Full list of topics 
Spacer
Spacer
Spacer
Spacer

Chronic PainArrow
Interview CP49  

Interview CP49

Sex: Male
Background:

Brief outline:


To watch or read an interview clip, click on the heading that interests you. Either a video,audio recording or text will open, depending on the clip
To close transcript boxes, click here
To print the interview’s text, click here
A doctor explains that after healing the sensitised pain system normally switches off but with chronic pain this doesn't happen.

 



One good way of explaining to people the sort of mechanism we are talking about with sensitisation in the nervous system would be the analogy of sunburn. You imagine you go off to Spain on your holiday and you're sitting on the balcony of your hotel, reading a really good book and you totally forget that you've gone from Britain to Spain and it's really hot and the sun's beating down and your right shoulder is in the sun. Your left shoulder is in the shade. Your right shoulder gets badly sunburned. 

The next day you take a shower. Well what's going to happen? Your left shoulder which is normal it's just going to be fine. It's just going to be warm water. But your right shoulder, the one that was sunburnt, it's going to be agony. Now why is that when it's the same stimulus on the two shoulders? Now what's happening here is that the nerves that go to this shoulder have been changed by nasty chemicals released by the damage to the skin. It isn't the damage to the skin itself that causes the sensitisation and if you think, that's logical. 

Damaging things doesn't make them work better, it's a result of that damage. When you damage the skin, nasty chemicals called inflammatory mediators, one of them is prostaglandin gets out from all these tissues onto the nerves and that sensitises the nerves and for example brings down the threshold at which that fibre would fire for pain. Normally this would be about 45 degrees. So on this shoulder you would have normal skin with normal nerve endings which would tell you it's painful at 45 degrees. On this shoulder the threshold might have gone down to 38 degrees. 

So you go on a shower at 40 degrees, this shoulder is 5 degrees below the pain threshold, that's fine. But this shoulder at 40 degrees that water is 2 degrees above the pain threshold so it says “That's very painful”. The lesson here is the stimulus is the same. It's the nervous system that's changed and whether or not someone feels pain doesn't just depend on the stimulus. It depends on the state of your nervous system as well. 

If we pursue the sunburn analogy a little further you imagine the day after you've had the sunburn things are at their worst. You've damaged the skin, everything is all wound up. Over the next few days things gradually heal. The skin will heal and gradually come back to normal, and the nervous system will also re-adjust itself gradually back to normal, so that after a few days that change in threshold which you'll remember came down from about 45 to maybe 38 degrees, re-adjusts back up again until it's at 45 degrees. 

The problem is that we think in chronic pain some people don't re-adjust after the injury so their nervous system is left in that sensitised state. Their thresholds are permanently lowered and they also get amplification, like turning up a volume control within the nervous system, so the whole thing is made worse by this sensitisation and amplification of the problem within the nervous system. 

And we believe that in many people who suffer chronic pain after injuries and maybe after other sorts of illnesses, like viral illnesses, it may be that the nervous system has changed and everything's been stirred up and sensitised but instead of re-adjusting to normal after a few days after healing takes place, they are left with this chronically sensitised nervous system that gives them a chronic pain syndrome.
Support our work

healthtalkonline.org - Teaching and Learning

Mail to a friend

Send