Neuropathic Pain Made Simple: What Every Clinician Should Know

Have you ever treated someone with what seemed like a simple musculoskeletal issue? Maybe shoulder pain, foot pain, or low back pain, but things just weren't adding up? The pain felt disproportionate, unpredictable, maybe even burning or zinging. And deep down you wondered, could this be nerve related? But then comes the frustration. You're not quite confident in how to test for nerve involvement beyond the standard sensory strength and reflex checks. So either move on or second guess yourself. And as a result, the patient continues to struggle and they may miss out on the targeted care they actually need. You're not alone. And today we're gonna change that we're. Welcome to the Modern Pain Podcast, where we help you make sense of pain and bring more clarity and confidence to your clinical practice. I'm your host, Mark Kargela, and in this episode we're gonna take a practical, deep dive into neuropathic pain, what it is, how it shows up, and how you can screen for it with confidence even without fancy equipment. You'll learn the true nature of neuropathic pain and how it differs from nociceptive and noci plastic pain. A simple pathway to recognize it in the clinic, and four common mistakes clinicians make that lead to misdiagnosis or mismanagement. Plus I've created a free clinical cheat sheet you can download that walks you through how to screen for small fiber changes at the bedside with just a coin and a paperclip. Grab that now at modern pain care.com/neuropathic or check the link in the show notes. Let's get into today's episode.

This is the Modern Pain Podcast with Mark Kargela. So let's look at a study, and this was back in 2012. It's a study by Keith Smart and his colleagues, and it's still used quite a bit. It was introduced to me in fellowship. There's probably some more papers recently, but I do think this paper is one of the first ones to really lay out some clinical groupings of what do we see in a subjective and a clinical exam that can help somebody who's got neuropathic pain. So let's look at the subjective components first. You might see the patient describing pain as burning, shooting sharp, aching, electric shock, like ants crawling on their skin. Those kind of weird symptoms that don't seem like they line up with maybe a local tissue issue. They might have a history of a nerve injury or mechanical compromise, maybe a compression injury or something like that. They also might have some medical conditions diabetes, diabetic neuropathy, those type of things we should be looking out for in their history as well. They have pain in association with other neurologic symptoms such as the pins and needles, maybe numbness, weakness, things that we commonly see in clinic when we're thinking about possible nerve involvement. The pain would be referred in a dermatome and cutaneous distribution. So this is again where we need to know nerve root distributions, peripheral nerve distribution, just so we can understand where maybe these pains are distributing in something that would be suspicious for a nerve versus, Hey, this is a local tissue issue. I. These symptoms, patients will often say they're not really responding well to NSAIDs, such as, ibuprofen, those type of things. The things that we would expect if it was a primary inflammatory nociceptive issue that would ideally be helping, but we're hearing in the history as we're speaking to these folks, that it isn't really helping much. You might hear that the patient, if the physician may, that maybe referred them or who's also been managing them, maybe put them on duloxetine or Pregabalin might be seeing that they're having some improvements with that, which again, at that point, probably neuropathic pain has already been diagnosed. You're gonna often see with these people pain of high severity and irritability. So that a lot of times you gotta be very cautious as we examine these folks that we're not getting significantly aggressive with our physical examinations, just because often these symptoms don't take much to provoke and they can often be a little bit of a difficult thing to settle. So as you're working and having people move or maybe doing things with exercise, you're instructing those folks, Hey, let me know when we're just getting to the edge of things. I don't want you to push into symptoms today. I want you just to go to the edge to where you're just maybe nudging into some things. Next we're gonna see maybe a mechanical pattern to aggravating and easing factors that involves things that load or compress nerve roots. So anything that kind of puts compression into maybe the nerve trunk of your sciatic digging into the back of your leg. Sometimes seats will do that for some people who have neuropathic pain in that distribution, I. You also might hear for the upper extremity neuropathic pain, anything reaching behind or reaching where they're put in tension. Oftentimes we mistake that painful arc, which we'll talk about later as a local tissue issue at the shoulder when we also know the painful arc is right in the realm of where Neurodynamic mechanical loading of that brachial plexus is probably at its peak. You also see pain in association with other dysesthesia. You get this crawling, heaviness, electrical sensations that again, just don't add up as a local tissue mechanical nociceptive issue. And then the one thing that I would also recommend you is like asking patients, can you just get pain just sitting there doing nothing like at rest, where you'll get these sudden bursts of pain. This is often a characteristic of neuropathic pain where patients can just say, I can