Spinal Cord Stimulation and Functional MRI

The main objective is to define, using functional magnetic resonance imaging, the effects of spinal cord stimulation (SCS) on cortical and subcortical BOLD effects in patients with neuropathic leg pain. Our hypothesis is that SCS will demonstrate a consistent pattern of BOLD activation that will correlate with symptomatic improvement.

Inclusion criteria

• Age 18-55 years at time of enrollment.
• Have previous implantation of thoracic epidural Medtronic Restore Ultra, Prime Advanced and Restore Advanced SCS in place for the treatment of CPRS-type 1 or chronic refractory neuropathic leg pain following FBSS. The implantation must be 3 or more months prior to enrollment.
• Patient must have reported significant pain improvement (>50%) following implantation of the SCS.
• Have consistently reproducible pain relief (> 50%) within 10 minutes of switching SCS from an OFF state to an ON state (with "optimal" parameters - see below).
• The SCS battery is implanted in the buttocks region.
• Unilateral or bilateral extremity pain.
• Able to provide informed consent.

Exclusion criteria

• Contraindication to MRI such as: SCS lead in the cervical epidural region Cardiac pacemaker Intracranial aneurysm clips, metallic implants or external clips within 10mm of the head Metallic foreign metals within the orbits Pregnancy; (urine pregnancy test will be done to confirm) Claustrophobia

• Pattern of response to spinal cord stimulation Inconsistent response of pain to spinal cord stimulation Long interval (> 10 minutes) before pain relief following switching SCS from an OFF state to an ON state (with "optimal" parameters) - long "washout" period Lack of significant pain improvement (< 50%) following implantation of SCS
• Positive history of significant brain lesions or pathology including:
• Prior ablative neurosurgery
• History of large vessel strokes or brain tumors
• Psychological Screening