DST). We report on positive preliminary results in terms of improving memory and executive function as well as beneficial changes in brain connectivity among TBI patients undergoing rTMS and hypothesize that we will obtain similar results in the proposed study.

Neurocognitive correlates of probable posttraumatic stress disorder following traumatic brain injury

Introduction

Neurocognitive problems associated with posttraumatic stress disorder (PTSD) can interact with impairment resulting from traumatic brain injury (TBI).

Research question

We aimed to identify neurocognitive problems associated with probable PTSD following TBI in a civilian sample.

Material and methods

The study is part of the CENTER-TBI project (Collaborative European Neurotrauma Effectiveness Research) that aims to better characterize TBI. For this cross-sectional study, we included patients of all severities aged over 15, and a Glasgow Outcome Score Extended (GOSE) above 3. Participants were assessed at six months post-injury on the PTSD Checklist-5 (PCL-5), the Trail Making Test (TMT), the Rey Auditory Verbal Learning Test (RAVLT) and the Cambridge Neuropsychological Test Automated Battery (CANTAB). Primary analysis was a complete case analysis. Regression analyses were performed to investigate the association between the PCL-5 and cognition.

Results

Of the 1134 participants included in the complete case analysis, 13.5% screened positive for PTSD. Probable PTSD was significantly associated with higher TMT-(B-A) (OR ​= ​1.35, 95% CI: 1.14–1.60, p ​< ​.001) and lower RAVLT-delayed recall scores (OR ​= ​0.74, 95% CI: 0.61–0.91, p ​= ​.004) after controlling for age, sex, psychiatric history, baseline Glasgow Coma Scale and education.

Discussion and conclusion

Poorer performance on cognitive tests assessing task switching and, to a lesser extent, delayed verbal recall is associated with probable PTSD in civilians who have suffered TBI.

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Six months after traumatic brain injury 13.5% of people screen positive for PTSD.

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Task switching performance and verbal memory are related to probable PTSD.

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PTSD severity is related to processing speed and task switching performance.

Mild Traumatic Brain Injury/Concussion Initiates an Atypical Astrocyte Response Caused by Blood-Brain Barrier Dysfunction

Mild traumatic brain injury/concussion (mTBI) accounts for 70-90% of all reported TBI cases and causes long-lasting neurological consequences in 10-40% of patients. Recent clinical studies revealed increased blood-brain barrier (BBB) permeability in mTBI patients, which correlated with secondary damage after mTBI. However, the cascade of cellular events initiated by exposure to blood-borne factors resulting in sustained damage is not fully understood. We previously reported that astrocytes respond atypically to mTBI, rapidly losing many proteins essential to their homeostatic function, while classic scar formation does not occur. Here, we tested the hypothesis that mTBI-induced BBB damage causes atypical astrocytes through exposure to blood-borne factors. Using an mTBI mouse model, two-photon imaging, an endothelial cell-specific genetic ablation approach, and serum-free primary astrocyte cultures, we demonstrated that areas with atypical astrocytes coincide with BBB damage and that exposure of astrocytes to plasma proteins is sufficient to initiate loss of astrocyte homeostatic proteins. Although mTBI resulted in frequent impairment of both physical and metabolic BBB properties and leakage of small-sized blood-borne factors, deposition of the coagulation factor fibrinogen or vessel rupture were rare. Surprisingly, even months after mTBI, BBB repair did not occur in areas with atypical astrocytes. Together, these findings implicate that even relatively small BBB disturbances are sustained long term, and render nearby astrocytes dysfunctional, likely at the cost of neuronal health and function.

Saccade and Fixation Eye Movements During Walking in People With Mild Traumatic Brain Injury

Background: Clinical and laboratory assessment of people with mild traumatic brain injury (mTBI) indicate impairments in eye movements. These tests are typically done in a static, seated position. Recently, the use of mobile eye-tracking systems has been proposed to quantify subtle deficits in eye movements and visual sampling during different tasks. However, the impact of mTBI on eye movements during functional tasks such as walking remains unknown.

Objective: Evaluate differences in eye-tracking measures collected during gait between healthy controls (HC) and patients in the sub-acute stages of mTBI recovery and to determine if there are associations between eye-tracking measures and gait speed.

Methods: Thirty-seven HC participants and 67individuals with mTBI were instructed to walk back and forth over 10-m, at a comfortable self-selected speed. A single 1-min trial was performed. Eye-tracking measures were recorded using a mobile eye-tracking system (head-mounted infra-red Tobbii Pro Glasses 2, 100 Hz, Tobii Technology Inc. VA, United States). Eye-tracking measures included saccadic (frequency, mean and peak velocity, duration and distance) and fixation measurements (frequency and duration). Gait was assessed using six inertial sensors (both feet, sternum, right wrist, lumbar vertebrae and the forehead) and gait velocity was selected as the primary outcome. General linear model was used to compare the groups and association between gait and eye-tracking outcomes were explored using partial correlations.

