Posts Tagged FES

[BLOG POST] Understanding the factors that impact the effectiveness of Functional Electrical Stimulation (FES) – pulse width and charge & torque

In the final of a series of blog articles, we are going to look at the factors that impact the effectiveness of FES. This one covers pulse width and charge & torque.

Read the first article here

Read the second article here

Pulse width

The available pulse widths in FES devices vary, most commonly between 150 and 300us, however much wider variations (50us to 2500us) in pulse width can have differing effects upon the target muscle tissue.

Practically, a longer pulse width causes the stimulus to remain in the tissues for longer, depolarising a greater number of nerve fibres, indiscriminate of motor, sensory or pain. Higher pulse widths have been shown to generate greater levels of torque and can often allow tetanic muscle contractions resulting in physiological joint movement at lower levels of amplitude, which can be useful when attempting to maximise torque in those with intact sensation.

However, when looking for a specific muscle contraction, for example a bicep’s, if too great a pulse width is applied it is common to see overflow into surrounding or opposing muscle groups. Compared to pulse frequency and current amplitude, the role of pulse duration is less appreciated in its possible influence on maximising torque output.

Alon et al back in 1983 showed that motor stimulation could be achieved with pulse durations in the range of 20 to 200 microseconds, without stimulation of pain response. In contrast, Hultman et al (1983) showed that a pulse duration of 500 microseconds resulted in 40% greater torque output compared to 150 microseconds.

Moreover, a pulse duration of 450 microseconds has been shown to be effective in conducting electrically induced resistance training in individuals with spinal cord injury (Kendell et al., 2006, Burnham et al., 1997, cited by Dolbow and Gorgey, 2016).

However, despite this evidence, most researchers have used pulse durations of 300 microseconds or below in their studies, which could potentially limit the outcome of Neuromuscular Electric Stimulation (NMES) protocols in maximising elicited torque output. The controversy regarding pulse duration selection reflects the limited amount of knowledge regarding the optimal pulse duration required to maximise torque output.

Charge & Torque

Total charge, the product of combined amplitude and pulse width, determines the force produced from the resultant muscle contraction. Maximising the charge, by applying maximal amplitude and pulse width, is likely to result in the maximum torque.

However, as stated above, patient tolerance is the determinant of how much charge may be applied. Manipulating both amplitude and pulse width can help to generate sufficient charge to result in a forceful muscle contraction, without becoming unbearable for the patient.

This article is taken from our white paper “The integration of Functional Electrical Stimulation (FES) technology and neurorehabilitation”.

via Understanding the factors that impact the effectiveness of Functional Electrical Stimulation (FES) – pulse width and charge & torque | Cyclone

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[Abstract + References] A Multi-channel EMG-Driven FES Solution for Stroke Rehabilitation – Conference paper

Abstract

Functional electrical stimulation (FES) has been applied to stroke rehabilitation for many years. However, users are usually involved in open-loop fixed cycle FES systems in clinical, which is easy to cause muscle fatigue and reduce rehabilitation efficacy. This paper proposes a multi-surface EMG-driven FES integration solution for enhancing upper-limb stroke rehabilitation. This wireless portable system consists of sEMG data acquisition module and FES module, the former is used to capture sEMG signals, the latter of multi-channel FES output can be driven by the sEMG. Preliminary experiments proved that the system has outperformed existing similar systems and that sEMG can be effectively employed to achieve different FES intensity, demonstrating the potential for active stroke rehabilitation.

