Effects of Environmental Demands on Locomotion After Traumatic Brain Injury

Exploring the challenges of avoiding collisions with virtual pedestrians using a dual-task paradigm in individuals with chronic moderate to severe traumatic brain injury

BACKGROUND

Individuals with a moderate-to-severe traumatic brain injury (m/sTBI), despite experiencing good locomotor recovery six months post-injury, face challenges in adapting their locomotion to the environment. They also present with altered cognitive functions, which may impact dual-task walking abilities. Whether they present collision avoidance strategies with moving pedestrians that are altered under dual-task conditions, however, remains unclear. This study aimed to compare between individuals with m/sTBI and age-matched control individuals: (1), the locomotor and cognitive costs associated with the concurrent performance of circumventing approaching virtual pedestrians (VRPs) while attending to an auditory-based cognitive task and; (2) gaze behaviour associated with the VRP circumvention task in single and dual-task conditions.

METHODOLOGY

Twelve individuals with m/sTBI (age = 43.3 ± 9.5 yrs; >6 mo. post injury) and 12 healthy controls (CTLs) (age = 41.8 ± 8.3 yrs) were assessed while walking in a virtual subway station viewed in a head-mounted display. They performed a collision avoidance task with VRPs, as well as auditory-based cognitive tasks (pitch discrimination and auditory Stroop), both under single and dual-task conditions. Dual-task cost (DTC) for onset distance of trajectory deviation, minimum distance from the VRP, maximum lateral deviation, walking speed, gaze fixations and cognitive task accuracy were contrasted between groups using generalized estimating equations.

RESULTS

In contrast to CTLs who showed locomotor DTCs only, individuals with m/sTBI displayed both locomotor and cognitive DTCs. While both groups walked slower under dual-task conditions, only individuals with m/sTBI failed to modify their onset distance of trajectory deviation and maintained smaller minimum distances and smaller maximum lateral deviation compared to single-task walking. Both groups showed shorter gaze fixations on the approaching VRP under dual-task conditions, but this reduction was less pronounced in the individuals with m/sTBI. A reduction in cognitive task accuracy under dual-task conditions was found in the m/sTBI group only.

CONCLUSION

Individuals with m/sTBI present altered locomotor and gaze behaviours, as well as altered cognitive performances, when executing a collision avoidance task involving moving pedestrians in dual-task conditions. Potential mechanisms explaining those alterations are discussed. Present findings highlight the compromised complex walking abilities in individuals with m/sTBI who otherwise present a good locomotor recovery.

Gait Impairment in Traumatic Brain Injury: A Systematic Review

Introduction: Gait impairment occurs across the spectrum of traumatic brain injury (TBI); from mild (mTBI) to moderate (modTBI), to severe (sevTBI). Recent evidence suggests that objective gait assessment may be a surrogate marker for neurological impairment such as TBI. However, the most optimal method of objective gait assessment is still not well understood due to previous reliance on subjective assessment approaches. The purpose of this review was to examine objective assessment of gait impairments across the spectrum of TBI. Methods: PubMed, AMED, OVID and CINAHL databases were searched with a search strategy containing key search terms for TBI and gait. Original research articles reporting gait outcomes in adults with TBI (mTBI, modTBI, sevTBI) were included. Results: 156 citations were identified from the search, of these, 13 studies met the initial criteria and were included into the review. The findings from the reviewed studies suggest that gait is impaired in mTBI, modTBI and sevTBI (in acute and chronic stages), but methodological limitations were evident within all studies. Inertial measurement units were most used to assess gait, with single-task, dual-task and obstacle crossing conditions used. No studies examined gait across the full spectrum of TBI and all studies differed in their gait assessment protocols. Recommendations for future studies are provided. Conclusion: Gait was found to be impaired in TBI within the reviewed studies regardless of severity level (mTBI, modTBI, sevTBI), but methodological limitations of studies (transparency and reproducibility) limit clinical application. Further research is required to establish a standardised gait assessment procedure to fully determine gait impairment across the spectrum of TBI with comprehensive outcomes and consistent protocols.

Executive function and relation to static balance metrics in chronic mild TBI: A LIMBIC-CENC secondary analysis

Introduction

Among patients with traumatic brain injury (TBI), postural instability often persists chronically with negative consequences such as higher fall risk. One explanation may be reduced executive function (EF) required to effectively process, interpret and combine, sensory information. In other populations, a decline in higher cognitive functions are associated with a decline in walking and balance skills. Considering the link between EF decline and reduction in functional capacity, we investigated whether specific tests of executive function could predict balance function in a cohort of individuals with a history of chronic mild TBI (mTBI) and compared to individuals with a negative history of mTBI.

Methods

Secondary analysis was performed on the local LIMBIC-CENC cohort (N = 338, 259 mTBI, mean 45 ± STD 10 age). Static balance was assessed with the sensory organization test (SOT). Hierarchical regression was used for each EF test outcome using the following blocks: (1) the number of TBIs sustained, age, and sex; (2) the separate Trail making test (TMT); (3) anti-saccade eye tracking items (error, latency, and accuracy); (4) Oddball distractor stimulus P300 and N200 at PZ and FZ response; and (5) Oddball target stimulus P300 and N200 at PZ and FZ response.

Results

The full model with all predictors accounted for between 15.2% and 21.5% of the variability in the balance measures. The number of TBI's) showed a negative association with the SOT2 score (p = 0.002). Additionally, longer times to complete TMT part B were shown to be related to a worse SOT1 score (p = 0.038). EEG distractors had the most influence on the SOT3 score (p = 0.019). Lastly, the SOT-composite and SOT5 scores were shown to be associated with longer inhibition latencies and errors (anti-saccade latency and error, p = 0.026 and p = 0.043 respectively).

