The discoveries of neuroscientists relating to pain, its causes, treatment and psychological implications, are the subject of a fascinating documentary by Horizon, entitled "The Secret World of Pain". Billions of neurons transmit messages from body to brain, enabling our pain system to work. Pain is essential to our survival; those who do not feel pain are vulnerable to injuries of which they are unaware. The lack of perception of pain is due to a faulty gene called SCN9A, which inhibits the pain pathways to the cortex where pain is perceived.
- A little girl read a story about a child who jumped off a building, using her umbrella as a parachute. So she tried this several times from a 3 m high garage, landing on cement on her knees. Feeling no pain, only later did she develop a severe infection as a result of her landings.
- The same child would sit in a kneeling position on a radiator, until her knees were burnt.
- Members of an Italian family were resistant to temperature. One reported swimming in the sea even at 10 or 11 degrees, another ate piping hot food, blistering her mouth, and a young girl could run on hot sand.
- A grandmother fell off an escalator. Surgeons confirmed she had not broken her ankle, although she had broken it twice previously, but never noticed.
- Her grandson fell off his bike. Six months later he couldn’t bend his arm and found that it was broken.
Their story adds weight to geneticist, Dr. John Wood’s, belief that the reasons we feel pain differently lie in our DNA and can be inherited – and the cause is an imperfect gene affecting the pain pathway to the cortex.
Pain is Subjective
Prof. Irene Tracey of University College, London, says that pain is entirely subjective. Neither pain nor pleasure exists, but is generated in the brain. Pain can change, according to environment, context and emotional state. In tests, students were shown a simple triangle, and a low-level pain stimulus was administered which the subjects rated 3/10. Then they were shown a square and were given a higher pain stimulus, rated at 7/10.
Finally, they were presented with the square, but this time at the low-level stimulus formerly associated with the triangle. They rated their pain as 5/10. This two-point increase demonstrates, says Prof. Tracey, that anxiety increases perception of pain. Depression, sadness, happiness, attitude; all of these can be instrumental in affecting the level of pain perceived. Imaging can show the parts of the brain instrumental in the process.
Amputation without Pain
Jonathan Metz performed an unthinkable act on his own body. His arm became trapped between a furnace’s heating vents in the basement of his house. He tried to free himself, shouting for help. After 24 hours he came to a terrible decision – to cut off his arm. Yet he felt no pain, only mild discomfort, while watching his flesh, bone and arteries being severed. His body managed to control the pain, even though he felt severe emotional trauma at having his head so close to the exposed end of his severed arm.
The extremity of his trauma had stimulated areas in Jonathan’s brain, for example, decision-making, emotion and attention, to send messages to the brain stem blocking the pain signals from the cortex and setting off a reaction that flooded his brain with natural painkillers.
Influence of Early-life Pain Experiences
The problem for some people is believed to be early life experiences. Premature babies often suffer painful procedures that are abnormally intense. Clinically required tests involving pricking the baby’s heel were carried out on full-term and premature babies. The results were monitored so brain activity could be recorded. Premature babies were found to be more sensitive to pain than full-term babies, affecting the development of the pain pathways, either weakening or strengthening them.
This important data will help to ensure they receive appropriate treatment as adults. Today, new research indicates that abnormalities can be reversed.
New Treatments for Pain
Chronic pain affects one in five people. This is a purposeless pain still perceived after the injury has been healed. One woman suffered a stroke and made a full recovery, but five years later, still experienced pain in her left side and head, and a stabbing feeling in her left eye. Prof. Turo Nurmikko of the University of Liverpool believes that changes to the brain can be reversed. Magnetic pulses were fired into her motor cortex, responsible for movement, to rewire malfunctioning nerve cells. She experienced the first pain relief for five years. It’s early days, says Prof. Nurmikko, but he is optimistic.
For burns patients, the healing process is nearly as severe as the injury, but they can be helped. Human beings are intensely visual creatures, says Prof. Hunter Hoffman of Harbourview Burns Center, Seattle.
The distraction of being immersed in a session of “virtual reality” experience called “Snow World” while changing burns dressings produced gratifying results. While throwing snowballs at exploding penguins, the patient’s attention focused on the activity of the game, allowing treatment to proceed at 50% reduction in pain. This works because the brain can only cope with a limited level of stimuli.
Gate-control Theory and Acupuncture
The gate-control theory of pain appeared in the journal Science in 1965, in an article by Ronald Melzack, a US psychologist and English anatomist, Patrick David Wall. The Oxford Dictionary of Psychology defines the process as follows: "Pain signals transmitted by small-diameter nerve fibres may be blocked at the level of the spinal cord and prevented from reaching the brain by the firing of larger sensory nerve fibres, which act as a gate without transmitting pain signals themselves."
Acupuncture, says the Oxford Dictionary of Psychology, works by stimulating large diameter sensory nerves enabling them to block the spinal gates. This is useful in cases of chronic pain where injury or infection may have damaged these large fibres, preventing them from operating as a pain-blocker.
Sources
"The Secret World of Pain" Horizon, BBC2 Television, 31 January 2011.
Oxford Dictionary of Psychology, Andrew M. Colman (with associate editors) Oxford University Press, 2001.
Janet Cameron - MA. Cert.Ed. is a retired university lecturer and author of twelve books, women's short fiction and a magazine column.
