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“ONE OF THE FIRST CHALLENGES IN UNDERSTANDING CHRONIC PAIN IN CHILDREN IS GETTING GOOD DATA”
It’s estimated that as many as 15 per cent of children in the UK suffer with chronic pain. Professor Suellen Walker explains UCL’s pioneering research project into the condition – and their collaboration with the University of Toronto
Photography Stocksy, iStock
Imagine having pain that persists for more than three months; that’s how doctors define chronic pain. In children, it can be recurrent pains such as headaches, abdominal pain and musculoskeletal pain, or it can be more persistent pain associated with diseases, chemotherapy treatment, tumours or inflammatory disorders including idiopathic arthritis and certain genetic conditions. One of the things that Dr Suellen Walker is most interested in is neuropathic pain (nerve injury pain), which is difficult to treat. “Normally pain pathways will respond to an inflammation, surgery or an injury and do what they’re supposed to do,” says Dr Walker. “They recover, and everything settles down. Occasionally the pain persists and the actual nerves are functioning but the sensitivity of the network has changed. But neuropathic pain is actually a disorder of the nerves that transmit pain.” Phantom limb pain is a classic example.
“One of the first challenges in understanding chronic pain in children is getting good data,” says Dr Walker, “because it depends on how you grade pain. We’re thinking about pain that affects function, i.e. pain that stops a kid from going to school and pain that needs healthcare services. It affects between five and 15 per cent of kids, but if you were to look at how many kids get limb pain, headaches or stomach pains, it would be much higher.” The lack of data is because this is an understudied area of child health; funding and research tend to focus on diseases themselves, rather than their symptoms. Meanwhile, paediatric experts are treating pain as part of an overall condition, and pain teams focus on understanding the pain itself and how children manage and cope with the pain so that they can get back to their normal functioning.
“Our UCL-UofT joint call for collaborative research is focused on understanding how different types of chronic pains affect the structure and function of the brain throughout the ages. The grant has allowed our two centres to come together and combine and exchange our expertise to develop novel insights into paediatric chronic pain. My lab has greatly benefited from the collaboration, as it has provided us the opportunity to develop new skills, and new insights into paediatric pain.”
Dr Massieh Moayedi, University of Toronto
The fact that pain is subjective and its severity and impact vary widely, is an added challenge. “Something that we’re trying to very much get away from,” says Dr Walker, “is the idea of whether a child’s pain is real or not. It does my head in when people say that it’s all in their head! We think that pain is whatever the child tells us.” But chronic pain can also affect a child’s behaviour – for example, their mood and sleep, and ability to go to school. At UCL GOS Institute of Child Health, this means looking at the whole picture, with researchers and scientists also working with clinical teams of doctors, nurses, psychologists, physiotherapists, and social workers.
Dr Walker believes that it is vital to identify and address chronic pain early. It’s already recognised that early-life events, adversities and neglect can have a long-term effect on mental and physical health. But her team are particularly interested in whether early life exposures in terms of pain, surgery, chemotherapy and other sorts of medical conditions can also have a longer-term effect. “Early-life experience of pain can alter your susceptibility to pain later on,” says Dr Walker, “either because of changes in how you cope with pain, or how your sensory function is working.” But the team also want to treat chronic pain early to prevent the long-term disability that goes along with it. “We want to get the kids back to school because that’s how they’re going to socialise and that is also going to help them to get better,” adds Dr Walker.
Three different groups of children are being studied. Professor Neil Marlow at the UCL Elizabeth Garrett Anderson Institute for Women’s Health is leading the study of the first group: children born extremely pre-term in 1995. His cohort are interesting, says Dr Walker, “because we know that exposure to pain and surgery in that very early phase of development, when the nervous system is immature, can cause long-term changes in sensory function.” A second group is children who are survivors of haematological cancers, leukaemia and lymphoma aged from 15 to 18. “We are working with the Great Ormond Street Hospital Late Effects Clinic to find out if these adolescents have pain or altered sensitivity. Research in the USA suggests that one in 10 or 12 childhood cancer survivors have persistent pain, but we don’t know what type of pain or how we could better recognise it or treat it.”