References

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    Lynch, C.L., Popovic, M.R.: Functional electrical stimulation. IEEE Control Syst. 28(2), 40–50 (2008)MathSciNetCrossRefGoogle Scholar
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    Liberson, W.: Functional electrotherapy: stimulation of the peroneal nerve synchronized with the swing phase of the gait of hemiplegic patients. Arch. Phys. Med. Rehabil. 42, 101 (1961)Google Scholar
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    Popović, D.B.: Advances in functional electrical stimulation (FES). J. Electromyogr. Kinesiol. 24(6), 795–802 (2014)CrossRefGoogle Scholar
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    Lyons, G.M., Sinkjær, T., Burridge, J.H., Wilcox, D.J.: A review of portable FES-based neural orthoses for the correction of drop foot. IEEE Trans. Neural Syst. Rehabil. Eng. 10(4), 260–279 (2002)CrossRefGoogle Scholar
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    Edgerton, V.R., Roy, R.R.: Robotic training and spinal cord plasticity. Brain Res. Bull. 78(1), 4–12 (2009)CrossRefGoogle Scholar
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    Lotze, M., Braun, C., Birbaumer, N., Anders, S., Cohen, L.G.: Motor learning elicited by voluntary drive. Brain 126(4), 866–872 (2003)CrossRefGoogle Scholar
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    Quandt, F., Hummel, F.C.: The influence of functional electrical stimulation on hand motor recovery in stroke patients: a review. Exp. Trans. Stroke Med. 6(1), 9 (2014)CrossRefGoogle Scholar
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    Hong, I.K., Choi, J.B., Lee, J.H.: Cortical changes after mental imagery training combined with electromyography-triggered electrical stimulation in patients with chronic stroke. Stroke 43(9), 2506–2509 (2012)CrossRefGoogle Scholar
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    Fujiwara, T.: Motor improvement and corticospinal modulation induced by hybrid assistive neuromuscular dynamic stimulation (hands) therapy in patients with chronic stroke. Neurorehabilitation Neural Repair 23(2), 125–132 (2009)CrossRefGoogle Scholar
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    Fang, Y., Zhu, X., Liu, H.: Development of a surface EMG acquisition system with novel electrodes configuration and signal representation. In: Lee, J., Lee, M.C., Liu, H., Ryu, J.-H. (eds.) ICIRA 2013. LNCS (LNAI), vol. 8102, pp. 405–414. Springer, Heidelberg (2013).  https://doi.org/10.1007/978-3-642-40852-6_41CrossRefGoogle Scholar
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    Forvi, E., et al.: Preliminary technological assessment of microneedles-based dry electrodes for biopotential monitoring in clinical examinations. Sens. Actuators A Phys. 180, 177–186 (2012)CrossRefGoogle Scholar

via A Multi-channel EMG-Driven FES Solution for Stroke Rehabilitation | SpringerLink

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[Abstract] Combining functional electrical stimulation and mirror therapy for upper limb motor recovery following stroke: a randomised trial

Introduction: There is a growing need to develop effective rehabilitation interventions for people presenting with stroke as healthcare services experience ever-increasing pressures on staff and resources. The primary objective of this research is to examine the effect that mirror therapy combined with functional electrical stimulation has on upper limb motor recovery and functional outcome for a sample of people admitted to an inpatient stroke unit.

Methods: A total of 50 participants were randomised to one of three treatment arms; Functional Electrical Stimulation, Mirror therapy or a combined intervention of Functional Electrical Stimulation with Mirror therapy. Socio-demographic and health information was collected at recruitment together with admission dates, medical diagnoses and baseline measures. Blinded assessments were undertaken at baseline and at discharge post-stroke by a registered physiotherapist and a clinical nurse specialist.

Results: The Action Research Arm Test and the Fugl–Meyer Upper Extremity assessment revealed statistically superior results for Functional Electrical Stimulation compared with Mirror therapy alone (p = 0.03). There were no other significant differences between the three groups.

Conclusion: The theory of combining interventions requires further investigation and warrants further research. Combining current interventions may have the potential to enhance stroke rehabilitation, improve functional outcomes and help reduce the overall burden of stroke.

