Alteration of postural responses to visual field motion in mild traumatic brain injury

Coordination of hip and spine in individuals with acute low back pain during unstable sitting

BACKGROUND CONTEXT

Trunk postural control differs between individuals with and without chronic low back pain (LBP). Whether this corresponds to differences in hip/spine coordination during the early acute phase of LBP (ALBP) is unclear.

PURPOSE

To compare hip/spine coordination in relation to seat movements between individuals with and without ALBP when balancing on an unstable seat and to identify coordination strategies to maintain balance using cluster analysis.

STUDY DESIGN/SETTING

Cross-sectional observational study.

PATIENT SAMPLE

ALBP (n=130) and pain-free (n=72) individuals.

OUTCOME MEASURES

Frequency domain measures to evaluate hip/spine coordination (amplitude spectrum, phase angle, and coherence) and time-series measures to assess overall balance performance (center of pressure [CoP] reflecting the amount of seat movements, upper thorax motion as a surrogate for head motion).

METHODS

Participants maintained balance while sitting on a seat fixed to a hemisphere. Seat, hip, and spine (lower lumbar, lumbar, upper lumbar, and thoracic) angular motion and force plate data were recorded.

RESULTS

Overall, seat/CoP movements (amplitude spectrum and RMSdisplacement) were greater (in both planes) and sagittal coordination (coherence) between the hip or lower spine and seat movements was lower in ALBP than controls. Cluster analysis using coherence data revealed different coordination strategies to maintain balance. Separate clusters used a "lower lumbar strategy" and "hip strategy" in the sagittal plane, and a "lower and upper lumbar strategy" and "lower lumbar strategy" in the frontal plane. A cluster using a "low coherence strategy" in both planes was also identified.

CONCLUSIONS

Hip and lower spine coordination was less in individuals with ALBP in conjunction with a lower quality of overall balance performance. However, interpretation of the relationship between coherence and overall balance performance was not straightforward. Clusters in both the ALBP group and the control group adopted a low coherence strategy, and this was not consistently related to poor overall balance performance. This suggests overall balance performance cannot be inferred from coherence alone and requires consideration of interaction of other different features.

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

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

Subtle impairments of perceptual-motor function and well-being are detectable among military cadets and college athletes with self-reported history of concussion

Introduction

A lack of obvious long-term effects of concussion on standard clinical measures of behavioral performance capabilities does not preclude the existence of subtle neural processing impairments that appear to be linked to elevated risk for subsequent concussion occurrence, and which may be associated with greater susceptibility to progressive neurodegenerative processes. The purpose of this observational cohort study was to assess virtual reality motor response variability and survey responses as possible indicators of suboptimal brain function among military cadets and college athletes with self-reported history of concussion (HxC).

Methods

The cohort comprised 75 college students (20.7 ± 2.1 years): 39 Reserve Officer Training Corp (ROTC) military cadets (10 female), 16 football players, and 20 wrestlers; HxC self-reported by 20 (29.2 ± 27.1 months prior, range: 3-96). A virtual reality (VR) test involving 40 lunging/reaching responses to horizontally moving dots (filled/congruent: same direction; open/incongruent: opposite direction) was administered, along with the Sport Fitness and Wellness Index (SFWI) survey. VR Dispersion (standard deviation of 12 T-scores for neck, upper extremity, and lower extremity responses to congruent vs. incongruent stimuli originating from central vs. peripheral locations) and SFWI response patterns were the primary outcomes of interest.

Results

Logistic regression modeling of VR Dispersion (range: 1.5-21.8), SFWI (range: 44-100), and an interaction between them provided 81% HxC classification accuracy (Model χ ²[2] = 26.03, p < .001; Hosmer & Lemeshow χ ²[8] = 1.86, p = .967; Nagelkerke R ²= .427; Area Under Curve = .841, 95% CI: .734, .948). Binary modeling that included VR Dispersion ≥3.2 and SFWI ≤86 demonstrated 75% sensitivity and 86% specificity with both factors positive (Odds Ratio = 17.6, 95% CI: 5.0, 62.1).

Discussion/Conclusion

Detection of subtle indicators of altered brain processes that might otherwise remain unrecognized is clearly important for both short-term and long-term clinical management of concussion. Inconsistency among neck, upper extremity, and lower extremity responses to different types of moving visual stimuli, along with survey responses suggesting suboptimal well-being, merit further investigation as possible clinical indicators of persisting effects of concussion that might prove to be modifiable.

Evolution of postural control assessment: From dynamic posturography to virtual reality

During the early years of spaceflight it was documented that astronauts were impaired and incapacitated upon return to earth. Computerized Dynamic Posturography (CDP) was devised to investigate and quantify this deficit, and eventually progressed into a clinical assessment tool. The current sprouting of virtual reality (VR) technologies has allowed for the development of an alternative approach that could be more informative. Many low-cost VR systems (including desktop gaming programs designed for rehabilitation) are now available. Continued improvements in this technology indicate a high probability that VR will become an integral component of posturography by replacing present mechanical CDP techniques. We researched the relevant literature to evaluate the strengths and weaknesses of CDP using the Equitest (Neurocom International; Clackamas USA), and the added benefits of incorporating VR to help clinicians assess the complex task of balance maintenance. VR is capable of manipulating task and environmental demands in order to assess functional postural behavior. VR is also a useful tool for clinical testing of postural disorders resulting from sensory mismatch. Although posturography is still a useful clinical tool, VR provides an inherent conflict between the visual and vestibular senses and can elevate the effectiveness of CDP for both assessment and intervention. We conclude that, when initially developed, CDP was innovative and ahead of its time. However, with the advent of VR, we have a chance to modernize CDP and enhance its value as a clinical instrument.

