Research linking the immune and nervous systems will revolutionise pain treatment

Ever wondered why your body aches when you have the flu? The virus responsible doesn’t directly affect muscles or nerves. So, what’s behind all that body pain?

New research findings from the Centre for Nanoscale BioPhotonics (CNBP) answer that question and will, health practitioners say, lead to a revolution in treating pain. Centre Director, Prof Mark Hutchinson, spearheads a group of researchers who, for the past 5 years, have been developing and using cutting-edge light technologies to view the molecular basis of pain.

Like 21st century incarnations of the earliest microscopes that revealed cells for the first time in the 1600s, these new technologies are providing intimate new insights into the inner workings of the human body. And when looking at pain, they’ve uncovered an inextricable link with the immune system. It’s a transformative concept for the medical and health community that’s already starting to be applied in the treatment of chronic pain.

‘There are about a trillion cells in your central nervous system and about 80% of them have an immune function, but no-one ever quite knew what they were there for,’ says David Butler, an Adelaide-based physiotherapist who’s been helping chronic pain sufferers for 3 decades. ‘Mark Hutchinson’s group has shown that those cells are critical in the pain experience. Research from groups like Mark’s have helped us understand that every event that goes on in the brain is part of the relationship between the immune system and the nervous system.’

So, we can now explain that the widespread body pain accompanying flu is due to the immune system being out of balance. Mostly, however, once the body is rid of the flu virus, the aches and pains subside as the immune system settles down. But what about long-term recurring pain such as that labelled ‘a migraine’ or persistent ‘lower back ache’? These kinds of chronic pain afflict more than 3 million Australians and because they’ve previously been considered mostly inexplicable, they’ve often been poorly treated.

But this new paradigm linking pain to the immune system changes that. It offers, at last, an explanation for chronic and recurring pain, which brings new opportunities for developing treatment.

‘The discoveries being made at the CNBP are providing clinicians and patients with tangible names and images of new cells and molecules responsible for the persistence of pain,’ Prof Hutchinson says. ‘And that’s important because we’ve have been challenged in pain by not knowing as much as we need to about the fundamental science behind its persistence.’

‘This new appreciation for the immune cells within the brain and spinal cord being involved with chronic pain, and the molecular signals found for that, gives hope because none of the drugs we have today target brain immunology.’

Most current pain medications target nerves, but this new perspective on pain suggests drugs targeting the immune system could be more effective. And they may have fewer side effects, such as the addiction problems that come with opioids, which are widely used for severe pain.

Beyond the development of drug treatments, the research findings may shine a light on the mechanisms behind psychological treatments for chronic pain, Prof Hutchinson says. ‘An appreciation for brain immunology may also help explain why talk-based therapies, like cognitive-based therapies, are so important in treating chronic pain, because changing thought processes may change the immune molecular drivers of pain.’

For Butler, that’s confirmation of the multi-pronged approach he and many other physios now take in their treatment of pain. ‘Mark’s work has certainly made us appreciate the importance of educational psychology as well as health psychology, advocating approaches such as cognitive behavioural therapy, mindfulness, hypnosis and conceptual change strategies that make the pain experience less threatening,’ he says.

The new research also promises to take the subjectivity out of measuring chronic pain: it should be possible to ultimately develop a way to identify, read and measure it with something as simple as a blood test.

That, in itself, is hugely significant because the often seeming inexplicable and unmeasurable qualities of chronic pain can see sufferers stigmatised, explains Dr Meredith Craigie, a staff specialist in the pain management unit at the Queen Elizabeth Hospital in Adelaide and Dean of the Faculty of Pain Medicine at the Australian and New Zealand College of Anaesthetists. ‘The old thinking was that if you still complained of pain after tissues had healed, you were making it up, fabricating it, malingering,’ she says. ‘Now we’re recognising that pain is a complex sensory and emotional experience, not just a simple neurological process in response to tissue damage.’

One of the most valuable things about developing a test for pain would be that it could validate people’s experiences, Dr Craigie explains. ‘So, this research that Mark and his team are doing is absolutely fundamental to changing the conversation in our community around the value of people who live with pain and the need to actually better understand what’s going on and treat it better,’ she says. ‘It offers hope of finally getting some decent treatments because much of what we have got, we have had for the last 30 or 40 years.’

Butler shares that hope: ‘Colleagues and I would be quite happy to say that with the current data, recovery is on the cards for many people who have in the past been told, “Let’s just try and manage your pain.” Now we’re seeking recovery.’