The priming effect of mirror visual feedback can be simply provided by inexpensive mirror therapy (MT), which exhibits beneficial effects on sensorimotor recovery in stroke. The present study was a single-blind pretest-posttest study that examined whether the priming effect of mirror visual feedback on bilateral task practice would render better outcomes. Twenty-three patients with chronic stroke were randomized to receive hospital-based task-oriented MT or bilateral arm training (BAT) for 4 weeks at 90 minutes/day, 3 days/week and a home practice for 30-40 minutes/day, 5 days/week. There was the potential trend for MT to improve temperature sense as measured by the revised Nottingham Sensory Assessment (Cohen’s
Stroke is a leading cause of disability worldwide. Stroke survivors may have impairments in sensorimotor function [
Among a wide range of stroke interventions, mirror therapy (MT) and bilateral arm training (BAT) are novel therapies for stroke. These interventions are priming techniques based on the bilateral approach to stroke rehabilitation and are easy for implementation during occupational therapy [
BAT has been provided in different forms, such as symmetric or alternating patterns, in task-oriented or non-task-oriented practice, and BAT has been implemented with electromyography-triggered neuromuscular stimulation, robots, or auditory cueing [
MT and BAT share similar key therapeutic elements, including the use of simultaneous bilateral arm movements, mass, and repetitive practice and providing movement-based priming. Conversely, the difference between BAT and MT lies in the mirror visual feedback in MT, which involves perceptual incongruence between visual and somatosensory areas and may offer a priming effect on motor learning [
In the past, MT was used as a priming technique to improve affected arm function and occupational performance for stroke [
This study evaluated the priming effects of mirror visual feedback by comparing the effects of task-oriented MT and BAT on sensorimotor performance and quality of life among chronic stroke patients who received an equal amount of therapy. We hypothesized that bilateral task practice with visual mirror feedback would lead to greater improvement in the outcome measures than bilateral task practice alone.
Individuals were recruited from 4 participating sites, including 1 medical center and 3 regional hospitals, upon the institutional review board approval. Using hospital records, once the potential participants were identified by the study therapist, the participants were invited and explained the experimental procedures of this study. Further eligibility and baseline assessments were then undertaken by the study assessor. The diagnosis of stroke was performed using standard imaging techniques. The inclusion criteria were that the patient had sustained their first-ever unilateral ischemic or hemorrhagic stroke more than 6 months after the onset; had mild to moderate motor impairment (total Fugl-Meyer Assessment upper extremity score between 18 and 55) [
Flow diagram of participants in the study.
The study used a single-blind randomized pretest and posttest design. Based on a computer-generated random-sequence table, permuted-block randomization to the BAT or MT groups (Figure
The treatment regimens were designed so that both groups received an equal amount of therapy, which included 4 weeks with (1) 1.5 hours/day, 3 days/week of hospital-based MT or the BAT protocol and (2) 30 to 40 minutes/day, 5 days/week of home practice. The hospital-based therapy was conducted during the participants’ regularly scheduled occupational therapy sessions. All other routine interdisciplinary stroke rehabilitation methods were continued as usual throughout the study.
The hospital-based MT protocol included mirror box training for 45 minutes and functional training for 45 minutes. After 10 minutes of warm-up exercises for the affected arm, including stretching and a passive range of motion exercises, a portable mirror box (
Intervention setup for mirror therapy (a) and bilateral arm training (b).
MT was followed by 45 minutes of functional training, such as chopping vegetables and pouring water from a kettle. All movements and activities during the functional training were designed according to the impairments of the participants and their individual rehabilitation goals.
The hospital-based BAT protocol was similar to that of MT, but the mirror box was not provided (Figure
Home practice was customized to each participant’s regular environment to achieve the purpose of rehabilitation. The activities were selected, demonstrated, and repeatedly practiced throughout the functional training session in the hospital to confirm that the patient performed them correctly. To ensure completeness, we informed the participants about the decline in effect without practice and had them complete a form that included their name, procedure, repetition frequency, and duration of the activities and the problems they encountered while performing the activities. The therapist conducted follow-ups by telephone and communication software or at each hospital visit.
The outcome measures used in the study covered the International Classification of Functioning, Disability and Health (ICF) domains of body function, structure, activity, and participation and included the Fugl-Meyer Assessment, the revised Nottingham Sensory Assessment, the Chedoke Arm and Hand Activity Inventory, the Motor Activity Log, and the Stroke Impact Scale 3.0. The amount of therapy (the repetition frequency of 10 minutes of non-task-oriented movements plus 35 minutes of task-oriented activities) administered to the participants and potential adverse effects, including pain and fatigue, were also recorded during the intervention period.
