Intimate Partner Violence-Related Brain Injury: Unmasking and Addressing the Gaps

Intimate partner violence (IPV) is a significant, global public health concern. Women, individuals with historically underrepresented identities, and disabilities are at high risk for IPV and tend to experience severe injuries. There has been growing concern about the risk of exposure to IPV-related head trauma, resulting in IPV-related brain injury (IPV-BI), and its health consequences. Past work suggests that a significant proportion of women exposed to IPV experience IPV-BI, likely representing a distinct phenotype compared with BI of other etiologies. An IPV-BI often co-occurs with psychological trauma and mental health complaints, leading to unique issues related to identifying, prognosticating, and managing IPV-BI outcomes. The goal of this review is to identify important gaps in research and clinical practice in IPV-BI and suggest potential solutions to address them. We summarize IPV research in five key priority areas: (1) unique considerations for IPV-BI study design; (2) understanding non-fatal strangulation as a form of BI; (3) identifying objective biomarkers of IPV-BI; (4) consideration of the chronicity, cumulative and late effects of IPV-BI; and (5) BI as a risk factor for IPV engagement. Our review concludes with a call to action to help investigators develop ecologically valid research studies addressing the identified clinical-research knowledge gaps and strategies to improve care in individuals exposed to IPV-BI. By reducing the current gaps and answering these calls to action, we will approach IPV-BI in a trauma-informed manner, ultimately improving outcomes and quality of life for those impacted by IPV-BI.

Neurovascular coupling is altered in women who have a history of brain injury from intimate partner violence: a preliminary study

Introduction

Intimate partner violence (IPV) is a global health crisis with 30% of women over the age of 15 experiencing at least one event in their lifetime. Brain injury (BI) due to head impacts and/or strangulation is a common but understudied part of this experience. Previous research has shown BI from other injury mechanisms can disrupt neurovascular coupling (NVC). To gain further insight into whether similar changes occur in this population, we assessed NVC responses in women with a history of IPV-BI.

Methods

NVC responses were measured for the middle and posterior cerebral arteries (MCA, PCA) using transcranial Doppler ultrasound while participants performed a complex visual search task. The lifetime history of previous exposure to IPV-BI was captured using the Brain Injury Severity Assessment (BISA) along with measures of post-traumatic stress disorder (PTSD), anxiety, depression, substance use, and demographic information. Initial analyses of NVC metrics were completed comparing participants who scored low vs. high on the BISA or did or did not experience non-fatal strangulation followed by a stepwise multiple regression to examine the impact of PTSD, anxiety, and depression on the relationship between the NVC metrics and IPV-BI.

Results

Baseline and peak cerebral blood velocity were higher and the percentage increase was lower in the PCA in the low compared to the high BISA group whereas no differences between the groups were apparent in the MCA. In addition, those participants who had been strangled had a lower initial slope and area under the curve in the PCA than those who had not experienced strangulation. Finally, the stepwise multiple regression demonstrated the percentage increase in the PCA was significantly related to the BISA score and both depression and anxiety significantly contributed to different components of the NVC response.

Conclusions

This preliminary study demonstrated that a lifetime history of IPV-BI leads to subtle but significant disruptions to NVC responses which are modulated by comorbid depression and anxiety. Future studies should examine cerebrovascular function at the acute and subacute stages after IPV episodes to shed additional light on this experience and its outcomes.

A computational pipeline towards large-scale and multiscale modeling of traumatic axonal injury

Contemporary biomechanical modeling of traumatic brain injury (TBI) focuses on either the global brain as an organ or a representative tiny section of a single axon. In addition, while it is common for a global brain model to employ real-world impacts as input, axonal injury models have largely been limited to inputs of either tension or compression with assumed peak strain and strain rate. These major gaps between global and microscale modeling preclude a systematic and mechanistic investigation of how tissue strain from impact leads to downstream axonal damage throughout the white matter. In this study, a unique subject-specific multimodality dataset from a male ice-hockey player sustaining a diagnosed concussion is used to establish an efficient and scalable computational pipeline. It is then employed to derive voxelized brain deformation, maximum principal strains and white matter fiber strains, and finally, to produce diverse fiber strain profiles of various shapes in temporal history necessary for the development and application of a deep learning axonal injury model in the future. The pipeline employs a structured, voxelized representation of brain deformation with adjustable spatial resolution independent of model mesh resolution. The method can be easily extended to other head impacts or individuals. The framework established in this work is critical for enabling large-scale (i.e., across the entire white matter region, head impacts, and individuals) and multiscale (i.e., from organ to cell length scales) modeling for the investigation of traumatic axonal injury (TAI) triggering mechanisms. Ultimately, these efforts could enhance the assessment of concussion risks and design of protective headgear. Therefore, this work contributes to improved strategies for concussion detection, mitigation, and prevention.

Characterizing Possible Acute Brain Injury in Women Experiencing Intimate Partner Violence: A Retrospective Chart Review

Survivors of intimate partner violence (IPV) often experience violent blows to the head, face, and neck and/or strangulation that result in brain injury (BI). Researchers reviewed the de-identified forensic nursing examination records of 205 women. More than 88% of women were subjected to multiple mechanisms of injury with in excess of 60% experiencing strangulation. About 31% disclosed various symptoms consistent with BI. Women experiencing strangulation were 2.24 times more likely to report BI-related symptoms compared to those who reported no strangulation. In conclusion, women experiencing IPV are prone to BI suggesting early screening and appropriate management are warranted.

