David R. Howell

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.

Effects of Concussion on Attention and Executive Function in Adolescents

BACKGROUND Head trauma in adolescents has been linked with deficits in attention and executive function that can compromise the performance of everyday tasks. Although previous research has examined this issue using computerized neuropsychological testing, little work has been done using laboratory-based measurements of attention and executive function in this population. A longitudinal analysis of recovery patterns of these measures among adolescents is central to understanding the effects of concussions across the age spectrum. PURPOSE This study prospectively and longitudinally examined laboratory-based measures of attention and executive function in concussed adolescents sequentially during a 2-month period after injury. METHODS Two measures of attention and executive function, the Attentional Network Test and the Task-Switching Test, were administered to 20 concussed adolescents within 72 h postinjury as well as at 1 wk, 2 wk, 1 month, and 2 months postinjury. Twenty healthy, matched control subjects were similarly assessed at the same time intervals. Data were analyzed by two-way, mixed-effects ANOVA to determine the effect of group and time on the dependent variables. RESULTS Compared with control subjects, the concussed group exhibited a significantly greater switch cost on the Task-Switching Test (P = 0.038, mean difference value = 38 ms) and a significantly greater reaction time for the Attentional Network Test conflict effect component (P = 0.015, mean difference value = 34 ms) for up to 2 months after injury. CONCLUSIONS Concussed adolescents have difficulty recovering executive function after injury and may require extended recuperation time before full recovery is achieved. Evaluations focusing on attention and executive function can be useful additions in the assessment and follow-up after head injury.

Original articleDual-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.

Return to Activity after Concussion Affects Dual-task Gait Balance Control Recovery

BACKGROUND Recent work has identified deficits in dual-task gait balance control for up to 2 months after adolescent concussion; however, how resumption of preinjury physical activities affects recovery is unknown. PURPOSE The objective of this study is to examine how return to activity (RTA) affects recovery from concussion on measures of symptom severity, cognition, and balance control during single-task and dual-task walking. METHODS Nineteen adolescents with concussion who returned to preinjury activity within 2 months after injury and 19 uninjured, matched controls completed symptom inventories, computerized cognitive testing, and single-task and dual-task gait analyses. Concussion participants were assessed at five time points: within 72 h, 1 wk, 2 wk, 1 month, and 2 months postinjury. Control participants were assessed at the same time points as their matched concussion counterparts. RTA day was documented as the postinjury day in which physical activity participation was allowed. The effect of returning to physical activity was assessed by examining the percent change on each dependent variable across time before and directly after the RTA. Data were analyzed by two-way mixed effects ANOVAs. RESULTS After the RTA day, concussion participants significantly increased their total center-of-mass medial/lateral displacement (P = 0.009, ηp = .175) and peak velocity (P = 0.048, ηp = 0.104) during dual-task walking when compared with pre-RTA data, whereas no changes for the concussion group or between groups were detected on measures of single-task walking, forward movement, or cognition. CONCLUSIONS Adolescents with concussion displayed increased center-of-mass medial/lateral displacement and velocity during dual-task walking after RTA, suggesting a regression of recovery in gait balance control. This study reinforces the need for a multifaceted approach to concussion management and continued monitoring beyond the point of clinical recovery.

Adolescents Demonstrate Greater Gait Balance Control Deficits After Concussion Than Young Adults

Background: Age has been described as a factor that affects recovery after concussion. The recommended management protocol is to treat adolescents in a more cautious manner than adults. However, few studies have prospectively and longitudinally assessed the way these age groups perform on motor tasks after concussion. Purpose: To examine dual-task gait balance control deficits after concussion in a group of adolescents and young adults in reference to matched control subjects within 72 hours of injury and throughout 2 months after injury. Study Design: Cohort study; Level of evidence, 2. Methods: Adolescents and young adults who sustained a concussion and individually matched controls completed a whole-body motion gait analysis while simultaneously performing a cognitive task. Subjects with concussion reported to the laboratory within 72 hours after injury and at the following time points: 1 week, 2 weeks, 1 month, and 2 months after injury. Control subjects completed the same protocol at similar time points. Gait balance control measurements included whole-body center-of-mass (COM) medial-lateral displacement/velocity and anterior velocity. Results: A total of 38 subjects with concussion, 19 young adults (mean ± SD age, 20.3 ± 2.4 years) and 19 adolescents (mean ± SD age, 15.1 ± 1.1 years), and 38 individually matched control subjects were tested. Within 72 hours of injury, adolescents displayed significantly greater COM medial-lateral displacement (P = .001) and peak velocity (P = .001) relative to their control group, and the young adult concussion group displayed significantly less peak COM anterior velocity than their control group (P = .01). Across the 2 months of testing, adolescents with concussion displayed significantly greater total COM medial-lateral displacement than did adolescent controls (P = .001), while young adults with concussion did not significantly differ from their matched controls (P = .07). Conclusion: An examination of gait balance control during dual-task walking revealed that after concussion, in reference to matched controls, adolescents demonstrated greater gait balance control deficits than did young adults initially and throughout the 2-month postinjury period, supporting the recommendation of conservative management for adolescents after concussion.

