How pain is processed in the brain

You’re listening to Chronic Insights, the podcast for people who have medical histories which are longer and more complicated than a Game of Thrones novel. Hi, I’m James Allen, your chronic illness companion.

How’s your pain today? Mine’s fairly low, maybe a 3 out of 10 right now. A lot better than a few days ago, when I was really unwell. I thought I had covid, but tested negative, so, I dunno. The worst part was, and this probably goes for you too if you have a chronic illness: it’s not just the cold or virus or whatever it was, it’s the interaction it has on all your other illnesses that makes it, frustrating. Because I stopped taking my medication that I take for my AS for a couple of days while I was really unwell, so I wasn’t taking the anti-inflammatories which helps my joint pain, and I didn’t take the methotrexate which I was supposed to take that day. Luckily I wasn’t due to take my biologic injection, which I think is, this weekend. So I recovered quite quickly from whatever virus or whatever I had, but the next few days I then had to recover from the fact that my AS was worse, because I hadn’t taken my meds!

You know what it’s like. Thanks for being here to listen, because I don’t really have anyone else to talk to who knows what it’s like having a chronic illness. So thank you.

Anyway, today’s episode will pick up from last week’s episode where we were learning about the neuroscience of pain. I’m not sure how many episodes it will take to cover it all, because I don’t really plan these episodes, I just go for however long I can before I start to lose steam, before I need to have a rest, or get up and move, or before the aches and pains start to build and I get too much brain fog and I start to lose track of what I’m saying. Again, you know what it’s like - we can’t just blast through things like most people, we have to pace ourselves, do things in smaller - chunks - a bit at a time - so, I know you understand why I don’t just do it all in one massive 3 hour long podcast.

So, I dunno how much we’ll cover today, but - I find it fascinating stuff, and I think it helps - like we saw last week, a lot of people find it easier to live with chronic pain if they understand why it’s happening and how it works. I think I’ve got quite a good analogy for it - you know if there’s some sound, some repetitive sound, maybe outside your home somewhere - and you don’t know what it is, or who’s making it, or why? That can be really annoying, and - stressful, especially if you’re trying to concentrate on something, or if you’re trying to relax. It’s like, what is that? What the hell is going on? But if you find out what it is - maybe it’s the local council clearing some drains, or digging a hole to fix a burst water pipe - when you know what it is, and why it’s happening, I think - it becomes much less annoying. Because you know, okay, it’s annoying, but at least there’s a reason for it happening that makes sense.

Well I think learning about the science behind pain is basically that. By understanding why it’s happening, it can become - I dunno, less scary? Less like it’s just some unfathomable evil force in your body, and more of a simple mechanism that you can see and understand.

So just before we get to that, I wanted to share this wonderful email I got from someone who has been using the Chronic Insights symptom diary app. They had got in contact a while ago to ask if the app could be changed so that when you’re putting in a number for a symptom like pain using the number dial, you could ask it to snap to whole numbers. And they got in contact this week, and kindly allowed me to share this email with you:

“Hi!! We chatted a while back about an app request I had, which was snapping to whole numbers for pain. I stopped using chronic insights for a while for external reasons and today I came back, and woah! It's got a great UI, great features, and I just wanted to thank you for adding the snap to whole numbers thing! I had forgotten about it and was just really happy to see it there. I flicked between different apps for a while but there weren't any good everything apps for health. Came back to chronic insights and for sure was not disappointed. Staying and paying, thank you so much for what you do.”

So, thank you so much for sharing that. And yeah, I think this is one of the great things about my symptom diary app - it’s not just another app made by some big company, made by developers who aren’t disabled and are just guessing what a symptom diary app should be and should look like, which is pushed out and never changes. I work on this app all the time, when I’m well enough. For years now. Because it’s my passion. It’s the one thing that I’ve done that I’m really proud of, and it’s become my main thing in life, so - if you’re using the app and there’s anything you want to be added, a feature, a different UI, whatever - just let me know. I can’t promise that it will be added, you know, it has to be feasible, and it can’t be too complex or confusing - like, I had a suggestion for the medication feature where you could record that you had taken part of a dose, like half a tablet of something, and had the rest later, and - it’s interesting, but I’m not sure yet how I can add that feature without it being too confusing or hard to use.

So anyway, thanks to everyone who has sent in feature suggestions, please - keep them coming. You can email me at james@chronicinsights.com or DM me on Instagram.