Dynamic Visual Stimulations Produced in a Controlled Virtual Reality Environment Reveals Long-Lasting Postural Deficits in Children With Mild Traumatic Brain Injury

Motor control deficits outlasting self-reported symptoms are often reported following mild traumatic brain injury (mTBI). The exact duration and nature of these deficits remains unknown. The current study aimed to compare postural responses to static or dynamic virtual visual inputs and during standard clinical tests of balance in 38 children between 9 and 18 years-of-age, at 2 weeks, 3 and 12 months post-concussion. Body sway amplitude (BSA) and postural instability (vRMS) were measured in a 3D virtual reality (VR) tunnel (i.e., optic flow) moving in the antero-posterior direction in different conditions. Measures derived from standard clinical balance evaluations (BOT-2, Timed tasks) and post-concussion symptoms (PCSS-R) were also assessed. Results were compared to those of 38 healthy non-injured children following a similar testing schedule and matched according to age, gender, and premorbid level of physical activity. Results highlighted greater postural response with BSA and vRMS measures at 3 months post-mTBI, but not at 12 months when compared to controls, whereas no differences were observed in post-concussion symptoms between mTBI and controls at 3 and 12 months. These deficits were specifically identified using measures of postural response in reaction to 3D dynamic visual inputs in the VR paradigm, while items from the BOT-2 and the 3 timed tasks did not reveal deficits at any of the test sessions. PCSS-R scores correlated between sessions and with the most challenging condition of the BOT-2 and as well as with the timed tasks, but not with BSA and vRMS. Scores obtained in the most challenging conditions of clinical balance tests also correlated weakly with BSA and vRMS measures in the dynamic conditions. These preliminary findings suggest that using 3D dynamic visual inputs such as optic flow in a controlled VR environment could help detect subtle postural impairments and inspire the development of clinical tools to guide rehabilitation and return to play recommendations.

The Marcus Institute for Brain Health: an integrated practice unit for the care of traumatic brain injury in military veterans

PRIMARY OBJECTIVE

Traumatic brain injury (TBI) is a signature wound of recent Unites States military conflicts. The National Intrepid Center of Excellence (NICoE) has demonstrated that interdisciplinary care is effective for active-duty military personnel with TBI and related psychological health conditions. This paper details how the Marcus Institute for Brain Health (MIBH), established in 2017 as an Integrated Practice Unit (IPU), is founded on the NICoE model and is dedicated to interdisciplinary care for Veterans with persistent symptoms due to TBI and psychological comorbidities.

RESEARCH DESIGN

A highly integrated group of clinicians from diverse disciplines combine their expertise to offer comprehensive evaluation, intensive outpatient treatment, and program outcomes evaluation.

METHODS AND PROCEDURES

The role of each discipline in the provision of care, and the regular interaction of all clinicians, are delineated. A strong connection to academic medicine is maintained so that clinical research and education complement patient care.

MAIN OUTCOMES AND RESULTS

Over three hundred veterans and family members have received treatment at the MIBH. Program evaluation is underway.

CONCLUSIONS

As the understanding of TBI and related psychological conditions continues its rapid evolution, the expert interdisciplinary care at the MIBH has great promise as a Veteran counterpart of the NICoE.

Potential Mechanisms of Acute Standing Balance Deficits After Concussions and Subconcussive Head Impacts: A Review

Standing balance deficits are prevalent after concussions and have also been reported after subconcussive head impacts. However, the mechanisms underlying such deficits are not fully understood. The objective of this review is to consolidate evidence linking head impact biomechanics to standing balance deficits. Mechanical energy transferred to the head during impacts may deform neural and sensory components involved in the control of standing balance. From our review of acute balance-related changes, concussions frequently resulted in increased magnitude but reduced complexity of postural sway, while subconcussive studies showed inconsistent outcomes. Although vestibular and visual symptoms are common, potential injury to these sensors and their neural pathways are often neglected in biomechanics analyses. While current evidence implies a link between tissue deformations in deep brain regions including the brainstem and common post-concussion balance-related deficits, this link has not been adequately investigated. Key limitations in current studies include inadequate balance sampling duration, varying test time points, and lack of head impact biomechanics measurements. Future investigations should also employ targeted quantitative methods to probe the sensorimotor and neural components underlying balance control. A deeper understanding of the specific injury mechanisms will inform diagnosis and management of balance deficits after concussions and subconcussive head impact exposure.

Visuo-motor integration, vision perception and attention in mTBI patients. Preliminary findings

Patients with mild traumatic brain injuries (mTBI) often report difficulties in motor coordination and visuo-spatial attention. However, the consequences of mTBI on fine motor and visuo-motor coordination are still not well understood. We aimed to evaluate whether mTBI had a concomitant effect on fine motor ability and visuo-motor integration and whether this is related to visual perception and visuo-spatial attention impairments, including patients at different symptoms stage. Eleven mTBI patients (mean age 22.8 years) and ten healthy controls participated in the study. Visuo-motor integration of fine motor abilities and form recognition were measured with the Beery-Buktenica Developmental Test of Visual-Motor Integration test, motion perception was evaluated with motion coherence test, critical flicker fusion was measured with Pocket CFF tester. Visuo-spatial was assessed with the Ruff 2 & 7 Selection Attention Test. mTBI patients showed reduced visuo-motor integration, form recognition, and motor deficits as well as visuo-spatial attention impairment, while motion perception and critical flicker fusion were not impaired. These preliminary findings suggest that the temporary brain insults deriving from mTBI compromise fine motor skills, visuomotor integration, form recognition, and visuo-spatial attention. The impairment in visuo-motor coordination was associated with speed in visuo-attention and correlated with symptoms severity while motor ability was correlated with time since concussion. Given the strong correlation between visuomotor coordination and symptom severity, further investigation with a larger sample seems warranted. Since there appeared to be differences in motor skills with respect to symptom stage, further research is needed to investigate symptom profiles associated with visuomotor coordination and fine motor deficits in mTBI patients.

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

OBJECTIVE

To examine how concussion may impair sensory processing for control of upright stance.