The Concussion Awareness Training Tool for Women's Support Workers Improves Knowledge of Intimate Partner Violence-Caused Brain Injury

Women who experience physical intimate partner violence (IPV) are at high risk of suffering a brain injury (BI) due to head impacts and/or strangulation. Currently, most staff at women's shelters tend not to be aware of IPV-caused BIs. The objective of this study was to address this by developing a new online module within the Concussion Awareness Training Tool (cattonline.com) specifically focused on IPV-caused BI, and measuring its effectiveness in increasing BI awareness and knowledge among staff members at women's shelters. A mixed-methods approach was used which included (i) a survey to measure participant knowledge before and after completing the module; (ii) a 1-on-1 interview 6 months post-training to better understand participants' perceptions of what effect the training had on how they worked with women in their job; and (iii) an evaluation of the content of the module using behavior change techniques. About 81 participants recruited from staff at women's shelters completed the pre/post survey. The average BI knowledge score increased significantly from the pre-survey (M = 8.12/12, SD = 1.05) to the post-survey (M = 9.72/12, SD = 1.62), t(80) = 9.12, P < .001, d = 1.01). Analysis of the interviews with 9 participants highlighted 3 main themes arising from the module: knowledge, mindfulness, and advocacy. All participants felt their knowledge of IPV-caused BIs had increased and said they would recommend the training to their co-workers. Analysis of the module content revealed the most frequent behavior change techniques were related to instructions on how to perform screening and accommodation for IPV-caused BI. The results showed the module was effective in increasing knowledge of IPV-caused BIs amongst women's shelter staff as well as improving how they advocate for, and are mindful of, their clients with BIs. This online training may help improve the care women with IPV-caused BIs receive, and ultimately improve their quality of life.

Repetitive bout of controlled soccer heading does not alter heart rate variability metrics: A preliminary investigation

Objectives

There is elevated unease regarding how repetitive head impacts, such as those associated with soccer heading, contribute to alterations in brain function. This study examined the extent heart rate variability (HRV) and cardiac baroreceptor sensitivity (BRS) metrics are altered immediately following an acute bout of soccer heading.

Methods

Seven male elite soccer players (24.1 ± 1.5 years) completed 40 successful soccer headers in 20-min. The headers were performed under controlled circumstances using a soccer ball launcher located 25 meters away and using an initial ball velocity of 77.5 ± 3.7 km/h (heading condition). An accelerometer (xPatch) on the right mastoid process quantified linear/rotational head accelerations. Participants also completed sham (body contact) and control (non-contact) sessions. A three-lead ECG and finger photoplethysmography characterized short-term spontaneous HRV/cardiac BRS, before and after each condition. The SCAT3 indexed symptom scores pre-post exposures to all three conditions.

Results

During the heading condition, cumulative linear and rotational accelerations experienced were 1,574 ± 97.9 g and 313,761 ± 23,966 rad/s², respectively. Heart rate trended toward an increase from pre- to post-heading (p = 0.063), however HRV metrics in the time-domain (ps > 0.260) and frequency-domain (ps > 0.327) as well as cardiac BRS (ps > 0.144) were not significantly changed following all three conditions. Following the heading condition, SCAT3 symptom severity increased (p = 0.030) with a trend for symptom score augmentation (p = 0.078) compared to control and sham.

Conclusion

Whereas, symptoms as measured by the SCAT3 were induced following an acute bout of controlled soccer heading, these preliminary findings indicate they were not accompanied by alterations to autonomic function. Ultimately, this demonstrates further research is needed to understand the physiological underpinnings of alterations in brain function occurring immediately after a bout of soccer heading and how these may, over time, contribute to long-term neurological impairments.

Ethicolegal considerations of screening for brain injury in women who have experienced intimate partner violence

The vast majority of women who experience physical intimate partner violence (IPV) will likely suffer a brain injury (BI) as a result of the abuse. Accurate screening of IPV-BI can ensure survivors have access to appropriate health care and other supports, but screening results may also impact them receiving fair and equitable treatment in the legal system, and the justice they deserve. We used semi-structured interviews, combined with a contrastive vignette that described a realistic but hypothetical scenario involving IPV with or without BI, to explore the impact of BI on parenting disputes. Participants were lawyers (n = 12) whose focus is family law. Results highlight the potential adverse consequences of a positive BI screen that are influenced by the legal responsibility of counsel, the legal aid status of the woman, ongoing family dynamics, and the expectations of society while the focus on the best interests of the child is retained. Taken together, the findings reflect the legal vulnerability of women in decision-making about their capacity to parent after a BI. We conclude with recommendations for the future of IPV-BI screening aimed at mitigating risk and equipping women to navigate a legal system that has disadvantaged them, both historically and in the current context.

