Pain without injury?
I have a read of this case, reported in the British Medical Journal, where a builder was brought into hospital crying out in agony after landing on a 15 cm nail:
A builder aged 29 came to the accident and emergency department having jumped down on to a 15 cm nail. As the smallest movement of the nail was painful he was sedated with fentanyl and midazolam. The nail was then pulled out from below. When his boot was removed a miraculous cure appeared to have taken place. Despite entering proximal to the steel toecap the nail had penetrated between the toes: the foot was entirely uninjured.
A painful ‘optical-illusion’
So what is going on here? No miraculous cure of course, just no injury! Perhaps your immediate thought is that the man was a bit mad or at least a bit of a drama queen? Well, no. In similar circumstances we may all have done exactly the same. In the moment he stepped on the nail, he looked down, saw it had penetrated his boot and his brain came to the logical conclusion that he was in real danger, raising the alarm/pain signal to force him to STOP and avoid further harm. The pain was very real, even if the injury wasn’t.
The brain always dictates whether we feel pain or not. Simply, we cannot feel pain without the brain. But we can feel pain in a leg, for example, without the leg. Have you heard of phantom limb pain? Here, the leg, and its relationship to the body, is represented as a virtual body in the brain. As the pain is centrally generated (in the brain) the person can still feel very real pain even after the limb has gone.
What turns on the pain-signal?
With any stimulus the brain will always make an assessment “How dangerous is this really?” If it arrives at the conclusion that you are in danger, then it will turn on the pain signal to alert you to act on this information. In the builder’s case, based on all available information to it, the brain made an evaluation that the foot was badly hurt and turned the pain signal on as protection.
Commonly, pain is an important protective mechanism that alerts us to actual or potential damage. In some cases not having pain would be life threatening e.g. if we didn’t act on the pain felt from an appendicitis or a heart attack the results could be fatal. Or more simply, if we fall and twist an ankle the resulting pain enforces a short period of relative rest to enable healing.
But in many cases pain does not reflect damage at the site of pain. This is because the brain responds to stimuli from a wide range of inputs – not just from the physical site of the pain. Many factors will influence the brain to initiate pain or not, such as our past experience, previous injury, current and/or past stress. Context is also hugely important. Picture these two scenarios:
Scene one – you fall over in the street and you bump your knee heavily.
Scene two – the same happens but this time you are in the middle of the road and a bus is heading towards you.
I think you would agree that the pain experience in these two situations will almost certainly be very different. Most likely in scene two little to no pain will be felt because in that moment the greater threat is the bus hurtling towards you. It would be unhelpful for the brain to initiate pain when in that moment it is far more important to get out of the way of the bus.
Pain is complex
The main point of this post is to introduce the fact that pain is a complex (and fascinating) phenomenon. It can be influenced by any number of factors and it certainly isn’t a good predictor of damage, especially when it persists for many weeks and months. But we’ll save persistent pain for a future blog post!