“ONE OF THE THINGS THAT WE’RE STARTING TO DO IS NEURO-IMAGING WITH MRIS”
Their biggest research group is children who are referred to the Chronic Pain Clinic at Great Ormond Street Hospital, recruited as part of their ongoing assessment. “It’s been much easier than I expected. Many families and children have agreed to help our research evaluating pain as they may have met doctors who didn’t understand their situation,” says Dr Walker. She recognises that many GPs may rarely see such complex cases. “Teaching and training about different types of pain in children is something that we’re trying to work on, because it’s something that a lot of people aren’t familiar with. Trying to get that education part right is so important. By the time these families get to us, they’ve been around the medical block and are really keen to understand more about what’s happening to their child. One of the things that we’re starting to do is neuro-imaging with MRIs. It’s an extra procedure that they must come back to the hospital for. Some have had MRIs as part of their clinical treatment, which can make it easier because they know what to expect, but a few have felt claustrophobic or worried during a previous MRI and yet may still agree to another one to help with research.” Their original plan was to recruit 74 children with neuropathic pain over three years, and they’re up to 60 already.
In the research, the team ask the children about their experience of pain. “We use questionnaires so that we can assess not just their pain, but also the impact it’s having on their wellbeing; their ability to go to school; their sleep, which is often a big problem; and their mood and physical function,” says Dr Walker. They also conduct quantitative sensory testing to look at the degree and distribution of altered sensitivity and how that changes both with treatment and with time – and across different conditions.
One of their cohort is 14-year-old Charlie. He has deformities in his feet which have resulted in repeated surgery. He has experienced a lot of pain related to the procedures, and the pain has become more persistent. Children like Charlie are learning how to manage their pain. “One of the difficulties is that we don’t have perfect medications for every type of pain,” says Dr Walker. “You might get some relief from medication, but there’s not always going to be a magic treatment. We also want to make sure that Charlie’s sleep improves and he’s able to cope with the pain. Kids are very good at using distraction and other strategies to help manage their pain.” With more detailed assessments such as sensory testing, the research is helping kids like Charlie to see and feel where their pain is different and better understand and manage it.
“Participating in UCL’s research was enjoyable for me because I got to experience different types of sensitivity tests and got a massive insight into the world of chronic pain and its effect on my senses and nerves. I got a lot of knowledge from the experience – and knowledge is power in terms of coping with my own pain.”
Charlie, a 14-year-old patient at Great Ormond Street Hospital
UCL has a strong track record in both neuroscience and pain research on the relation between neuroscience and pain, but the Global Engagement Strategy has helped to raise the bar higher for pain in children. By collaborating with the University of Toronto, one of the few other centres for pioneering pain research in kids, they are amplifying their expertise and collaborating on grants. “By sharing our protocols, using the same outcomes and the same test methods, we can combine our results and get a bigger sample size. We can also compare children with different types of chronic pain across different centres,” says Dr Walker. A key collaborator in Toronto is Dr Massieh Moayedi, an expert on adult pain imaging, who used to work at UCL.
Eighteen months into their project, the team have got two papers in the pipeline and are working towards several goals. “Some of our kids with genetic causes underlying their pain are very hard to treat with the available drugs, so we’re hoping that research by us and other pain researchers at UCL will help to identify more specific targets and better interventions,” says Dr Walker. They are also trying to validate screening tools for neuropathic pain and sensory changes, so that GPs and paediatricians can identify these conditions and make referrals more quickly if needed. “There is a process of needing to exclude various conditions, but ideally managing the pain would be going on alongside this process rather than just being a later option.”
Dr Walker has been at UCL for 19 years. “It’s one of the few institutions involved with paediatric pain research and its interdisciplinary departmental infrastructure and excellent track record with close collaborations across university and hospital sites is basically why I’m here!” she says. Along with other experts around the world who specialise in child pain, she hopes that a Lancet commission will further raise awareness about childhood pain. “While we’re trying to find better interventions for the future, our current research is aimed at better understanding their pain so we can direct our existing treatments to the right kids at the right time. For me that would be a great start.”
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