Monitoring recovery of gait balance control following concussion using an accelerometer

Despite medical best-practice recommendations, no consistent standard exists to systematically monitor recovery from concussion. Studies utilizing camera-based systems have reported center-of-mass (COM) motion control deficits persisting in individuals with concussion up to two months post-injury. The use of an accelerometer may provide an efficient and sensitive method to monitor COM alterations following concussion that can be employed in clinical settings. This study examined: (1) frontal/sagittal plane acceleration characteristics during dual-task walking for individuals with concussion and healthy controls; and (2) the effectiveness of utilizing acceleration characteristics to classify concussed and healthy individuals via receiver operating characteristic (ROC) curve analyses. Individuals with concussion completed testing within 72 h as well as 1 week, 2 weeks, 1 month, and 2 months post-injury. Control subjects completed the same protocol in similar time increments. Participants walked and simultaneously completed a cognitive task while wearing an accelerometer attached to L5. Participants with concussion walked with significantly less peak medial-lateral acceleration during 55-75% gait cycle (p=0.04) throughout the testing period compared with controls. Moderate levels of sensitivity and specificity were found at the 72 h and 1 week testing times (sensitivity=0.70, specificity=0.71). ROC analysis revealed significant AUC values at the 72 h (AUC=0.889) and two week (AUC=0.810) time points. Accelerometer-derived measurements may assist in detecting frontal plane control deficits during dual-task walking post-concussion, consistent with camera-based studies. These initial findings demonstrate potential for using accelerometry as a tool for clinicians to monitor gait balance control following concussion.

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

Abstract Primary objective: To evaluate excitability and inhibition of the motor cortex acutely and longitudinally following mild traumatic brain injury (mTBI). Research design: A longitudinal paired case-control design was used to examine cortical excitability and inhibition in 15 adults who had sustained an mTBI (mean age = 20.8 ± 1.2 years) and 15 matched control participants (mean age = 21.1 ± 1.3 years). Methods and procedures: Participants visited the lab within 72 hours of injury and again at 1, 2, 4 and 8 weeks post-injury. During each visit, transcranial magnetic stimulation was used to examine resting motor threshold (RMT), motor evoked potential peak-to-peak amplitude (MEPamp) and cortical silent period (CSP) duration of the first dorsal interosseous muscle. Main outcomes and results: There were no differences between groups in RMT (p = 0.10) or MEPamp (p = 0.22) at 72 hours post-injury or across the 2-month testing period (p ≥ 0.68), indicating similar cortical excitability. However, the CSP duration was higher in individuals with mTBI, indicating greater intra-cortical inhibition compared with the control group at 72 hours post-injury (p = 0.03) and throughout the 2 months of recovery (p = 0.009). Conclusions: mTBI appeared to have little effect on cortical excitability, but an acute and long-lasting effect on intra-cortical inhibition.

Initial somatic symptoms are associated with prolonged symptom duration following concussion in adolescents.

To determine which initial postinjury symptom domains are independently associated with symptoms lasting >28 days in youth athletes who sustained sport‐related concussions.

Physical Activity Level and Symptom Duration Are Not Associated After Concussion

Background: Physical rest after a concussion has been described as a key component in the management of the injury. Evidence supporting this recommendation, however, is limited. Purpose: To examine the association between physical activity and symptom duration in a cohort of patients after a concussion. Study Design: Cohort study; Level of evidence, 2. Methods: This study included 364 patients who were diagnosed with a concussion, were seen by a physician within 3 weeks of injury, and completed a questionnaire at the initial clinic visit. The questionnaire assessed the postconcussion symptom scale (PCSS) score, previous number of concussions, presence of the loss of consciousness or amnesia at the time of injury, and prior treatment for headaches. During each follow-up clinic visit, physical activity level was self-reported. A Cox proportional hazard model was constructed to determine the association between symptom duration, initial clinic visit responses, and self-reported physical activity level after the injury. Results: Study participants ranged in age from 8 to 27 years (mean age, 15.0 years) and had sustained a mean of 0.8 prior concussions; 222 patients (61%) were male. On initial examination, the mean PCSS score was 34.7. The mean symptom duration was 48.9 days after the injury. Among the variables included in the model, initial PCSS score and female sex were independently associated with symptom duration, while physical activity level after the injury was not. For participants aged between 13 and 18 years, however, higher levels of physical activity after the injury were associated with a shorter symptom duration. Conclusion: Results from this study indicate that physical activity after the injury may not be universally detrimental to the recovery of concussion symptoms.

Single-task and dual-task gait among collegiate athletes of different sport classifications: Implications for concussion management.

Gait impairments have been documented following sport-related concussion. Whether preexisting gait pattern differences exist among athletes who participate in different sport classifications, however, remains unclear. Dual-task gait examinations probe the simultaneous performance of everyday tasks (ie, walking and thinking), and can quantify gait performance using inertial sensors. The purpose of this study was to compare the single-task and dual-task gait performance of collision/contact and noncontact athletes. A group of collegiate athletes (n = 265) were tested before their season at 3 institutions (mean age= 19.1 ± 1.1 years). All participants stood still (single-task standing) and walked while simultaneously completing a cognitive test (dual-task gait), and completed walking trials without the cognitive test (single-task gait). Spatial-temporal gait parameters were compared between collision/contact and noncontact athletes using MANCOVAs; cognitive task performance was compared using ANCOVAs. No significant single-task or dual-task gait differences were found between collision/contact and noncontact athletes. Noncontact athletes demonstrated higher cognitive task accuracy during single-task standing (P = .001) and dual-task gait conditions (P = .02) than collision/contact athletes. These data demonstrate the utility of a dual-task gait assessment outside of a laboratory and suggest that preinjury cognitive task performance during dual-tasks may differ between athletes of different sport classifications.