Clinical Assessments of Balance in Adults with Concussion: An Update.

Postural instability is a cardinal indicator of concussion. Assessments of the postural control system range from clinical to laboratory tests that assess the balance of the individual. In a previous article regarding clinical assessment of balance in adults with concussion, we reviewed the importance of balance as a component in concussion evaluations. The purpose of this review article is to update the information previously published in 2014. Since 2014, research has provided evidence for the incorporation of dynamic methods for evaluating balance postconcussion with particular emphasis on sensory system integration and dual tasking. Therefore, this review will examine the current state of knowledge on how concussion injuries affect postural control, advancements in evaluating balance postconcussion, such as novel eye-tracking techniques, and current recommendations for best practices for balance assessment.

Constraining eye movement in individuals with Parkinson's disease during walking turns.

Walking and turning is a movement that places individuals with Parkinson's disease (PD) at increased risk for fall-related injury. However, turning is an essential movement in activities of daily living, making up to 45 % of the total steps taken in a given day. Hypotheses regarding how turning is controlled suggest an essential role of anticipatory eye movements to provide feedforward information for body coordination. However, little research has investigated control of turning in individuals with PD with specific consideration for eye movements. The purpose of this study was to examine eye movement behavior and body segment coordination in individuals with PD during walking turns. Three experimental groups, a group of individuals with PD, a group of healthy young adults (YAC), and a group of healthy older adults (OAC), performed walking and turning tasks under two visual conditions: free gaze and fixed gaze. Whole-body motion capture and eye tracking characterized body segment coordination and eye movement behavior during walking trials. Statistical analysis revealed significant main effects of group (PD, YAC, and OAC) and visual condition (free and fixed gaze) on timing of segment rotation and horizontal eye movement. Within group comparisons, revealed timing of eye and head movement was significantly different between the free and fixed gaze conditions for YAC (p < 0.001) and OAC (p < 0.05), but not for the PD group (p > 0.05). In addition, while intersegment timings (reflecting segment coordination) were significantly different for YAC and OAC during free gaze (p < 0.05), they were not significantly different in PD. These results suggest individuals with PD do not make anticipatory eye and head movements ahead of turning and that this may result in altered segment coordination during turning. As such, eye movements may be an important addition to training programs for those with PD, possibly promoting better coordination during turning and potentially reducing the risk of falls.

Assessment of oculomotor control and balance post-concussion: a preliminary study for a novel approach to concussion management.

PRIMARY OBJECTIVE: Balance disturbances occur in ∼30% of concussion injuries, with vestibular dysfunction reported as the main contributor. However, few have studied oculomotor control post-concussion to assess vestibular dysfunction. RESEARCH DESIGN: The current research measured the differences in oculomotor control between athletes post-concussion (PC) and athletes without concussion (NC) during an active balance control task. METHODS: Nine PC and nine NC athletes wore a monocular eye tracking device, while balance tests were performed using the Nintendo WiiFit® soccer heading game. Average game scores, eye deviations from centre (Gaze Deviations) and gaze fixation (Percentage Time on Centre) were measured. RESULTS: PC made significantly greater Gaze Deviations from centre compared to NC (p < 0.001), however Percentage Time on Centre and game scores were not significantly different between groups. Correlations between gaze and balance within groups revealed a significant positive correlation in NC, while a significant negative correlation in PC. CONCLUSIONS: Results from this exploratory examination of oculomotor behaviour post-concussion revealed significant differences in gaze stability between athletes with a concussion and those without, suggesting vestibular involvement post-concussion. Assessment of oculomotor control during balance activities may provide further insight into dysfunction of the vestibular system following a concussion injury.

Clinical assessment of balance in adults with concussion.

Balance is a key component to the assessment of concussion injury; however, the efficacies of clinical tests used are currently under debate. It is questionable whether currently accepted methods of standing balance assessment quantify balance disturbances sufficiently to support decisions on recovery and return to play. Recent evidence of balance abnormalities postconcussion that linger beyond the typical 3- to 5-day recovery period support arguments that currently available standing balance tests are not sensitive enough to determine recovery of function. This article discusses the current clinical tests used in the assessment of concussion in adults and their limitations and the evidence supporting continued balance dysfunction. Implications for the future of balance assessment in concussed adults and recommendations to clinicians for best practices are presented.

