What is Central Sensitisation?
Normally, when you have an acute injury to your tissue, the pain you experience is proportional to the severity of the injury. While there are other factors – for example, if you are grumpy due to an argument with your partner, it may hurt more when you bump your head than if you are in a great mood because you just got some good news – but on the whole, the amount of pain is related to how badly you have injured yourself. If you stub your toe, it may hurt quite a bit at the time, but the pain quickly fades and you forget about it.
Chronic pain is different. When the initial insult has long healed, but pain persists, there may be a process called central sensitisation going on. In central sensitisation, the nerves in the central nervous system (your brain and spinal cord) are ‘’mis-reading’’ the state of the tissues. They are thinking there is something serious going on when there isn’t – and because of their confusion, they are sending way too many messages, way too loud. It is like a castle that thinks it’s being attacked because there was a bump in the night – and the soldiers have been pulled out of their beds and are madly getting organised for a battle, and yelling at all the other soldiers to get themselves ready. Too much activity for no practical purpose!
Another way of looking at it is to look at nerve activity in the central nervous system as noise. In central sensitisation, the volume dial has been bumped, so even minor noises are heard as incredibly loud. This is interpreted as something very serious going on, even though the real situation is much more minor.
If you have chronic vulvar pain with no known medical cause, it may be that the volume dial has been bumped, and you are hearing every little thing that goes on in the vulva. The fault doesn’t lie with your vulvar tissue; it lies with the central nervous system, which has itself confused. This is why specific antidepressant medications such as amitriptyline are sometimes prescribed for chronic pain syndromes. It is not because the problem is ‘’all in your head’’ – but in another way, I guess you could say that a big part of the problem actually IS all in your head (and spinal cord)! These medications aim to ‘’quieten down’’ the nerve messages, which have been ‘’turned up’’ while travelling up the spinal cord.
Sticking with the sensory analogies, you can think of the sensations you experience visually. What should normally be very tiny or hardly noticeable is being magnified by the brain and spinal cord. It is as though your brain and spinal cord is looking down the wrong end of a set of binoculars – and everything seems much larger and more significant than it really is. This is central sensitisation, and it is a known process that has been measured and documented in the central nervous systems of people with chronic pelvic pain, vulvodynia, and interstitial cystitis.