Yes, pain really is all in your headby Ruth Laugesen
A revolution in brain science has led to the discovery of new ways to stop persistent pain.
Ken Ng was 12 when he had his left leg amputated below the knee to stop the spread of bone cancer. It was the start of a long journey of pain. Phantom sensations from his amputated limb haunted him as a teenager, including stabbing sensations and a vice-like constriction around his stump. It got worse when he moved to Wellington to begin studying for his law degree. By 2009, the sensations flooding in from his absent limb were consuming him.
Each day he downed a succession of prescription painkillers – codeine, tramadol, Neurofen and Voltaren. “I couldn’t really study any more, I couldn’t sit my exams. It made me introverted, I didn’t want anything to do with people. I wasn’t eating, I stopped going to lectures and the tramadol was making me hallucinate.” Ng sought help from his GP, who referred him to Capital & Coast District Health Board’s pain clinic. Luckily for Ng, the clinic had just begun to offer a simple but revolutionary new therapy, which recognises that some types of chronic pain are caused not by tissue damage but by changes in the wiring of the brain. Ng started his treatment with two weeks of computer exercises looking at pictures of right and left legs, and then began mirror therapy.
Ng’s occupational therapist, Maria Polaczuk, seated him with a large mirror positioned upright between his legs so it reflected his whole right leg. “All I could see was two bare normal legs. I massaged my right foot with my hands, manipulated it up and down. I was getting a sense of what a foot felt like.” As he looked at this reflected whole leg in the mirror, where usually he would see an amputated limb, something strange started to happen. “The tingling painful sensation in my stump started to fade and become less prominent.”
After two weeks of mirror exercises, four times a day, the phantom pain disappeared altogether. Now 22, Ng has been able to stop taking painkillers. He has had one brief attack of phantom pain, after a period of stress, but apart from that he experiences only the more routine discomfort of pressure on his stump from his prosthesis. Mirror therapy is one byproduct of a great leap forward in science’s understanding of pain and how it is manufactured in the human brain.
A decade and a half of brain imaging has found that although tissue damage is very important in determining pain, it is not the only ingredient. When you injure part of your body, an alarm goes off in the central nervous system in the spinal cord and brain. The brain constructs the pain experience by assessing not just the injury but also thoughts, feelings, context, beliefs, expectations, past experiences and genetics. Any of these factors can turn the volume up or down on pain. These other factors can also influence whether the brain’s pain system becomes stuck on high alert in the long term, even when an initial injury has subsided. Some 700,000 New Zealanders, or one in six, suffer from chronic pain. This is pain that has lasted for three months or more; arthritis and back pain are two common types.
Tissue injury is not the cause of ongoing pain for many people, such as those with irritable bowel syndrome, fibromyalgia, headaches, chronic regional pain syndrome, and back pain that isn’t resolved after operations. For these patients, the central pain system has malfunctioned, in what some clinicians argue is a form of neurological disorder. Neurological factors are also at work for those patients whose pain is out of proportion to the severity of the disorder they are suffering from – for example, people who have severe pain but apparently only mild arthritis. Phantom limb pain is one extreme example of how the brain can conjure up pain signals out of thin air. But in many other pain conditions, processes in the brain can play a stronger role than doctor and patient might think.
“The idea that more damage on my finger leads to more pain, and less damage leads to less pain, and there is this nice one-to-one relationship is absolutely untrue,” says Irene Tracey, head of the Oxford Centre for Functional Magnetic Resonance Imaging of the Brain, here recently to speak at the annual conference of the New Zealand Pain Society. “There is a long journey from that little finger up to the brain. And what we’ve appreciated from the science in the past decade is that along that journey we have these exquisite mechanisms for changing the firing rate of these inputs, and we can make the pain get much bigger and we can make it get much less. And when it gets into the brain, we can make it go to all sorts of different places. And that’s something you can’t see, and that you’re not going to understand just looking at the little finger.”
She says pain is in the brain because that’s the organ that generates the experience. “People still somehow think that pain is out there in that bad arm or bad leg – what they don’t appreciate is that is just part of the process, and if you don’t have an active conscious brain, you’re not going to experience that injury to your knee. It’s actually okay for the pain to be in your head, because it is a very flexible malleable perception that can change.”