Results: Individuals with mTBI showed significantly reduced saccade frequency (p = 0.016), duration (p = 0.028) and peak velocity (p = 0.032) compared to the HC group. No significant differences between groups were observed for the saccade distance, fixation measures and gait velocity (p > 0.05). A positive correlation was observed between saccade duration and gait velocity only for participants with mTBI (p = 0.025).

Conclusion: Findings suggest impaired saccadic eye movement, but not fixations, during walking in individuals with mTBI. These findings have implications in real-world function including return to sport for athletes and return to duty for military service members. Future research should investigate whether or not saccade outcomes are influenced by the time after the trauma and rehabilitation.

S100B, GFAP, UCH-L1 and NSE as predictors of abnormalities on CT imaging following mild traumatic brain injury: a systematic review and meta-analysis of diagnostic test accuracy

Biomarkers such as calcium channel binding protein S100 subunit beta (S100B), glial fibrillary acidic protein (GFAP), ubiquitin c-terminal hydrolase L1 (UCH-L1) and neuron-specific enolase (NSE) have been proposed to aid in screening patients presenting with mild traumatic brain injury (mTBI). As such, we aimed to characterise their accuracy at various thresholds. MEDLINE, SCOPUS and EMBASE were searched, and articles reporting the diagnostic performance of included biomarkers were eligible for inclusion. Risk of bias was assessed using the QUADAS-II criteria. A meta-analysis was performed to assess the predictive value of biomarkers for imaging abnormalities on CT. A total of 2939 citations were identified, and 38 studies were included. Thirty-two studies reported data for S100B. At its conventional threshold of 0.1 μg/L, S100B had a pooled sensitivity of 91% (95%CI 87-94) and a specificity of 30% (95%CI 26-34). The optimal threshold for S100B was 0.72 μg/L, with a sensitivity of 61% (95% CI 50-72) and a specificity of 69% (95% CI 64-74). Nine studies reported data for GFAP. The optimal threshold for GFAP was 626 pg/mL, at which the sensitivity was 71% (95%CI 41-91) and specificity was 71% (95%CI 43-90). Sensitivity of GFAP was maximised at a threshold of 22 pg/mL, which had a sensitivity of 93% (95%CI 73-99) and a specificity of 36% (95%CI 12-68%). Three studies reported data for NSE and two studies for UCH-L1, which precluded meta-analysis. There is evidence to support the use of S100B as a screening tool in mild TBI, and potential advantages to the use of GFAP, which requires further investigation.

Gastrointestinal Decompression on Computed Tomography Examination for Patients with Craniocerebral Injury

Objective: Patients with craniocerebral injury usually accompanied by intracranial hypertension and vomiting, which affect the effect of CT scanning. The aim of this study was to discuss the application effects of gastrointestinal decompression on computed tomography (CT) examination for patients with craniocerebral injury. Methods: A total of 80 patients with craniocerebral injury in our hospital were randomly selected and divided into control and observation groups, 40 cases in each group. The observation group was given gastrointestinal decompression before the CT examination, while the control group received routine examination. The success rate of CT examination, CT scanning effect, examination, and complication during scanning were recorded and compared in two groups. Results: The one-time success rate (100.0%) of CT examination was 100.0% (40/40) in the observation group was significantly higher than the rate in the control group (82.5%, P = 0.034). The CT examination clearly showed in the types of craniocerebral injury, the brain tissue injury, the ventricular compression and the midline displacement. The CT examination time of observation group was shorter than that of control group (P < 0.001), while there was no significant difference in the whole examination time spent on both gastrointestinal decompression operation and CT examination between the two groups (P = 0.301). In the observation group, there was only 1 case of retching, and no cases of vomiting or aspiration during scanning. The incidence of various complications in observation group was significantly lesser than the incidence in control group (P = 0.034). Conclusions: Continue gastrointestinal decompression can significantly reduce the incidence of vomiting and other complication in patients with craniocerebral injury during CT examination, reduce the CT examination time, and improve the success rate of one-time scanning.

Quantitative multimodal imaging in traumatic brain injuries producing impaired cognition

PURPOSE OF REVIEW

Cognitive impairments are a devastating long-term consequence following traumatic brain injury (TBI). This review provides an update on the quantitative mutimodal neuroimaging studies that attempt to elucidate the mechanism(s) underlying cognitive impairments and their recovery following TBI.

RECENT FINDINGS

Recent studies have linked individual specific behavioural impairments and their changes over time to physiological activity and structural changes using EEG, PET and MRI. Multimodal studies that combine measures of physiological activity with knowledge of neuroanatomical and connectivity damage have also illuminated the multifactorial function-structure relationships that underlie impairment and recovery following TBI.

SUMMARY

The combined use of multiple neuroimaging modalities, with focus on individual longitudinal studies, has the potential to accurately classify impairments, enhance sensitivity of prognoses, inform targets for interventions and precisely track spontaneous and intervention-driven recovery.

