Sensible advice for aches, pains & injuries


Telescopes, not brain scanners: some musings on the relationship between pain and tissue damage

Paul Ingraham ARCHIVEDMicroblog posts are archived and rarely updated. In contrast, most long-form articles on are updated regularly over the years.

Everything we feel and perceive is Brain-Made®: surprisingly detailed mental models of what we expect to perceive, cleverly compared to information gathered by nerve endings about things like the taste of nectarines, the sound of a bumblebee, or a nebula glimpsed through a telescope.

Or back pain! But pain is more volatile than other sensations, more “open to interpretation” than bumblebee buzzings or fruit flavours.

Is a nebula out there? Or is it just a mirage between your ears? Trick question! (Running Chicken Nebula, photo by Martin Pugh)

Crucially, pain is also not subject to independent verification. Everyone can more or less agree that nectarines are delicious and bumblee buzzings are at a lower pitch than smaller bees, but no one can tell you anything about your back pain, and your brain has an extraordinary ability to warp it. Your pain is like a funhouse mirror reflection of what’s going on in the flesh.

These are clinically important facts about how pain works, and I’ve written a lot about them. They are so important that, in many discussions, they have begun to drown out the boring-but-basic fact that tissue trouble still usually leads directly to pain. Pain and tissue damage are positively and strongly correlated. Of course.

Pain perception is subject to strong distortions, but these are mostly rare and hallucinatory. We can make pain up out of thin air, but we rarely do. And we can have painless trauma, but we rarely do. There are famous and fascinating examples of such cases, but they are famous because they are somewhat exotic. Pain perception may be volatile, particularly with complex and chronic cases, but it’s still mostly a consistent and predictable warning system about tissue danger.

It has to be reliable: that’s why it exists.

Unexplained chronic pain

This is where the pain science rubber hits the practical road. Unexplained chronic pain is common, and the relationship between pain and tissue damage often gets weirder and murkier as time goes on, which can get totally confounding for patients and professionals. We need to simplify. When there’s no known damage, there are two possibilities:

  1. either there is tissue insult (a source of nociception) that just can’t be identified (surprisingly common I think), or
  2. the relationship between tissue insult and pain has broken down (also quite common).

And these scenarios are not mutually exclusive: you can have both tissue damage and a wonky, disproportionate relationship to pain.

Point one is an important source of reassurance for many people. I’m speaking both professionally and personally here, because I suffered exactly that fate in the last year: a persistent pain with no apparent cause, so much so that I was told by a few professionals that my only problem was “pain dysfunction,” or experiencing pain without tissue damage. But then, rather better late than never, the %#!!$& source was found and removed and that was the end of my pain. Ta da!

So I suffered a year of serious chronic pain with no apparent source that absolutely was positively, strongly correlated with a tissue insult. Just a sneaky one!

I know similar things have happened to plenty of other people too.

Is it all in your head?

Sure, technically, all pain is indeed all in your head…but so are those nectarines, bumblebees, and nebulae. That is the nature of consciousness. Most experiences have strong roots in the world. Or your body.

Everything is in the brain, but when we want to learn about the universe, we look through telescopes, not brain scanners.

~Dr. Rob Tarzwell of One-Minute Medical School. (Ironically, when Dr. Rob wants to learn about people, he looks at them with a brain scanner.)

If you want to know about nectarines, you mostly study nectarines, not brains. If you want to know about that nebula, you use a telescope, not a brain scanner. And if you want to know how back pain works, you are going to have to study back injuries and pathologies and the creative and colourful ways that brains play with pain perception. But brains are still usually playing with the perception of something that is actually going on in the “world” of your back, in your tissues.

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