Reconceptualisation of Pain
Just for the record….
Pain does not provide a reliable measure of tissue state.
Pain is modulated by many factors from across somatic, psychological and social domains.
The relationship between pain and tissue state is less predictable as pain persists.
Pain can be conceptualised as a conscious correlate of the implicit perception that tissue is in danger.
Returning to a theme we have discussed before (pain and the brain) the above are indisputable facts derived from scientific evidence produced in the emerging field of Multisensory Integration. This is a field of endeavour dedicated to understanding how the brain synthesises information from different senses to coordinate an appropriate coherent response. This is fertile ground for physiotherapists / clinicians treating pain disorders and dictates that we reconceptualise our model of pain and the framework for which we provide patient care. Hint: the psychosocial model is only part of this.
At the forefront of this research is physiotherapist Lorimer Moseley, Professor of Clinical Neurosciences and Chair in Physiotherapy at the University of South Australia, Adelaide. He has written 75 papers and published in all the prestigious Pain, Neuroscience and Physiotherapy journals and has a list of awards too long to mention here.
We recently caught up at a seminar he conducted entitled “Pain and the Performing Brain”. As the title suggests the focus of the day was to explore the multi-modal factors which influence pain perception and how these impact on performance. Many concepts were presented and we were fortunate to extract some key take home messages in an interview I recorded which is posted below. Click here if you can’t wait.
Lorimer’s team have proposed a theoretical construct termed the “Cortical Body Matrix” to integrate the broad spectrum of sensory and perceptual factors which have been shown to influence the pain experience. Readers may remember the neuromatrix concept proposed by Ronald Melzack some years ago in which the concept of an individual “neural signature” was proposed. I had the luxury of hearing the man himself explain how this concept evolved. In summary, developments in brain imaging demonstrated diffuse, variable and sometimes disparate cortical activity in response to painful stimuli – not explained by a “pain centre” which has now well and truly been put to bed (ie: it can’t be cut out or ablated by procedures!).
My admittedly limited understanding of the cortical body matrix concept is that it expands the envelope of sensory perception by incorporating elements of somatic, spatial and cortical processing into a paradigm which can be manipulated for clinical purposes.
Previous posts on Lorimer’s excellent www.BodyinMind.org site discuss aspects of sensory conflict which can be used to “break-up associations” in the neuronal tag which combine to output the pain experience. Some of the strategies involve:
Access Strategies to Cortical Body Matrix
Conflicting tactile /Proprioceptive /visual cues.
Visual distortion (magnification of effected part)
Image recognition (body part aspects and orientation)
As clinicians we are familiar with symptom reports of:
Swelling (when not visibly evident),
Heaviness (when identical size)
Localisation discrepancy (when obviously present)
Thermal sensory disturbance (with similar temperature)
Dysaesthesia (exploding, crushing, non-responsive, sluggish)
These can be coupled with…
Blood flow changes
Spatial processing deficits
Data was presented outlining the mechanisms behind these sensations with particular emphasis on the dynamic and contextual variations which occur across the spectrum of normal environmental conditions to ultimately modulate the pain experience.
This information forces us to move away from the modality specific – receptor pathway – sensory cortex model of nociception to integrate domains of patient perception, prior experience, context, perceived threat, cognitive and emotive processes as parts of a neuronal matrix which ultimately outputs pain sensation.
I would also add factors such patient satisfaction, confidence in the clinician, perceptions of empathy, clinician credibility, body language, communication skills, personality, commitment to help, therapeutic environment as other, parallel sensory input’s – at the risk of sounding a bit “new age-y”.
I don’t think we can continue to ignore (or at least not talk about) these factors even if they don’t lend themselves to such rigorous scrutiny as the neurosciences and cause some ( discomfort as we saw here ) when we do.
To paraphrase Charles Spence (The Handbook of Multisensory Processes).
From the existing body of research there can be no doubt that our senses are designed to function in concert and that our brains are organised to use the information derived from multi-sensory channels cooperatively to enhance rapid detection, identification and response. Even experiences that appear to be modality specific have most likely been influenced by other sensory input whether perceptible or sub-conscious.
This raises questions regarding the hierarchy of information processing and the underlying mechanisms of excitation / inhibition within the brain.
How does the brain weigh up the different input it receives from multi-sensory stimuli to produce a final perceptual output / experience?
What factors combine to determine the most dominant, pervasive sensory cue in a given context?
What factors influence the dynamic nature of this response?
These are questions which Lorimer’s team and other neuroscientists are striving to unravel.
I was fortunate to interview Lorimer after his workshop and I invite you to listen to the audio below.
Prof Lorimer Moseley Interview
Here are some of the issues we discussed
– the transition from disillusionment with physiotherapy to subsequent rejuvenation in the path subsequently taken.
– the use of visual illusions to illustrate discrepancies between sensation and perception.
– calls for classification of pain based on mechanisms rather than structure or symptoms.
– improvements in technology.
– proprioceptive deficiencies in low back pain patients and perceptual impairments of painful body parts.
– the clinical tools such as. “Explain pain” and the “Recognize” program
– evidence-based practice, the therapeutic relationship, outcome measures and perceptual components of human interaction – Where does this leave the double-blind clinical trial?
What a treat, got the intra-cellular juices flowing?
Enjoy the Clinical Challenge
DavidGHTime Code(s): nc nc nc nc nc nc