I have a few comments about SCI
Spinal cord injury manifests symptoms asociated with three regions: - I'll
use motor responses as an example
region#1 the damage distally encroaches on the interneurones above causing
paresis of muscle which may still have some voluntary activation. The motor
units affected are lower motor neurone lesion and assuming no plasticity /
recovery then the muscle fibre of that motor neurone will atrophy.
Compensation hypertrophy of the intact motor units can occur with
rehabilitation. These muscles (depending on the motor units activated) may
have an upper limit of their capacity to strengthen. The role of ES in
these cases are to modify/ facilitate motor control patterns rather than
generate torque using an external drive source.
The next level distally is the zone of injury.
Here the motor units have a lower motor neurone lesion . No Voluntary
control nor any spinal reflex impact. These muscle atrophy due to disuse.
If the final common pathway is destroyed then FES is impractical. - this
is often the case at the lesion site although the zone varies in width.
The region below the injury is where the final common pathway is intact if
the cord is still intact (i.e not the corda equinae). These muscles
therefore are motor units that are linked to the spinal reflex system.
since the cortical control of the reflexes are primarily inhibitory then
these motor units tend to exhibit hyper-reflexia (+/-velocity dependence)
- spasticity. The muscles are provided with some input - and therefore
often show less disuse atrophy than a completely denervated muscle - this
varies considerably. Generally the uncoltrolled extension pattern of the
lower limbs creates functional problems , however some individuals also
have functional problems with excessive hypotonus - for example very low
tone in the trunk may make transferring difficult due to the spine
stretching out when the individual with paraplegia / low quadriplegia
attempts to transfer. Some individuals are able to facilitate movement
utilising the tone spasticity.
One of the problems of spasticity in individuals with SCI is the
unpredictability of it. Short of a cue for SCI research into "controlling
Spasticity in the realtime" is probably an area of great need for the
function and well being of individuals with SCI.
FES across the zones:
The deinnervated zone is a probelm in rehabilitation and the application of
FES in the upper limb especially if the shoulder stabilisers that shpould
provide proximal stability are dennervated. In the case of an individual
with paraplegia this maybe overcome by the latissimus dorsi's ability to
stabilise the pelvis (especially with arms fixed) acting through the
thoraco-lumbar fascia.
Pain:
In terms of the perception of pain from each region, it is more complicated
since the brain is the integrator of the feedback or apparent feedback from
each region. It reacts to changed afferent feedback in various ways
including alterations in the receptive fields and perception thresholds.
I know little enough to comment.
Garry.
______________________
Garry Allison
Helen Slattery
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