Intro

Peripheral neuropathic pain is primarily influenced by the biology and pathophysiology of the underlying structures, peripheral sensory nerves, and their central pathways.

In this episode, Kait Nevel, MD speaks with Miroslav Bačkonja, MD, an author of the article “Peripheral Neuropathic Pain,” in the Continuum October 2024 Pain Management in Neurology issue.

Dr. Nevel is a Continuum® Audio interviewer and a neurologist and neuro-oncologist at Indiana University School of Medicine in Indianapolis, Indiana.

Dr. Bačkonja is the clinical director in the Division of Intramural Research at the National Institutes of Health in Bethesda, Maryland.

Additional Resources

Read the article: Peripheral Neuropathic Pain

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Full episode transcript available here

Dr Jones: This is Dr Lyell Jones, Editor in Chief of Continuum, the premier topic-based neurology clinical review and CME journal from the American Academy of Neurology. Thank you for joining us on Continuum Audio, which features conversations with Continuum's guest editors and authors who are the leading experts in their fields. Subscribers to the Continuum Journal can read the full article or listen to verbatim recordings of the article and have access to exclusive interviews not featured on the podcast. Please visit the link in the episode notes for more information on the article, subscribing to the journal, and how to get CME.

Dr Nevel: Hello, this is Dr Kait Nevel. Today I'm interviewing Dr Miroslav Backonja about his article on peripheral neuropathic pain, which appears in the October 2024 Continuum issue on pain management and neurology. Welcome to the podcast. 

Dr Backonja: Thank you. 

Dr Nevel: Misha, can you please introduce yourself to the audience?

Dr Backonja: Yes, I’m Miroslav Backonja, but everybody calls me Misha. So everybody knows me by that. I'm a training neurologist, and I also have training as well as certification in pain management. And most of my practice has been where neurology meets the pain, which is neuropathic pain. I spend some time basic science lab and then transition into clinical research. And I was in academia for a couple of decades and was most recently recruited by NCCIH National Center for Complementary and Integrated Health and have been there for two and a half years now. 

Dr Nevel: That's wonderful. I would love to hear more about your career at the NCCIH, a little bit and what you do in your role now, and how that came to be.

Dr Backonja: Yeah, I was recruited to help and provide clinical support to efforts at NCCIH in the phenotyping of pain and neurologists who've done research in quantitative sensory assessment and other quantitative means of assessment of pain. Coming to NIH was very rewarding and quite of a learning experience. After six months being there, I've discovered that NIH is the biggest secret in plain sight. They say in the plain sight because it's public institution and everything is open to public and it's a secret because we don't think about it. This is in particular in reference to biomedical research training, including clinical trainings. So, I would encourage everybody to think of NIH as a place to spend some time and learn. There are wonderful research opportunities as well as educational opportunities. Vast library of presentations, green rounds and different other types of courses - some of them open to public, and some of them are up to FAS, which is a foundation of advances in science education by discovering. I feel like being back in school and having fun. 

Dr Nevel: That's wonderful. Can you share with us a little bit about how you became interested in peripheral neuropathy and pain management of peripheral neuropathic pain? 

Dr Backonja: It actually goes back to my residency and fellowship. And actually, you know, I had the luck of being exposed to a couple of clinicians who actually became my mentors. First was Jose Ochoa, who was one of the first people to quote from a small fiber, C fiber specifically, and he also was pioneered in quantitative sensory testing. And the other one was Charles Cleland, who was a psychologist and who pioneered assessment of patient symptoms, developing the Brief Pain Inventory is one of the tools. That actually peaked my interest in the topic of pain and once when I started learning about pain, what is the kind of mysterious experience of humans’ pain, turns out that we have learned a lot of science about the pain and can make the pain very accessible. And I hope some of this will come to the chapter that we've provided. 

Dr Nevel: Thank you for sharing that. I think of peripheral neuropathy and I think most neurologists think of peripheral neuropathy as one of the bread-and-butter diagnosis within our field. For the practicing neurologist out there who might be listening, what do you think is the most important takeaway from your article that maybe they don't already know about peripheral neuropathic pain?

