[Physio Explained] Understanding the complexities of chronic pain with Dr Rocco Cavaleri

In this episode with Dr Rocco Cavaleri, we explore chronic pain and all of it’s complexities. We discuss:

·   What is Central sensitisation?

·   What is the difference between acute and chronic pain

·   Can we treat chronic pain?

·   Role of the nervous system in chronic pain

·   Clinical recommendations for treating chronic pain patients

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Dr Rocco Cavaleri is a Senior Lecturer in the Physiotherapy department at Western Sydney University. Rocco completed his PhD in 2022 and also holds a B Health Science (Hons I)/ M Physiotherapy from Western Sydney. He is also an adjunct assistant professor at USC and an honorary research fellow at Queensland University of Technology. Prior to commencing his PhD, he worked clinically as a physiotherapist across both acute and private practice contexts. Rocco currently leads the Brain Stimulation and Rehabilitation (BrainStAR) lab.  

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Transcript

SPEAKER_01 0:05

Make sure you have a multidisciplinary team. Try and get ahead of it as a way to summarize it. Like try and really effectively screen and target acute pain before it becomes chronic. Explain properly, like with the proper physiology, with the proper anatomy, what's going on to your patient so they feel comfortable getting a bit of that graded exposure? Give them that sense of control. And as part of that, give them that predictability and give that give their nervous system that predictability to try and get it out of that hypersensitive kind of chaotic state.

SPEAKER_02 0:38

What actually is central sensitization? And are we sometimes overusing the term in clinical practice? Can we truly treat the brain when managing chronic pain? Or is that an oversimplification? And what does this mean for how we assess, communicate and treat our patients day to day? On today's episode, we're joined by Dr. Rocco Cavalleri. Rocco is the director of the Brainstar Lab at Western Sydney University and a senior lecturer in the physiotherapy department. He is also a Fulbright scholar, having completed his program at the Division of Physical Therapy at the University of Southern California. Before his research career, Rocco worked clinically as a physiotherapist across both acute and private practice settings. Today we explore central sensitization, brain-targeted approaches to pain, and what all this means for clinicians working with persistent pain. You're going to love this episode. It's packed with clinical insight and practical takeaways. I'm Sarah Yule, and this is Physio Explained. Well, welcome to you, Rocco. Thanks so much for joining us today.

SPEAKER_01 1:41

Thanks for having me.

SPEAKER_02 1:42

So let's dive straight into it. What is central sensitization and how does it relate to chronic pain?

SPEAKER_01 1:49

Yeah, absolutely. So to really unpack and understand central sensitization, it's helpful to step back a little bit and just differentiate between acute and chronic pain. Most people would know that acute pain is that early beneficial protective physiological response, right? You reach out, you touch a stove, it's hot. So you withdraw your hand, so you know not to touch it again. And that's a necessary protective mechanism that's kept us alive for thousands of years, right? But in some people, that initial pain persists and it might persist well beyond you what you would expect. And that's what we start to label as chronic pain. So chronic pain is usually pain that persists beyond that expected tissue healing time or beyond three months, and it's no longer at that stage beneficial, it's no longer protective, and it can actually be quite harmful. So that's the stage we're really talking about when central sensitization comes into play. And the way I've had, or the way I like to explain central sensitization is even though there's quite complex neurophysiological mechanisms going on, breaking it down to really simple terms that a patient can understand, I think, is really helpful. So in a cute or with the nervous system, it's helpful to think of it like someone playing the guitar. You know, so they're playing the guitar, the sound sounds nice and sweet, they can play melodiously, everything's humming along nicely. And occasionally they may strum the strings really hard and you get this loud distortion, but it doesn't really last long. And it's kind of what you expect. You saw a big strum, so you heard a loud noise. That's kind of how acute pain works. You know, everything's in proportional or at least somewhat associated with the tissue damage that's occurring. In chronic pain, it's like someone's come along and cranked that guitar amp up to 11, right? Now, even when the person's trying to play sweetly, play softly, you're hearing loud, raucous, distorted sounds. It's out of proportion with what they're playing. And that really is the core of what central sensitization is. It's this upregulation of the nervous system, this hypersensitivity. You start getting painful responses to stimuli that were never painful in the first place. You start getting pain beyond that original site of injury. You might get bilateral pain. So it's yeah, it's really that hypersensitivity, that upregulation of the nervous system, which is quite distressing, quite damaging for people who are experiencing chronic pain.

