Metabolic Imaging of Pain Matrix Using 18 F Fluoro-deoxyglucose Positron Emission Tomography/Computed Tomography for Patients Undergoing L2 Dorsal Root Ganglion Stimulation for Low Back Pain.

Introduction Nociceptive signals from lumbar intervertebral discs ascend in the sympathetic chain via the L2 dorsal root ganglion (L2 DRG), a potential target for discogenic low back pain in neuromodulation. Positron Emission Tomography/Computed Tomography (PET-CT) measures functional changes in the brain metabolic activity, identified by the changes in the regional cerebral blood flow (rCBF) as determined by the changes of F-18 Fluoro-deoxyglucose (F-18 FDG) tracer within brain tissues. Methods and Materials Nine patients were recruited to explore the changes in PET-CT imaging at baseline and four-weeks post implantation of bilateral L2 DRG neurostimulation leads and implantable pulse generator (IPG). PET-CT scans were performed 30 min following an IV injection of 250 +/- 10% MBq of F-18 FDG tracer. Fifteen frames were acquired in 15 min. PET list-mode raw data were reconstructed and normalized appropriately to a brain anatomical atlas. Results Nine patients were recruited to the study, where PET-CT imaging data for five patients were analyzed. The right and left insular cortex, primary and secondary somato-sensory cortices, prefrontal cortex, anterior cingulate cortex, thalamus, amygdala, hippocampus and the midline periaqueductal areas, were assessed for any changes in the metabolic activity. A total of 85 pain matrix regions were delineated SUV (standardized uptake value)(MAX), SUV (MEAN) +/- SD, and SUVPEAK were calculated for each of these regions of the brain and were compared pre- and post-L2 DRG stimulation. Sixty-one of the 85 matrices showed an increase in metabolic activity whereas 24 matrices showed a reduction in metabolic activity. Conclusion This is the first ever study reporting the changes in cerebral metabolic activity and multi-frame static brain F-18 FDG PET imaging after L2 DRG stimulation for discogenic low back pain. Predominantly an increased metabolic activity in nociceptive brain matrices are seen with an increased in (FF)-F-18 FDG uptake following L2 DRG stimulation.