Conclusions

These findings show that integration and re-weighting of sensory input when vision is occluded or corrupted is most related to EF. This indicates that combat-exposed Veterans and Service Members have greater problems when they need to differentiate between cues when vision is not a reliable input. In sum, these findings suggest that EF could be important for interpreting sensory information to identify balance challenges in chronic mTBI.

Relationship Between Cognition and Gait at 2- and 12-Months Post-Traumatic Brain Injury

Background: A common and debilitating challenge experienced by people with TBI is gait-associated mobility impairment and persisting cognitive impairments. Cognitive and physical impairments are often addressed independently during rehabilitation, however, increasing evidence links cognitive and motor processes more closely. Objectives: (1) To determine if correlations exist between measures of cognitive and gait recovery, post-TBI. (2) To investigate the predictive power of cognition at 2-months on gait outcomes at 12-months post-TBI. Methods: In this secondary, longitudinal study of cognitive and neural recovery, data from 93 participants admitted to an inpatient neurorehabilitation program were analyzed. Spatiotemporal gait variables [velocity, step time variability (STV), step length variability (SLV)] were collected along with cognitive variables [Trail Making Test-B (TMT-B), Digit Span-Forward (DS-F)]. Spearman's correlation coefficients were calculated between gait and cognitive variables. Multilinear and step wise regression analyses were calculated to determine predictive value of cognitive variables at 2-months on gait performance at 12-months-post TBI. Results: At 2-months post-injury, TMT-B was significantly correlated with gait velocity and STV; and DS-F was significantly correlated with velocity. At 12-months post-injury, TMT-B and DS-F was still significant correlated with velocity. TMT-B at 2-months was correlated with SLV and STV at 12-months; and DS-F correlated significantly with velocity. Regression models showed TMT-B at 2-months predicting STV, SLV, and velocity at 12-months. Conclusions: Significant associations and predictions between physical and cognitive recovery post-TBI were observed in this study. Future directions may consider a "neural internetwork" model as a salient rehabilitation approach in TBI that integrates physical and cognitive functions.

Effects of spatial working memory in balance during dual tasking in traumatic brain injury and healthy controls

OBJECTIVES

The aim of this research was to assess cognitive-motor interactions though dual tasks of working memory in patients with traumatic brain injury (TBI) and control subjects. Methods: Twenty patients with chronic TBI with good functional level and 19 matched healthy controls performed dual working memory tasks (1-back numeric and 1-back spatial (S)) while sitting, standing, and walking. The center of pressure (COP) displacement amplitude, cadence, and error percentage (PER) were recorded as dependent variables. Results: The results revealed main effects of Group (TBI, controls) (p = .011) and Task factors (Single, Dual Standing 1-back, Dual Standing 1-back (S); p = .0001) for the COP. Patients showed greater displacement than controls (p = .011), and an analysis of the Task factor showed a minor displacement for the dual 1-back (S) task compared with the 1-back and single task (p = .002 and p = .001, respectively). Conclusions: Postural control during both standing and walking improved during performance of the spatial working memory task. In the dual task, both patients and controls showed a postural prioritization as an adaptive response to the increase in cognitive demand.

Absence of Glia Maturation Factor Protects from Axonal Injury and Motor Behavioral Impairments after Traumatic Brain Injury

Traumatic brain injury (TBI) causes disability and death, accelerating the progression towards Alzheimer's disease and Parkinson's disease (PD). TBI causes serious motor and cognitive impairments, as seen in PD that arise during the period of the initial insult. However, this has been understudied relative to TBI induced neuroinflammation, motor and cognitive decline that progress towards PD. Neuronal ubiquitin-C-terminal hydrolase- L1 (UCHL1) is a thiol protease that breaks down ubiquitinated proteins and its level represents the severity of TBI. Previously, we demonstrated the molecular action of glia maturation factor (GMF); a proinflammatory protein in mediating neuroinflammation and neuronal loss. Here, we show that the weight drop method induced TBI neuropathology using behavioral tests, western blotting, and immunofluorescence techniques on sections from wild type (WT) and GMF-deficient (GMF-KO) mice. Results reveal a significant improvement in substantia nigral tyrosine hydroxylase and dopamine transporter expression with motor behavioral performance in GMF-KO mice following TBI. In addition, a significant reduction in neuroinflammation was manifested, as shown by activation of nuclear factor-kB, reduced levels of inducible nitric oxide synthase, and cyclooxygenase- 2 expressions. Likewise, neurotrophins including brain-derived neurotrophic factor and glial-derived neurotrophic factor were significantly improved in GMF-KO mice than WT 72 h post-TBI. Consistently, we found that TBI enhances GFAP and UCHL-1 expression and reduces the number of dopaminergic TH-positive neurons in WT compared to GMF-KO mice 72 h post-TBI. Interestingly, we observed a reduction of THpositive tanycytes in the median eminence of WT than GMF-KO mice. Overall, we found that absence of GMF significantly reversed these neuropathological events and improved behavioral outcome. This study provides evidence that PD-associated pathology progression can be initiated upon induction of TBI.

Clinical Utility and Analysis of the Run-Roll-Aim Task: Informing Return-to-Duty Readiness Decisions in Active-Duty Service Members

INTRODUCTION

The Assessment of Military Multitasking Performance (AMMP1) consists of six dual-task and multitask military-relevant performance-based assessments which were developed to provide assistance in making return-to-duty decisions after concussion or mild traumatic brain injury (mTBI.) The Run-Roll-Aim (RRA) task, one component of the AMMP, was developed to target vulnerabilities following mTBI including attention, visual function, dynamic stability, rapid transition, and vestibular function. One aim of this study was to assess the known-group and construct validity of the RRA, and additionally to further explore reliability limitations reported previously.