Constraining eye movement when redirecting walking trajectories alters turning control in healthy young adults.

Humans use a specific steering synergy, where the eyes and head lead rotation to the new direction, when executing a turn or change in direction. Increasing evidence suggests that eye movement is critical for turning control and that when the eyes are constrained, or participants have difficulties making eye movements, steering control is disrupted. The purpose of the current study was to extend previous research regarding eye movements and steering control to a functional walking and turning task. This study investigated eye, head, trunk, and pelvis kinematics of healthy young adults during a 90° redirection of walking trajectory under two visual conditions: Free Gaze (the eyes were allowed to move naturally in the environment), and Fixed Gaze (participants were required to fixate the eyes on a target in front). Results revealed significant differences in eye, head, and trunk coordination between Free Gaze and Fixed Gaze conditions (p < 0.001). During Free Gaze, the eyes led reorientation followed by the head and trunk. Intersegment timings between the eyes, head, and trunk were significantly different (p < 0.05). In contrast, during Fixed Gaze, the segments moved together with no significant differences between segment onset times. In addition, the sequence of segment rotation during Fixed Gaze suggested a bottom-up postural perturbation control strategy in place of top-down steering control seen in Free Gaze. The results of this study support the hypothesis that eye movement is critical for the release of the steering synergy for turning control.

Visual Cues Promote Head First Strategies During Walking Turns in Individuals With Parkinson's Disease.

Anticipatory eye movement promotes cranio-caudal sequencing during walking turns. Clinical groups, such as Parkinson's disease (PD), do not produce anticipatory eye movements, leading to increased risk of falls. Visual cues may promote anticipatory eye movement by guiding the eyes into the turn. This study examined if visual cues could train anticipatory eye movement. Ten neurotypical young adults and 6 adults with PD completed three blocks of walking trials. Trials were blocked by visual condition: non-cued baseline turns (5 trials), visually cued turns (10 trials), and non-cued post turns (5 trials). A Delsys Trigno (Delsys, Boston, MA) recorded horizontal saccades at 1024 Hz via electrooculography (EOG). Two Optotrak cameras (Northern Digital Inc., ON, Canada) captured body segment kinematics at 120 Hz. Initiation of segment rotation with respect to ipsilateral foot contact (IFC1) prior to the turn was calculated. Neurotypical young adults (NYA) produced typical cranio-caudal rotation sequences during walking turns. Eyes led (407 ms prior to IFC1), followed by the head (50 ms prior to IFC1), then trunk and pelvis. In contrast, PD produced no anticipatory eye or segment movement at baseline. During pre-trials the eyes moved 96 ms after IFC1 and segment movement was initiated by the pelvis followed by trunk and head segments. After visual cue training however, PD produced anticipatory eye movements 161 ms prior to IFC1, followed by the head 88 ms following IFC1 but ahead of trunk and pelvis onset. These results suggest visual cues assist in producing cranio-caudal control during walking turns in PD.

Smooth Pursuit and Saccades after Sport-Related Concussion.

