Therapy of paretic arm in hemiplegic subjects augmented with a neural prosthesis: a cross-over study

A novel functional electrical stimulation treatment for recovery of hand function in hemiplegia: 12-week pilot study

BACKGROUND

Loss of finger extension is common after stroke and can severely limit hand function. Contralaterally controlled functional electrical stimulation (CCFES) is a new treatment aimed at restoring volitional finger and thumb extension. A previous pilot study showed reductions in hand impairment after 6 weeks of CCFES, but the effect did not persist after end of treatment.

OBJECTIVE

This study aimed to evaluate the feasibility of achieving greater and more persistent gains with CCFES by increasing the treatment period to 12 weeks.

METHODS

CCFES uses neuromuscular electrical stimulation to open the paretic hand in direct proportion to the degree of volitional opening of the unimpaired contralateral hand, which is detected by an instrumented glove. Three subjects with chronic hemiplegia participated in a 12-week CCFES treatment, which consisted of daily CCFES-assisted active repetitive hand-opening exercises and twice weekly functional task practice with CCFES.

RESULTS

Maximum voluntary finger extension increased by 101 degrees and 68 degrees for subjects 1 and 2, respectively, but subject 3 had no improvement in finger extension. Box and Block score increased by 6, 15, and 7 blocks, and upper extremity Fugl-Meyer score increased by 11, 15, and 7 points for subjects 1, 2, and 3, respectively. The finger extension gains declined at the 1-month and 3-month follow-up for subjects 1 and 2, but the gains in Box and Block and Fugl-Meyer scores persisted at follow-up.

CONCLUSIONS

Greater reductions in hand impairment were achieved by extending the treatment period. The effect and its longevity may be related to baseline impairment level.

Synergistic control of forearm based on accelerometer data and artificial neural networks

In the present study, we modeled a reaching task as a two-link mechanism. The upper arm and forearm motion trajectories during vertical arm movements were estimated from the measured angular accelerations with dual-axis accelerometers. A data set of reaching synergies from able-bodied individuals was used to train a radial basis function artificial neural network with upper arm/forearm tangential angular accelerations. The trained radial basis function artificial neural network for the specific movements predicted forearm motion from new upper arm trajectories with high correlation (mean, 0.9149-0.941). For all other movements, prediction was low (range, 0.0316-0.8302). Results suggest that the proposed algorithm is successful in generalization over similar motions and subjects. Such networks may be used as a high-level controller that could predict forearm kinematics from voluntary movements of the upper arm. This methodology is suitable for restoring the upper limb functions of individuals with motor disabilities of the forearm, but not of the upper arm. The developed control paradigm is applicable to upper-limb orthotic systems employing functional electrical stimulation. The proposed approach is of great significance particularly for humans with spinal cord injuries in a free-living environment. The implication of a measurement system with dual-axis accelerometers, developed for this study, is further seen in the evaluation of movement during the course of rehabilitation. For this purpose, training-related changes in synergies apparent from movement kinematics during rehabilitation would characterize the extent and the course of recovery. As such, a simple system using this methodology is of particular importance for stroke patients. The results underlie the important issue of upper-limb coordination.

A four-week, task-specific neuroprosthesis program for a person with no active wrist or finger movement because of chronic stroke

BACKGROUND AND PURPOSE

This case report describes a task-specific training protocol incorporating functional electrical stimulation for a person who had chronic stroke and who initially exhibited no active wrist or finger movement.

CASE DESCRIPTION

A 63-year-old man with hemiparesis caused by an ischemic stroke 7 years before the intervention described here received task-specific training incorporating an electrical stimulation neuroprosthesis 3 hours per day, 5 days per week, for 4 weeks. Testing was conducted before and after the intervention and again 6 weeks later with stroke-specific outcome measures.

OUTCOMES

Increases in function and quality of life were observed after the intervention.

DISCUSSION

An intervention incorporating task-specific training with functional electrical stimulation appears to have increased function and quality of life in a person with chronic stroke. This type of intervention might provide a pathway by which people with similar impairments would become eligible for more advanced treatment regimens, such as modified constraint-induced therapy.