So. The science of pain. Last week we talked about how normal pain works - the useful kind of pain, which lets you know that your body has an injury, starting at the nociceptor, the type of sensory neuron, the long nerve cells in your body that transmit signals. One really cool thing I didn’t mention last week is how long these nerve cells are. Because when we think about cells in the human body, we often think of these teeny, tiny little things that you can’t see without a microscope. Well a sensory nerve cell, a neuron, can be - a metre in length! A metre! One cell. That’s amazing! These really long ones are in your legs, so they can carry a signal from your toes, all the way up to the base of your spine, in one go. Awesome.

So the nociceptor is a type of sensory neuron which detects injury, and there are different kinds which are specialised at sensing different things. Some detect extreme heat, some extreme pressure or stretching, and others detect certain chemicals, like ones which are released when we are physically damaged. One of these happens to be capsaicin, the chemical in chilli peppers, which is why when we eat chillis it feels like it’s burning - it’s not actually burning, it’s just that our nocireceptors are interpreting it as - extreme heat. I had one last week, it was a good thing I tried it first before slicing it up and putting it in my dinner - just, the tiniest, tiniest bit, I tried and it blew my face off, it was just - well, the reason is was packed with capsaicin, and my nocireceptors in my mouth, the instant it came into contact, bang! They activated.

So when nocireceptors activate, they send an electrical impulse all the way up the length of that nerve cell first to the spinal cord, and then up the spine to the brain. Except, that’s not the whole story. It might not actually get to the brain, because there will usually be several neurons involved in passing the signal up to the brain, and at the junction between neurons is - the synapse. A little gap. And waiting at the gap are neuroreceptors, chemicals which can jump into the gap and may, or may not, continue the signal, depending on if there are enough of them, and whether there are any counteracting neurotransmitters which can actively stop the signal.

And then, even if it gets transmitted all the way to the brain, into the junction box called the thalamus, and then to the cerebral cortex, the outer layer at the top of the brain, there are more factors involved. Memory. Emotional state. Alertness. Things that have happened previously, can all affect how that signal is actually processed and what we ultimately experience.

So that's the main pain pathway, from pain sensor to the brain. And normally, pain like this, acute pain which is short lived and happens because of an injury, this is extremely helpful to us. But in chronic pain, something goes wrong. And because the nervous system is so complex, there are a lot of things which can go wrong. It’s like Scotty said in Star Trek: “the more complicated they make the plumbing, the easier it is to stuff up the drains.”

For example, when you get an injury and the nocireceptors do their normal job of signalling that something is wrong, sometimes the body actually produces more receptors at that spot, sometimes temperature or some of those touch sensors we already talked about, and they can actually start triggering the nocireceptors, and this explains why sometimes chronic pain can linger long after the injury has healed - which is sometimes called post-traumatic pain, or complex regional pain syndrome.

And remember those synapses, the junctions which pass signals from one neuron to the next? Well, the more signals go across those synapses, the better they become at passing on more signals, because the synapse will produce more neurotransmitter to jump into that gap and carry the signal on.

And when these signals get to the cortex in the brain, instead of just one small part of the brain getting activated, if there is repeated stimulation, eventually more areas can become activated, and they sort of start reinforcing each other, like getting feedback on a mic, so that the brain itself actually changes so that more of it just becomes good at processing pain.

In a way, it's like muscle memory. If you start learning the piano, it's really really hard just to play a few notes. You have to really think about them every time. After years of practice, it can actually become almost subconscious - you can just play, without really thinking about the individual movements anymore. That's because the neurons for doing those specific movements with your fingers have become really good over time at sending those signals.

This can sometimes happen with chronic pain. It's called "central sensitisation". If we experience pain for a long period of time, the brain actually becomes more sensitive to pain.

So that sucks, right? I don't know about you, but some of these facts are, like, so "you're the reason why"! But, you know, at least it starts to make sense, right? It's not that our bodies hate us, it's that our bodies are just doing what they've evolved to do. It's just that, it's getting it wrong for some reason. I prefer knowing why, and understanding it - it helps me be less angry, or frustrated, and a bit more in control of my chronic pain. It helps me rationalise it, to understand it.