Smooth pursuit eye movements (SPEMs) and saccadic eye movements are both commonly impaired following sport-related concussion (SRC). Typical oculomotor assessments measure individual eye movements in a series of restrictive tests designed to isolate features such as response times. These measures lack ecological validity for athletes because athletes are adept at simple tasks designed for the general population. Yet, because eye movement metrics are sensitive and well-characterized neuroanatomically, it would be valuable to test whether athletes exhibit abnormal eye movements with more challenging tasks. To address this gap in knowledge, we collected eye-tracking data during a sport-like task to gain insight on gaze behavior during active self-motion. SPEMs and saccadic eye movements were recorded during a sport-like visual task within 24-48 h following SRC. Thirty-six Division I student-athletes were divided into SRC and control (CON) groups. All participants completed two blocks of the Wii Fit© soccer heading game (WF) while wearing a monocular infrared eye tracker. Eye movement classification systems quantified saccadic amplitude (SA), velocity (SV), and count (SC); as well as SPEM velocity (SPV) and amplitude (SPA). Separate Mann-Whitney U tests evaluated SPA and SC and found no significant effects (SPA, p = 0.11; SC, p = 0.10). A multi-variate analysis of variance (MANOVA) for remaining variables revealed SPV was significantly greater in CON (p < 0.05), but the SRC group had greater SA and SV (p < 0.05). These findings suggest that during a sport-like task, to maintain foveation SRC subjects used larger amplitude, faster saccades, but exhibited slower SPEMs. Measuring oculomotor function during ecologically valid, sport-like tasks may serve as a concussion biomarker and provide insights into eye movement control after SRC.

Deep brain stimulation enhances movement complexity during gait in individuals with Parkinson's disease.

Deep brain stimulation (DBS) is associated with substantial improvements in motor symptoms of PD. Emerging evidence has suggested that nonlinear measures of complexity may provide greater insight into the efficacy of anti-PD treatments. This study investigated sample entropy and complexity index values in individuals with PD when DBS was OFF compared to ON. Five individuals with PD using DBS performed a four-minute treadmill walking task while 3D kinematics were collected over two periods of 30 s. Participants were tested in the DBS-ON and DBS-OFF conditions. Sample entropy (SE) and complexity index (CI) values were calculated for ankle, knee and hip joint angles. Paired samples t-tests were used to compare mean SE and CI values between the DBS-OFF and DBS-ON conditions, respectively. No differences in SE or CI were observed between the DBS-ON and DBS-OFF conditions at the ankle. At the knee, the DBS-ON was associated with greater SE and CI values than the DBS-OFF condition. At the hip, DBS-ON was associated with greater SE and CI values than the DBS-OFF condition. DBS enhances complexity of movement at the hip and knee joints while complexity at the ankle joint is not significantly altered. Greater complexity of knee and hip joint motion may represent increased adaptability and a greater number of available strategies to complete the gait task.

The relationship between postural stability and virtual environment adaptation.

Currently little is known about how adaptive responses to virtual environments are different between individuals who experience sickness related symptoms and those who do not. It is believed that sensory interactions between visually perceived self-motion and static inertial cues from vestibular and/or proprioceptive sensory systems contribute to the development of adaptation symptoms. The aim of this study was to evaluate the relationship between adaptation symptoms and postural stability in a virtual environment (VE) driving simulator. In addition, the role of sensory interaction was assessed using direct electrical stimulation techniques of the vestibular and cutaneous sensory systems. Posture performance was measured using centre of pressure measures of single leg stance tests during eyes open and eyes closed conditions. Correlation analysis of postural measures and symptom scores were conducted, as well as analysis of variance of posture performance between SICK and WELL individuals. Results indicate that posture stability is negatively correlated to symptom reporting. WELL individuals displayed the greatest decrease in postural stability during eyes open single leg stance following VE simulation. Application of a secondary sensory stimulation (vestibular or cutaneous) resulted in increased visual dependency for postural control following simulation. Combined, these results suggest that sensory interactions drive postural changes that are observed following VE simulation and are related to how visual information is used to control posture.

Kinematics and muscular responses to a ramp descent in the ACL deficient knee.

