Spatial orientation of attention and obstacle avoidance following concussion

Different neurocognitive controls modulate obstacle avoidance through pregnancy

Understanding why falls during pregnancy occur at over 25% rate over gestation has clinical impacts on the health of pregnant individuals. Attention, proprioception, and perception of the environment are required to prevent trips and falls. This research aimed to understand how the changes to these neurocognitive processes control obstacle avoidance through gestation. Seventeen pregnant participants were tested five times in 6-week intervals. Participants walked an obstacle course (OC), and we analyzed the crossings over obstacles that were set to 10% of participants' body height. Participants also performed an attentional network test (ANT: performance of specific components of attention), an obstacle perception task (OP: ability to visually define an obstacle and translate that to a body posture), and a joint position sense task (JPS: ability to recognize and recreate a joint position from somatosensation). In the OC task, average leading and trailing foot crossing heights significantly reduced by 13% and 23% respectively, with no change in variation, between weeks 13 and 31 of pregnancy, indicating an increased risk of obstacle contact during this time. The variability in minimum leading foot distances from the obstacle was correlated with all three neurocognition tasks (ANT, OP, and JPS). Increased fall rates in the second and third trimesters of pregnancy may be driven by changes in attention, with additional contributions of joint position sense and environmental perception at various stages of gestation. The results imply that a holistic examination on an individual basis may be required to determine individual trip risk and appropriate safety modifications.

Vestibular perceptual testing from lab to clinic: a review

Not all dizziness presents as vertigo, suggesting other perceptual symptoms for individuals with vestibular disease. These non-specific perceptual complaints of dizziness have led to a recent resurgence in literature examining vestibular perceptual testing with the aim to enhance clinical diagnostics and therapeutics. Recent evidence supports incorporating rehabilitation methods to retrain vestibular perception. This review describes the current field of vestibular perceptual testing from scientific laboratory techniques that may not be clinic friendly to some low-tech options that may be more clinic friendly. Limitations are highlighted suggesting directions for additional research.

Methodological Critique of Concussive and Non-Concussive Dual Task Walking Assessments: A Scoping Review

OBJECTIVE

To understand the methodological approaches taken by various research groups and determine the kinematic variables that could consistently and reliably differentiate between concussed and non-concussed individuals.

METHODS

MEDLINE via PubMed, CINAHL Complete via EBSCO, EBSCOhost, SPORTDiscus, and Scopus were searched from inception until 31 December 2021, using key terms related to concussion, mild traumatic brain injury, gait, cognition and dual task. Studies that reported spatiotemporal kinematic outcomes were included. Data were extracted using a customised spreadsheet, including detailed information on participant characteristics, assessment protocols, equipment used, and outcomes.

RESULTS

Twenty-three studies involving 1030 participants met the inclusion criteria. Ten outcome measures were reported across these articles. Some metrics such as gait velocity and stride length may be promising but are limited by the status of the current research; the majority of the reported variables were not sensitive enough across technologies to consistently differentiate between concussed and non-concussed individuals. Understanding variable sensitivity was made more difficult given the absence of any reporting of reliability of the protocols and variables in the respective studies.

CONCLUSION

Given the current status of the literature and the methodologies reviewed, there would seem little consensus on which gait parameters are best to determine return to play readiness after concussion. There is potential in this area for such technologies and protocols to be utilised as a tool for identifying and monitoring concussion; however, improving understanding of the variability and validity of technologies and protocols underpins the suggested directions of future research. Inertial measurement units appear to be the most promising technology in this aspect and should guide the focus of future research.

IMPACT

Results of this study may have an impact on what technology is chosen and may be utilised to assist with concussion diagnosis and return to play protocols.

Multi-domain assessment of sports-related and military concussion recovery: A scoping review

OBJECTIVE

This review explores the literature on multi-domain assessments used in concussion recovery, to inform evidence-based and ecologically valid return-to-play. It asks: What simultaneous, dynamic multi-domain paradigms are used to assess recovery of youth and adults following concussion?

METHODS

Five databases were searched (CINAHL, EMBASE, MEDLINE, PsycInfo, SPORTDiscus) until September 30, 2021. Records were limited to those published in peer-reviewed journals, in English, between 2002 and 2021. Included studies were required to describe the assessment of concussion recovery using dynamic paradigms (i.e., requiring sport-like coordination) spanning multiple domains (i.e., physical, cognitive, socio-emotional functioning) simultaneously.

RESULTS

7098 unique articles were identified. 64 were included for analysis, describing 36 unique assessments of 1938 concussed participants. These assessments were deconstructed into their constituent tasks: 13 physical, 17 cognitive, and one socio-emotional. Combinations of these "building blocks" formed the multi-domain assessments. Forty-six studies implemented level walking with a concurrent cognitive task. The most frequently implemented cognitive tasks were 'Q&A' paradigms requiring participants to answer questions aloud during a physical task.

CONCLUSIONS

A preference emerged for dual-task assessments, specifically combinations of level walking and Q&A tasks. Future research should balance ecological validity and clinical feasibility in multi-domain assessments, and work to validate these assessments for practice.

Deficits in visuospatial attentional cueing following mild traumatic brain injury

Visual attentional deficits are frequently reported in patients with mild traumatic brain injury (TBI). In the present study, the ability to orient visual attention (i.e., the use of endogenous and exogenous visual cues) was investigated using a modified Posner visual search task, in which the participant was required to search for a target shape (radial frequency patterns) amongst distractor shapes. Participants were required to determine whether a target radial frequency pattern was present or absent from an array of distractors. Attention to the target location was cued using central or peripheral cueing procedures to investigate endogenous or exogenous attention allocation. Predictability was not manipulated between central and peripheral cues. Search difficulty was varied by systematically changing the radial frequency difference between target and distractors (and thereby shape difference), and cues could be valid or invalid in that they correctly or incorrectly indicated the position of the target shape. Both target discriminability (i.e., identifying the presence or absence of the target) and reaction times were measured. Thirteen patients with chronic mild TBI and 21 age-, sex-, and IQ -matched healthy controls participated in the study. For control participants, both discrimination accuracy and reaction times improved with visual search efficiency, and they were sensitive to the type of cue, with performance worst for cue invalid conditions than valid conditions. However, the results for TBI patients were strikingly different; we find that discrimination accuracy slightly improved with visual search difficulty (compared to controls), but not reaction times, and TBI patients were largely insensitive to the type of visual cue, and did not show a selective deficit for central or peripheral cues, suggesting an impairment in both endogenous and exogenous visual attention. In conclusion, patients with mild TBI exhibit a poor ability to orient visual attention.

