Sensitisation is a term that regularly refers to an increase in sensitivity. What role does sensitisation play in chronic pain and how can you counteract this process?
Two types of Sensitisation
Sensitisation makes the nervous system more sensitive, allowing you to experience pain faster and/or more intense. There are two forms of sensitisation: Peripheral and central sensitisation. Both forms can play a role in experiencing (severe) pain.
Peripheral Sensitisation - ‘the outside’ becomes more sensitive
Peripheral means literally on the edges, or outside. The pain spreads throughout the body, but especially on the outside (e.g. the skin) we have numerous cells that can transmit stimuli. As some kinds of sensors, these cells can perceive pressure, heat and chemicals in the body. Each cell needs a certain amount of stimulation to send a signal, which is called the threshold value. We also call these stimuli warning signals in case of pain.
With peripheral sensitisation, two things can happen: The threshold is lowered, or the cells fire signals in a different way. As a result, that part of the body sends more stimuli travelling faster to the brain. And the increasing amount of stimuli can increase the change of pain. For example, when you have been in the sun for too long, you get a sunburn. The skin is more sensitive to touch during the following days and it will also hurt more. It was previously thought that peripheral sensitivity caused chronic pain. Insights about this view have changed, and central sensitisation now plays a more important role in pain theories.
Central Sensitisation - ‘the inside’ becomes more sensitive
Central sensitisation increases the sensitivity of the body’s nervous system. It usually involves the spinal cord and the brain. In the spinal cord, all the nerves come together and all the stimuli go over a kind of highway to the brain. Both parts of the nervous system play a role in central sensitisation.
It is said in the spinal cord that there are ‘pain gates’ that let in or stop the stimuli from the rest of the body. It is as if in several places on the spinal cord there is a kind of mini-brain that can decide for itself how many stimuli are allowed through. With central sensitisation, these gates allow stimuli through more easily, which can then travel to the brain.
The brain is the second part that plays a role in central sensitisation. In modern pain theory, the brain is the most important place. With central sensitisation, the brain becomes more sensitive to the incoming stimuli. The pain alarm system reacts much more sensitively to the incoming stimuli than you would expect. This process of hypersensitivity of the pain alarm system is sometimes referred to as ‘cortical reorganisation’. Cortical reorganisation means that the brain adapts and develops, in the case of pain in such a way that the brain reacts much more actively to chronic pain. In the increase in sensitivity of the brain, we now know that what we think, feel and focus our attention on plays an important role. And that negative thoughts and feelings can even cause that sensitivity to increase. So in total, three places can contribute to chronic pain. In the end, the brain always (unconsciously) decides to create the pain. Therefore the brain has the ‘main role’ in chronic pain.
So in total there are three places that can play a role in chronic pain. In the end, the brain always (unconsciously) decides to create the pain. Therefore the brain has the ‘main role’ in chronic pain.
What can be done about sensitisation?
At Reducept we are fully engaged in reversing sensitisation. We do this mainly by focusing on central sensitisation. By doing exercises that positively influence your thinking, feeling, attention and behaviour, new pathways are created in the brain. Pathways that will hopefully replace the ‘pain paths’ that are now there in time and become stronger and stronger. It will also further lead to cortical reorganisation, but in this case a positive reorganisation that ensures the pain is given less space.