Monday, July 5, 2021

The Feel of Recovery

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.

4 comments:

oc1dean said...

I liked the book, Sensory Re-Education of the Hand after Stroke by Yekutiel Margar. I seemed to be the only documentation I could find on sensory recovery

Peter G Levine said...

Dean: I haven't read that. But I'm convinced that motor and sensory should not be viewed as seperate. they are 2 parts of a whole. thanks for the comment!

Julia said...

I read this book. It's excellent. I don't understand why sensory retraining isn't started with patients on day 1 when movement may be difficult or impossible. More precious subacute recovery time wasted. The only sensory retraining I've ever had is what I've done myself. I've even been told by some OT luminaries and their acolytes (Glenn Gillen at Columbia) that sensation isn't important, just "function". Well, earth to Glenn - no sensation, no function.

Peter G Levine said...

Remember... manged care does not pay for recovery of sensation, only recovery of movement. So therapists are reluctant to focus on that for which they will not be paid.

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