Altered Brain Functional Connectivity in Female Athletes Over the Course of a Season of Collision or Contact Sports

University athletes are exposed to numerous impacts to the body and head, though the potential cumulative effects of such hits remain elusive. This study examined resting-state functional connectivity (rsFC) of brain networks in female varsity athletes over the course of a season. Nineteen female university athletes involved in collision (N = 12) and contact (N = 7) sports underwent functional magnetic resonance imaging scans at both pre- and post-season. A group-level independent component analysis (ICA) was used to investigate differences in rsFC over the course of a season and differences between contact and collision sport athletes. Decreased rsFC was observed over the course of the season between the default mode network (DMN) and regions in the frontal, parietal, and occipital lobe (p false discovery rate, ≤0.05) driven by differences in the contact group. There was also a main effect of group in the dorsal attention network (DAN) driven by differences between contact and collision groups at pre-season. Differences identified over the course of a season of play indicate largely decreased rsFC within the DMN, and level of contact was associated with differences in rsFC of the DAN. The association between exposure to repetitive head impacts (RHIs) and observed changes in network rsFC supplements the growing literature suggesting that even non-concussed athletes may be at risk for changes in brain functioning. However, the complexity of examining the direct effects of RHIs highlights the need to consider multiple factors, including mental health and sport-specific training and expertise, that may potentially be associated with neural changes.

Visuospatial Attention Allocation as an Indicator of Cognitive Deficit in Traumatic Brain Injury: A Systematic Review and Meta-Analysis

Traumatic Brain Injury (TBI) is defined by changes in brain function resulting from external forces acting on the brain and is typically characterized by a host of physiological and functional changes such as cognitive deficits including attention problems. In the present study, we focused on the effect of TBI on the ability to allocate attention in vision (i.e., the use of endogenous and exogenous visual cues) by systematically reviewing previous literature on the topic. We conducted quantitative synthesis of 16 selected studies of visual attention following TBI, calculating 80 effect size estimates. The combined effect size was large (g = 0.79, p < 0.0001) with medium heterogeneity (I² = 68.39%). Subgroup analyses revealed an increase in deficit with moderate-to-severe and severe TBI as compared to mild TBI [F_{(2, 76)} = 24.14, p < 0.0001]. Task type was another key source of variability and subgroup analyses indicated that higher order attention processes were severely affected by TBI [F_{(2, 77)} = 5.66, p = 0.0051). Meta-regression analyses revealed significant improvement in visual attention deficit with time [p(mild) = 0.031, p(moderate-to-severe) = 0.002, p(severe) < 0.0001]. Taken together, these results demonstrate that visual attention is affected by TBI and that regular assessment of visual attention, using a systematic attention allocation task, may provide a useful clinical measure of cognitive impairment and change after TBI.

Performance during dual-task walking in a corridor after mild traumatic brain injury: A potential functional marker to assist return-to-function decisions

Objective: To compare the performance of participants with mTBI and healthy control on locomotor-cognitive dual-tasks in a corridor with limited technology.Design: Prospective study of twenty participants with mTBI (10 women; 22.10 ± 2.97 years; 70.9 ± 22.31 days post-injury), and 20 sex- and age-matched control participants (10 women; 22.55 ± 2.72 years).Methods: Participants performed six different dual-tasks combining locomotor tasks (level-walking, obstacle-crossing, and tandem gait) and cognitive tasks (counting backwards and verbal fluency). Symptoms and neuropsychological performance were also assessed.Results: No differences between groups were found for symptoms and neuropsychological measures. For gait speed, the group effect was not significant, but a significant group X cognitive task interaction was found, revealing a tendency toward slower gait speed in the mTBI group during dual-task conditions. A significantly greater dual-task cost for gait speed was found for the mTBI group. Although no statistically significant differences in cognitive performance were observed during dual-tasks, the mTBI group subjectively reported being significantly less concentrated.Conclusion: The present study revealed that in persons who seem to have well recovered after mTBI, on average 71 days post-injury, alterations in gait are detectable using a simple, "low-tech," corridor-based dual-task walking assessment.

Using IMU-based kinematic markers to monitor dual-task gait balance control recovery in acutely concussed individuals

BACKGROUND

Concussion may result in acutely impaired dynamic balance control that can persist up to two months post injury. Such impairment has been detected using sophisticated whole body center of mass kinematic metrics derived from camera-based motion analysis under a dual-task paradigm. However, wearable sensor kinematics for describing gait imbalance is lacking.

METHODS

This study employed a longitudinal design. Gait balance control of acutely concussed and healthy matched control participants was assessed at five post-injury time points (within 72 h of injury, at one week, two weeks, one month, and two months). Tri-axial accelerations and angular velocities were collected with a dual-task gait protocol using an inertial measurement unit placed over the fifth lumbar vertebra.

FINDINGS

Eight consistent gait event specific peak accelerations and six peak angular velocities measured by the inertial measurement unit were examined. Peak yaw and roll angular velocities at heel strike and peak roll angular velocities during early single-support, distinguished healthy from concussed participants across the two month post-injury period, while peak vertical acceleration at the end of terminal stance peak medial-lateral acceleration to the right during loading response showed promise.

INTERPRETATION

Utilization of peak accelerations and angular velocities collected from a single inertial measurement unit placed over the fifth lumbar vertebra in a divided attention paradigm may offer a clinically feasible method for detecting subtle changes in gait balance control in concussed individuals.

Using functional movement tests to investigate the presence of sensorimotor impairment in amateur athletes following sport-related concussion: A prospective, longitudinal study

OBJECTIVE

To longitudinally investigate the presence of sensorimotor impairments in amateur athletes following sport-related concussion using two functional movement tests.

DESIGN

Prospective, longitudinal study.

SETTING

Human movement analysis laboratory.

