Therapeutic Effects of Functional Electrical Stimulation
Thomas Sinkjær1, Dejan
B. Popović1, Mirjana B.Popović1,2
1Center for Sensory
Motor Interaction, Aalborg
University , Denmark University
of Belgrade , Yugoslavia
Introduction
Plasticity of the
CNS has been recognized as a part of the structural and physiological substrate
for recovery of function after brain injury [1]. Cortico-motor reorganization
could occur as a response to: altered inputs to the cortex sensory, as an
adaptation to injury of the central or peripheral nervous system or as a
consequence of the motor task performed, and may be either short term or more
long lasting. Dynamic remodeling processes occurring in the sensorimotor cortex
of humans has been demonstrated after peripheral deafferentation [2].
Modification of the sensory representation has been shown for the fingering
digits of violin players. However not for digits of the bow hand, indicating
thus a long-lasting change in the sensory cortex has occurred in response to
the repetitive performance of complex and highly skilled motor task [3].
Changes in the fMRI signal were found with practice of four-finger tapping
exercise over a period of days and weeks to last for 4-6 weeks, whereas expansion
of Transcranial Magnetic Stimulation maps persisted until the performance of
the task reached plateau [4]. The question that we are answering considering
the above facts is what we need to change in the rehabilitation protocols to
improve outcome of functional movements after stroke by promoting
neuroplasticity?
The reviews of the
neurorehabilitation methods [5, 6] suggest that almost all techniques that
involve increased exercise or electrical stimulation promote recovery. In order
to evaluate the differences between the effects of conventional vs.
enhanced therapy we introduced Functional Electrical Therapy (FET) [7]. FET is
a treatment that combines electrical therapy and intensive exercise for
hemiplegic patients.
Methods
Subjects. The following two evaluated: 1) acute
hemiplegic subjects (more than two weeks and less than three months following
first stroke ever), 2) chronic hemiplegic subjects (more than one-year post
stroke). 32 subjects were randomly
included in the study (mean age & SD, 61.5±7.5). The acute subjects were accepted in the
study at an average 6±2 weeks after the onset of stroke, while the
chronic subjects after 65±9 weeks.
The inclusion criteria were: 1) stroke of ischaemic or hemorrhagic
origin, confirmed by MRI or CT scan; 2) age over 18; 3) able to give informed
consent; and 4) cognitive status sufficient for learning how to use FET. The exclusion criteria were: 1) dependent on
care, prior to stroke, for activities of daily living, 2) severe medical
condition in any arm that precludes participation in the study, 3) previous
injury or disease or contracture affecting hemiplegic or non-hemiplegic arm or
hand, and 4) pre-existent neurological disease or injury. All subjects had some
extension of their wrist, fingers and thumb against gravity at the onset of
hemiplegia (3 to 6 weeks after stroke).
All subjects were able to extend the wrist and fingers more than 20
degrees against gravity, and they could extend all fingers for more than 10
degrees against gravity. The average spasticity of the subjects (modified
Ashworth scale) was 2-3). Study hemiplegic subjects signed informed consent
approved by the local ethics committee before entering in the study.
Treatment. All subjects received the conventional
physical therapy and FET based on Bobaths methods [8]. Acute subjects were
randomly assigned to control or FET group. FET is a procedure of voluntary
activation of all preserved sensory-motor mechanisms of the paretic arm in
synchrony with a neural prosthesis that apples four channels and surface
electrodes in order to assist opening, closing, holding, and releasing of
objects in a fashion similar to normal grasping. This treatment was applied in
FET and chronic hemiplegic subjects for three consecutive weeks on a daily
basis. The FET sessions lasted for 30 minutes. The assignment during the
session was that hemiplegic subjects functionally use various daily necessities
(e.g., can, telephone receiver, comb, toothbrush, VCR tape). A functional use of an object comprised the
following phases: reach, grasp, manipulate the object, bring object back to the
original post, and release it. Details on the procedure are explained elsewhere
[7]. Hemiplegic subjects from the control group were required to daily exercise
for 30 minutes trying to accomplish the same tasks as the FET group yet without
a neural prosthesis.
Outcome measures: 1) Upper Extremity Functioning Test (UEFT),
2) Drawing test and 3) structured questionnaire about the real use and
satisfaction [7]. The subjects were
assessed at the point of entry to the trial, after the treatment (3 weeks), and
at 6, 13, 26 weeks after the beginning of the study. The statistical analysis
used repeated ANOVA to compare the gains in each of the groups and differences
between the groups.
Results
Figure 1 shows the
results of the upper extremity test for chronic, acute control and FET groups.
The linear regression trend lines are intentionally broken into two parts to
point to the fact that the functional gains are changing through the evaluation
period. The gains are much bigger at the beginning, and they are very
dissimilar for different groups. The gains are the biggest for the acute FET.
There is a statistically significant gain in acute FET subjects (p<0.01,
F=8.5). There was a statistically significant difference between the gains in
FET acute subjects compared to two other groups (p<0.01, F=21.2).
Figure 1. The Upper Extremity Function Test is a number
of successful repetitions of functional tasks during two-minute intervals. 11
tasks were tested. The bars are average ± S.D. for the whole group over all 11 tasks.
Figure 2. The drawing test shows the ability to draw a
square with the side of 20cm on the digitizing board. The score expressed in
percent was calculated by normalizing the area surrounded with the drawing to
the nominal area of the square (400 cm2).
The results were obtained from three
successive drawing in clock and counter clock directions. The bars are average ± S.D. for the whole group.
Figure 2 shows the
results of the drawing test. Drawing test shows the ability to coordinate elbow
and shoulder joints while making straight-line movements in four orthogonal
directions in the horizontal plane. The gains in the drawing test are obvious,
and very much alike the gains in the UEFT the linear regression trend lines are
broken to demonstrate the variability of slopes. The gains are maximal during
the treatment in the acute hemiplegic subjects. There is a statistically
significant gain in acute FET subjects (p<0.01, F=11.3). There was a
statistically significant difference between the gains in FET acute subjects
compared to two other groups (p<0.01, F=9.6).
The gains in chronic
subjects in both UEFT and drawing test are small, yet noticeable. Note that the
chronic hemiplegic subjects started the study from the level being much bigger
compared with the acute subjects. This was expected because these hemiplegic
subjects reached plateau at about six months and their gains during this first
year were due to the conventional treatment and natural recovery. The acute
subjects who participated in the FET program achieved much better scores and
they overcome the abilities of chronic subjects at about 6 weeks.
The gains in acute
subjects cannot be attributed only to stronger muscles since the changes were
dramatic in the control of non-stimulated motor systems, i.e., elbow and
shoulder. The most likely answer to the question why this techniques works is
that it contributes to the neuroplasticity in acute state of hemiplegia.
Conclusion
The conclusions from
this presentation is that functional electrical therapy when applied in acute
hemiplegic subjects with some residual wrist and fingers extension leads to
faster and greater gains in functional measures that are important for normal
life.
References
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Acknowledgments
The author wishes to
acknowledge the Danish National Research Foundation, Copenhagen, Denmark and
Ministry of Health and Technology of Serbia, Belgrade.