The level of upper extremity motor impairment was evaluated with the 33-item Fugl-Meyer Assessment, which uses a 3-point scale (0 to 2) [
The Chedoke Arm and Hand Activity Inventory measures arm and hand functions on 13 real-life bilateral tasks on a 7-point scale (1 to 7) [
Baseline clinical characteristics were presented as frequencies with percentages, means with standard deviations (SDs), or medians with the interquartile ranges. The differences between the two groups were compared by Fisher’s exact test for categorical data and by the independent
Twenty-three stroke patients (13 men and 10 women) consented to participate in the study. The patients had a mean age of 54.57 years (SD, 10.52 years; range, 41.16 years) with a mean stroke onset of 53 months (SD, 31.58 months) (Figure
Demographics and baseline clinical characteristics.
Characteristics | Mirror therapy ( |
Bilateral arm training ( |
---|---|---|
Age (y) | 50.72 (10.75) | 58.77 (8.91) |
Sex | ||
Male | 7 (58.33%) | 6 (54.55%) |
Female | 5 (41.67%) | 5 (45.45%) |
Side of lesion | ||
Left | 5 (41.67%) | 5 (45.45%) |
Right | 7 (58.33%) | 6 (54.55%) |
Type of stroke | ||
Ischemia | 6 (50.00%) | 6 (54.55%) |
Hemorrhage | 6 (50.00%) | 5 (45.45%) |
Months from stroke onset | 57.92 (29.92) | 47.64 (33.9) |
Fugl-Meyer assessment—upper extremity | 33.42 (7.48) | 33 (9.74) |
National Institutes of Health Stroke Scale | 4.25 (2.53) | 4.91 (3.51) |
Education (y) | 10.38 (5.13) | 10.45 (3.11) |
Note: data are the mean (standard deviation), median (interquartile range), or
No significant difference in the Fugl-Meyer Assessment was found between the two groups (Table
Descriptive and inferential statistics for outcome measures.
Pretest scores | Posttest scores | Estimated between-group difference‡ | |||||
---|---|---|---|---|---|---|---|
Mirror therapy | Bilateral arm training | Mirror therapy | Bilateral arm training | Mean/median differences (95% CI) | |||
Fugl-Meyer Assessment—upper extremity | |||||||
Proximal | 28.33 (5.03) | 26.27 (6.26) | 29.42 (5.18) | 28.09 (5.61) | −0.74 (−2.26-0.78) | 0.83 | −0.40 (−1.22-0.44) |
Distal | 5.08 (3.53) | 6.73 (5.06) | 6.75 (3.39) | 8.18 (5.12) | 0.22 (−1.24-1.68) | 0.39 | 0.12 (−0.70-0.94) |
Total | 33.42 (7.48) | 33 (9.74) | 36.17 (8.01) | 36.27 (9.57) | −0.52 (−2.83-1.79) | 0.67 | −0.19 (−1.00-0.64) |
Revised Nottingham Sensory Assessment† | |||||||
Light touch | 4 (0-8) | 8 (6-8) | 7 (0-8) | 8 (7-8) | 0 (−0.42-1.42) | 0.37 | 0.18 (−0.86-1.22) |
Temperature | 2 (0-4) | 6 (0-8) | 4 (1-7) | 5.5 (0-7) | 0 (0.14-2.74) | 0.05 | 1.00 (−0.09-2.09) |
Pinprick | 8 (2-8) | 8 (7-8) | 8 (3-8) | 8 (8-8) | 0 (−2.31-1.75) | 0.50 | 0.00 (−1.03-1.03) |
Pressure | 8 (2-8) | 8 (8-8) | 8 (0-8) | 8 (8-8) | 0 (−0.62-0.40) | 0.50 | 0.00 (−1.03-1.03) |
Localization | 0 (0-5) | 5 (0-7) | 3 (0-4) | 8 (4-8) | −1.5 (−3.14-0.14) | 0.95 | −1.05 (−2.15-0.05) |
Bilateral simultaneous touch | 7 (0-8) | 8 (6-8) | 4 (0-8) | 8 (8-8) | 0 (−1.72-0.62) | 0.68 | −0.26 (−1.30-0.78) |
Tactile total scale | 27 (6-41) | 44 (27-46) | 34 (11-41) | 45.5 (35-47) | 0 (−4.28-3.28) | 0.70 | −0.29 (−1.33-0.75) |
Chedoke Arm and Hand Activity Inventory | 41.42 (7.05) | 42.82 (11.63) | 46.58 (9.39) | 50.27 (14.93) | −2.28 (−6.59-2.03) | 0.85 | −0.44 (−1.25-0.40) |
Motor Activity Log | |||||||
Amount of use | 0.58 (0.27) | 0.84 (0.56) | 1.37 (0.7) | 1.33 (0.8) | 0.30 (−0.09-0.69) | 0.08 | 0.62 (−0.24-1.44) |
Quality of movement | 0.44 (0.24) | 0.67 (0.6) | 1.18 (0.66) | 1.17 (0.73) | 0.24 (−0.14-0.62) | 0.12 | 0.50 (−0.35-1.31) |
Stroke Impact Scale overall | 65.46 (6.87) | 64.46 (20.53) | 71.38 (9.44) | 64.56 (17.4) | 5.82 (0.40-11.24) | 0.02 | 0.89 (0.003-1.71) |
Note: data are the mean (standard deviation) or median (interquartile range). CI = confidence interval. †Only those participants who scored less than 48 points at pretest, indicating sensation impairments, were included in the data analysis. ‡Mean/median difference was subtracted mean/median change score of bilateral arm training group from the one of mirror therapy group. §
No statistically significant difference in the Chedoke Arm and Hand Activity Inventory was found between the two groups (Table
To the best of our knowledge, this study is the first to evaluate the priming effects of mirror visual feedback by comparing the effects of task-oriented MT and BAT on sensorimotor performance and quality of life among chronic stroke patients who received an equal amount of therapy. This study highlights the mirror visual feedback, which may be a pivotal element of bilateral task practice in MT, and provides different recovery characteristics. The findings partially support our hypothesis, with greater improvements in temperature sense and quality of life after MT.