PARTICIPANTS

Athletes who presented to a hospital emergency department and were diagnosed with sport-related concussion, and sex-, age-, and activity-matched non-concussed, control athletes. Concussed participants were assessed within one-week following sport-related concussion, upon clearance to return-to-sporting activity (RTA), and two weeks after RTA. Control participants were assessed at an initial time-point and approximately two and four weeks following their initial study assessment.

MAIN OUTCOMES MEASURES

At each laboratory assessment, participants completed two functional movement tests: the Star Excursion Balance Test to evaluate anterior reach distance (normalised for leg length) and fractal dimension (centre of pressure path complexity), and the Multiple Hop Test to evaluate corrective postural strategies and time-to-stabilisation.

RESULTS

Fifty concussed athletes and 50 control athletes completed the study. There were no significant differences at any study assessment between the concussion and control group on the Star Excursion Balance Test anterior reach distance or fractal dimension (centre of pressure path complexity). During the Multiple Hop Test, the concussion group used a significantly greater number of corrective postural strategies than the control group one-week following sport-related concussion and upon clearance to RTA, but not two weeks following RTA.

CONCLUSION

Recently concussed athletes made a greater number of corrective postural strategies than control participants during the Multiple Hop Test upon clearance to RTA but not two weeks after RTA. The Multiple Hop Test may offer a clinically useful tool for practitioners to examine the recovery of subtle sensorimotor impairments and related RTA readiness.

Gait Performance in People with Symptomatic, Chronic Mild Traumatic Brain Injury

There is a dearth of knowledge about how symptom severity affects gait in the chronic (>3 months) mild traumatic brain injury (mTBI) population despite up to 53% of people reporting persisting symptoms after mTBI. The aim of this investigation was to determine whether gait is affected in a symptomatic, chronic mTBI group and to assess the relationship between gait performance and symptom severity on the Neurobehavioral Symptom Inventory (NSI). Gait was assessed under single- and dual-task conditions using five inertial sensors in 57 control subjects and 65 persons with chronic mTBI (1.0 year from mTBI). The single- and dual-task gait domains of Pace, Rhythm, Variability, and Turning were calculated from individual gait characteristics. Dual-task cost (DTC) was calculated for each domain. The mTBI group walked (domain z-score mean difference, single-task = 0.70; dual-task = 0.71) and turned (z-score mean difference, single-task = 0.69; dual-task = 0.70) slower (p < 0.001) under both gait conditions, with less rhythm under dual-task gait (z-score difference = 0.21; p = 0.001). DTC was not different between groups. Higher NSI somatic subscore was related to higher single- and dual-task gait variability as well as slower dual-task pace and turning (p < 0.01). Persons with chronic mTBI and persistent symptoms exhibited altered gait, particularly under dual-task, and worse gait performance related to greater symptom severity. Future gait research in chronic mTBI should assess the possible underlying physiological mechanisms for persistent symptoms and gait deficits.

Gait Deviations Associated With Concussion: A Systematic Review

BACKGROUND

Gait deviations resulting from concussion are important to consider in the diagnosis, treatment progression, and return to activity after a concussion.

OBJECTIVE

To identify quantifiable gait deviations associated with concussion across populations and time since injury.

METHODS AND MATERIALS

Six electronic databases were systematically searched from January 1974 to September 2016. Studies selected included original data, had an analytic design, and reported a quantifiable gait parameter in individuals who had sustained a concussion as defined by the American Congress of Rehabilitation Medicine or related definitions. Preferred Reporting Items for Systematic reviews and Meta-Analysis guidelines were followed. Two independent authors assessed study quality [Downs and Black (DB) criteria] and level of evidence (Oxford Center of Evidence-Based Medicine Model).

RESULTS

Of 2650 potentially relevant articles, 21 level 4 studies were included. The median DB score was 12/33 (range 10-16). Heterogeneity in gait parameters and timing of postconcussion testing precluded meta-analysis. There is consistent level 4 evidence of increased medial-lateral center-of-mass displacement, and inconsistent level 4 evidence of decreased gait velocity after concussion. Further, there is preliminary level 4 evidence that gait deficits may exist beyond the typical 10-day recovery period and return to activity.

CONCLUSION

These findings suggest that individuals who have suffered a concussion may sway more in the frontal plane, and walk slower compared to healthy controls. Consensus about the most important gait parameters for concussion diagnosis and clinical management are lacking. Further, high-quality prospective cohort studies evaluating changes in gait from time of concussion to return to activity, sport, recreation and/or work are needed.

Remote concussion history does not affect visually-guided reaching in young adult females

Aim:

We examined the long-term effects of concussions in young adult females on visuomotor behavior during a visually-guided reaching task of various complexities.

Materials & methods:

20 females with a history of longer than 6 months since a concussion and 20 healthy females quickly and accurately performed a delayed reach to a previously cued target.

Results:

As both cognitive and motor load increased, task performance decreased for both groups (p < 0.05). However, contrary to our primary hypothesis, no differences in task performance were found between the two experimental groups (p > 0.05).

Conclusion:

The young adult females with a remote history of concussion demonstrated no deficits in visuomotor behavior on an attention-mediated reaching task as compared with control participants.

Current literature is inconclusive regarding the long-term effects of concussion. Some have argued that the differing results are due to many uncontrolled factors in study design. In this study, 20 females with a history of concussion more than 6 months ago and 20 healthy females performed a reaching task under different levels of difficulty. As the reaching task got harder, both groups had greater difficulty doing the task quickly and accurately (p < 0.05). Surprisingly, however, no differences in reaching performance existed between the two groups (p > 0.05). Young adult females with a remote history of concussion demonstrated no greater problems with complicated reaching tasks when compared with control participants when experimental conditions are tightly controlled.

