Chapters Transcript Video Evidence for Peripheral Nerve Stimulation for Chronic Hemiplegic Shoulder Pain Richard Wilson, M.D., from MetroHealth Rehabilitation Institute, presents at the Johns Hopkins Department of PM&R’s Grand Rounds on April 27, 2022. Um So what we're going to discuss today is uh the evidence for peron stimulation for chronic hemiplegic shoulder pain. So, I'm a um clinically a physiatrist who treats stroke survivors is both inpatient and outpatient. But my research is about the use of peripheral nerve stimulation and treatment of chronic pain. Uh So there's a, a natural overlap with the hemiplegic shoulder pain, which this treatment was actually initially designed for. So these are my disclosures related to the discussion today. Um So I have support from the National Institutes of Health to the study perseus stimulation, the treatment of chronic pain. I've also had some relationships with S pr Therapeutics, which is a company that sells the devices prefer for stimulation. So, the objectives of this discussion is to go to the current evidence regarding efficacy of peripheral motor nerve stimulation for the treatment of hemiplegic shoulder pain, uh then identify the implanted and percutaneous approaches to the treatment as well as introduce to you a theoretical mechanism of action for this treatment for hemiplegic shoulder pain. As I go through this, please interrupt me, I'm happy to answer questions or clarify anything. Um Somebody will have to let me know if something comes up into the chat, which I won't be able to monitor. So, shoulder pain is common after stroke, for those of you who treat stroke survivors likely see this all the time. Um It's estimated that for those who have moderate to severe impairments after stroke, that 60% of individuals will experience shoulder pain. So this is a particular problem when we're focusing on rehabilitation outcomes, people's shoulder hurts, they have difficulty participating in therapies. And much of what we know about the neuroplasticity to improve recovery with therapies is uh based on repetitive task practice. And that can be hindered by disuse for people who have painted their shoulder that makes them not want to participate in the therapies outside of recovery. This can still be a problem with function. So there are obvious ways that shoulder pain affects function such as affecting the way somebody dresses if they're trying to get an arm through a sleeve. But then also in non obvious ways, 13% also say that having shoulder pain after a stroke can affect their walking. As with any chronic pain syndrome, hemiplegic shoulder pain is associated with worse quality of life. And for these reasons, this is important in the rehabilitation of people after a stroke. If we look at a list of what has been proposed as a cause for hemiplegic shoulder pain, it's a very broad list. Um and there are different reasons for this one. Is, it's likely that there are more than one mechanisms that the shoulder pain um is caused by after a stroke. And also the admission that we don't know all there is to know about hemiplegic shoulder pain. So there have been different ways of systematizing uh ideologies for shoulder pain. This was from Kliman that was published in 2011. Um And many of the theories are that impaired motor control uh of different sorts, whether it's a placid motor control or spastic motor control, increase the risk for soft tissue lesions that then can create hemiplegic shoulder pain. There are also changes in the nervous system that can uh contribute to this as well. It's important to uh stop now and make sure we're getting on the same page of, of what hemiplegic shoulder pain is for the rest of this discussion, you know, as I said before, it's a very broad uh syndrome. Um But not all that is relevant to the evidence regarding peripheral nerve stimulation. So, particularly related to altered peripheral and central nervous system activity. There's a number of different aspects of the sort of pain that we won't consider. One is peripheral nerve entrapment. Uh And really, this is more theoretical than something that is known to happen. Uh This is based on the idea that if somebody has pheno subluxation that there can be either traction or entrapment of uh brachle uh nerves to create shoulder pain. So that's not, well, documented that it actually occurs. Shoulder hand syndrome is also known as complex regional pain syndrome. So that can cause shoulder pain, but that's not something that's been studied with uh peripheral nerve stimulation as a treatment nor has central poster pain. And in fact, uh people with those diagnoses would have been excluded from trials. Spatial neglect would not be uh considered in in this syndrome. Um and also adhesive capsulitis, which is clearly a different um entity than what would have been included in any of the studies. So, otherwise, um the syndrome of a shorter pain that has been put in the trials is still very broad, uh includes many different pathologies. There are a number of options that are available for treatment and when looking at randomized control trials for hemolytic shoulder pain, you know, it's clear that we don't know as much as we should. Uh considering oral analgesics and physical therapeutics