Utility of a pediatric fast magnetic resonance imaging protocol as surveillance scanning for traumatic brain injury

OBJECTIVE

Traumatic brain injury (TBI) is a prevalent pediatric pathology in the modern emergency department. Computed tomography (CT) is utilized for detection of TBI and can result in cumulatively high radiation exposure. Recently, a fast brain magnetic resonance imaging (fbMRI) protocol has been employed for rapid imaging of hydrocephalus in pediatric patients. The authors investigate the utility of a modified trauma-focused fbMRI (t-fbMRI) protocol as an alternative to surveillance CT in the setting of acute TBI in pediatric patients, thus reducing radiation exposure while improving diagnostic yield.

METHODS

A retrospective review was performed at the authors' institution for all pediatric patients who had undergone t-fbMRI within 72 hours of an initial CT scan, using a 1.5- or 3-T MR scanner for trauma indications. Forty patients met the study inclusion criteria. The authors performed a comparison of findings on the reads of CT and fbMRI, and a board-certified neuroradiologist conducted an independent review of both modalities.

RESULTS

T-fbMRI outperformed CT in specificity, sensitivity, and negative predictive value for all injury pathologies measured, except for skull fractures. T-fbMRI demonstrated a sensitivity of 100% in the detection of extraaxial bleed, intraventricular hemorrhage, and subarachnoid hemorrhage and had a sensitivity of 78% or greater for epidural hematoma, subdural hematoma, and intraparenchymal hemorrhage. T-fbMRI yielded a specificity of 100% for all types of intracranial hemorrhages, with a corresponding negative predictive value that exceeded that for CT.

CONCLUSIONS

In pediatric populations, the t-fbMRI protocol provides a valid alternative to CT in the surveillance of TBI and intracranial hemorrhage. Although not as sensitive in the detection of isolated skull fractures, t-fbMRI can be used to monitor pathologies implicated in TBI patients while minimizing radiation exposure from traditional surveillance imaging.

Neuroinflammation and Hypothalamo-Pituitary Dysfunction: Focus of Traumatic Brain Injury

The incidence of traumatic brain injury (TBI) has increased over the last years with an important impact on public health. Many preclinical and clinical studies identified multiple and heterogeneous TBI-related pathophysiological mechanisms that are responsible for functional, cognitive, and behavioral alterations. Recent evidence has suggested that post-TBI neuroinflammation is responsible for several long-term clinical consequences, including hypopituitarism. This review aims to summarize current evidence on TBI-induced neuroinflammation and its potential role in determining hypothalamic-pituitary dysfunctions.

Emerging Utility of Applied Magnetic Resonance Imaging in the Management of Traumatic Brain Injury

Traumatic brain injury (TBI) is a widespread and expensive problem globally. The standard diagnostic workup for new TBI includes obtaining a noncontrast computed tomography image of the head, which provides quick information on operative pathologies. However, given the limited sensitivity of computed tomography for identifying subtle but meaningful changes in the brain, magnetic resonance imaging (MRI) has shown better utility for ongoing management and prognostication after TBI. In recent years, advanced applications of MRI have been further studied and are being implemented as clinical tools to help guide care. These include functional MRI, diffusion tensor imaging, MR perfusion, and MR spectroscopy. In this review, we discuss the scientific basis of each of the above techniques, the literature supporting their use in TBI, and how they may be clinically implemented to improve the care of TBI patients.

Global mean diffusivity: A radiomarker discriminating good outcome long term after traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is a chronic pathology responsible for cognitive disorders impacting outcome. Global clinical outcome several years after TBI may be associated with anatomical sequelae. Anatomical lesions are not well described because characterizing diffuse axonal injury and brain atrophy require using specific MRI sequences with quantitative measures. The best radiologic parameter to describe the lesions long term after TBI is not known.

OBJECTIVE

We aimed to first, assess the global volumetric and diffusion parameters related to long-term outcome after TBI and second, define the most discriminating parameter.

METHODS

In this observational study, we included 96 patients with severe TBI and 22 healthy volunteers. The mean delay after TBI was 63.2 months [range 31-119]. The Glasgow Outcome Scale Extended (GOS-E) was used to assess the global long-term clinical outcome. All patients underwent multimodal MRI with measures of brain volume, ventricle volume, global fractional anisotropy (FA) and global mean diffusivity (MD).

RESULTS

All 96 participants had significant impairment in global FA, global MD, brain volume and ventricle volume as compared with the 22 controls (P<0.01). Only global MD significantly differed between the "good recovery" group (GOS-E score 7-8) and the other two groups: GOS-E scores 3-4 and 5-6. Brain volume significantly differed between the GOS-E 7-8 and 3-4 groups. Global MD was the most discriminating radiological parameter for the "good recovery" group versus other patients, long term after TBI. FA appeared less relevant at this time. Global atrophy was higher in patients than controls but lacked reliability to discriminate groups of patients.