Re-conceptualizing postural control assessment in sport-related concussion: Transitioning from the reflex/hierarchical model to the systems model

Background: While postural control impairment is common following sport-related concussion, few investigations have studied the physiological basis for this impairment. Both the Reflex/Hierarchical Model and the Systems Model are commonly used to characterize the physiological basis of postural control.Purpose: To discuss the physiological basis of postural control impairment resulting from sport-related concussion based on these models and suggest directions for future research.Methods: Narrative literature review.Findings: Postural control impairment seen with sport-related concussion is a multifaceted construct that can result from deficits in numerous systems that underlie postural control as described by the Systems Model, rather than a unidimensional construct that stems from the central nervous systems' inability to integrate sensory input to control posture as per the Reflex/Hierarchical Model.Conclusion: We recommend a transition away from the Hierarchical/Reflex Model of postural control towards the Systems Model in the conceptualization of sport-related concussion. Future research on postural control following sport-related concussion should account for the multifaceted nature of the resulting postural control impairment based on the Systems Model. Clinically, there is a need for a clinical postural control test that allows examination across the affected systems under single-task, dual-task, and sport-specific paradigms.

Single and dual tandem gait assessment post concussion: What performance time is clinically relevant across adult ages and what can influence results?

AIM

The three-metre tandem gait test (TG) is used to assess postural control during locomotion following sports concussion. However, values used to determine a pass/fail result are currently based on young athletic populations. Times for test completion may be influenced by several intrinsic or extrinsic factors. The aim of this study was to collate healthy individual single, dual task as well as dual task cost - motor TG times for a non-elite athlete population, across several age groups, and to investigate several potential influencing factors.

METHODS

Healthy individuals aged 18-55+, who had never experienced a concussion completed single and dual task TG following the SCAT5 protocol. A separate group (n = 20, age, foot length and body mass index matched) performed the tests with alternate instructions.

RESULTS

Mean best TG time for all participants were: single task 21.03 (±5.26s), dual task 29.59 (±9.84s) and DTC-motor 8.57 (±7.5s:41.7%). Age and foot length but not specificity of verbal instructions were related to TG times. Significantly slower single and dual task times were identified for the 55 + age group when compared to the three youngest groups (p < 0.01). No difference was seen for DTC-motor time or % between age groups (p > 0.05).

CONCLUSION

Healthy individual data collected exceeded previously reported average times. Faster times were evident in younger participants and those with longer foot length. Results from this study can be used as a reliable guideline to inform clinical decisions around the pass/fail result of TGT across age ranges in non-elite athlete populations post-concussion.

Effects of Recent Concussion and Injury History on Instantaneous Relative Risk of Lower Extremity Injury in Division I Collegiate Athletes

BACKGROUND

Growing evidence suggests that concussion increases the risk of lower extremity (LE) musculoskeletal injury. However, it is unclear to how the effect of concussion on LE injury risk may be influenced by previous injuries. This study sought to examine the association between concussion, previous LE injuries, and the risk LE injury to the same previously injured limb (ipsilateral) or the opposite limb (contralateral).

METHODS

This retrospective study examined medical records from 110 concussed athletes and 110 matched controls for LE injuries in the 365 days before and after the concussion event. The effect of concussion on time to injury was assessed with a Cox proportional hazard model after adjusting for injury history. Fine and Gray subdistribution models assessed the cumulative risk of ipsilateral and contralateral injury by group.

RESULTS

Concussion was associated with an increased instantaneous relative risk of LE injury when adjusting for LE injury history [hazard ratio (HR) = 1.67, 95% confidence interval (CI) = 1.11-2.53], agreeing with previous results. Among individuals who had a history of LE injuries before the concussion event, a nonsignificant yet moderate effect of concussion on the instantaneous relative risk of ipsilateral injuries was found after adjusting for the competing risk of contralateral injuries and censored values (HR = 1.85, 95% CI = 0.76-4.46).

CONCLUSIONS

This study provides independent confirmation of previous studies, reporting an association between concussion and LE injury risk. Furthermore, this study suggests that future large-scale studies should consider the competing risk of ipsilateral, contralateral, and new injuries in populations with an injury history.

The effect of concussion on batting performance of major league baseball players

Purpose

Previous investigations into concussions' effects on Major League Baseball (MLB) players suggested that concussion negatively impacts traditional measures of batting performance. This study examined whether post-concussion batting performance, as measured by traditional, plate discipline, and batted ball statistics, in MLB players was worse than other post-injury performance.

Subjects and methods

MLB players with concussion from 2008 to 2014 were identified. Concussion was defined by placement on the disabled list or missing games due to concussion, post-concussive syndrome, or head trauma. Injuries causing players to be put on the disabled list were matched by age, position, and injury duration to serve as controls. Mixed effects models were used to estimate concussion's influence after adjusting for potential confounders. The primary study outcome measurements were: traditional (eg, average), plate discipline (eg, swing-at-strike rate), and batted ball (eg, ground ball percentage) statistics.

Results

There were 85 concussed players and 212 controls included in the analyses. There was no significant difference in performance between concussed players and controls. However, concussed players started at a lower level of performance pre-event than the controls, striking out a 9.2% rate vs 8.2% (P=0.042) with an isolated power of 0.075 vs 0.082 (P=0.035). For concussed players, traditional batting statistics decreased before plate discipline metrics.

Conclusion

MLB players' performance was lower after return from concussion, but no more than after return from other injuries. The decreased performance prior to concussion suggests that concussion-related performance declines may not be due exclusively to concussion and perhaps point to risk factors predisposing to concussion.

Sensorimotor and Physiological Indicators of Impairment in Mild Traumatic Brain Injury: A Meta-Analysis

OBJECTIVE

To systematically review the literature with meta-analysis to determine whether persistence of sensorimotor or physiological impairment exists between 4 weeks to 6 months post mild traumatic brain injury (mTBI), and assign level of evidence to findings.

METHOD

The databases PubMed, pscyINFO, SPORTdiscus, Medline, CINAHL and Embase were searched from inception to November 2016 using a priori inclusion criteria. Critical appraisal was performed, and an evidence matrix established level of evidence. Meta-analysis of pooled results identified standardized mean difference (SMD) and 95% confidence intervals (95% CI) between mTBI and healthy controls for a variety of physiological and sensorimotor indicators.

RESULTS

Eighteen eligible articles, with a mean quality score of 15.67 (SD = 2.33) were included in the final review. Meta-analysis of center of motion variable; maximal mediolateral center of motion/center of pressure separation distance SMD [95% CI] approached significance at (-0.42 [-0.84, -0.00], I² = 0%) for dual task, level walking indicating a potential reduction in maximal mediolateral excursion during gait in the mTBI group compared to healthy controls. Significantly reduced variability in the standard deviation of heart beat intervals was observed in the mTBI group (-0.51 [-0.74, -0.28], I² = 0%). Overall, significant group differences in 36 sensorimotor and physiological variables (eg, balance, gait velocity and motion analysis outcomes, various oculomotor tasks, as well as heart rate variability frequency domains) were identified.