or exercise based therapy or shoulder pain after stroke. You know, those are standards of care. Uh but we don't know how well they work. And partly that's due to the many different um things that are associated within those treatments. You know, there are many different oral analgesics that could be used. Uh not one of them is preferred for hemiplegic shoulder pain. So we, we do avoid some such as nsaids which increase the risk of stroke. Uh physical therapeutics is also something that's very um broad in its application. So different therapists uh use different techniques, different institutions uh in in the uh techniques are also tailored to the individual who's receiving treatment. But again, those are standard of care. All of my patients tend to, to use those in one form or the other. Uh There's some evidence for botulinum toxin treatment in the treatment of spasticity for one month after a stroke, but not beyond that. Uh there's some evidence for robotic therapy and corticosteroid injections being efficacious at one month. Uh corticosteroid injections have some evidence. At three months. Super scan. The nerve block is shown to be uh efficacious after three months. Uh Though interestingly, the three month data also include as the injected uh corticosteroids. So it's, it's not sure if it's really a nerve block effect or whether it's a systemic corticosteroid effect. So, surface electrical stimulation um in the form of neuromuscular electrical stimulation where muscle contraction is, the goal is known at this point through multiple systematic reviews to not be effective. Um The percutaneous peripheral stimulation where muscle contractions go has been found to be effective. In multiple studies. It has been shown that after a temporary treatment that there can be a long term effects one year after the cessation of treatment that individuals are still doing better than controlled therapy. So we'll go over some of this. So, percutaneous motor peripheral nerve stimulation for pain relief is based on the prior treatment of using surface stimulation to create muscle contraction to improve biomechanics at the shoulder decades ago, it this was more common than it's used now. Uh And it was thought that subluxation was one of the biggest contributors to having hemiplegic shoulder pain. And so the idea was to stimulate the muscles to create muscle contraction that would improve the strength of the muscles, reduce subluxation, restore more normal biomechanics and thus resolve shoulder pain. Much of that is not believed at this point. But that was the basis for why percutaneous peripheral nerve stimulation was invented. So, if this was invented by my chairperson, Doctor John Chey, right. And the reason that the percutaneous form was uh designed was because patients who are undergoing surface stimulation found it difficult. They would wear these electrodes for many hours a day uh over the course of weeks to try to get the effect. And that was painful that the skin is a poor conductor of electricity. So to have a high enough intensity, create muscle contraction uh can um stimulate receptors within the skin to create pain. It's also difficult for uh patients to make sure that the electrodes are getting over motor end points to create strong enough muscle contraction as well. Uh So, having a percutaneous system in which electrodes or tunneled to the muscles, uh provides a way to anchor the electrodes in the muscles for uh long term use also bypasses the painful effect of the skin. So the initial way this was designed was actually with four different leads going to the, each one, each, the trapeze of the affected shoulder, the super Spinatus poster deltoid and middle deltoid. Um And for those of you who are involved in research, uh the case report for this treatment was first published in 2001. And uh it took until I believe 2018 for the treatment to be FDA approved. So it's a very long road to get new treatments out to our patients. Bye. So in the current use of Ron stimulation for hemiplegic shoulder pain, it's with a percutaneous electrode with a single electrode that's placed through the skin and it's anchored into the deltoid muscle uh in between the middle and poster deltoids and the anchoring reduces the risk of migration that's attached to an external stimulator. And that stimulator provides an electrical current to stimulate the motor end point to the x-ray nerve. So that the middle poster deltoid muscles contract every 30 seconds, there's a five second ramp up. It says that it's maximum for 10 seconds, a five second ramp down and then off for 10 and then so it repeats that 32nd cycle. Most of the research has the stimulation dose at six hours per day. And the uh FDA has approved this device for the use for 60 days so that the electrodes that is placed through the skin can be in place for 60 days. It can be used for a shorter duration as well. Uh When the uh treatment has ended the electrodes removed through gentle traction. Uh that happens in the clinic in between the implant and the explant of the electrode. Uh the person using it in the community, they can really do what they want. They control when stimulation occurs. There's some uh ways to control intensity. Um So it's, it's really a pretty