CONCLUSION

Global mean diffusivity seems a more promising radiomarker than global FA for discriminating good outcome long term after TBI. Further work is needed to understand the evolution of these long-term radiological parameters after TBI.

Use of Medical Cannabis to Treat Traumatic Brain Injury

There is not a single pharmacological agent with demonstrated therapeutic efficacy for traumatic brain injury (TBI). With recent legalization efforts and the growing popularity of medical cannabis, patients with TBI will inevitably consider medical cannabis as a treatment option. Pre-clinical TBI research suggests that cannabinoids have neuroprotective and psychotherapeutic properties. In contrast, recreational cannabis use has consistently shown to have detrimental effects. Our review identified a paucity of high-quality studies examining the beneficial and adverse effects of medical cannabis on TBI, with only a single phase III randomized control trial. However, observational studies demonstrate that TBI patients are using medical and recreational cannabis to treat their symptoms, highlighting inconsistencies between public policy, perception of potential efficacy, and the dearth of empirical evidence. We conclude that randomized controlled trials and prospective studies with appropriate control groups are necessary to fully understand the efficacy and potential adverse effects of medical cannabis for TBI.

Niche Cells Crosstalk In Neuroinflammation After Traumatic Brain Injury

Traumatic brain injury (TBI) is recognized as the disease with high morbidity and disability around world in spite of the work ongoing in neural protection. Due to heterogeneity among the patients, it's still hard to acquire satisfying achievements in clinic. Neuroinflammation, which exists since primary injury occurs, with elusive duality, appear to be of significance from recovery of injury to neurogenesis. In recent years, studied have revealed that communication in neurogenic niche is more than “cell to cell” communication, and study on NSCs represent it as central role in the progress of neural regeneration. Hence, the neuroinflammation-affecting crosstalk after TBI, and clarifying definitive role of NSCs in the course of regeneration is a promising subject for researchers, for its great potential in overcoming the frustrating status quo in clinic, promoting welfare of TBI patient.

CORM-3 ameliorates neurodegeneration in the amygdala and improves depression- and anxiety-like behavior in a rat model of combined traumatic brain injury and hemorrhagic shock

OBJECTIVE

Emotional disturbances characterized by depression and anxiety among survivors of traumatic brain injury (TBI) impact the quality of life severely. Currently, there is a lack of effective drug treatment for neurodegeneration induced by TBI, mainly due to failed efficacy of compounds such as corticosteroids, calcium channel blockers, and excitatory amino acid inhibitors. Thus, we sought to continue with our investigation on CORM-3, a water-soluble exogenous carbon monoxide-releasing molecule with excellent anti-inflammatory actions employed in a previous study using a rat model of combined TBI with hemorrhage shock and resuscitation (HSR).

METHODS

Rats were administrated with CORM-3 after induction of TBI and HSR and examined depressive and anxiety-like behaviors, along with cerebral function employing functional magnetic resonance imaging (MRI) 30-days post-trauma. Also, the following variables were measured: 1) neuronal pyroptosis and apoptosis 24 h post-trauma, 2) the roles of PKG-ERK1/2 signaling pathways with the use of the protein kinase G (PKG) specific inhibitor, KT5823.

RESULTS

CORM-3-treated rats displayed significant ameliorated depression- and anxiety-like behaviors, improved cerebral blood flow, and fractional anisotropy (FA), showed less neuronal pyroptosis and apoptosis in the amygdala, and upregulated the phosphorylation of Vasodilator-stimulated phosphoprotein (VASP) and ERK1/2. However, CORM-3 neuroprotective effects against trauma were only partially reversed by KT5823.

CONCLUSION

CORM-3 ameliorated the emotional deficits and neuronal death induced in the amygdala post-TBI and HSR rat model, and PKG-ERK1/2 signaling might be implicated in the underlying mechanism.

Blood-Brain Barrier Disruption in Mild Traumatic Brain Injury Patients with Post-Concussion Syndrome: Evaluation with Region-Based Quantification of Dynamic Contrast-Enhanced MR Imaging Parameters Using Automatic Whole-Brain Segmentation

Objective

This study aimed to investigate the blood-brain barrier (BBB) disruption in mild traumatic brain injury (mTBI) patients with post-concussion syndrome (PCS) using dynamic contrast-enhanced (DCE) magnetic resonance (MR) imaging and automatic whole brain segmentation.

Materials and Methods

Forty-two consecutive mTBI patients with PCS who had undergone post-traumatic MR imaging, including DCE MR imaging, between October 2016 and April 2018, and 29 controls with DCE MR imaging were included in this retrospective study. After performing three-dimensional T1-based brain segmentation with FreeSurfer software (Laboratory for Computational Neuroimaging), the mean K^trans and v_p from DCE MR imaging (derived using the Patlak model and extended Tofts and Kermode model) were analyzed in the bilateral cerebral/cerebellar cortex, bilateral cerebral/cerebellar white matter (WM), and brainstem. K^trans values of the mTBI patients and controls were calculated using both models to identify the model that better reflected the increased permeability owing to mTBI (tendency toward higher K^trans values in mTBI patients than in controls). The Mann-Whitney U test and Spearman rank correlation test were performed to compare the mean K^trans and v_p between the two groups and correlate K^trans and v_p with neuropsychological tests for mTBI patients.

