to stimulator trial: Risk of bleeding – Spinal cord stimulator trial and implant have been identified as procedures with high risk of serious intraspinal bleeding, which can cause permanent neurologic damage. Appropriate planning for discontinuation and reinstitution of anti-platelet and anticoagulant medications is necessary prior to placement of a stimulator. Psychological evaluation – Depression, anxiety, somatization, and hypochondriasis are associated with worse outcomes for spinal cord stimulators. Experts recommend psychological evaluation prior to placement. A diagnosis with a psychiatric disorder is not a strict contraindication to stimulator placement. However, treatment of the disorder prior to consideration of a trial placement is indicated. Delayed placement – Stimulators may have poor efficacy if placed many years after onset of chronic pain. One review of 400 cases found a success rate of only 9% for patients with stimulator placed over 15 years after onset of pain compared with nearly 85% for patients who received stimulators within two years of pain onset. Technical difficulty – Variations in anatomy, whether congenital or acquired, may preclude successful placement in certain individuals. Imaging of the spine is necessary to guide selection of candidates for whom spine surgery is more appropriate than stimulator placement. Trial period In order to assess the efficacy of the spinal cord stimulator before implantation, a trial must be performed. This trial begins with placement of temporary leads into the epidural space and connected percutaneously to an external generator. The trial typically lasts 3–7 days followed by a 2-week reprieve before SCD implantation to ensure that there is no infection from the trial. Successful trial is defined by at least 50% reduction in pain and 80% paresthesia overlap of the original area of pain. If a patient has sudden changes in their pain, then further investigation is needed for possible lead migration or stimulator malfunction. History Electrotherapy of pain by neurostimulation began shortly after Melzack and Wall proposed the gate control theory in 1965. This theory proposed that nerves carrying painful peripheral stimuli and nerves carrying touch and vibratory sensation both terminate in the dorsal horn (the gate) of spinal cord. It was hypothesized that input to the latter could be manipulated to “close the gate” to the former. As an application of the gate control theory, Shealy et al. implanted the first spinal cord stimulator device directly on the dorsal column for the treatment of chronic pain and in 1971, Shimogi and colleagues