Pain is a construct | #pain #neuroscience

Pain is a construct that is unique to our own brain hence the individual nature of the experience. By definition, according to the International Association for the Study of Pain (IASP), pain is a sensory and emotional experience. Both sensations and emotions are also brain constructs, in other words our brains create the experience to be played out via the body. In essence this is why pain is so influenced by our mental state and attentional processes: most patients I talk to will describe an increase in pain at times of stress (stress can also reduce pain; stress induced analgesia–this being the case when something else is more salient at the time) and when they are unable to distract themselves.

Our language, pain descriptions, our inner voice are all brain constructs that emerge as are the movements we make–more on this soon

Pain emerges from the body tissues, or in the case of phantom limb pain (PLP) in the space that was once occupied. A great deal has been learned from PLP (see video below with VS Ramachandran talking about ‘The Tell-Tale Brain’) including the fact that pain cannot be created by the tissues as they are clearly not in existence, however the cortical representation (the somatosensory maps, motor maps etc) remain in the brain, igniting under certain circumstances to construct a pain experience via the salient network. The salient network exists to detect differences in physiological activity and respond accordingly, perhaps with protection in mind that would include pain in the area of the body deemed under threat. For pain is about ‘threat’. When the brain receives contextual information suggestive of threat, it must scrutinise this data and compare to what it knows before responding. On there being a perception of threat, regardless of the reality (eg/ light brushing, a simple movement, watching someone else move, thinking about movement–some readers will know only too well how the latter cues can trigger pain), the brain will protect, drive attention and motivate action via the experience of pain in the body.

Our individual belief system, our resilience at the time, our mood at the time and the context will all impact upon the pain perception and what happens next. The construct of pain, the common denominator being that it hurts in the body, is varied in its volume, location and pattern in many cases when the sensitivity has persisted for some time. In other cases, the pain can have a mechanical pattern (not implying that a structure is out of place and can be put back by manual therapy) meaning that certain movements or touch can hurt and be more predictable. However, the bottom line remains that the brain must perceive a threat.

On the positive side, although complex and modulated at many levels, pain is changeable. There are many access routes into changing the experience and a person’s belief that they can gain increasing control over their pain to be able to reduce the feeling and train to decrease sensitivity. The newer brain focused therapies all aim to do this by targeting changes and adaptations in the central nervous system, although I would argue that we are seeking to change the processing of the danger signals with any of the techniques used in the clinic. Light manual techniques that result in pain relief do not ‘put discs back’ but they can alter the threat value and hence change guarding, reflexive protection and the perception of touch leading to relief and ease of movement. We just have to think carefully about which techniques and strategies are most appropriate at the time, how we set the environment and context so that the brain is acceptant of the treatment and responds by reducing activity in the pain matrix or representation.

Undoubtedly treating chronic pain is complex but if we think about the pain mechanisms and the influences upon pain (stress, anxiety, mood, exercise, movement, sleep etc), we can build a comprehensive programme to address the different dimensions: physical, cognitive and emotional. Let us treat the tissues with care to nourish and promote healthy movement, but to do this effectively we have to think about the brain and how it is constructing the reality of the patient and get it onside.

Specialist Pain Physio Clinics, London

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