Undamaged nerve fibres - not those that are injured - may cause long-term chronic pain, research suggests. Ongoing pain affects one-in-five adults across Europe, and costs an estimated £23 billion a year in lost work days. Inflammation caused by damaged nerve fibres triggered nearby undamaged ones to send signals to the brain, the University of Bristol researchers said. In the journal Neuroscience, they say their finding may aid the development of more effective painkillers. 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. It is particularly difficult to live with because it is often impossible to treat with currently available painkillers. Previous research into ongoing pain has tended to focus on the damaged nerve fibres after injury or disease and overlooked the intact fibres.