Interaction of electrical stimulation and voluntary hand movement in SII and the cerebellum during simulated therapeutic functional electrical stimulation in healthy adults.

The therapeutic application of functional electrical stimulation (FES) has shown promising clinical results in the rehabilitation of post-stroke hemiplegia. It appears that the effect is optimal when the patterned electrical stimulation is used in close synchrony with voluntary movement, although the neural mechanisms that underlie the clinical successes reported with therapeutic FES are unknown. One possibility is that therapeutic FES takes advantage of the sensory consequences of an internal model. Here, we investigate fMRI cortical activity when FES is combined with voluntary effort (FESVOL) and we compare this activity to that produced when FES and voluntary activity (VOL) are performed alone. FESVOL revealed greater cerebellar activity compared with FES alone and reduced activity bilaterally in secondary somatosensory areas (SII) compared with VOL alone. Reduced activity was also observed for FESVOL compared with FES alone in the angular gyrus, middle frontal gyrus and inferior frontal gyrus. These findings indicate that during the VOL condition the cerebellum predicts the sensory consequences of the movement and this reduces the subsequent activation in SII. The decreased SII activity may reflect a better match between the internal model and the actual sensory feedback. The greater cerebellar activity coupled with reduced angular gyrus activity in FESVOL compared with FES suggests that the cortex may interpret sensory information during the FES condition as an error-like signal due to the lack of a voluntary component in the movement.

Patients' perceptions of the benefits and problems of using the ActiGait implanted drop-foot stimulator.

OBJECTIVE: To evaluate patients' perceptions of the benefits and problems associated with using the ActiGait implanted drop-foot stimulator. METHOD: Thirteen participants who had suffered a stroke at least 6 months prior to recruitment, had a drop-foot that affected walking and had taken part in a trial in which an ActiGait drop-foot stimulator had been implanted, completed a postal questionnaire. RESULTS: Users agreed that the ActiGait had a positive effect on walking; they used it regularly and had little difficulty with putting it on and taking it off. Reliability was a greater problem at 90 days than at the final assessment. Ten of the 13 responders either agreed or strongly agreed with the statement that the ActiGait improved their quality of life at 90 days and 9 out of 12 at the final assessment: 11 of the 12 respondents would recommend the ActiGait to others. DISCUSSION AND CONCLUSION: From the users' perspective the ActiGait improved walking, it was reported to be used regularly and it appeared to be easier to use than a surface system. Users were equivocal about the reliability of the system at 90 days, but at the final assessment reliability had improved.

Phase II trial to evaluate the ActiGait implanted drop-foot stimulator in established hemiplegia.

OBJECTIVE: To evaluate a selective implantable drop foot stimulator (ActiGait) in terms of effect on walking and safety. DESIGN: A phase II trial in which a consecutive sample of participants acted as their own controls. SUBJECTS: People who had suffered a stroke at least 6 months prior to recruitment and had a drop-foot that affected walking were recruited from 3 rehabilitation centres in Denmark. METHODS: Stimulators were implanted into all participants. Outcome measures were range of ankle dorsiflexion with stimulation and maximum walking speed and distance walked in 4 minutes. Measurements were applied before implantation, at 90 days and at a long-term follow-up assessment. Changes over time and with and without stimulation are reported. Safety was evaluated by nerve conduction velocity and adverse events. RESULTS: Fifteen participants were implanted and 13 completed the trial. Long-term improvements were detected in walking speed and distance walked in 4 minutes when stimulated, and the orthotic effect of stimulation showed statistically significant improvement. The device did not compromise nerve conduction velocity and no serious device-related adverse events were reported. Technical problems were resolved by the long-term follow-up assessment at which further improvement in walking was observed. CONCLUSION: This trial has evaluated the safety and performance of the device, which was well accepted by patients and did not compromise safety.

Event driven electrical stimulation of the dorsal penile/clitoral nerve for management of neurogenic detrusor overactivity in multiple sclerosis.

