“When neural circuits all work, it’s like a symphony,” says Dr. Allen Burton, medical director of neuromodulation at Abbott. “But sometimes, somebody inherits a bad gene, or gets injured, or something nobody knows goes amiss." As a result of this unknown cause, certain neural circuits might start firing over and over again. Our brains think this repeated signal indicates a continuing problem. "All of a sudden, instead of having normal sensation, you have pain, or a terrible ongoing sensation that won’t go away,” Burton says.