There is a paradox at the heart of pain that makes its treatment particularly intractable. “When most parts of the body are damaged, they stop working—they switch off,” Tracey says. “But when nerves are damaged, they do exactly the opposite—they switch on. Sometimes they just won’t switch off, and that is when you get chronic pain.” In the worst cases, as Tracey puts it, it is as if the volume knob on their pain has been turned all the way up. Figuring out how to turn that volume down has proved to be one of the greatest frustrations in medical science.