AIMS: The aim of this study was to evaluate the effect of automatic event driven electrical stimulation on the dorsal penile/clitoral nerve for management of neurogenic detrusor overactivity in patients suffering from Multiple Sclerosis. METHODS: A total of 10 patients participated in the study. Detrusor pressure was recorded during physiological filling of the bladder and electrical stimulation was applied with surface electrodes whenever the detrusor pressure exceeded 10 cm H(2)O. RESULTS: In seven of the eight patients, where neurogenic detrusor overactivity was observed an average of 12 detrusor contractions could be inhibited by stimulation. In one patient, however, stimulation failed to inhibit the detrusor contractions. The average increase in bladder volume from first suppressed detrusor contraction until leakage was 94% (range: 22-366%). On average, the time from first suppressed contraction until leakage was 15 min and 50 sec (range: 4 min 58 sec-32 min 5 sec) with an average physiological filling rate of 8 ml/min. Urgency was effectively suppressed at the onset of stimulation. CONCLUSIONS: The results indicate that involuntary detrusor contractions in patients with multiple sclerosis can effectively be inhibited with event driven stimulation, hereby improving bladder capacity and reducing the number of incontinence episodes. However, the used method for detecting detrusor contractions is not suitable in a chronic setting and alternative techniques needs to be investigated if stimulation should be applied automatically.

Colon emptying induced by sequential electrical stimulation in rats.

Electrical stimulation could be used to induce colon emptying. The present experiments were performed to establish a stimulation pattern to optimize the stimulation parameters and to test neural involvement in propulsion induced by electrical stimulation. Colon segments were sequentially stimulated using rectangular pulses. The resulting propulsive activity displaced intraluminal content in consecutive propulsion steps. The propulsion steps differed in displacement latency, distance, and velocity along the stimulated colon. Increasing the pulse duration or amplitude resulted in a decrease of the latency. Increasing the stimulation amplitude doubled the displacement distance. The frequencies tested in the present study did not affect propulsion. Inhibition of cholinergic and nitrergic pathways inhibited propulsion. Electrical stimulation can induce colonic propulsion. Motor differences are present along the descending colon. The most suitable combination of pulse parameters regarding colon stimulation is 0.3 ms, 5 mA, 10 Hz. Neural circuits are involved in propulsion when using these values.

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

There are indications that both intensive exercise and electrical stimulation have a beneficial effect on arm function in post-stroke hemiplegic patients. We recommend the use of Functional Electrical Therapy (FET), which combines electrical stimulation of the paretic arm and intensive voluntary movement of the arm to exercise daily functions. FET was applied 30 min daily for 3 weeks. Forty-one acute hemiplegics volunteered in the 18-months single blinded cross-over study (CoS). Nineteen patients (Group A) participated in FET during their acute hemiplegia, and 22 patients (Group B) participated in FET during their chronic phase of hemiplegia. Group B patients were controls during FET in acute hemiplegia, and Group A patients were controls during the FET in chronic hemiplegia. Thirty-two patients completed the study. The outcomes of the Upper Extremity Function Test (UEFT) were used to assess the ability of patients to functionally use objects, as were the Drawing Test (DT) (used to assess the coordination of the arm), the Modified Ashworth Scale, the range of movement, and the questionnaire estimating the patients' satisfaction with the usage of the paretic arm. Patients who participated in the FET during the acute phase of hemiplegia (Group A) reached functionality of the paretic arm, on average, in less than 6 weeks, and maintained this near-normal use of the arm and hand throughout the follow-up. The gains in all outcome scores were significantly larger in Group A after FET and at all follow-ups compared with the scores before the treatment. The gains in patients who participated in the FET in the chronic phase of hemiplegia (Group B) were measurable, yet not significant. The speed of recovery was larger during the period of the FET compared with the follow-up period. The gains in Group A were significantly larger compared with the gains in Group B. The FET greatly promotes the recovery of the paretic arm if applied during the acute phase of post-stroke hemiplegia.

Evaluating robustness of gait event detection based on machine learning and natural sensors.

A real-time system for deriving timing control for functional electrical stimulation for foot-drop correction, using peripheral nerve activity as a sensor input, was tested for reliability to investigate the potential for clinical use. The system, which was previously reported on, was tested on a hemiplegic subject instrumented with a recording cuff electrode on the Sural nerve, and a stimulation cuff electrode on the Peroneal cuff. Implanted devices enabled recording and stimulation through telelinks. An input domain was derived from the recorded electroneurogram and fed to a detection algorithm based on an adaptive logic network for controlling the stimulation timing. The reliability was tested by letting the subject wear different foot wear and walk on different surfaces than when the training data was recorded. The detection system was also evaluated several months after training. The detection system proved able to successfully detect when walking with different footwear on varying surfaces up to 374 days after training, and thereby showed great potential for being clinically useful.

Biopotentials as command and feedback signals in functional electrical stimulation systems.