just be laying down. I can be doing nothing. I will get these random, just pretty sharp, nasty jolts of pain that go into my leg or my arm, depending again where the patient's pain is located. So let's look at the clinical examination with these folks as well to see what kind of things we might see clinically with them. So with these patients, pain symptom provocation with mechanical movement tests, so again, our active and passive neurodynamic testing, straight leg raise, slump testing. You do your active upper limb nerve, you do your upper limb neurodynamic tests your median and your radial, your ulnar nerve testing. You'll also get pain and symptom provocation with palpation of relevant nerve tissues, and this is probably one area I see clinicians make a big mistake as they start palpating, down the areas of pain and they disassociate or misdiagnose these tender points as something that's a problem locally in the tissue, like a trigger point or something like that when this is probably the materializing of hypersensitivity in the distribution of the nerves. Ensure muscles might get hypersensitive and maybe increase their tone when the nerve that's supplying them is highly sensitive. We'll see positive neurologic findings. Decreased reflexes, sensation or muscle power in a dermatome or myoma distribution. We might also see antalgic posturing of the affected limb or body part where the patient's trying to find positions where they have to externally rotate their lower extremity to put some maybe mechanical slacking on the nerve. Or they might say the old shoulder abduction sign where somebody walks in your clinic or you might hear a patient say, when I rest my hand in my head, it's the only source of relief I get. Again, the thought with that is there might be some mechanical. Slacking or decreasing the mechanical load on that nerve. Then lastly, you might see positive findings of hyperalgesia, primary or secondary, or even allodynia where just sensations or stimuli that should be, light touch or things that should not have pain are hyper sensitive and you're getting pain with even light touch or things that shouldn't be that sensitive. This is a pathway that was developed by Annina Schmid and her colleagues as part of a neuropathic, pain special interest group for the International Associations for the Study of pain, where we can help clinicians kind of work through a pathway to help us determine, hey, is neuropathic pain present or not in this patient or this clinical situation. So obviously we're gonna have pain and then we talked about our history is gonna give us some clues that, hey, this might be present or not. You're gonna then move on to the examination, do some of the things that we'll talk about you're gonna do a sensory exam, you're gonna do mechanical loads to nerves. You can do palpatory assessments, you're gonna do all the things that we know how to do clinically to determine, you might look at spinal related movements, especially if it's spinal related leg pain, which was a context of this study where you're gonna have movements that might influence spinal positioning or things that if there is neuropathic pain being generated, possibly from a spinal condition, that we might have some altering of symptoms based on spinal positioning. And then complimentary tests are mainly for folks more in the physician realm where you're gonna see cts, MRIs, skin biopsies, other tests that are probably tests outside of your basic clinical practice in physical therapy. So I wanted to get into four issues, four mistakes. Some of these I've made. The one at the end, definitely I've made. Let's talk about some of the issues that we all face as clinicians or some of the mistakes we've made. I've made them all. You may be making them, or you're making them currently. That's why we're having this video. So hopefully these will help you out. First one, not thoroughly questioning out symptoms. So what does that mean when we're not thoroughly questioning out symptoms? Well, one, you need to not just'cause let's just say we have a patient with lateral elbow pain on the left and we just tunnel vision in. We question, we do all the palpating.'cause again, if there's nerve issues, you're gonna get tenderness at the lateral elbow, which if we're really anchored on this being a lateral elbow issue and a lateral epycondylgia you're gonna start digging and finding sensitivity. And, oop, my diagnosis is made. This is just a lateral epicondylgia, nociceptive dominant. But we want to question out like, where are these symptoms distributing? And I tell students that I mentor and clinicians I mentor, that you need to question out from the spine all the way down to the distal extremity through that area of symptoms. So any current or past symptoms in your neck or. Into your top of your shoulder, any symptoms in your upper arm, any symptoms in your lower arm, any numbness, tingling. We're gonna question all those things from the whole distribution of where a nerve could be. And it's just good common practice to do that where you're gonna ask these questions to understand if the patient says, yeah, I got this lateral elbow pain, I also have this pain on the outside of my wrist, and I got this pain on top of my shoulder. And recognize patients sometimes don't offer this information. They don't understand that there's a connection to this thing. They just, their pain may be worse at the elbow and that's where they find that they need to discuss with you. So they don't draw it on a body chart. They don't discuss it in clinic'cause they see that as separate issues. But us as a wise clinician or as somebody who understands