BACKGROUND AND PURPOSE: Descent of a ramp has been shown to induce large anterior shear forces on the knee joint. Compensatory muscle responses observed in individuals following an anterior cruciate ligament (ACL) injury are believed to be adopted for the purpose of reducing these forces at the knee, in the absence of the mechanical restraint previously provided by the ACL. As such, examining the kinematics and muscle responses of ACL deficient individuals during ramp descent may provide further insight into strategies used by this population to compensate for anterior shear forces at the knee. METHODS: Eight ACL deficient individuals were studied, in comparison to a healthy CONTROL group (N=8), during the descent of a 20 degrees ramp. Kinematics and electromyography were recorded for the injured lower limb of ACLD and matched limb of healthy control individuals. RESULTS: ACLD individuals produced altered knee kinematics at heel contact only. Knee motion through stance and swing were similar to CONTROL individuals. ACLD individuals produced significantly greater vastus lateralis and gastrocnemius total muscle activity, but decreased total biceps femoris activity. No significant differences were observed for the timing of peak muscle activity or the magnitude at this point between ACLD and CONTROL. DISCUSSION AND CONCLUSION: Greater total muscle activity of vastus lateralis implies that greater force contributions from this muscle were used by ACLD in comparison to CONTROL in response to the ramp. These observations reinforce that quadriceps avoidance is not used by ACLD individuals to reduce anterior shear forces at the knee joint. Rather, vastus lateralis may be used to reduce internal tibial rotation in extreme loading situations.

The effects of gaze stabilization on gait parameters in individuals with Parkinson's disease.

The purpose of this study was to examine the effects of gaze fixation on head stabilization and gait during straight over ground walking in individuals with Parkinson's disease (PD). Eight individuals with PD (Age: 62.3±8.1 years) volunteered for the study. Full body kinematic data were collected at 120Hz using a Vicon motion capture system. Two visual conditions were used to determine the effects of gaze fixation: FREE gaze and FIXED gaze. During FIXED gaze, participants were required to fixate on a still target 13m ahead. During FREE gaze, participants were free to visually scan the environment. Five straight walking trials were performed in each experimental condition for a total of ten walking trials. Head segment stabilization strategies as well as gait parameters were compared between conditions. Step width, step length, stride time, cadence, double support time, centre of mass (CoM) velocity and CoM medial-lateral deviation were calculated for two strides of each over ground walking trial. Comparisons of mean values and variability were made using repeated measures ANOVAs. Results revealed that maintaining a FIXED gaze had no significant effect on head stabilization strategies or gait parameters with the exception of a significant increase in step width variability (p=0.003). CoM velocity was not significantly different between FREE and FIXED gaze conditions (FREE: 1.17±0.20m/s; FIXED: 1.16±0.19m/s). CoM medial-lateral deviation was observed to be greater in FIXED (47.1±36.9cm) compared to FREE (26.9±15.1cm), though not significantly. These results suggest that gaze fixation to a target in front while walking increases step width variability and CoM M-L deviations indicative of reduced postural stability. This is an important consideration for use of visual cues to promote gait in PD.

Assessment of the Wii Basic Balance Test in measuring postural deficits post-concussion.

Background and Aim: To evaluate the Wii Basic Balance Test (WBBT), as a tool for detecting postural instability in athletes with concussions. Methods: Seventy-nine healthy physically active controls (NORM) (mean age 21.23 ± 1.78), and fifty-six athletes with concussions (CONC) (mean age 19.39 ± 2.145) participated in this study. All participants performed the Wii Basic Balance Test, which requires the participants to shift weight mediolaterally to maintain a red bar within a blue area denoted on the screen for three seconds during set levels of difficulty. CONC were included in the study within 24-48 hours of the initial concussion injury. Seven one-way ANOVAs assessed differences for each (1) Mean total number of WBBT Levels completed (TL), (2) Mean total seconds to complete all WBBT Level (TT), (3) Time to complete Level 1 (LI), (4) Time to complete Level 2 (L2), (5) Time to complete Level 3 (L3), (6) Time to complete Level 4 (L4), (7) Time to complete Level 5 (L5). Results: CONC completed significantly fewer Levels of the WBBT (p=0.032) when compared to NORM. Athletes with Concussions took a significantly longer time to complete LI (p=0.002) when compared to CONC. Post-hoc Chi-Square analysis determined a significantly greater (p=0.015) proportion (39%) of CONC successfully completed WBBT L5 when compared to the proportion (19%) of CONC. Follow up ROC curves revealed an Sn = 0.392 and an Sp = 0.821 for TL with a cutoff value of 4 levels, Sn=0.875 and an Sp = 0.253 for LI with a cutoff value of 4.4 seconds, and Sn = 0.804 and an Sp = 0.392 for those who successfully completed the WBBT L5. Conclusions: WBBT could be a low cost object method of assessing postural instability within 24-48 hours post-concussion. Relevance for patients: This data could provide health providers with an alternative method to measure the presence of postural instability post-concussion injury.