Dr Backonja: When it comes to peripheral neuropathy and peripheral neuropathic pain, it goes back to my early experience and still holds the truth. Neuropathies don't kill people, they just maim them. They create- cause lots of disability and if you add a pain to it, it can be quite disabling. In some regards, it has been neglected the area of development in neurology in terms of scientific discoveries, although things are changing quite rapidly as of recently. Main take home messages, and especially when it comes to a sensory neuropathies and painful neuropathies, is that it's one of the skills that has not been well researched and then not well communicated to the vaccine neurologist in terms of what to do with it. But most neurologist sensory symptoms are just like a noise because, especially when it comes to pain and prosthesias and allodynia and hyperalgesias, like, what is that like? It's just not knowing what to make of it. Frequently associated also with emotional components in terms of the people are either depressed because of persistence of pain or anxious, not knowing what's going on. And that really can create quite a bit of a challenge in terms of what to do with it. But once anybody who's interested learns the fact that sensory neuropathies and fever neuropathies as well could be as well and is easily diagnosed by a neurologist who pays a little bit of attention and gains some skills in assessing not only negative sensory phenomena, because that's what he as a neurologist get trained to detect and quantify sensory deficits as well as motor deficits and loss reflexes. Also, if you pay attention to positive sensory phenomena, which is part of the repertoire of symptoms that patients with neuropathic pain experience, it's not whether patients would have either positive sensory phenomena like prosthesia and pain or negative sensory phenomena. Actually, they have all of them. And that's kind of puzzling for many patients. And lots of times, very patients say, like, how can I hurt when I don't feel like, let's say, like most commonly it's lower extremities. Like I don't feel my feet, but it hurts. I mean, how come? Oh, that's a cardinal feature of neuropathic pain, neuropathic painful neuropathy.

Dr Nevel: Yeah, thanks for that. You know, I really thought that your Table 3-1 was really nice. It kind of lists through the common causes of peripheral neuropathic pain and just demonstrates the diversity of the different etiologies or other conditions that can cause neuropathic pain. And so, I encourage the listeners to review that table. But, on that topic, can you share with us what you think are the most important components of evaluating patients with neuropathic pain to maybe come to a diagnosis, to find what the underlying etiology or driver is? 

Dr Backonja: When it comes to painful neuropathies, there are actually two problems you have to solve. So, don't forget that part. The first one is finding a pathological theology. Why a person has a neuropathy, what kind of neuropathy. And then second is, what's the nature of the sensory problems? What's the nature of the sensory symptoms, specifically pain, levodenia and hypogesia. So, figuring out the theology of the B12 deficiency or diabetic painful neuropathy, you can relatively quickly or hopefully one would relatively quickly come to that at theological diagnosis. But then the second part is the diagnosis of symptoms. What's the underlying metaphysiology of that. And again, just reminding colleagues that the specific sensory phenomena such as thermal hyperalgesia is now well established to be due to what's called peripheral sensitization of C fibers, which are the small unmyelinated fibers, expressed TP 1 receptors. So, patients who will report that taking a hot shower is very painful. An example of that or when conducting sensory exam and applying if you come to the point of examining the perception of warm and hot and patient affords the pain. That's just the hallmark of the C hurtful sensitizations to C fibrous sensitization. On the other hand, if somebody has mechanical ordinia like putting the shirt on hurts, putting the socks hurts. Well, that's evident to central sensitization. These are the simple, relatively simple but symptoms or signs that could have implication if those patients with central sensitization are more than likely to benefit from medications that restore descending inhibition, such as tricyclic antidepressants or SNRI’s. And so just paying attention to that, it gives a clinician being a clinician or a neurologist, like, let me consider prescribing medication that have central A acting properties. Or if it's purpose sensitization, something we have like a sodium channel blocking property, things of that sort. Actually, there are some other strategies such as antagonist TRPV1receptors, the capsaicin base. Those are the kind of things that can help a neurologist kind of take the evaluation of painful neuropathies to the next level.