easy treatment uh for participants once they have the electrode in place, this is a short video showing the implantation of the percutaneous electrode. So this is information that comes with the tray or uh in, in the in the tray. So the uh test electrode is placed through an anesthetized portion of the skin is the stimulation is is used to test contraction of the muscles which you can see by uh movement of the the test needle. A sheet is left in place so that the wire electrode can be introduced to the location that was already tested within a needle introducer uh that is then connected or tested that has been cut out due to time. But the needle introducer and the sheath are then removed, leaving the wire electrode in place that's hooked up to a connector and cabling. So it can be connected to the stimulator. But the goal is for the person to have a comfortable contractions that they can uh tolerate for up to six hours per day. Um The way you see the electrode exiting the skin. Um and the uh connecting block is what a person would go home with. They cover this with Tegaderm. They're able to take a shower with a Tegaderm covering. Uh We only ask that they not submerge their shoulder into water. So no baths, no swimming, but otherwise they can do what they want. The stimulator that you see on, on this person's back would be in a convenient location for when they're undergoing treatment. Uh It's just that they're back here because of the sterile field and to allow the coordinator to have access to it during the implant procedure. So there are a couple of devices that have been tested in the treatment of hemiplegic shoulder pain. So this is the uh Sprint P N S system. It's manufactured by S Pr Therapeutics in Cleveland Ohio. This is the direct descendant of what was uh invented by John Chain. So it's a memory invasive procedure as you've seen for implantation. Uh The stimulators can have one or two electrodes for stimulation. So, uh as you can see, and this picture and the treatment of low back pain where there are muscles that are bilateral. Um you can have two channels for stimulation. Case of shoulder pain is typically one channel. The, the F D E said the electrodes can stay in place for up to 60 days in uh practical use or in the clinic. The amount of stimulation is prescribed by the team who's uh implanted it from motor stimulation in which motor end points are stimulated to create muscle contraction. Most studies for different applications have used it for six or 12 hours a day. There are some applications for sensory stimulation. So the the stimulation of sensory nerves in which uh it's used all day long. So particularly in the case of post surgical pain relief, it's used for 24 hours a day. Again, in the for shoulder pain, it can be implanted and explanted in an ambulatory clinic. It doesn't have to be in a, a procedure room. And for shoulder pain applications, it doesn't require any external imaging. It's I pretty simple to get the lead implanted within the deltoid muscle to stimulate the motor end points. Um Though some sensory applications do require imaging to make sure that you can get the electric close enough to a nerve. The stem router is also uh an available device that's approved by the FDA that has been studied for the treatment of hemiplegic shoulder pain. So this is not percutaneous. There is an electrode that is placed completely under the skin. Um the uh energy for the stimulation as well as control is sent through. And a um a device that's worn on the outside of the body, it's uh to an adhesive pad like to the skin and there is a remote control to control the external pulse transmitter. Uh It's rechargeable with an external power supply. An implant isn't uh very in invasive, that's minimally invasive but explant of the electrode if it needed to come out is much more invasive? Are there any questions about um implantation or the devices used for peripheral nurse simulation before we go into uh discussing the evidence? Hi Rich. This is prey. Um Great to see you here. Um Yeah, my question was uh this is very exciting. Oops. Um So sorry, ambulance all around me. Uh But I wondered if um so is it wireless? Why is it that um the Bioness device is more invasive than um the other than, than the Sprint P CS device? Uh So in the case of the Bioness, this electrode is completely under the skin. There, none of it is um traversing the skin. So it, it is a uh intended to be a permanent implant. So once it's there, the hope is never to have to remove it. So um it is, the implantation is a little bit more invasive, but it's still considered minimally invasive. But the explantation because the skin goes over it, there's no access to it once it's in place becomes more invasive in the case of the S B R system. Um There, there's a wire electrode that is introduced with a needle, but that electrode remains protruding from the skin throughout use and at the end of use, at the end of uh whatever time period it's intended to use for up to 60 days. Uh It can be removed just by gentle traction at the end of the electrode. I see. So is there the potential for infection is the potential for infection greater with any one of these? Because the wire is sticking out the short duration of use for the