All subjects will have two permanent stimulators placed over the exiting nerve roots at T9 at the implant visit. The stimulators can easily be removed for non-responders. High frequency stimulation is typically programmed below sensory threshold. This type of stimulation lends itself to a placebo-controlled trial. For this study subjects will be randomized 1:1 at enrollment into a high frequency or sham group. Neither the subjects nor experimenters will be made aware of their randomization assignment for at least the first month of the trial. Subjects belonging to both groups will be unblinded to their assignment at the 1-month or a later visit (including unscheduled visit) if they have a VAS > 30 mms. Subjects belonging to the sham group will be reprogrammed with HF stimulation at this point. Subjects belonging to the HF stimulation group will keep stimulating with HF. Subjects reporting a VAS < 30 mms will continue to be blinded.