Wind blowing on skin or touch of a shirt is extremely painful - Discovery will help sufferers rebuffed for lack of physical signs Dec. 15, 2005. ELAINE CAREY HEALTH REPORTER Canadian scientists have discovered a protein that plays a key role in causing debilitating, chronic pain that until now has never been understood. "Some people can't wear shirts or they're not able to go out because the touch of a breeze gives them lightning-like pain," said Dr. Michael Salter, who heads the University of Toronto Centre for the Study of Pain. "The worst part is that there's often no physical sign that something's wrong. They're suffering intensely, they get no relief from medications and their family and friends don't understand." The discovery paves the way for developing new ways of detecting and treating the chronic pain that affects thousands of Canadians, says a study published yesterday in the scientific journal Nature. Chronic or neuropathic pain is caused by nerve damage brought on by an injury or illnesses such as cancer, HIV-AIDS or diabetes, which causes changes in spinal cord cells called microglia. Once damaged, the scientists discovered that microglia release a protein called brain-derived neurotrophic factor which causes spinal neurons to send an abnormal signal to the pain-processing networks in the brain. Microglia normally act to suppress pain signals to the brain and spinal cord but the protein converts it into a mechanism that amplifies them, said Salter, co-principal investigator with Dr. Yves De Koninck of Laval University and a senior scientist at Sick Kids Hospital. "One of the messages from this paper ... is that after these kinds of injuries to nerves in your arm or leg or hand, you can have changes in your spinal cord that can perpetuate pain and actually intensify it long after the injury has healed," he said. "This is an important discovery for the millions of Canadians who suffer from debilitating chronic pain that cannot currently be treated," said Michael Wilson, chair of NeuroScience Canada, one of the funders of the research through the Brain Repair Program. The discovery "represents an important shift that could soon provide patients with effective treatments and allow them to be active again in our society," Wilson said. Chronic pain is "a touchy subject" because there are no obvious physical symptoms and sufferers are often told they are making it up or faking it, Salter said. Even strong painkillers don't suppress the pain because they work on only some of the large pain-processing networks but not all of them, he said. "Typically people with neuropathic pain get very little pain relief from traditional painkillers like morphine or Aspirin or acetaminophen," he said. For some people the pain is so acute that even common events like wind blowing on the skin or the touch of a shirt is extremely painful. When neuropathic pain attacks children with cancer who are undergoing chemotherapy, the pain is so excruciating the treatment has to be stopped. The discovery of how microglia communicate with nerve cells in the pain-processing networks should help in developing drugs to treat it, Salter said. And it could lead to a diagnostic test to identify it. "You could go and have a test and show your physician: `Look, there really is something wrong with me,'" he said. That is a bigger issue in the United States where many chronic pain sufferers can't get any health care benefits. Barry Ulmer, executive director of the Chronic Pain Association of Canada, said the findings were encouraging but were still only at the laboratory stage and "it's got a long way to go. "If pain was spelled flu, it would already be considered an epidemic in this country," said Ulmer, whose wife suffers from chronic pain. "Anything that comes forward that takes away from the subjective nature of pain is helpful," he said. "Most people are stigmatized because of it. Anything positive that comes along has to be a bonus."