CONCLUSION

Findings demonstrate that persistence of sensorimotor and physiological changes beyond expected recovery times following subacute mTBI in an adult population is possible. These findings have implications for post-injury assessment and management.

Alterations in dual-task walking persist two months after mild traumatic brain injury in young adults

Objectives

To compare dual-task performance involving different cognitive-locomotor combinations between healthy controls and participants with sub-acute mild traumatic brain injury (mTBI) and to correlate dual-task performances to history of prior head injuries.

Methods

Eighteen participants having recently sustained mTBI and 15 controls performed nine dual-tasks combining locomotor (level-walking, narrow obstacle, deep obstacle) and cognitive (Stroop task, Verbal fluency, Counting backwards) tasks. Previous history of concussion was also investigated.

Results

Slower gait speeds were observed in the mTBI group compared to controls during both single and dual-tasks. Longer response times to cognitive tasks in the mTBI group further suggested the presence of residual impairments two months following injury. No combination of dual-task was more sensitive. Correlations were observed between history of mTBI and several measures of dual-task performance, underlying the need to further consider the effects of multiple injuries in relation to dual-task walking.

Conclusion

Dual-tasks using simultaneously locomotor and cognitive functions represent an ecological way for clinicians to detect residual, but subtle, alterations post-mTBI. History of previous mTBI needs to be considered as a personal characteristic which may influence dual-task walking performance.

Detecting gait abnormalities after concussion or mild traumatic brain injury: A systematic review of single-task, dual-task, and complex gait

BACKGROUND

While a growing number of studies have investigated the effects of concussion or mild traumatic brain injury (mTBI) on gait, many studies use different experimental paradigms and outcome measures. The path for translating experimental studies for objective clinical assessments of gait is unclear.

RESEARCH QUESTION

This review asked 2 questions: 1) is gait abnormal after concussion/mTBI, and 2) what gait paradigms (single-task, dual-task, complex gait) detect abnormalities after concussion.

METHODS

Data sources included MEDLINE/PubMed, Scopus, Web of Science, and Cumulative Index to Nursing and Allied Health Literature (CINAHL) accessed on March 14, 2017. Original research articles reporting gait outcomes in people with concussion or mTBI were included. Studies of moderate, severe, or unspecified TBI, and studies without a comparator were excluded.

RESULTS

After screening 233 articles, 38 studies were included and assigned to one or more sections based on the protocol and reported outcomes. Twenty-six articles reported single-task simple gait outcomes, 24 reported dual-task simple gait outcomes, 21 reported single-task complex gait outcomes, and 10 reported dual-task complex gait outcomes.

SIGNIFICANCE

Overall, this review provides evidence for two conclusions: 1) gait is abnormal acutely after concussion/mTBI but generally resolves over time; and 2) the inconsistency of findings, small sample sizes, and small number of studies examining homogenous measures at the same time-period post-concussion highlight the need for replication across independent populations and investigators. Future research should concentrate on dual-task and complex gait tasks, as they showed promise for detecting abnormal locomotor function outside of the acute timeframe. Additionally, studies should provide detailed demographic and clinical characteristics to enable more refined comparisons across studies.

Effects of concussions on visually guided motor actions: A literature review

Athletes must be able to successfully navigate the soccer pitch or hockey rink to win the game, requiring maximal cognitive resources to successfully compete. Concussions potentially deplete these resources, and the long-term impact of concussions on an individual's goal-directed visually guided behavior continues to elude the scientific community. While the acute effects on cognition and the motor system have been elucidated elsewhere, long-term effects on performance have been less clear. Additionally, most investigations into long-term postinjury motor behaviors have focused on balance and gait, with little focus on functional upper extremity movements. These arm movements require both cognitive and motor functions to successfully complete the task, such as visually guided reaching, and have received little attention. This review examines the current state of the literature to date on the long-term effects of concussions on cognitive and motor deficits affecting visuomotor behavior.

Dual-Task Assessment Protocols in Concussion Assessment: A Systematic Literature Review

Study Design Systematic review. Background When assessed in isolation, balance and neurocognitive testing may not be sufficiently responsive to capture changes that occur with concussion. Normal daily activities require simultaneous cognitive and physical demands. Therefore, a dual-task assessment paradigm should be considered to identify performance deficits. Objectives To evaluate the literature and to identify dual-task testing protocols associated with changes in gait after concussion. Methods A systematic review of articles of individuals with concussion who underwent dual-task testing with a combination of motor and cognitive tasks was conducted. The AMED, CINAHL, Embase, PsycINFO, PubMed, Scopus, SPORTDiscus, and Web of Science databases and gray literature were searched from inception to January 29, 2017. Title and abstract, full-text, and quality review and data abstraction were performed by 2 independent reviewers. Results Twenty-four articles met the inclusion criteria. Eleven articles reported decreased gait velocity and increased medial-lateral displacement for individuals with concussion during dual-task conditions. Overall, included articles were of poor to moderate methodological quality. Fifteen articles used the same participants and data sets, creating a threat to validity and limiting the ability to make conclusions. Conclusion A deterioration in gait performance during dual-task testing is present among people with concussion. Specific recommendations for the use of a dual-task protocol to assess individuals with suspected concussion injury in a clinical setting have yet to be determined. J Orthop Sports Phys Ther 2018;48(2):87-103. Epub 7 Nov 2017. doi:10.2519/jospt.2018.7432.