neuropathic pain, you're gonna start hopefully connecting the dots that, hey, they got lateral wrist pain, lateral elbow pain, and neck pain. That sure lines up with a possible neuropathic pain condition. Next mistaking positive clinical exam findings is a local tissue issue. I've already alluded to this a little bit, but this is basically where the patient has tenderness throughout all sorts of areas. When you palpate it could be in the shoulder with a shoulder pain,'cause a lot of those nerve trunks truck right through the shoulder. So we might be mistaking, maybe rotator cuff or tendinopathy or, tendon type pathologies. You might be palpating along the course of the median nerve and the bicep or in the front of the elbow and you're thinking, okay, this is bicipital tendonitis. I. The big moral of that story is you need to palpate possibly throughout. If you're not sure if this is a local issue or not, then you would expect the tenderness to stay pretty local and focus to a tissue and you shouldn't see it tracing. And that's where you need to know where your nerve trunks distribute throughout the body, where you can have some access to'em. Obviously in the satic nerve, you can palpate down the trunks as it warms alongside, the hamstrings. You can, if you're really sadistic, you can do the bowring test where you're strumming the back of the knee in Slack, where you're putting a little twang on the satic nerve. Again, I wouldn't recommend doing that. If somebody's got a hot satic nerve, they're not gonna like you so much. But you need to make sure that when you're assessing for palpatory tenderness, that your at least thinking process needs to include that there's possibly that this sensitivity could be a widespread sensitivity of a nerve. Then it just expand your palpation. Maybe it is just locating itself there. It's not really distributing further. It's very focused and localized where we can be maybe more. Suspicious that it's nociceptive or a local tissue issue versus, Hey, I palpate and man, it's sensitive here, but I can palpate all the way down into some nerve distributions and palpate all the way up. And man, it is hypersensitive and tender. And as I mentioned earlier too, we can get clinicians who get anchored into a. Treating these local downstream sensitive issues where they got things that get characterized as trigger points or things where I'm poking needles, I'm driving my knuckle, I'm doing scraping techniques, and granted, those actually can probably impact neuropathic pain. But if we're working with somebody, for instance, who's got a herniated disc at the neck and downstream is where all the sensitivity and pain is, and you're just focusing downstream with all these peripheral techniques. You might manage their pain that and take a while as maybe the natural history of the thing going on in their neck does its thing. And over time, that quiets down and the pain kind of gets in a good spot. But maybe you're better off. Focusing yourself at the issue the upstream issue of May, the herniated disc. So I think jumping into peripheral neuromodulatory techniques where you're scraping, poking needles, driving your hand, doing soft tissues. Now those might be part, even if you do understand that there's a proximal issue in the neck or the spine, that maybe you still use those techniques as a neuromodulatory thing, where again, we're putting it in a narrative where we're not fixing, people aren't faulty, we're just simply trying to decrease some of the sensitivity as their body does what bodies do, and that's, natural history recovery provided. We're not getting in the way of it. Next, using incorrect terminology, and this is one I've definitely been guilty with myself. so let's talk about what that terminology is. So, neuropathic pain is defined by the International Association for the Study of Pain. Neuropathic pain is pain that arises as a direct consequence of a lesion or diseases affecting the somatosensory system. So this is a helpful table that's been proposed, and this is a, again, coming out of Annina Schmid's work and her colleagues where this is something that I would immediately call everything a radiculopathy and not really understood those terms as I was applying them in my own practice. I work with a lot of osteopaths and they throw somatic referred pain, not pretty much majority of everything. I joke, of course, they're very good and they do some things, but the somatic referred thing gets thrown around quite a bit. So somatic referred. Pain really looks at the source of the pain being noxious stimulation of nerve endings in somatic structures, discs, facet joints or muscles, tendons, ligaments. And the pain is often a aching, gnawing pressure type pain. And it's referred it's not necessarily distributed in any specific. Anatomically plausible, neuropathic, or, nerve distribution, be it peripheral, be it nerve root. So it, but it's just this kinda general distribution in radiation and there's been plenty of studies that have shown facet distributions and distributions of discogenic pain when maybe possibly nerves aren't being affected. Of course, there's criticisms. Are we ever gonna be able to perfectly isolate a pain to a specific tissue? I get it. There are times where tissues can have the primary referring issue from and be maybe the primary. Target we need to be looking at as we're trying to help somebody with pain and then radicular pain. And I think radicular pain we often mistake is radiculopathy and radicular pain can be hyperexcitability and discharges of the dorsal horn or dorsal root ganglion caused by, inflammation, ischemia or mechanical deformation if radicular pain