Persistent Visual and Vestibular Impairments for Postural Control Following Concussion: A Cross-Sectional Study in University Students.

OBJECTIVE: To examine how concussion may impair sensory processing for control of upright stance. METHODS: Participants were recruited from a single university into 3 groups: 13 participants (8 women, 21 ± 3 years) between 2 weeks and 6 months post-injury who initiated a return-to-play progression (under physician management) by the time of testing (recent concussion group), 12 participants (7 women, 21 ± 1 years) with a history of concussion (concussion history group, > 1 year post-injury), and 26 participants (8 women, 22 ± 3 years) with no concussion history (control group). We assessed sensory reweighting by simultaneously perturbing participants' visual, vestibular, and proprioceptive systems and computed center of mass gain relative to each modality. The visual stimulus was a sinusoidal translation of the visual scene at 0.2 Hz, the vestibular stimulus was ± 1 mA binaural monopolar galvanic vestibular stimulation (GVS) at 0.36 Hz, the proprioceptive stimulus was Achilles' tendon vibration at 0.28 Hz. RESULTS: The recent concussion (95% confidence interval 0.078-0.115, p = 0.001) and the concussion history (95% confidence interval 0.056-0.094, p = 0.038) groups had higher gains to the vestibular stimulus than the control group (95% confidence interval 0.040-0.066). The recent concussion (95% confidence interval 0.795-1.159, p = 0.002) and the concussion history (95% confidence interval 0.633-1.012, p = 0.018) groups had higher gains to the visual stimulus than the control group (95% confidence interval 0.494-0.752). There were no group differences in gains to the proprioceptive stimulus or in sensory reweighting. CONCLUSION: Following concussion, participants responded more strongly to visual and vestibular stimuli during upright stance, suggesting they may have abnormal dependence on visual and vestibular feedback. These findings may indicate an area for targeted rehabilitation interventions.

Effects of purposeful soccer heading on circulating small extracellular vesicle concentration and cargo.

BACKGROUND: Considering the potential cumulative effects of repetitive head impact (HI) exposure, we need sensitive biomarkers to track short- and long-term effects. Circulating small extracellular vesicles (sEVs) (<200 nm) traffic biological molecules throughout the body and may have diagnostic value as biomarkers for disease. The purpose of this study was to identify the microRNA (miRNA) profile in circulating sEVs derived from human plasma following repetitive HI exposure. METHODS: Healthy adult (aged 18-35 years) soccer players were randomly assigned to one of 3 groups: the HI group performed 10 standing headers, the leg impact group performed 10 soccer ball trapping maneuvers over 10 min, and the control group did not participate in any soccer drills. Plasma was collected before testing and 24 h afterward, and sEVs were isolated and characterized via nanoparticle tracking analysis. Next-generation sequencing was utilized to identify candidate miRNAs isolated from sEVs, and candidate microRNAs were analyzed via quantitative polymerase chain reaction. In silico target prediction was performed using TargetScan (Version 7.0; targetscan.org) and miRWalk (http://mirwalk.umm.uni-heidelberg.de/) programs, and target validation was performed using luciferase reporter vectors with a miR-7844-5p mimic in human embryonic kidney (HEK) 293T/17 cells. RESULTS: Plasma sEV concentration and size were not affected across time and group following repetitive HI exposure. After 24 h, the HI read count from next-generation sequencing showed a 4-fold or greater increase in miR-92b-5p, miR-423-5p, and miR-24-3p and a 3-fold or greater decrease in miR-7844-5p, miR-144-5p, miR-221-5p, and miR-22-3p. Analysis of quantitative polymerase chain reaction revealed that leg impact did not alter the candidate miRNA levels. To our knowledge, miR-7844-5p is a previously unknown miRNA. We identified 8 miR-7844-5p mRNA targets: protein phosphatase 1 regulatory inhibitor subunit 1B (PPP1R1B), LIM and senescent cell antigen-like domains 1 (LIMS1), autophagy-related 12 (ATG12), microtubule-associated protein 1 light chain 3 beta (MAP1LC3B), integrin subunit alpha-1 (ITGA1), mitogen-activated protein kinase 1 (MAPK1), glycogen synthase kinase 3ß (GSK3ß), and mitogen-activated protein kinase 8 (MAPK8). CONCLUSION: Collectively, these data indicate repetitive HI exposure alters plasma sEV miRNA content, but not sEV size or number. Furthermore, for the first time we demonstrate that previously unknown miR-7844-5p targets mRNAs known to be involved in mitochondrial apoptosis, autophagy regulation, mood disorders, and neurodegenerative disease.