Characterization of Cognitive-Motor Function in Women Who Have Experienced Intimate Partner Violence-Related Brain Injury

Intimate partner violence (IPV) affects at least one in three women worldwide, and up to 92% report symptoms consistent with brain injury (BI). Although a handful of studies have examined different aspects of brain structure and function in this population, none has characterized potential deficits in cognitive-motor function. This knowledge gap was addressed in the current study by having participants who had experienced IPV complete the bimanual Object Hit & Avoid (OHA) task in a Kinesiological Instrument for Normal and Altered Reaching Movement (KINARM) End-Point Laboratory. BI load, post-traumatic stress disorder (PTSD), anxiety, depression, substance use, and history of abuse were also assessed. A stepwise multiple regression was undertaken to explore the relationship between BI load and task performance while accounting for comorbid psychopathologies. Results demonstrated that BI load accounted for a significant amount of variability in the number of targets hit and the average hand speed. PTSD, anxiety, and depression also contributed significantly to the variability in these measures as well as to the number and proportion of distractor hits, and the object processing rate. Taken together, these findings suggest that IPV-related BI, as well as comorbid PTSD, anxiety, and depression, disrupt the processing required to quickly and accurately hit targets while avoiding distractors. This pattern of results reflects the complex interaction between the physical injuries induced by the episodes of IPV and the resulting impacts that these experiences have on mental health.

A global collaboration to study intimate partner violence-related head trauma: The ENIGMA consortium IPV working group

Intimate partner violence includes psychological aggression, physical violence, sexual violence, and stalking from a current or former intimate partner. Past research suggests that exposure to intimate partner violence can impact cognitive and psychological functioning, as well as neurological outcomes. These seem to be compounded in those who suffer a brain injury as a result of trauma to the head, neck or body due to physical and/or sexual violence. However, our understanding of the neurobehavioral and neurobiological effects of head trauma in this population is limited due to factors including difficulty in accessing/recruiting participants, heterogeneity of samples, and premorbid and comorbid factors that impact outcomes. Thus, the goal of the Enhancing NeuroImaging Genetics through Meta-Analysis (ENIGMA) Consortium Intimate Partner Violence Working Group is to develop a global collaboration that includes researchers, clinicians, and other key community stakeholders. Participation in the working group can include collecting harmonized data, providing data for meta- and mega-analysis across sites, or stakeholder insight on key clinical research questions, promoting safety, participant recruitment and referral to support services. Further, to facilitate the mega-analysis of data across sites within the working group, we provide suggestions for behavioral surveys, cognitive tests, neuroimaging parameters, and genetics that could be used by investigators in the early stages of study design. We anticipate that the harmonization of measures across sites within the working group prior to data collection could increase the statistical power in characterizing how intimate partner violence-related head trauma impacts long-term physical, cognitive, and psychological health.

Using Behavior Change Theory to Understand How to Support Screening for Traumatic Brain Injuries Among Women Who Have Experienced Intimate Partner Violence

Background: Women who experience intimate partner violence (IPV) are at a high risk for traumatic brain injuries (TBIs). Women's shelters may be an ideal location for TBI screening. Behavior change theory can help understand factors that influence screening at women's shelters and develop interventions to promote screening. Objective: To use behavior change theory to understand the local context of women's shelters, factors influencing screening for TBIs among staff who work at women's shelters, and co-develop intervention recommendations to promote screening of TBIs at women's shelters. Methods: The research was conducted in three phases in partnership with the Kelowna Women's Shelter. In phase 1, participants (staff at women's shelters across Canada) completed an online survey that assessed their current TBI screening behaviors, knowledge of TBIs, and factors influencing screening. In phase 2, participants (staff at women's shelters in the Okanagan) completed an interview regarding the factors that influence screening for TBIs. In both phases, factors were analyzed using the Theoretical Domains Framework. In phase 3, intervention recommendations were co-developed using the Behavior Change Wheel. Results: In phase 1, findings indicate that participants (n = 150) lack skills (mean = 2.1, standard deviation [SD] = 1.9) and knowledge (mean = 2.9, SD = 2.2) with regard to screening and are nervous to screen (mean = 3.0, SD = 2.4) for TBIs. In phase 2, 194 barriers to screening for TBI were extracted from 10 interviews with staff members. Prominent domains included knowledge (37%), beliefs about capabilities (16%), and environmental context and resources (15%). Finally, in phase 3, five intervention recommendations were co-developed for interventions aiming to promote TBI screening in women's shelters. Conclusions: This thesis was the first theory-based study to develop intervention recommendations for promoting screening of TBIs at women's shelters. The recommendations have the potential to increase TBI screening at women's shelters ultimately improving the quality of life of women who have experienced a TBI from IPV.

An Acute Bout of Soccer Heading Subtly Alters Neurovascular Coupling Metrics

Objective: The current investigation examined how a bout of soccer heading may impact brain function.

Design: Semi-randomized crossover cohort.

Setting: Controlled soccer heading.

Participants: Seven male soccer players (24.1 ± 1.5 years).

Intervention: 40 successful soccer headers were performed in 20 min (25 m, launch velocity ~80 km/h). X2 xPatch recorded linear and rotational head accelerations during each impact. A contact control “sham” condition – ball made body contact, but not by the head; and a no activity time “control” condition were also completed.

Main Outcome Measures: Posterior and middle cerebral artery (PCA and MCA, respectively), cerebral blood velocity (CBV) was recorded during a visual task (neurovascular coupling: NVC) alongside SCAT3 symptoms scores pre/post a controlled bout of soccer heading.

Results: Cumulative linear and rotational accelerations were 1,574 ± 97.9 g and 313,761 ± 23,966 rads/s², respectively, during heading and changes in SCAT3 symptom number (pre: 2.6 ± 3.0; post: 6.7 ± 6.2, p = 0.13) and severity (pre: 3.7 ± 3.6, post: 9.4 ± 7.6, p = 0.11) were unchanged. In the PCA, no NVC differences were observed, including: relative CBV increase (28.0 ± 7.6%, p = 0.71) and total activation (188.7 ± 68.1 cm, p = 0.93). However, MCA-derived NVC metrics were blunted following heading, demonstrating decreased relative CBV increase (7.8 ± 3.1%, p = 0.03) and decreased total activation (26.7 ± 45.3 cm, p = 0.04).