METHODS

Participants were recruited from a single university into 3 groups: 13 participants (8 women, 21 ± 3 years) between 2 weeks and 6 months post-injury who initiated a return-to-play progression (under physician management) by the time of testing (recent concussion group), 12 participants (7 women, 21 ± 1 years) with a history of concussion (concussion history group, > 1 year post-injury), and 26 participants (8 women, 22 ± 3 years) with no concussion history (control group). We assessed sensory reweighting by simultaneously perturbing participants' visual, vestibular, and proprioceptive systems and computed center of mass gain relative to each modality. The visual stimulus was a sinusoidal translation of the visual scene at 0.2 Hz, the vestibular stimulus was ± 1 mA binaural monopolar galvanic vestibular stimulation (GVS) at 0.36 Hz, the proprioceptive stimulus was Achilles' tendon vibration at 0.28 Hz.

RESULTS

The recent concussion (95% confidence interval 0.078-0.115, p = 0.001) and the concussion history (95% confidence interval 0.056-0.094, p = 0.038) groups had higher gains to the vestibular stimulus than the control group (95% confidence interval 0.040-0.066). The recent concussion (95% confidence interval 0.795-1.159, p = 0.002) and the concussion history (95% confidence interval 0.633-1.012, p = 0.018) groups had higher gains to the visual stimulus than the control group (95% confidence interval 0.494-0.752). There were no group differences in gains to the proprioceptive stimulus or in sensory reweighting.

CONCLUSION

Following concussion, participants responded more strongly to visual and vestibular stimuli during upright stance, suggesting they may have abnormal dependence on visual and vestibular feedback. These findings may indicate an area for targeted rehabilitation interventions.

Tomographic Task-Related Functional Near-Infrared Spectroscopy in Acute Sport-Related Concussion: An Observational Case Study

Making decisions regarding return-to-play after sport-related concussion (SRC) based on resolution of symptoms alone can expose contact-sport athletes to further injury before their recovery is complete. Task-related functional near-infrared spectroscopy (fNIRS) could be used to scan for abnormalities in the brain activation patterns of SRC athletes and help clinicians to manage their return-to-play. This study aims to show a proof of concept of mapping brain activation, using tomographic task-related fNIRS, as part of the clinical assessment of acute SRC patients. A high-density frequency-domain optical device was used to scan 2 SRC patients, within 72 h from injury, during the execution of 3 neurocognitive tests used in clinical practice. The optical data were resolved into a tomographic reconstruction of the brain functional activation pattern, using diffuse optical tomography. Moreover, brain activity was inferred using single-subject statistical analyses. The advantages and limitations of the introduction of this optical technique into the clinical assessment of acute SRC patients are discussed.

Visual and Vestibular Integration Express Summative Eye Movement Responses and Reveal Higher Visual Acceleration Sensitivity than Previously Described

Purpose

Acceleration plays a great impact on the vestibular system, but is attributed little influence over vision. This study aims to explore how visual and vestibular acceleration affect roll-plane oculomotor responses, including their addiative effect.

Methods

Seated in a mechanical sled, 13 healthy volunteers (7 men, 6 women; mean age 25 years) were exposed to a series of visual (VIS) optokinetic, vestibular (VES) whole-body, and combined (VIS + VES) rotations. This was carried out at two acceleration intensities. Subjects wore a video-based eye tracker, enabling analysis of torsional and skewing eye movement responses, which were used to evaluate the individual response to each trial. The tracker also contained accelerometers allowing head tracking.

Results

Both ocular torsion and vertical skewing were sensitive to acceleration intensities for VES and VIS + VES. For VIS only, skewing exhibited such a response. An increased acceleration yielded a decreased torsion-skewing ratio for VIS, explained by the change in skewing, but remained unchanged for VES and VIS + VES. Torsion exhibited particularly reliable summative effect, yielding a relative contribution of 32% VIS and 75% VES during low acceleration, and 19% and 85%, respectively, during high acceleration.

Conclusions

The change in the skewing response to different intensities indicates that the visual system is more sensitive to visual accelerations than previously described. Eye movements showed reliable summative effects, indicating a robust visual-vestibular integration that indicates their integrative priorities for each acceleration, with the visual system being more involved during low accelerations. Such objective quantifications could hold clinical utility when assessing sensory mismatch in vertiginous patients.

Recovery Trajectory of Postural Control Impairments Following a Concussion: A Case Study

CONTEXT

Altered postural control represents one of the most common motor consequences following a concussion and there is a paucity of data monitoring the recovery trajectory that identifies the persistent changes of postural control.

OBJECTIVE

To determine whether the recovery trajectory of postural control was consistent across different measures of postural stability and whether increased postural challenge (ie, sloped surface) revealed subtle postural impairments.

DESIGN

A single-subject case study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

One concussed individual with a cohort of healthy controls (n = 10) used for comparison.

MAIN OUTCOME MEASURES

Center of pressure variability (linear-SD and nonlinear-multiscale entropy) was used to index postural sway preinjury and at periodic intervals following the concussion.

RESULTS

The concussed individuals displayed reduced amounts of sway during the initial recovery phase that failed to returned to preinjury levels but reached the level of healthy controls at 1-month postinjury. The multiscale entropy analysis revealed increased center of pressure irregularity throughout recovery that persisted up to 1-month post injury.

CONCLUSIONS

The findings identified subtle, persistent postural control impairments revealed through the nonlinear analysis of center of pressure and supports the notion that the consequences of a concussion (ie, impaired postural control) need to be considered beyond the resolution of behavioral symptoms.

Vestibular and Balance Dysfunction Following Sport-Related Concussion

Purpose

Sport-related concussion is a significant public health concern that requires a multidisciplinary team to appropriately manage. Athletes often report dizziness and imbalance following concussion, and these symptoms can predict increased time to recover. Vestibular diagnostic evaluations provide important information regarding the athlete's oculomotor, gaze stability, and balance function in order to identify deficits for rehabilitation. These measures also describe objective function helpful for determining when an athlete is ready to return to play. The purpose of this clinical focus article is to provide background on the current understanding of the effects of concussion on the peripheral and central vestibular system, as well as information on a protocol that can be used for acute concussion assessment. Case studies describing 3 common postconcussion presentations will highlight the usefulness of this protocol.

