by Mr Charles Willis-Owen BM BCh MA(Hons) (Oxon) MFSEM FRCS (Tr&Orth)
Pain is defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage. Pain is a perception created by the brain in a response to a noxious stimulus. We know from various situations in life, probably most notably with optical illusions, that the brain can easily be tricked into perceiving something which is not there. Perceptions are merely our brains interpretation of reality and therefore, the link between a noxious stimulus and the perception of pain is not linear or predictable.
Well characterised pain pathways within the human body turn noxious stimuli in to the perception of pain, however exactly the same noxious stimulus can be perceived very differently by two different people. Take for example the ability of some individuals to walk across a bed of hot coals. For most human beings this would be agony, but for some people exactly the same noxious stimulus causes them no distress whatsoever. Similarly, the same individual, depending on the context of the stimulus, can perceive exactly the same noxious stimulus differently. Take, for example, the pain associated with being hit by a snowball thrown by one’s child versus being hit by an object thrown by an assailant and the latter is likely to be perceived as far more painful. This is because the brain colours
the stimulus with an interpretation of how damaging the noxious event was intended to be in order to alter the perceiver’s behaviour in the future.
There have been elegant scientific studies carried out to demonstrate this effect. Gray and Wegner in 2008 carried out an experiment using 48 volunteers who were connected to a device that could give electric shocks when a button was pressed. The volunteers each had a partner who would press the button which would deliver either an audible tone with no shock, or an audible tone with an electric shock of variable intensity. The catch was that when the partner pressed the button on some occasions a shock would be delivered but on other occasions just the audible tone would be delivered. The partner actually had no specific control over whether the volunteer received a shock but both the subject and the partner thought that they did so. The volunteer’s pain perception was rated after each shock. The findings of the study were that when shocks were delivered accidentally, they were perceived to be less painful than when shocks were
delivered deliberately and furthermore, after a number of accidental shocks the perceived pain got less and less, however, this was not observed with shocks that were delivered deliberately. This demonstrates the powerful effect of perceived intent on a person’s perception of pain and this is highly relevant to the medicolegal environment.
This means that for any given injury, a Claimant’s perception of pain, where there is a feeling of injustice, is likely to be more painful than if the injury were sustained by accident in a “patient” who feels no such sense of injustice and blames themselves. This may account for the well known phenomenon in medicine that work related injures and difficult to treat whereas sports injures tend to do better! Just as beauty is in the eye of the beholder, pain is in the brain of the perceiver. For medical experts who spend most of their days seeing patients with specific injuries, it can initially be confusing or misleading when one subsequently sees a Claimant with exactly the same injury who reports much greater levels of pain.
There is no clear way to measure pain objectively, or accurately assess how much pain the Claimant is really perceiving and therefore, one must be careful
in jumping to conclusions if a Claimant reports more pain than would be normally expected by a “patient”.
This means that it can be difficult for an expert to establish whether a Claimant is over reporting their pain for reasons of secondary gain and it can make establishing whether a Claimant is a reliable witness somewhat difficult.
As well as intensity, pain is described in terms of its character. Descriptions of the character of pain are remarkably consistent for any given noxious stimulus. For example, broken bones often are associated with a deep ache, pain with movement, and a sensation that something is out of place. It would be most unusual for somebody to perceive a fracture as a burning pain, or stinging pain. By the same token ligament injuries where the ligament is completely snapped off are often not particularly painful, but where ligaments are partially torn and the remaining fibres are under excessive tension they can be very painful indeed. Fractures that have failed to heal for some time (non-union) present with a constant low grade background ache, and pain particularly more prominent at night time. Pain caused by infection is often associated with warmth, a sensation of pressure, and a strong psychological component with an underlying sensation that some thing is not right. Pain associated with malignancy can present with similar features but with prominent night time pain and pain using the affected part of the body.
With a detailed knowledge of the various different types of musculoskeletal pain it is possible to establish whether a Claimant is misrepresenting their symptoms and thus, a skilful expert can still reach conclusions by listening carefully to what the Claimant describes to them.
In summary, pain is a perception, it is highly variable depending on the context, and differs both between individuals and within an individual depending on the surrounding circumstances. Pain perceptions do not always reflect reality and in general Claimants can be expected to suffer more pain for a given noxious stimulus than the patients that doctors see as part of their day-to-day practice.
The descriptors used for certain types of pain tend to be remarkably consistent between individuals and careful attention should be paid to these when assessing the musculoskeletal pain described by a Claimant. Musculoskeletal pain has a variety of causes and there are typical presentations and descriptions for each cause. The severity of any pain is quite variable but the nature of the pain is usually not. For this reason instructing an expert who has a deep and detailed understanding of these facts and of the various presentations of musculoskeletal pain can make a considerable difference to the opinions and conclusions reached.