Conclusion: Although an acute bout of soccer heading did not result in an increase of concussion-like symptoms, there were alterations in NVC responses within the MCA during a visual task. This suggests an acute bout of repetitive soccer heading can alter CBV regulation within the region of the brain associated with the header impacts.

A Prospective Transcranial Doppler Ultrasound-Based Evaluation of the Effects of Repetitive Subconcussive Head Trauma on Neurovascular Coupling Dynamics

OBJECTIVE

To determine the effects of repetitive subconcussive head trauma on neurovascular coupling (NVC) responses.

DESIGN

Prospective cohort study collected between September 2013 and December 2016.

SETTING

University laboratory.

PARTICIPANTS

One hundred seventy-nine elite, junior-level (age, 19.6 ± 1.5 years) contact sport (ice hockey, American football) athletes recruited for preseason testing. Fifty-two nonconcussed athletes returned for postseason testing. Fifteen noncontact sport athletes (age, 20.4 ± 2.2 years) also completed preseason and postseason testing.

EXPOSURE(S)

Subconcussive sport-related head trauma.

MAIN OUTCOME MEASURES

Dynamics of NVC were estimated during cycles of 20 seconds eyes closed and 40 seconds eyes open to a visual stimulus (reading) by measuring cerebral blood flow (CBF) velocity in the posterior (PCA) and middle (MCA) cerebral arteries via transcranial Doppler ultrasound.

RESULTS

Both athlete groups demonstrated no significant differences in PCA or MCA NVC dynamics between preseason and postseason, despite exposure to a median of 353.5 (range, 295.0-587.3) head impacts (>2g) over the course of the season for contact sport athletes.

CONCLUSIONS

Within the context of growing concern over detrimental effects of repetitive subconcussive trauma, the current results encouragingly suggest that the dynamics of NVC responses are not affected by 1 season of participation in junior-level ice hockey or American football. This is an important finding because it indicates an appropriate postseason CBF response to elevated metabolic demand with increases in neural activity.

Attention Is Required to Coordinate Reaching and Postural Stability during Upper Limb Movements Generated While Standing

In the present study we investigated how attention contributes to the interaction between reach planning and execution, and postural control. Reaching movements were generated while standing and were performed either in isolation or in conjunction with a secondary reaction time (RT) task. In addition, to better understand how online movement control is affected by this interaction, the reaching movements could be unexpectedly perturbed medial-laterally. Postural kinetic, arm kinematic and RT, and secondary RT measures were used to characterize the responses. Results indicate task performance worsened when both the reaching and secondary tasks were completed simultaneously. Our results imply the generation of reaching movements while standing requires attentional resources to properly coordinate the interaction between the reaching task and postural control.

The Time Course of Motoneuronal Excitability during the Preparation of Complex Movements

For a simple RT task, movement complexity increases RT and also corticospinal excitability, as measured by the motor evoked potential (MEP) elicited by TMS of the motor cortex. However, it is unknown if complexity-related increases in corticospinal excitability during the preparation of movement are mediated at the cortical or spinal level. The purposes of this study were to establish a time course of motoneuronal excitability before prime mover activation and to assess task-dependent effects of complex movements on motoneuronal and cortical excitability in a simple RT paradigm. It was hypothesized that motoneuronal and cortical excitability would increase before prime mover activation and in response to movement complexity. In a seated position, participants completed ballistic elbow extension/flexion movements with their dominant arm to one, two, or three targets. TMS and transmastoid stimulation (TS) were delivered at 0%, 70%, 80% or 90% of mean premotor RT for each complexity level. Stimulus intensities were set to elicit MEPs and cervicomedullary MEPs (CMEPs) of ∼10% of the maximal M-wave in the triceps brachii. Compared with 0% RT, motoneuronal excitability (CMEP amplitude) was already 10% greater at 70% RT. CMEP amplitude also increased with movement complexity as both the two- and three-movement conditions had greater motoneuronal excitability than the one-movement condition (p < .038). Importantly, when normalized to the CMEP, there was no increase in MEP amplitude. This suggests that complexity-related increases in corticospinal excitability are likely to be mediated more by increased excitability at a motoneuronal than cortical level.

Effects of transcranial direct current stimulation over right posterior parietal cortex on attention function in healthy young adults

Attention involves three distinct networks for alerting, orienting, and executive control. Interventions targeting the specific attentional networks remain lacking. Transcranial direct current stimulation (tDCS) has been shown to modulate cortical excitability, which potentially serves as an interventional tool to treat individuals with attention impairment. The purpose of this study was to examine the effects of applying tDCS over the right posterior parietal cortex (PPC) on the performance of the three attentional networks. Twenty-six healthy young adults performed the Attention Network Test before and after anodal or sham tDCS stimulation over the right PPC. The alerting, orienting, and executive effects were assessed before and after the stimulation. The results demonstrated that the orienting effect was significantly improved after real tDCS relative to sham, whereas the alerting and executive control effects remained unaffected. Consistent with previous clinical and functional imaging studies, this suggests that the right PPC is actively engaged with the spatial orienting of attention.