A neural tracking and motor control approach to improve rehabilitation of upper limb movements

Background

Restoration of upper limb movements in subjects recovering from stroke is an essential keystone in rehabilitative practices. Rehabilitation of arm movements, in fact, is usually a far more difficult one as compared to that of lower extremities. For these reasons, researchers are developing new methods and technologies so that the rehabilitative process could be more accurate, rapid and easily accepted by the patient. This paper introduces the proof of concept for a new non-invasive FES-assisted rehabilitation system for the upper limb, called smartFES (sFES), where the electrical stimulation is controlled by a biologically inspired neural inverse dynamics model, fed by the kinematic information associated with the execution of a planar goal-oriented movement. More specifically, this work details two steps of the proposed system: an ad hoc markerless motion analysis algorithm for the estimation of kinematics, and a neural controller that drives a synthetic arm. The vision of the entire system is to acquire kinematics from the analysis of video sequences during planar arm movements and to use it together with a neural inverse dynamics model able to provide the patient with the electrical stimulation patterns needed to perform the movement with the assisted limb.

Methods

The markerless motion tracking system aims at localizing and monitoring the arm movement by tracking its silhouette. It uses a specifically designed motion estimation method, that we named Neural Snakes, which predicts the arm contour deformation as a first step for a silhouette extraction algorithm. The starting and ending points of the arm movement feed an Artificial Neural Controller, enclosing the muscular Hill's model, which solves the inverse dynamics to obtain the FES patterns needed to move a simulated arm from the starting point to the desired point. Both position error with respect to the requested arm trajectory and comparison between curvature factors have been calculated in order to determine the accuracy of the system.

Results

The proposed method has been tested on real data acquired during the execution of planar goal-oriented arm movements. Main results concern the capability of the system to accurately recreate the movement task by providing a synthetic arm model with the stimulation patterns estimated by the inverse dynamics model. In the simulation of movements with a length of ± 20 cm, the model has shown an unbiased angular error, and a mean (absolute) position error of about 1.5 cm, thus confirming the ability of the system to reliably drive the model to the desired targets. Moreover, the curvature factors of the factual human movements and of the reconstructed ones are similar, thus encouraging future developments of the system in terms of reproducibility of the desired movements.

Conclusion

A novel FES-assisted rehabilitation system for the upper limb is presented and two parts of it have been designed and tested. The system includes a markerless motion estimation algorithm, and a biologically inspired neural controller that drives a biomechanical arm model and provides the stimulation patterns that, in a future development, could be used to drive a smart Functional Electrical Stimulation system (sFES). The system is envisioned to help in the rehabilitation of post stroke hemiparetic patients, by assisting the movement of the paretic upper limb, once trained with a set of movements performed by the therapist or in virtual reality. Future work will include the application and testing of the stimulation patterns in real conditions.

Hybrid assistive systems for rehabilitation: lessons learned from functional electrical therapy in hemiplegics

This paper suggests that the optimal method for promoting of the recovery of upper extremity function in hemiplegic individuals is the use of hybrid assistive systems (HAS). The suggested HAS is a combination of stimulation of paralyzed distal segments (hand) in synchrony with robot controlled movements of proximal segments (upper arm and forearm). The use of HAS is envisioned as part of voluntary activation of preserved sensory-motor systems during task related exercise. This HAS design follows our results from functional electrical therapy, constraint induced movement therapy, intensive exercise therapy, and use of robots for rehabilitation. The suggestion is also based on strong evidences that cortical plasticity is best promoted by task related exercise and patterned electrical stimulation.

Neuromodulation by functional electrical stimulation (FES) of limb paralysis after stroke

Functional Electrical Stimulation (FES) in stroke patients has been demonstrated to provide clinical benefits such as improvement in movement, skills, function and decrease of spasticity. Imaging and neurophysiological studies have shown cortical excitability and reorganization. After injury, the parameters of timing, intensity, frequency, and duration of FES are still to be determined. Additional issues that should be determined are whether the changes induced by FES are long-lasting, and which clinical and electrophysiological parameters are important and to what extent.

