The release of compelling new research has sparked fresh debate about the source of Complex Regional Pain Syndrome. Hot on the heels of the latest insight, WPR’s Sarah Nelson reflects on the rare chronic pain syndrome.

Persistent and polarising – yet poorly understood – Complex Regional Pain Syndrome (CRPS) inflicts debilitating pain on approximately 16,000 people in the UK. But with no specific test to confirm the condition, and a raft of infections and autoimmune issues often needing to be ruled out first, confusion is rife.

Individuals presenting with CRPS tend to report prolonged, severe pain which may be constant and likened to burning, stabbing, and stinging in their arm or leg. Associated symptoms of the condition also encompass a change in skin temperature, swelling, stiffness, or difficulty co-ordinating muscle movement.

The unrestrictive nature of CRPS’ features is not dissimilar to the diversity of sufferers who bear the brunt of it. Although more prominent in females, and rare in the elderly, it can showcase in anyone at any time. A limited portion of children under 10 are affected by it – and they, along with adolescents, hold a more promising prognosis.

A CLEAR CAUSE – OR A LACK OF CLARITY?

In 90 per cent of CRPS cases, its on-set is prompted by prior trauma or injury, such as limb immobilisation, sprains, strains, and soft tissue injury. But why do we only see this excessive response to injury in a certain number of patients? And why is the pain experienced disproportionate and potentially longer than would be expected for the damage itself? For one case in every 10, the trigger isn’t obvious. And whereas most people recover well within a year, some people have some or all of the symptoms for many weeks, months, or even years.

Spurred on by this ambiguity, researchers at the Universities of Bath and Oxford, have published new research in the journal, Brain. For their study, the scientists were keen to uncover more about how and why individuals suffering from CRPS report losing track of the position of their painful limb and not being able to move it.

The team tested how quickly people with CRPS processed visual information in the side of their environment nearer to their painful limb compared to the other side of the environment. And using laser pointers controlled by a computer, they projected two flashes of light onto the left and right side of a board that was placed in front of the patients, and the patients had to say which light appeared first.

Their results subsequently demonstrated that people with CRPS processed the light on the affected side of the board more slowly than the light on the unaffected side, suggesting that information that is nearer to the affected side of the body isn’t processed by the brain.

Speaking on the findings, lead author, Dr Janet Bultitude, from the University of Bath’s Centre for Pain Research, explained, ‘People with CRPS are usually in constant pain that they can’t ignore. Yet paradoxically they often report that they are not sure where their painful limb is unless they look at it directly, and that movements are not automatic – they have to ‘tell’ their limb to move. The odd sensations they experience suggest there could be a change in mechanisms that normally allow us to process information at different locations in the space around us.’

TRICKY TO TREAT – OR WORKING A TREAT?

Again, indicative of the variable forms of CRPS, its current treatments can be categorised under four main branches – pain medications; education and self-management; psychological support; and physical rehabilitation therapies which are vital to normalise sensation in the limb and improve function and mobility. But new, alternative research and therapies are continuing to emerge.

Dr Bultitude confirmed this, saying, ‘Our results show that people with CRPS are slower to process visual information that comes from the side of their environment where their painful limb is normally located. Since we used a test of vision, the slower processing can’t be because of changes in the limb itself, but must be due to the way the brain processes information.

‘We’re excited that these results can help propel us forward to developing new treatments for those affected by the condition.’