Steve,
I think the amount of voluntary control over tone would be best determined
by the extent to which the motor learning centers are intact. Learning
takes different forms, and just because a child's declarative learning
capabilities are intact does not necessarily mean that their motor learning
(or procedural learning) capabilities are. Tone is regulated by many
different areas of the CNS, from the spinal cord, to the brain stem and
subcortical gray, to even the cortex itself. Due to the uniqueness of each
case of CNS injury, it is difficult sometimes to determine to what extent
the higher centers have control over the tone.
It is true that we can learn to override lower centers to facilitate
movement patterns. Take for instance the first time you learned to play a
difficult sport, such as water skiing. Your body was probably over-ridden
with muscle tone. Your mistakes were often over-corrected leading to poor
coordination, your body was stiff, and you may have been concentrating on
the task so hard you didn't see the buoy until it was too late... CRASH! As
you got more practice, your movement patterns were refined, you made only
appropriate corrections, and you may have gotten good enough to daydream
while performing the task. During this period your muscle tone decreases to
appropriate levels because splinting against mistakes or possible injury is
no longer necessary.
Often times, I think we misinterpret changes in muscle tone as pathological
when it may very well be the way in which we use the tone that represents
pathology. It is perfectly normal for a patient to show increased tonus
when performing an activity that the patient is not sure he or she is
capable of doing. Fear of falling or even fear of failure can cause
increased tone. Anxiety is one factor that can be controlled to help bring
out movement patterns not overridden with spastic patterns. Effort is
another. When someone gets up and walks, there are many variables to
control... balancing a moving center of gravity over an ever changing base
of support is a difficult proposition. This requires an incredible amount
of effort and concentration to control when you have muscle weakness,
sensory disturbances, and coordination deficits to contend with. Reducing
the variables of motor control can greatly enhance motor learning. This is
why I'm a big supporter of aquatic therapy and harness supported treadmill
training. But even without expensive equipment there are things I do.
First, I work on reducing anxiety by earning the patient's trust and
companionship. If he thinks I'll hurt him or make him fall, then he'll be
anxious and high tone. I talk to the patient, explain what I'm doing and
why in simple terms, and try to be fun and interesting! If I engage the
patient's concentration, they seem to be that much more likely to learn.
When starting a new or difficult activity, I provide lots of support and
take away extraneous things (simple, no obstacles, and no audience). I
provide lots of meaningful and helpful feedback at first, but quickly begin
taking it away once the patient shows some sign of "getting it." I try to
"test the waters" by periodically taking away some support and seeing what
happens. This way, the patient learns from their own mistakes in a safe and
confident way without becoming dependent on my cues and support. Finally, I
always try to structure sessions so that there are more successes than
failures and end with the successful completion of a task. I've had a great
deal of success using these techniques and I believe they're on track with
current thought in PT.
Hope this helps!
Sincerely,
Geoff Mosley, PT
MRC
Mt. Vernon, MO
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