And maybe, just maybe, we can learn some things which can really help us manage our own pain. Did you know that the body actually has mechanisms to reduce pain? Did you know that the body produces it’s own opioids? I was really amazed when I learned that, I had no idea. And those inhibitory neurotransmitters - did you know that as well as pain pathways going up the neuron to the brain, there are also pathways going from the brain back down to the body, which can act to reduce and dampen down pain? So, we can also learn about why certain things might affect pain, and more importantly understand them in the context of our own unique circumstances, our own health conditions and our environments, our own bodies, and effectively what we’re doing here is becoming experts of our bodies.

I like that. I hope you do too. Let me know what you think - james@chronicinsights.com.

Here’s another interesting thing about pain, which can give us more insight into how it works. You know in a movie, if there’s been a gun fight, you know, Keanu Reeves has been blasting some bad guys or whatever. And the good guys are celebrating, and then someone realises they’ve been shot and they didn’t realise? This is real thing that can happen. It's documented. So what's going on there?

Well, being in a gun fight is probably the most stressful environment there is, right? Alertness is through the roof, you literally might die at any minute, and because of this, the biochemistry in the brain changes into a radically different state, because of things like adrenaline, which is a very powerful hormone. It’s produced by a part of our nervous system called the "sympathetic" nervous system - which is a bit of a weird name, sympathy can mean ‘working together’, working ‘in sympathy’, so the sympathetic nervous system is lots of parts of the nervous system working as one.

Basically it's the part of our nervous system which makes us more alert and ready for action. The reason someone can get shot and not feel pain is because at that moment, the brain is interpreting things differently, because of the highly stressful life-and-death situation it's in. So this just helps to reinforce this point, that all pain is how the brain interprets signals from the body. And there are similar documented stories from sports, where maybe it's a cup final, everything is on the line, and a player can actually fracture a bone, something that’s normally immediately very painful, and not realise until after the game when the adrenaline stops flowing.

And actually from an evolutionary perspective, this makes sense, right? If we're in that kind of highly stressful situation, it's actually better for our survival if we're not distracted by pain at that moment, when we might need to be thinking more about - how do I get away from this tiger which has huge teeth and is looking at me like I’m the last chicken in the coup.

Another interesting thing is, have you ever noticed that when you stub your toe, there's a few moments there where it doesn't hurt? Because we know from last week that nerves can transmit signals at 100 meters a second, so we should feel it immediately, right? And sometimes when you injure yourself, let's say your arm, and you know something has happened, but it's not until you look at it and realise that you've cut yourself that the pain kicks in?

What this tells us is that the brain is not just using signals from your nerves, but is actually also using what you see (like, what was that - oh my god, ive been cut!), and what you hear (like your toe banging off a table leg - when you hear that bang you know it’s gonna hurt!). What you're thinking (like I'm having a really bad day, or - oh my that tiger looks hungry), your emotional state (you’re in a world cup final!), it uses all these things to help to figure out how to interpret the pain.

So I don't know about you, but as someone who lives with chronic pain every day, I find this fascinating, and illuminating. It makes me want to learn more about what's going on in the brain, because I feel like I have more power over it, instead of it having all the power over me, because I understand it. I think it can - improve our relationship with pain.

What do you think? I hope this helps. I’m at that point now where the aching in my hips and my back is starting to - fog my brain, so - I need to stop for this week. But there’s some good stuff coming up - next week I’ll talk about the para-sympathetic nervous system, which is basically the opposite of the fight-or-fight mechanism. It’s the part of our nervous system which can calm us down, which wakes up when we meditate, when we slow our breathing, when we relax, when we touch and cuddle and kiss, when we do the things that make us happy. It can have a profound effect on chronic pain, how we experience it. And we’ll talk about other things which can dampen down chronic pain, like - did you know that the body creates it’s own opioids? I didn’t know that, I find that fascinating - I thought opioids were just things you get in painkillers.

So, that will be next week. I’ll end this episode as usual with a poem I wrote about chronic pain. It’s one of the poems from my upcoming poetry book. It’s called Prism, and it’s one of my favourites.

sometimes when the pain is just right
when it catches the angle of the light
just so

poems tumble out of my head

but I am too exhausted to catch them
in the notebook I keep in my pocket
so they fall to the ground

and I watch with morbid fascination
as they slowly turn to dust
unwritten

until you come to gather me up
to stroke my head and kiss my cheek

and I smile as I watch
the dust float away

glinting
in the light

Okay, thanks for being here, my spoonie friend, my companion in chronic illness. Just remember that we’re in this together, and you’re not alone. See you next time. Love you. Bye Bye.