Upper-Extremity Functional Electric Stimulation–Assisted Exercises on a Workstation in the Subacute Phase of Stroke Recovery

OBJECTIVE

To test the efficacy of functional electric stimulation (FES)-assisted exercise therapy (FES-ET) on a workstation in the subacute phase of recovery from a stroke.

DESIGN

Single-blind, randomly controlled comparison of high- and low-intensity treatment.

SETTING

Laboratory in a rehabilitation hospital.

PARTICIPANTS

Nineteen stroke survivors (10 men, 9 women; mean age +/- standard deviation, 60.6+/-5.8y), with upper-extremity hemiplegia (mean poststroke time, 48+/-17d). The main inclusion criteria were: stroke occurred within 3 months of onset of trial and resulted in severe upper-limb dysfunction, and FES produced adequate hand opening.

INTERVENTION

An FES stimulator and an exercise workstation with instrumented objects were used by 2 groups to perform specific motor tasks with their affected upper extremity. Ten subjects in the high-intensity FES-ET group received FES-ET for 1 hour a day on 15 to 20 consecutive workdays. Nine subjects in the low-intensity FES-ET group received 15 minutes of sensory electric stimulation 4 days a week and on the fifth day they received 1 hour of FES-ET.

MAIN OUTCOME MEASURES

Primary outcome measure included the Wolf Motor Function Test (WMFT). Secondary outcome measures included the Motor Activity Log (MAL), the upper-extremity portion of the Fugl-Meyer Assessment (FMA), and the combined kinematic score (CKS) derived from workstation measurements. The WMFT, MAL, and FMA were used to assess function in the absence of FES whereas CKS was used to evaluate function assisted by FES.

RESULTS

Improvements in the WMFT and CKS were significantly greater in the high-intensity group (post-treatment effect size, .95) than the low-intensity group (post-treatment effect size, 1.3). The differences in MAL and FMA were not statistically significant.

CONCLUSIONS

Subjects performing high-intensity FES-ET showed significantly greater improvements on the WMFT than those performing low-intensity FES-ET. However, this was not reflected in subjects' self-assessments (MAL) or in their FMA scores, so the clinical significance of the result is open to debate. The CKS data suggest that high-intensity FES-ET may be advantageous in neuroprosthetic applications.

Neuromodulation of lower limb monoparesis: functional electrical therapy of walking

After Cerebro-Vascular Accident (CVA), restoration of normal function, such as locomotion, depends on reorganization of existing central nervous system (CNS) circuitry. This capacity for reorganization, generally referred to as plasticity, is thought to underlie many instances of functional recovery after injury as well as learning and memory in the undamaged CNS. Both the reorganization of the supraspinal and spinal circuitry are highly important for the recovery of walking. The neural mechanisms responsible for learning and adapting processes are thought to involve changes both in the efficacy of synaptic function and the pattern of synaptic connections within neural circuits. In the uninjured CNS, these changes occur as a result of alterations in the amount of neural activity within circuits and are, therefore, termed activity-dependent. In this chapter, we will present several therapies of walking that provide effective input for the training of the existing CNS circuitry; thereby, contribute to long term recovery of sensory-motor functions. The focus of this chapter is Functional Electrical Therapy (FET) of walking, that is, the multi-channel electrical stimulation of sensory-motor systems that lead to more normal stance and swing of the paretic leg during the walking exercise.

Efficacy of electrical stimulation to increase muscle strength in people with neurological conditions: a systematic review

BACKGROUND AND PURPOSE

Weakness in partially paralysed muscles is a disabling impairment for people with neurological conditions. Strength training programmes are widely administered to address this impairment. There is a common belief that the effectiveness of strength training programmes can be enhanced by the addition of electrical stimulation. The purpose of this systematic review was to assess the efficacy of electrical stimulation for increasing voluntary strength in people with neurological conditions.

METHOD

Eligible randomized trials of electrical stimulation were identified by searches of computerized databases. The search yielded 11,267 abstracts, of which 60 were retrieved. Two assessors independently reviewed full text versions of these articles.

RESULTS

Eighteen studies satisfied the inclusion criteria. These studies involved participants with spina bifida (n = 1), cerebral palsy (n = 1), peripheral nerve lesion (n = 1), multiple sclerosis (n = 1), spinal cord injury (n = 3) and stroke (n = 11). The mean (SD) PEDro score for trial quality was 4.9 (1.0) out of 10. Meta-analyses of studies involving similar patients were not done because of insufficient data or lack of homogeneity. The results of all studies were analysed individually.

