functional electric stimulation (FES) could improve hand function in stroke patients. In this study, we attempt to combine. BAT with FES applying to the post-stroke ...
2011 IEEE International Conference on Rehabilitation Robotics Rehab Week Zurich, ETH Zurich Science City, Switzerland, June 29 - July 1, 2011
Clinical Effects of Combined Bilateral Arm Training with Functional Electrical Stimulation in Patients with Stroke Fang-Chen Wu1, Yin-Tsong Lin1, Te-Son Kuo1,2,3 and Jer-Junn Luh*4, Jin-Shin Lai*5
Abstract—cerebral vascular disease (or stroke) is the main cause of disabilities in adults. Upper-limb dysfunction after stroke usually exists, leading to severe limits of motor capabilities as well as daily activities. Therefore, effective treatment interventions for upper-limb rehabilitation after stroke are needed. Based on the neurophysiological evidence and clinical measures, combined bilateral arm training (BAT) with functional electric stimulation (FES) could improve hand function in stroke patients. In this study, we attempt to combine BAT with FES applying to the post-stroke paretic arm. A linear guide platform with FES feedback control was developed to execute the training of bilateral reaching movements. 35 stroke subjects were recruited and divided into two groups (BAT with FES and BAT alone). 23 participants completed this experiment with 3-week intervention. According to our preliminary results, a favorable trend toward improvement in experimental group (BAT with FES) existed after treatment and at follow-up. Further analysis would be conducted to investigate the kinematic change on motor performance. Moreover, various treatment doses as well as more functional approaches would also be considered for better effects of upper limb rehabilitation after stroke. Keywords: upper limb rehabilitation, bilateral arm training (BAT), functional electrical stimulation (FES) control system
I. INTRODUCTION
S
troke, or cerebral vascular accident (CVA), is the main cause of functional disabilities in adults worldwide. In general, it is common for stroke survivors to have upper limb dysfunction [1]. Approximately two thirds of these patients suffer from motor difficulties, and almost half of them continue to remain deficient in the affected arms and severely limit to activities of daily living (ADL) [2-3]. Medical complications due to immobilization also occur [4-5]. It not only has a negative impact on the self-independent ability of stroke patients, but also increases the costs of medical care as well as labor consumption[5]. Therefore, effective treatment interventions for upper limb rehabilitation after stroke are needed to improve the stroke survivors’ motor control and
1Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University 2Department of Electrical Engineering, National Taiwan University 3Institute of Biomedical Engineering, National Taiwan University 4School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University 5Department of Physical Medicine & Rehabilitation, College of Medicine, National Taiwan University * Corresponding Author
978-1-4244-9862-8/11/$26.00 ©2011 IEEE
functional abilities. Functional electrical stimulation (FES), first described during the 1960s, was applied to patients with spinal cord injury (SCI) [6]. It can generate contractions in weakness or paretic muscles using short electrical current pulses via the surface electrodes, resulting in the inhibition of abnormal reflexes and inducing active movements [7]. Many studies have shown that therapeutic exercise involving functional electric stimulation may benefit stroke patients. Some neurological and physiological researches have demonstrated that this training program could increase cortical density of the damaged hemisphere [8]as well as induce neural plasticity. Besides, the improvement in physical performance such as cardiorespiratory and musculoskeletal function has also been reported by clinical outcome measures [9-11]. Some studies also supported improvement of upper-limb motor function after FES in stroke rehabilitation [12-13]. Consequently, the enhancement of motor recovery and functional capabilities in patients with stroke could be found following FES intervention. Bilateral arm training (BAT) has been thought as a potential therapeutic approach to stroke rehabilitation. Being close to functional activities in real life, it emphasizes bilateral symmetrical movements to coordinate use of both arms during repetitive or rhythmic practice [14]. Recovery of motor function after such training programs has been observed and explained through some neural mechanisms, including neural facilitation of ipsilateral tracts, cortical disinhibition, two-level neural crosstalk, and other central regulation of brain function [15-18]. In recent years, FES has been attempted to apply to bilateral training in stroke rehabilitation. There is increasing evidence that the combination of FES and BAT could not only decrease neurological deficits but improve voluntary movements in stroke patients with upper limb impairment [19-23]. However, these studies mostly focus on the effectiveness of hand function recovery after bilateral training with FES. It is worthy to note that the arm reach motion is the primary movement when people perform upper-limb functional activities. Goal-directed behavior, consisting of both strategy planning and implementation, commonly happens in daily activities[24]. A loss of the ability of arm reaching in stroke patients may lead to motor dysfunction, and influence different levels of executed tasks. Some studies also reported the coordination control training between trunk and arm motion during forward reaching could benefit promotion of trunk stability and increase interaction of external
environment [25-26]. Therefore, a therapeutic exercise of bilateral forward reaching with FES should to be concerned. In this study, FES in combination with BAT was designed for stroke rehabilitation. Outcome measures involving clinical scales and kinematic information, evaluated after 3-week intervention and at follow-up, were to explore whether or not it has a better effect than BAT alone. More details of the experiment and results were described as follows. II. MATERIAL AND METHODS A. SUBJECTS Stroke subjects were recruited from the National Taiwan University Hospital (NTUH). The training program of BAT without FES was performed before as a control group. In the control group, these patients were only conducted to perform bilateral reaching movements by using a cross rod, But stroke patients in the experimental group executed the exercises on a linear guide platform with FES feedback control. The treatment time in both groups was during the same period. Before starting the intervention, each participant signed the document of informed consent in accordance with the NTUH Institutional Review Board (IRB). Criteria for both groups in this study were chosen in the following way. Inclusion criteria were: (1) clinical diagnosis of unilateral stroke; (2) able to understand and follow simple verbal instructions; (3) Brunnstrom stage for the arm less than IV; (4) no excessive spasticity in the affected arm (The modified Ashworth Scale (MAS) Љ 2); (5) unable to perform the active movements of full elbow extension. Exclusion criteria were: (1) upper limb comorbidities for limiting functional improvement; (2) unable to tolerate the level of FES needed for some visible muscle contractions; (3) the affected elbow contracture greater than 15 ̓ ; (4) unstable cardiopulmonary function. B. LINEAR GUIDE PLATFORM WITH FES FEEDBACK CONTROL This linear guide platform with FES feedback control was developed for upper-limb stroke rehabilitation (Fig.1). It consists of two linear guides and a self-triggered functional electrical stimulator. The resin ball recirculation components of the linear guides are to increase the smoothness and ensure the accuracy of high-speed motion. Two wooden-made handles on square areas (10x10 cm) are designed for each subject to grasp during training. One linear degree-of-freedom (DOF) enables stroke patients to guide the correct trajectories of forward reaching in the horizontal plane, and provide a little assistance to the bilateral reaching movements. In addition, the reaching length and the distance of two linear guides could be adjusted according to each subject’ arm length and shoulder width. To prevent over-reaching of the affected arm during FES application at higher stimulus intensity, an external cross rod is screwed ahead. A portable surface neuromuscular stimulator with 2 channels (TENSMED-931, Enraf-Nonius International, Netherlands) was used to deliver FES. It consists of 28 preset
programs and 5 custom programs. In this study, a customized program was selected so that the FES could combine with the linear guide platform, and be controlled easily by a computer. The parameters of TENSMED-931 were described as follows: Continuous electrical stimulation was with a frequency of 80 Hz. Although the stimulation frequency was higher than conventional ES, it may be adequate to induce enough muscle contractions to assist the movement of arm reaching. The pulse duration was a control variable (50~400 us) for safety considerations, and could be adjustable according to the severity of arm impairment after stroke.
Fig.1 a linear guide platform with FES feedback control Displacement data of both arm reaching could be collected via two linear wire potentiometers, then triggering a functional electrical stimulator (TENSMED-931).