SPEAKER_02 4:17

That's a fantastic analogy for it. I've not heard that guitar analogy before. Oh, cool. Always nice to have another analogy in the toolkit. And so in terms of in terms of treating chronic pain, can we target the pr the brain directly to treat chronic pain?

SPEAKER_01 4:35

Yeah, it's it's an interesting one, isn't it? Like we're saying, you know, the nervous system, the brain are really the the central hub, right? That's what's driving the pain, that's what's causing pain chronicity. So can we just target the nervous system and make the pain go away? The answer is kind of. So we we've run a series of studies where we've used non-invasive brain stimulation to target the brain and try and treat people living with chronic pain, different chronic pain conditions. We initially started with targeting the motor cortex. It's a nice superficial site, it has a low risk of adverse events, things like seizures following stimulation. But also, we know in pain, people typically change the way they move. And one theory around chronic pain is you have these maladaptive movement patterns after an initial injury. And people who persist with those patterns, you know, we think tend to develop chronic pain. So the logic of targeting the motor cortex was okay, let's see if we can target that, normalize movement patterns, and see if we can treat chronic pain. And with those series of studies, we did show that targeting the motor cortex with these non-invasive brain stimulation techniques does treat chronic pain quite effectively and experimental pain as well. But what was really interesting was when we took a deeper dive and had a look at the motor cortex, it didn't actually change all that much. So even though that's a site we were stimulating, the motor cortex wasn't really reacting the way we we kind of expected. And motor patterns didn't really change all that much either. When we looked at other regions of the brain, we actually found that even though we were stimulating one particular area, multiple areas involved in pain processing were lighting up. So we were seeing changes in the amygdala, seeing changes or activation in the thalamus, somatosensory region, DLPFC. Lots of different areas were kind of being activated, and the motor cortex was acting as a bit of a relay station to these other areas. And that really highlighted to us just how complex chronic pain actually is. You know, you've got areas involved in sensation, motor processing, anxiety, depression, catastrophizing, all these factors that are responding to the treatment. It's really hard to work out what actually promoted the pain relief because there were so many things happening concurrently. So, in terms of whether I see that being integrated into clinical practice, potentially, I don't think it's a panacea because chronic pain is so complex, but I do see things like the non-invasive brain stimulation hopefully acting as a bit of an adjunct. So something that can support, you know, the awesome job we do in targeting chronic pain clinically as physiotherapists, particularly with the advent of home-based brain stimulation. I think that's something that's very exciting, pun intent, not intended, but that's something that's very exciting for me, is the potential short-term reality of people going home and putting on these, you know, these devices and receiving treatment for their chronic pain, non-invasively at home. I think that's a really cool, interesting thing that physiotherapists are kind of primed to do. You know, we're trained in electrotherapeutic modalities. So why not, you know, take that next kind of venture into brain stimulation? The other really interesting thing in terms of the the, I guess, the relationship between brain stimulation and chronic pain and and management is we've also run a series of studies, and other labs have done this as well, identifying, or that have identified these specific markers that seem to predict who is likely to develop chronic pain after an acute injury and who's likely to recover. So I think one really interesting avenue that we're starting to explore now is whether we can really early flag, okay, this person's at risk. Let's give them an intervention targeting targeting the nervous system and see if we can prevent that chronic pain from developing in the first place. So, yeah, what's this space potentially is probably probably the answer to whether we can we can target it. But it's a really exciting kind of avenue.

SPEAKER_02 8:27

I have several questions from that. That research, firstly, sounds incredibly interesting and also sounds like it's perhaps opened more questions than answers, which is the cranial nature of a study. But going to back to the brain stimulation at home, from a practical perspective, what does this actually look like in terms of what you would prescribe to a patient?

