Effect of
EMG-triggered Electrical Stimulation in Patients with Chronic Hemiplegia
Young-Hee Lee*, Yang Tark Lee, Kyung Hee Park, Sung
Hoon Kim, Sang Min Jang, Tae Ho Kim, Myoung Yae Lee
Introduction
Following a cerebrovascular accident
(CVA) and traumatic brain injury (TBI), any spontaneous recovery of the upper
limb motor function is generally limited to the first six months. During this
period, the motor recovery has been reported to be enhanced, beyond that
attained by conventional therapy, rehabilitation techniques, including neurofacilitatory physical therapy, EMG bio-feedback and
positional feedback, with electrical stimulation. However, there is a consensus
that the current rehabilitation techniques are less effective in improving
upper limb motor function in a chronic brain lesion (>6 months). As the
months after a stroke accumulate into years, individuals typically accept the
chronic motor problems, and attempt to compensate for their losses. Wolf et al[1] argued that individuals with upper-extremity motor
problems display behaviors that indicate learned nonuse. An affected arm is not used for any voluntary
movements, whereas an unaffected arm will attempt to execute all of the motor
actions required for daily living. So, control of upper extremity functions,
such as wrist and finger extensors, are a challenging aspect in upper extremity
recovery. In this study, attempts were made to identify
the effect and mechanism of EMG-triggered electrical neuromuscular stimulation
for the recovery of hemiplegic arm function.
Methods
Eight subjects, 6
≥ 1 year after stroke, and 2 with TBI, with chronic upper-extremity
impairments, were recruited. All the subjects were male, with a mean age of 40
years (SD=5.8) and an average time after brain lesion of 26 months (SD=19). Six
of the subjects had left hemisphere brain lesions, whereas the other two had
right hemisphere brain lesions.
Both before and after
treatment, six clinical tests were administered to evaluate the effects of the
treatment. The Box and Block timed manipulation test, Fugl-Mayer
(FM) score and functional independence measure (FIM), were used to evaluate the
functional recovery in hand and wrist/finger movements after the brain lesion.
A modified Ashworth scale (MAS) was used to evaluate the spasticity. The motor
free visual perception test (MVPT) and Loewenstein
occupational therapy cognitive assessment (LOTCA) were used to evaluate the
perceptual and cognitive function. A
quantitative EMG, from the extensor digitorum communis (EDC) muscle, and an
excursion of the 2nd metacarpophalangeal joint, using the MP150 ® system (BIOPAC systems Inc.), were
administered to evaluate the kinesiologic function.
Using an Automove AM 800 ® (danmeter,
In two subjects, one showing, and the other not showing, voluntary finger movement prior to treatment, functional MRI and magnetic evoked potential (MEP) brain mapping were used to evaluate the brain plasticity.
Results
The subjects treated with EMG-triggered electrical stimulation
showed significant gain in the amplitude of the quantitative EMG and excursion
sums, during maximal exertion, comparing to those prior to treatment (p<0.05)(Figure
1). There was also a decrease of spasticity after treatment, but the
functional, perceptual and cognitive measurements were not changed
significantly (p>0.05). The MEP mapping and functional MRI showed increases
in the motor output area sizes and activated motor cortices in both
hemispheres, after four weeks of EMG-triggered electrical stimulation, in a subject
that showed voluntary finger movement prior to treatment (Figure 2).
Figure 1.
Quantitative EMG from EDC (RMS) and excursion
sums of the
2nd MCP joint during voluntary hand movement.
* p<0.05
AFFECTED UNAFFECTED
Figure 2. MEP Mapping showed an increase in the motor output area sizes in both hemispheres after 4 weeks of EMG triggered electrical stimulation
Discussion
Given
that wrist and finger extension control is one of the most difficult motions to
regain after a brain lesion, and a key precursor for prehensile activity, the
loss of this capability is a primary disabler of hand function. Frequently, the
prehensile motions, and wrist/finger extension movements, serve as markers for
therapeutic intervention. In a related study on EMG-triggered neuromuscular
electrical stimulation, Chae et al[2] provided
acute stroke patients with 15 days (1 hour per day) of treatment. The wrist and
finger extension neuromuscular stimulation group demonstrated greater gains in
their FM scores, following treatment, than the control group. The motor
recovery found in their acute stroke population was dramatic compared with our
study group of stroke survivors, with well-defined unilateral motor
dysfunctions that had accumulated over many years. The stage of motor recovery
is an important distinction between these study; Chae
et al[2] used acute
stroke patients (<1 year after stroke) in their
study, whereas
the present study tested patients with chronic brain lesions (>1 year after
brain lesion).Admittedly, in the present study, there were significant gains in the amplitude of quantitative EMG and
the excursion sums during maximal exertion comparing to those prior to
treatment. There was also a significant decrease of spasticity after treatment.
However, the functional, perceptual and cognitive measurements were not
significantly changed.
Nevertheless, a theoretical question about the mechanism still
remains: What mechanism does the EMG-triggered neuromuscular stimulation
activate that could explain the improved spasticity and kinesiologic
values? However, the restricted treatment times involved, and the short
training programs, suggest that a muscle training explanation has limitations.
As reviewed by
Another viable explanation involves the
sensorimotor integration theory. Xerri et al[4] reported that monkeys generated new cortical
representations after microlesions had destroyed
specific regions of the somatosensory cortex. The re-emergence of fingertip
representations, once the monkeys reacquired previously learned finger
manipulation movements, was interpreted as substantial evidence supporting the
integration of the sensorimotor signals. This interpretation is consistent with
brain plasticity studies in humans during motor skill learning. Researchers
have argued that cortical plasticity, following a stroke, goes through similar
alterations to those that have been observed during motor skill learning in
normal uninjured brain. In our study, there were increases in the motor
output area sizes and activated motor cortices in both hemispheres, after four
weeks of EMG-triggered electrical stimulation, in a subject that had shown
voluntary finger movement in the MEP mapping and functional MRI prior to
treatment.
In summary, the use of EMG-triggered neuromuscular electrical
stimulation, to the EDC muscle, in individuals with chronic brain lesions, due
to a stroke or TBI, resulted in significant improvements in the spasticity and kinesiologic values. There was also
functional radiological and physiologic evidence of central nervous system
reorganization in a case that showed a marked improvement in finger motion,
which might explain the mechanism of effect as being one of brain plasticity. These findings suggest that
neuromuscular-triggered electrical stimulation is a beneficial adjunct to the
rehabilitation of hand function following a chronic brain lesion.
References
[1] Wolf, S.L., Lecraw,
D.E., Barton,
[2] Chae, J., Bethoux, F., Bohine, T., Dobos, L., Davis, T., Friedl, A.,
Neuromuscular stimulation for upper extremity motor and functional recovery in
acute hemiplegia. Stroke, 1998. 29: p. 975-979.
[3]
[4] Ghez, C.,
Gordon, J., Ghilardi, M., Sainburg,
R., Contributions of vision and proprioception to accuracy in limb movements.
In: Gazzaniga M.S., ed. The cognitive Neurosciences.