ASB clinical biomechanics award winner 2016: Assessment of gaze stability within 24-48hours post-concussion.

BACKGROUND: Approximately 90% of athletes with concussion experience a certain degree of visual system dysfunction immediately post-concussion. Of these abnormalities, gaze stability deficits are denoted as among the most common. Little research quantitatively explores these variables post-concussion. As such, the purpose of this study was to investigate and compare gaze stability between a control group of healthy non-injured athletes and a group of athletes with concussions 24-48hours post-injury. METHODS: Ten collegiate NCAA Division I athletes with concussions and ten healthy control collegiate athletes completed two trials of a sport-like antisaccade postural control task, the Wii Fit Soccer Heading Game. During play all participants were instructed to minimize gaze deviations away from a central fixed area. Athletes with concussions were assessed within 24-48 post-concussion while healthy control data were collected during pre-season athletic screening. Raw ocular point of gaze coordinates were tracked with a monocular eye tracking device (240Hz) and motion capture during the postural task to determine the instantaneous gaze coordinates. This data was exported and analyzed using a custom algorithm. Independent t-tests analyzed gaze resultant distance, prosaccade errors, mean vertical velocity, and mean horizontal velocity. FINDINGS: Athletes with concussions had significantly greater gaze resultant distance (p=0.006), prosaccade errors (p<0.001), and horizontal velocity (p=0.029) when compared to healthy controls. INTERPRETATION: These data suggest that athletes with concussions had less control of gaze during play of the Wii Fit Soccer Heading Game. This could indicate a gaze stability deficit via potentially reduced cortical inhibition that is present within 24-48hours post-concussion.

Relationship between the Romberg test and the Wii Fit basic balance test and cognition in athletes with concussion.

BACKGROUND: Approximately 30% of individuals with a sport-related concussion present with postural instability. Multiple clinical balance tests exist to diagnose postural instability; yet little is known about the potential relationship between these type of postural assessments and cognition post-concussion. AIM: The purpose of the current study was to assess the relationship between the Romberg test, the Wii Fit basic balance test (WBBT), and the composite scores on the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) test in a sample of athletes with concussions. METHODS: Fifty five post-concussed athletes (40 males) completed the Romberg test (RT) (-/+), the WBBT, and ImPACT test. WBBT performance was operationalized as the number of successfully completed trials (of 5 trials of increasing difficulty) within 30 seconds. Pearson's and point-biserial correlations examined univariate associations among the variables. RESULTS: The RT and WBBT were not significantly related (r = - 0.029, p = 0.832). The RT weakly correlated with ImPACT impairment scores (r = 0.26, p = 0.041), whereas WBBT the number of trials did not (r = - 0.20, p = 0.155). The RT scores were significantly correlated with ImPACT Visual Processing Speed Score (r = 0.27, p = 0.036) and Reaction Time score (r = 0.34, p = 0.006). In contrast, WBBT trials were significantly correlated with the ImPACT Visual Memory Score (r = - 0.41, p = 0.003). CONCLUSIONS: These results suggest that the WBBT and RT assess unique aspects of postural control. The RT may relate directly to single sensory cognitive and motor processing, while the WBBT may relate to multi-sensory visually driven cognitive and motor processing. RELEVANCE FOR PATIENTS: Clinical balance tests could point to different cognitive impairments post-concussion.

Is the size of the useful field of view affected by postural demands associated with standing and stepping?