Results

Increased permeability owing to mTBI was observed in the Patlak model but not in the extended Tofts and Kermode model. In the Patlak model, the mean K^trans in the bilateral cerebral cortex was significantly higher in mTBI patients than in controls (p = 0.042). The mean v_p values in the bilateral cerebellar WM and brainstem were significantly lower in mTBI patients than in controls (p = 0.009 and p = 0.011, respectively). The mean K^trans of the bilateral cerebral cortex was significantly higher in patients with atypical performance in the auditory continuous performance test (commission errors) than in average or good performers (p = 0.041).

Conclusion

BBB disruption, as reflected by the increased K^trans and decreased v_p values from the Patlak model, was observed throughout the bilateral cerebral cortex, bilateral cerebellar WM, and brainstem in mTBI patients with PCS.

Cathepsin B in neurodegeneration of Alzheimer's disease, traumatic brain injury, and related brain disorders

Investigations of Alzheimer's disease (AD), traumatic brain injury (TBI), and related brain disorders have provided extensive evidence for involvement of cathepsin B, a lysosomal cysteine protease, in mediating the behavioral deficits and neuropathology of these neurodegenerative diseases. This review integrates findings of cathepsin B regulation in clinical biomarker studies, animal model genetic and inhibitor evaluations, structural studies, and lysosomal cell biological mechanisms in AD, TBI, and related brain disorders. The results together indicate the role of cathepsin B in the behavioral deficits and neuropathology of these disorders. Lysosomal leakage occurs in AD and TBI, and related neurodegeneration, which leads to the hypothesis that cathepsin B is redistributed from the lysosome to the cytosol where it initiates cell death and inflammation processes associated with neurodegeneration. These results together implicate cathepsin B as a major contributor to these neuropathological changes and behavioral deficits. These findings support the investigation of cathepsin B as a potential drug target for therapeutic discovery and treatment of AD, TBI, and TBI-related brain disorders.

Histological and Behavioral Evaluation after Traumatic Brain Injury in Mice: A Ten Months Follow-Up Study

Traumatic brain injury (TBI) is a chronic pathology, inducing long-term deficits that remain understudied in pre-clinical studies. In this context, exploration, anxiety-like behavior, cognitive flexibility, and motor coordination were assessed until 5 and 10 months after an experimental TBI in the adult mouse, using two cohorts. In order to differentiate age, surgery, and remote gray and white matter lesions, three groups (unoperated, sham-operated, and TBI) were studied. TBI induced delayed motor coordination deficits at the pole test, 4.5 months after injury, that could be explained by gray and white matter damages in ipsilateral nigrostriatal structures (striatum, internal capsule) that were spreading to new structures between cohorts, at 5 versus 10 months after the injury. Further, TBI induced an enhanced exploratory behavior during stressful situations (active phase during actimetry test, object exploration in an open field), risk-taking behaviors in the elevated plus maze 5 months after injury, and a cognitive inflexibility in the Barnes maze that persisted until 9 months after the injury. These behavioral modifications could be related to the white and gray matter lesions observed in ipsi- and contralateral limbic structures (amygdala, hilus/cornu ammonis 4, hypothalamus, external capsule, corpus callosum, and cingular cortex) that were spreading to new structures between cohorts, at 5 months versus 10 months after the injury. The present study corroborates clinical findings on TBI and provides a relevant rodent chronic model which could help in validating pharmacological strategies against the chronic consequences of TBI.

Magnetic Resonance Imaging as a Biomarker in Rodent Peripheral Nerve Injury Models Reveals an Age-Related Impairment of Nerve Regeneration

Assessment of myelin integrity in peripheral nerve injuries and pathologies has largely been limited to post-mortem analysis owing to the difficulty in obtaining biopsies without affecting nerve function. This is further encumbered  by the small size of the tissue and its location. Therefore, the development of robust, non-invasive methods is highly attractive. In this study, we used magnetic resonance imaging (MRI) techniques, including magnetization transfer ratio (MTR), to longitudinally and non-invasively characterize both the sciatic nerve crush and lysolecithin (LCP) demyelination models of peripheral nerve injury in rodents. Electrophysiological, gene expression and histological assessments complemented the extensive MRI analyses in young and aged animals. In the nerve crush model, MTR analysis indicated a slower recovery in regions distal to the site of injury in aged animals, as well as incomplete recovery at six weeks post-crush when analyzing across the entire nerve surface. Similar regional impairments were also found in the LCP demyelination model. This research underlines the power of MTR for the study of peripheral nerve injury in small tissues such as the sciatic nerve of rodents and contributes new knowledge to the effect of aging on recovery after injury. A particular advantage of the approach is the translational potential to human neuropathies.