MATERIALS AND METHODS

A cross-sectional study consisting of 84 Active Duty service members in two groups (healthy control - HC and individuals experiencing persistent mTBI symptoms) completed neurocognitive tests and the RRA. The RRA task requires a high level of mobility and resembles military training activities in a maneuver that includes combat rolls, fast transitions, obstacle avoidance, and visual search. Observational and inertial sensor data were compared between groups and performance across four trial times was compared within groups. Correlations between RRA results and neurocognitive test scores were analyzed.

RESULTS

Simple observational measures (time, errors) did not differ between groups. Spectral power analysis of the inertial sensor data showed significant differences in motor performance between groups. Within group one-way ANOVAs showed that in HC trial 1, time was significantly different than trials 2,3 and 4 (F(3,47) = 4.60, p < 0.01, Tukey HSD p < 0.05) while the mTBI group showed no significant difference in time between trials. During testing individuals with mTBI were less likely to complete the multiple test trials or required additional rest between trials than HCs (χ2 = 10.78, p < 0.01). Small but significant correlations were seen with two neurocognitive tests of attention and RRA performance time.

CONCLUSION

While observational scores were not sensitive to group differences, inertial sensor data showed motor performance on the forward run, combat roll, and backward run differed significantly between groups. The RRA task appeared challenging and provoked symptoms in the mTBI group, causing 8 of 33 mTBI participants to stop the task or require additional rest between trials while none of the HC participants had to stop. Individuals with mTBI demonstrated slower learning of the complex motor sequence compared to HCs who had significant improvement after one trial of RRA. Complex novel training maneuvers like RRA may aid clinicians in informing return to duty decisions.

Physical Performance and Fall Risk in Persons With Traumatic Brain Injury

Injuries sustained from traumatic brain injury (TBI) culminate in both cognitive and neuromuscular deficits. Patients often progress to higher functioning on the Rancho continuum even while mobility deficits persist. Although prior studies have examined physical performance among persons with chronic symptoms of TBI, less is known about the relatively acute phase of TBI as patients prepare for rehabilitation discharge. The aims of this cross-sectional study were to (a) compare balance and gait performance in 20 ambulant persons with moderate to severe TBI who were nearing rehabilitation discharge with their age-matched controls and (b) describe performance with thresholds for fall risk and community navigation. During a designed task circuit, 40 participants (20 persons with TBI and 20 controls) performed the Timed Up and Go (TUG), gait velocity, and Walking and Remembering tests. Balance testing included the Fullerton Advanced Balance Scale (FABS) and instrumented Modified Clinical Test for Sensory Interaction in Balance (MCTSIB). Statistical analyses included analysis of covariance for group comparisons and a multivariate analysis of covariance for MCTSIB sway velocities with anthropometric controls. The TBI group (mean [ M] age = 42, standard deviation [ SD] =19.5 years; 70% males) performed significantly more poorly on all mobility tests ( p < .05) and their scores reflected a potential fall risk. Gait velocity was significantly slower for the TBI versus control group ( M = .96, SD = 2.6 vs. M = 1.5, SD = 2.2 m/s; p < .001), including TUG times ( M = 13.5, SD = 4.9 vs. M = 7.7, SD = 1.4; p < .001). TBI participants also demonstrated significantly greater sway velocity on all MCTSIB conditions ( p < .01) and lower performance on the FABS ( p < .001). Performance indices indicate potential fall risk and community navigation compromise for individuals with moderate to severe TBI. Physical performance scores support the need for continued interventions to optimize functional mobility upon discharge.

Gait and Conditioned Fear Impairments in a Mouse Model of Comorbid TBI and PTSD

STUDY OBJECTIVES

Traumatic brain injury (TBI) and posttraumatic stress disorder (PTSD) commonly cooccur. Approaches to research and treatment of these disorders have been segregated, despite overlapping symptomology. We and others have hypothesized that comorbid TBI + PTSD generates worse symptoms than either condition alone. We present a mouse model of comorbid TBI + PTSD to further explore this condition.

METHODS

A mouse model of TBI + PTSD was generated using the single prolonged stress (SPS) protocol in combination with the controlled cortical impact (CCI) protocol. This resulted in four experimental groups: control, TBI, PTSD, and TBI + PTSD. Behavioral phenotyping included gait analysis, contextual fear conditioning, acoustic startle response, and prepulse inhibition.

RESULTS

Mice in the TBI + PTSD group showed a significantly impaired gait compared to their counterparts with TBI alone as well as control mice. Mice in the TBI + PTSD group showed significantly impaired contextual fear recall compared to controls. Prepulse inhibition testing revealed intact acoustic startle and auditory sensory gating.

CONCLUSIONS

These results indicate that SPS paired with CCI in mice produces unique behavioral impairments in gait and fear recall that are not present in either condition alone. Further studies are underway to examine additional behavioral, physiological, and pathological phenotypes in this combined model of TBI + PTSD.

Walking speed changes in response to novel user-driven treadmill control

Implementing user-driven treadmill control in gait training programs for rehabilitation may be an effective means of enhancing motor learning and improving functional performance. This study aimed to determine the effect of a user-driven treadmill control scheme on walking speeds, anterior ground reaction forces (AGRF), and trailing limb angles (TLA) of healthy adults. Twenty-three participants completed a 10-m overground walking task to measure their overground self-selected (SS) walking speeds. Then, they walked at their SS and fastest comfortable walking speeds on an instrumented split-belt treadmill in its fixed speed and user-driven control modes. The user-driven treadmill controller combined inertial-force, gait parameter, and position based control to adjust the treadmill belt speed in real time. Walking speeds, peak AGRF, and TLA were compared among test conditions using paired t-tests (α = 0.05). Participants chose significantly faster SS and fast walking speeds in the user-driven mode than the fixed speed mode (p > 0.05). There was no significant difference between the overground SS walking speed and the SS speed from the user-driven trials (p < 0.05). Changes in AGRF and TLA were caused primarily by changes in walking speed, not the treadmill controller. Our findings show the user-driven treadmill controller allowed participants to select walking speeds faster than their chosen speeds on the fixed speed treadmill and similar to their overground speeds. Since user-driven treadmill walking increases cognitive activity and natural mobility, these results suggest user-driven treadmill control would be a beneficial addition to current gait training programs for rehabilitation.

