The effects of body position and actual execution on motor imagery of locomotor tasks in people with a lower-limb amputation

Towards efficient motor imagery interventions after lower-limb amputation

BACKGROUND

The therapeutic benefits of motor imagery (MI) are now well-established in different populations of persons suffering from central nervous system impairments. However, research on similar efficacy of MI interventions after amputation remains scarce, and experimental studies were primarily designed to explore the effects of MI after upper-limb amputations.

OBJECTIVES

The present comparative study therefore aimed to assess the effects of MI on locomotion recovery following unilateral lower-limb amputation.

METHODS

Nineteen participants were assigned either to a MI group (n = 9) or a control group (n = 10). In addition to the course of physical therapy, they respectively performed 10 min per day of locomotor MI training or neutral cognitive exercises, five days per week. Participants' locomotion functions were assessed through two functional tasks: 10 m walking and the Timed Up and Go Test. Force of the amputated limb and functional level score reflecting the required assistance for walking were also measured. Evaluations were scheduled at the arrival at the rehabilitation center (right after amputation), after prosthesis fitting (three weeks later), and at the end of the rehabilitation program. A retention test was also programed after 6 weeks.

RESULTS

While there was no additional effect of MI on pain management, data revealed an early positive impact of MI for the 10 m walking task during the pre-prosthetic phase, and greater performance during the Timed Up and Go Test during the prosthetic phase. Also, a lower proportion of participants still needed a walking aid after MI training. Finally, the force of the amputated limb was greater at the end of rehabilitation for the MI group.

CONCLUSION

Taken together, these data support the integration of MI within the course of physical therapy in persons suffering from lower-limb amputations.

Anodal transcranial direct current stimulation does not enhance the effects of motor imagery training of a sequential finger-tapping task in young adults

When applied over the primary motor cortex (M1), anodal transcranial direct current stimulation (a-tDCS) could enhance the effects of a single motor imagery training (MIt) session on the learning of a sequential finger-tapping task (SFTT). This study aimed to investigate the effect of a-tDCS on the learning of an SFTT during multiple MIt sessions. Two groups of 16 healthy young adults participated in three consecutive MIt sessions over 3 days, followed by a retention test 1 week later. They received active or sham a-tDCS during a MIt session in which they mentally rehearsed an eight-item complex finger sequence with their left hand. Before and after each session, and during the retention test, they physically repeated the sequence as quickly and accurately as possible. Both groups (i) improved their performance during the first two sessions, showing online learning; (ii) stabilised the level they reached during all training sessions, reflecting offline consolidation; and (iii) maintained their performance level one week later, showing retention. However, no significant difference was found between the groups, regardless of the MSL stage. These results emphasise the importance of performing several MIt sessions to maximise performance gains, but they do not support the additional effects of a-tDCS.

Cortical Reorganization after Limb Loss: Bridging the Gap between Basic Science and Clinical Recovery

Despite the increasing incidence and prevalence of amputation across the globe, individuals with acquired limb loss continue to struggle with functional recovery and chronic pain. A more complete understanding of the motor and sensory remodeling of the peripheral and central nervous system that occurs postamputation may help advance clinical interventions to improve the quality of life for individuals with acquired limb loss. The purpose of this article is to first provide background clinical context on individuals with acquired limb loss and then to provide a comprehensive review of the known motor and sensory neural adaptations from both animal models and human clinical trials. Finally, the article bridges the gap between basic science researchers and clinicians that treat individuals with limb loss by explaining how current clinical treatments may restore function and modulate phantom limb pain using the underlying neural adaptations described above. This review should encourage the further development of novel treatments with known neurological targets to improve the recovery of individuals postamputation.Significance Statement In the United States, 1.6 million people live with limb loss; this number is expected to more than double by 2050. Improved surgical procedures enhance recovery, and new prosthetics and neural interfaces can replace missing limbs with those that communicate bidirectionally with the brain. These advances have been fairly successful, but still most patients experience persistent problems like phantom limb pain, and others discontinue prostheses instead of learning to use them daily. These problematic patient outcomes may be due in part to the lack of consensus among basic and clinical researchers regarding the plasticity mechanisms that occur in the brain after amputation injuries. Here we review results from clinical and animal model studies to bridge this clinical-basic science gap.

