PET Patterns, Biomarkers and Outcome in Burst SCS Treated FBSS Patients

Inclusion Criteria: 1. Occurrence of chronic pain in the lumbosacral region, as well as unilateral or bilateral leg pain. 2. Prior lumbar surgery in medical history. 3. Diagnosed with neuropathic pain in the lower extremities and graded as probable neuropathic pain or definite neuropathic pain according International Association for the Study of Pain (IASP) criteria. 4. Patient report largely unchanged pain condition last 6 months. 5. Patient has undergone a 7 day SCS trial with epidural burst stimulation with the following results: 1. At least 75% coverage of the painful area of tonic stimulation before start of burst trial stimulation. 2. At least 50% reduction in pain intensity, measured via BPI, item 5 from baseline of trial to end of trial period. 6. The patient is ≥ 18 years of age and \< 60 years of age. 7. The patient must willingly participate in all parts of the study, as well as having the ability to complete the entire study plan. 8. Patient must certify that he / she understands the study plan, as well as voluntarily sign informed consent to participate in the study. 9. Must be able to sit still for a minimum of 45 minutes and be able to follow restrictions related to the PET survey. Exclusion Criteria: 1. The patient has other current pain conditions than back and leg pain after back surgery. 2. The patient is treated with opioids exceeding 80 milligrams of Morphine per day or is considered at risk for development of problematic opioid use. 3. The patient suffers from an untreated depression or anxiety. 4. The patient can not complete the study plan. 5. The patient is unable to read or write Swedish. 6. The patient is currently participates in another clinical trial. 7. A history of previous PET scan or other substantial radiation dose in the last 5 years. 8. The patients is suffering from claustrophobia. 9. Ongoing pregnancy or planned pregnancy during study time. 10. The patient has contraindications for arterial catheterization. 11. The patient is previously treated with spinal cord stimulation.