Reduced P3b brain response during sustained visual attention is associated with remote blast mTBI and current PTSD in U.S. military veterans

Approximately 275,000 American service members deployed to Iraq or Afghanistan have sustained a mild traumatic brain injury (mTBI), with 75% of these incidents involving an explosive blast. Combat-related mTBI is frequently associated with comorbid mental health disorders, especially posttraumatic stress disorder (PTSD). Attention problems, including sustained attention, are common cognitive complaints of veterans with TBI and PTSD. The present study sought to examine neural correlates of sustained attention in veterans with blast mTBI and/or current PTSD. In 124 veterans of Operations Enduring and Iraqi Freedom (OEF/OIF), we examined event-related potentials (ERPs) elicited by targets and non-targets during performance of a degraded-stimulus continuous performance task (DS-CPT). Four groups, consisting of veterans with blast-related mTBI only, current PTSD only, both blast mTBI and PTSD, and a control group, were studied. Compared to all other groups, blast mTBI only participants were more likely to respond regardless of stimulus type during the DS-CPT. During target detection, the three mTBI/PTSD groups showed reduced amplitude of the P3b (i.e., P300) ERP at Pz compared to the control group. P3b of the three affected groups did not differ from each other. These results suggest that parietal P3b amplitude reduction during target detection in the DS-CPT task may be an index of brain pathology after combat trauma, yet the diminished brain response fails to differentiate independent effects of blast-related mTBI or severity of PTSD symptomatology.

Evidence of a conservative gait strategy in athletes with a history of concussions

BACKGROUND

A history of 3 or more concussions is frequently associated with numerous short- and long-term neuropathologies. Impairments in postural control are a known acute consequence of concussion; however, limited evidence exists on the effects of multiple concussions on gait. The purpose of this study was to assess gait stepping characteristics in collegiate aged student-athletes based on concussion history.

METHODS

There were 63 participants divided into 3 even groups based on concussion history: ≥3 concussions, 1-2 concussions, and 0 concussion. All participants completed 10 trials of gait on a 4.9 m instrumented walkway. The dependent variables of interest included both gait stepping characteristics (step velocity, length, and width, double support time, and the percentage of the gait cycle in stance) and coefficient of variability (CoV) measures (step length, time, and width). The gait stepping characteristics were compared first with a MANOVA with follow-up 1-way ANOVAs and Tukey post hoc tests as appropriate. The CoV measures were compared with 1-way ANOVAs and Tukey post hoc tests.

RESULTS

There were main effects for group for step velocity, length, width, and double support time. Overall, the 0 concussion group displayed typical healthy young gait parameters and performed significantly better than either concussion group. The 0 concussion group had a significantly greater step length CoV, but there were no differences in the step time or width CoV.

CONCLUSION

This finding provides evidence of subtle impairments in postural control during gait among individuals with prior history of concussion which could be an early indicator of future neurological deficiencies. The limited difference in the variability measures is consistent with prior static stance studies and could suggest the individuals constrain their motor systems to reduce variability. Taken together, these findings suggest a conservative gait strategy which is adopted by individuals with a history of concussions.

Postural control deficits identify lingering post-concussion neurological deficits

Concussion, or mild traumatic brain injury, incidence rates have reached epidemic levels and impaired postural control is a cardinal symptom. The purpose of this review is to provide an overview of the linear and non-linear assessments of post-concussion postural control. The current acute evaluation for concussion utilizes the subjective balance error scoring system (BESS) to assess postural control. While the sensitivity of the overall test battery is high, the sensitivity of the BESS is unacceptably low and, with repeat administration, is unable to accurately identify recovery. Sophisticated measures of postural control, utilizing traditional linear assessments, have identified impairments in postural control well beyond BESS recovery. Both assessments of quiet stance and gait have identified lingering impairments for at least 1 month post-concussion. Recently, the application of non-linear metrics to concussion recovery have begun to receive limited attention with the most commonly utilized metric being approximate entropy (ApEn). ApEn, most commonly in the medial-lateral plane, has successfully identified impaired postural control in the acute post-concussion timeframe even when linear assessments of instrumented measures are equivalent to healthy pre-injury values; unfortunately these studies have not gone beyond the acute phase of recovery. One study has identified lingering deficits in postural control, utilizing Shannon and Renyi entropy metrics, which persist at least through clinical recovery and return to participation. Finally, limited evidence from two studies suggest that individuals with a previous history of a single concussion, even months or years prior, may display altered ApEn metrics. Overall, non-linear metrics provide a fertile area for future study to further the understanding of postural control impairments acutely post-concussion and address the current challenge of sensitive identification of recovery.

Using dual task walking as an aid to assess executive dysfunction ecologically in neurological populations: A narrative review

Within rehabilitation, clinical assessment plays a crucial role in diagnosis, prognostication and making decisions about return to function. The ecological validity of the assessment of executive dysfunction has become a particular focus in neuropsychology and is gaining interest in mobility research and neurological rehabilitation of acquired brain injury or degenerative neurological diseases. In this narrative review, we look at how the task of walking and the inseparable cognitive demands and interference of the surrounding environment are exploited in dual task walking (DTW) paradigms to expose executive dysfunction. While quite a number of studies and reviews have recently focused on the utility of DTW for gait assessment, particularly to assess fall risk, very little consideration has been given to the level of ecological validity required. This paper directly addresses this issue with discussion of evidence and lacunas related to task, personal and technological factors that should be addressed in order to exploit fully DTW paradigms as an ecological assessment tool.

Neural substrates underlying the passive observation and active control of translational egomotion

Moving or static obstacles often get in the way while walking in daily life. Avoiding obstacles involves both perceptual processing of motion information and controlling appropriate defensive movements. Several higher-level motion areas, including the ventral intraparietal area (VIP), medial superior temporal area, parieto-insular vestibular cortex (PIVC), areas V6 and V6A, and cingulate sulcus visual area, have been identified in humans by passive viewing of optic flow patterns that simulate egomotion and object motion. However, the roles of these areas in the active control of egomotion in the real world remain unclear. Here, we used functional magnetic resonance imaging (fMRI) to map the neural substrates underlying the passive observation and active control of translational egomotion in humans. A wide-field virtual reality environment simulated a daily scenario where doors randomly swing outward while walking in a hallway. The stimuli of door-dodging events were essentially the same in two event-related fMRI experiments, which compared passive and active dodges in response to swinging doors. Passive dodges were controlled by a computer program, while active dodges were controlled by the subject. Passive dodges activated several higher-level areas distributed across three dorsal motion streams in the temporal, parietal, and cingulate cortex. Active dodges most strongly activated the temporal-vestibular stream, with peak activation located in the right PIVC. Other higher-level motion areas including VIP showed weaker to no activation in active dodges. These results suggest that PIVC plays an active role in sensing and guiding translational egomotion that moves an observer aside from impending obstacles.