Cross-sectional comparison of spiral versus block integrated curriculums in preparing medical students to diagnose and manage concussions

BACKGROUND

An integrated curriculum is designed to be repetitive yet progressive and the concept has rapidly established itself within medical education. National organizations have recommended a shift to a spiral curriculum design, which uses both vertical and horizontal integration. This study examined differences between the recently implemented integrated spiral (class of 2019) and conventional block (classes of 2016-2018) MD curricula at the University of British Columbia (UBC) with respect to knowledge of concussion.

METHODS

Cross-sectional online survey (FluidSurveys: Fluidware, Ottawa, ON), distributed via email to UBC medical students during the 2015-2016 academic year. Questions focused on demographic data, knowledge of concussion definition, and management considerations. Differences in responses across the two groups were assessed using chi-square tests. Ordinal Likert-scale data were analyzed using Mann-Whitney U-Tests. Statistical significance was determined a priori at p < 0.05.

RESULTS

One hundred forty eight medical students (57% female) responded with 78 students in the spiral curriculum and 70 students the block curriculum. Important differences between responses from spiral versus block curricula students included: formal exposure to concussion-related educational material (10.8 h spiral vs. 3.95 h block), understanding concussions can occur without direct head impacts (90% spiral vs. 70% block, X²_1,148 = 9.41, p = 0.002) and identifying long-term consequences (dementia: 90% spiral vs. 66% block, X²_1,148 = 12.57, p < 0.0001; second impact syndrome: 80% spiral vs. 57% block, X²_1,148 = 8.60, p = 0.003; Parkinsonism: 47% spiral vs. 17% block, X²_1,148 = 14.87, p < 0.001). Block students identified the need for a full neurological exam (X²_1,148 = 17.63, p < 0.001) and had greater clinical exposure to acute concussion (47% block vs. 14% spiral, X²_1,148 = 19.27, p < 0.001) and post-concussion syndrome (37% block vs. 19% spiral, X²_1,148 = 5.91, p = 0.015).

CONCLUSIONS

The findings from this preliminary study suggest the spiral curriculum design, which emphasizes and revisits clinical competencies, promotes a strong understanding and retention of knowledge in highly prevalent clinical conditions such as concussion.

No change in plasma tau and serum neurofilament light concentrations in adolescent athletes following sport-related concussion

Sport-related concussion (SRC), a mild form of traumatic brain injury (TBI), is a common injury in contact sports. Health care professionals rely on subjective criteria (e.g., symptoms), as there is no objective marker for identification of athletes with SRC. Blood-based biomarkers have shown promise as diagnostic and prognostic tools following TBI and SRC. In the present study, we examined plasma tau and serum NF-L, two biomarkers for neuronal/axonal injury, concentrations at preseason and following SRC in contact sport athletes (n = 11) using ultrasensitive single molecule array (Simoa) assays. Preseason baseline samples were collected, and post-concussion samples were obtained at 6- and 14-days following injury. We found no difference between baseline, 6-day and 14-day post-concussion concentrations of tau (p = 0.14) or NF-L (p = 0.53). Further, no difference was found between preseason baseline and all post-SRC samples for tau (p = 0.22) or NF-L (p = 0.98). The total number of symptoms reported on the Standardized Assessment of Concussion– 3^rd Edition (SCAT3) and associated symptom severity scores increased from preseason to 6-days post-SRC but returned to baseline values at 14-days (p = 0.02 and p = 0.003, respectively). These results suggest that the severity of neuronal injury in this cohort of contact sport athletes with clinical uncomplicated SRC was too low to be detected by tau and NF-L measurements in blood samples obtained at 6- and 14-days post-injury.

Cerebral Autoregulation Is Disrupted Following a Season of Contact Sports Participation

Repetitive subconcussive head impacts across a season of contact sports participation are associated with a number of deficits in brain function. To date, no research has investigated the effect of such head impact exposure on dynamic cerebral autoregulation (dCA). To address this issue, 179 elite, junior-level (age 19.6 ± 1.5 years) contact sport (ice hockey, American football) athletes were recruited for pre-season testing. Fifty-two non-concussed athletes returned for post-season testing. Fifteen non-contact sport athletes (age 20.4 ± 2.2) also completed pre- and postseason testing. dCA was assessed via recordings of beat-by-beat mean arterial pressure (MAP) and middle cerebral artery blood velocity (MCAv) using finger photoplethysmography and transcranial Doppler ultrasound, respectively, during repetitive squat-stand maneuvers at 0.05 and 0.10 Hz. Transfer function analysis was used to determine Coherence (correlation), Gain (response amplitude), and Phase (response latency) of the MAP-MCAv relationship. Results showed that in contact sport athletes, Phase was reduced (p = 0.027) and Gain increased (p < 0.001) at post-season compared to pre-season during the 0.10 Hz squat-stand maneuvers, indicating cerebral autoregulatory impairment in both the latency and magnitude of the response. Changes in Phase were greater in athletes experiencing higher numbers and severity of head impacts. By contrast, no changes in dCA were observed in non-contact sport controls. Taken together, these results demonstrate that repetitive subconcussive head impacts occurring across a season of contact sports participation are associated with exposure-dependent impairments in the cerebrovascular pressure-buffering system capacity. It is unknown how long these deficits persist or if they accumulate year-over-year.