Traumatic brain injury: neuropathological, neurocognitive and neurobehavioral sequelae

Traumatic brain injury (TBI) causes substantial neurological disabilities and mental distress. Annual TBI incidence is in magnitude of millions, making it a global health challenge. Categorization of TBI into severe, moderate and mild by scores on the Glasgow coma scale (GCS) is based on clinical grounds and standard brain imaging (CT). Recent research focused on repeated mild TBI (sport and non-sport concussions) suggests that a considerable number of patients have long-term disabling neurocognitive and neurobehavioral sequelae. These relate to subtle neuronal injury (diffuse axonal injury) visible only by using advanced neuroimaging distinguishing microstructural tissue damage. With advanced MRI protocols better characterization of TBI is achievable. Diffusion tensor imaging (DTI) visualizes white matter pathology, susceptibility weight imaging (SWI) detects microscopic bleeding while functional magnetic resonance imaging (fMRI) provides closer understanding of cognitive disorders etc. However, advanced imaging is still not integrated in the clinical care of patients with TBI. Patients with chronic TBI may experience many somatic disorders, cognitive disturbances and mental complaints. The underlying pathophysiological mechanisms occurring in TBI are complex, brain injuries are highly heterogeneous and include neuroendocrine dysfunctions. Post-traumatic neuroendocrine dysfunctions received attention since the year 2000. Occurrence of TBI-related hypopituitarism does not correlate to severity of the GCS scores. Complete or partial hypopituitarism (isolated growth hormone (GH) deficiency as most frequent) may occur after mild TBI equally as after moderate-to-severe TBI. Many symptoms of hypopituitarism overlap with symptoms occurring in patients with chronic TBI, i.e. they have lower scores on neuropsychological examinations (cognitive disability) and have more symptoms of mental distress (depression and fatigue). The great challenges for the endocrinologist are: (1) detection of hypopituitarism in patients with TBI prospectively (in the acute phase and months to years after TBI), (2) assessment of the extent of cognitive impairment at baseline, and (3) monitoring of treatment effects (alteration of cognitive functioning and mental distress with hormone replacement therapy). Only few studies recently suggest that with growth hormone (rhGH) replacement in patients with chronic TBI and with abnormal GH secretion, cognitive performance may not change while symptoms related to depression and fatigue improve. Stagnation in post-TBI rehabilitation progress is recommended as a signal for clinical suspicion of neuroendocrine dysfunction. This remains a challenging area for more research.

Relationship between white matter integrity and post-traumatic cognitive deficits: a systematic review and meta-analysis

OBJECTIVE

To investigate relationships between cognitive domains and white matter changes in different regions in patients with cognitive deficits after traumatic brain injury (TBI).

METHODS

Databases including PubMed, Embase, Web of Science and CENTRAL were searched for studies published before 5 August 2017. Correlation coefficients between cognition and white matter integrity, measured by diffusion metrics, including fractional anisotropy (FA), were pooled from 49 studies including 1405 patients. The influence of demographic factors was assessed by meta-regression analysis.

RESULTS

Significant pooled FA-executive correlations (p<0.001) were found across various regions, including the corpus callosum (CC) (r=0.42, 95% CI 0.30 to 0.54), superior longitudinal fasciculus (r=0.50, 95% CI 0.41 to 0.59) and internal capsule (IC) (r=0.49, 95% CI 0.37 to 0.61). The fornix (r=0.62, 95% CI 0.45 to 0.78) and cingulum (r=0.57, 95% CI 0.34 to 0.81) particularly correlated with memory (p<0.001). The CC and IC also showed significant relationships with attention and processing speed (p<0.001). Demographic factors had no influence overall, except that studies with a greater proportion of males had stronger correlations between memory and white matter (p<0.05).

CONCLUSIONS

FA is the most sensitive metric for detecting post-TBI cognitive decline across various domains. Representative white matter regions, such as the CC and IC, perform better than whole-brain white matter for reflecting a wide range of cognitive domains, including memory, attention and executive functions. Moreover, the fornix and cingulum particularly reflect memory function. They yield insights into particular imaging indicators that have neuropsychological value.

Impacts of cognitive impairment for different levels and causes of traumatic brain injury, and education status in TBI patients

Traumatic brain injury (TBI) is one of main causes of death and disability among many young and old populations in different countries.

OBJECTIVE

The aim of this study were to consider and predict the cognitive impairments according to different levels and causes of TBI, and education status.

METHODS

The study was performed using the Mini-Mental State Examination (MMSE) to estimate cognitive impairment in patients at a trauma center in Zahedan city. Individuals were considered eligible if 18 years of age or older. This investigation assessed a subset of patients from a 6-month pilot study.

RESULTS

The study participants comprised 66% males and 34% females. Patient mean age was 32.5 years and SD was 12.924 years. One-way analysis of variance between groups indicated cognitive impairment related to different levels and causes of TBI, and education status in patients. There was a significant difference in the dimensions of cognitive impairments for different levels and causes of TBI, and education status. A regression test showed that levels of traumatic brain injury (b=.615, p=.001) and education status (b=.426, p=.001) predicted cognitive impairment.