Reliability and clinical feasibility of measuring dual-task gait in the inpatient rehabilitation setting following traumatic brain injury

Background: To prepare patients with traumatic brain injury (TBI) for discharge from inpatient rehabilitation, physical therapists may incorporate dual-task gait activities. Reliability of common dual-task measures for people with TBI in inpatient rehabilitation is undetermined. Our purpose was to assess inter-rater and intra-rater reliability and clinical feasibility of dual-task measures [Walking While Talking Test (WWTT), Modified Walking and Remembering Task (mWART), Timed Up and Go-cognitive (TUG-COG)] in inpatient rehabilitation for patients with TBI. Methods: A total of 22 individuals with TBI completing the dual-task measures (WWTT, Walking and Remembering Task (WART), and TUG-COG) in inpatient rehabilitation were rated concurrently by two physical therapists in a single testing session. Sessions were video recorded and rated by the same raters viewing the video 7-10 days later. Raters completed a survey assessing feasibility of conducting the dual-task measures in patients with TBI in inpatient rehabilitation. Data were analyzed by calculating ICC_(2,1) for inter-rater reliability and ICC_(3,1) for intra-rater reliability. Results: All dual-task measures (WWTT, mWART, TUG-COG) had excellent inter-rater and intra-rater reliability. Raters considered dual-task measures feasible for patients with TBI during inpatient rehabilitation. Conclusions: The WWTT, mWART, and TUG-COG have excellent reliability and appear clinically feasible for incorporation into clinical practice in inpatient rehabilitation following TBI.

Decomposition of leg movements during overground walking in individuals with traumatic brain injury

OBJECTIVE

Walking requires precise coordination of bilateral lower extremity motions at all joints. This ability can be affected by traumatic brain injury (TBI). The study investigated inter-joint coordination of lower extremities during overground walking after TBI.

METHODS

Ten individuals with post-injury ataxia, postural stability and gait abnormalities, as well as 10 sex- and age-matched control subjects were involved in the study. Participants walked at self-selected speed in three experimental conditions: normal walking without any additional task; walking with a narrow base of support, and walking while holding a cup full of water. Inter-joint coordination was analysed as the percentage of gait cycle during which the leg movement was decomposed with 0% indicating simultaneous motion of the two joints (i.e. hip-knee, knee-ankle, and hip-ankle) through the entire gait cycle or 100% indicating motion of only one joint. Decomposition was calculated for each pair of joints and for the left and right leg separately.

RESULTS

Participants with TBI showed greater decomposition indices and poorer inter-joint coordination respectively than control individuals for all joint pairs (p < 0.01). Walking with the narrower base of support or with a cup, increased movement decomposition in the TBI group, but not in the control group.

CONCLUSION

The results revealed post-injury gait impairment that manifests as decomposition of multi-joint motions of the lower extremities during overground walking.

Effects of walking on bilateral differences in spatial attention control: a cross-over design

Background

Walking requires a high attentional cost for balance control and interferes with the control of attention. However, it is unclear whether the performance of visual spatial attention control, which is one of the functions of attention control, is also decreased during walking. In addition, although previous studies have shown right-hemispheric dominance and lower ability of left side visual spatial attention control during sitting, it remains unknown whether walking accentuates bilateral differences in visual spatial attention control. We tested the hypothesis that walking interferes with visual spatial attention control on both sides and accentuates its bilateral differences.

Methods

Twenty healthy right-handed subjects (24.3 ± 2.0 years) participated in this study. Subjects performed a random stimulus–response compatibility (SRC) task during both sitting and walking situations. To evaluate the effects of walking, reaction time was measured on both sides for the two situations. In comparison to the both situations (sitting and walking), the amount of change of the SRC effect on both sides was used. In the comparing the bilateral difference (left and right), the difference of the SRC effect was evaluated in each situation. The paired t-test was applied to both comparisons for statistical analysis.

Results

The SRC effect on both sides during walking was significantly larger than during sitting (P < 0.05). In addition, walking significantly accentuated the bilateral differences in visual spatial attention control (P < 0.05).

Conclusions

These results suggest that walking affects the performance of visual spatial attention control on both sides and accentuates its bilateral differences. These results have implications for development of practice methods of gait disorder with higher brain dysfunction.

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.

Gait mechanics in patients with chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is characterized by the frequent association of disease outside the lung. The objective of this study was to determine the presence of biomechanical gait abnormalities in COPD patients compared to healthy controls while well rested and without rest.

METHODS

Patients with COPD (N = 17) and aged-matched, healthy controls (N = 21) walked at their self-selected pace down a 10-meter walkway while biomechanical gait variables were collected. A one-minute rest was given between each of the five collected trials to prevent tiredness (REST condition). Patients with COPD then walked at a self-selected pace on a treadmill until the onset of self-reported breathlessness or leg tiredness. Subjects immediately underwent gait analysis with no rest between each of the five collected trials (NO REST condition). Statistical models with and without covariates age, gender, and smoking history were used.

RESULTS

After adjusting for covariates, COPD patients demonstrated more ankle power absorption in mid-stance (P = 0.006) than controls during both conditions. Both groups during NO REST demonstrated increased gait speed (P = 0.04), stride length (P = 0.03), and peak hip flexion (P = 0.04) with decreased plantarflexion moment (P = 0.04) and increased knee power absorption (P = 0.04) as compared to REST. A significant interaction revealed that peak ankle dorsiflexion moment was maintained from REST to NO REST for COPD but increased for controls (P < 0.01). Stratifying by disease severity did not alter these findings, except that step width decreased in NO REST as compared to REST (P = 0.01). Standardized effect sizes of significant effects varied from 0.5 to 0.98.

