Have you ever watched a 3-month-old baby in motion? Even lying on his back, it’s obvious that my new grandson doesn’t lack muscles. He’s definitely moving those limbs, but he has no control of them; he’s just thrashing. Control will come gradually as his young brain slowly builds the collection of networked cells that allow him to sense where his fingers and toes, hands and feet — all the bits of him — are located at any given moment. His process of swinging wildly at his mom’s dangling earring will change, in the space of weeks, to a smooth reach and a firm grab. Ouch.

The name we give to that inner sense of our own body in ever-changing relation to time and space is proprioception. It develops throughout infancy, childhood and adolescence by way of a feedback loop that involves using all the exterior senses to form a sophisticated, integrated series of networks inside the brain, literally constructed over time through trial and error. Spinal cord injury commonly steals proprioception, and that loss seems connected to one of SCI’s most difficult and demoralizing side effects: neuropathic pain.

How could neuropathic pain be related to proprioception? Can the constantly changing mental map of body position be restored, absent the ability to move or feel? And if that map is restored, would that somehow translate to reduced neuropathic pain?

Relearn, Restore, Reduce

Those questions were on my mind when I spoke with Dr. Ann Van de Winckel a few weeks ago. She’s a Belgian physical therapist and scientist currently working with adults with spinal cord injury in the Department of Rehabilitation Medicine at the University of Minnesota in Minneapolis. Her research, which first investigated the effects of improving proprioception through therapy to restore sensation and movement after stroke, is now focused on neuropathic pain after SCI.

The idea is straightforward. Van de Winckel had been working for decades with adults with stroke and monitoring changes in brain activity under a particular therapy commonly used in Italy, known as cognitive multisensory rehabilitation. CMR therapy reliably improves sensation and movement in adults with stroke, and she was interested in understanding why.

“Based on my brain research, I realized that the areas I saw restored in adults with stroke, which led to sensorimotor improvement, are areas important for body awareness, and in integrating information to guide movements — namely, the parietal operculum and the insula,” says Van de Winckel.

We don’t have to understand the deep structure of the human brain and its secrets to see how she made the leap to SCI.

“These same areas are also important within the pain perception network,” she says. “So that is how I built my hypothesis: that by improving the body awareness (and restoring that network) we can actually at the same time restore the pain processing network (and reduce pain).”

Her current SCI research is done in collaboration with Dr. Leslie Morse, an expert in SCI who leads the Department of Rehabilitation  Medicine at the University of Minnesota Medical School. The two of them designed a study meant to find out if the Italian rehabilitation therapy could help reduce neuropathic pain in people living with SCI.

The Italian CMR stroke rehab therapy sounds, at first hearing, not exactly suitable for people with SCI. It involves working with a certified trainer to focus on the position of the body during various scenarios. How can a person with complete paraplegia participate in such a project? That’s what her earliest participants thought at first.

Here’s an example of what one of the first therapy sessions might entail: The participant is seated on a treatment table, and there’s a barrier set up so that the participant can only see a bit of the top of their legs. They can see the therapist, kneeling before the table, but they cannot see the rest of their upper legs nor their own lower legs.

Van de Winckel explains: “They can see the top of their legs, but they don’t see the rest. And the therapist is asking, ‘If I reach out my arm, do you think I can touch you? And if I can touch you, where can I touch you?’

“In order to answer that question, they have to reconstruct an image based on what they see of the upper part of their legs. Where are my knees, how big are my knees, how long are my shins? Where does my foot touch the floor? Where is the arm of the therapist compared to my leg?”

The goal is to help people recreate a 3D image in their heads of their lower body based on only a partial view. It’s a thinking task, not a physical one. Sometimes, while sitting, they’re asked to imagine standing, in an exercise done with layers placed under the buttocks (for example, one layer on the left buttocks, and two layers under the right buttocks). The participant can see the position of their feet but cannot see how many layers are under the pelvis.

Participants are then asked which leg would have the most weight. Van de Winckel says this forces them to consider the position of their hips compared to their feet and how it reflects on the weight that they would have on their feet

At this point, a skeptical person would say something like, “Dr. Van de Winckel, you don’t get it. I can’t feel these things. Imagining things that I can’t do is hard. This is silly.” It does seem silly, until you remember those stroke studies showing that exercises like these restored both sensation and movement to adults with chronic stroke. These exercises changed the brains of the people who did them. And yet it still seems improbable that re-building a functional proprioception network — absent real sensation and movement — could reduce neuropathic pain.

It seems improbable until you remember what neuropathic pain is: the brain’s misbegotten attempt to organize chaotic or missing signals from a damaged sensory system. My grandson, you and I have all created networks as infants that stand in our brains like radio towers tuned to specific frequencies. Our own bodies built those towers. They’re searching for recognizable signals, and when they don’t find them, they turn up the volume. That’s neuropathic pain. The harder the brain tries, the worse the pain.

The theory is that these exercises are a way to calm the system down — to give the networks, in a way, something orderly to do. Focus on your own right foot. You know it’s down there. How close is it to that therapist’s right hand? How far would she have to reach to touch it?

In some ways this therapy is similar to the work with mirrors that helps some amputees deal with their own neuropathic pain. Those missing limbs ache and burn just like those of many people living with SCI, but that pain can be reduced by doing exercises with a mirror arranged so that the intact limb is reflected where the missing one should be. The brain takes in the sight of the limb, and the networks report that all is well.

This is also the goal of CMR. The big difference between mirror therapy and CMR is that we’re not trying to fool the brain. We’re giving it real information to work with, imagination of real sensation from the actual limbs that is close enough to the feedback loop that built the proprioception network in the first place.

There are people with SCI who have already completed this training. The data gathered from their experiences cannot be published until the entire study is finished. I can say, though, that all of them are glad they took the opportunity, found pain relief and even experienced some recovery in movement and sensation.

Taped on the wall above my desk, I have a list of six things to keep in mind when writing about science. It includes these reminders:
• Inference can be premature.
• Exciting is often incorrect.

It’s important to remember, always, that when it comes to human biology what we don’t know is orders of magnitude bigger than what we do know. I’d love to be able to guarantee that a simple, noninvasive technique exists that can take your worst neuropathic pain down several notches and give you days that are pain-free. I can’t guarantee that, but I can say — based on current information publicly available — that it’s possible. What’s more, those of you who are interested and able can be part of the process of finding out more.

Get Involved

Dr. Van de Winckel’s CMR study is ongoing. She is looking for 17 more volunteers. The main requirement is chronic neuropathic pain due to SCI, at a level of at least 3 on a scale of 0-10. Subjects need to be able to get to three 45-minute therapy sessions a week for six weeks, in Minneapolis. For more information, or to learn how you can get involved, email Van de Winckel at avandewi@umn.edu.