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.
The Feel Of Recovery
My first job in research was at the exemplary Kessler Institute in
New Jersey. My second day on the job I was
told to read a series of papers on stroke-specific outcome measures—physical
tests—that I was going to be doing. I read furiously for 2 hours or so but
realized that I wasn’t going to be able to finish reading the articles that
day, let alone assimilate all the information therein. My boss, a PT, PhD said
something I’ll never forget. “Take as long as you need.” No time limit within
reason. I could spend days reading, highlighting, absorbing and cogitating and
triangulating with other research and get paid to do it.
Ever since then, in every research capacity I’ve worked I’ve taken time to read interesting peer-reviewed articles. I realize most therapists don’t have the time to do this. Most of the folks who tout being evidenced-based know clinicians only have an hour or so per week to spare for reading within their area of interest. Is it a coincidence that an hour per week is about the time folks spend in their morning constitutional? Maybe we should publish our studies on toilet paper! Of course, there's only one problem with that plan ….wait for it…you can only read it once!
I thought it might be of some benefit to condense something I’ve been reading about lately: Recovery of sensation post-stroke. We’ve all seen it, from the procreative 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 every reason to promote 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.
Schabrun SM, Hillier S. Evidence for the retraining of sensation after stroke: a systematic review. Clin Rehabil. 2009 Jan;23(1):27-39.
Sullivan JE, Hedman LD. Sensory dysfunction following stroke: incidence, significance, examination, and intervention.Top Stroke Rehabil. 2008 May-Jun;15(3):200-17. Review.