Conclusion

Sport-related concussion is a highly visible disorder with many symptoms that may be evaluated in the vestibular clinic. A thoughtful protocol evaluating the typical presentation of these patients may help guide the multidisciplinary team in determining appropriate management and clearance for return to sport.

Determining Outcome in Children and Adolescents After Concussion: Viewing Things More Holistically

Pediatric and adolescent concussion is an increasingly high-profile public health issue, but it is also a highly heterogeneous phenomenon. Many factors interact dynamically to influence the recovery trajectory of adolescents and children. Diagnostic assessment must include domains other than self-reported symptoms, yet many prognostic models of outcome focus solely on the presence or absence of postconcussion symptoms to determine recovery. Function after concussion (recovery or persistence of problems) is the result of an interaction between biological, psychological, and social factors. Despite biopsychosocial models of assessment being advocated in rehabilitation for the last 20 years, they are still not routinely implemented in the evaluation of concussions, along the recovery trajectory, in children and adolescents. The International Classification of Functioning, Disability and Health is a framework anchored in a biopsychosocial perspective that can guide clinicians and researchers to include multiple perspectives in their assessments or research designs. By focusing on the patient as a person, researchers and clinicians can provide a more holistic approach that has the potential to contribute to a more successful and sustainable pediatric and adolescent concussion care model. J Orthop Sports Phys Ther 2019;49(11):855-863. Epub 9 Oct 2019. doi:10.2519/jospt.2019.8918.

Effect of Optic Flow on Postural Control in Children and Adults with Autism Spectrum Disorder

Individuals with autism spectrum disorder (ASD) have been associated with sensorimotor difficulties, commonly presented by poor postural control. Postural control is necessary for all motor behaviors. However, findings concerning the effect of visual motion on postural control and the age progression of postural control in individuals with ASD are inconsistent. The aims of the present study were to examine postural responses to optic flow in children and adults with and without ASD, postural responses to optic flow in the central and peripheral visual fields, and the changes in postural responses between the child and adult groups. Thirty-three children (8-12 years old) and 33 adults (18-50 years old) with and without ASD were assessed on quiet standing for 60 seconds under conditions of varying optic flow illusions, consisting of different combinations of optic flow directions and visual field display. The results showed that postural responses to most optic flow conditions were comparable between children with and without ASD and between adults with and without ASD. However, adults with ASD appeared more responsive to forward-moving optic flow in the peripheral visual field compared with typically developed adults. The findings suggest that children and adults with ASD may not display maladaptive postural responses all the time. In addition, adults in the ASD group may have difficulties prioritizing visual information in the central visual field over visual information in the peripheral visual field when in unfamiliar environments, which may have implications in understanding their motor behaviors in new surroundings.

Examining the Reversibility of Long-Term Behavioral Disruptions in Progeny of Maternal SSRI Exposure

Serotonergic dysregulation is implicated in numerous psychiatric disorders. Serotonin plays widespread trophic roles during neurodevelopment; thus perturbations to this system during development may increase risk for neurodevelopmental disorders. Epidemiological studies have examined association between selective serotonin reuptake inhibitor (SSRI) treatment during pregnancy and increased autism spectrum disorder (ASD) risk in offspring. It is unclear from these studies whether ASD susceptibility is purely related to maternal psychiatric diagnosis, or if treatment poses additional risk. We sought to determine whether maternal SSRI treatment alone or in combination with genetically vulnerable background was sufficient to induce offspring behavior disruptions relevant to ASD. We exposed C57BL/6J or Celf6^+/- mouse dams to fluoxetine (FLX) during different periods of gestation and lactation and characterized offspring on tasks assessing social communicative interaction and repetitive behavior patterns including sensory sensitivities. We demonstrate robust reductions in pup ultrasonic vocalizations (USVs) and alterations in social hierarchy behaviors, as well as perseverative behaviors and tactile hypersensitivity. Celf6 mutant mice demonstrate social communicative deficits and perseverative behaviors, without further interaction with FLX. FLX re-exposure in adulthood ameliorates the tactile hypersensitivity yet exacerbates the dominance phenotype. This suggests acute deficiencies in serotonin levels likely underlie the abnormal responses to sensory stimuli, while the social alterations are instead due to altered development of social circuits. These findings indicate maternal FLX treatment, independent of maternal stress, can induce behavioral disruptions in mammalian offspring, thus contributing to our understanding of the developmental role of the serotonin system and the possible risks to offspring of SSRI treatment during pregnancy.

Visual-vestibular processing deficits in mild traumatic brain injury

BACKGROUND

The search for reliable and valid signs and symptoms of mild traumatic brain injury (mTBI), commonly synonymous with concussion, has lead to a growing body of evidence that individuals with long-lasting, unremitting impairments often experience visual and vestibular symptoms, such as dizziness, postural and gait disturbances.

OBJECTIVE

Investigate the role of visual-vestibular processing deficits following concussion.

METHODS

A number of clinically accepted vestibular, oculomotor, and balance assessments as well as a novel virtual reality (VR)-based balance assessment device were used to assess adults with post-acute concussion (n = 14) in comparison to a healthy age-matched cohort (n = 58).

RESULTS

Significant between-group differences were found with the VR-based balance device (p = 0.001), with dynamic visual motion emerging as the most discriminating balance condition. The symptom reports collected after performing the oculomotor and vestibular tests: rapid alternating horizontal eye saccades, optokinetic stimulation, and gaze stabilization, were all sensitive to health status (p < 0.05), despite the absence of oculomotor abnormalities being observed, except for near-point convergence. The BESS, King-Devick, and Dynamic Visual Acuity tests did not detect between-group differences.

CONCLUSION

Postural and visual-vestibular tasks most closely linked to spatial and self-motion perception had the greatest discriminatory outcomes. The current findings suggest that mesencephalic and parieto-occipital centers and pathways may be involved in concussion.

A prospective investigation of changes in the sensorimotor system following sports concussion. An exploratory study

BACKGROUND

Sports concussion is a risk for players involved in high impact, collision sports. Post-concussion, the majority of symptoms subside within 7-10 days, but can persist in 10-20% of athletes. Understanding the effects of sports concussion on sensorimotor systems could inform physiotherapy treatment.