sprint device. Uh is one reason that it's, it's not that big of a risk, but then also it's not that the design of the electrode contributes to a low infection risk. It's a coil design that allows the tissue to scar around it to prevent um bacteria from going from the skin surface into the uh body. Uh So in that way, uh it's a pretty low risk even though it's a percutaneous system, that's, that has something going through the skin for two months. Uh The bio has a pretty low risk for infection as well. There, there are other implant and stimulation devices that have a much higher risk. Got it. And is it only could it be done in any muscle or is it only specific muscles that um the implants are approved for? But it can be any muscle throughout the, the body that it can be used for. And again, some applications are muscle based and some are sensory based. So it may not be a muscle target. It could be a nerve target. Uh in the case of shoulder pain, the sprint device has only been studied uh stimulating the uh middle and posterior deltoids. Uh The earliest uh method for stimulation that was made by John Cha. They actually use four electrodes, stimulating trape super A poster deltoid and metal deltoid. People might use it differently in the clinical realm, but it's not been studied that way. Thank you so much. You're welcome. So, the first randomized controlled trials on gover were uh they were conducted here at our institution. Uh And the question was whether or not single lead peripheral nerve stimulation was better than physical therapy for chronic hemiplegic shoulder pain. Uh So this is after the early randomized control trials, utilizing the four lead system. So as a single site randomized controlled trial, uh we recruited those who had shoulder pain after stroke, uh they had to be adults, the pain had to be chronic. So at least three months of having shoulder pain after their stroke, it had to be moderate to severe. So it had to be at least a four on a 0 to 10 scale zero being no pain and 10, the worst pain. And that was based on the worst pain somebody experienced in the last week. Uh They also had to have some sort of weakness of their shorter abductor. So anything less than full strength would suffice. The participants were randomized to two different treatments. Uh The first was peripheral nerve stimulation as I've described. So as a single electrode placed between the metal and poster deltoids to stimulate the motor end point of the x-ray nerve to create muscle contraction every 30 seconds. Uh And that was done for six hours a day, for three weeks. The electrode was in place for four weeks total. The first week was a period of not having stimulation to allow some scar tissue to form around the electrode. The alternative treatment was an exercise based treatment that we term physical therapy. So this was eight hours of physical therapy over four weeks. Uh So two hours per week, the uh therapist educated the participants on proper positioning and handling of the mire limb slings were issued if it was felt to be uh an improvement. The therapy focused on improving range of motion and strength as well as task specific therapy to improve activities of daily living. Participants were also given a home exercise program uh that they were advised to use during the four weeks of therapy and also during the three months of follow up, the 25 individuals were recruited to the trial, 13 randomized to peripheral nerve simulation and 12 to physical therapy. Our primary outcome was the worst pain in the last week. Uh zero being no pain, 10, the worst possible. And this is showing a week of the trial in terms of preity of shoulder pain. About 60% in each of these groups have had shoulder pain for at least 18 months. So most of them on average were uh well into the chronic phase. So both groups started off in the severe pain range in about a 7.5. And you can see that with treatment, both groups have improvement. Uh The peripheral nerve stimulation group experienced greater improvement. So we expect the physical therapy group as a control to also improve the receiving active treatment. At the end of four weeks, treatment ended except for the advice of the group of physical therapy to continue their home exercise program, then they were followed for a total of three months. And you can see that those in the peripheral nurse simulation group maintained that reduction in pain to a greater extent than those that received the exercise based therapy. So this is also something we see in our clinics that patients do very well when they're working with therapists. Uh And for some reason, after therapy ends, some of those gains tend to be lost. But at the end of treatment, there was a statistically significant and clinically relevant advantage to performer stimulation. So we also had a measure for global success of pain relief. This was a reduction in pain of 30% at the end of treatment that that was followed for the remaining uh followed time assessments over the three months. So 67% of those with peripheral nerve stimulation experienced success compared to 25% in the control group. To the end of this trial, we concluded that single lead three week peripheral nerve stimulation was more effective in reducing pain