Heading in soccer increases serum neurofilament light protein and SCAT3 symptom metrics

Objectives

To determine the effect of heading a soccer ball on serum neurofilament light (NF-L) protein, plasma tau protein and symptom metrics including total number of symptoms reported and symptom severity scores on the Standardized Concussion Assessment Tool— 3rd edition (SCAT3).

Methods

Eleven male collegiate soccer players were recruited to take part in three experimental conditions including heading, sham and control conditions. Participants were required to perform 40 headers in 20 min in the heading condition, and control 40 soccer balls directed at them with their hands, chest or thigh in the sham condition. No ball contact was made during the control condition. Blood sampling and SCAT3 symptom assessments were completed prior to and 1 hour following conditions. A subset of participants returned 3 weeks following the heading condition for blood sampling.

Results

NF-L was elevated at 1 hour (p=0.004) and 1 month (p=0.04) following the heading condition, and at 1 hour (p=0.02) following the control condition. Tau levels remained unchanged following all conditions. The total number of symptoms (TS) and symptom severity (SS) scores from the SCAT3 were both elevated following the heading condition (p=0.01 and p=0.03, respectively). Both TS and SS decreased following sham (p=0.04 and p=0.04) and control conditions (p=0.04 and p=0.04).

Conclusion

An acute bout of soccer heading is associated with increased NF-L concentrations at 1 hour and 1 month following the session and can lead to symptoms commonly reported following sport-related concussion.

Anticipatory postural adjustments as a function of response complexity in simple reaction time tasks

The central nervous system preplans postural responses to successfully perform complex multi-joint movements. These responses have been termed anticipatory postural adjustments (APAs), and they constitute a general type of response to stabilize posture prior to movement initiation. APA sequences are elicited with shorter latency when a startling acoustic stimulus is applied, demonstrating their preplanned nature. Increasing task complexity using a simple reaction time (RT) paradigm has been shown to delay limb movement RT as a result of additional planning or sequencing requirements; however, the effect of task complexity on APA dynamics is unclear. The purpose of the present study was to investigate if task complexity modulates APA onset in a manner analogous to that observed in the primary effector. 13 participants completed 150 trials of simple (1-target) and complex (2- or 3-target) arm movements while standing on a force plate. Results indicated participants had significantly faster arm movement RTs in the simple versus the most complex condition. Similar to the primary effector, APA RTs were longer in the most complex (3-target) movement compared to both the 1-target and 2-target movements. Furthermore, APA excursion velocities were scaled to the complexity of the upcoming movement: the rate of APAs increased from simplest to most complex movements. These findings clearly demonstrate APAs are sensitive to task complexity, further elucidating their preplanned role in stabilizing posture which enables the successful completion of intended movements.

A History of Concussion Does Not Lead to an Increase in Ocular Near Point of Convergence

Ocular near point of convergence (NPC) has been shown to be sensitive to the effects of concussion and subconcussive impacts. To determine if NPC is also sensitive to a previous history of concussion, male contact-sport athletes either with (n=26) or without (n=16) a history of at least one previous concussion had their NPC assessed. The results showed that participants with a history of concussion displayed NPC values (9.4±1.6 cm) indistinguishable from those with no history of concussion (8.4±2.1 cm, t-test, p=0.09). This was the case regardless of whether 1, 2, or 3 or more concussions had occurred and despite the fact participants with concussion (mean time since last concussion: 1136 days) suffered from an increased number and severity of symptoms as assessed with the SCAT 3 (3.6±2.2 vs. 2.13±1.89 symptoms, 6.1±4.1 vs. 3.19±2.99 severity, t-test, p<0.05). Taken together, these results imply that NPC may not be a suitable tool to assess the potential long-term effects of one or more concussions over a longer time frame. Future research using larger sample sizes is warranted to evaluate the potential dose-response relationship between number of prior concussions and NPC.

Imaging in Pediatric Concussion: A Systematic Review

CONTEXT

Pediatric mild traumatic brain injury (mTBI) is a common and poorly understood injury. Neuroimaging indexes brain injury and outcome after pediatric mTBI, but remains largely unexplored.

OBJECTIVE

To investigate the differences in neuroimaging findings in children/youth with mTBI. Measures of behavior, symptoms, time since injury, and age at injury were also considered.

DATA SOURCES

A systematic review was conducted up to July 6, 2016.

STUDY SELECTION

Studies were independently screened by 2 authors and included if they met predetermined eligibility criteria: (1) children/youth (5-18 years of age), (2) diagnosis of mTBI, and (3) use of neuroimaging.

DATA EXTRACTION

Two authors independently appraised study quality and extracted demographic and outcome data.

RESULTS

Twenty-two studies met the eligibility criteria, involving 448 participants with mTBI (mean age = 12.7 years ± 2.8). Time postinjury ranged from 1 day to 5 years. Seven different neuroimaging methods were investigated in included studies. The most frequently used method, diffusion tensor imaging (41%), had heterogeneous findings with respect to the specific regions and tracts that showed group differences. However, group differences were observed in many regions containing the corticospinal tract, portions of the corpus callosum, or frontal white-matter regions; fractional anisotropy was increased in 88% of the studies.

LIMITATIONS

This review included a heterogeneous sample with regard to participant ages, time since injury, symptoms, and imaging methods which prevented statistical pooling/modelling.

CONCLUSIONS

These data highlight essential priorities for future research (eg, common data elements) that are foundational to progress the understanding of pediatric concussion.

