Introduction
A research project investigating a method for restoring lost
movements in people with a
upper motor neuron lesion (e.g Ictus - stroke, spinal cord injury, etc )
The basic
idea is to 'boost' impaired movements by measuring the intention and
activate
necessary muscles in a manner that is close to normal motions.
Muscle
contractions are generating a weak signal (myoelectric activity), which
can be
measured by sensitive electronic circuits. From the myoelectric signal
(MeS),
the amount of movement that the subject is attempting can be estimated.
Even
paretic muscles, with only twitches of contraction, may be used for
estimating
the users intent to move.
On the
contrary, if the circumstances are right, muscles can also be made
contract by
stimulating them with electricity. When the muscle-contraction is
functional,
we call it Functional Electrical Stimulation - FES.
So the
concept is actually simple: The MeS represents intent to move - the FES
induces
the movement. In combination, we can then let the mind control the lost
movements - again. Ideally, the MeS controlled FES should acting like a
servo
control or power
steering
in a car - a small steering effort is augmented by actuators to provide the power
needed for turning heavy
wheels, so the driver only needs to provide modest effort. In our case,
the
driver is a part of the muscle still under volitional control and the
actuator
is the FES of the paralyzed part of the muscle (or a synergistic
muscle).
While the concept is simple and intuitive (Vodovnik 1965), there are some technical and physiological obstacles. Furthermore, there are the questions about feasibility for activities of daily living and the clinical relevance for rehabilitation.