Backward locomotor treadmill training combined with transcutaneous spinal direct current stimulation in stroke: a randomized pilot feasibility and safety study

Exploring the Impact of Backward and Forward Locomotor Treadmill Training in Chronic Stroke Survivors with Severe Post-Stroke Walking Impairment: A Single-Center Pilot Randomized Controlled Trial

BACKGROUND

Defined as a self-selected speed of <0.4 m/s, chronic stroke survivors falling in this category are classified as "severe", usually homebound and sedentary, and they experience worse outcomes. Limited rehabilitation strategies are available to improve walking speed and related outcomes in this subgroup, and questions regarding effective rehabilitation options remain. The objective of this study was to determine the effects of backward (BLTT) and forward (FLTT) locomotor treadmill training on overground walking speed, spatiotemporal symmetry, and dynamic postural stability.

METHODS

In this single-center, assessor-blinded, randomized controlled pilot trial, 14 stroke survivors with severe waking impairment underwent 12 sessions of BLTT (n = 7) or FLTT (n = 7). The primary outcome was the proportion of participants reaching clinically meaningful important difference (MCID) on the 10-meter walk test following training completion. Secondary outcomes were between-group differences in walking speed, spatiotemporal symmetry, and completion time on the 3-meter timed up and go (3M TUG) at 24 h, 30 days, and 90 days POST.

RESULTS

Two subjects in the BLTT group (28.6%) and one (14.3%) in FLTT achieved MCID following training; however, most subjects did not, with significant variability in response. At 24 h POST, the median (IQR) percent change in walking speed was 28.9 (9.01-36.7) and 17.4 (12.6-39.7) with BLTT and FLTT, respectively; however, no between-group differences were seen (p = 0.80) at this time point or at 30 (p > 0.99) and 90 (p > 0.99) days follow up. Likewise, there were no significant between-group differences in spatiotemporal symmetry and the 3M TUG across time points.

CONCLUSIONS

While preliminary, this study found that 12 training sessions did not lead to group-level achievement of MCID for walking speed in our cohort and found no significant between-group differences in walking capacity or dynamic postural stability. Future well-powered dosing trials and mechanistically driven studies are needed to optimize and identify predictors of training response.

Effects of Transcranial and Trans-Spinal Direct Current Stimulation Combined with Robot-Assisted Gait Training on Gait and Fatigue in Patients with Multiple Sclerosis: A Double-Blind, Randomized, Sham-Controlled Study

Background/Objectives: Multiple Sclerosis (MS) is a chronic neurological condition that impairs motor and sensory functions, particularly gait. Non-invasive neuromodulation techniques aim to enhance functional recovery and motor-cognitive outcomes, though their effectiveness remains debated. This study compared the effects of transcranial direct current stimulation (tDCS) and trans-spinal direct current stimulation (tsDCS), combined with robotic-assisted gait training (RAGT), on motor function and fatigue in people with MS (pwMS). Methods: This double-blind, randomized, sham-controlled clinical trial included 35 pwMS, who participated in 12 sessions of 20 min anodal tDCS (n = 11), cathodal tsDCS (n = 12), or sham treatment (n = 12), in addition to RAGT. Primary outcomes were assessed using the Timed 25-foot Walk (T25-FW), Timed Up and Go (TUG), walking speed, and Multiple Sclerosis Walking Scale-12 (MSWS-12). Fatigue was assessed with the Fatigue Severity Scale (FSS) and the Fatigue Impact Scale (FIS). ClinicalTrials number: NCT06121635. Results: Significant improvements in gait speed, T25-FW, MSWS-12, TUG scores, and fatigue (FSS) favored tDCS and tsDCS over sham stimulation. While no differences were found between tDCS and tsDCS, the tsDCS group showed a significant improvement in the FIS physical subscale compared to sham, unlike the tDCS group. Conclusions: tDCS and tsDCS, combined with RAGT, improve walking and reduce fatigue in pwMS, highlighting their potential in motor rehabilitation.