Sport-Related Concussion Alters Indices of Dynamic Cerebral Autoregulation

Sport-related concussion is known to affect a variety of brain functions. However, the impact of this brain injury on cerebral autoregulation (CA) is poorly understood. Thus, the goal of the current study was to determine the acute and cumulative effects of sport-related concussion on indices of dynamic CA. Toward this end, 179 elite, junior-level (age 19.6 ± 1.5 years) contact sport (ice hockey, American football) athletes were recruited for preseason testing, 42 with zero prior concussions and 31 with three or more previous concussions. Eighteen athletes sustained a concussion during that competitive season and completed follow-up testing at 72 h, 2 weeks, and 1 month post injury. Beat-by-beat arterial blood pressure (BP) and middle cerebral artery blood velocity (MCAv) were recorded using finger photoplethysmography and transcranial Doppler ultrasound, respectively. Five minutes of repetitive squat-stand maneuvers induced BP oscillations at 0.05 and 0.10 Hz (20- and 10-s cycles, respectively). The BP-MCAv relationship was quantified using transfer function analysis to estimate Coherence (correlation), Gain (amplitude ratio), and Phase (timing offset). At a group level, repeated-measures ANOVA indicated that 0.10 Hz Phase was significantly reduced following an acute concussion, compared to preseason, by 23% (-0.136 ± 0.033 rads) at 72 h and by 18% (-0.105 ± 0.029 rads) at 2 weeks post injury, indicating impaired autoregulatory functioning; recovery to preseason values occurred by 1 month. Athletes were cleared to return to competition after a median of 14 days (range 7-35), implying that physiologic dysfunction persisted beyond clinical recovery in many cases. When comparing dynamic pressure buffering between athletes with zero prior concussions and those with three or more, no differences were observed. Sustaining an acute sport-related concussion induces transient impairments in the capabilities of the cerebrovascular pressure-buffering system that may persist beyond 2 weeks and may be due to a period of autonomic dysregulation. Athletes with a history of three or more concussions did not exhibit impairments relative to those with zero prior concussions, suggesting recovery of function over time. Findings from this study support the potential need to consider physiological recovery in deciding when patients should return to play following a concussion.

The potential for animal models to provide insight into mild traumatic brain injury: Translational challenges and strategies

Mild traumatic brain injury (mTBI) is a common health problem. There is tremendous variability and heterogeneity in human mTBI, including mechanisms of injury, biomechanical forces, injury severity, spatial and temporal pathophysiology, genetic factors, pre-injury vulnerability and resilience factors, and clinical outcomes. Animal models greatly reduce this variability and heterogeneity, and provide a means to study mTBI in a rigorous, controlled, and efficient manner. Rodent models, in particular, are time- and cost-efficient, and they allow researchers to measure morphological, cellular, molecular, and behavioral variables in a single study. However, inter-species differences in anatomy, morphology, metabolism, neurobiology, and lifespan create translational challenges. Although the term "mild" TBI is used often in the pre-clinical literature, clearly defined criteria for mild, moderate, and severe TBI in animal models have not been agreed upon. In this review, we introduce current issues facing the mTBI field, summarize the available research methodologies and previous studies in mTBI animal models, and discuss how a translational research approach may be useful in advancing our understanding and management of mTBI.

Motor Planning Influences the Perceived Timing of Vibrotactile Stimuli in an Amplitude-Dependent Manner

The authors characterized how motor planning influences temporal order judgment (TOJ) tasks. They examined this by applying vibrotactile stimulation during the planning stages of a bimanual arm movement that would bring the arms into a crossed configuration. The authors have previously shown that planning to cross the arms induces a subjective reversal of spatially defined temporal order judgments that evolves over the course of the planning period. It was unclear, however, whether this effect is modulated by the extent to which the arms would be crossed after movement. The authors examined this issue by having participants plan to move to 4 different targets that would leave the arms in crossed configurations of varying extents. The results demonstrate that even though cutaneous stimuli were applied before the movements, if participants were planning to move into a more crossed configuration, performance on the TOJ task worsened depending on where they were in the planning process. This data suggest the brain uses planning signals to predict sensations from impending movements in a context-dependent manner.

Dynamic cerebral autoregulation in young athletes following concussion

The purpose of this study was to examine cerebral autoregulation (CA) in young athletes experiencing concussion. The subjects were monitored and repeatedly tested 72 hours, 2 weeks and 1 month post-injury. Mean arterial blood pressure (MABP), end-tidal partial pressure of carbon dioxide (PETCO2) and cerebral blood flow velocity (CBFV) in the middle and posterior cerebral arteries were monitored during mental activation paradigms. In order to characterize CA we employed autoregressive models with exogenous inputs (ARX) and impulse response models based on the Laguerre expansion technique (LET). By extracting gain and phase estimates from the obtained models we were able to detect disruptions in CA 72 hours following concussion and a slow recovery within a time period of one month.