 

via Combining functional electrical stimulation and mirror therapy for upper limb motor recovery following stroke: a randomised trial: European Journal of Physiotherapy: Vol 0, No 0

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[Abstract + References] Using Orientation Sensors to Control a FES System for Upper-Limb Motor Rehabilitation

Abstract

Contralaterally controlled functional electrical stimulation (CCFES) is a recent therapy aimed at improving the recovery of impaired limbs after stroke. For hemiplegic patients, CCFES uses a control signal from the non-impaired side of the body to regulate the intensity of electrical stimulation delivered to the affected muscles of the homologous limb on the opposite side of the body. CCFES permits an artificial muscular contraction synchronized with the patient’s intentionality to carry out functional tasks, which is a way to enhance neuroplasticity and to promote motor learning. This work presents an upper extremity motor rehabilitation system based on CCFES, using orientation sensors for control. Thus, the stimulation intensity (current amplitude) delivered to the paretic extremity is proportional to the degree of joint amplitude of the unaffected extremity. The implemented controller uses a control strategy that allows the delivered electrical stimulation intensity, to be comparable to the magnitude of movement. It was carried out a set of experiments to validate the overall system, for executing five bilateral mirror movements that include human wrist and elbow joints. Obtained results showed that movements voluntary signals acquired from right upper-limb were replicated successfully on left upper-limb using the FES system.

References

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    World Report on Disability, World Health Organization (WHO) (2011)Google Scholar
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    Moller, A.R.: Neural Plasticity and Disorders of the Nervous System. Cambridge University Press, Cambridge (2006)CrossRefGoogle Scholar
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    Hara, Y., Obayashi, S., Tsujiuchi, K., Muraoka, Y.: The effects of electromyography controlled functional electrical stimulation on upper extremity function and cortical perfusion in stroke patients. Clin. Neurophysiol. 124, 2008–2015 (2013)CrossRefGoogle Scholar
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    Sheffler, L., Chae, J.: Neuromuscular electrical stimulation in neurorehabilitation. Muscle Nerve 35, 562–590 (2007)CrossRefGoogle Scholar
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    Doucet, B.M., Lamb, A., Griffin, L.: Neuromuscular electrical stimulation for skeletal muscle function. Yale J. Biol. Med. 85, 201–215 (2012)Google Scholar
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    Popovic, D.B., Sinkjærc, T., Popovic, M.B.: Electrical stimulation as a means for achieving recovery of function in stroke patients. NeuroRehabilitation 25, 45–58 (2009)Google Scholar
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    Knutson, J.S., Harley, M.Y., Hisel, T.Z., Makowski, N.S., Fu, M.J., Chae, J.: Contralaterally controlled functional electrical stimulation for stroke rehabilitation. In: Proceedings of IEEE Engineering and Medicine and Biology Society, pp. 314–317 (2012)Google Scholar
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    Knutson, J.S., Harley, M.Y., Hisel, T.Z., Makowski, N.S., Chae, J.: Contralaterally controlled functional electrical stimulation for recovery of elbow extension and hand opening after stroke: a pilot case series study. Am. J. Phys. Med. Rehabil. 93(6), 528–539 (2014)CrossRefGoogle Scholar
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    Sabatini, A.M.: Estimating three-dimensional orientation of human body parts by inertial/magnetic sensing. Sensors 11, 1489–1525 (2011)CrossRefGoogle Scholar
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    Filippeschi, A., Schmitz, N., Miezal, M., Bleser, G., Ruffaldi, E., Stricker, D.: Survey of motion tracking methods based on inertial sensors: a focus on upper limb human motion. Sensors 17, 1257 (2017)CrossRefGoogle Scholar
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    Borbély, B.J., Szolgay, P.: Real-time inverse kinematics for the upper limb: a model-based algorithm using segment orientations. Biomed. Eng. Online 2017(16), 21 (2017)CrossRefGoogle Scholar
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    Lynch, C., Popovic, M.: Functional electrical stimulation: closed-loop control of induced muscle contractions. IEEE Control Syst. Mag. 28, 40–49 (2008)MathSciNetCrossRefGoogle Scholar
  13. 13.
    Ferrarin, M., Palazzo, F., Riener, R., Quintern, J.: Model-based control of FES-induced single joint movements. IEEE Trans. Neural Syst. Rehabil. Eng. 9(3), 245–257 (2001)CrossRefGoogle Scholar
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    Knutson, J.S., Gunzler, D.D., Wilson, R.D., Chae, J.: Contralaterally controlled functional electrical stimulation improves hand dexterity in chronic hemiparesis. Stroke. 47(12), 2596–2602 (2016)CrossRefGoogle Scholar

via Using Orientation Sensors to Control a FES System for Upper-Limb Motor Rehabilitation | SpringerLink