for at least three months than physical therapy. Uh There are some other outcomes that were measured in which both treatments were uh effective in improving pain. But there was not a statistically significant difference. Uh So, uh both experience reduction in pain interference, that's from the brief pain inventory. Uh It's likely that the clinical difference that was estimated or the difference between peripheral nerve stimulation and physical therapy was clinically relevant with a greater reduction per peral nerve stimulation. Both experienced improvement in bodily pain quality of life that was measured by the S F 36. There's an improvement in both shoulder abduction, strength and pain free, external rotation range of motion. It's unlikely that these improvements are clinically relevant for stroke survivors. There was improvement in operations from the Elmeer Assessment and it was also found to be a safe treatment. So there were no serious adverse events with the trial. Um There were three individuals who had a portion of the electrode tip retained in their muscle. So in some individuals, there's more scar tissue around the tip and during removal, a portion will be left behind. Uh They don't feel it, it doesn't cause them discomfort. Uh And we don't retrieve it, we give the person information so that if they were to have an MRI since they're stroke survivors, that that's something they might need. Um And lets the radio radiologists know how to obtain images safely with this metal being in the arms, it has been tested up to 1.5 Tesla to be safe for MRI. So we were happy about the results of the first trial. Um but it was clear that things can still be changed to improve treatment. Uh So we designed a two stage treatment for shoulder pain to try to improve from there. Now, from our two prior randomized controlled trials, whether it's the four lead or the single lead, approximately uh 65% of those individuals receiving Perner stimulation had successful treatment which was much better than the control situation. And while that seems to be much better, we wonder why it can't be 100%. So, a study was conducted uh trying to determine which clinical factors in stroke survivors will predict successful treatment with per nerve stimulation. Uh And these were post talk data from the first randomized controlled trial of the uh four lead system. Then in that the peripheral nerve stimulation was delivered for six weeks. The number one clinical factor for predicting successful outcome was actually time from stroke um which is closely related to also the duration of shoulder pain for me. Uh many of the stroke survivors. So you can see that with six weeks of four lead stimulation that the peripheral nerve stimulation is associated with a robust reduction in pain for individuals who are closer to their stroke, less than 18 months in the control situation, which is uh the use of a hemi slink, there is a much lower likelihood of success. So 94% of these individuals have a successful response to the treatment compared to 7% in the control group. If we look at those for more than 18 months from the stroke, we see that peripheral stimulation is associated with, with a reduction in pain. However, once treatment ends, their pain returns to closely mirror those in the control group. And in fact, there's not a difference between the groups. So we wonder what could be done for these individuals who still suffer from chronic shoulder pain that might improve their pain long term. So we designed this two stage pilot study. Uh This was a four different sites throughout the United States as a convenient sample, single arm. So the stage one of this two stage treatment was the percutaneous peripheral nerve stimulation treatment that I've already described. Uh we recruited participants who had shoulder pain for at least six months. It had to be chronic, had to be moderate to severe. So at least a four on a 0 to 10 scale for the worst pain. In the last week, they had to be refractory at two different treatments that could be oral analgesics, a shoulder injection or having gone through an exercise based treatment for their shoulder pain. And they also had a, a weakness of the shoulder of doctors. So this first stage was six weeks in length, but it was divided into two different periods. So the first three weeks was a blinded sham introductory period. So the person had received the electrode. Uh They were given the stimulator advice on how to use. It, advised to use it six hours a day. But the stimulator didn't deliver any electrical current. It uh appeared to deliver the electrical current the battery would drain but no current was delivered. Uh And other studies about this method show that about 60% of people in the sham uh phase believe that they are receiving electrical stimulation. After three weeks, the participants were brought back with, they were advised that we were changing their electrical stimulus, so that might feel different. So at that point, we put them in an active um phase of treatment so that they would have a electric current creating muscle contraction every 30 seconds for six hours a day. So participants were considered a success if they had a two point reduction on a 0 to 10 scale at the end of the