SPEAKER_01 8:49

Yeah, absolutely. So we we've just finished running a pretty large clinical trial looking at home-based TDCS, transcranial direct current stimulation. And it's gotten to the point now where it's basically a prefabricated, like an existing head piece that you can pop on to the patient's head, and then they have pre-soaked electrodes that just click into the headset. So it's very, very easy, very intuitive. They pop it on, they hit start, all of the parameters and settings dictated by us behind the scenes remotely. So we do the prescription remotely. Literally the only thing the person interacts with is a button that says on. So they pop it on, press on. And at the moment, well, the protocol we trial was 20 minutes a day for five consecutive days. So that's kind of a standard, you know, five to 10 days, 20 minutes a day, which is not too bad when you consider that, you know, you could do that treatment while you're just sitting at home, chilling, reading a book or watching TV.

SPEAKER_02 9:42

So it's quite a sort of a passive treatment for them, presumably as an adjunct to the wider pain program as well.

SPEAKER_01 9:49

Yeah, exactly. Like we're we're exploring it in the context of because you've got to do it as a study, we're exploring it in isolation at the moment. But the bigger picture is yeah, can we combine it with things like the exercise program or can we combine it with physiotherapy? Because like I said, I think it's more an adjunct treatment than a be all and end-all.

SPEAKER_00 10:05

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SPEAKER_02 10:30

Yeah, fascinating. And so, in terms of clinical takeaways and and practical tips for physios, what do you have in your toolkit? We've already got a great analogy in terms of the guitar.

SPEAKER_01 10:44

Feel free to steal it.

SPEAKER_02 10:46

Noted, it's in the toolkit. What are your clinical takeaways and some tips for physios that are managing those with chronic pain?

SPEAKER_01 10:55

Yeah, definitely. I think one, even, you know, we're talking about the brain simulation research and how complex pain actually is, like neurophysiologically. I think appreciating that complexity in the first place is really useful. You know, understanding that, yes, this person's pain is absolutely real and it's physiologically driven. It's not in their head, it's absolutely real. I think that's really important. And then drawing on, okay, you know, like I said earlier, areas involved in motor control, somatosensory processing, emotion, anxiety, they all play a role. You know, sociocultural factors play a role. All of those influences can kind of contribute to that dialing up of the AMP towards 11, right? That contributes to that sensitivity. So clinically, I think a multidisciplinary approach is essential. We we can, you know, contribute towards the pain relief and the motor adaptation issues by getting people involved who may be able to help with the psychological elements, like a psychologist, getting social workers involved, occupational therapists involved, I think is really necessary and really important because chronic pain is so complex. Even before then, fully appreciating that once you get to the stage of chronic pain, those abnormal or maladaptive changes to the brain have become entrenched. So ideally, you want to start thinking about how you're gonna mitigate or manage chronic pain before pain is even become chronic. So when you've got people coming through the door with acute pain, I think there is a little bit of a temptation to sort of say, oh yeah, you know, paracetamol and, you know, relative rest and you should be right within X amount of time. I don't think that's doing patients the biggest service we possibly could. I think even during the acute stage, as a takeaway, trying to screen and identify who could be at risk of chronic pain development is really important. Obviously, clinically we go through things like yellow flags and trying to identify who might be at risk, but there are actually tools to do that. The start back tool is the one that comes to mind for back pain that actually helps you stratify, you know, who's got a low, moderate, and high risk of chronic pain development. So even during the acute stages, if you're seeing people who are at a high risk of chronic pain development, starting to think, okay, maybe a multi-dysc team is involved here, maybe I do need to get a psychologist involved is a really forward-thinking and important management tool. But if you do get to the stage where the pain is chronic, beyond the multi-dysc team, I think giving the patient credit where credit is due is really important. Explaining to them that yes, you have pain, it is very real, but it doesn't necessarily mean that your tissue is at an imminent threat. You know, the tissue isn't damaged is really important because that can help them regain that sense of control and help you start to introduce things like graded exposure. You know, you start saying to them, yep, look, we're going to introduce you to that little bit of discomfort, that little bit of pain to try and desensitize you or desensitize your nervous system, sorry, is a really useful strategy. And if they understand that, yeah, okay, I'm going to be pushing myself a little bit, but I'm not going to be harming myself, I'm not going to be causing tissue damage, I think that's a really useful tool as well. And then from there, giving them them that sense of autonomy and control, right? Trying to strip away some of these factors that contribute to that dial being turned up to 11. So being very careful with the language we use. And I was guilty of this as well, you know, saying things like, oh, there's bone on bone, or you've slipped a disc, right? That immediately generates threat and makes the person catastrophize and worry justifiably about what you're saying. So being very mindful to explain things accurately, right? Use proper anatomy within what the person understands, and then start to withdraw slowly the hands-on. So maybe early days, it's useful to do some manual therapy. But as the person starts to get that sense of autonomy and that understanding of what's going on, give them more hands-off interventions, a bit of graded exposure, a bit of exercise is, I think, really, really valuable so that they're not relying on you as the clinician, right? Because you want to give them that sense of autonomy and control. Last strategy that I think is often overlooked is that the nervous system really craves predictability, right? So some things that we don't necessarily consider as physiotherapists is the timing of our interventions and our exercise programs around their life. So encouraging them and supporting them to have, you know, a regular sleep schedule, good sleep hygiene, really, really useful, really important. Optimizing your intervention around their work and their workload, having predictable patterns and predictable timing for things like exercise, physiotherapy appointments. It's really little and like little steps, and people don't usually think, okay, I'm going to try and help this person schedule their day. But doing that can actually help, there's lots of literature to suggest that doing that can reduce that sensitivity, reduce that susceptibility to chronic pain development. So that that would kind of be my, I guess, key takeaways, you know, the clinical recommendations, make sure you have a multidisciplinary team, try and get ahead of it is a way to summarize it. Like try and really effectively screen and target acute pain before it becomes chronic. Explain properly, like with the proper physiology, with the proper anatomy, what's going on to your patient so they feel comfortable getting a bit of that graded exposure, give them that sense of control. And as part of that, give them that predictability and give that, give their nervous system that predictability to kind of get it out of that hypersensitive kind of chaotic state.