A virtual instrumentation software platform, Lab VIEW ® 8.6 software (National Instruments, Austin, TX), were used for kinematic data acquisition, signal processing, and FES control programming. To receive the displacement data of both arms reaching during intervention, two linear wire potentiometers (HPS-S-R, HONTKO, CO., LTD., R.O.C. (Taiwan)) were to connect a computer via a DAQ board (NI USB-6008, National Instruments, Austin, TX). FES feedback control system utilizes displacement changes during arm reaching, which is developed to decide whether the FES trigger “on” or “off”. A block diagram of FES feedback control system is shown in Figure2. An input filter is to convert the electrical resistance to the displacement for lateral processing by the controller. The controller is to compute the error between the desired control signal (Xu ) and the actually signal (Xa). In the other words, as long as finding an error due to the affected arm falling behind, a control signal is sent to the actuator, FES trigger. The sensor is the potentiometers for providing feedback. Finally, there is a comparator to compare the difference between the input signal and the sensor output for further analyses.
Fig.2 Block diagram of FES feedback control system The controller is to compute the error between the desired control signal (Xu) and the actually signal (Xa). TENSMED-931 could deliver FES after being triggered “on”.
The Lab VIEW control interface (Fig. 3) allows interaction between users and the system. Some parameters are adjustable according to the condition of each subject, including “the initial length”, “the reaching length”, “left or right stroke”, and the training cycle. Kinematic trajectories of the affected arm could be shown simultaneously during the experiment for providing visual feedback. It is composed of “displacement graph”, “velocity graph”, “acceleration graph”, and “accelerator graph”.
Fig.3 LabVIEW control interface Some parameters could be adjustable, including “the initial length”, “the reaching length”, “left or right stroke”, and the training cycle. Kinematic trajectories of the affected arm could be shown simultaneously providing visual feedback.
C. EXPERIMENTAL Subjects received a proximately one-hour session twice a week, over a period of 3 weeks. That is, during the intervention period of totally 6 sessions, they practiced bilateral arm reaching movements. FES could provide extra assistance if necessary to help complete the full reaching movement. The details of pre-setting and the training experiment are described as follows:
Fig.4 An stroke subject underwent the training program of combined BAT with FES
Fig.5 during BAT, FES could provide assistance if necessary. Self-adhesive surface electrodes were placed on the motor point of the triceps brachii muscle and anterior deltoid muscle in the affected arm (right side) to facilitate muscle contractions.
Each subject sat upright in a chair with back support. Then, everyone was instructed to grasp the handles on the handle platforms of this training system, or use an elastic support bandage due to a nonfunctional hand. Two training movements were performed with repetitive rhythm: i) bilateral arm reaching, ii) drawing back (Fig.4). During each experiment, TENSMED-931 was triggered by the detection sensors of different distance due to the affected arm falling behind in forward reaching movements. It could deliver FES and induce muscle contractions via pairs of self-adhesive surface electrodes, placed on the motor point of the triceps brachii and anterior deltoid in the affected arm (Fig.5). The stimulation intensity ranged was set for providing enough assistance of reaching movements without pain. D. ASSESSMENT Subjects underwent assessment in their affected arms by a single blind physical therapist at three times: pre-treatment (week 0), post-treatment (week 3), and at one month follow-up (week 7). A basic physical examination was performed, such as stroke severity, muscle tone, muscle strength, etc. Clinical assessment included the Fugl-Meyer Assessment of the upper extremity section (FMA-UE), the Action Research Arm Test (ARAT), and the Motor Activity Log (MAL). Three evaluated scales have following characteristics: The FMA-UE is the most widely used for evaluating motor impairment in upper limb after stroke. The ARAT is a functional scale for measuring upper-extremity movements (both arm and hand) function. The MAL is a physical activity questionnaire which consists of the scores for the amount of use (AOU) and the quality of movement (QOM) of the paretic arm. Kinematic data were also collected as an objective description of what people perform a task based on spatio-temporal information. Furthermore, the compensation movements at the affected shoulder during experiment were also recorded by a 3-axis accelerometer (ADXL 330, Analog Device Inc., Norwood, MA).
