Below is an article I wrote in a PT trade magazine years ago. It describes, theoretically at least, how to get sensation back after stroke. Turns out, nothing new under the sun. Getting back sensation is the same as getting back movement. Repeated attempts at feeling drives the brain to be better at feeling.
There are 2 ways of retraining feeling: active and passive. Passive seems to be more for tactile stuff, active is more for proprioception (the feel of movement).
But movement and sensation double back on each other. Movement affects sensation because if you can't move the brain stops listening for movement. And if you can't feel, your movement goes haywire.
Rehab clinicians have seen it all... from the proprioceptive deficits of the apraxic survivor, to the hyper-sensitivity of survivors with
shoulder/hand syndrome (RSD), stroke deals an unpredictable hand of sensory dysfunction
to many survivors. Approximately 60% of stroke survivors have some sort of
sensation loss. Of all the squealae after stroke, loss of sensation is the most
perplexing for researchers. Most research focuses on the effect of interventions
on recovery of movement and function. There
are reasons that research focuses on movement and not on sensation.
For instance,
movement is considered more important. In some ways it is. Edward Taub, the
developer of constraint induced therapy (CIT), proved that primates could move
limbs they couldn’t feel before he was out of graduate school in the 1960’s. So
if movement can be relearned without sensation, there is less focus on that that relearning. Also, any gains in recovery of movement are easily
seen, and we focus on what we can see. Sensation is much more difficult to
measure. But any therapist worth their salt knows that sensation impacts on
movement. Movement is the Ying to movement’s Yang; neither does well in
isolation.
If a therapist wanted
help a client relearn sensation, how would they go about it? First, understand
that sensation would, in fact, be relearned--in much the same way that movement
is relearned. The same rules apply. We know that repetitive practice
reestablishes movement. Although much more research needs to be done,
repetitive feeling seems to help
reestablish sensation. Also, movement itself seems to drive increases in
sensation. The more the survivor moves, the more the sensation of movement
becomes ingrained into the neurons of the brain and the more the brain
“listens” to the feeling of the movement. The more the brain listens, the more
neuroplastic rewiring occurs to make the brain more perceptive to the
sensation.
There are two
veins of inquiry that researchers are following that promote repetitive feeling;
passive and active training.
Passive Training of Sensation
(PTS)
PTS usually involves surface electrical stimulation.
This would be delivered in much the same way transcutaneous electrical nerve stimulation (TENS)
is. That is, there is no muscular contraction. The hypothesis is that
continuous signals sent from the peripheral
to central nervous system reallocate neurons
to feeling the limbs. Stimulation sessions ranged from one session for one day
to one session per day for several weeks. Other PTS paradigms have used
pneumatic compression, thermal stimulation and vibration to a portion of the
body.
Active Training
of Sensation (ATS)
The research in this area has used a variety
of training techniques. ATS involves having the stroke survivor actively
involved in training. Included has been practice determining where limbs are in
space with eyes closed (for proprioception) and practice with localizing
sensation (“Where do you feel this?”). Also used is repeated challenge to stereognosis
(the ability to perceive the form of an object held in the hand).
Ultimately, the
best paradigms for reestablishing sensation involve the blending of ATS and
PTS. Since the more movement that is
done the better the brain becomes at listening, anything that compels the
survivor to move will tend to drive sensory recovery. Repetitive practice paradigms,
including CIT may be helpful in the recovery of movement and the sensation of
movement.
Much more research is needed in this important
area. Every study and systematic review of sensation after stroke
agrees: The testing and treatment of post-stroke sensation deficit lags well
behind the testing and treatment of movement.