Interventions to improve outdoor mobility among people living with disabilities: A systematic review

Background

Around 15% of the global population live with some form of disabilities and experience worse health outcomes, less participation in the community and are part of fewer activities outside the home. Outdoor mobility interventions aim to improve the ability to move, travel and orient outside the home and could influence the number of activities outside the home, participation and quality of life. However, outdoor mobility interventions may also lead to harm like falls or injuries or have unforeseen effects which could lead to mortality or hospitalization.

Objectives

To assess the efficacy of interventions aiming to improve outdoor mobility for adults living with disabilities and to explore if the efficacy varies between different conditions and different intervention components.

Search Methods

Standard, extensive Campbell search methods were used, including a total of 12 databases searched during January 2023, including trial registries.

Selection Criteria

Only randomized controlled trials were included, focusing on people living with disabilities, comparing interventions to improve outdoor mobility to control interventions as well as comparing different types of interventions to improve outdoor mobility.

Data Collection and Analysis

Standard methodological procedures expected by Campbell were used. The following important outcomes were 1. Activity outside the home; 2. Engagement in everyday life activities; 3. Participation; 4. Health-related Quality of Life; 5. Major harms; 6. Minor harms. The impact of the interventions was evaluated in the shorter (≤6 months) and longer term (≥7 months) after starting the intervention. Results are presented using risk ratios (RR), risk difference (RD), and standardized mean differences (SMD), with the associated confidence intervals (CI). The risk of bias 2-tool and the GRADE-framework were used to assess the certainty of the evidence.

Main Results

The screening comprised of 12.894 studies and included 22 studies involving 2.675 people living with disabilities and identified 12 ongoing studies. All reported outcomes except one (reported in one study, some concerns of bias) had overall high risk of bias. Thirteen studies were conducted in participants with disabilities due to stroke, five studies with older adults living with disabilities, two studies with wheelchair users, one study in participants with disabilities after a hip fracture, and one study in participants with cognitive impairments. Skill training interventions versus control interventions (16 studies) The evidence is very uncertain about the benefits and harms of skill training interventions versus control interventions not aimed to improve outdoor mobility among all people living with disabilities both in the shorter term (≤6 months) and longer term (≥7 months) for Activity outside the home; Participation; Health-related Quality of Life; Major harms; and Minor harms, based on very low certainty evidence. Skill training interventions may improve engagement in everyday life activities among people with disabilities in the shorter term (RR: 1.46; 95% CI: 1.16 to 1.84; I 2 = 7%; RD: 0.15; 95% CI: -0.02 to 0.32; I 2 = 71%; 692 participants; three studies; low certainty evidence), but the evidence is very uncertain in the longer term, based on very low certainty evidence. Subgroup analysis of skill training interventions among people living with disabilities due to cognitive impairments suggests that such interventions may improve activity outside the home in the shorter term (SMD: 0.44; 95% CI: 0.07 to 0.81; I 2 = NA; 118 participants; one study; low certainty evidence). Subgroup analysis of skill training interventions among people living with cognitive impairments suggests that such interventions may improve health-related quality of life in the shorter term (SMD: 0.49; 95% CI: 0.12 to 0.88; I 2 = NA; 118 participants; one study; low certainty evidence). Physical training interventions versus control interventions (five studies) The evidence is very uncertain about the benefits and harms of physical training interventions versus control interventions not aimed to improve outdoor mobility in the shorter term (≤6 months) and longer term (≥7 months) for: Engagement in everyday life activities; Participation; Health-related Quality of Life; Major harms; and Minor harms, based on very low certainty evidence. Physical training interventions may improve activity outside the home in the shorter (SMD: 0.35; 95% CI: 0.08 to 0.61; I 2 = NA; 228 participants; one study; low certainty evidence) and longer term (≥7 months) (SMD: 0.27; 95% CI: 0.00 to 0.54; I 2 = NA; 216 participants; one study; low certainty evidence). Comparison of different outdoor mobility interventions (one study) The evidence is very uncertain about the benefits and harms of outdoor mobility interventions of different lengths in the shorter term (≤6 months) and longer term (≥7 months) for Activity outside the home; Engagement in everyday life activities; Participation; Health-related Quality of Life; Major harms; and Minor harms, based on very low certainty evidence. No studies explored the efficacy of other types of interventions.

