New research shows that it is undamaged nerve fibres that cause ongoing spontaneous pain, not those that are injured.
These unexpected findings, by Dr Laiche Djouhri, Professor Sally Lawson and colleagues from the University of Bristol, UK, are reported in the Journal of Neuroscience [25 January, 2006].
Previous research into ongoing chronic pain has tended to focus on the damaged nerve fibres after injury or disease and overlooked the intact fibres. This new understanding may help pharmaceutical companies formulate novel pain killers.
Professor Lawson said: “The cause of this ongoing pain and why it arises spontaneously was not understood before. Now that we know the type of nerve fibres involved, and especially that it is the undamaged fibres that cause this pain, we can examine them to find out what causes them to continually send impulses to the brain. This should help in the search for new analgesics that are effective for controlling ongoing pain.”
Ongoing pain is a burning or sharp stabbing/shooting pain that can occur spontaneously after nerve injury. Unlike ‘evoked’ pain caused, for example, by hitting your thumb with a hammer, ongoing pain is particularly difficult to live with because it is often impossible to treat with currently available pain killers.
Djouhri and Lawson show that the nerve cells responsible are ‘nociceptors’ or damage detectors. There are thousands of these nerves cells, each of which has a very long, fine nerve fibre emerging from it. These fibres run within nerves and connect the skin or other tissues to the spinal cord.