The useful field of view (UFOV) is the visual area from which information is obtained at a brief glance. While studies have examined the effects of increased cognitive load on the visual field, no one has specifically looked at the effects of postural control or locomotor activity on the UFOV. The current study aimed to examine the effects of postural demand and locomotor activity on UFOV performance in healthy young adults. Eleven participants were tested on three modified UFOV tasks (central processing, peripheral processing, and divided-attention) while seated, standing, and stepping in place. Across all postural conditions, participants showed no difference in their central or peripheral processing. However, in the divided-attention task (reporting the letter in central vision and target location in peripheral vision amongst distracter items) a main effect of posture condition on peripheral target accuracy was found for targets at 57° of eccentricity (p=.037). The mean accuracy reduced from 80.5% (standing) to 74% (seated) to 56.3% (stepping). These findings show that postural demands do affect UFOV divided-attention performance. In particular, the size of the useful field of view significantly decreases when stepping. This finding has important implications for how the results of a UFOV test are used to evaluate the general size of the UFOV during varying activities, as the traditional seated test procedure may overestimate the size of the UFOV during locomotor activities.

Simulated visual field loss does not alter turning coordination in healthy young adults.

Turning, while walking, is an important component of adaptive locomotion. Current hypotheses regarding the motor control of body segment coordination during turning suggest heavy influence of visual information. The authors aimed to examine whether visual field impairment (central loss or peripheral loss) affects body segment coordination during walking turns in healthy young adults. No significant differences in the onset time of segments or intersegment coordination were observed because of visual field occlusion. These results suggest that healthy young adults can use visual information obtained from central and peripheral visual fields interchangeably, pointing to flexibility of visuomotor control in healthy young adults. Further study in populations with chronic visual impairment and those with turning difficulties are warranted.

Vision and falls: a multidisciplinary review of the contributions of visual impairment to falls among older adults.

Falls are a leading cause of mortality among older adults worldwide. With the increasing aging population, falls are rapidly becoming a public health concern. Numerous internal and external factors have been associated with an older adult's increased risk of falling. Most notably visual impairments are gaining recognition for their critical role in fall events, particularly related to trips, slips and falls due to environmental hazards. This review presents the issue of vision and falls from a multidisciplinary health professional perspective. Discussions include the influence of visual impairment on mobility and activities of daily living, the effects of medications on vision, visual cognitive factors on falls risk and visual training interventions. Finally, implications for multidisciplinary health professional practice and suggestions for future research are offered.

Vision and agility training in community dwelling older adults: incorporating visual training into programs for fall prevention.

This study aimed to examine the effect of visual training on obstacle course performance of independent community dwelling older adults. Agility is the ability to rapidly alter ongoing motor patterns, an important aspect of mobility which is required in obstacle avoidance. However, visual information is also a critical factor in successful obstacle avoidance. We compared obstacle course performance of a group that trained in visually driven body movements and agility drills, to a group that trained only in agility drills. We also included a control group that followed the American College of Sports Medicine exercise recommendations for older adults. Significant gains in fitness, mobility and power were observed across all training groups. Obstacle course performance results revealed that visual training had the greatest improvement on obstacle course performance (22%) following a 12 week training program. These results suggest that visual training may be an important consideration for fall prevention programs.

WiiFit™ Plus balance test scores for the assessment of balance and mobility in older adults.

The Nintendo Wii™ is becoming an increasingly popular technology for the training and assessment of balance in older adults. Recent studies have shown promising results for its use in fall prevention. However, it is not clear how scores on the WiiFit™ balance games relate to current standardized tests of balance and mobility. The purpose of this study was to evaluate the relationship between WiiFit™ Plus balance tests, and standardized tests of older adult fitness, balance, mobility, self-reported balance confidence, and visual attention and processing. Results from 34 older adult participants indicate that WiiFit™ balance tests do not correlate well with standardized functional balance, mobility and fitness tests. However, the Wii balance score, as measured by the Basic Balance Test of the WiiFit™, does correlate with visual processing speed as measured by the Useful Field of View (UFOV(®)) test. These results indicate that WiiFit™ balance tests may provide advantageous information supplementary to information obtained through standard functional mobility and balance tests; however, caution should be used when using the WiiFit™ balance tests in isolation. Further research is necessary as these technologies become widely used in clinical and home settings for balance training and assessment.