OBJECTIVE

To explore changes in sensorimotor function in the acute phase following sports concussion.

DESIGN

Prospective cohort study.

METHODS

Fifty-four players from elite rugby union and league teams were assessed at the start of the playing season. Players who sustained a concussion were assessed three to five days later. Measures included assessments of balance (sway velocity), vestibular system function (vestibular ocular reflex gain; right-left asymmetry), cervical proprioception (joint position error) and trunk muscle size and function.

RESULTS

During the playing season, 14 post-concussion assessments were performed within 3-5 days of injury. Significantly decreased sway velocity and increased size/contraction of trunk muscles, were identified. Whilst not significant overall, large inter-individual variation of test results for cervical proprioception and the vestibular system was observed.

LIMITATIONS

The number of players who sustained a concussion was not large, but numbers were comparable with other studies in this field. There was missing baseline data for vestibular and cervical proprioception testing for some players.

CONCLUSIONS

Preliminary findings post-concussion suggest an altered balance strategy and trunk muscle control with splinting/over-holding requiring consideration as part of the development of appropriate physiotherapy management strategies.

Assessing subacute mild traumatic brain injury with a portable virtual reality balance device

PURPOSE

Balance impairment is a common sensorimotor symptom in mild traumatic brain injury (mTBI). We designed an affordable, portable virtual reality (VR)-based balance screening device (Virtual Environment TBI Screen [VETS]), which will be validated relative to the Neurocom Sensory Organization Test (SOT) to determine if it can replace commonly used postural assessments.

METHODS

This preliminary study examines healthy adults (n = 56) and adults with mTBI (n = 11). Participants performed six upright postural tasks on the VETS and the SOT. Analysis of variance was used to determine between-group differences. Pearson's correlations were used to establish construct validity. Known-groups approach was used to establish classification accuracy.

RESULTS

The mTBI cohort performed significantly worse than the healthy cohort on the new device (p = 0.001). The new device has 91.0% accuracy and an ROC curve with a significant area-under-the-curve (AUC = 0.865, p < 0.001). Conditions with dynamic visual stimulation were the most sensitive to health status. The SOT had an 84.8% accuracy and AUC =0.703 (p = 0.034).

CONCLUSIONS

The new VR-based device is a valid measure for detecting balance impairment following mTBI and can potentially replace more expensive and cumbersome equipment. Assessments that test visual-vestibular processing, such as VETS, increase sensitivity to mTBI-related balance deficits, which can be used to guide rehabilitation. Implications for rehabilitation Emerging technology using virtual reality can be economically integrated into the clinical setting for easy testing of postural control in neurologically impaired populations. Tailoring postural assessments to include tasks that rely on visual and vestibular integration will increase the accuracy of detecting balance impairment following mild traumatic brain injury.

Differential Sensitivity Between a Virtual Reality Balance Module and Clinically Used Concussion Balance Modalities

OBJECTIVE

Balance assessments are part of the recommended clinical concussion evaluation, along with computerized neuropsychological testing and self-reported symptoms checklists. New technology has allowed for the creation of virtual reality (VR) balance assessments to be used in concussion care, but there is little information on the sensitivity and specificity of these evaluations. The purpose of this study is to establish the sensitivity and specificity of a VR balance module for detecting lingering balance deficits clinical concussion care.

DESIGN

Retrospective case-control study.

SETTING

Institutional research laboratory.

PARTICIPANTS

Normal controls (n = 94) and concussed participants (n = 27).

INTERVENTIONS

All participants completed a VR balance assessment paradigm. Concussed participants were diagnosed by a Certified Athletic Trainer or physician (with 48 hours postinjury) and tested in the laboratory between 7 and 10 days postinjury. Receiver operating characteristic curves were performed to establish the VR module's sensitivity and specificity for detecting lingering balance deficits.

MAIN OUTCOME MEASURES

Final balance score.

RESULTS

For the VR balance module, a cutoff score of 8.25 was established to maximize sensitivity at 85.7% and specificity at 87.8%.

CONCLUSIONS

The VR balance module has high sensitivity and specificity for detecting subacute balance deficits after concussive injury.

CLINICAL RELEVANCE

The VR balance has a high subacute sensitivity and specificity as a stand-alone balance assessment tool and may detect ongoing balance deficits not readily detectable by the Balance Error Scoring System or Sensory Organization Test. Virtual reality balance modules may be a beneficial addition to the current clinical concussion diagnostic battery.

Validation of a virtual reality balance module for use in clinical concussion assessment and management

OBJECTIVE

To determine the criterion and content validity of a virtual reality (VR) balance module for use in clinical practice.

DESIGN

Retrospective, VR balance module completed by participants during concussion baseline or assessment testing session.

SETTING

A Pennsylvania State University research laboratory.

PARTICIPANTS

A total of 60 control and 28 concussed students and athletes from the Pennsylvania State University.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

This study examined: (1) the relationship between VR composite balance scores (final, stationary, yaw, pitch, and roll) and area of the center-of-pressure (eyes open and closed) scores and (2) group differences (normal volunteers and concussed student-athletes) on VR composite balance scores.

RESULTS

With the exception of the stationary composite score, all other VR balance composite scores were significantly correlated with the center of pressure data obtained from a force platform. Significant correlations ranged from r = -0.273 to -0.704 for the eyes open conditions and from r = -0.353 to -0.876 for the eyes closed condition. When examining group differences on the VR balance composite modules, the concussed group did significantly (P < 0.01) worse on all measures compared with the control group.

CONCLUSIONS

The VR balance module met or exceeded the criterion and content validity standard set by the current balance tools and may be appropriate for use in a clinical concussion setting.

CLINICAL RELEVANCE

Virtual reality balance module is a valid tool for concussion assessment in clinical settings. This novel type of balance assessment may be more sensitive to concussion diagnoses, especially later (7-10 days) in the recovery phase than current clinical balance tools.

