Clinical Studies

Electromyogram-Triggered Neuromuscular Stimulation for Improving the Arm Function of Acute stroke Survivors: A Randomized Pilot Study
-Gerard Francisco, MD, Jon Chae, MD, ME, Harmeen Chawla, MD, Steven Kirshblum, MD, Richard Zorowitz, MD, Gerald Lewis, MS, PT, Shcone Pang, MS, OTR. Arch. Phys. Med. Rehabil 1998; 79:570-575

Summary:

Objective: To assess the efficacy of electromyogram (EMG)-triggered neuromuscular stimulation (EMG-stim) in enhancing upper extremity motor and functional recovery of acute stroke survivors.

Design: A pilot randomized, single-blinded clinical trial.

Setting: Freestanding inpatient rehabilitation facility.

Patients: Nine subjects who were within 6 weeks of their first unifocal. nonhemorrhagic stroke were randomly assigned to either the EMG-stim (n=4) or control (n=5) group. All subjects had a detectable EMG signal (>5µV) from the surface of the paretic extensor carpi radialis and voluntary wrist of the paretic extensor carpi radialis and voluntary wrist extension in synergy or in isolation with muscle grade of <3/5.

Intervention: All subjects received two 30-minute sessions per say of wrist strengthening exercises with EMG-stim (experimental) or without (control) for the duration of their rehabilitation stay.

Main Outcome Measures: Upper extremity Fugl-Meyer motor assessment and the feeding, grooming, and upper body dressing items of the Functional Independence Measure (FIM) were assessed at study entry and at discharge.

Results: Subjects treated with EMG-stim exhibited significantly greater gains in Fugl-Meyer (27.0 vs 10.4; p=.05), and FIM (6.0 vs 3.4: p=.02) scores compared with controls.

Conclusion: Data suggest that EMG-stim enhances the arm function of acute stroke survivors.




Electromyographically triggered electric muscle stimulation for chronic hemiplegia.
-R.W. Fields, Arch. Phys. Med. Rehabil 1987 Jul;68(7):407-14.

Electromyographically triggered electric muscle stimulation (EMS) was evaluated in combination with conventional treatment in 69 consecutive postcerebrovascular accident outpatients whose onset of hemiplegia was four months to 14 years earlier. Six subjects initially exhibited no residual volitional activity in targeted muscles, and all patients had undergone conventional therapy with little or no functional recovery. Prescribed treatment (patient compliance was frequently substandard) involved several months of four to five sessions per week, focusing on wrist extension and/or ankle dorsiflexion initially, and often other movements later. During 30 to 300 movement attempts per session, EMG's that exceeded a preset threshold triggered immediate stimulation to force movement completion. Over sessions, patients commonly realized substantially improved increases in voluntary EMG capabilities generally proportionate to the frequency of treatment sessions. Parallel improvements were also found for subjectively scaled functional measures of range-of-motion and ambulation. Motivation was important to success, but side and nature of stroke, age, and poststroke interval were not. Progress often far exceeded that of previous conventional therapy. Regarding mechanisms, impaired proprioceptive feedback is considered central to stroke-disrupted sensorimotor control. EMG-triggered EMS is intended to improve brain relearning by reinstating proprioceptive feedback time-locked to each attempted movement. Clinical results were consistent with this theory.




Mental Practice of Motor Skills used in poststroke Rehabilitation has Own Effects on Central Nervous Activation.
-T. Weiss, Ellen Hansen, R. Rost, L. Beyer, F. Merten, Christa Nichelmann, and C. Zippel. Intern J. Neuroscience, 1994, Vol. 78, pp 1 57-166.

Summary:

In the last years it has been shown that the use of the EMG triggered electrical myostimulation (ETEM) brings good results in poststroke rehabilitation. It has been hypothesized that the relearning effects obtained by means of ETEM are due to the reinstatement of proprioceptive feedback. However, the technique is most powerful if imagination of motor acts (the so called mental practice) is used as an initial part of ETEM. Since mental practice in healthy people leads to central nervous activation processes as well as to an improvement of motor skills, we investigated the effects of mental practice alone on central nervous activity by means of EEG in stroke patients.

Twelve left-sided hemiplegic patients who underwent a specific poststroke rehabilitation treatment were requested to perform a simple arm movement sequence. In the following mental practice period the patients were requested to imagine the same sequence without any real movement. EEG background activity was recorded during baseline and imagination periods. After the calculation of z-transformed power values within the alpha and beta-1 band, differences between rest and imagination periods were evaluated for significance.

Stroke patients showed significant decreases of alpha as well as beta-1 power during mental practice in comparison to the rest period. These changes are similar to those obtained in healthy subjects. Central alpha power diminished only during imagination of the contralateral arm. This phenomenon as well as the decrease of beta-1 power in central derivation were also obtained during real motor performance and might indicate an activation of the sensorimotor cortex. In accordance with the hypothesis of internal feedback mechanisms, this activation is a necessary prerequisite for motor learning during mental practice. We conclude that mental practice of motor skills might have own effects in poststroke rehabilitation.




Patterns of Central Motor Reorganization in Hemiplegic Cerebral Palsy.
-L.J. Carr, L.M. Harrison, A.L. Evans and J.A Stephens. 1993, Oxford University Press, Brain, 116, 1223, 1247.

Summary:

Central motor reorganization was studied in 33 subjects with hemiplegic cerebral palsy. Corticospinal projections were investigated using focal magnetic stimulation of the motor cortex. Reflex pathways were examined with digital nerve stimulation. Cross-correlation analysis of multi-unit EMG was used to detect activity in branched common stem last order presynaptic inputs to motor neuron pools. The neurophysiological findings were related to the clinical outcome.

In 21 of the subjects studied (64%), there was evidence for reorganization of central motor pathways. The clinical and neurophysiological findings revealed two different forms of reorganization. In both forms focal magnetic stimulation demonstrated novel ipsilateral motor pathways from the undamaged motor cortex to the hemiplegic hand. Ipsilateral projections were not demonstrated from the damaged motor cortex. Eleven subjects had intense mirror movements. In these subjects cross-correlation analysis and reflex testing suggested that corticospinal axons had branched abnormally and projected bilaterally to homologous motor neuron pools on both sides of the spinal cord. The remaining 10 subjects did not have intense mirror movements and in these subjects there was no evidence for last order branching of corticospinal axons.

It was found that good function of the hemiplegic hand was associated with the presence of EMG responses in that hand following magnetic stimulation of the contralateral motor cortex. When EMG responses were absent, hand function was poor unless the subject had intense mirror movements.




Treatment of Hemiplegia by Means of Imagination-dependent EMG-triggered muscle stimulation.
-J. Danz, S. Gutierrez-Lopez. Physikalische Medizin, Heft 1, 4. Jahrgang, Feb. 1994.

Summary:

The imagination of a movement elevates the electrical activity of paralyzed muscles. By means of a device Automove, this changed activity is used to generate low-frequency pulses which in turn are applied to induce a contraction of the spastic antagonist muscles. In this way the imagination-dependent muscle stimulation - triggered by EMG - circumvents the spastic movement patterns. The patient becomes able to regain forgotten movements by means of the method described.

During the acute phase after a stroke it was applicable in only one third of our patients (n=40). Another group consisted of out-patients (n=20). In 18 of these a functional improvement of the paralyzed arm was attained after treatment for six months.