The effects of unilateral step training and conventional treadmill training on gait asymmetry in patients with chronic stroke

BACKGROUND

Step length asymmetry is common after stroke. Unilateral step training (UST) can improve step length asymmetry for patients who take a longer step with their paretic leg (P-long). UST has not been tested with patients who take a shorter step with their paretic leg (P-short).

RESEARCH QUESTION

Does training patients according to the direction of their asymmetry improve step length asymmetry?

METHODS

Adults 18 years and older with asymmetrical gait at least 6 months post-stroke completed three 20 min treadmill training sessions at least 48 h apart: Conventional treadmill; UST with the non-paretic leg stationary on the side of the treadmill and the paretic leg stepping on the moving treadmill belt (P-stepping); and UST with the paretic leg stationary on the side of the treadmill and the non-paretic leg stepping on the moving belt (NP-stepping). Spatiotemporal gait parameters before, immediately, 10 min and 30 min after training were recorded at self-selected and fastest walking pace. Asymmetry values for each parameter were calculated. RmANOVAs were used to investigate the effects of training type on spatiotemporal parameters and paired-samples t-tests used to investigate potential contributors to training effects on asymmetry.

RESULTS

Twenty participants (16 male, median age 65 (43-80) years; 11 P-long, 9 P-short) were included. Improvements in step length asymmetry were observed immediately after both Conventional (9.1 %; 95 % CI 2.7-15.4%) and P-stepping (11.6 %; 95 % CI 5.3-17.8 %) treadmill training in participants who take a shorter step with their paretic leg, however effects were only sustained after Conventional training. Step length asymmetry did not improve for P-long participants with any training type.

SIGNIFICANCE

The effectiveness of unilateral step training may be related to the direction of step length asymmetry. Further investigation is required before considering using unilateral step training as a rehabilitation tool for gait asymmetry after stroke.

WITHDRAWN: Immediate Adaptations to Poststroke Walking Performance Using a Wearable Robotic Exoskeleton

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Safety and Feasibility of Transcranial Magnetic Stimulation as an Exploratory Assessment of Corticospinal Connectivity in Infants After Perinatal Brain Injury: An Observational Study

BACKGROUND

Perinatal brain injuries often impact the corticospinal system, leading to motor impairment and cerebral palsy. Although transcranial magnetic stimulation (TMS) has been widely used to study corticospinal connectivity in adults and older children, similar studies of young infants are limited.

OBJECTIVES

The objective was to establish the safety and feasibility of advanced TMS assessments of the corticospinal connectivity of young infants with perinatal brain injury.

DESIGN

This was a pilot, cross-sectional study of 3- to 12-month-old (corrected age) infants with perinatal stroke or intracranial hemorrhage.

METHODS

Six participants (2 term, 4 preterm) were assessed with stereotactic neuronavigation-guided TMS. Single-pulse TMS was applied to each hemisphere and responses were recorded simultaneously from both upper limbs. During data collection, vital signs and stress responses were measured to assess safety. Developmental motor outcomes were evaluated using the General Movements Assessment and Bayley Scales of Infant and Toddler Development (3rd edition). A clinical diagnosis of cerebral palsy was recorded, if available.

RESULTS

No adverse events occurred during TMS testing. All sessions were well tolerated. Contralateral motor evoked responses were detected in 4 of 6 participants. Both contralateral and ipsilateral responses were observed in 2 of 6 participants.

LIMITATIONS

TMS responses were not obtained in all participants. This could be related to the location of brain injury or developmental stage of the corticospinal system controlling the wrist flexor muscle group from which responses were recorded.

CONCLUSIONS

This study provides a summary of the framework for performing novel TMS assessments in infants with perinatal brain injury. Implementing this approach to measure corticospinal connectivity in hypothesis-driven studies in young infants appears to be justified. Such studies could inform the characterization of corticospinal development and the neural mechanisms driving recovery following early interventions.