Visuomotor deficits during locomotion in previously concussed athletes 30 or more days following return to play

Current protocols for returning athletes to play (RTP) center around resolution of physical symptoms of concussion. However, recent research has identified that balance and cognitive deficits persist beyond physical symptom recovery. Protocols that involve testing dynamic balance and visuomotor integration have been recommended as potential tools for better understanding of length of impairment following concussion. A dynamic, visuomotor paradigm was undertaken in the current study to assess decision making in athletes who had sustained a concussion >30 days before study participation and had been cleared to RTP (N = 10). Two obstacles created a gap that varied between 0.6 and 1.8× participants' individual shoulder width in open space. Participants made decisions to navigate through or deviate around the gap created by the two obstacles. The results revealed that previously concussed athletes were highly variable in their decision making and demonstrated variable Medial‐Lateral (ML) center of mass (COM) control when approaching the obstacles, when compared with nonconcussed, age‐matched controls. As such, they showed poor visuomotor control and decision making, as well as poor dynamic stability compared to controls. Visuomotor deficits were persistent in the sample of previously concussed individuals, well beyond deficits identified by current RTP standards. This study suggests that dynamic, visuomotor integration tasks may be of benefit to increase rigor in RTP protocols and increase safety of athletes returning to sport.

Cognitive recovery from concussion does not coincide with physical symptom recovery. Deficits of concussion persist well beyond the believed 30 days of recovery. Visuomotor paradigms in combination with balance control can determine concussion recovery.

Acute and longitudinal changes in motor cortex function following mild traumatic brain injury

PRIMARY OBJECTIVE

To evaluate excitability and inhibition of the motor cortex acutely and longitudinally following mild traumatic brain injury (mTBI).

RESEARCH DESIGN

A longitudinal paired case-control design was used to examine cortical excitability and inhibition in 15 adults who had sustained an mTBI (mean age = 20.8 ± 1.2 years) and 15 matched control participants (mean age = 21.1 ± 1.3 years).

METHODS AND PROCEDURES

Participants visited the lab within 72 hours of injury and again at 1, 2, 4 and 8 weeks post-injury. During each visit, transcranial magnetic stimulation was used to examine resting motor threshold (RMT), motor evoked potential peak-to-peak amplitude (MEPamp) and cortical silent period (CSP) duration of the first dorsal interosseous muscle.

MAIN OUTCOMES AND RESULTS

There were no differences between groups in RMT (p = 0.10) or MEPamp (p = 0.22) at 72 hours post-injury or across the 2-month testing period (p ≥ 0.68), indicating similar cortical excitability. However, the CSP duration was higher in individuals with mTBI, indicating greater intra-cortical inhibition compared with the control group at 72 hours post-injury (p = 0.03) and throughout the 2 months of recovery (p = 0.009).

CONCLUSIONS

mTBI appeared to have little effect on cortical excitability, but an acute and long-lasting effect on intra-cortical inhibition.

Are divided attention tasks useful in the assessment and management of sport-related concussion?

This article is a systematic review of the literature on divided attention assessment inclusive of a cognitive and motor task (balance or gait) for use in concussion management. The systematic review drew from published papers listed in PubMed, MEDLINE, EMBASE and CINAHL databases. The search identified 19 empirical research papers meeting the inclusion criteria. Study results were considered for the psychometric properties of the paradigms, the influence of divided attention on measures of cognition and postural control and the comparison of divided attention task outcomes between individuals with concussion and healthy controls (all samples were age 17 years or older). The review highlights that the reliability of the tasks under a divided attention paradigm presented ranges from low to high (ICC: 0.1-0.9); however, only 3/19 articles included psychometric information. Response times are greater, gait strategies are less efficient, and postural control deficits are greater in concussed participants compared with healthy controls both immediately and for some period following concussive injury, specifically under divided attention conditions. Dual task assessments in some cases were more reliable than single task assessments and may be better able to detect lingering effects following concussion. Few of the studies have been replicated and applied across various age groups. A key limitation of these studies is that many include laboratory and time-intensive measures. Future research is needed to refine a time and cost efficient divided attention assessment paradigm, and more work is needed in younger (pre-teens) populations where the application may be of greatest utility.

Concussion induces gait inter-joint coordination variability under conditions of divided attention and obstacle crossing

This study investigated the effect of concussion on the pattern and variability of inter-joint coordination during level walking (Level), obstacle crossing (OB), and walking with a concurrent cognitive test (ATT). Gait analyses of 23 concussed and 23 matched healthy adults were performed. Continuous relative phase (CRP), derived from phase angles of two adjacent joints, was used to assess inter-joint coordination. Cross-correlation measures and root-mean-square (RMS) differences were used to compare CRP patterns of the Level condition to those of OB and ATT conditions, respectively. Deviation phase (DP) was used to evaluate variability of inter-joint coordination for each task. For hip-knee and knee-ankle CRP patterns, RMS differences between OB and Level and between ATT and Level in concussed subjects were significantly greater than those of healthy adults. No significant group differences were detected for the cross-correlation measures of hip-knee and knee-ankle CRP patterns. In stance phase, a significant task effect on DP values was detected in hip-knee inter-joint coordination. For knee-ankle inter-joint coordination, concussed subjects showed significantly greater DP values than healthy controls during OB and ATT. In swing phase, concussed individuals showed greater DP values in hip-knee and knee-ankle inter-joint coordination compared to healthy controls. The findings suggest that the ability to modulate inter-joint coordination patterns when accommodating to gait perturbations is affected by concussion.