CONCLUSIONS

Patients with COPD appear to demonstrate biomechanical gait changes at the ankle as compared to healthy controls. This was seen not only in increased peak ankle power absorption during no rest but was also demonstrated by a lack of increase in peak ankle dorsiflexion moment from the REST to the NO REST condition as compared to the healthy controls. Furthermore, a wider step width has been associated with fall risk and this could account for the increased incidence of falls in patients with COPD.

Effects of traumatic brain injury on locomotor adaptation

BACKGROUND AND PURPOSE

Locomotor adaptation is a form of short-term learning that enables gait modifications and reduces movement errors when the environment changes. This adaptation is critical for community ambulation for example, when walking on different surfaces. While many individuals with traumatic brain injury (TBI) recover basic ambulation, less is known about recovery of more complex locomotor skills, like adaptation. The purpose of this study was to investigate how TBI affects locomotor adaptation.

METHODS

Fourteen adults with TBI and 11 nondisabled comparison participants walked for 15 minutes on a split-belt treadmill with 1 belt moving at 0.7 m/s, and the other at 1.4 m/s. Subsequently, aftereffects were assessed and de-adapted during 15 minutes of tied-belt walking (both belts at 0.7 m/s).

RESULTS

Participants with TBI showed greater asymmetry in interlimb coordination on split-belts than the comparison group. Those with TBI did not adapt back to baseline symmetry, and some individuals did not store significant aftereffects. Greater asymmetry on split-belts and smaller aftereffects were associated with greater ataxia.

DISCUSSION

Participants with TBI were more perturbed by walking on split-belts and showed some impairment in adaptation. This suggests a reduced ability to learn a new form of coordination to compensate for environmental changes. Multiple interacting factors, including cerebellar damage and impairments in higher-level cognitive processes, may influence adaptation post-TBI.

CONCLUSIONS

Gait adaptation to novel environment demands is impaired in persons with chronic TBI and may be an important skill to target in rehabilitation.

VIDEO ABSTRACT AVAILABLE

(See Video, Supplemental Digital Content 1, http://links.lww.com/JNPT/A74) for more insights from the authors.

The effect of cognitive task complexity on gait stability in adolescents following concussion

Concussion has been reported to result in disturbances to motor and cognitive functions. One way to examine these disturbances is through a dual-task assessment. Many secondary cognitive tasks have been proposed as appropriate tools during concussion assessment; however, task complexity has not been compared within a dual-task investigation. The purpose of this study was to prospectively examine how gait balance control was affected by three secondary cognitive tasks of varying complexity following concussion. Forty-six adolescents completed a dual-task walking protocol which included walking without any cognitive task (WALK), walking while completing a single auditory Stroop (SAS), multiple auditory Stroop (MAS), and a question and answer task (Q&A). Those who sustained a concussion (n = 23, mean age 15.4 ± 1.3 years) reported to the laboratory within 72 h of injury and in the following time increments: 1 week, 2 weeks, 1 month, and 2 months post-injury. Twenty-three healthy control subjects (mean age 15.4 ± 1.3 years), individually matched to each concussion subject, completed the same protocol in similar time increments. The concussion group demonstrated greater total center of mass (COM) medial/lateral displacement in the MAS and Q&A conditions compared with the control group. The concussion group also displayed the greatest peak COM anterior velocity in the least complex condition (WALK), and a significant decrease was observed as task complexity increased (SAS > MAS > Q&A). These findings indicate that gait balance control may be affected by task complexity following concussion and represent a way to identify motor recovery following concussion.

Remote brain network changes after unilateral cortical impact injury and their modulation by acetylcholinesterase inhibition

We explored whether cerebral cortical impact injury (CCI) effects extend beyond direct lesion sites to affect remote brain networks, and whether acetylcholinesterase (AChE) inhibition elicits discrete changes in functional activation of motor circuits following CCI. Adult male rats underwent unilateral motor-sensory CCI or sham injury. Physostigmine (AChE inhibitor) or saline were administered subcutaneously continuously via implanted minipumps (1.6 micromoles/kg/day) for 3 weeks, followed by cerebral perfusion mapping during treadmill walking using [(14)C]-iodoantipyrine. Quantitative autoradiographs were analyzed by statistical parametric mapping and functional connectivity (FC) analysis. CCI resulted in functional deficits in the ipsilesional basal ganglia, with increased activation contralesionally. Recruitment was also observed, especially contralesionally, of the red nucleus, superior colliculus, pedunculopontine tegmental nucleus, thalamus (ventrolateral n., central medial n.), cerebellum, and sensory cortex. FC decreased significantly within ipsi- and contralesional motor circuits and between hemispheres, but increased between midline cerebellum and select regions of the basal ganglia within each hemisphere. Physostigmine significantly increased functional brain activation in the cerebellar thalamocortical pathway (midline cerebellum→ventrolateral thalamus→motor cortex), subthalamic nucleus/zona incerta, and red nucleus and bilateral sensory cortex. In conclusion, CCI resulted in increased functional recruitment of contralesional motor cortex and bilateral subcortical motor regions, as well as recruitment of the cerebellar-thalamocortical circuit and contralesional sensory cortex. This phenomenon, augmented by physostigmine, may partially compensate motor deficits. FC decreased inter-hemispherically and in negative, but not positive, intra-hemispherical FC, and it was not affected by physostigmine. Circuit-based approaches into functional brain reorganization may inform future behavioral or molecular strategies to augment targeted neurorehabilitation.

