At least one in five Australians lives with chronic pain, and often the cause is unknown. Scientists are just now discovering the crucial role the brain plays in how pain is experienced, and how it might pave the way for innovative treatment, write Lynne Malcolm and Olivia Willis.
The economic and social burden of chronic pain is enormous.
While analgesic drugs can provide pain relief for many, their side-effects, tolerance issues and addictiveness mean that scientists are on the hunt for alternative treatments.
Every emotion and every cognition is amplified. People with ongoing pain, they anticipate pain with a lot of fear and they worry a lot of the time.Dr Sylvia Gustin, Neuroscience Research Australia
The challenge of developing such treatments has led to more research on the brain’s role in chronic pain.
‘At the moment we have focused our work to two areas in the brain,’ says Dr Sylvia Gustin from Neuroscience Research Australia. ‘One is called the thalamus—the other is the prefrontal cortex.’
Described as the ‘border in the brain’, the thalamus acts as the gateway between the spinal cord and higher brain centres.
When you sustain an acute injury there is an opening in the thalamus for information to pass through from the affected body part to the brain.
‘This is very important because then we need to heal, we need to relax, we need to look after ourselves. After an acute injury is healed, we know that this border should actually close.’
When researching people who experience chronic pain, Gustin identified a key neurological difference: the opening in the thalamus remains open long after acute pain is gone.
Gustin’s team found a decrease in the volume of the thalamus, resulting in a decrease of a specific neurotransmitter: gamma-aminobutyric acid, or GABA.
‘What this means,’ Gustin says, ‘is that in people with ongoing pain, this border is always open. Every signal gets amplified and it results in the experience of pain.’
Researchers also found people with chronic pain experienced a reduction in the volume of their prefrontal cortex—the region of the brain that is understood to regulate emotions, personality expression and social behaviour.
This results in a further decline in the neurotransmitter GABA.
‘Every emotion and every cognition is amplified. People with ongoing pain, they anticipate pain with a lot of fear and they worry a lot of the time, and they can’t dampen down these feelings because the prefrontal cortex has lost its ability to dampen down these thoughts.’
Anxiety, depression and suicidal thoughts can be big problems for those living with chronic pain, says Gustin.
‘Twenty per cent try to suicide. A lot of clients who I see, they can’t stop their worrying, they can’t stop their anxiety, and they ask me why.
‘I think showing them that there are subtle changes in the brain—and because of these subtle brain changes, they have these thoughts and they can’t stop it—it helps them to cope with that, because a lot of times they are stigmatised.
For many patients, what’s worse is the invisible nature of their condition.
‘You can’t see pain, and this is a very big thing for these people,’ says Gustin. ‘With my work, I can educate people that it’s a physical pain that results from subtle changes in the brain.’
According to Gustin, the research demonstrates that interaction between brain cells is damaged in the brains of people with chronic pain.
‘It’s in an unhealthy way, and we can change that. The border, the thalamus, can actually close, and we can do that with neuro-feedback.
‘We can change the way the cells talk to each other and we can actually rewrite the painful memories.’
The importance of perception
Through research on people living with osteoarthritis, Dr Tasha Stanton from the University of South Australia has discovered there are many surprising factors that influence pain, including the way a person perceives their own body.
‘If we give people [with osteoarthritis] pictures of their hand at different sizes and we say ‘please pick out which one best represents your hand’, they will choose the image that is significantly smaller.
‘That suggests that there is alteration in their perception of the size of their body part.
‘But it’s not limited to that—we also see problems with their perception of touch. They are not very good at localising where they are being touched and they are not very good at localising where that body part is located in space.’
Stanton says these tests suggest people with chronic pain process location-specific information differently. She hopes to use this new information to develop new treatments.
‘The tack I have taken has been saying: if we have these altered perceptions in people with pain, what if we actually target these perceptions directly?’
Working with people with knee osteoarthritis, Stanton and her team have devised a series of experimental ‘visual illusions’, in which patients wear video goggles while researchers feed them a ‘live video link’ of their knee.
Patients watch the video in real-time, unaware researchers are covertly changing what’s on the screen in front of them.
‘One of the more potent illusions that we use is called the stretch illusion. They are looking down at their knee and suddenly they see it start to elongate, as if the joint is stretching out and being tractioned.
‘At that exact same time, we give a slight pull on the calf muscle.
‘Both the visual and touch information is telling their brain, “Actually, your knee is stretching out big and long!” And for some people, they are getting pain relief with this type of illusion.’
According to Stanton, the research supports other evidence that suggests that information from one sense—like touch or vision—can modulate information that is coming from another sense.
‘Our brain takes information from all these different senses—from touch, from sound, from vision, from movement—it puts all these things together for us to create a perception or a feeling of our own body.
‘It makes sense, then, for treatments to embrace that multisensory nature.’
How to talk about pain
Toby Newton-John, a clinical psychologist at the University of Technology in Sydney, says the social dynamics around chronic pain can have a ‘very large influence’ over patients’ future expressions of pain.
‘If the person with pain expresses their pain a great deal and their partner responds to those expressions of pain in ways that the person in pain finds helpful or desirable, they are more likely to express those pain behaviours in the future.’
‘Equally, if a partner doesn’t respond [in a way that’s perceived] as being helpful, those pain behaviour expressions are less likely in the future.’
While a partner can inadvertently increase a patient’s disability by providing excessive practical help, Newton-John says continued emotional support remains crucial to people living with chronic pain.
‘Research isn’t at all saying that partners should just give up and have no further involvement with people with pain at all.
The clinical psychologist says it’s helpful to move away from constant discussion about the pain to expressing broader care and concern for that person as a whole.
‘Instead of asking, “How is your back?” the partner can ask, “How was your day today?”
‘Instead of asking, “Is the pain worse today?” the partner can ask, “How are you feeling in yourself today?”‘