'I chewed off half my tongue': Why pain is a necessity
What would a world without pain be like? It may sound ideal, but it can cause extreme difficulties.
It is the world Steve Pete inhabits. Born in Washington State, US, with the genetic disorder congenital analgesia, he is incapable of feeling physical pain.
If he stubs his toe it doesn't throb, there is no need for anaesthetic when having teeth removed and he has never had a headache in his life.
But pain is a vital warning system for our bodies - it tells us when we are doing something harmful and need to stop, and it alerts us that something is wrong and we need to investigate, something Steve has learnt the hard way.'Constant plaster casts'
Steve's condition first came to light when he was a teething toddler and chewed off part of his tongue without noticing.
It was a constant problem when he was growing up.
He admits that he and his brother, who has the same genetic condition, didn't have the same restraining influence that other children did.
"Boys will always be boys," he said. "They get into mischief, but we just kind of pushed it to the limit."
It meant his early childhood was marked by constant plaster casts and a lot of missed school due to frequent stays in hospital.
Now in his thirties and married with children of his own, who did not inherit the condition, Steve is starting to pay the price of his pain-free existence.
"As children if we were to break a leg we would continue using that leg even though we were in a cast, and by not giving it time to heal it would heal improperly.
"And you incur so many injuries as a child that as an adult you start to deal with the repercussions of all those injuries, like having arthritis starting to set into your joints, and mobility issues."
Steve is now taking part in a study into his condition, in the hope that a better understanding of his genetic mutation can help those for whom pain is an all too present problem.
His is one of four personal takes on pain featured in a new exhibition at the Science Museum in London.
Pain Less explores the growing insight science is gaining into the complexities of this very basic human sensory experience and possible therapies, from virtual reality trickery to spider venom.
End Quote Peter King Phantom limb patient
On a scale of one to 10, my pain is around eight.”
The flip side of the pain coin is Peter King, another extraordinary story featured in the museum's exhibition.
While Steve never suffers pain, Peter is never without it. He feels it in a limb that is no longer there - his left arm that was amputated 20 years ago.
Crippled on his left side by polio at the age of two, Peter had never had much function in the arm, only pain.
Following an additional injury when he was 50, the decision was taken to amputate above the elbow joint - an operation that he hoped would also cure his pain.Phantom feelings
But while Peter's arm may be physically absent, the sensation of it remains.
Peter has a phantom limb, and like many who experience the ghost of a lost extremity, it does not move freely; rather his is fixed in a painful position and he has shooting burning pains down the arm and the feeling that his wrist is circled by a tight strap.
"On a scale of one to 10" he said, "my pain is around eight".
The pain and sensation experienced in phantom limbs, from nerves that are no longer there, has fascinated scientists for decades and for many sufferers like Peter pain killers fail to work.
But Peter has been testing a new technique using a computerised movement recognition kinnect system and virtual reality headset to trick his mind into thinking that a flipped image of his right arm is really his left arm, moving and performing tasks.
When he moves his right, the left arm responds too, and he admits his brain is fooled.
"After just a few minutes my phantom left arm, which is normally just lying at my side, starts to feel like it is moving up to touch things because in my headset I can see my left arm working".
And just 30-40 minutes of exercises brings a release to his clenched hand and drops his pain levels down to one or two out of 10.
But people with unusual relationships with pain like Steve Pete and Peter King, contribute more to the topic than interesting stories.
By understanding what has gone wrong in them scientists are starting to unravel the complexities of the relationship between the hard-wiring of our pain circuits and the influence of our brains in experiencing and processing pain.
- Every square centimetre of your skin contains around 15 receptors for pressure.
- There are six sensors for cold and one for warmth.
- But one square centimetre of skin has 200 receptors for pain.
It is more than just a set of wiring - it is also a measure of suffering experienced, and the difficulty scientists and doctors have is that this is a very subjective and individual matter.
Different people can be exposed to the same level of stimuli and yet report experiencing different degrees of pain - ie some people appear to have a higher pain threshold than others.
There is even variation within the same individual.
Pain has a definite emotional component. Happiness, sadness, being in love, having your attention distracted can all alter pain perception substantially, making it a difficult puzzle to solve, but one that is getting increasing attention from the research community.