E. STATISTICAL ANALYSIS Statistical data analyses were performed by SPSS 15.0 software, and the descriptive statistics were presented for the data sets. Levene’s test is a generalized test for relative variation. The normality test (the Shapiro-Wilk test), which tests the subjects’ baseline data, was to determine whether or not the parametric analysis is used. III. RESULTS Thirty five stroke patients were recruitment from NTU Hospital. Twenty three participants (10 in experiment group and 13 in control group) completed the treatment process. Outcome measures of clinical scales were to evaluate the effects of BAT combined with FES in patients with stroke, and it was performed as follows: An independent samples t-test compared both groups for similarity in subjects’ demographic data (Table. 1) and baseline clinical characteristics, and there were no statistical difference between two groups. According to the Shapiro-Wilk test, the frequency distribution of outcome measures was significantly different from a normal distribution on ARAT and MAL test, except for the FMA-UE test. As a result, both parametric and nonparametric statistics were suggested for further analysis. The significance level was set at α =0.05 (two-tailed P).
Wilcoxon Signed Ranks Test after treatment (p=0.011), and at follow-up (p=0.018) (Fig.7). However, the control group only had significant improvement after intervention (p=0.043), but not lasting at follow-up (p=0.596). The Mann-Whitney Test showed the statistical difference between two groups existed at follow-up (p=0.032). The MAL test (both AOU and QOM) revealed no significant difference was found for either between-group or within-group comparison (Fig.8). Both groups showed extremely low scores on the MAL-AOU and MAL-QOM. However, there was still a trend of improvement in the experimental group. CLINICAL OUTCOME MEASURES AMONG GROUPS Control
Experiment
- pre-treatment
28.37̈́18.02
27.47̈́9.77
- post-treatment
28.47̈́14.35
35.50̈́8.3
- follow-up
32.00̈́13.68
41.13̈́8.27
- pre-treatment
10.89̈́13.09
8.07̈́7.66
- post-treatment
11.24̈́13.43
12.00̈́9.44
9.75̈́10.91
21.75̈́11.61
- pre-treatment
0.31̈́0.65
0.01̈́0.05
- post-treatment
0.39̈́0.68
0.02̈́0.06
- follow-up
0.23̈́0.52
0.03̈́0.07
- pre-treatment
0.43̈́0.88
0.02̈́0.06
- post-treatment
0.38̈́0.80
0.02̈́0.06
- follow-up
0.26̈́0.55
0.03̈́0.07
FMA-UE
ARAT
- follow-up MAL-AOU
TABLE 1 SUBJECTS’ CHARACTERISTICS IN THE PRE-TREATMENT STAGE Control (n=19) 6/ 13
Experiment (n=16) 8/ 8
Age (yrs)
53.83̈́13.88
60.94̈́14.62
Post-stroke (months)
21.52̈́30.76
9.00̈́ 11.31
Gender(female/ male)
Affect side (right/ left)
11/ 8
9/ 7
Brunnstrom stage (stage) - proximal part (arm)
3.63 ̈́0.83
3.13 ̈́0.72
- distal part (hand)
3.11 ̈́1.10
2.88 ̈́1.31
Range of motion (normal/ limitation) 14/ 5 Data are present as mean ̈́ SD.
MAL-QOM
Data are present as mean ̈́ SD.
12/ 4
The clinical measurements of both groups were presented in Table. 2. Two-way mixed analysis of variance (ANOVA) was used for group comparison on the FMA-UE test. It revealed no statistical difference for either between-group (p=0.109) or within-group (p=0.085) comparison after intervention (Fig.6), but the scores were increased in the experimental group. It may imply that a favorable trend toward improvement existed in the experimental group after the training of BAT with FES. Data analyses of both the ARAT test and the MAL test were performed in the nonparametric statistics owing to its non-normal distribution. One the ARAT test, there were statistical difference within the experimental group using the
Fig. 6 FMA-UE scores in both groups (control and experiment) No significant difference was found either between two groups or within group using two-way ANOVA. Nevertheless, a trend toward improvement existed in the experimental group.