treatment phase compared to the end of sham, or if they ended the treatment phase as being completely pain free. If they had successful treatment and their pain returned, they could go on to the second phase of treatment. So this was receiving an implantable stimulator that's placed under either general or local anesthesia. It was connected to an electrical lead that was anchored into the deltoid muscle all completely under the skin. Participants would use the stimulation six hours a day and control it via a remote. The stimulator contained a battery that had to be charged every two weeks. Then we followed the participants for two years. So 28 individuals were enrolled in the trial phase of those five and successful treatment of pain, their pain had returned and they were eligible to go on to uh the fully implanted phase. On average, the time for stroke for this group was 3.1 years. So our primary outcome is a again the worst pain in the last week. So zero being no pain, 10, the worst pain possible. And this is showing week of the trial. So at the end of this sham period, so about midway through, uh there's a 36% reduction in pain. So we know that uh patients as well as research participants who are undergoing a treatment that's involved with the procedure are likely to have placebo effects. Then these are, are different. At the end of the trial phase, their pain had reduced to 71% of baseline. At that point, they received their fully implanted stimulator and they were followed. And you can see that throughout the uh follow up time period that their pain was reduced by 80 to 90% of baseline. So this is a pretty big deal for this group. Um being more than three years from this drug who have had chronic shoulder pain, uh for a very long time know, I'm often asked, well, how do we know if participants need sustained stimulation to control their pain? And, and based on this trial design, we don't actually know how long somebody needs stimulation to resolve their pain. But we do have a natural experiment from one of the participants. So this participant started off at a baseline pain of nine underwent the trial phase that took them down to a three, they then had implantation of the uh stimulator that completely resolve their pain with daily use by uh about three months. But then the stimulation was turned off. So this individual had a myocardial infarction. Uh And when they were admitted to the hospital, the cardiologist didn't want the experimental stimulation being delivered. So asked for the stimulation to stop which it did. And you can see that within six weeks, the pain had returned to baseline at that point. Uh The cardiologist allowed the stimulation to restart again in about six weeks, uh back down to a zero out of 10 and they're maintained at a 01 for years. So I don't know if this is general liable to other individuals. Uh But it is interesting to have this uh one natural experiment. So there's a very uh good response, particularly looking at a 50% pain reduction for a successful outcome. When comparing to the end of m, there's a more than 90% reduction in pain interference. And that's the brief pain inventory measure and also improvement in pain free external range of motion. Unfortunately, that stimulator uh was only available experimentally, it's not FDA approved. So it's not something that you could use for your patients, but the stem router from Bioness could be used. So it has been studied. There is a case series that was published by Mick Roberts. Uh say an abstract was presented at the North American Neuromodulation Society by Mick Roberts in 2016, in which seven individuals with hemiplegic shoulder pain were enrolled in the trial. The stem router was placed to stimulate the axillary nerve and then participants were followed. Um This wasn't a rigorous trial so that the the follow up period is from one month to 48 months. You can see for this uh outcome of the visual analog scale for pain, uh 0 to 10, 0, no pain, 10, the worst pain imaginable that looking at the green bars, which is the pain after stimulation that all of these individuals that they graft uh have a lower pain than their pain before stimulation. So this provides some evidence that this device could be used in a similar way that I showed in the other trial. So as mentioned, uh there are adverse events that show associated with Perner stimulation. So for percutaneous stimulation, that sprint device, it's mostly skin irritation from having the device adhered to the return electrode that's in place for up to two months or the skin covering over the device, there can be a breakage of the electrode which should be less than 10%. And looking at all the available studies, there is risk for a skin infection but it's less than 1%. The fully implanted devices have uh additional risk. So, implants like pain at 12% a higher risk for a pocket infection that's for implant devices. Um Other than Bioness, there could be a lead fracture that would render the device useless at that point. And also uh reports and literature of lead migration. Uh This is uh yeah, uh stem router migrating from a a gluteus muscle. So when it comes to the mechanism, you know, if this is effective, how does it work? We really don't know how it works. But we