Myelin Water Fraction Is Transiently Reduced after a Single Mild Traumatic Brain Injury--A Prospective Cohort Study in Collegiate Hockey Players

Impact-related mild traumatic brain injuries (mTBI) are a major public health concern, and remain as one of the most poorly understood injuries in the field of neuroscience. Currently, the diagnosis and management of such injuries are based largely on patient-reported symptoms. An improved understanding of the underlying pathophysiology of mTBI is urgently needed in order to develop better diagnostic and management protocols. Specifically, dynamic post-injury changes to the myelin sheath in the human brain have not been examined, despite ‘compromised white matter integrity’ often being described as a consequence of mTBI. In this preliminary cohort study, myelin water imaging was used to prospectively evaluate changes in myelin water fraction, derived from the T2 decay signal, in two varsity hockey teams (45 players) over one season of athletic competition. 11 players sustained a concussion during competition, and were scanned at 72 hours, 2 weeks, and 2 months post-injury. Results demonstrated a reduction in myelin water fraction at 2 weeks post-injury in several brain areas relative to preseason scans, including the splenium of the corpus callosum, right posterior thalamic radiation, left superior corona radiata, left superior longitudinal fasciculus, and left posterior limb of the internal capsule. Myelin water fraction recovered to pre-season values by 2 months post-injury. These results may indicate transient myelin disruption following a single mTBI, with subsequent remyelination of affected neurons. Myelin disruption was not apparent in the athletes who did not experience a concussion, despite exposure to repetitive subconcussive trauma over a season of collegiate hockey. These findings may help to explain many of the metabolic and neurological deficits observed clinically following mTBI.

Tactile gating in a reaching and grasping task

Abstract A multitude of events bombard our sensory systems at every moment of our lives. Thus, it is important for the sensory cortex to gate unimportant events. Tactile suppression is a well-known phenomenon defined as a reduced ability to detect tactile events on the skin before and during movement. Previous experiments found detection rates decrease just prior to and during finger abduction, and decrease according to the proximity of the moving effector. This study examined how tactile detection changes during a reach to grasp. Fourteen human participants used their right hand to reach and grasp a cylinder. Tactors were attached to the index finger, the fifth digit, and the forearm of both the right and left arm and vibrated at various epochs relative to a "go" tone. Results showed that detection rates at the forearm decreased before movement onset; whereas at the right index finger, right fifth digit and at the left index finger, left fifth digit, and forearm sites did not decrease like in the right forearm. These results indicate that the task affects gating dynamics in a temporally- and contextually dependent manner and implies that feed-forward motor planning processes can modify sensory signals.

Learning about gravity: segmental assessment of upright control as infants develop independent sitting

The question of how infants attain upright sitting is at the core of understanding the development of most functional abilities. Our simple, practical method of securing the hips and different trunk segments while evaluating the infant's ability to vertically align and stabilize the trunk in space contributes a useful method and new insights into the development of upright control. Previous studies have considered the trunk to develop as a single segment. The goal of the present study was to examine how postural control changes across multiple trunk segments during typical development (TD) of sitting balance. For this purpose, electromyography (EMG) and kinematic data were collected at four levels of trunk support (axillae, midribs, waist, hips), in a longitudinal study of eight TD infants (3-9 mo of age). We found that developmental changes in stability were specific to the region of the trunk being investigated, changes in antagonistic muscle activity differed for the anterior-posterior versus the medial-lateral axis, and the relationship between muscle activation and movement changed from erratic attempts to gain upright position to anticipatory graded responses as infants developed upright control through a four-stage behavioral process. This information can be used by researchers to further refine hypotheses regarding this developmental process and by clinicians who wish to develop and test more specific treatment programs for children with postural dysfunction.

Expectations can modulate the frequency and timing of multiple saccades: a TMS study

This study was undertaken to determine if target predictability could modulate saccadic planning and timing at the level of the frontal eye fields (FEF). To this end, healthy participants performed two gap saccade tasks in which the targets were displaced left or right of the midline in either a predictable or a random fashion. Additionally, half of the participants were informed about this manipulation. Single pulse transcranial magnetic stimulation (TMS) was applied to the left FEF before, during, or after the target onset. We examined both the saccade latency and the frequency of multiple saccades (MS) (i.e., saccades that covered <90 % of the distance to the target and were subsequently followed by a corrective saccade). Findings revealed that saccadic reaction times were quickest to the more predictable target side and also confirmed that MS were released more quickly than single saccades. Further, the frequency of MS differed between target locations; higher frequencies of MS were found on the unpredictable side, showing more vulnerability to TMS disruption. In conclusion, we have demonstrated that target predictability modulates saccade planning and that this modulation takes place at least in part in the FEF. The influence of FEF in these processes is observed both in the latencies with which saccades are executed and in the timing and characteristics of the multiple saccades that are observed under different task constraints. Finally, the timing of the FEF contribution also appears to be influenced by the manipulation of target predictability. Each of these observations serves to further clarify the role of the human FEF in saccade planning.

Development of postural control during gait in typically developing children: the effects of dual-task conditions

The purpose of this study was to investigate the typical development of postural control in younger (5-6 yrs) and older (7-16 yrs) children (YTD and OTD) during two gait tasks, including level walking and obstacle-crossing, using a dual-task paradigm, and to compare the results of the children's performance with that of healthy young adults (HYA). Our findings revealed that gait control in typical children requires attentional resources to maintain stability. Moreover, dual-task interference was less in HYA compared to YTD and OTD. Gait performance decrements in the dual-task context were greater in YTD compared to OTD, whereas cognitive performance decrements in YTD and OTD were similar. In addition, dual-tasking affected cognitive performance more in YTD when gait task difficulty was increased. Results suggest a developmental trend in attentional resources used to control gait in typical children. Postural control during gait under dual-task conditions was improved when children were more mature, as attentional resources increased with age.