Modulation of cortical activity in 2D versus 3D virtual reality environments: an EEG study

There is a growing empirical evidence that virtual reality (VR) is valuable for education, training, entertaining and medical rehabilitation due to its capacity to represent real-life events and situations. However, the neural mechanisms underlying behavioral confounds in VR environments are still poorly understood. In two experiments, we examined the effect of fully immersive 3D stereoscopic presentations and less immersive 2D VR environments on brain functions and behavioral outcomes. In Experiment 1 we examined behavioral and neural underpinnings of spatial navigation tasks using electroencephalography (EEG). In Experiment 2, we examined EEG correlates of postural stability and balance. Our major findings showed that fully immersive 3D VR induced a higher subjective sense of presence along with enhanced success rate of spatial navigation compared to 2D. In Experiment 1 power of frontal midline EEG (FM-theta) was significantly higher during the encoding phase of route presentation in the 3D VR. In Experiment 2, the 3D VR resulted in greater postural instability and modulation of EEG patterns as a function of 3D versus 2D environments. The findings support the inference that the fully immersive 3D enriched-environment requires allocation of more brain and sensory resources for cognitive/motor control during both tasks than 2D presentations. This is further evidence that 3D VR tasks using EEG may be a promising approach for performance enhancement and potential applications in clinical/rehabilitation settings.

Rigid, Variable-View Endoscope in Neurosurgery

Introduction. The endoscope became a highly valued visualization tool in neurosurgery. However, technical limitations caused by the rigidity of current standard endoscopes significantly decrease ergonomy in transcranial neurosurgery. Further technological developments will aid enlarging the surgical applicability. Objective. To evaluate the intraoperative features of a rigid variable-view endoscope in neurosurgery. Methods. We assessed a 4 mm rigid rod lens endoscope (EndoCAMeleon, Karl Storz, Tuttlingen, Germany) in the intraoperative setting. The device offers a variable angle of view from 15° to 90° in one plane. The endoscope was used in 3 cases (aneurysm clipping, vestibular schwannoma surgery, endoscopic third ventriculostomy) for inspection. Results. Direct insertion of the device through the craniotomy/burr hole with the lowest angled view (15°) was always possible. Neurovascular structures crossing the access route could be visualized and avoided. This allowed a targeted positioning of the endoscope’s tip in the operating field. Once the target point was reached, viewing direction was changed in one plane from 15° to 90° according to anatomic demands. As the endoscope’s tip does not move while the lens is rotated, surrounding neurovascular structures are not at risk to be injured. However, turning of the lens-controlling wheel in proximity to delicate structures may be inconvenient. Conclusion. The rigid, variable-view endoscope has the potential to become an appreciated visualization tool in neuroendoscopy. The steerable lens enables a tremendous expansion of the visual field, resulting in higher efficiency for surgeons and increased safety for patients.

Athletes' age, sex, and years of education moderate the acute neuropsychological impact of sports-related concussion: a meta-analysis

The objective of this study is to determine which pre-existing athlete characteristics, if any, are associated with greater deficits in functioning following sports-related concussion, after controlling for factors previously shown to moderate this effect (e.g., time since injury). Ninety-one independent samples of concussion were included in a fixed+systematic effects meta-analysis (n = 3,801 concussed athletes; 5,631 controls). Moderating variables were assessed using analogue-to-ANOVA and meta-regression analyses. Post-injury assessments first conducted 1-10 days following sports-related concussion revealed significant neuropsychological dysfunction, postural instability and post-concussion symptom reporting (d = -0.54, -1.10, and -1.14, respectively). During this interval, females (d = -0.87), adolescent athletes competing in high school competitions (d = -0.60), and those with 10 years of education (d = -1.32) demonstrated larger post-concussion neuropsychological deficits than males (d = -0.42), adults (d = -0.25), athletes competing at other levels of competition (d = -0.43 to -0.41), or those with 16 years of education (d = -0.15), respectively. However, these sub-groups' differential impairment/recovery beyond 10 days could not be reliably quantified from available literature. Pre-existing athlete characteristics, particularly age, sex and education, were demonstrated to be significant modifiers of neuropsychological outcomes within 10 days of a sports-related concussion. Implications for return-to-play decision-making and future research directions are discussed.

Concussion in athletics: ongoing clinical and brain imaging research controversies

Concussion, the most common form of traumatic brain injury, proves to be increasingly complex and not mild in nature as its synonymous term mild traumatic brain injury (mTBI) would imply. Despite the increasing occurrence and prevalence of mTBI there is no universally accepted definition and conventional brain imaging techniques lack the sensitivity to detect subtle changes it causes. Moreover, clinical management of sports induced mild traumatic brain injury has not changed much over the past decade. Advances in neuroimaging that include electroencephalography (EEG), functional magnetic resonance imaging (fMRI), resting-state functional connectivity, diffusion tensor imaging (DTI) and magnetic resonance spectroscopy (MRS) offer promise in aiding research into understanding the complexities and nuances of mTBI which may ultimately influence clinical management of the condition. In this paper the authors review the major findings from these advanced neuroimaging methods along with current controversy within this field of research. As mTBI is frequently associated with youth and sports injury this review focuses on sports-related mTBI in the younger population.

Residual brain dysfunction observed one year post-mild traumatic brain injury: combined EEG and balance study

OBJECTIVES

There is still considerable debate and controversy about whether EEG can be used as a robust clinical tool for assessment of mild traumatic brain injury (MTBI). Nonhomogeneous subject populations, inaccurate assessment of severity of brain injury, time since injury when EEG testing was performed, the lack of EEG research conducted serially and in conjunction with other behavioral measures as injury evolves over time may contribute to the existing controversies. In this study, we implemented a concussion assessment protocol combining a series of EEG and balance measures throughout one year post-injury to document the efficacy of EEG and balance measures as relate to differential recovery of patients suffering from MTBI.