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[Abstract] Within-session effects of selected physical rehabilitation interventions for a dysfunctional arm post-stroke on arm movement and muscle firing patterns

Introduction/Background

Upper extremity (UE) impairments and activity limitations are a common problem in individuals following a cerebrovascular accident (CVA). Eighty-five percent of individuals with CVA report UE functional limitations that are associated with decreased health-related quality of life. Occupational therapy (OT) and physical therapy (PT) approaches are typically aimed to treat impairments, activity limitations, and participation restrictions following a CVA. This study examines the effects of five therapeutic approaches on upper extremity (UE) movement and muscle activation patterns in persons with CVAs: (1) proprioceptive neuromuscular facilitation (PNF); (2) neurodevelopmental treatment (NDT); (3) functional electrical stimulation (FES); (4) weight-bearing and (5) modified Constraint-Induced Movement Therapy (mCIMT).

Material and method

This is a case report involving a 61-year-old male who underwent 30-minute intervention sessions for each approach stated above. Electromyography (EMG) and 3D motion capture data were collected pre- and post-intervention and at 30 minute follow-up. Data were analyzed for reaching a cup at waist level, maximum shoulder flexion, and moving cup to mouth as in drinking.

Results

No significant differences were seen for UE movements across all interventions for kinematic or EMG data. There appears to be a trend towards normal elbow movement following NMES, mCIMT and PNF and increased variability in shoulder flexion in mCIMT and NDT interventions. Weight-bearing provided the least amount of evidence for improved kinematic motion. Improvement in elbow kinematics may indicate proximal stability following PNF, FES, and mCIMT allows for increased distal mobility at the elbow.

Conclusion

Some interventions produced trends that indicate better UE movement. Increased proximal stability may have caused better distal mobility as shown by improved elbow movement. Increased variability of shoulder flexion may indicate the participant learned different options to perform the same movement. Further research is needed o provide a more transparent understanding of the efficacy of interventions for individuals with hemiparesis following a CVA.

 

via Within-session effects of selected physical rehabilitation interventions for a dysfunctional arm post-stroke on arm movement and muscle firing patterns – ScienceDirect

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[Abstract] Hybrid robotic system combining passive exoskeleton and functional electrical stimulation for upper limb stroke rehabilitation: Preliminary results of the retrainer multi-center randomized controlled trial

Introduction/Background

Stroke is the main cause of acquired adult disability with major impact on arm function. The combined use of Functional Electrical Stimulation (FES) and robotic technologies is strongly advocated to improve rehabilitation outcomes after stroke. We present the preliminary data of a multi-center Randomized Controlled Trial aimed at evaluating the effectiveness of this system with respect to conventional therapy for sub-acute stroke upper limb rehabilitation.

Material and method

The RETRAINER system consists of a lightweight and non-cumbersome passive arm exoskeleton for weight relief, a current-controlled stimulator with 2 channels of stimulation and 2 channels of EMG recordings.

In this work we are presenting the preliminary results of 39 sub-acute stroke patients with a distance from the acute event between two weeks and nine months. The inclusion criteria was: age between 18 and 85 years, Motricity Index (MI) < 80%, muscular activity for arm and shoulder at least 1 Medical Research Council (MRC) with a visible contraction, no joint limitation, pain or spasticity. They were randomized in two group: 1 conventional rehabilitation methods, 2 experimental group using Retrainer System. Each participant performed 9 weeks of treatment 3 times for week. We measured MI, Action Research Arm Test (ARAT) and Motor Activity Log (MAL) at beginning (T0) and at the end of treatment (T1).

Results

Results are showed in the next Table 1.

Conclusion

Both groups showed statistical improvement in outcome measures. Experimental group showed a statistical better improvement regarding time and group effect.