How Posture and Previous Sensorimotor Experience Influence Muscle Activity during Gait Imagery in Young Healthy Individuals

This study explores how gait imagery (GI) influences lower-limb muscle activity with respect to posture and previous walking experience. We utilized surface electromyography (sEMG) in 36 healthy young individuals aged 24 (±1.1) years to identify muscle activity during a non-gait imagery task (non-GI), as well as GI tasks before (GI-1) and after the execution of walking (GI-2), with assessments performed in both sitting and standing postures. The sEMG was recorded on both lower limbs on the tibialis anterior (TA) and on the gastrocnemius medialis (GM) for all tested tasks. As a result, a significant muscle activity decrease was found in the right TA for GI-1 compared to GI-2 in both sitting (p = 0.008) and standing (p = 0.01) positions. In the left TA, the activity decreased in the sitting posture during non-GI (p = 0.004) and GI-1 (p = 0.009) in comparison to GI-2. No differences were found for GM. The subjective level of imagination difficulty improved for GI-2 in comparison to GI-1 in both postures (p < 0.001). Previous sensorimotor experience with real gait execution and sitting posture potentiate TA activity decrease during GI. These findings contribute to the understanding of neural mechanisms beyond GI.

Interventions for motor rehabilitation in people with transtibial amputation due to peripheral arterial disease or diabetes

BACKGROUND

Amputation is described as the removal of an external part of the body by trauma, medical illness or surgery. Amputations caused by vascular diseases (dysvascular amputations) are increasingly frequent, commonly due to peripheral arterial disease (PAD), associated with an ageing population, and increased incidence of diabetes and atherosclerotic disease. Interventions for motor rehabilitation might work as a precursor to enhance the rehabilitation process and prosthetic use. Effective rehabilitation can improve mobility, allow people to take up activities again with minimum functional loss and may enhance the quality of life (QoL). Strength training is a commonly used technique for motor rehabilitation following transtibial (below-knee) amputation, aiming to increase muscular strength. Other interventions such as motor imaging (MI), virtual environments (VEs) and proprioceptive neuromuscular facilitation (PNF) may improve the rehabilitation process and, if these interventions can be performed at home, the overall expense of the rehabilitation process may decrease. Due to the increased prevalence, economic impact and long-term rehabilitation process in people with dysvascular amputations, a review investigating the effectiveness of motor rehabilitation interventions in people with dysvascular transtibial amputations is warranted.

OBJECTIVES

To evaluate the benefits and harms of interventions for motor rehabilitation in people with transtibial (below-knee) amputations resulting from peripheral arterial disease or diabetes (dysvascular causes).

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date was 9 January 2023.

SELECTION CRITERIA

We included randomised controlled trials (RCT) in people with transtibial amputations resulting from PAD or diabetes (dysvascular causes) comparing interventions for motor rehabilitation such as strength training (including gait training), MI, VEs and PNF against each other.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were 1. prosthesis use, and 2.

ADVERSE EVENTS

Our secondary outcomes were 3. mortality, 4. QoL, 5. mobility assessment and 6. phantom limb pain. We use GRADE to assess certainty of evidence for each outcome.

MAIN RESULTS

We included two RCTs with a combined total of 30 participants. One study evaluated MI combined with physical practice of walking versus physical practice of walking alone. One study compared two different gait training protocols. The two studies recruited people who already used prosthesis; therefore, we could not assess prosthesis use. The studies did not report mortality, QoL or phantom limb pain. There was a lack of blinding of participants and imprecision as a result of the small number of participants, which downgraded the certainty of the evidence. We identified no studies that compared VE or PNF with usual care or with each other. MI combined with physical practice of walking versus physical practice of walking (one RCT, eight participants) showed very low-certainty evidence of no difference in mobility assessment assessed using walking speed, step length, asymmetry of step length, asymmetry of the mean amount of support on the prosthetic side and on the non-amputee side and Timed Up-and-Go test. The study did not assess adverse events. One study compared two different gait training protocols (one RCT, 22 participants). The study used change scores to evaluate if the different gait training strategies led to a difference in improvement between baseline (day three) and post-intervention (day 10). There were no clear differences using velocity, Berg Balance Scale (BBS) or Amputee Mobility Predictor with PROsthesis (AMPPRO) in training approaches in functional outcome (very low-certainty evidence). There was very low-certainty evidence of little or no difference in adverse events comparing the two different gait training protocols.