CONCLUSION

Different levels of TBI and education status were useful for predicting cognitive impairment in patients. Severe TBI and no education were associated with worse cognitive performance and higher disability. These data are essential in terms of helping patients understand their needs. Therefore, the factors identified can help plan effective rehabilitation programs.

Diffusion Kurtosis Imaging Characterizes Brain Microstructural Changes Associated with Cognitive Impairment in a Rat Model of Chronic Traumatic Brain Injury

This study aims to investigate the value of diffusion kurtosis imaging (DKI) in assessing microstructural changes associated with cognitive impairment in chronic traumatic brain injury (TBI). At 7 months, six TBI rats and six control rats underwent Morris water maze (MWM) tests, followed by DKI examinations. DKI parameters were measured in bilateral cortex, hippocampus, and callosum. Brain immunohistochemistry (IHC) analysis of neuron [neuron-specific nuclear protein (NeuN)], astroglia [glial fibrillary acidic protein (GFAP)], microglia [ionized calcium binding adaptor molecule 1 (Iba-1)], and myelin [myelin basic protein (MBP)] was performed in the same area as DKI parameter. The DKI parameters, IHC results, and MWM results were compared between TBI and control groups. Correlation analysis was performed to analyze the relationship between DKI parameters and IHC and MWM results. TBI group had worse performance in MWM test. DKI showed higher mean diffusion (MD) in all ipsilateral regions of interest (ROIs), and lower mean kurtosis (MK) in ipsilateral cortex and callosum in TBI group (P < 0.05). TBI group also showed lower IHC staining of NeuN, and higher staining of Iba-1 and MBP in all ipsilateral ROIs (P < 0.05). Further correlational study showed a positive relationship between MK and NeuN, MD and MBP in ipsilateral cortex, and a negative relationship between MK and Iba-1, MBP in ipsilateral cortex and hippocampus (P < 0.05). The MK in ipsilateral cortex and hippocampus were also correlated with MWM test results (P < 0.05). Our study suggests that DKI could be used to assess the microstructural changes associated with cognitive impairment in chronic TBI.

Longitudinal Microstructural Changes in Traumatic Brain Injury in Rats: A Diffusional Kurtosis Imaging, Histology, and Behavior Study

BACKGROUND AND PURPOSE

Traumatic brain injury is a major public health problem worldwide. Accurately evaluating the brain microstructural changes in traumatic brain injury is crucial for the treatment and prognosis assessment. This study aimed to assess the longitudinal brain microstructural changes in traumatic brain injury in the rat using diffusional kurtosis imaging.

MATERIALS AND METHODS

Diffusional kurtosis imaging was performed in a group of 5 rats at preinjury and 3, 14, and 28 days after traumatic brain injury. The diffusional kurtosis imaging parameters were measured in the bilateral cortex, hippocampus, and corpus callosum. Another 4 groups of 5 rats were used in brain immunohistochemistry analysis of neuron (neuron-specific nuclear protein [NeuN]), astroglia (glial fibrillary acidic protein [GFAP]), microglia (ionized calcium binding adaptor molecule 1 [Iba-1]), and myelin (myelin basic protein [MBP]) in the same area as the diffusional kurtosis imaging parameter measurements. Furthermore, 2 groups of 6 rats underwent a Morris water maze test at 28 days after traumatic brain injury. The diffusional kurtosis imaging parameters, immunohistochemistry results, and Morris water maze test results were compared longitudinally or between traumatic brain injury and control groups.

RESULTS

Compared with baseline, traumatic brain injury in the rat showed higher mean kurtosis and mean diffusivity values in the ipsilateral perilesional cortex and hippocampus and lower fractional anisotropy values in the corpus callosum (P < .05). The traumatic brain injury group showed higher staining of GFAP and Iba-1 and lower immunohistochemistry staining of NeuN and MBP in all ipsilateral ROIs (P < .05). There was no significant difference in the contralateral ROIs in diffusional kurtosis imaging parameters or immunohistochemistry results. The Morris water maze test revealed lower platform crossing times in the probe test (P < .05).

CONCLUSIONS

Our study indicated that there were longitudinal changes in diffusional kurtosis imaging parameters, accompanied by multiple pathologic changes at different time points following traumatic brain injury, and that mean kurtosis is more sensitive to detect microstructural changes, especially in gray matter, than mean diffusivity and fractional anisotropy.