coexists with radiculopathy. So this can have a radiculopathy, but. If we go to the radiculopathy finding, this is with hard neurologic signs. We're seeing sensory loss, we're seeing myoma loss, we're seeing reflex loss. There's concrete hard neuro signs that accompany radiculopathy. You can have positive nerve testing, nerve sensitivity testing, be it neurodynamics, palpatory tests and all these different things in a radicular pain. But it's probably radicular if you're not seeing any significant hard neurologic signs in your neurologic examination. So we want to have a good neurologic exam that'll help us differentiate these. So again, being able to differentiate your terminology between somatic referred. Radicular pain and radiculopathy. And again, radicular pain and radiculopathy are often gonna be some of those things where we're thinking there's neuropathic pain involved and we can do some of those exam things that we spoke about earlier. I. And lastly, not testing small fiber dysfunction. So, and this is one that I've been guilty of, it wasn't until our podcast last week, and I'm gonna give you some check out the card I'll be able to direct you to that episode and it'll talk to some of the issues we have. And in that episode, it was more from whiplash associated Disorder type two, which was previously thought to be primarily a musculoskeletal only issue. And why, looking at small fiber dysfunction might be helpful for those folks. So one simple, one pin prick would be taking this super fancy piece of equipment, which is a paperclip. You got a dull side, you got a sharp side, and then you can just go down in nerve distributions and say, have a patient, maybe you have'em close their eyes so they ain't cheating, sharper, dull, sharper, dull, sharper, dull. And you're just having that patient go throughout that nerve root distribution. So that's a very fancy piece of equipment. And then lastly, you can have coins. And this is one a Nina had described in her work where we use a coin to determine if the person's got some thermal detection threshold issues. So you'd have one of these in your pocket that would ideally bring a coin up to body temperature. And then you'd have a coin that maybe is sitting out at room temperature, which would be cool or cold.

So let's look at our fancy cold detection procedure and just gonna go over some of the procedures of that to help determine if there's some cold thermal difficulties. So we're gonna place the room temperature coin on the lateral arm. Remember, the room temperature coin is the one that should be perceived as cooler. We're gonna palpate it on the lateral arm, then we're gonna immediately place it on the Palmer tip of the index finger. And what we'll do with that is, does this feel the same, colder or warmer than your upper arm? And the interpretation of this is basically if the fingertip feels warmer or less cold, then this might be a possible cold detection deficit. Now if we look at a warm detection procedure, you may have guessed this, you're gonna grab the one outta your pocket, that's body temperature that should be warmed, and you're gonna place that warm coin on the lateral upper arm. Again, you could maybe do this in the thigh and then into the distal toes for somebody with lower extremity. Then you're gonna place it on the Palmer Index fingertip and ask the patient, does this feel the same, colder or warmer than your upper extremity? And the interpretation of this would be if the fingertip feels colder or less warm, possible warm detection deficit. So our clinical tip with this one would be, try not to use. Leading language or things that are, is it better? Is it worse? Is it colder? Is it warmer? You just let the patient, you give'em some choices and they choose. Versus you lead'em to a choice. Is this colder? Is this warmer? Because, and patients sometimes can be people pleasers and maybe give you answers you they think you want to hear versus maybe a more true objective thing. And remember too, the lateral upper arm just acts as a control site. It's less commonly affected with a neuropathy, so it's something that can be something that often we wouldn't expect to have neuropathy, but in the case where we might have a patient where we're thinking whatever reason or small fiber issue might be more than just, than the distal extremities, then obviously we'd want to try to find a different control site for that person. So hopefully this episode helped y'all. Again, if you're interested, make sure you download the clinical cheat sheet in the show notes, Or go to modern pain care.com/neuropathic and you can download it there. Hopefully it's helpful for you to the clinic. I'd also love to know if this episode was helpful for you. I want to try to create content that's helpful for you on the clinic. I know I've had questions from folks that I've mentored in the past about this, so hopefully it's valuable to you. Drop a comment in the comments below, let me know what you thought. And I'd love to hear if you could share some of your tips that you might have found in your work with folks with Neuropathic Pain. We're gonna leave it there this week. We'll talk to you all next week.

This has been another episode of The Modern Pain Podcast with Dr. Mark Kargela. Join us next time as we continue our journey to help change the story around pain. For more information on the show, visit modern pain care.com. This podcast is for educational and informational purposes only. It is not a substitute for medical advice or treatment. Please consult a licensed professional for your specific medical needs, changing the story around pain. This is the Modern Pain Podcast.