METHODS

Three hundred and eighty subjects at risk for MTBI were initially recruited for baseline testing. Forty nine from this initial subjects pool subsequently suffered a single episode of concussive blow and were tested on day 7, 15, 30 days, 6 months and 12 months post-injury. EEGs were recorded while sitting, standing on the force plate and then on a foam base of support with eyes open/closed conditions. EEG alpha power (8-12 Hz) and its percent suppression from sitting to standing postures were computed. The center of pressure (COP) measures were obtained from the force platform and analyzed for eyes open and eyes closed conditions.

RESULTS

Percent alpha power suppression from sitting to standing postural conditions significantly increased in MTBI subjects shortly after the injury (p<0.01). Percent alpha power suppression significantly correlated with increased area of COP during standing posture with eye closed (r(2)=0.53, p<0.01). The magnitude of alpha power suppression predicted the rate of recovery of this measure in sub-acute and chronic phases of injury (r(2)=0.609, p<0.01). Finally, 85% of MTBI subjects who showed more than 20% of alpha power suppression in the acute phase of injury did not return to pre-injury status up to 12 months post-injury.

CONCLUSIONS

The efficacy of serially implemented EEG measures in conjunction with balance assessment over the course of MTBI evolution to document residual cerebral dysfunction was demonstrated. Specifically, alteration of EEG alpha power dynamics in conjunction with balance data in the acute phase of injury with respect to baseline measures may predict the rate of recovery from a single concussive blow.

SIGNIFICANCE

Neurophysiological measures are excellent tools to assess the status and prognosis of patients with MTBI.

Actual state of EndActive ventricular endoscopy

PURPOSE

We assessed usability and applicability of a rigid, multidirectional steerable videoendoscope (EndActive, Karl Storz GmbH, Tuttlingen, Germany) for endoscopic third ventriculostomy and compared our experience with reports about other multidirectional endoscopes.

METHODS

The prototype is a 4-mm-diameter rigid videoendoscope with an integrated image sensor comprising an embedded light source, offering a free viewing direction in a range of 160° while the tip itself does not move. In five specimens (ten sides), we introduced the endoscope via precoronal burr holes through the lateral ventricle and foramen of Monro into the third ventricle. The endoscope's tip was positioned at the level of the mamillary bodies and the previously defined anatomical target structures; anteriorly, the optic chiasm, anterior commissure, infundibulum, tuber cinereum and posteriorly, the entrance to the mesencephalic aqueduct and posterior commissure were inspected.

RESULTS

A single insertion of the videoendoscope was sufficient to explore with the multiplanar viewing mechanism the entire third ventricle. The prototype videoendoscope may be held like a microsurgical instrument in one hand. It is feasible to control movements precisely due to the reduced weight and ergonomic shape of the device.

CONCLUSIONS

The prototype EndActive has the potential to fit in the current concept of ETV and enrich the setting adding working economy and viewing variability.

Alteration of brain default network in subacute phase of injury in concussed individuals: resting-state fMRI study

There are a number of symptoms, both neurological and behavioral, associated with a single episode of r mild traumatic brain injury (mTBI). Neuropsychological testing and conventional neuroimaging techniques are not sufficiently sensitive to detect these changes, which adds to the complexity and difficulty in relating symptoms from mTBI to their underlying structural or functional deficits. With the inability of traditional brain imaging techniques to properly assess the severity of brain damage induced by mTBI, there is hope that more advanced neuroimaging applications will be more sensitive, as well as specific, in accurately assessing mTBI. In this study, we used resting state functional magnetic resonance imaging to evaluate the default mode network (DMN) in the subacute phase of mTBI. Fourteen concussed student-athletes who were asymptomatic based upon clinical symptoms resolution and clearance for aerobic exercise by medical professionals were scanned using resting state functional magnetic resonance imaging. Nine additional asymptomatic yet not medically cleared athletes were recruited to investigate the effect of a single episode of mTBI versus multiple mTBIs on the resting state DMN. In concussed individuals the resting state DMN showed a reduced number of connections and strength of connections in the posterior cingulate and lateral parietal cortices. An increased number of connections and strength of connections was seen in the medial prefrontal cortex. Connections between the left dorso-lateral prefrontal cortex and left lateral parietal cortex showed a significant reduction in magnitude as the number of concussions increased. Regression analysis also indicated an overall loss of connectivity as the number of mTBI episodes increased. Our findings indicate that alterations in the brain resting state default mode network in the subacute phase of injury may be of use clinically in assessing the severity of mTBI and offering some insight into the pathophysiology of the disorder.

Application of a novel measure of EEG non-stationarity as 'Shannon- entropy of the peak frequency shifting' for detecting residual abnormalities in concussed individuals

OBJECTIVE

The aim of this report was to propose a novel measure of non-stationarity of EEG signals, named Shannon- entropy of the peak frequency shifting (SEPFS). The feasibility of this method was documented comparing this measure with traditional time domain assessment of non-stationarity and its application to EEG data sets obtained from student-athletes before and after suffering a single episode of mild traumatic brain injury (mTBI) with age-matched normal controls.

METHODS

Instead of assessing the power density distribution on the time-frequency plane, like previously proposed measures of signal non-stationarity, this new measure is based on the shift of the dominant frequency of the EEG signal over time. We applied SEPFS measure to assess the properties of EEG non-stationarity in subjects before and shortly after they suffered mTBI. Student-athletes at high risk for mTBI (n=265) were tested prior to concussive episodes as a baseline. From this subject pool, 30 athletes who suffered from mTBI were retested on day 30 post-injury. Additional subjects pool (student-athletes without history of concussion, n=30) were recruited and test-re-tested within the same 30 day interval. Thirty-two channels EEG signals were acquired in sitting eyes closed condition.

RESULTS

The results showed that the SEPFS values significantly decreased in subjects suffering from mTBI. Specifically, reduced EEG non-stationarity was observed in occipital, temporal and central brain areas, indicating the possibility of residual brain dysfunctions in concussed individuals. A similar but less statistically significant trend was observed using traditional time domain analysis of EEG non-stationarity.

CONCLUSIONS

The proposed measure has at least two merits of interest: (1) it is less affected by the limited resolution of time-frequency representation of the EEG signal; (2) it takes into account the neural characteristics of the EEG signal that have not been considered in previously proposed measures of non-stationarity.