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.

Dual-task training for balance and mobility in a person with severe traumatic brain injury: a case study

BACKGROUND AND PURPOSE

Attentional impairments following severe traumatic brain injury (TBI) are common and can lead to decreased functional mobility and balance, as well as deficits in previously automatic movements such as walking and stair climbing. The purpose of this case study was to determine the feasibility and potential value of incorporating a cognitive-motor dual-task training program into physical therapy for a patient with a severe TBI.

CASE DESCRIPTION

The patient was a 26-year-old woman who sustained a severe TBI during a motor vehicle accident 46 days prior to physical therapy evaluation. On the 8-level Rancho Los Amigos Cognitive Function Scale, her functioning was classified as level IV. She had impairments in attention, functional mobility, and balance, all of which limited her ability to participate in activities of daily living.

INTERVENTION

: Physical therapy was provided over 26 days within the inpatient rehabilitation setting. Interventions included mobility tasks such as walking, balancing, and stair climbing. Mobility training was paired with specific secondary cognitive and motor tasks.

OUTCOMES

Dual-task training may have contributed to improvements on outcome measures designed to test divided attention including the Walking While Talking Test and Trail Making Test and a greater rate of improvement in walking speed and time to descend stairs when compared to the baseline phase.

DISCUSSION

Addition of cognitive-motor dual-task training to standard physical therapy in the inpatient rehabilitation setting appears to be feasible and may have value for improving function in individuals with severe TBI.

VIDEO ABSTRACT AVAILABLE

(see Video, Supplemental Digital Content 1, http://links.lww.com/JNPT/A41) for more insights from the authors.

Dual-task effect on gait balance control in adolescents with concussion

OBJECTIVE

To prospectively and longitudinally examine how concussion affects gait balance control in adolescents during single- and dual-task walking.

DESIGN

Cohort, prospective, repeated-measures design.

SETTING

Motion analysis laboratory.

PARTICIPANTS

Adolescents (N=20) identified as suffering a concussion were matched with healthy control subjects (N=20) and tested 5 times across a 2-month period after injury.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Gait temporal-distance parameters included average walking speed, step length, and step width; whole body center of mass (COM) parameters included medial/lateral displacement and peak COM medial/lateral and anterior velocities; dual-task cost, which was defined as percent change from single- to dual-task conditions; and Stroop test accuracy.

RESULTS

No between-group differences were observed for step length and step width. The dual-task cost for average walking speed for subjects with concussion was greater than control subjects across the 2-month testing period (main effect of group P=.019), as was the dual-task costs for peak anterior COM velocity (main effect of group P=.017) and total COM medial/lateral displacement (main effect of group P=.013). The total COM medial/lateral displacement (group × task interaction P=.006) and peak COM medial/lateral velocity (main effect of group P=.027; main effect of task P=.01) were significantly greater in subjects with concussion compared with control subjects during dual-task walking. Subjects with concussion were significantly less accurate than controls on the Stroop test (main effect of group P=.004).

CONCLUSIONS

The findings suggest that concussion affects the ability of adolescents to control body posture during gait up to 2 months after injury. Furthermore, dual-task paradigms may provide additional useful information in the clinical assessment and recovery of concussion.

Walking Stroop carpet: an innovative dual-task concept for detecting cognitive impairment

Background

Several studies have reported the potential value of the dual-task concept during locomotion in clinical evaluation because cognitive decline is strongly associated with gait abnormalities. However, current dual-task tests appear to be insufficient for early diagnosis of cognitive impairment.

Methods

Forty-nine subjects (young, old, with or without mild cognitive impairment) underwent cognitive evaluation (Mini-Mental State Examination, Frontal Assessment Battery, five-word test, Stroop, clock-drawing) and single-task locomotor evaluation on an electronic walkway. They were then dual-task-tested on the Walking Stroop carpet, which is an adaptation of the Stroop color–word task for locomotion. A cluster analysis, followed by an analysis of variance, was performed to assess gait parameters.

Results

Cluster analysis of gait parameters on the Walking Stroop carpet revealed an interaction between cognitive and functional abilities because it made it possible to distinguish dysexecutive cognitive fragility or decline with a sensitivity of 89% and a specificity of 94%. Locomotor abilities differed according to the group and dual-task conditions. Healthy subjects performed less well on dual-tasking under reading conditions than when they were asked to distinguish colors, whereas dysexecutive subjects had worse motor performances when they were required to dual task.

Conclusion

The Walking Stroop carpet is a dual-task test that enables early detection of cognitive fragility that has not been revealed by traditional neuropsychological tests or single-task walking analysis.

Physical therapy recommendations for service members with mild traumatic brain injury

Mild traumatic brain injuries (MTBIs) are of increasing concern in both the military and civilian populations as the potential long-term effects and costs of such injuries are being further recognized. Injuries from conflicts in Afghanistan and Iraq have increased public awareness and concern for TBI. The Proponency Office for Rehabilitation and Reintegration, Office of the Surgeon General, US Army tasked a team of physical and occupational therapists to assemble evidence-informed guidelines for assessment and intervention specific to MTBI. Given the paucity of specific guidelines for physical therapy related to MTBI, we focused on literature that dealt with the specific problem area or complaint of the Service member following MTBI. Recommendations, characterized as practice standards or practice options based on strength of evidence, are provided relative to patient/client education, activity intolerance, vestibular dysfunction, high-level balance dysfunction, posttraumatic headache, temporomandibular disorder, attention and dual-task performance deficits, and participation in exercise. While highlighting the need for additional research, this work can be considered a starting point and impetus for the development of evidence-based practice in physical therapy for our deserving Service members.