 

via Hybrid robotic system combining passive exoskeleton and functional electrical stimulation for upper limb stroke rehabilitation: Preliminary results of the retrainer multi-center randomized controlled trial – ScienceDirect

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[Abstract] A brain–computer interface based stroke rehabilitation system, controlling an avatar and functional electrical stimulation, to improve motor functions

Introduction/Background

Brain–computer interfaces (BCI) can detect the neuronal activity of patients’ motor intention to control external devices. With the feedback from the device, the neuronal network in the brain to reorganizes due to neuroplasticity.

Material and method

The BCI controls an avatar and functional electrical stimulation (FES) to provide the feedback. The expected task for the patient is to imagine either left or right wrist dorsiflexion according to the instructions. The training was designed to have 25 sessions (240 trials of either left or right motor imagery) of BCI feedback sessions over 13 weeks. Two days before and two days after we did clinical measures to observe motor improvement. The primary measure was upper extremity Fugl–Meyer assessment (UE-FMA), which evaluates the motor impairment. Four secondary measures were also performed to exam the spasm (modified Ashworth scale, MAS), tremor (Fahn tremor rating scale, FTRS), level of daily activity (Barthel index, BI), and finger dexterity (9-hole peg test, 9HPT).

Results

One male stroke patient (53 years old, 11 months since stroke, and right upper limb paralyzed) participated in the training. He quickly learned to use the BCI and the maximal classification accuracy was over 90% after the 5th session. The UE-FMA increased from 25 to 46 points. The BI increased from 90 to 95 points. MAS and FTRS decreased from 2 to 1 and from 4 to 3 points respectively. Although he could not conduct the 9HPT until 18th training session, he was able to complete the test from 19th session in 10 min 22 s and the time was reduced to 2 min 53 s after 25th session.

Conclusion

The patient could be more independent in his daily activity, he had less spasticity and tremor. Also, the 9HPT was possible to do, which was not before. The system is currently validated with a study of 50 patients.

 

via A brain–computer interface based stroke rehabilitation system, controlling an avatar and functional electrical stimulation, to improve motor functions – ScienceDirect

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[Case Report] Case report on the use of a functional electrical orthosis in rehabilitation of upper limb function in a chronic stroke patient – Full Text PDF

Abstract

Introduction. The increasing incidence of strokes and their occurrence in younger active people require the development of solutions that allow participation, despite the debilitating deficit that is not always solved by rehabilitation. The present report shows
such a potential solution.
Objective. In this presentation we will show the effects of using a functional electric orthosis, the high number of repetitions and daily electrostimulation in a young stroke patient with motor deficit in the upper limb, the difficulties encountered in attempting to
use orthosis, the results and the course of its recovery over the years.
Materials and Methods. The present report shows the evolution of a 31-year-old female patient with hemiplegia, resulting from a hemorrhagic stroke, from the moment of surgery to the moment of purchasing a functional electrical orthosis and a few months
later, highlighting a 3-week period when the training method focused on performing a large number of repetitions of a single exercise helped by the orthosis – 3 weekly physical therapy sessions, with a duration of one hour and 15 minutes, plus 2 electrostimulation sessions lasting 20 minutes each and 100 elbow extension, daily, 6 times a week. The patient was evaluated and filmed at the beginning and end of the 3 week period. The patient’s consent was obtained for the use of the data and images presented.
Results. Invalidating motor deficiency and problems specific to the use of upper limb functional electrostimulation in patients with stroke sequelae (flexion synergy, exaggeration of reflex response, wrist position during stimulation, etc.) made it impossible to use orthosis in functional activities within ADL although it allowed the achievement of a single task. Evaluation on the FuglMayer assessment does not show any quantifiable progress, although it is possible to have slightly improved the control of the
shoulder and elbow and increased the speed of task execution.
Conclusions. The use of functional orthoses of this type may be useful in patients who still have a significant functional rest in the shoulder, elbow and hand, and where the orthosis can produce an effective grasp. However for some patients, perhaps those who
would have been desirable to benefit most from this treatment, the benefit of using this orthosis is minimal.[…]

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[WEB SITE] Scientists develop combined therapy for stroke victim recovery

Scientists in Switzerland have demonstrated that combining a brain-computer interface (BCI) with functional electrical stimulation (FES) can help stroke victims recover greater use of their paralysed limbs – even years after the stroke.

