Chronic Pain: disorder of the nervous system?
Pain. We’ve all experienced it. No one likes it (unless you identify with the characters in Fifty Shades of Grey!), and we generally can’t control it. I meet a lot of patients with chronic pain who emphasise that the pain is all “coming from my disc”, or “caused by the arthritis in my spine”. They often point with great conviction to scan results – MRIs or CTs – that apparently confirm the source of their pain.
This is not surprising. Many people with chronic pain have been doubted or outright disbelieved. Employers, insurers, doctors, spouses, friends, family (but never physios, of course) – any of these people might have implied that the pain was “all in your head”, or that they were “putting it on”. They might have suggested that the pain “couldn’t be that bad”, and that “it should be better by now”. Such comments can be very damaging to someone’s sense of self, and can create a stigma around chronic pain. Because most people after a back injury don’t go on to develop chronic pain, the suggestion is often that if you do develop chronic pain then it must – somehow – be your fault.
For patients who have experienced all that (and worse, if they’ve been through “independent medical panels” or litigation), it’s perfectly natural to want to prove to everyone that your pain is legitimate, and is coming from a provable injury. For these reasons many chronic pain patients emphasise that their MRI results shows permanent and severe damage. When asked, they often also very strongly believe that all their pain is coming from the particular body part that was injured. These beliefs are quite understandable, but, with our current understanding of the science of pain, they are not quite accurate.
When I tell patients that our brain and spinal cord can modulate, or change, the level of pain depending on the particular situation, many patients are quick to ask, “Are you saying the pain is all in my head?” My answer is an emphatic, “No!” I then point out that, just because pain changes depending on the particular situation, and just because pain does not tell us perfectly about the state of damage to a body part, that doesn’t mean that it’s “all in your head”. The truth is a lot more complicated.
Many people would assume that, when we feel pain, a nerve in a particular area – say, our foot – detects damage, and then sends a signal to our spinal cord and further up to our brain, with pain occurring as a particular part of the brain receives this message. This common-sense view was widely accepted until 1965, when pioneering pain researchers Melzack and Wall came up with their “gate control theory”. They discovered that nerves come down from the brain to the spinal cord, to meet the danger signals (not damage signals) coming up from, in our example, the foot. These descending nerves can either inhibit or excite the upcoming danger signal. That is, they can either block, or amplify, the signal that goes up to the brain, which we ultimately experience as pain.
What decides whether the upcoming signals are dampened down, or instead amplified? Whether we experience more, or less, pain? If we think about the purpose of pain – as a warning that our body is in danger – then it makes sense that upcoming danger signals are dampened down when our brain concludes there is little danger. Importantly for us, when our brain concludes there is a lot of danger, it will let through more signals, and we will feel more pain!
“So you are saying it’s all in my head!” I hear you shout. No! When I say that your brain concludes how much danger you are in, what I mean is that your brain draws on all the available information it can – which includes information coming from the nerves supplying your whole body – but also on your past experiences, the particulars of the situation you are in, your thoughts and beliefs (“this pain is definitely stomach cancer”, compared to, “this pain is from eating too much cake”). What is interesting – and frustrating for pain sufferers – is that even though your brain is doing all this, you do not have direct control over it (just like it can force you to breathe when you hold your breath long enough)! Even if you tell yourself that you are safe, your brain can decide otherwise, which makes you feel more pain. This idea of the way our brain modulates the amount of pain we feel, without any conscious awareness or control on our part, is widely proven. You can probably think of examples where the context in which you were injured had a marked effect on the pain you felt.
It’s not just your brain though. When you’ve had pain for a while, important changes in the spinal cord can occur, which affect the way that danger signals travel up to the brain. What all this means is that when you feel pain, even when you do have a bulging disc, the pain is not simply coming from the disc, with the severity of the pain being equal to the level of damage. No, instead, the pain arises out of the whole process of nerve activity – including nerves travelling from the disc to the spinal cord, from the spinal cord to the brain, and in the brain itself. There are lots of different things that make these nerves function differently, and it these changes in nervous system functioning that usually lead to someone experiencing chronic pain. These changes, when they occur in the brain and spinal cord, are called “central sensitization”. When these changes occur in nerves out in the body it is called “peripheral sensitization”. It’s very important to point out that, even when changes have occurred in the way the brain processes pain, this does NOT mean it’s the person’s fault, or that they could choose for it to be different, or that it would simply go away if they thought or acted differently, or that they have a “low pain threshold”. Nevertheless, thoughts, beliefs, feelings and behavior all require activity in the central nervous system, and all can contribute – to varying degrees – to your brain’s unconscious calculation of danger. This means they can all be involved, without you even knowing it, in the way your spinal cord dampens or amplifies the danger signals that are experienced as pain (once they are processed by your brain).
So to improve, the chronic pain sufferer needs to encourage their nervous system to change the way it works. If someone has a stroke, they need to be exposed to lots of new stimuli for their nervous system to change its structure and function in order for them to recover. Relatedly, a sufferer of chronic pain has to do the things that will drive their nervous system to change and adapt, and reduce its level of sensitization.
What are these things that will drive the nervous system to positively adapt – to reduce its sensitization and the amplification of pain? Well, that would be telling I can tell you it’s not a quick and easy process, but the first step is understanding what is happening to your body. Continuing to put all the focus on a poor old disc, even if it is bulging, will not help your body reduce its painfully sensitized state. Instead, taking control – not feeling helpless – immediately reduces your brain’s sense of danger. Is it time you (not quite like Mr Grey) took control? Seamus graduated from Latrobe University in 2003, receiving a Bachelor of Physiotherapy. He has comprehensive clinical experience, having worked in a range of hospital and private practice settings including Mill Park Physiotherapy Centre and the Royal Melbourne Hospital and Epworth Health Care in pain services. – Seamus Barker, Pain Management Physiotherapist.
Seamus Barker is the Coordinator of the Persistent Pain Program at Ballarat Health Services, and will also be consulting at Lake Health Group as a Pain Management Physiotherapist focusing on sensory and movement retraining, functional restoration and education for pain.
Currently undertaking a PhD with the University of Sydney’s School of Medicine and the University of South Australia investigating the contrasting accounts of pain provided by patients, by medical discourse, and by current neuroscience. He has had a long interest in the psychological and sociological aspects of pain, having also completed further training in CBT with the University of Sydney’s Pain Management Research Institute, as well as a Bachelor of Arts in Sociology at the University of Melbourne in 2012. Seamus is a member of the Australian Pain Society, the International Association for the Study of Pain, and Arthritis Victoria.