A previous study showed that MT has a large effect and demonstrated group differences in changes in temperature sense [
In addition, although no statistically significant differences were found from before to after treatment in the outcome measures of motor impairment and arm/hand functions on bilateral tasks, the MT group showed significant improvements in quality of life and exhibited a trend for a greater extent of improved amount of use and quality of movement in daily life than the dose-matched BAT group. These results could be explained by an increased activation of the mirror neuron system and the priming effect of mirror visual feedback. The perceptual and motor areas may be connected by the mirror neuron system [
Furthermore, according to the priming paradigms, mirror visual feedback from MT provides priming effects not only by movement-based priming but also by further motor imagery and action observation [
The descriptive data showed that the improvement of the motor impairment and arm/hand functions on bilateral tasks was not significantly different between groups. Several possible reasons may explain these observations. First, a previous study showed bilateral reaching for targets that shifted from within to beyond the length of the arm increasing the recruitment of arm movements [
Second, the bilateral MT used in the study may have led to a limited deployment of attention to the mirror and practice of simultaneous bilateral movements for the participants with somatosensory impairment or poor attention. The possible efficacy might have also been decreased during bilateral MT.
This preliminary study has several limitations that warrant consideration. First, this study was based on a small sample size. Further research based on a larger sample is needed to validate and extend the findings. For example, given a power of 0.80 and a one-sided type I error of 0.05, the minimum sample size for future trials to validate the advantages of MT in improving somatosensory function (e.g., temperature) will be at least 14 subjects in each intervention group. Second, we did not consider the effect of individualized target distance on the arm and trunk movement during reaching. This aspect is probably a factor contributing to the differences observed between these two groups and needs to be tested or well controlled in future studies.
Third, the bilateral MT used in the study may have also led to a limitation of deploying attention to the mirror and the practice of bilateral movements. The nature of mirror visual feedback experienced by the participants in the MT group may have differed on an individual basis and warrants scrutiny. The unilateral approach to MT or MT augmented by auditory feedback might be appropriate modifications in future research.
Finally, the demographic characteristics of the study participants should be considered when interpreting the findings of the study. Patients with hemorrhagic stroke may display better functional improvements over time [
Age may also be a moderator factor of the priming effect of mirror visual feedback in stroke that warrants evaluation. One study suggested that the activation of the mirror neuron system was independent of age [
Social or personal factors, such as family support or general health status, might influence treatment outcomes, which may further affect the performance of or participation in meaningful occupations [
According to the results of this study, when providing occupational therapy interventions to patients with profiles similar to those outlined in our study, the priming effect induced by mirror visual feedback could be used to enhance sensorimotor performance after stroke. Furthermore, providing mirror visual feedback may be a better option if improved temperature sense or quality of life is the goal of treatment. Use of mirror visual feedback on bilateral task practice may increase the amount of use and quality of movement of the affected upper extremity.
This comparative study sheds some light on the priming effects of mirror visual feedback on improvements after stroke. Having mirror visual feedback on bilateral task practice had a better effect on the recovery of the temperature sense and quality of life. To effectively achieve treatment goals for bilateral task practice in sensorimotor rehabilitation, providing mirror visual feedback may be a better option if improvement of stroke-related quality of life is the goal of treatment. Our study also presents mirror visual feedback as a better option for the improvement of sensory function. These findings may be helpful in planning individually tailored rehabilitation therapies involving the bilateral practice approach.
The demographic and clinical data collected to support the findings of this study were approved by the Human Research Committee of the China Medical University Hospital for protecting patient privacy. The data used to support the findings of this study are available from the corresponding author upon request (
The authors declare that there is no conflict of interest regarding the publication of this paper.
This study was partly supported by the National Health Research Institutes (NHRI-EX106-10403PI, NHRI-EX107-10403PI, and NHRI-EX106-10604PI) and the Ministry of Science and Technology (103-2314-B-002-008-MY3, 103-2314-B-182-004-MY3, 104-2314-B-002-019-MY3, 105-2314-B-182-037-MY3, 105-2314-B-182-018, 107-2314-B-002-052, and 108-2314-B-002-165-MY3) of Taiwan.