have um some ideas, you know, this is caused us to really look at what we think is happening and and evaluate it. And as I said, we don't think that subluxation is the cause of shoulder pain and and the subluxation is not being addressed by peripheral nerve stimulation to improve pain. You know, not everybody with hemiplegic short pain has sub subluxation, it's only only half of them. Um And we can improve people's pain without improving subluxation. We don't think that altered biomechanics is causing shoulder pain and being addressed by perier nerve stimulation. So we can measure improvements, but those are so small that they're not likely to be clinically relevant also exercise based therapies can also improve uh biomechanics yet not be as effective improving pa. And finally, we do not think that we're affecting spasticity. We've been able to show improvements in pain. Uh for those with heavy bleeding, shoulder pain did not affect their spasticity. So we are now thinking that whatever is happening patho physiologically to allow chronic pain to exist is likely different than what caused the pain to occur initially. So there was something that occurred to cause acute pain, but then something within the body changes that allows it to be maintained for months or years after that injury. Uh and it's likely maladaptive neuro plastic changes. And this is a current thing for for many different chronic pain syndromes that it's a problem within the brain or the spinal cord. Uh that's maintaining the pain. One of the things that is uh attributing to this at least theoretically is central hypersensitivity as the but can exist to maintain a chronic pain state. So, central hypersensitivity for those of you who aren't aware, there's an adaptive response of our bodies. It's it's part of our normal responses to uh pain or pending tissue injury. There are some parts of it that can be acted peripherally but that it can be completely needed centrally as well. So this is a protective mechanism that our bodies use. Uh It can result in spontaneous pain or allen having pain to something that shouldn't be painful. This expansion of painful areas where people with hemiplegic shoulder pain often have pain beyond their shoulder, it goes down their arm, it goes to their back, up to their neck. And there can also be diffuse hyperalgesia. So changes in the entire sema sensory system to change how pain is perceived or when it is perceived, the experimental conditions, this last minutes to hours if the stimulus is removed. Um But it's clear that this can be uh maintained in the absence of a harmful stimulus in a pathological sense. Uh And there is evidence this is happening in those with hemiplegic shoulder pain. So we conducted a study comparing those with hemiplegic shoulder pain to pain free controls after stroke. And we evaluate their pressure pain thresholds. It's looking at at what pressure that they start to experience pain. Uh We do that with a uh pressure gauge as seen here. So at the affected shoulder, those with tic shoulder pain have an earlier onset of pain perception to the application of pressure compared to pain free controls, that's not very exciting. Uh Most of you would have guessed that anyway. But it's also the case that their non affected shoulder and at the non affected leg. So throughout the body of people with chronic hemiplegic shoulder pain, on average, they have a a change in perception of pain. So this can only be mediated centrally. Uh and it's well known to exist in other chronic pain syndromes that compared to pain free controls, those with chronic pain, have a change in how they perceive pain. So, if this is the case, um how does it work? Now, this is our, our theory on what is happening. We haven't yet uh proven it. So, peripheral nerve stimulation directly activates alpha motor neuron eer which is what creates muscle contraction, but also sends the signal through A and the one A one B nerves, it's likely that the brain interprets the direct stimulation as noise but the muscle contraction is different. So that is also sending information into the nervous system on the spindles called the tenant organs, joint capsules, a cutaneous A that the central nervous system understands. And we believe that this somehow interrupts that uh process that allows chronic pain to exist. And that in the case of peripheral nerve stimulation, you can actually get desensitization that a temporary treatment can create long term pain relief. It's clear that some individuals require a persistent uh stimulation for pain relief, but many can have a temporary treatment for long term pain relief. Uh So in closing, what we, what's coming next with this? So we wonder if we can actually have a better effect, peripheral nerve stimulation and an exercise based therapy such as BT are combined. So we're at the end of a multi site, double blind placebo controlled randomized trial of those with shoulder pain after stroke or randomizing individuals to three groups. One looking at a combined treatment of Perner stimulation and physical therapy. And then we have two different groups that have a sham for either stimulation or therapy. So we're uh treating individuals for four weeks and then following them for a total of six months