The effect of a novel gait retraining device on lower limb kinematics and muscle activation in healthy adults

The Re-Link Trainer (RLT) is a modified walking frame with a linkage system designed to apply a non-individualized kinematic constraint to normalize gait trajectory of the left limb. The premise behind the RLT is that a user's lower limb is constrained into a physiologically normal gait pattern, ideally generating symmetry across gait cycle parameters and kinematics. This pilot study investigated adaptations in the natural gait pattern of healthy adults when using the RLT compared to normal overground walking. Bilateral lower limb kinematic and electromyography data were collected while participants walked overground at a self-selected speed, followed by walking in the RLT. A series of 2-way analyses of variance examined between-limb and between-condition differences. Peak hip extension and knee flexion were reduced bilaterally when walking in the RLT. Left peak hip extension occurred earlier in the gait cycle when using the RLT, but later for the right limb. Peak hip flexion was significantly increased and occurred earlier for the constrained limb, while peak plantarflexion was significantly reduced. Peak knee flexion and plantarflexion in the right limb occurred later when using the RLT. Significant bilateral reductions in peak electromyography amplitude were evident when walking in the RLT, along with a significant shift in when peak muscle activity was occurring. These findings suggest that the RLT does impose a significant constraint, but generates asymmetries in lower limb kinematics and muscle activity patterns. The large interindividual variation suggests users may utilize differing motor strategies to adapt their gait pattern to the imposed constraint.

The influence of the Re-Link Trainer on gait symmetry in healthy adults

Walking function post-stroke is characterized by asymmetries in gait cycle parameters and joint kinematics. The Re-Link Trainer is designed to provide kinematic constraint to the paretic lower limb, to guide a physiologically normal and symmetrical gait pattern. The purpose of this pilot study was to assess the immediate influence of the Re-Link Trainer on measures of gait symmetry in healthy adults. Participants demonstrated a significantly lower cadence and a 62% reduction in walking speed in the Re-Link Trainer compared to normal walking. The step length ratio had a significant increase from 1.0 during normal walking to 2.5 when walking in the Re-Link Trainer. The results from this pilot study suggest in its current iteration the Re-Link Trainer imposes an asymmetrical constraint on lower limb kinematics.

Design, Analysis, and Optimization of an Acute Stroke Gait Rehabilitation Device

Stroke is one of the leading causes of adult physical disability, and rehabilitation and hospitalization costs for stroke are among the highest for all injuries. Current rehabilitation techniques are labor intensive and time consuming for therapists and difficult to perform effectively. Research suggests that starting rehabilitation during the acute or subacute stage of recovery results in better outcomes than therapy delivered in the chronic stage. To improve the gait rehabilitation process, robot-assisted gait rehabilitation has gained much interest over the past years. However, many robot-assisted rehabilitation devices have limitations; one of which is being bulky and complex to handle. Large and expensive devices that require special training to operate are less attractive to clinics and therapists, and ultimately less likely to be available to patients especially at the early stage of stroke. To address these limitations, this research proposes a new gait rehabilitation device called the linkage design gait trainer (LGT). The device is based on a walking frame design with a simple four-bar linkage “end-effector” mechanism to generate normal gait trajectories during general walking and exercise. The design of the four-bar linkage mechanism was optimized for a particular gait pattern. A prototype of the device was developed and tested. The kinematics of the device itself and gait kinematics with and without assistance from the device were recorded and analyzed using an optical motion capture system. The results show the linkage mechanism is able to guide the leg of the user during over ground walking. There were some differences in the hip (20.5 deg RMS) and knee (14.8 deg RMS) trajectory between the person walking with and without the device assistance. The study demonstrated the concept and feasibility of this novel gait training device.

Abstract 152: The Contrastim Stroke Study: Improving Hand and Arm Function After Stroke With Combined Non-Invasive Brain Stimulation and Task-Oriented Therapy - A Pilot Study

Objective: To determine whether neuro-navigated 1hz rTMS targeted to the non-lesioned hemisphere (NLH) combined with task-oriented occupational therapy (OT) can improve motor function of arm and hand in patients with subacute stroke.

Methods: 30 patients (3-9 months post-stroke) were randomly assigned to sham (n=10) or active 1hz rTMS (n=20) targeted to the wrist extensor representation in the NLH. Patients completed 3 visits per week for 6 weeks that included: 20min pre-functional OT, neuro-navigated 1hz rTMS or sham, and 60 min upper-limb task-oriented OT. Patients returned for 1 week, 1 month, and 6 month follow-up visits. Groups were well matched at baseline but there was a trend toward more severe impairment in the active treatment group on the Upper Extremity Fugl Meyer (UEFM) (23.8±10.2, active; 31.5±15.3, sham: p=0.11).

Results: Patients receiving active rTMS prior to OT made significantly greater gains on the UEFM by 6 months post-intervention than patients receiving sham stimulation (change in UEFM 14.4 ± 10.0 vs. 4.1 ± 5.5; p=0.013). On ANOVA differences were significant for group, time and group x time (F=5.73, df=2, p=0.006). Individuals receiving active rTMS were significantly more likely to exceed the published minimal clinical important difference (MCID) on the UEFM at 6 months post (88% vs. 38%, p = 0.002). Similar trends at 1 week and 1 month post were not statistically significant. Ceiling effects were unlikely.

