The pain revolution

A revolution in the understanding of pain and its underlying mechanisms is occurring, changing our views of pain and disability and pointing us towards new treatments for this very complex problem.

Our understanding of pain has undergone a slow improvement since the time of Descartes, with many long periods without new ideas or investigation.

However, in the last 35-40 years there has been an explosion both in research and ideas. This has lead to many new methods of treating pain and an altogether new vision of what pain is and how it is produced.

Descartes, in the seventeenth century, achieved a major revolution in thought by arguing that the (then new) methods of science could be used to study the human body. He proposed that the human body was a form of machine and so could be studied like other phenomena.

Specificity theory

Under Descartes’ influence, the scientific search for how pain was conducted culminated in the specificity theory, which held sway until the middle of the twentieth century.

This viewed pain as a simple system where an input of one kind travelled along special nerves for that kind of input, terminating in specific areas of brain again receptive to that input. The input which went in was thought to be what was felt by the brain. This lead to various kinds of therapy, including the cutting of nerve pathways to try and abolish chronic pain.

This theory was clearly wrong to anyone who studied patients in pain, for it implied that if there was no injury to account for the pain then it could not exist. Therefore, patients who did complain of pain in those circumstances were mentally unwell.

Pattern theory

Pattern theory evolved from these ideas and is not covered here (but will be in more detail in my forthcoming ebook), and while it did not lead to any startling discoveries, it set the scene for the emergence of the gate control theory in 1965. This theory has had enormous influence.

Gate control theory

Ronald Melzack and Patrick Wall published their paper on the gate control theory of pain in 1965 and were astonished at the vigour of the response.

A new way of thinking about a subject can sometimes release a huge wave of research and new ideas. Indeed, a theory may not be much use in explaining the world unless it does this.

Gate theory is based on several propositions:

• The transmission of impulses from the body into the central nervous system is “gated” ( altered, changed, modulated) in the spinal cord.
• Gating is affected by the degree of activity in the large diameter and the small diameter nerve fibres. Impulses along the larger fibres tends to block pain transmission (close the gates) and more activity in the smaller fibres tends to facilitate transmission (open the gates).
• This gating mechanism in the spinal cord is affected by descending impulses from the brain.
• Large fibres may activate specific cognitive (thinking, analysing) processes in the brain, which then influence the gate by down going impulse transmission.
• When the pain output to the brain reaches a certain level it activates the action system, in other words we change our behaviour to do something about the pain.

So what does this mean?

Gate theory allows for the dynamic (constantly changing) role of the brain in pain processes. Psychological aspects of pain are now seen as integral parts of the process and not just reactions to pain. This has opened the way for psychological approaches to be used for pain treatment and management.

Simplistic treatments such as cutting nerve pathways (which often made the pain worse) have been replaced by more realistic treatments, with physiotherapists and transcutaneous nerve stimulation (TENS) brought into the picture.

What’s beyond the Gate?

The fundamental principles of gate theory have remained intact over the years since it was introduced, with much of the detail filled in. However, the next challenge is to understand the workings of the brain.

It’s as if there have been three distinct stages of understanding about the mechanisms of pain and how it is felt:

1. Concentration on the areas of injury or damage, with little else relevant
2. Realising the spinal cord (central nervous system) has an important role
3. Realising that the brain has an important role in how we feel pain.

We seem to be at the start of No.3 now…….more another time…or read on below….