Fig. 7 ARAT scores in both groups (control and experiment) *P< 0.05 between groups and within group as indicated. Using the nonparametric test, statistical improvement was found in both groups. Yet the improvement in the control group could not last at follow-up. A significant difference between two groups was only found at follow-up.
Fig. 8 MAL scores in both groups (control and experiment) No significant difference was found either between two groups or within group using the nonparametric test. Both groups showed extremely low scores on the MAL-AOU and MAL-QOM. However, there was still a trend of improvement in the experimental group.
IV. DISCUSSION A. COMPARISON WITH PREVIOUS STUDIES FES has been widely used for stroke rehabilitation [27-28]. Prior studies showed that FES could improve body functions, such as increasing cardiorespiratory fitness [29], strengthening atrophied muscles, and moderation of spasticity. Based on neurological evidence, neural facilitation and brain plasticity were also found after FES therapy [30]. Besides, either higher or lower dose of FES has been reported to have a significant effect on the rehabilitation of upper-limb after
stroke [31]. There is increasing concern about clinical effect of combined BAT with FES in patient with stroke. The combination of BAT and FES revealed functional improvement in the affected hand of stroke patients in recent studies. In this paper, an intervention of BAT combined with FES focused on the affected arm in patients with stroke. To perform this training program, a customized linear guide platform with FES feedback control was designed. Particularly, it could provide low-cost but stable training equipment of bilateral arm reaching, which enables stroke patients to perform standard movements of symmetric bilateral reaching repetitively. Most importantly, self-triggered FES during elbow extension could augment the affected arm movements and increase cognitive attention through proprioceptive sensory feedback. Thus, motor learning may enhance the improvement of upper limb function in stroke patients. B. IMPROVEMENT OF ARM MOTOR FUNCTION The preliminary results obtained in this experiment proposed that the beneficial clinical effects of combined bilateral arm training with FES exist in patients with stroke. Although there was no statistical difference between the two groups, a favorable trend toward improvement was found in the experimental group after intervention, and at follow-up. These findings may imply that the effects of combined BAT with FES may be better than BAT alone. Analyzing the outcome measures of clinical scales, the FMA-UE scores reflected no significant difference using two-way mixed ANOVA. A possible factor could contribute to the assessment of FMA-UE consisting of both arm and hand ability. Concerning about the characteristics items in this test, improvement of proximal part (flexor and extensor synergy) and coordination ability were recorded in most subjects. An improvement of muscle strength in the proximal part of upper extremity was found. Besides, some subjects reflected the improvement of hand grasp ability after this training program.. The results suggested that some benefits in the distal part of upper extremities may exist regarding only the training of the affected arm. On the ARAT test, a significant improvement was found in the experimental group after-treatment, and at follow-up. But the statistical difference between two groups only showed at follow-up. Whether the carry-over effects of BAT with FES training exist or not, a variable training period would be suggested in further study. The MAL is an interview questionnaire that assesses the use of the paretic upper limb of stroke patients in daily activities [32-33]. Resulting from the subjects’ characteristics in Taiwan, there was something special that no matter how severity of the impaired arms, these stroke survivors seldom use their affected upper extremities to execute functional tasks. Hence, little significance was found using the MAL test. A home education program for using the affected arm is needed to provide assistance during activities of daily living.
V. CONCLUSIONS AND FUTURE WORKS This preliminary study demonstrated that the combination of BAT and FES on upper-limb motor function had clinical benefits in patients with stoke. The findings implied that the neural facilitation or brain plasticity may be induced through therapeutic exercises combined with self-triggered FES. Further analysis of kinematic data would be conducted. Besides, it is needed to assess whether or not to increase the treatment doses for better clinical effects. More functional approaches, such as the training program consisting of both arm and hand movements, would be also considered in upper limb rehabilitation after stroke.
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