Virtual reality in concussion management: from lab to clinic.

The use of virtual reality (VR) technology continues to grow in the areas of clinical assessment and rehabilitation. Both researchers and health-care providers are exploring ways to incorporate VR in clinical practice as an emerging technology. VR postural control and neuropsychological testing represent a promising next step in sport-related concussion (SRC) management. This article reviews the current literature on VR applications for SRC assessment. RELEVANCE FOR PATIENTS: VR-based postural control assessments suggest that visual motion is destabilizing following SRC, perhaps indicating persistent perceptual-motion disintegration when clinical postural control tests suggest complete recovery. VR can also provide functional neuropsychological assessments using real-life scenarios or virtual environments, which may be more sensitive than traditional pencil-and-paper or computerized neuropsychological assessments.

Sensory Reweighting for Upright Stance in Soccer Players: A Comparison of High and Low Exposure to Soccer Heading.

The purpose of this study was to compare sensory reweighting for upright stance between soccer players who report higher soccer heading exposure to those who report lower soccer heading exposure. Thirty participants completed a self-reported questionnaire to estimate the number of soccer headers experienced over the previous year and were divided into "low exposure" and "high exposure" groups based on their responses. Sensory reweighting for upright stance was assessed by simultaneously perturbing visual, vestibular, and proprioceptive systems. The visual stimulus was a sinusoidal translation of the visual scene at 0.2 Hz, the vestibular stimulus was ±1mA binaural monopolar galvanic vestibular stimulation (GVS) at 0.36 Hz, and the proprioceptive stimulus was Achilles tendon vibration at 0.28 Hz. The visual stimulus was presented at two amplitudes (0.2 m, 0.8 m). Center of mass (COM) gain/phase to each modality, total power, 95% area and velocity were compared between low exposure (N = 15, six males, 21.5 ± 1.9 years, 27.7 ± 31.6 headers) and high exposure groups (N = 15, 10 males, 22.1 ± 3.5years, 734.9 ± 877.7 headers). Without vibration, COM 95% area (F = 5.861, p = 0.022*, partial η2 = 0.173), velocity (F = 14.198, p = 0.001, partial η2 = 0.336), and total power (F = 13.491, p = 0.001, partial η2 = 0.325) for the "high exposure" group were higher than for the "low exposure" group, and postural sway lagged the vestibular stimulus in the "high exposure" group rather than leading it as in the "low exposure" group (F = 4.765, p = 0.038, partial η2 = 0.145). There were no differences in sensory reweighting and no differences in COM gain/phase between groups. These findings lend empirical evidence to a detrimental effect of soccer heading exposure on balance control during upright stance.

Age of First Exposure to Soccer Heading and Sensory Reweighting for Upright Stance.

US Soccer eliminated soccer heading for youth players ages 10 years and younger and limited soccer heading for children ages 11-13 years. Limited empirical evidence associates soccer heading during early adolescence with medium-to-long-term behavioral deficits. The purpose of this study was to compare sensory reweighting for upright stance between college-aged soccer players who began soccer heading ages 10 years and younger (AFE ≤ 10) and those who began soccer heading after age 10 (AFE > 10). Thirty soccer players self-reported age of first exposure (AFE) to soccer heading. Sensory reweighting was compared between AFE ≤ 10 and AFE > 10. To evaluate sensory reweighting, we simultaneously perturbed upright stance with visual, vestibular, and proprioceptive stimulation. The visual stimulus was presented at two different amplitudes to measure the change in gain to vision, an intra-modal effect; and change in gain to galvanic vestibular stimulus (GVS) and vibration, both inter-modal effects. There were no differences in gain to vision (p=0.857, η2=0.001), GVS (p=0.971, η2=0.000), or vibration (p=0.974, η2=0.000) between groups. There were no differences in sensory reweighting for upright stance between AFE ≤ 10 and AFE > 10, suggesting that soccer heading during early adolescence is not associated with balance deficits in college-aged soccer players, notwithstanding potential deficits in other markers of neurological function.