Recently a new form of spinal cord stimulation therapy called burst spinal cord stimulation (Burst-SCS) is available to treat chronic pain. The goal of this study is to learn more about how Burst-SCS works to reduce chronic pain. The study will examine chronic pain patients who have been deemed candidates for Burst-SCS therapy, and who have already been selected to receive a temporary externalized trial of Burst-SCS from their own doctors as part of their standard clinical care for chronic pain management. During the study, participants will be asked to complete a variety of evaluations at certain time points. In addition, there will be a randomized, double blind, crossover phase, where the particular effects of Burst-SCS and sham SCS will be evaluated. The device used to deliver Burst-SCS and sham SCS is the St. Jude Medical Invisible Trial System.