These systems in our brain have amazing abilities to modify the experience of pain, she says. “What we now have to do is see how we can harness the good ones and limit the bad ones. So when people are encouraged to come up with mechanisms to reduce their anxiety, lift their mood or be more positive, this really is fundamentally changing chemistry, anatomy, physiology and brain networks. And that will influence the end result of what pain you have just as much as if you went to the original damaged area and made it worse or made it better.” This is why if two people sprain their hands, the outcomes can be very different.
One person might heal rapidly and feel little pain, whereas the other person might develop agonising, crippling pain in the hand for years, despite x-rays showing the hand is physically fine. When the first brain maps of pain began appearing 15 years ago, some expected the pictures would show a few discrete sections of the brain at work processing sensations from a distant wounded body part. The surprise was that large territories of the brain go to work when people burn their finger or stub their toe. “We looked at these brain maps and we thought ‘holy shit’,” says Australian pain specialist David Butler, head of the Neuro Orthopaedic Institute. “We thought there would only be one or two areas turned on when you have pain. But you can have 300 to 400 areas turned on with the pain experience.”
Why does so much of the brain need to be involved in deciding how badly something hurts? Says Tracey: “Pain is such an important experience for survival that you need to have the fl exibility to alter it for the situation you’re in. Sometimes you don’t need to be dealing with the pain, because there might be something more life-threatening, so you need to be able to block it – you need to be able to control it.” In fact, the brain brings so many of its facilities into play in processing pain that scientists have so far failed to find any single corner of the brain whose sole job it is to be a gateway for pain, a so-called primary pain cortex.
A painful stimulus isn’t even necessary to light up some of the brain’s pain centres. Empathy can be enough. Researchers have found that some of the same pain centres are activated when someone sees a loved one receiving a painful stimulus as when someone receives the painful stimulus themselves. And if you are feeling depressed, a jab or a burn hurts more. In one 2010 study, a group of university students was divided into two groups, one of which was played doleful music at half-speed while being read gloomy statements. The other group was played neutral music and was read neutral statements. Then members of both groups were exposed to painful stimuli. Those in the gloomy group rated the pain worse and had increased activity in a broad network of brain areas.
Anxiety, catastrophising and negative expectations also make pain worse. And that doesn’t mean anxious people merely complain more loudly. Anxiety changes the structure of their brain to process tissue-damage signals differently, amplifying the pain signals so they get stronger. On the plus side, the brain also dampens down pain if it is distracted. Studies have found distracting people when pain is applied leads them to rate the pain as being lower in intensity and less unpleasant than those who have not been distracted.
Research done in 2004 found pain centres in many parts of the brain were much less active for those who were being distracted while pain was applied. Meditation has also been found to dampen pain – it increases activity in the part of the brain involved with cognitive regulation of incoming injury signals. Thoughts and feelings loom so large in our experience of pain that they can cancel out some of the most powerful painkillers. In a study by Tracey published earlier this year, a group of volunteers were hooked up to intravenous lines and given painful burns. They were told that they would later receive an opioid. After the first burn, the subjects rated the heat at six out of 10 for pain. Unknown to them, they then started receiving the powerful short-acting opiate Remifentanil, which is used in anaesthesia.
They then rated the pain as five, showing the opiate was having only a small effect. Actors dressed as nurses then came in and pretended to start the opiates. The subjects’ assessment of their pain dropped to two once they knew they were getting the drug. Next, the subjects were told the opiate had been stopped, and that often people experienced worse pain after an opiate was withdrawn. The subjects’ assessment of their pain rocketed back up to six, where it had been before they had received any painkiller. What they didn’t know was they were still being dosed with Remifentanil. Their negative expectations were so powerful that it had completely wiped out the effects of the drug.
Tracey’s research has big implications for how doctors talk to their patients about painkillers, says Dr Paul Hardy, clinical director of the Wellington regional pain service. Tell a patient that a painkiller might not work for them, and it probably won’t. “You need to use positive encouragement, saying this is going to help your pain and make your pain go away.” The brain-mapping revolution has confirmed why some of the established treatments for chronic pain offer some relief, treatments like cognitive behavioural therapy, antidepressants, meditation and hypnosis. The research has shown that these treatments work in dampening pain intensity. And they also confirm the importance of exercise, social contact and positive expectations. Cognitive behavioural therapy is particularly powerful in changing brain architecture, by tackling beliefs, thinking processes, anxiety and depression.