AUTHORS' CONCLUSIONS

Overall, there is a paucity of research in the field of motor rehabilitation in dysvascular amputation. We identified very low-certainty evidence that gait training protocols showed little or no difference between the groups in mobility assessments and adverse events. MI combined with physical practice of walking versus physical practice of walking alone showed no clear difference in mobility assessment (very low-certainty evidence). The included studies did not report mortality, QoL, and phantom limb pain, and evaluated participants already using prosthesis, precluding the evaluation of prosthesis use. Due to the very low-certainty evidence available based on only two small trials, it remains unclear whether these interventions have an effect on the prosthesis use, adverse events, mobility assessment, mortality, QoL and phantom limb pain. Further well-designed studies that address interventions for motor rehabilitation in dysvascular transtibial amputation may be important to clarify this uncertainty.

Anodal tDCS does not enhance the learning of the sequential finger-tapping task by motor imagery practice in healthy older adults

Background

Motor imagery practice (MIP) and anodal transcranial direct current stimulation (a-tDCS) are innovative methods with independent positive influence on motor sequence learning (MSL) in older adults.

Objective

The present study investigated the effect of MIP combined with a-tDCS over the primary motor cortex (M1) on the learning of a finger tapping sequence of the non-dominant hand in healthy older adults.

Methods

Thirty participants participated in this double-blind sham-controlled study. They performed three MIP sessions, one session per day over three consecutive days and a retention test 1 week after the last training session. During training / MIP, participants had to mentally rehearse an 8-element finger tapping sequence with their left hand, concomitantly to either real (a-tDCS group) or sham stimulation (sham-tDCS group). Before and after MIP, as well as during the retention test, participants had to physically perform the same sequence as fast and accurately as possible.

Results

Our main results showed that both groups (i) improved their performance during the first two training sessions, reflecting acquisition/on-line performance gains, (ii) stabilized their performance from one training day to another, reflecting off-line consolidation; as well as after 7 days without practice, reflecting retention, (iii) for all stages of MSL, there was no significant difference between the sham-tDCS and a-tDCS groups.

Conclusion

This study highlights the usefulness of MIP in motor sequence learning for older adults. However, 1.5 mA a-tDCS did not enhance the beneficial effects of MIP, which adds to the inconsistency of results found in tDCS studies. Future work is needed to further explore the best conditions of use of tDCS to improve motor sequence learning with MIP.

Use of a Single Wearable Sensor to Evaluate the Effects of Gait and Pelvis Asymmetries on the Components of the Timed Up and Go Test, in Persons with Unilateral Lower Limb Amputation

The Timed Up and Go (TUG) test quantifies physical mobility by measuring the total performance time. In this study, we quantified the single TUG subcomponents and, for the first time, explored the effects of gait cycle and pelvis asymmetries on them. Transfemoral (TF) and transtibial (TT) amputees were compared with a control group. A single wearable inertial sensor, applied to the back, captured kinematic data from the body and pelvis during the 10-m walk test and the TUG test. From these data, two categories of symmetry indexes (SI) were computed: One SI captured the differences between the antero-posterior accelerations of the two sides during the gait cycle, while another set of SI quantified the symmetry over the three-dimensional pelvis motions. Moreover, the total time of the TUG test, the time of each subcomponent, and the velocity of the turning subcomponents were measured. Only the TF amputees showed significant reductions in each SI category when compared to the controls. During the TUG test, the TF group showed a longer duration and velocity reduction mainly over the turning subtasks. However, for all the amputees there were significant correlations between the level of asymmetries and the velocity during the turning tasks. Overall, gait cycle and pelvis asymmetries had a specific detrimental effect on the turning performance instead of on linear walking.