Dr Nevel: Yeah, the- by getting a careful history and exam, that can influence what treatment you prescribe to patients. Understanding whether it's central or peripheral. On the topic of treating patients and talking with patients and evaluating them, what do you think is most important to counsel our patients about who we are treating for neuropathic pain?

Dr Backonja: Number one: by getting good history and exam. Well, really in the coming to specific diagnosis is huge relief to the patients who thinks many themselves that they're just going nuts are crazy because nobody else understands these symptoms. So, validation in terms they have a real problem. Second important step is that for the most patients, there is probably reasonable degree of therapeutic interventions that can lead to relief of pain. And also, with applying the integrative approaches with complementary medicine is that patients are given tools to deal with what is otherwise underlying problem. Those two steps make a huge difference. 

Dr Nevel: Absolutely. What's the most challenging aspect about managing patients with peripheral neuropathic pain?

Dr Backonja: Actually, there are a couple. Number one thus far: we do not have a cure for any other neuropathies or painful neuropathies. So that's one of the big disappointing things one would need to communicate to the patient. The second challenge is actually the therapies that actually for neuropathic pain. There's a half a dozen- yeah, half a dozen FDA approved treatment. One thing that's interesting characteristic that all of them prove proven efficacy in clinical trials. If you scratch the surface, you find out that only 40% of patients obtain 30% pain relief. So, it's a rare patient that gets 100% pain relief, and even those, too, get what we call clinically significant, and then in studies, basically significant benefit. It's only partial penalty. But for the most those who do get the benefit, pain goes down probably enough for them to get some a semblance of normality in terms of having some control over the symptoms and their function. It's then the third challenge is really working through those available therapies to find what works for individual patients because we're not at the point yet where for example, other fields like oncology, you can quickly through the means of biomedical and other evaluation come to the patient specific therapy. So, at this point in time you're far from that. What we end up doing with when it comes to management for painful neuropathies is a trial. Sometimes patients say, well, trial and error. I would say, well, it's a treatment trials. We try one thing at a time, assess the risks and benefits and then there was many treatments that carry the benefit. If you carry it on when once, when they don't or if there's adverse events, side effects, we discontinue them. And then most of the patients end up with a combination of pharmacological and now pharmacological treatments and most of them can get some semblance of symptoms control.

Dr Nevel: I really appreciate your point on preparing our patients and you know, expectations and things like that and working with them and looking for things that may help. But also having an understanding that the likelihood of complete pain relief is maybe not a super high chance of complete pain relief. 

Dr Backonja: But if you're going back to the kind of preparing patients, it's a good to acknowledge or give a chance to express themselves because many times they patients are confused because they have symptoms that are confusing to them. And so just to have them express it. And for example, my alma mater, we developed the color paint drawing where the different sensory qualities are presented by different colors. And then on the body diagram, patients draw where they have symptoms. And this is probably one of the rare examples where you can literally see a pain because these neurologists can recognize the patterns. You can see the pattern of the motor, right, is multiplex or radiculopathy or the list goes on and on. So, this is one of the kind of tools that's very simple, but gives the patients another way to communicate because lots of times they really have difficulties expressing themselves.

Dr Nevel: Right. So, the opposite of the most challenging, can you share with the listeners what you find the most rewarding about taking care of patients with peripheral neuropathic pain?

Dr Backonja: What is rewarding is that with some work- and again, it's not easy work because it does require multiple visits and multiple assessments and the reassessments, most patients can get control over their symptoms to the point of coming to beginning some of the functional improvement and aspects of quality of life like sleep and work, they are definitely rewarding and most of the time it's fairly obvious. And again, pain management is definitely a team sport where really, it's important to gauge colleagues. Most of the places don't have what I have had when I was in academic institutions, easy access to health psychologist or physical therapist. Most communities do have those specialties. And many patients actually benefit from things that are what's considered a complementary medicine, such as Tai chi or yoga. And actually, in my practice, Tai chi was probably most common prescription for my patients because, as I tell them, there are multiple benefits. Number one: one of the risks of patients, especially prophyl neuropathies and lower extremities, is a loss of proprioception. Again, even those who have a reasonable preserved proprioception over welding, noise of pain actually makes the problem walking the at risk of falling. Actually, Tai chi one gets improvement in balance. There's also medicating component to it. So, mindfulness medication is kind of built in it and that all kind of gives the patients a better control of symptoms. So, some of those interventions are easily accessible in community. So, it's, again, it's a patient education that really takes important part.