SIGNIFICANCE

This new method may potentially be used as a complementary tool to assess the alteration of brain functions as a result of mTBI.

Dizziness after traumatic brain injury: Results from an interview study

BACKGROUND

Dizziness is a commonly reported sequel to traumatic brain injury (TBI).

OBJECTIVE

To better define the nature of the symptomatology and the impact that dizziness has on the TBI survivor.

SETTING

A community brain injury rehabilitation programme and a community access programme for TBI survivors.

METHOD

Focus groups with TBI survivors and individual interviews with TBI survivors and some of their carers.

RESULTS

The data confirmed that dizziness is difficult for TBI survivors to define and describe and it consists of multiple symptoms. Dizziness also appears to be associated with significant functional difficulties. Additionally, many of the participants of this study reported falling. Carers reported a number of observable signs of dizziness and indicated that they believed they were able to tell when the person they cared for was dizzy.

CONCLUSION

The results provide information which will help in the development of more appropriate outcome measurement tools for dizziness after a TBI.

Differential effect of first versus second concussive episodes on wavelet information quality of EEG

OBJECTIVE

Recent reports have suggested that long-term residual brain dysfunctions from mild traumatic brain injury (MTBI) that are often overlooked by clinical criteria may be detected using advanced research methods. The aim of the present study was to examine the feasibility of EEG wavelet information quality measures (EEG-IQ) in monitoring alterations of brain functions as well as to determine the differential rate of recovery between the first and second concussive episodes.

METHODS

Student-athletes at high risk for MTBI (n=265) were tested prior to concussive episodes as a baseline. From this subject pool, twenty one athletes who suffered from two concussive episodes within one athletic season and were tested on days 7, 14 and 21 post-first and second injuries using a within-subjects design. Specifically, EEG was recorded and processed using wavelet entropy (EEG-IQ) algorithm along with a battery of neuropsychological (NS) tests. Spatial distribution of EEG-IQ and its dynamics in conjunction with NS data were analyzed prior to and after MTBI.

RESULTS

No neuropsychological deficits were present in concussed subjects beyond 7 days post-injury after first and second concussions. However, EEG-IQ measures were significantly reduced primarily at temporal, parietal and the occipital regions (ROIs) after first and especially after second MTBI (p<0.01) beyond 7 days post-injury. Rate of recovery of EEG-IQ measures was significantly slower after second MTBI compared to those after the first concussion (p<0.01).

CONCLUSIONS

EEG-IQ measures may reveal alterations in the brain of concussed individuals that are most often overlooked by current assessment tools. In this regard, EEG-IQ may potentially be a valuable tool for assessing and monitoring residual brain dysfunction in "asymptomatic" MTBI subjects.

SIGNIFICANCE

The results demonstrate the potential utility of EEG-IQ measures to classify concussed individuals at various stages of recovery.

Automatic classification of athletes with residual functional deficits following concussion by means of EEG signal using support vector machine

There is a growing body of knowledge indicating long-lasting residual electroencephalography (EEG) abnormalities in concussed athletes that may persist up to 10-year postinjury. Most often, these abnormalities are initially overlooked using traditional concussion assessment tools. Accordingly, premature return to sport participation may lead to recurrent episodes of concussion, increasing the risk of recurrent concussions with more severe consequences. Sixty-one athletes at high risk for concussion (i.e., collegiate rugby and football players) were recruited and underwent EEG baseline assessment. Thirty of these athletes suffered from concussion and were retested at day 30 postinjury. A number of task-related EEG recordings were conducted. A novel classification algorithm, the support vector machine (SVM), was applied as a classifier to identify residual functional abnormalities in athletes suffering from concussion using a multichannel EEG data set. The total accuracy of the classifier using the 10 features was 77.1%. The classifier has a high sensitivity of 96.7% (linear SVM), 80.0% (nonlinear SVM), and a relatively lower but acceptable selectivity of 69.1% (linear SVM) and 75.0% (nonlinear SVM). The major findings of this report are as follows: 1) discriminative features were observed at theta, alpha, and beta frequency bands, 2) the minimal redundancy relevance method was identified as being superior to the univariate t -test method in selecting features for the model calculation, 3) the EEG features selected for the classification model are linked to temporal and occipital areas, and 4) postural parameters influence EEG data set and can be used as discriminative features for the classification model. Overall, this report provides sufficient evidence that 10 EEG features selected for final analysis and SVM may be potentially used in clinical practice for automatic classification of athletes with residual brain functional abnormalities following a concussion episode.

Differential rate of recovery in athletes after first and second concussion episodes

OBJECTIVE

Clinical observations suggest that a history of previous concussions may cause a slower recovery of neurological function after recurrent concussion episodes. However, direct examination of this notion has not been provided. This report investigates the differential rate of restoring the visual-kinesthetic integration in collegiate athletes experiencing single versus recurrent concussion episodes.

METHODS

One hundred sixty collegiate athletes were tested preseason using multimodal research methodology. Of these, 38 experienced mild traumatic brain injury (MTBI) and were tested on Days 10, 15, and 30 after injury. Nine of these MTBI patients experienced a second MTBI within 1 year after the first brain injury and were retested. The postconcussion symptoms checklist, neuropsychological evaluations, and postural responses to visual field motion were recorded using a virtual reality environment.

RESULTS

All patients were asymptomatic at Day 10 of testing and were cleared for sport participation based on clinical symptoms resolution. Balance deficits, as evident by incoherence with visual field motion postural responses, were present at least 30 days after injury (P < 0.001). Most importantly, the rate of balance symptoms restoration was significantly reduced after a recurrent, second concussion (P < 0.001) compared with those after the first concussion.

CONCLUSION

The findings of this study confirm our previous research indicating the presence of long-term residual visual-motor disintegration in concussed individuals with normal neuropsychological measures. Most importantly, athletes with a history of previous concussion demonstrate significantly slower rates of recovery of neurological functions after the second episode of MTBI.