WASHINGTON, Jan. 25 (UPI) -- English researchers have pinpointed the exact cause of chronic pain, possibly opening the door for revolutionary new treatments.
In a study released Tuesday, Sally Lawson and Laiche Djouhri of the University of Bristol revealed that healthy nerve fibers are the culprits of spontaneous pain, one of three symptoms of chronic pain.
"We really followed our noses. No one was examining this problem of spontaneous pain," said Lawson, a professor of physiology.
The study will be published Tuesday in the Journal of Neuroscience.
Lawson and colleagues found healthy nerve fibers send messages of pain to the spinal cord, an unexpected discovery. Of the little research done on chronic pain, researchers had previously focused on damaged nerve fibers as pain conduits.
Spontaneous pain is a burning, stabbing or shooting pain that occurs randomly yet consistently after injury to nerves. It differs from the two other types of pain, allodynia and hyperalgesia, which both result from evoked pain, such as hitting a thumb with a hammer.
Because it's difficult to replicate spontaneous pain in research animals, few people have studied it, leaving the ailment -- until now -- largely unexplained.
Lawson and colleagues concentrated on the healthy nerve fibers of rats and found these robust cells were detecting damage and firing electrical impulses from the site of the injury to the spinal cord. These healthy nerve fibers, called nociceptors, are the tiniest of nerve fibers, about a thousandth of a millimeter across.
The researchers were able to discern the rats' spontaneous pain through their behavior.
Lawson doesn't know why the healthy fibers are to blame, although she speculated that they may be picking up on the distress of their neighbors. For example, when a nerve is damaged or crushed, as it dies it issues an inflammatory response to nearby nerves.
The study also found that the more information these healthy fibers send, the stronger the pain.
Jeffrey Mogil, the EP Taylor professor of pain studies at McGill University in Montreal, Canada, found the research stunning.
"The important thing here is that all of drug development for pain in the past 50 years has been looking at how drugs work, and no one has looked at spontaneous pain. The reason for the problem may have been people were studying the wrong symptom," he said.
Most of the drugs to treat pain have not evolved into effective treatments, a sore spot for many chronic-pain sufferers.
"This will help force a shift on how pain research is done -- a shift for the better," Mogil said.
Nerve injury can come from a range of ailments, such as a compressed nerve, back problems, complications from surgery, diabetes, shingles and cancer, among others. An accident can also cause permanent nerve damage.
At least 70 million Americans deal with chronic pain of some type, according to the American Chronic Pain Association. In a 2005 poll by ABC News, USA Today and the Stanford University Medical Center, 19 percent of Americans reported experiencing chronic pain, mostly in their backs and knees. The outlook in England is similar, with 20 percent of the English also racked with ongoing pain.
"It's really a problem if people can't function and can't go to work. They're in dreadful pain, their families suffer, and their workplace suffers as well," Lawson said.
Lawson's next step is to study why the healthy nerve fibers continuously send impulses to the spinal cord -- and how to stop them.
"It's an exciting change in the way we should be targeting our efforts," she said.