to look at long term outcomes. The primary outcome is the worst pain in the last week. But we do have a global success measure and then we have some secondary outcomes. Uh Many of the ones that we've also shown but improving our ability to measure uh shorter kinematics using optokinetic, uh looking at quantitative sensory testing to evaluate changes in their sema sensory systems. Um And hopefully we can give you results in the next couple of years. So I'll end there. Um I'll end with the summary of evidence. So there's level one, a evidence that Perner stimulation is associated with a reduction in chronic shoulder pain and hele shoulder pain. Uh One A that it's associated with reduction in pain, interference with the activities of daily living. It's one B that's associated with reduction in shoulder impairment. Again, the clinical relevance isn't known it's not likely clinically relevant. Um And there's to be evidence that fully implanted per nerve stimulation may be effective for treatment of he pig shoulder pain and those who receive temporary relief from a percutaneous treatment. So I'll end there and I'm happy to take any questions, quiet group today. Um Thank you for sharing. Um This is some really interesting um use of technology. I think it's a nice um addition to our tool set as opposed to just our typical um medication route. So, um a pre did you have a question? Well, I just wanted to say thank you for uh a very stimulating presentation. Um Sorry, I had trouble switching my video back on. Um, but I, I did have a question but I didn't wanna hog all the Q and A. So, um oh, does anyone else have any questions? I think you could go for a? Ok. Well, so, um it's, I think it's very exciting and interesting to um you know, know that percutaneous muscle stimulation might interrupt this whole cycle of pain. How is this, you know, what about tens, you know, tens is based on a similar idea, but it's more just cutaneous stimulation. Um And the whole idea is this gate theory of pain. So, is there anything in common with, you know, is it that we are bombarding the central nervous system with this input? So it, it basically overshadows the painful inputs and alters perception. Um That's a great, great question. So, uh different than tens or spinal cord stimulation, uh which those are thought to work on gate theory, mostly though there are other theories on, on what might be happening. Um And they're blocking the uh painful sensations from the periphery, from getting to the central nervous system. That's the way they thought they worked. They aren't associated with long term pain relief. If you stop either of those forms of stimulation, the pain returns in, in in relatively short period of time. So what's different here is trying to communicate with the central nervous system in ways it understands that using uh the body's receptors. So when the muscle contracts and you get changes in length and force the receptors that send information into the central nervous system that it understands spinal cord stimulation in tens are not uh forms of stimulation that mean anything to the central nervous system, it just comes through as, as noise. Um So, and that, that is the main thing that we think is different and why this form of stimulation is more effective. Uh And it's, you know why is exercise based therapy effective? It's likely moving the body, you get changes in muscles and joints and that sends information into the nervous system. Uh This might be similar uh that, that's our theory and that and how we approach it. Um So until other forms of stimulation where you could provide sensory stimulation that the nervous system can interpret, it's unlikely that those will be more effective. So in other words, you're stimulating the muscle, but you can stimulate it for longer than physical therapy can because that's just episodic and for a short duration. Whereas here you can go up to six hours, eight hours. Yes. And if, if somebody is not moving their limb, it's unlikely to be associated with the worse in pain to have a muscle contraction by itself. Whereas going through an exercise based therapy, the joint is moving. Uh, and that may create pain. So then, uh, it may not be, it may be, uh, one aspect that's different, uh, for some individuals going through an exercise based therapy where here it's pain free to get that information from the muscle, going into the central nervous system. Yeah, it's interesting that stimulating one muscle could have that effect. Yes. Uh There, there is um in nonhuman studies, there's some evidence that you can simulate elsewhere in the body that it influence what's happening within the central nervous system. Diffusely. Uh We haven't been able to study that in this case just because we can't get reviewers to agree to it, to get us funding. But I agree it'd be interesting to try. Great. Thank you so very much. My pleasure. Thank you again. Um I'm sure that if anyone has questions that come up at a later time, they can certainly reach out to doctor Wilson and um he may be able to help um and I appreciate everyone for logging in today and have a great one. Have a good day. Thank you. Thanks. Thank you very much. Created by
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