Background: Sympathetic dysfunction may be present in complex regional pain syndrome, and sympathetic blocks are routinely performed in practice. To investigate the therapeutic and predictive values of sympathetic blocks, the authors test the hypotheses that sympathetic blocks provide analgesic effects that may be associated with the temperature differences between the two extremities before and after the blocks and that the effects of sympathetic blocks may predict the success (defined as achieving more than 50% pain reduction) of spinal cord stimulation trials.
Brief Summary: This is a multi-center, prospective, open-label, single-arm, observational, feasibility study. The goal of this study is to determine the feasibility of intra-spinal stimulation with optimal paresthesia coverage therapy for chronic pain relief in patients with complex regional pain syndrome type I or causalgia. Up to 20 patients with intractable chronic severe limb pain associated with complex regional pain syndrome (CRPS) will be included in the study. A standard of care trial phase to test a subjects' response to Intraspinal-Optimal Stim therapy will be conducted during a 3 to 10-day period. Patients that obtain 50% or greater pain relief during the trial period will undergo permanent implantation of the device. Primary outcome will evaluate pain response at 3 months of therapy, based on NPRS pain score relative to baseline. Patients will be followed up for 6 months after the start of therapy.