Imagine a life without pain. No pounding headache after a hellish day at the office. No cricked back after that awful night on Aunt Millie's lumpy sofa bed. No pangs from injuries, childbirth or food poisoning--no pangs, either, to impel us to yank a finger from a flame, rest a broken leg or refrain from romping through poison oak.
Put that way, life without pain would be bad. And short. Once in a blue moon, a child is born without pain-sensing nerves and sets about exploring the world without the cautionary lesson of pain. As the years go by, the injuries pile up--from self-mutilation, damaged joints, infected wounds--until one of them finally proves fatal.
Pain, in other words, is incredibly useful from a survival point of view--a fact that is of no comfort whatsoever to anyone suffering from pain that just keeps coming and coming, for months, years, even decades.
Chronic pain--from arthritis, from cancers invading the body, from damaged nerves and tissues, or mysterious causes that doctors don't understand--creates untold misery in the world, as well as untold hours lost from work. Headaches. Back pain. Facial pain. Intractable pain, sometimes, responding poorly to today's drugs, leaving many sufferers demoralized and despairing.
"When a pain's of short duration, you can cope with it," says Dennis Turk, professor of anesthesiology at the University of Washington, Seattle. "But what do you do when there's no end--when it's 365 days a year, 24 hours a day? It's no surprise that these people get depressed."
What has been a surprise, though, are recent discoveries that could change the way scientists and doctors view pain.
"Pain is not just a symptom of an injury," says Allan Basbaum, chairman of the department of anatomy at UC San Francisco. "Under some conditions, it's really a disease of the nervous system."
What Basbaum is saying is that pain nerves, when we're injured, seem to subtly change--and those changes, if they stick around, can set people up for longer-term misery. Misery that might be avoided if the initial pain were nipped in the bud.
Such nipping should be easier in the future. For years, pain management has relied largely on two groups of drugs: opioids, derived from morphine; and nonsteroidal anti-inflammatory drugs (NSAIDs), a class of painkillers that includes aspirin and ibuprofen. Both groups, while immensely useful, have side effects, such as addictive potential and constipation for opioids, and stomach irritation for the NSAIDs. And they don't work for all types of pain.
Today, though, scientists have homed in on a dizzying array of molecules our bodies use in the pain response. Many of them--including glutamate, substance P and the painful-even-to-pronounce tetrodotoxin-resistant sodium channel--offer different ways to interfere with the pain pathway.
Pain and Our Ability to Fight It
What is pain, anyway? This seems like a really stupid question. (Jab a pin in yourself, it hurts and you go, "yow!" right?) Yet a band of pain scientists didn't think so back in the '70s, when they went into seclusion to properly define the term.
Pain, they agreed, is more than just the relay of a "something bad is happening" message from some part of our body.
Those messages are a huge part of pain, of course. Damaged tissue--from a cut or a scrape, or arthritis--dumps a slew of chemicals onto the special, pain-sensing nerves that run through our bodies. Many of those chemicals can activate the nerves--as can a rude slap or a hand on a hot stove. The nerves then zap electrical messages to the spinal cord and thence to the brain, where the message gets interpreted. What kind of pain? How much? And where in the body did it come from?
But sensing the pain is not the same as getting upset by it. In an operation that's rarely performed nowadays--a cingulumotomy--nerves are cut in a region of the brain involved in the pain response. The result? A chronic pain patient who will now smile at you, and tell you, "I feel the pain. It just doesn't hurt anymore."
And even people who don't opt for this procedure will vary greatly in how much they feel an incoming pain sensation. Certain cultures accept pain more readily. Certain people just don't let pain get to them as easily. Plus, if people are focused on some tricky task, or if they're excited, they'll feel pain less.
"It's the parable of the soldier who looks down after the fighting has stopped, sees blood on his boots and yells for the medic," says Dr. John Loeser, professor of neurological surgery and anesthesiology at the University of Washington. "Or the athlete that fractured a bone but felt no pain."
Our body's pain-fighting system is responsible. Sometimes, when the brain's got other pressing things to think about (like running away from a man-eating tiger or solving a differential equation), it shushes the pain signals, using several chemicals (including our body's natural painkillers, the endorphins) to relay its "Be quiet!" message back down the spinal cord.