Altered connectivity of default mode and executive control networks among female patients with persistent post-concussion symptoms

Association of player position and functional connectivity alterations in collegiate American football players: an fMRI study

Introduction

Resting state-fMRI, provides a sensitive method for detecting changes in brain functional integrity, both with respect to regional oxygenated blood flow and whole network connectivity. The primary goal of this report was to examine alterations in functional connectivity in collegiate American football players after a season of repetitive head impact exposure.

Methods

Collegiate football players completed a rs-fMRI at pre-season and 1 week into post-season. A seed-based functional connectivity method, isolating the posterior cingulate cortex (PCC), was utilized to create individual functional connectivity maps. During group analysis, first, voxel-wise paired sample t-tests identified significant changes in connectivity from pre- to post-season, by player, and previous concussion history. Second, 10 DMN ROIs were constructed by overlaying an anatomical map over regions of positive correlation from one-sample t-tests of pre-season and post-season. These ROIs, plus the LpCun, were included in linear mix-effect modeling, with position or concussion history as covariates.

Results

66 players were included (mean age 20.6 years; 100% male; 34 (51.5%) non-speed position players). The 10 DMN ROIs showed no alterations from pre-season to post-season. By concussion history, the right temporal ROI demonstrated a significant effect on baseline functional connectivity (p = 0.03). Speed players, but not non-speed players, demonstrated a significant decrease in functional connectivity in the precuneus from pre- to post-season (p < 0.001).

Discussion

There are region-specific differences functional connectivity related to both position and concussion history in American collegiate football players. Player position affected functional connectivity across a season of football. Position-specific differences in head impact exposure rate and magnitude plays a crucial role in functional connectivity alterations.

Changes in Resting-State Functional Connectivity and Cognitive-Affective Symptoms in Patients With Post-Concussion Syndrome Treated With N-Acetyl Cysteine

OBJECTIVE

Concussion accounts for more than 80% of people experiencing traumatic brain injury. Acute concussion is associated with characteristic cognitive and functional deficits that may persist for weeks to months. A subgroup of these patients (from 10% to 50%) have persistent symptoms referred to as chronic post-concussion syndrome (PCS). There are limited treatment options for these patients and the pathophysiology is poorly understood, though oxidative stress is thought to be a contributing factor. The purpose of this study was to evaluate whether an antioxidant, N-acetylcysteine (NAC), might be beneficial in patients with PCS.

SETTING

Outpatient medicine center.

PARTICIPANTS

Fifty patients with chronic PCS for at least 3 months post injury.

DESIGN

The patients with PCS were enrolled in this randomized unblinded clinical trial to receive the antioxidant NAC as a combination of daily oral and weekly intravenous infusions, or assigned to a waitlist control group where they would continue to receive standard of care.

MAIN MEASURES

Resting-state functional connectivity (FC) magnetic resonance imaging (rsFC-MRI) was performed pre and post either NAC or the waitlist period along with cognitive, emotional, and sensory symptom assessments.

RESULTS

The results demonstrated significant (P < .05) improvements in symptoms as determined by the Rivermead Post-Concussion Symptoms Questionnaire, Spielberger State-Trait Anxiety Inventory, and Profile of Mood Scale in the PCS group receiving NAC as compared to patients receiving ongoing standard care. Importantly, there were significant (P< .01) changes in FC in the NAC group, particularly in networks such as the default mode network, salience network, and executive control network. These changes in FC also correlated with improvements in symptoms.

CONCLUSIONS

In patients with chronic PCS, NAC treatment was associated with significant changes in resting state FC and improvement in a variety of symptoms, particularly cognitive and affective symptoms.

Concussion history and virtual reality metrics predict core or lower extremity injury occurrence among high school athletes

Introduction

A history of concussion is recognized as a risk factor for musculoskeletal injury, which is likely associated with physiological effects that warrant better understanding. This study aimed to assess the potential of measurements obtained from an immersive virtual reality (VR) test to identify a subtle perceptual-motor impairment that may be prospectively associated with the occurrence of a core or lower extremity sprain or strain.

Methods

A cohort of 68 high school athletes (41 female soccer players and 27 male football players) provided survey responses and completed an immersive VR test several days prior to the initiation of preseason practice sessions. Measurements of eye, neck, arm, and whole-body displacements were obtained during 40 successive lunging/reaching responses to visual stimuli moving horizontally across the VR headset display. Injury occurrences were electronically documented from the initial preseason practice session to the final game of the season.

Results

A statistically significant and intrinsically credible two-factor prediction model for core or lower extremity injury occurrence included an interaction between female sex and a self-reported history of two or more concussions, along with slow response time (RT) for arm reach (OR = 4.67; 95% CI, 1.51-14.43). Follow-up analyses identified sex-specific cut points for arm reach RT associated with elevated injury risk, which were ≥1.385 s for females and ≥1.257 s for males.