SPEAKER_02 16:25

Those are some brilliant recommendations. I think, as you say, although it sounds simple, helping someone schedule their day, we underestimate the role of predictability in what it does for our human brains. Like I said, I've got many questions, but highlighting in your answer, you've you've said education is so important. And going back to what you've said, which is using the right anatomy and physiology, knowing the complexity of it, what level of depth do you go into with reference to the nervous system? When we're describing the nervous system to a patient, what level of anatomy and physiology do you dive into with a patient?

SPEAKER_01 17:02

Yeah, it's a good question. It's it's very, very patient-specific. So if I've got someone who may have a bit of a health background or who has a good understanding, obviously you want to develop that understanding and rapport with your patient first. I'll give them what I feel like they can understand and obviously give them opportunity to clarify, ask questions. But I'll never dip into the very, very colloquial slash exaggerated terminology, right? So, like, like I said, the slip the disc or bone on bone, or you know, the this is jutting out. And I and I also won't, what I've seen people do clinically is kind of tiptoe around it or give pretty inaccurate descriptions, you know, like uh this chronic pain is caused by fibrosis or the scar tissue in your nervous system, stuff like that. I don't think is helpful. It can just be a bit confusing. I think, at a minimum, you know, the guitar amplitude kind of thing is a nice analogy. It's very easy for a patient to latch on to. And then it gives you the option to say, you know, yep, your brain and your spinal cord are responsible for controlling these nerves. Your pain is really real. The nerves are actually hyper-responsive, just like the amp in the guitar is, right? So you start to sort of start very simple, something they can latch on to, and then progressively introduce more and more of that education over time. You don't go crazy and start talking about dorsal root ganglions and nerves and all this crazy stuff. But I think giving them a little bit of insight with something that they're familiar with is more useful than just being flippant with it and saying, Yep, your brain is responding differently, or really, really oversimplifying it to the point where it's not meaningful. So it is a bit of a balance. But yeah, I think starting simple, giving them something to latch on to, and then building up their understanding as you get a bit more of an understanding of where they're at is probably the approach to take.

SPEAKER_02 18:48

It's a fantastic answer. Well, thank you so much, Proco. That was really helpful and really insightful, and I think it's given us plenty of clinical takeaways around some practical tips in how we treat chronic pain, whether it's clear, confident communication, building that shared understanding, acknowledging that chronic pain has a high level of complexity and we're avoiding this one size fits all approach.

SPEAKER_01 19:12

Absolutely.

SPEAKER_02 19:13

So thank you so much.

SPEAKER_01 19:14

Thank you so much for having me.

SPEAKER_02 19:15

It was great, really appreciate it.