Ng’s mirror therapy is part of another branch of pain research that focuses on physical therapy as the key to unscrambling distortions in brain wiring that are fuelling the pain experience. University of California neuroscientist Vilayanur Ramachandran first developed mirror therapy for phantom limb pain in 1994. It was then incorporated into a wider physical therapy known as graded motor imagery developed by Lorimer Moseley, professor of clinical neurosciences of the University of South Australia, in collaboration with Butler of the Neuro Orthopaedic Institute, which trains therapists in the techniques.
Graded motor imagery is offered by about 100 physiotherapists and occupational therapists around New Zealand, and began here three years ago after Moseley and Butler gave conference presentations. It is focused on types of pain present on just one side of the body, particularly in limbs, in conditions such as phantom limb pain, brachial plexus tears and complex regional pain syndrome. It doesn’t work for everyone, as it takes concentration and effort, but for those who have success the results can be dramatic.
New evidence is coming through that the techniques also help some people with carpal tunnel syndrome and osteoarthritis of the knee. And at the Wellington regional pain clinic, the technique has brought a breakthrough for one patient with decades of excruciating pain to one side of the face from trigeminal neuralgia, which was set off by even a breeze on his skin. That patient has now been able to stop taking painkillers. Graded motor imagery is a “fabulous” addition to the pain toolkit, says Hardy, who asked staff to start using it at the regional pain clinic after he came here from the UK, where he had seen it in action.
In many chronic-pain patients, an affected body part is so painful that they are highly resistant to moving it, and therefore cannot do the exercises needed to begin the healing processes, says Butler. Brain mapping has revealed that these are not just recalcitrant patients, but that in many painful conditions, the brain map has changed, assigning more nerve cells in the brain to the painful body part, in a process known as “smudging”. “We know, for example, if you’ve got chronic back pain, then in most people the nerve cells in the brain looking after the back will expand and spread. Essentially your back gets bigger in your brain. It’s just your brain looking after you, saying that back’s in trouble,” says Butler.
“Some of the ways you can change the brain is to get your body going, because as soon as you can get your body going normally, then those brain cells will change.” For patients who are terrified of moving because of pain, computer exercises are the first step, involving recognition of right and left limbs. Often such perceptions have become scrambled as a result of the “smudging”. By trying to recognise left and right limbs in various positions, patients are essentially moving their own affected body parts in their head, and taking the first step towards unsmudging. However, some patients find even these mental exercises excruciatingly painful.
“I’ve been consulting on a lady who has a complex pain-syndrome problem in her left hand. If I show her a picture of a left hand and ask her if it is left or right, she’ll go into a panic attack. The brain has worked out that it needs to protect that hand, and if protection means closing down some of the basic elements of movement, like judging whether it is left or right, or planning movement, the brain will actually do it.” For patients like this, an even gentler first step of therapy is watching others moving the affected limb, such as on television or in a film. The final step in graded motor imagery is mirror work, which can correct the neural representation of the reflected limb. With a phantom limb like Ng’s, the brain’s representation of th absent limb becomes “smudged”, generating pain.
Butler, who is a physiotherapist, says a strong body of research has established some of the common factors for those who develop chronic pain conditions. “Firstly, simply a belief that pain equals damage. The second thing that produces chronic pain is something called fear avoidance, where people are fearful of movement because it hurts too much, and they are terrifi ed they will damage something. “Another thing that predicts whether someone goes on to chronic pain is an absolute search for a passive answer, whereas we know that those who seek an active answer, which might mean knowledge or exercise, will do better. And the fourth thing that always predicts whether someone goes on to chronic pain is a withdrawal from social life. They decide to stay home, to retreat.”
And he says scary medical diagnoses can in themselves create changes in the brain – for example, in the diagnosis of “slipped disc”. In reality, says Butler, there is no such thing as a slipped disc, as the discs in the spine are firmly held in place. What they are is bulging discs. “If you’re told that you’ve got a slipped disc and that the x-ray shows degeneration, but you aren’t told that this is very common, that 70% of people have bulging discs, and that 90% of people have degeneration in their back, then that would be another reason that the brain would change. There would be more fear; it would increase the belief that pain equals damage; it would give you more fear avoidance; and you would say, ‘I’m not going out tonight, I’m staying home.’”
Butler’s recipe for recovery from pain is to accept that in many cases pain is normal, to get moving, to be social and to seek active answers. Pleasure is also part of the answer. “When the brain lights up and feels pleasure, it’s not much different than pain. When you’re having pleasure, you’re exercising the bits of your brain related to pain. The more pleasure you have, the less pain you’ll have.” For Ng, life is now blessedly more ordinary. He has been able to continue his studies, and is due to finish his law degree this year. “I can do so much more. Everything’s more normal.”
