If you grab the handle of a hot frying pan, the pain alerts you to danger. You yank your hand back and nurse the injury, and the pain soon subsides. This so-called acute pain (that is, sudden pain) is generally "good" pain because it serves a useful purpose; it's part of the body's warning system that helps prevent serious injury and ensures that wounds are soon attended to.
But for people with chronic pain — pain that lasts at least a few months, sometimes years — the pain message is sent and received over and over but often serves no obvious purpose. Although chronic pain can be a profound challenge for those living with this problem, there are reasons to be hopeful.
In its broadest definition, pain is any unpleasant sensation. The way the body "feels" pain is complicated. For example, pain may be acute, as with touching the hot pain, or chronic, meaning that it lasts at least two months. In addition, the quality of pain varies depending on which nerve pathways send the pain message. It may be an intense, shooting pain that comes and goes from moment to moment, or it may be a relentless, grinding ache. In addition, pain can be "referred"; that is, it may originate in one area but be felt elsewhere.
Pain experts divide pain — regardless of its duration — into two main types: pain caused by damage to tissues such as skin, muscle or internal organs and pain caused by nerve damage or abnormal nerve function. Pain caused by tissue damage is called nociceptive pain. Pain caused by nerve damage or abnormal nerve function is called neuropathic pain, or neuropathy. This type of pain is responsible for some of the most challenging cases of chronic pain, in that pain occurs even though there is no ongoing tissue damage. Neuropathic pain may involve any part of the nervous system, from the tiniest nerve in a toe to complex nerve centers such as the spinal cord or brain.
An array of pain sensors, nerve fibers, pathways and chemical messengers work together to produce the conscious experience of pain:
Pain sensors (also called nerve receptors or pain receptors) sense different things. Some sense heat or cold, others sense pressure and others respond best to chemical irritation or movement.
Nerve fibers carry the messages picked up through these pain sensors. Some nerve fibers carry messages quickly, others relatively slowly.
Pathways are the routes that pain signals travel along nerve fibers; for example, a pain message travels from the toe to the brain along a nerve pathway across multiple nerve fibers.
Some chemical messengers (called neurotransmitters) increase the intensity of a pain signal, whereas others decrease it.
For example, if you step on a nail, pain sensors in your foot send a high-speed signal to the spinal cord, which instantly sends a signal back to your leg to jerk your foot away from the nail. This occurs just as — or even before — you "feel" the pain consciously. Meanwhile, pain signals also travel along a separate pathway to the brain, letting you know that you have injured your foot.
This is a very different pain signaling system from the one that would kick in if the pain were associated with an injured organ, as in a case of appendicitis. The brain interprets somatic (external) and visceral (internal) pain signals quite differently because somatic pain receptors send pain signals along different nerve pathways than those used by visceral pain receptors. These visceral receptors, because they are located inside your body, can detect poor circulation or stretch (that is, dilation or expansion) in an organ.
So if you step on a nail, somatic (external) pain receptors relay immediate and precise pain information to your brain. But in the early phases of appendicitis, visceral (internal) pain receptors alert your brain to a more vague problem.
In appendicitis — in cases of visceral pain in general — the end result is nausea and widespread, crampy discomfort rather than sharp pain. In fact, you may find it difficult to describe just where the pain is located in its early stages. As appendicitis worsens, inflammation along the lining of the abdomen sends more specific signals indicating trouble in the right lower part of the abdomen. As the pain becomes more defined, it involves different pain sensors and different pain pathways. This explains how the pain associated with appendicitis evolves from cramps all over the abdomen to sharp, localized pain and points out how variable pain recognition and signaling can be.
The role of your brain. The brain has an elaborate system for modifying pain signals. For example, soldiers in the heat of battle have reported not feeling severe wounds until after the smoke has cleared, and athletes may not notice they've been injured until after a game.
One way the brain reduces pain sensation is by secreting natural painkillers, including chemicals known as endorphins. Endorphins act on the brain in ways similar to narcotics, such as morphine. Another pain-modifying system governs the amount of the chemical messenger serotonin in the brain. Drugs that either mimic these naturally occurring painkillers or affect the amount of them circulating in the brain can be potent pain relievers.
On the flip side, some things may increase pain sensation; some people with chronic headaches, for instance, report that stress can make their headaches worse. And anyone who looks away when getting a shot knows that watching the needle go in seems to make it hurt more.
Coping With Pain
Sometimes it's clear what causes chronic pain. It may be a symptom of cancer or the reminder of an old injury. It may be a symptom of a chronic illness, such as migraine headaches or arthritis. Or it may be a signal that the nerves themselves are injured (neuropathy). But sometimes chronic pain has no clear explanation and will persist unabated for years.
Many people with chronic pain feel anxious and worried about the future. They worry about how their pain might affect their quality of life — their ability to work and play. Many people with chronic pain have seen several health-care providers without finding relief. They may be frustrated, angry or depressed and uncertain where to turn next.
Fortunately, health-care providers know more about chronic pain than it may sometimes seem, and each year they become better at diagnosing and treating it. Old attitudes about pain are shifting, too; for example, health-care providers have long been hesitant to prescribe potentially addictive narcotics, but as understanding of these and newer drugs has advanced, health-care providers are increasingly willing to treat pain with these powerful tools. New drugs, and new ways of using old drugs, are bringing relief. Some types of chronic pain that couldn't be treated a few years ago, such as migraine pain, can now be controlled.
Strategies for living with chronic pain — how you manage physically, how you work with your health-care providers, how you relate to your family and friends, even how you think about the experience — can make your pain easier to endure.
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