 

stroke-brain-computer-interface

 

Paralysis of an arm and/or leg is one of the most common results of a stroke. However, a team of scientists at the Defitech Foundation Chair in Brain-Machine Interface, in association with other members of EPFL’s Center for Neuroprosthetics, the Clinique Romande de Réadaptation in Sion, and the Geneva University Hospitals, have developed a technique aimed at enabling stroke victims to recover greater use of their paralysed limbs. The scientists’ pioneering approach utilises two existing therapies – a brain-computer interface (BCI) and functional electrical stimulation (FES).

Explaining the key to their approach, José del R. Millán, who holds the Defitech Chair at EPFL, said: “The key is to stimulate the nerves of the paralysed arm precisely when the stroke-affected part of the brain activates to move the limb, even if the patient can’t actually carry out the movement. That helps re-establish the link between the two nerve pathways where the signal comes in and goes out.”.

Combined therapy tested on stroke patients

Twenty-seven patients aged between 36 and 76 took part in the clinical trial. All had a similar lesion that resulted in moderate to severe arm paralysis following a stroke occurring at least ten months earlier. Half of the patients were treated with the scientists’ dual-therapy approach and reported clinically significant improvements. The other half were treated only with FES and served as a control group.

For the first group, the scientists used a BCI system to link the patients’ brains to computers by means of electrodes. This enabled them to pinpoint exactly where the electrical activity occurred in the brain tissue when the patients tried to reach out their hands. Each time the electrical activity was identified the system immediately stimulated the arm muscle controlling the corresponding wrist and finger movements. The patients in the second group also had their arm muscles stimulated, but at random times. This control group enabled the scientists to determine how much of the additional motor-function improvement could be attributed to the BCI system.

 

The scientists noted a significant improvement in arm mobility among patients in the first group after just ten one-hour sessions. When the full round of treatment was completed, some of the first-group patients’ scores on the Fugl-Meyer Assessment – a test used to evaluate motor recovery among patients with post-stroke hemiplegia – were over twice as high as those of the second group.

“Patients who received the BCI treatment showed more activity in the neural tissue surrounding the affected area. Due to their plasticity, they could help make up for the functioning of the damaged tissue,” says Millán.

 

Electroencephalographies (EEGs) of the patients clearly showed an increase in the number of connections among the motor cortex regions of their damaged brain hemisphere, which corresponded with the increased ease in carrying out the associated movements. In addition, the enhanced motor function didn’t seem to diminish with time. Evaluated again 6-12 months later, the patients were found to have lost none of their recovered mobility.

The study results were published in Nature Communications.

via Scientists develop combined therapy for stroke victim recovery

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[ARTICLE] Brain-actuated functional electrical stimulation elicits lasting arm motor recovery after stroke – Full Text

Abstract

Brain-computer interfaces (BCI) are used in stroke rehabilitation to translate brain signals into intended movements of the paralyzed limb. However, the efficacy and mechanisms of BCI-based therapies remain unclear. Here we show that BCI coupled to functional electrical stimulation (FES) elicits significant, clinically relevant, and lasting motor recovery in chronic stroke survivors more effectively than sham FES. Such recovery is associated to quantitative signatures of functional neuroplasticity. BCI patients exhibit a significant functional recovery after the intervention, which remains 6–12 months after the end of therapy. Electroencephalography analysis pinpoints significant differences in favor of the BCI group, mainly consisting in an increase in functional connectivity between motor areas in the affected hemisphere. This increase is significantly correlated with functional improvement. Results illustrate how a BCI–FES therapy can drive significant functional recovery and purposeful plasticity thanks to contingent activation of body natural efferent and afferent pathways.

Introduction

Despite considerable efforts over the last decades, the quest for novel treatments for arm functional recovery after stroke remains a priority1. Synergistic efforts in neural engineering and restoration medicine are demonstrating how neuroprosthetic approaches can control devices and ultimately restore body function2,3,4,5,6,7. In particular, non-invasive brain-computer interfaces (BCI) are reaching their technological maturity8,9 and translate neural activity into meaningful outputs that might drive activity-dependent neuroplasticity and functional motor recovery10,11,12. BCI implies learning to modify the neuronal activity through progressive practice with contingent feedback and reward —sharing its neurobiological basis with rehabilitation13.