The Microtubule-Modulating Drug Epothilone D Alters Dendritic Spine Morphology in a Mouse Model of Mild Traumatic Brain Injury

Microtubule dynamics underpin a plethora of roles involved in the intricate development, structure, function, and maintenance of the central nervous system. Within the injured brain, microtubules are vulnerable to misalignment and dissolution in neurons and have been implicated in injury-induced glial responses and adaptive neuroplasticity in the aftermath of injury. Unfortunately, there is a current lack of therapeutic options for treating traumatic brain injury (TBI). Thus, using a clinically relevant model of mild TBI, lateral fluid percussion injury (FPI) in adult male Thy1-YFPH mice, we investigated the potential therapeutic effects of the brain-penetrant microtubule-stabilizing agent, epothilone D. At 7 days following a single mild lateral FPI the ipsilateral hemisphere was characterized by mild astroglial activation and a stereotypical and widespread pattern of axonal damage in the internal and external capsule white matter tracts. These alterations occurred in the absence of other overt signs of trauma: there were no alterations in cortical thickness or in the number of cortical projection neurons, axons or dendrites expressing YFP. Interestingly, a single low dose of epothilone D administered immediately following FPI (and sham-operation) caused significant alterations in the dendritic spines of layer 5 cortical projection neurons, while the astroglial response and axonal pathology were unaffected. Specifically, spine length was significantly decreased, whereas the density of mushroom spines was significantly increased following epothilone D treatment. Together, these findings have implications for the use of microtubule stabilizing agents in manipulating injury-induced synaptic plasticity and indicate that further study into the viability of microtubule stabilization as a therapeutic strategy in combating TBI is warranted.

Epileptiform activity in traumatic brain injury predicts post-traumatic epilepsy

We hypothesize that epileptiform abnormalities (EAs) in the electroencephalogram (EEG) during the acute period following traumatic brain injury (TBI) independently predict first-year post-traumatic epilepsy (PTE1 ). We analyze PTE1 risk factors in two cohorts matched for TBI severity and age (n = 50). EAs independently predict risk for PTE1 (odds ratio [OR], 3.16 [0.99, 11.68]); subdural hematoma is another independent risk factor (OR, 4.13 [1.18, 39.33]). Differences in EA rates are apparent within 5 days following TBI. Our results suggest that increased EA prevalence identifies patients at increased risk for PTE1 , and that EAs acutely post-TBI can identify patients most likely to benefit from antiepileptogenesis drug trials. Ann Neurol 2018;83:858-862.

Self-reported traumatic brain injury and in vivo measure of AD-vulnerable cortical thickness and AD-related biomarkers in the ADNI cohort

In this study, we aimed to investigate whether self-reported mild traumatic brain injury (mTBI) was associated with decreased AD-vulnerable cortical thickness, and to assess the relationship between AD-vulnerable cortical thickness and AD-related biomarker in the Alzheimer's Disease Neuroimaging Initiative subjects. We identified 45 self-reported mTBI subjects, who had structural MRI, 18F-AV45 PET, and cerebrospinal fluid (CSF) data. Of them, eight subjects were normal; ten were preclinical AD; seventeen were MCI due to AD; ten were AD. Additional demographics-controlled 45 subjects were included. Cortical thickness of eight AD-vulnerable regions, mean AD-vulnerable cortical thickness, 18F-AV45 PET mean amyloid SUVR, CSF Aβ42, CSF total tau (T-tau), and CSF phosphorylated tau (P-tau) were compared between mTBI and non-TBI groups. Correlational analysis was done to investigate the relationship between mean AD-vulnerable cortical thickness and mean amyloid SUVR, CSF Aβ42, CSF T-Tau, CSF P-Tau. Our study revealed that preclinical AD subjects with self-reported mTBI had smaller cortical thickness in mean and three AD-vulnerable cortical regions than non-TBI subjects (P<0.05). The mean AD-vulnerable cortical thickness was correlated with CSF T-tau (r=-0.81, P=0.001). There was no statistical difference in the comparison of normal, MCI due to AD, and AD groups. Our study indicated that among individuals with preclinical AD, but not normal, MCI due to AD and AD subjects, self-reported mTBI was associated with more decreased AD-vulnerable cortical thickness which was related to CSF tau pathology, suggesting the possible early involvement of tau pathology in the decreased AD-vulnerable cortical thickness of self-reported TBI subjects.

Vascular impairment as a pathological mechanism underlying long-lasting cognitive dysfunction after pediatric traumatic brain injury

Traumatic brain injury (TBI) is the leading cause of death and disability in children. Indeed, the acute mechanical injury often evolves to a chronic brain disorder with long-term cognitive, emotional and social dysfunction even in the case of mild TBI. Contrary to the commonly held idea that children show better recovery from injuries than adults, pediatric TBI patients actually have worse outcome than adults for the same injury severity. Acute trauma to the young brain likely interferes with the fine-tuned developmental processes and may give rise to long-lasting consequences on brain's function. This review will focus on cerebrovascular dysfunction as an important early event that may lead to long-term phenotypic changes in the brain after pediatric TBI. These, in turn may be associated with accelerated brain aging and cognitive dysfunction. Finally, since no effective treatments are currently available, understanding the unique pathophysiological mechanisms of pediatric TBI is crucial for the development of new therapeutic options.