Discussion

High school female soccer players who have sustained more than one concussion appear to be highly vulnerable to core or lower extremity sprain or strain, with the risk of injury compounded by a slow arm reach RT. Male football players as a group demonstrated significantly faster arm reach RT than that of female soccer players, but slow perceptual-motor RT for arm reach was also identified as a potentially important injury risk factor for male players. Immersive VR appears to provide precise measurements of behavioral performance characteristics that depend on brain processing efficiency. Given that the speed, accuracy, and consistency of perceptual-motor responses may be modifiable, future research should explore the potential benefits of VR training for reducing the risk of sport-related injuries.

Sleep loss, caffeine, sleep aids and sedation modify brain abnormalities of mild traumatic brain injury

Little evidence exists about how mild traumatic brain injury (mTBI) is affected by commonly encountered exposures of sleep loss, sleep aids, and caffeine that might be potential therapeutic opportunities. In addition, while propofol sedation is administered in severe TBI, its potential utility in mild TBI is unclear. Each of these exposures is known to have pronounced effects on cerebral metabolism and blood flow and neurochemistry. We hypothesized that they each interact with cerebral metabolic dynamics post-injury and change the subclinical characteristics of mTBI. MTBI in rats was produced by head rotational acceleration injury that mimics the biomechanics of human mTBI. Three mTBIs spaced 48 h apart were used to increase the likelihood that vulnerabilities induced by repeated mTBI would be manifested without clinically relevant structural damage. After the third mTBI, rats were immediately sleep deprived or administered caffeine or suvorexant (an orexin antagonist and sleep aid) for the next 24 h or administered propofol for 5 h. Resting state functional magnetic resonance imaging (rs-fMRI) and diffusion tensor imaging (DTI) were performed 24 h after the third mTBI and again after 30 days to determine changes to the brain mTBI phenotype. Multi-modal analyses on brain regions of interest included measures of functional connectivity and regional homogeneity from rs-fMRI, and mean diffusivity (MD) and fractional anisotropy (FA) from DTI. Each intervention changed the mTBI profile of subclinical effects that presumably underlie healing, compensation, damage, and plasticity. Sleep loss during the acute post-injury period resulted in dramatic changes to functional connectivity. Caffeine, propofol sedation and suvorexant were especially noteworthy for differential effects on microstructure in gray and white matter regions after mTBI. The present results indicate that commonplace exposures and short-term sedation alter the subclinical manifestations of repeated mTBI and therefore likely play roles in symptomatology and vulnerability to damage by repeated mTBI.

Test-Retest Reliability of Immersive Virtual Reality Measures of Perceptual-Motor Performance

The duration, accuracy, and consistency of responses to various types of stimuli are widely accepted as indirect indicators of the efficiency of brain information processing, but current clinical tests appear to lack sufficient sensitivity to detect subtle impairments. Immersive virtual reality (VR) offers a new means to acquire measures of perceptual-motor responses to moving visual stimuli that require rapid conflict resolution, but their test-retest reliability has not yet been demonstrated. Repeated measures. We analyzed data from 19 healthy young adults who performed a 40-trial VR test on three consecutive days. We focused on response time (RT) and perceptual latency (PL) for eye, neck, arm, and whole-body step displacements involved in executing a reaching/lunging movement in a right or left direction toward a peripherally located virtual target. Measures of RT and PL included a 40-trial mean, an intra-individual variability (IIV) value, and a rate correct score (RCS) that incorporated both response duration and accuracy. Most mean and IIV values for PL and RT demonstrated a positive distributional skew that was substantially reduced by natural logarithm transformation. While a learning effect was evident between sessions 1 and 2 for 7 of 8 mean PL and RT measures, 3-session intraclass correlation coefficient (ICC) values were moderate to excellent for 15 of 16 transformed PL and RT measures (range: .618 to .922). The composite RCS metric did not require transformation for either PL or RT, whose respective 3-session ICC values were .877 and .851. This moderate to excellent test-retest reliability for various VR measures of perceptual-motor function, combined with evidence of their validity from both past and future research, suggest that these measures can advance clinical detection of impaired brain processing and longitudinal assessments of potentially modifiable performance deficiencies.

A review of brain regions and associated post-concussion symptoms

The human brain is an exceptionally complex organ that is comprised of billions of neurons. Therefore, when a traumatic event such as a concussion occurs, somatic, cognitive, behavioral, and sleep impairments are the common outcome. Each concussion is unique in the sense that the magnitude of biomechanical forces and the direction, rotation, and source of those forces are different for each concussive event. This helps to explain the unpredictable nature of post-concussion symptoms that can arise and resolve. The purpose of this narrative review is to connect the anatomical location, healthy function, and associated post-concussion symptoms of some major cerebral gray and white matter brain regions and the cerebellum. As a non-exhaustive description of post-concussion symptoms nor comprehensive inclusion of all brain regions, we have aimed to amalgamate the research performed for specific brain regions into a single article to clarify and enhance clinical and research concussion assessment. The current status of concussion diagnosis is highly subjective and primarily based on self-report of symptoms, so this review may be able to provide a connection between brain anatomy and the clinical presentation of concussions to enhance medical imaging assessments. By explaining anatomical relevance in terms of clinical concussion symptom presentation, an increased understanding of concussions may also be achieved to improve concussion recognition and diagnosis.