'I turn the pain off...'
One woman’s experiences with guided motor imagery are paying off.
Wellington ecologist Suzanne Bassett was driving home one morning in October 2009 from Rotorua where she had been working in a conservation forest catching kiwi and studying their eggs. Near Hunterville on State Highway One, an oncoming driver crossed the centre line and smashed head on into Bassett’s car. Her injuries were so severe that emergency personnel initially phoned her in as dead. But she survived, and a long and difficult journey began. Worst affected was her crushed left knee and lower leg. The surgeon fastened the joint of her knee back together with a network of wires.
Bassett, who is chirpy and quietly unsinkable, persevered through painful physical therapy and learnt to walk again. However, every step sends shooting pains up her leg. Even at rest, her knee hurts badly. A mother of a five-year-old, Bassett was having to take painkillers daily to tolerate the pain until physio therapist Dagmar Hempel introduced her to guided motor imagery, a recently developed technique that vividly demonstrates how powerful the brain’s perceptions are in shaping pain.
Bassett sits down on a chair and places a long mirror facing her good right leg, so she can see its reflection in the mirror. It looks like she has two good legs again, left and right. Her damaged left leg is hidden from view. She looks into the mirror andcarefully in unison lifts her right toe and her left toe on the hidden side of the mirror. This movement causes intense pain in her bad leg. As she stares at the mirror, though, something changes.
“Now I’m switching the pain off in my left leg.” The pain is gone. She stands up, puts her weight on both feet, and the pain floods back to her left leg. She looks into the mirror, and switches off the pain again. The pain stays switched off until Bassett moves again. But the technique has offered enough relief that Bassett no longer needs to take painkillers, and feels more clear-headed as a result. She can sit on the couch painfree and read her daughter a story. Bassett is now patiently working on extending the technique for longer and longer periods of time.
“I still have a leg filled with metal that hurts, but we’re trying to turn it off all the time. I think I’m much better able to cope with my pain, and I think I’m reducing the amount of pain I’m in. When I turn the pain off and I sit there happily, I just think that’s amazing.”
When the cure can make things worse
Sometimes the treatment for pain can be highly dangerous.
Wellington designer Alex, 59, was skiing in Colorado last year when he had to seek urgent dental treatment for a tooth abscess. Afterwards, the dentist handed him an unfamiliar prescription – for oxycodone. A former drug addict who has been drug-free for 15 years, Alex did as he was told and popped one of the pills. The results were surprising. “It was just like heroin.” He didn’t sleep that night, but drifted in and out of a dream state, one that drug users call being “on the nod”. The next day, he “skied like a teenager”, taking risks he wouldn’t usually take. Back at his hotel room, he got rid of the rest of the bottle, unsettled by how strong the drugs were.
Oxycodone, marketed as OxyContin, has brought an epidemic of addiction and overdose deaths in its wake in the United States. Now it is being heavily used here, too. Since it was subsidised by Pharmac in 2005, annual prescriptions have shot up to 186,000, overtaking morphine. The growth in oxycodone prescriptions has been such that the total use of strong opiates in New Zealand has more than doubled in the past 10 years, from 200,000 prescriptions a year to 500,000.
Wellington regional pain service clinical head Dr Paul Hardy believes oxycodone is far more addictive than morphine. “It can be very difficult for patients to stop taking it. “We see a number of patients who have been given oxycodone postoperatively after having had simple surgery, for fractures or hernia. A number of these patients we actually transfer across to morphine because it’s easier for them to stop taking morphine than to stop taking oxycodone. Between tablets of oxycodone, patients get a craving for the next tablet.”
Whereas in the past strong opiates were mainly used for cancer pain, much of the growth in oxycodone use appears to have come as a result of extending it to non-malignant conditions, such as arthritis and other chronic pain. Drug company Mundipharma has promoted oxycodone to doctors as suitable for severe arthritis pain. But although opiates are effective short-term painkillers, there is no evidence they are effective in long-term treatment of chronic pain. One of the potential side effects of long-term use is actually an increase in pain.
“There is a point at which you don’t get any better pain control, so the dose goes up and up and up, and all you do is consume more drug, develop more addictive tendencies, get more side effects, but you don’t actually get more pain control,” says Hardy.
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