Today Functional Electrical Stimulation (FES) is available as a clinical tool in muscle activation used for picking up objects, for standing and walking, for controlling bladder emptying, and for breathing. Despite substantial progress in development and new knowledge, many challenges remain to be resolved to provide a more efficient functionality of FES systems. The most important task of these challenges is to improve control of the activated muscles through open loop or feedback systems. Command and feedback signals can be extracted from biopotentials recorded from muscles (Electromyogram, EMG), nerves (Electroneurogram, ENG), and the brain (Electroencephalogram (EEG) or individual cells). This paper reviews work in which EMG, ENG, and EEG signals in humans have been used as command and feedback signals in systems using electrical stimulation of motor nerves to restore movements after an injury to the Central Nervous System (CNS). It is concluded that the technology is ready to push for more substantial clinical FES investigations in applying muscle and nerve signals. Brain-computer interface systems hold great prospects, but require further development of faster and clinically more acceptable technologies.

Restitution of reaching and grasping promoted by functional electrical therapy.

Functional electrical therapy (FET) is a new term describing a combination of functional electrical stimulation that generates life-like movement and intensive exercise in humans with central nervous system lesions. We hypothesized that FET can promote a significant recovery of functioning if applied in subacute stroke subjects. The study included 16 stroke subjects divided into a low functioning group (LFG) and a high functioning group (HFG) based on their ability to control wrist and fingers and randomly associated into FET and controls. The FET consisted of 30 min daily sessions during 3 weeks. The exercise comprised functional use of daily necessary activities (e.g., writing, using a telephone receiver, and drinking from a can). The outcome presented in this article is the upper-extremity function test performed before and after the therapy. The change in performance of the HFG group was significant. The number of successful repetitive movements in 2 min was doubled and 1.6 times increased for controls, and the time to perform the movement was decreased by 71% percent and by 36% in controls. In the LFG FET group, the difference in performance was the following. First, the number of tasks was increased from 0 to 6 (total of 11 tasks). Second, the averaged number of successful repetitive movements was increased from 0 to 3. The functional improvement in the FET LFG is probably not sufficient to make the more affected arm/hand effective for daily necessities; thus, the FET effects could deteriorate over a longer time. The subjects from the control LFG made only a marginal improvement. The follow-up for each subject will continue for 12 months after the beginning of the treatment.

A review of portable FES-based neural orthoses for the correction of drop foot.

This paper reviews the technological developments in neural orthoses for the correction of upper motor neurone drop foot since 1961, when the technique was first proposed by Liberson and his co-workers. Drop foot stimulator (DFS) developments are reviewed starting with hard-wired single-channel and multichannel surface functional electrical stimulation (FES) systems, followed by implanted drop foot stimulators, and then continuing with microprocessor-based surface and implanted drop foot stimulators. The review examines the role of artificial and "natural" sensors as replacements for the foot-switch as the primary control sensor in drop foot stimulators. DFS systems incorporating real-time control of FES and completely implanted DFS systems finish the review.

Neurorehabilitation of upper extremities in humans with sensory-motor impairment.

Today most clinical investigators agree that the common denominator for successful therapy in subjects after central nervous system (CNS) lesions is to induce concentrated, repetitive practice of the more affected limb as soon as possible after the onset of impairment. This paper reviews representative methods of neurorehabilitation such as constraining the less affected arm and using a robot to facilitate movement of the affected arm, and focuses on functional electrotherapy promoting the movement recovery. The functional electrical therapy (FET) encompasses three elements: 1) control of movements that are compromised because of the impairment, 2) enhanced exercise of paralyzed extremities, and 3) augmented activity of afferent neural pathway. Liberson et al. (1) first reported an important result of the FET; they applied a peroneal stimulator to enhance functionally essential ankle dorsiflexion during the swing phase of walking. Merletti et al. (2) described a similar electrotherapeutic effect for upper extremities; they applied a two-channel electronic stimulator and surface electrodes to augment elbow extension and finger extension during different reach and grasp activities. Both electrotherapies resulted in immediate and carry-over effects caused by systematic application of FET. In studies with subjects after a spinal cord lesion at the cervical level (chronic tetraplegia) (3-5) or stroke (6), it was shown that FET improves grasping and reaching by using the following outcome measures: the Upper Extremity Function Test (UEFT), coordination between elbow and shoulder movement, and the Functional Independence Measure (FIM). Externally applied electrical stimuli provided a strong central sensory input which could be responsible for the changes in the organization of impaired sensory-motor mechanisms. FET resulted in stronger muscles that were stimulated directly, as well as exercising other muscles. The ability to move paralyzed extremities also provided awareness (proprioception and visual feedback) of enhanced functional ability as being very beneficial for the recovery. FET contributed to the increased range of movement in the affected joints, increased speed of joint rotations, reduced spasticity, and improved functioning measured by the UEFT, the FIM and the Quadriplegia Index of Function (QIF).