Conclusion: These findings suggest neuro-navigated 1hz rTMS paired with task-oriented OT is more likely to promote clinically important improvements than OT alone. Of note is the finding that significant improvements in impairment were seen 6 months following therapy, suggesting non-invasive brain stimulation as an adjuvant to therapy promotes lasting motor improvement.

Transcranial direct current stimulation and aphasia: the case of mr. C

PURPOSE

To illustrate the ethical challenges that arose from investigating a novel treatment procedure, transcranial direct current stimulation (tDCS), in a research participant with aphasia.

METHOD

We review the current evidence supporting the use of tDCS in aphasia research, highlighting methodological gaps in our knowledge of tDCS. Then, we examine the case of Mr. C, a person with chronic aphasia who participated in a research protocol investigating the impact of tDCS on aphasia treatment. We describe the procedures that he underwent and the resulting behavioral and neurophysiological outcomes. Finally, we share the steps that were taken to balance beneficence and nonmaleficence and to ensure Mr. C's autonomy.

RESULTS

The objective data show that while Mr. C may not have benefitted from participating in the research, neither did he experience any harm.

CONCLUSION

Researchers must consider not only the scientific integrity of their studies, but also potential ethical issues and consequences to the research participants.

Contribution of intracortical inhibition in voluntary muscle relaxation

Terminating a voluntary muscle contraction is an important aspect of motor control, and yet, its neurophysiology is unclear. The objective of this study was to determine the role of short-interval intracortical inhibition (SICI) by comparing SICIs during relaxation from a power grip versus during a sustained power grip at the matching muscle activity level. Right-handed healthy young adults gripped and relaxed from power grip following auditory cues. The relaxation period was determined as the time for the flexor digitorum superficialis (FDS) muscle to reach its pre-contraction baseline level after the cue to relax. SICI during relaxation was obtained at different times into the relaxation period in two separate studies (70, 80, 90 % into relaxation in Study 1; 25, 50, 75 % into relaxation in Study 2). In addition, SICI during sustained contraction was assessed while subjects maintained a power grip at the matching FDS EMG levels (obtained during relaxation, for both Studies). Results showed that the mean SICI was greater during relaxation than during sustained contraction at the matching muscle activity level in both Studies (p < 0.05), indicating increased activation of intracortical inhibitory circuits for muscle relaxation. SICI gradually increased from 25 to 50 and 75 % into relaxation (Study 2, p < 0.05), but did not change from 70 to 80 and 90 % into relaxation (Study 1). MEP decreased with progression of relaxation (p < 0.05) in both Studies, reflecting gradual decreases in corticomotor excitability. This work supports the hypothesis that relaxation from a voluntary muscle contraction involves inhibitory activity in the primary motor cortex.

Relationships between functional and structural corticospinal tract integrity and walking post stroke

OBJECTIVE

Studies on upper limb recovery following stroke have highlighted the importance of the structural and functional integrity of the corticospinal tract (CST) in determining clinical outcomes. However, such relationships have not been fully explored for the lower limb. We aimed to test whether variation in walking impairment was associated with variation in the structural or functional integrity of the CST.

METHODS

Transcranial magnetic stimulation was used to stimulate each motor cortex while EMG recordings were taken from the vastus lateralis (VL) bilaterally; these EMG measures were used to calculate both ipsilateral and contralateral recruitment curves for each lower limb. The slope of these recruitment curves was used to examine the strength of functional connectivity from the motor cortex in each hemisphere to the lower limbs in chronic stroke patients and to calculate a ratio between ipsilateral and contralateral outputs referred to as the functional connectivity ratio (FCR). The structural integrity of the CST was assessed using diffusion tensor MRI to measure the asymmetry in fractional anisotropy (FA) of the internal capsule. Lower limb impairment and walking speed were also measured.

RESULTS

The FCR for the paretic leg correlated with walking impairment, such that greater relative ipsilateral connectivity was associated with slower walking speeds. Asymmetrical FA values, reflecting reduced structural integrity of the lesioned CST, were associated with greater walking impairment. FCR and FA asymmetry were strongly positively correlated with each other.

CONCLUSIONS

Patients with relatively greater ipsilateral connectivity between the contralesional motor cortex and the paretic lower limb were more behaviorally impaired and had more structural damage to their ipsilesional hemisphere CST.

SIGNIFICANCE

Measures of structural and functional damage may be useful in the selection of therapeutic strategies, allowing for more tailored and potentially more beneficial treatments.