Most attempts to use non-invasive BCI systems for upper limb rehabilitation after stroke have coupled them with other interventions, although not all trials reported clinical benefits. The majority of these studies are case reports of patients who operated a BCI to control either rehabilitation robots14,15,16,17,18,19 or functional electrical stimulation (FES)20,21,22,23. A few works have described changes in functional magnetic resonance imaging (fMRI) that correlate with motor improvements17,18,22.

Recent controlled trials have shown the potential benefit of BCI-based therapies24,25,26,27. Pichiorri et al.26recruited 28 subacute patients and studied the efficacy of motor imagery with or without BCI support via visual feedback, reporting a significant and clinically relevant functional recovery for the BCI group. As a step forward in the design of multimodal interventions, BCI-aided robotic therapies yielded significantly greater motor gains than robotic therapies alone24,25,27. In the first study, involving 30 chronic patients24, only the BCI group exhibited a functional improvement. In the second study, involving 14 subacute and chronic patients, both groups improved, probably reflecting the larger variance in subacute patients’ recovery and a milder disability25. The last study27 showed that in a mixed population of 74 subacute and chronic patients, the percentage of patients who achieved minimally clinical important difference in upper limb functionality was higher in the BCI group. The effect in favor of the BCI group was only evident in the sub-population of chronic patients. Moreover, the conclusions of this study are limited due to differences between experimental and control groups prior to the intervention, such as number of patients and FMA-UE scores, which were always in favor of the BCI group.

In spite of promising results achieved so far, BCI-based stroke rehabilitation is still a young field where different works report variable clinical outcomes. Furthermore, the efficacy and mechanisms of BCI-based therapies remain largely unclear. We hypothesize that, for BCI to boost beneficial functional activity-dependent plasticity able to attain clinically important outcomes, the basic premise is contingency between suitable motor-related cortical activity and rich afferent feedback. Our approach is designed to deliver associated contingent feedback that is not only functionally meaningful (e.g., via virtual reality or passive movement of the paretic limb by a robot), but also tailored to reorganize the targeted neural circuits by providing rich sensory inputs via the natural afferent pathways28, so as to activate all spare components of the central nervous system involved in motor control. FES fulfills these two properties of feedback contingent on appropriate patterns of neural activity; it elicits functional movements and conveys proprioceptive and somatosensory information, in particular via massive recruitment of Golgi tendon organs and muscle spindle feedback circuits. Moreover, several studies suggest that FES has an impact on cortical excitability29,30.

To test our hypothesis, this study assessed whether BCI-actuated FES therapy targeting the extension of the affected hand (BCI–FES) could yield stronger and clinically relevant functional recovery than sham-FES therapy for chronic stroke patients with a moderate-to-severe disability, and whether signatures of functional neuroplasticity would be associated with motor improvement. Whenever the BCI decoded a hand-extension attempt, it activated FES of the extensor digitorum communis muscle that elicited a full extension of the wrist and fingers. Patients in the sham-FES group wore identical hardware and received identical instructions as BCI–FES patients, but FES was delivered randomly and not driven by neural activity.

As hypothesized, our results confirm that only the BCI group exhibit a significant functional recovery after the intervention, which is retained 6–12 months after the end of therapy. Besides the main clinical findings, we have also attempted to shed light on possible mechanisms underlying the proposed intervention. Specifically, electroencephalography (EEG) imaging pinpoint significant differences in favor of the BCI group, mainly an increase in functional connectivity between motor areas in the affected hemisphere. This increase is significantly correlated with functional improvement. Furthermore, analysis of the therapeutic sessions substantiates that contingency between motor-related brain activity and FES occurs only in the BCI group and contingency-based metrics correlate with the functional improvement and increase in functional connectivity, suggesting that our BCI intervention might have promoted activity-dependent plasticity.[…]

Continue —> Brain-actuated functional electrical stimulation elicits lasting arm motor recovery after stroke | Nature Communications

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