Authors’ Conclusions

Twenty-two studies of interventions to improve outdoor mobility for people living with disabilities were identified, but the evidence still remains uncertain about most benefits and harms of these interventions, both in the short- and long term. This is primarily related to risk of bias, small underpowered studies and limited reporting of important outcomes for people living with disabilities. For people with disabilities, skill training interventions may improve engagement in everyday life in the short term, and improve activity outside the home and health-related quality of life for people with cognitive impairments in the short term. Still, this is based on low certainty evidence from few studies and should be interpreted with caution. One study with low certainty evidence suggests that physical training interventions may improve activity outside the home in the short term. In addition, the effect sizes across all outcomes were considered small or trivial, and could be of limited relevance to people living with disabilities. The evidence is currently uncertain if there are interventions that can improve outdoor mobility for people with disabilities, and can improve other important outcomes, while avoiding harms. To guide decisions about the use of interventions to improve outdoor mobility, future studies should use more rigorous design and report important outcomes for people with disabilities to reduce the current uncertainty.

Trans-Spinal Direct Current Stimulation in Neurological Disorders: A systematic review

BACKGROUND AND PURPOSE

Trans-spinal direct current stimulation (tsDCS) is a noninvasive stimulation technique that applies direct current stimulation over spinal levels. However, the effectiveness and feasibility of this stimulation are still unclear. This systematic review summarizes the effectiveness of tsDCS in clinical and neurophysiological outcomes in neurological patients, as well as its feasibility and safety.

METHODS

The search was conducted using the following databases: PEDro, Scopus, Web of Science, CINAHL, SPORTDiscus, and PubMed. The inclusion criteria were: Participants : people with central nervous system diseases; Interventions : tsDCS alone or in combination with locomotion training; Comparators : sham tsDCS, transcranial direct current stimulation, or locomotion training; Outcomes : clinical and neurophysiological measures; and Studies : randomized clinical trials.

RESULTS

Eight studies with a total of 143 subjects were included. Anodal tsDCS led to a reduction in hypertonia, neuropathic pain intensity, and balance deficits in people with hereditary spastic paraplegia, multiple sclerosis, and primary orthostatic tremor, respectively. In contrast, cathodal tsDCS only had positive effects on balance and tremor in people with primary orthostatic tremor. No severe adverse effects were reported during and after anodal or cathodal tsDCS.

DISCUSSION AND CONCLUSIONS

Although certain studies have found an effect of anodal tsDCS on specific clinical outcomes in people with central nervous system diseases, its effectiveness cannot be established since these findings have not been replicated and the results were heterogeneous. This stimulation was feasible and safe to apply. Further studies are needed to replicate the obtained results of tsDCS when applied in populations with neurological diseases.

Dynamic electrical stimulation enhances the recruitment of spinal interneurons by corticospinal input

Highly varying patterns of electrostimulation (Dynamic Stimulation, DS) delivered to the dorsal cord through an epidural array with 18 independent electrodes transiently facilitate corticospinal motor responses, even after spinal injury. To partly unravel how corticospinal input are affected by DS, we introduced a corticospinal platform that allows selective cortical stimulation during the multisite acquisition of cord dorsum potentials (CDPs) and the simultaneous supply of DS. Firstly, the epidural interface was validated by the acquisition of the classical multisite distribution of CDPs and their input-output profile elicited by pulses delivered to peripheral nerves. Apart from increased EMGs, DS selectively increased excitability of the spinal interneurons that first process corticospinal input, without changing the magnitude of commands descending from the motor cortex, suggesting a novel correlation between muscle recruitment and components of cortically-evoked CDPs. Finally, DS increases excitability of post-synaptic spinal interneurons at the stimulation site and their responsiveness to any residual supraspinal control, thus supporting the use of electrical neuromodulation whenever the motor output is jeopardized by a weak volitional input, due to a partial disconnection from supraspinal structures and/or neuronal brain dysfunctions.