Racial differences in employment outcome after traumatic brain injury at 1, 2, and 5 years postinjury

Gary KW, Arango-Lasprilla JC, Ketchum JM, Kreutzer JS, Copolillo A, Novack TA, Jha A. Racial differences in employment outcome after traumatic brain injury at 1, 2, and 5 years postinjury.

OBJECTIVES

To examine racial differences in competitive employment outcomes at 1, 2, and 5 years after traumatic brain injury (TBI) and to determine whether changes in not competitive employment rates over time differ between blacks and whites with TBI after adjusting for demographic and injury characteristics.

DESIGN

Retrospective cohort study.

SETTING

Sixteen TBI Model System Centers.

PARTICIPANTS

Blacks (n=615) and whites (n=1407) with moderate to severe TBI.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

Employment status dichotomized as competitively employed versus not competitively employed.

RESULTS

After adjusting for demographic and injury characteristics, repeated-measures logistic regression indicated that (1) the odds of not being competitively employed were significantly greater for blacks than whites regardless of the follow-up year (all P<.001); (2) the odds of not being competitively employed declined significantly over time for each race (P< or =.004); and (3) changes over time in the odds of not being competitively employed versus being competitively employed were not different between blacks and whites (P=.070). In addition, age, discharge FIM and Disability Rating Scale, length of stay in acute and rehabilitation, preinjury employment, sex, education, marital status, and cause of injury were significant predictors of employment status postinjury.

CONCLUSIONS

Short- and long-term employment is not favorable for people with TBI regardless of race; however, blacks fare worse in employment outcomes compared with whites. Rehabilitation professionals should work to improve return to work for all persons with TBI, with special emphasis on addressing specific needs of blacks.

Can measures of cognitive function predict locomotor behaviour in complex environments following a traumatic brain injury?

PRIMARY OBJECTIVE

To determine the relationships between clinical measures of executive function and attention, and laboratory measures of anticipatory locomotor adaptations with dual tasks following a TBI.

METHODS AND PROCEDURES

Ten people with moderate or severe TBI were compared to 10 healthy subjects for neuropsychological measures in the clinic, as well as locomotor patterns and reading time in the laboratory for adapted Stroop tasks (Bar and Word) during unobstructed and obstructed walking.

MAIN OUTCOMES AND RESULTS

As previously found 1 (Vallee M, McFadyen BJ, Swaine B, Doyon J, Cantin JF, Dumas D. Effects of environmental demands on locomotion after traumatic brain injury. Archives of Physical Medicine Rehabilitation 2006;87:806--813) during the locomotor activities, subjects with TBI walked slower, had higher clearance margins and took longer to read during the Stroop tasks than healthy subjects. In general, subjects with TBI also showed deficits in executive functions and attention. Significant relationships were specifically observed between scores on Trail Making B and clearance margins for subjects with TBI, but not for healthy subjects. Alternatively, significant relationships between clinical scores on Stroop and dual task Stroop reading times were obtained for healthy subjects but not for subjects with TBI.

CONCLUSIONS

These results suggest that measures of executive functioning and attention may be associated to locomotor behaviour in complex environments following a moderate to severe TBI.

Assessing gait impairment following experimental traumatic brain injury in mice

Although gait disturbance is frequently documented among patients with traumatic brain injury (TBI), gait data from animal models of TBI are lacking. To determine the effect of TBI on gait function in adult mice, we assessed gait changes following unilateral controlled cortical impact (CCI) using a computer-assisted automated gait analysis system. Three days after CCI, intensity, area or width of paw contact were significantly decreased in forepaw(s) while the relative paw placement between the fore and hindpaws altered, suggesting that TBI affected sensorimotor status and reduced interlimb coordination. Similar to TBI patients, CCI decreased gait velocity and stride length, and prolonged stance and swing phase in mice. Following CCI, step pattern was also changed with increasing use in the ipsilateral-diagonal limb sequence. Our results indicate that gait analysis provides great insight into both spatial and temporal aspects of limb function changes during overground locomotion in quadruped species with head injury that are valuable for the purpose of treatment and rehabilitation. Our study also provides additional functional validation for the established mouse CCI model that is relevant to human head injury.

Bilateral claudication results in alterations in the gait biomechanics at the hip and ankle joints

Claudication is the most common symptomatic manifestation of peripheral arterial disease (PAD), producing significant ambulatory compromise. The purpose of this study was to use advanced biomechanical gait analysis to determine the gait alterations occurring in claudicating patients both before and after onset of claudication pain in their legs. Hip, knee, and ankle joint moments were measured in claudicating patients (age: 64.46+/-8.47 years; body mass: 80.70+/-12.64kg; body height: 1.72+/-0.08m) and were compared to gender-age-body mass-height-matched healthy controls (age 66.27+/-9.22 years; body mass: 77.89+/-10.65kg; body height: 1.74+/-0.08m). The claudicating patients were evaluated both before (pain-free (PF) condition) and after (pain condition) onset of claudication pain in their legs. Thirteen symptomatic PAD patients (26 claudicating limbs) with bilateral intermittent claudication (IC) and 11 healthy controls (22 control limbs) were tested during level walking at their self-selected speed. Compared to controls, PAD hip and ankle joints demonstrated significant angular kinematics and net internal moment changes. Alterations were present both in PF and pain conditions with several of them becoming worse in the pain condition. Both PF and pain conditions resulted in significantly reduced peak hip extensor moment (5.62+/-1.40 and 5.63+/-1.33% BWxBH, respectively) during early stance as compared to controls (7.53+/-1.16% BWxBH). In the pain condition, PAD patients had a significantly reduced ankle plantar flexor moment (7.56+/-1.41% BWxBH) during late stance as compared to controls (8.65+/-1.27% BWxBH). Furthermore, when comparing PF to pain conditions, there was a decreased peak plantar flexor moment (PF condition: 8.23+/-1.37 vs. pain condition: 7.56+/-1.41% BWxBH) during late stance. The findings point to a weakness in the posterior compartment muscles of the hip and calf as being the key factor underlying the PAD gait adaptations. Our findings establish a detailed baseline description of the changes present in PAD patient's joint angles and moments during walking. Since IC is primarily a gait disability, better understanding of the abnormalities in joint and muscle function will enhance our understanding of the gait impairment and may lead to novel, gait-specific treatments.