Dr Nevel: Yeah. And that Tai chi is maybe one of the answers to the next question that I have for you. But as the clinical director of the Division of Intramural Research at the National Center for Complementary and Integrative Health, I have to ask you, Misha, what sort of integrative and complementary type interventions do you counsel your patients about, maybe beyond Tai chi, and which ones do you think are the most helpful?

Dr Backonja: To clarify, the NIH patients I see are all admitted per protocol. Actually, NIH has the largest research hospitals called clinical NIH Clinical Centre, which has a hospital and clinics. All the patients that come to our program, they come per protocol for the most part.

They come for specific investigations. At the moment, we do not have intramural treatment protocols, although in near future one of my goals is to establish that. The NIH funds- 90% of funding from NIH goes extramurally to academic institutions and other healthcare organizations and so on, and only 10% goes for intermural research. So, what we do is much smaller in scope, much more focused. So, what do we support NCCIH actually support extramurally full range of anything from probiotics, research in microbiome related to health and pain all the way to interventions such as mindfulness meditation? Intramurally, once when patients come for protocol, we evaluated and it's unavoidable to be a question. So, what do we do now? What recommendations do we make? Again, we don't- with the present time, we have treatment protocols and then, most of the time, what I can do is provide recommendations to the patients when they go back to the treating community, to the treating providers. It's usually a fairly comprehensive list including pharmacological and non-pharmacological accommodations for those who have had experience with pharmacology. Sometimes I can just say yes, continue or change or whatever. But then when it comes to additional complementary accommodations, they always provide information. For example, why do I recommend Tai chi? Or, what's the benefit of yoga and why would one want to try to learn trying to behavioral therapy or mindfulness meditation? What's the benefit of turmeric and some other components of what's called anti-inflammatory diet and what's the rationale behind all of that? So rather than just giving a list of recommendations and leaving it that, I try to engage patients in terms of having to understand why something is recommended, whether the fits with their expectations and what fits with their lifestyle and so on.

Dr Nevel: Yeah. So, what's coming up, what's next in painful peripheral neuropathy? What do you think is exciting? Where do you foresee some breakthroughs in this field?

Dr Backonja: Probably what will make the most difference is application of some of the really molecular biology tools that are being applied to peripheral neuropathy. So hopefully one of these days you'll have a cure for neuropathy and pain and anything would come to that will be probably interaction between a nervous system and an immune system, in particular neuroinflammation. That's kind of my bias. They're probably that's- well, the answer will be, but many painful neuropathies - actually every painful neuropathy, because they come from, as a result, specific pathologies - are different in a sense of trajectory natural course that will have to be first addressed. And again, depending on the underlying disease and molecular biology of that and genetics of it will determine that. But on the other hand, there are some common denominators, as we talked, when it comes to painful neuropathies, which is drivers of peripheral and central sensitization. And maybe one of these days, we'll find what are those drivers and how to change the system so it does not produce pain and other associated symptoms.

Dr Nevel: So once again, today I've been interviewing Dr Miroslav Misha Backonja, whose article on peripheral neuropathic pain appears in the most recent issue of Continuum on pain management in neurology. Be sure to check out Continuum Audio episodes from this and other issues. And thank you to our listeners for joining us today. And thank you, Misha, so much for talking with me today about your article. I encourage all of the listeners to read it. It was very comprehensive and just really wonderful to read.

Dr Backonja: Thank you. Enjoyed it.

Dr Monteith: This is Dr Teshamae Monteith, associate editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use this link in the episode notes to learn more and subscribe. AAN members, you can get CME for listening to this interview by completing the evaluation at continpub.com/AudioCME. Thank you for listening to Continuum Audio.