Spinal facilitation of descending motor input

Highly varying patterns of electrostimulation (Dynamic Stimulation, DS) delivered to the dorsal cord through an epidural array with 18 independent electrodes transiently facilitate corticospinal motor responses, even after spinal injury. To partly unravel how corticospinal input are affected by DS, we introduced a corticospinal platform that allows selective cortical stimulation during the multisite acquisition of cord dorsum potentials (CDPs) and the simultaneous supply of DS. Firstly, the epidural interface was validated by the acquisition of the classical multisite distribution of CDPs on the dorsal cord and their input-output profile elicited by pulses delivered to peripheral nerves. Apart from increased EMGs, DS selectively increased excitability of the spinal interneurons that first process corticospinal input, without changing the magnitude of commands descending from the motor cortex, suggesting a novel correlation between muscle recruitment and components of cortically-evoked CDPs. Finally, DS increases excitability of post-synaptic spinal interneurons at the stimulation site and their responsiveness to any residual supraspinal control, thus supporting the use of electrical neuromodulation whenever the motor output is jeopardized by a weak volitional input, due to a partial disconnection from supraspinal structures and/or neuronal brain dysfunctions.

What Else Can Be Done by the Spinal Cord? A Review on the Effectiveness of Transpinal Direct Current Stimulation (tsDCS) in Stroke Recovery

Since the spinal cord has traditionally been considered a bundle of long fibers connecting the brain to all parts of the body, the study of its role has long been limited to peripheral sensory and motor control. However, in recent years, new studies have challenged this view pointing to the spinal cord's involvement not only in the acquisition and maintenance of new motor skills but also in the modulation of motor and cognitive functions dependent on cortical motor regions. Indeed, several reports to date, which have combined neurophysiological techniques with transpinal direct current stimulation (tsDCS), have shown that tsDCS is effective in promoting local and cortical neuroplasticity changes in animals and humans through the activation of ascending corticospinal pathways that modulate the sensorimotor cortical networks. The aim of this paper is first to report the most prominent tsDCS studies on neuroplasticity and its influence at the cortical level. Then, a comprehensive review of tsDCS literature on motor improvement in animals and healthy subjects and on motor and cognitive recovery in post-stroke populations is presented. We believe that these findings might have an important impact in the future making tsDCS a potential suitable adjunctive approach for post-stroke recovery.

Modeling Electric Fields in Transcutaneous Spinal Direct Current Stimulation: A Clinical Perspective

Clinical findings suggest that transcutaneous spinal direct current stimulation (tsDCS) can modulate ascending sensitive, descending corticospinal, and segmental pathways in the spinal cord (SC). However, several aspects of the stimulation have not been completely understood, and realistic computational models based on MRI are the gold standard to predict the interaction between tsDCS-induced electric fields and anatomy. Here, we review the electric fields distribution in the SC during tsDCS as predicted by MRI-based realistic models, compare such knowledge with clinical findings, and define the role of computational knowledge in optimizing tsDCS protocols. tsDCS-induced electric fields are predicted to be safe and induce both transient and neuroplastic changes. This could support the possibility to explore new clinical applications, such as spinal cord injury. For the most applied protocol (2-3 mA for 20-30 min, active electrode over T10-T12 and the reference on the right shoulder), similar electric field intensities are generated in both ventral and dorsal horns of the SC at the same height. This was confirmed by human studies, in which both motor and sensitive effects were found. Lastly, electric fields are strongly dependent on anatomy and electrodes' placement. Regardless of the montage, inter-individual hotspots of higher values of electric fields were predicted, which could change when the subjects move from a position to another (e.g., from the supine to the lateral position). These characteristics underlines the need for individualized and patient-tailored MRI-based computational models to optimize the stimulation protocol. A detailed modeling approach of the electric field distribution might contribute to optimizing stimulation protocols, tailoring electrodes' configuration, intensities, and duration to the clinical outcome.

Feasibility of transcutaneous spinal direct current stimulation combined with locomotor training after spinal cord injury

Study Design:

Feasibility study, consisting of random-order, cross-over study of a single intervention session, followed by a parallel-arm study of 16 sessions

Objectives:

To investigate the feasibility of a novel combinatorial approach with simultaneous delivery of transcutaneous spinal direct current stimulation (tsDCS) and locomotor training (tsDCS+LT) after spinal cord injury, compared to sham stimulation and locomotor training (sham+LT), and examine preliminary effects on walking function.

