The aim of the study is to evaluate treatment outcomes of Spinal Cord Stimulation. In the study each patient participates in four test sessions of 4-5 hours. Patients arrive for test days with their stimulation on. In each test session, baseline pain is first evaluated. Then, SCS is regulated (on/off) and patients evaluate their pain intensity immidiately and every 15 minutes during the test sessions. Patients are blinded to the treatment conditions during their participation in the study. At all times, patients can resume their usual treatment.