Sufferers of chronic pain in a limb perceive the space around the limb less accurately, according to a study by Lieve Filbrich and Valéry Legrain, researchers at the UCL Institute of Neuroscience. Chronic pain’s impact on vision suggests complex changes in the patient’s brain as well as the value of cognitive rehabilitation in treating it.
When we feel pain, our brain automatically locates it but also detects, through our vision, what provokes it. Thus it coordinates different sensory modalities: touch and perception of pain to monitor our body, and vision to track our environment. If vision and feeling pain are coordinated by the brain, what happens if one of these two senses is disrupted? Lieve Filbrich and the team of Valéry Legrain, researchers at the Pain Research Lab of the Institute of Neuroscience (IONS/COSY), tried to answer that question. ‘We wanted to analyse what happens at the visual level if we suffer chronic pain,’ they explained, ‘and more specifically in the space that surrounds the afflicted limb.’
Cognitive disorders related to chronic pain
For this study, which was published in Scientific Reports, the team considered patients suffering from complex regional pain syndrome (CRPS), a rare disease that causes pain in a limb (for example, the hand or foot). The pain often arises after minor trauma, such as a fracture or an operation, but is disproportionate to the triggering event and can become chronic. Symptoms in the afflicted limb include inflammation, swelling, temperature change, colouration, etc. Patients also report various cognitive disorders, including difficulties forming a mental picture of the afflicted limb, moving it or sensing when it is touched. ‘Considering they perceive stimuli to their afflicted limb less accurately,’ Lieve Filbrich said, ‘we wondered whether they also perceived stimuli in the space surrounding the limb less accurately, such as visual stimuli.’
Altered vision of space around afflicted limb
‘We tested 14 patients who suffered from CRPS in an upper limb, essentially the hand’, Lieve Filbrich said. ‘We showed lights in different places, for example near or far from their hands. Each time, two lights followed one another very rapidly first on the left, then on the right, and vice versa. We asked patients to make a temporal judgement, that is, to tell us which light appeared first, on the left or right.’ The result: patients systematically misjudged the order of the lights near the afflicted hand, especially at close range. ‘It’s as if they had impaired perception of the visible space around the afflicted hand’, Valery Legrain explained. ‘This shows that a deficit in a limb can provoke changes in the brain, as a result of brain plasticity, and in how the brain handles visual information.’
A new chronic pain treatment?
These results open the way toward new treatments for chronic pain through cognitive rehabilitation. ‘This technique could complement pharmaceutical and physical therapy’, Valery Legrain says. ‘The goal would be to rearrange the pathways in the brain through neuropsychological rehabilitation. The idea would be to rebuild the schema the other way around: improve visual-motor coordination to influence the way they perceive pain. There have already been attempts at visual-motor coordination training techniques that suggest an influence on pain, but there are still too few trials on the subject.’
Before envisioning the development of a treatment, researchers must first understand the mechanisms at work. ‘Perception of space is a complex skill,’ Valery Legrain specifies. ‘It requires different spatial capacities. We have to identify which one is lacking in order to rehabilitate it.’ To do this, the team envisions continuing to work with CRPS patients in two ways. ‘We’ll introduce electroencephalography to observe brain activity and study the neurophysiological mechanisms at work. We’ll also use virtual reality techniques to change their visual environment and observe how they react.’
Collaboration with England
In the next stage of their research, Lieve Filbrich and Valery Legrain plan to work together with a University of Bath (England) group led by Janet Bultitude, who published a similar study on the subject. ‘We had no idea they were also working on it’, Valery Legrain explains. ‘Our results appeared independently in two separate journals, and they were very similar, which reinforces their validity. So we decided to work together. We have greater expertise than they do in neuroscience, including in using electroencephalography, and they have better access to patients owing to their hospitals specialised in this syndrome.’
‘The first results reinforce the recent theory that the brain doesn’t treat pain as an isolated sensation’, Valery Legrain concludes. ‘It’s integrated with other information, such as the perception of visual space, within a general warning system involving many mechanisms that allow the body to react efficiently to potential danger.’
Note : this research was financed by the Belgian Fund for Scientific Research (FNRS) and led by Dr Lieve Filbrich as part of her PhD thesis, with the assistance of her supervisor Dr Valéry Legrain and her team at the Pain Research Lab.
A glance at Lieve Filbrich's bio
2009-2011 Master’s Degree in Psychology, UCL
2011-2012 University Certificate in Psychology, UCL
2011-2013 Clinical Neuropsychologist
2013-2017 PhD in Psychology, UCL, financed by F.R.S-FNRS
Dr Filbrich is currently seeking postdoctoral funding to continue her research.
A glance at Valéry Legrain's bio
1994-1999 Master’s Degree in Psychology, UCL
1999-2003 PhD in Psychology, UCL, financed by F.R.S-FNRS
2003-2007 F.R.S-FNRS Research Associate
2004-2005 Postdoctorate, Université Claude-Bernard de Lyon
2007-2008 Postdoctorate, Heinrich Heine University Düsseldorf
2009-2013 Postdoctorate, Ghent University, financed by FWO; separate short residencies at University College London.
Since 2013 F.R.S-FNRS Research Associate and Visiting Associate Professor, UCL, Co-coordinator, Pain Research Lab of the Institute