Returning service members to duty following mild traumatic brain injury: exploring the use of dual-task and multitask assessment methods

Within the last decade, more than 220,000 service members have sustained traumatic brain injury (TBI) in support of military operations in Iraq and Afghanistan. Mild TBI may result in subtle cognitive and sensorimotor deficits that adversely affect warfighter performance, creating significant challenges for service members, commanders, and clinicians. In recent conflicts, physical therapists and occupational therapists have played an important role in evaluating service member readiness to return to duty (RTD), incorporating research and best practices from the sports concussion literature. Because premorbid (baseline) performance metrics are not typically available for deployed service members as for athletes, clinicians commonly determine duty readiness based upon the absence of postconcussive symptoms and return to "normal" performance on clinical assessments not yet validated in the military population. Although practices described in the sports concussion literature guide "return-to-play" determinations, resolution of symptoms or improvement of isolated impairments may be inadequate to predict readiness in a military operational environment. Existing clinical metrics informing RTD decision making are limited because they fail to emphasize functional, warrior task demands and they lack versatility to assess the effects of comorbid deficits. Recently, a number of complex task-oriented RTD approaches have emerged from Department of Defense laboratory and clinical settings to address this gap. Immersive virtual reality environments, field-based scenario-driven assessment programs, and militarized dual-task and multitask-based approaches have all been proposed for the evaluation of sensorimotor and cognitive function following TBI. There remains a need for clinically feasible assessment methods that can be used to verify functional performance and operational competence in a variety of practice settings. Complex and ecologically valid assessment techniques incorporating dual-task and multitask methods may prove useful in validating return-to-activity requirements in civilian and military populations.

Mapping multisensory parietal face and body areas in humans

Detection and avoidance of impending obstacles is crucial to preventing head and body injuries in daily life. To safely avoid obstacles, locations of objects approaching the body surface are usually detected via the visual system and then used by the motor system to guide defensive movements. Mediating between visual input and motor output, the posterior parietal cortex plays an important role in integrating multisensory information in peripersonal space. We used functional MRI to map parietal areas that see and feel multisensory stimuli near or on the face and body. Tactile experiments using full-body air-puff stimulation suits revealed somatotopic areas of the face and multiple body parts forming a higher-level homunculus in the superior posterior parietal cortex. Visual experiments using wide-field looming stimuli revealed retinotopic maps that overlap with the parietal face and body areas in the postcentral sulcus at the most anterior border of the dorsal visual pathway. Starting at the parietal face area and moving medially and posteriorly into the lower-body areas, the median of visual polar-angle representations in these somatotopic areas gradually shifts from near the horizontal meridian into the lower visual field. These results suggest the parietal face and body areas fuse multisensory information in peripersonal space to guard an individual from head to toe.

The use of the dual-task paradigm in detecting gait performance deficits following a sports-related concussion: a systematic review and meta-analysis

OBJECTIVES

The purpose of this systematic review was to determine the viability of the dual-task paradigm in the evaluation of a sports-related concussion.

DESIGN

Systematic review and meta-analysis.

METHODS

Eight electronic databases were searched from their inception until the 11(th) of April 2011. Studies were grouped according to their reported gait performance variables and their time(s) of assessment(s). Raw mean differences (MD) and 95% confidence intervals (CI) were calculated based on raw means and standard deviations for gait performance measures in both single- and dual-task conditions. Dual-task deficits were pooled using a random effects model and heterogeneity (I(2)) between studies was assessed.

RESULTS

Ten studies representing a total sample of 168 concussed and 167 matched (age and gender) non-concussed participants met the inclusion criteria. Meta-analysis demonstrated that dual-task performance deficits were detected (p<0.05) in the concussed group for gait velocity (GV) (MD=-0.133; 95% CI -0.197, -0.069) and range of motion of the centre of mass in the coronal plane (ML-ROM) (MD=0.007; 95% CI 0.002, 0.011), but not in the non-concussed group; GV (MD=-0.048; 95% CI -0.101, 0.006), ML-ROM (MD=0.002; 95% CI -0.001, 0.005).

CONCLUSIONS

The results of this study indicate that GV and ML-ROM are sensitive measures of dual-task related changes in concussed patients and should be considered as part of a comprehensive assessment for a sports-related concussion.

Can a clinical test of reaction time predict a functional head-protective response?

PURPOSE

Reaction time is commonly prolonged after a sport-related concussion. Besides being a marker for injury, a rapid reaction time is necessary for protective maneuvers that can reduce the frequency and severity of additional head impacts. The purpose of this study was to determine whether a clinical test of simple visuomotor reaction time predicted the time taken to raise the hands to protect the head from a rapidly approaching ball.

METHODS

Twenty-six healthy adult participants recruited from campus and community recreation and exercise facilities completed two experimental protocols during a single session: a manual visuomotor simple reaction time test (RT(clin)) and a sport-related head-protective response (RT(sprt)). RT(clin) measured the time required to catch a thin vertically oriented device on its release by the tester and was calculated from the distance the device fell before being arrested. RT(sprt) measured the time required to raise the hands from waist level to block a foam tennis ball fired toward the subject's face from an air cannon and was determined using an optoelectronic camera system. A correlation coefficient was calculated between RT(clin) and RT(sprt), with linear regression used to assess for effect modification by other covariates.

RESULTS

A strong positive correlation was found between RT(clin) and RT(sprt) (r = 0.725, P < 0.001) independent of age, gender, height, or weight.

CONCLUSIONS

RT(clin) is predictive of a functional sport-related head-protective response. To our knowledge, this is the first demonstration of a clinical test predicting the ability to protect the head in a simulated sport environment. This correlation with a functional head-protective response is a relevant consideration for the potential use of RT(clin) as part of a multifaceted concussion assessment program.

The effects of attention capacity on dynamic balance control following concussion

The purpose of this study was to examine how individuals modulate attention in a gait/cognition dual task during a 4-week period following a concussion. Ten individuals suffering from a grade 2 concussion and 10 matched controls performed a single task of level walking, a seated auditory Stroop task and a simultaneous auditory Stroop and walking task. Reaction time and accuracy were measured from the Stroop task. Dynamic balance control during gait was measured by the interaction (displacement and velocity) between the center of mass (CoM) and center of pressure (CoP) in the coronal and sagittal planes. Concussed individuals shifted from conservative control of balance (shorter separation between CoM and CoP) immediately after injury to normal balance control over 28 days post-injury. Immediately after injury, correlations analyses using each subject on each testing day as a data point showed that there was a spectrum of deficient performance among concussed individuals on the first testing day. Within a testing session, deficiencies in reaction time of processing involved in the Stroop task were commonly seen with reduce dynamic balance control. However, the prioritization was not always towards the same task between trials. There were no correlations in the control group. Information provided in this study would enhance our understanding of the interaction between attention and gait following concussion.