The role of executive function and attention in gait

Until recently, gait was generally viewed as a largely automated motor task, requiring minimal higher-level cognitive input. Increasing evidence, however, links alterations in executive function and attention to gait disturbances. This review discusses the role of executive function and attention in healthy walking and gait disorders while summarizing the relevant, recent literature. We describe the variety of gait disorders that may be associated with different aspects of executive function, and discuss the changes occurring in executive function as a result of aging and disease as well the potential impact of these changes on gait. The attentional demands of gait are often tested using dual tasking methodologies. Relevant studies in healthy adults and patients are presented, as are the possible mechanisms responsible for the deterioration of gait during dual tasking. Lastly, we suggest how assessments of executive function and attention could be applied in the clinical setting as part of the process of identifying and understanding gait disorders and fall risk.

Effects of an attention demanding task on dynamic stability during treadmill walking

Background

People exhibit increased difficulty balancing when they perform secondary attention-distracting tasks while walking. However, a previous study by Grabiner and Troy (J. Neuroengineering Rehabil., 2005) found that young healthy subjects performing a concurrent Stroop task while walking on a motorized treadmill exhibited decreased step width variability. However, measures of variability do not directly quantify how a system responds to perturbations. This study re-analyzed data from Grabiner and Troy 2005 to determine if performing the concurrent Stroop task directly affected the dynamic stability of walking in these same subjects.

Methods

Thirteen healthy volunteers walked on a motorized treadmill at their self-selected constant speed for 10 minutes both while performing the Stroop test and during undisturbed walking. This Stroop test consisted of projecting images of the name of one color, printed in text of a different color, onto a wall and asking subjects to verbally identify the color of the text. Three-dimensional motions of a marker attached to the base of the neck (C5/T1) were recorded. Marker velocities were calculated over 3 equal intervals of 200 sec each in each direction. Mean variability was calculated for each time series as the average standard deviation across all strides. Both "local" and "orbital" dynamic stability were quantified for each time series using previously established methods. These measures directly quantify how quickly small perturbations grow or decay, either continuously in real time (local) or discretely from one cycle to the next (orbital). Differences between Stroop and Control trials were evaluated using a 2-factor repeated measures ANOVA.

Results

Mean variability of trunk movements was significantly reduced during the Stroop tests compared to normal walking. Conversely, local and orbital stability results were mixed: some measures showed slight increases, while others showed slight decreases. In many cases, different subjects responded differently to the Stroop test. While some of our comparisons reached statistical significance, many did not. In general, measures of variability and dynamic stability reflected different properties of walking dynamics, consistent with previous findings.

Conclusion

These findings demonstrate that the decreased movement variability associated with the Stroop task did not translate to greater dynamic stability.

Multiple-task walking training in people with mild to moderate Parkinson's disease: a pilot study

Objective: To determine whether multiple-task training of walking is feasible and worthwhile in people with mild to moderate Parkinson's disease.

Design: Baseline-controlled pilot study with three-week baseline, training and retention phases.

Setting: University research laboratory.

Subjects: Five people aged 61 ±8 years with mild to moderate Parkinson's disease (Hoehn and Yahr stages II—III).

Interventions: Multiple-task training was performed for 30 minutes once a week during the three-week training phase.

Main measures: Participants were tested and trained during the `on' phase

of medication. Feasibility of training was examined using 10 cm visual analogue scales to measure participant perception of mental fatigue, physical fatigue, difficulty, anxiety and confidence. Walking velocity, stride length and cadence under multiple-task conditions were measured.

Results: Participants reported low levels of mental fatigue, physical fatigue, difficulty and anxiety as well as high levels of confidence associated with multiple-task training. No adverse effects of training were reported. Multiple-task walking velocity increased by 0.09 ± 0.06 m/s (95% confidence interval (CI) 0.02 to 0.16) between the baseline and training phase and this increase was maintained in the retention phase.

Conclusion: Multiple-task training is feasible in people with mild to moderate Parkinson's disease. The data suggest sustained benefits on multiple-task walking velocity are possible. A randomized controlled trial of multiple-task training efficacy is warranted.

Recovery of cognitive and dynamic motor function following concussion

OBJECTIVE

Neuropsychological testing has been advocated as an important tool of proper post-concussion management. Although these measures provide information that can be used in the decision of when to return an individual to previous levels of physical activity, they provide little data on motor performance following injury. The purpose of this investigation was to examine the relationship between measures of dynamic motor performance and neuropsychological function following concussion over the course of 28 days.

METHODS

Participants completed two experimental protocols: gait stability and neuropsychological testing. The gait stability protocol measured whole-body centre of mass motion as subjects walked under conditions of divided and undivided attention. Neuropsychological testing consisted of a computerised battery of tests designed to assess memory, reaction time, processing speed and concussion symptoms. Correlation coefficients were computed between all neuropsychological and gait variables and comparisons of neuropsychological and gait stability post-concussion recovery curves were assessed.

RESULTS

Dynamic motor tasks, such as walking under varying conditions of attention, are complex and demanding undertakings, which require a longer recovery time following a concussion than cognitive measures. Little statistical relationship was found between the neuropsychological and gait variables, and the recovery curves of neuropsychological and gait domains were observed to be independent.

CONCLUSIONS

In order to fully examine the effects of concussion and determine the optimal time for a safe return to activity, a multi-factorial approach, including both cognitive and motor tasks, should be employed.