CONCLUSION

Several studies suggest a modest beneficial effect of electrical stimulation in patients with stroke. It is not clear whether patients with other types of neurological disabilities benefit from electrical stimulation in the same way.

Neuromuscular electrical stimulation in neurorehabilitation

This review provides a comprehensive overview of the clinical uses of neuromuscular electrical stimulation (NMES) for functional and therapeutic applications in subjects with spinal cord injury or stroke. Functional applications refer to the use of NMES to activate paralyzed muscles in precise sequence and magnitude to directly accomplish functional tasks. In therapeutic applications, NMES may lead to a specific effect that enhances function, but does not directly provide function. The specific neuroprosthetic or "functional" applications reviewed in this article include upper- and lower-limb motor movement for self-care tasks and mobility, respectively, bladder function, and respiratory control. Specific therapeutic applications include motor relearning, reduction of hemiplegic shoulder pain, muscle strengthening, prevention of muscle atrophy, prophylaxis of deep venous thrombosis, improvement of tissue oxygenation and peripheral hemodynamic functioning, and cardiopulmonary conditioning. Perspectives on future developments and clinical applications of NMES are presented.

Mechanisms of recovery in stroke patients with hemiparesis or aphasia: new insights, old questions and the meaning of therapies

PURPOSE OF REVIEW

The mechanisms responsible for recovery after stroke in patients with hemiparesis or aphasia are under intense study, since knowledge of these mechanisms is a prerequisite for choosing which therapy a patient receives and when to apply it.

RECENT FINDINGS

Most of the recent insights are obtained with longitudinal studies using functional imaging and direct cortical stimulation during the process of recovery. They reveal that reorganization is a highly dynamic process, involving the establishment of new communications in the remaining system and showing similarities to learning processes in healthy individuals. Lesion localization is a major determinant for recovery and the pattern of reorganization. Neurobiological hypotheses lead to clinical studies, which in turn are now used to confirm or reject these hypotheses.

SUMMARY

Although our understanding of the mechanisms responsible for recovery is increasing, the application of this knowledge in daily praxis is still limited. A better understanding of the underlying mechanisms, however, can lead to appropriate therapies for individual patients.

Automatic determination of synergies by radial basis function artificial neural networks for the control of a neural prosthesis

This paper describes an automatic method for synthesizing the control for a neural prosthesis (NP) that could augment elbow flexion/extension and forearm pronation/supination in persons with hemiplegia. The basis for the control was a synergistic model of reaching and grasping that uses temporal and spatial synergies between the arm and body segments. The synergies were determined from the movement data measured in nondisabled persons during the performance of functional tasks. The work space was divided into six zones: distance (two attributes) and laterality (three attributes). Radial basis function artificial neural networks (RBF ANN) were used to determine synergies. Sets of RBF ANN characterized with good generalization were selected as control laws for elbow flexion/extension and forearm pronation/supination. The validation was performed for three categories: inter-subject, distance, and laterality generalization. For all of the defined spatial synergies, the correlation was high for inter-subject and distance, yet low for the laterality scenario. This suggests the necessity for implementing different maps for different directions, but the same maps for different distances. The natural movements of the upper arm then drive the lower arm (elbow flexion/extension and forearm pronation/supination) in a way that is very well suited for the administration of functional electrical therapy (FET) in persons with hemiplegia soon after the onset of impairment.

Reanimating limbs after injury or disease

Many diseases and injuries lead to loss of motor function. Can we reanimate paralyzed limbs to produce effective, graceful movements? Recent insights into the function of the motor system and greatly improved computing capabilities have made this a realistic goal, even in the absence of regeneration of motor pathways. Some approaches involve stimulating muscles, nerves or the spinal cord below the level of a lesion. Others involve recording a subject's intention from the cortex, and using this intention to control computers, robots or systems for stimulating the limbs. Here, we critically analyze the possibilities and limitations of various approaches for restoring motor function based on recent human trials and underlying neuroscience research.