“The phenomena of pain belong to that borderline between the body and the soul about which it is so delightful to speculate from the comfort of an armchair but which offers such formidable obstacles to scientific enquiry.” (J. H. Kellgren, 1948)
Here are three relatively unknown or frequently ignored aspects of pain which however are commonly evident in clinical practice:
- The presence or intensity of pain is not well related to medical diagnostic findings (x-ray, scanning, blood tests). Thus two people of the same age, sex and similar general physical condition, with similar spinal x-rays or scans, can have vastly different degrees of spinal pain, from virtually none, to virtually unbearable.
- Contrary to what many osteopaths and chiropractors like to think musculoskeletal pain in the general population is not well related to postural features, bodily asymmetries or load-bearing. Some people are highly sensitive to minute sources of pain, others are unaffected by potentially large ones.
- To even begin to understand such aspects as these, one must take into account a number of phenomena:
The multifactorial nature of pain
Except in the simplest circumstances (e.g. you cut yourself, you drop a large rock on your foot, etc.), the question, “What is the cause of my pain?” has no clear-cut answer. The experience of pain is a final result of numerous inputs from both past and present. These may include, just for example: your constitution and general physical and mental condition; the accumulation of trauma, physical and emotional, and its effect in sensitising the nervous system; energy levels and fatigueability; biochemical balance and nutritional factors; stressful life events and situations, and your ability and resources to cope with them; personality traits and psycho-emotional factors; your knowledge, beliefs and past experiences; the existence of musculoskeletal pathology like arthritis or slipped disks; and yes, also “mechanical” triggers like actual physical insult and the soundness of the physical structure of your body to absorb it. But for any realistic appraisal of pain it is essential to realise that the actual triggering event is in many cases by no means the most important input in all of this that determines the experience of pain.
The neural network
All of this information is processed and interpreted by the central nervous system (brain and spinal cord). Here, in the course of your life a “virtual” blueprint is born and develops, partly from your genes, partly from your experiences, which determines how you will interpret and handle noxious impulses. It is called the neural network. Will you interpret the slightest abnormal sensation “catastrophically” and experience extreme pain and anxiety? Will you ignore painful signals, brush them aside and carry on as normal? Or will your system discriminate the important from the insignificant correctly most of the time, assigning appropriate levels of pain and behaviour to each occasion? These questions are not answered by you entirely voluntarily, but by your neural network working unbeknown to you in the background.
Nociception is the name given to the activation of specialised nerve endings which cause “pain” signals to be transmitted towards the spinal cord and brain. It is an unconscious process: at this stage pain is not necessarily felt, as these signals are just the raw information, unprocessed as yet by the brain. These specialised nerve endings are activated by stimuli such as mechanical loading, tension, pressure, stretching, shock, or abrasion, real or potential tissue damage, chemical irritation and heat. Nociceptors are being activated in our bodies all the time and we are largely unaware of this. This is because not all potentially damaging stimuli are in fact important: the brain has to make this distinction and act accordingly (as explained in “the neural network” above), which in most instances is to ignore the stimuli.
Pain sensitivity and tollerance
People talk about having a high or low “pain threshold”, but in fact there are two different pain thresholds: sensitivity and tolerance. Pain sensitivity is how much one perceives pain. Pain tolerance is how much one reacts to it. You could, for example, have high pain sensitivity and low pain tolerance, or vice versa. Pain sensitivity and tolerance are modified by all of the factors listed in “the neural network” above. In some circumstances, due to the summation of numerous factors, some of which have been listed, people can become highly sensitised to the extent that stimuli only very slightly more intense than normal cause pain. (This is called “central sensitisation”, as it is the central nervous system that is “sensitised”). Often, anxiety follows as the person understandably, but wrongly, attributes the pain to injury or illness.
Psychological aspects of pain
In all of us psychological influences have an enormous influence on pain (its occurrence, characteristics and intensity) and our behavioural response to it. These include your personality traits, general mental condition, past and present emotional trauma, stressful life events and situations, and your ability and resources to cope with them, mood, knowledge, beliefs and past experiences, the presence of anxiety or depression. This much is known fact. And yet, when it is suggested that a person’s pain may have important psychological influences requiring specialised help, there is frequently an astonishing level of resistance to the idea. The person thinks psychologists are for people who are mentally ill. “No”, they object, “my pain is real”.
This, however, is meaningless: all pain is a subjective experience, and all pain is real to the sufferer (except in those rare cases when people actually fake it). Whether its origin is mostly physical or mostly psychological, it is equally real.
The significance of pain
It is clearly likely that pain evolved in response to injury and illness in order to determine life-saving behavioural responses such as withdrawal from the source of pain, or seeking help. These are normal (functional) responses. However, pain does not always mean there is injury or illness. In certain common circumstances, people’s response to pain may become poorly adapted (dysfunctional). This happens for example in central sensitisation (see above), “neuropathic” pain, and in some cases of chronic pain.
In central sensitisation pain results from insignificant stimuli, and is erroneously believed to be from some injury or illness. In neuropathic pain, “sensitised” nerves spontaneously produce painful sensations even long after the original reasons for the pain reaction (e.g. a physical injury) no longer exist.
In chronic pain, the pain can be maintained by inappropriate behavioural responses such as excessive avoidance of activity, excessive focusing on the pain, or unconsciously soliciting secondary benefits from one’s symptoms such as sympathy or relief from responsibilities or demands (e.g. sexual). The obtaining of these benefits unconsciously reinforces the pain and the behaviour.
In essence, in these situations, the fault is not so much with the body’s structure itself, but with the body’s responses to stimuli, or the person’s responses to pain. In some cases the individual roles of the whole family may become so defined by one family member’s illness that a self-maintaining system evolves. These phenomena are much more common than is generally recognised.