Look up a definition of pain, and invariably it will feature the word ‘distress’. This intersection of the physical and psychological is one of the elements that makes chronic pain so difficult to diagnose and treat, and why people with chronic pain can often fall through the cracks in the medical system.
It’s a sometimes-controversial conundrum that has preoccupied Dr Bernadette Fitzgibbon’s research career: “It is the subjectivity of pain,” says Dr Fitzgibbon, explaining her determination to help people better understand chronic pain. Dr Fitzgibbon is a National Health and Medical Research Council (NHMRC) early-career research fellow and head of the Pain and Affective Neuroscience Unit at the Monash Alfred Psychiatry Research Centre.
“Because people can’t see it or pinpoint its source, and think that it’s all in someone’s mind, it can be dismissed and put in the ‘too-hard basket’.”
While working in the field of rheumatology for her master’s degree, Dr Fitzgibbon came into contact with a large group of people with chronic pain disorders, whose medical conditions were inordinately complex and often unresolved.
One such disorder is fibromyalgia, a chronic condition defined by widespread, diffuse pain, but which can also present with fatigue, sleep and cognitive problems, and symptoms of depression. People with the disorder are often misdiagnosed as having depression or chronic fatigue, and can sometimes live with fibromyalgia for many years before it’s correctly diagnosed.
Even then, the situation is far from straightforward. There are no blood tests, no inflamed joints or elevated biomarkers that definitively identify fibromyalgia.
To make matters even more complicated, fibromyalgia is often – but not always – associated with mental trauma or illness, such as childhood abuse.
Current treatment options for fibromyalgia tend to focus on trying to mute or mitigate the sensation of pain through the use of opioids, anti-inflammatory drugs or steroids.
But there’s growing evidence that chronic pain disorders such as fibromyalgia are associated with heightened activity in the central nervous system, so that it becomes more acutely responsive to painful stimuli.
Pain a personal experience
This prompted Dr Fitzgibbon to question whether, instead of trying to address the pain itself, a treatment could change how a person experiences that pain and thereby reduce the distress. Her research is focused on a part of the brain called the dorsolateral prefrontal cortex. This region is a key component of the neural network involved in the experience of pain, particularly related to the cognitive and emotional components of that experience, and it is relatively unstudied.
“While the sensory network is taking in the location and the intensity of pain, cognition and emotional components are all about your reaction to it,” Dr Fitzgibbon says. The dorsolateral prefrontal cortex may be the reason some people, including elite sportspeople and endurance athletes, can endure extraordinary levels of pain, while others show a much greater degree of what is uncharitably called pain ‘catastrophisation’.
“The dorsolateral prefrontal cortex is involved in regulating pain, so for people who receive negative information in any form, the dorsolateral prefrontal cortex is essentially determining: ‘Is it really bad or is it going to be OK?’ “For people with a higher degree of catastrophisation the answer is ‘not OK’ and so they tend to experience pain more intensely.”
The dorsolateral prefrontal cortex may also explain why mood has such a significant influence on pain and why depression is more common in people with fibromyalgia. “If people already have low mood, it’s much harder to regulate your emotion, because you’re ruminating on a negative experience more than you would do if you didn’t have depressive symptoms,” Dr Fitzgibbon says.
In one trial, Dr Fitzgibbon has been investigating whether it might be possible to modulate an individual’s perception of pain by using transcranial magnetic stimulation – or a version of this called beta burst stimulation – to target the neurons in this part of the brain.
At the same time as deploying this potential new therapeutic approach, Dr Fitzgibbon will record subjects’ brain signalling patterns over the course of treatment, to see how the pain circuits of the brain change with symptom relief.
She’s also working to understand how life experiences such as trauma – whether physical or emotional – influence how pain is processed, which is particularly relevant for a condition such as fibromyalgia. It may be that these early experiences change the pain systems in the brain and make certain people more susceptible to developing chronic pain disorders.
“By the end of my career I’d love to be able to say that we have identified that there are experiences across the life span that influence your chance of going on to develop disorders like fibromyalgia, and use this information to provide preventative resources early on,” Dr Fitzgibbon says.
Ultra athletes and the bucket test
When it comes to pain tolerance, ultra marathon runners are in a league of their own. They are able to run for days at a time, with hardly any rest, pushing the human body to the limits of endurance. For this reason, they are also a fascinating case study for researchers seeking to understand how people experience pain.
Dr Bernadette Fitzgibbon and her colleagues have been studying ultramarathoners, using a variety of tests to understand why signals of pain that might severely incapacitate an average person are brushed off by endurance athletes.
In one setting, subjects were asked to hold their hand in a bucket of iced water for as long as they could. Dr Fitzgibbon herself could only last about six seconds. The ultramarathon runners kept their hands in the freezing water for the full three minutes. The researchers are also looking at heart rate, skin conduction and brain activity in this group.
“We are seeing substantial differences, both in how pain is tolerated and experienced, as well as a relationship to pain-related cognition,” Dr Fitzgibbon says.
The hope is that the findings from these ultra marathoners will shed light on what might be happening with people at the other end of the pain-experience spectrum, such as those with fibromyalgia and other chronic pain disorders.
At the time of writing this article, Dr Fitzgibbon was employed by Monash University.
Related:
Evidence for the improvement of fatigue in fibromyalgia
