Understanding Chronic Pain

 
In the forefront of pain research are scientists supported by the National Institute of Neurological Disorders and Stroke (NINDS), the leading Federal agency supporting research on pain. Other Federal agencies important in pain research include the National Institute of Mental Health (NIMH), the National Institute of Dental Research (NIDR) and the National Center Institute (NCI). Within the last decade both the International Association for the Study of Pain and the American Pain Society have been established and grown into flourishing professional organizations attracting young as well as established research investigators and practicing physicians.

Sounding The Pain Alarm

Part of the inspiration for the new groups has come from a deeper understanding of pain made possible by advances in research techniques. Not long ago neuroscientists debated whether pain was a separate sense at all, supplied with its own nerve cells and brain centers like the senses of hearing or taste or touch. Maybe you hurt, the scientists reasoned, because nerve endings sensitive to touch are pressed very hard. To some extent, that is true: Some nerve fibers in your skin will be stimulated by a painful pinch as well as a gentle touch. But neuroscientists now know that there are many small nerve cells with extremely fine nerve fibers that are excited exclusively by intense, potentially harmful stimulation. Scientists call the nerve cells nociceptors, from the word noxious, meaning physically harmful or destructive.

Some nociceptors sound off to several kinds of painful stimulation -- a hammer blow that hits your thumb instead of a nail; a drop of acid; a flaming match. Other nociceptors are more selective. They are excited by a pinprick but ignore painful heat or chemical stimulation. It's as though nature has sprinkled your skin and your insides with a variety of pain-sensitive cells, not only to report what kind of damage you're experiencing, but to make sure the message gets through on at least one channel.

Broadcasting The News

That same dispersion of force continues once pain messages reach the central nervous system. Suppose you touch a hot stove. Some incoming pain signals are immediately routed to nerve cells that signal muscles to contract, so you pull your hand back. That streamlined pathway is a reflex, one of many protective circuits wired into your nervous system at birth.

Meanwhile the message informing you that you've touched the stove travels along other pathways to higher centers in the brain. One path is a express route that reports the facts: where it hurts; how bad it is; whether the pain is sharp or burning. Other pain pathways plod along more slowly, the nerve fibers branching to make connections with many nerve cells (neurons) en route. Scientists think that these more meandering pathways act as warning systems alerting you of impending damage and in other ways filling out the pain picture. All the pathways combined contribute to the emotional impact of pain -- whether you feel frightened, anxious, angry, annoyed. Experts called those feelings the "suffering" component of pain.

Still other branches of the pain news network are alerting another major division of the nervous system, the autonomic nervous system. That division handles the body's vital functions like breathing, blood flow, pulse rate, digestion, elimination. Pain can sound a general alarm in that system, causing you to sweat or stop digesting your food, increasing your pulse rate and blood pressure, dilating the pupils of your eye, and signaling the release of hormones like epinephrine (adrenaline). Epinephrine aids and abets all those response as well as triggering the release of sugar stored in the liver to provide an extra boost of energy in an emergency.

Censoring The News

Obviously not every source of pain creates a full-blown emergency with adrenaline-surging, sweat-pouring, pulse-racing responses. Moreover, observers are well aware of times and places when excruciating pain is ignored. Think of the quarterback's ability to finish a game oblivious of a torn ligament, or a fakir sitting on a bed of spikes. One of the foremost pioneers in pain research adds his personal tale, too, of the time he landed a salmon after a long and hearty struggle, only then to discover the deep blood-dripping gash on his leg.

Acknowledging such events, neuroscientists have long suspected that there are built-in nervous system mechanisms that can block pain messages.

Now it seems that just as there is more than one way to spread the news of pain, there is more than one way to censor the news. These control systems involve pathways that come down from the brain to prevent pain signals from getting through.

The National Institute of Neurological Disorders and Stroke (NINDS) supports and conducts research on brain and nervous system disorders. NINDS is one of the 17 research institutes of the Federal Government's National Institutes of Health, an agency of the Public Health Service within the U.S. Department of Health and Human Services.

Neurological disorders, which number more than 600, strike an estimated 50 million Americans each year. By supporting and conducting neurological research, the NINDS seeks better understanding, diagnosis, treatment and prevention of these disorders. To achieve this goal, the institute relies on both clinical and basic research. Some key areas of NINDS research include AIDS, amyotrophic lateral sclerosis (ALS), Alzheimer's disease, developmental disorders, epilepsy, neurogenetic disorders, head and spinal cord injury, multiple sclerosis, pain, Parkinson's disease, sleep disorders, and stroke.

If you have a personal concern about neurological disorders, please consult with your healthcare provider. For more information on neurological disorders and stroke call the National Institute of Neurological Disorders and Stroke at 1-800-352-9424.

Reproduced with permission (1993-1997), The National Institute of Neurological Disorders and Stroke
Licensed to Medical Strategies, Inc. (MSI)