Setting:

Clinical research center in the southeastern United States

Methods:

Eight individuals with chronic incomplete spinal cord injury (ISCI) completed the two-part protocol. Feasibility was assessed based on safety (adverse responses), tolerability (pain, spasticity, skin integrity), and protocol achievement (session duration, intensity). Walking function was assessed with the 10-meter and 6-minute walk tests.

Results:

There were no major adverse responses. Minimal reports of skin irritation and musculoskeletal pain were consistent between groups. Average training peak heart rate as percent of maximum (mean(SD); tsDCS+LT: 66(4)%, sham+LT: 69(10)%) and Borg ratings of perceived exertion (tsDCS+LT: 17.5(1.2), sham+LT: 14.4(1.8)) indicate both groups trained at high intensities. Walking speed gains exceeded the minimal clinically important difference (MCID) in three of four who received tsDCS+LT (0.18(0.29) m/s) and one of four in sham+LT (−0.05(0.23) m/s). Gains in walking endurance exceeded the MCID in one of four in each group (tsDCS+LT: 36.4(69.0) m, sham+LT: 4.9(56.9) m).

Conclusions:

Combinatorial tsDCS and locomotor training is safe and feasible for individuals with chronic ISCI, even those with considerable walking impairment. Study outcomes support the need to investigate the efficacy of this approach.

Serial Backward Locomotor Treadmill Training Improves Bidirectional Walking Performance in Chronic Stroke

Background and Research Question

Walking impairment remains a major limitation to functional independence after stroke. Yet, comprehensive and effective strategies to improve walking function after stroke are presently limited. Backward Locomotor Treadmill Training (BLTT) is a promising training approach for improving walking function; however, little is known about its mechanism of effect or the relationship between backward walking training and resulting overground forward walking performance. This study aims to determine the effects of serial BLTT on spatial aspects of backward and forward walking in chronic post-stroke individuals with residual walking impairment.

Methods

Thirty-nine adults (>6 months post-stroke) underwent 6 days of BLTT (3 × /week) over 2 weeks. Outcome measures included PRE-POST changes in backward and forward walking speeds, paretic and non-paretic step lengths, and single-support center of pressure distances. To determine the association between BLTT and overground walking, correlation analyses comparing training-related changes in these variables were performed.

Results

We report an overall improvement in BLTT and overground walking speeds, bilateral step lengths, and single-support center of pressure distances over six training sessions. Further, there were weak positive associations between PRE-POST changes in BLTT speed, BLTT paretic step length, and overground forward walking speed.

Conclusion and Significance

Our findings suggest that individuals with chronic post-stroke walking impairment experience improvements in spatial walking measures during BLTT and overground. Therefore, BLTT may be a potential adjunctive training approach for post-stroke walking rehabilitation.

Backward Locomotor Treadmill Training Differentially Improves Walking Performance across Stroke Walking Impairment Levels

Background: Post-stroke walking impairment is a significant cause of chronic disability worldwide and often leads to loss of life roles for survivors and their caregivers. Walking impairment is traditionally classified into mild (>0.8 m/s), moderate (0.41–0.8 m/s), and severe (≤0.4 m/s), and those categorized as “severe” are more likely to be homebound and at greater risk of falls, fractures, and rehospitalization. In addition, there are minimal effective walking rehabilitation strategies currently available for this subgroup. Backward locomotor treadmill training (BLTT) is a novel and promising training approach that has been demonstrated to be safe and feasible across all levels of impairment; however, its benefits across baseline walking impairment levels (severe (≤0.4 m/s) vs. mild–moderate (>0.4 m/s)) have not been examined. Methods: Thirty-nine adults (>6 months post-stroke) underwent 6 days of BLTT (3×/week) over 2 weeks. Baseline and PRE to POST changes were measured during treadmill training and overground walking. Results: Individuals with baseline severe walking impairment were at a more significant functional disadvantage across all spatiotemporal walking measures at baseline and demonstrated fewer overall gains post-training. However, contrary to our working hypothesis, both groups experienced comparable increases in cadence, bilateral percent single support times, and step lengths. Conclusion: BLTT is well tolerated and beneficial across all walking impairment levels, and baseline walking speed (≤0.4 m/s) should serve as a covariate in the design of future walking rehabilitation trials.