Alterations in Gray Matter Volume and GABA in Veterans Treated with Percutaneous Electric Neural Field Stimulation (PENFS)

Previous studies have demonstrated that fibromyalgia results in gray matter alterations as well as changes in GABA concentrations in various cortical regions when compared to healthy controls [1,2,3]. In veterans with fibromyalgia, we investigate the effect of PENFS on gray matter alterations and GABA concentrations and correlate them with clinical outcomes such as pain scores and function. PENFS applied to the ear stimulates auricular branches of cranial nerves including the vagus. Subjects: 21 veterans aged 20-60 years old with fibromyalgia were randomized to standard therapy control (ST) or standard therapy with auricular PENFS (ST+PENFS). (ST+PENFS: n = 12; ST: n = 9) Total n = 21. Intervention: ST involved standard therapy. ST+PENFS group included ST+PENFS weekly (5 days on) for 4 weeks. Imaging: Neuroimaging data was collected within 2 weeks of initiating treatment and 2 weeks following the final treatment. Self-reported pain and function were assessed and correlated to MRI timepoints. Analysis was performed of GABA concentrations using a right posterior insula voxel placement. Volumetric assessments were performed of the structural MRI data. Clinical assessments were also conducted. Findings: auricular PENFS results in novel changes observed as neural plasticity on fMRI. This study provides valuable insight on the role of potential biomarkers such as GABA and further investigates cortical gray matter alterations and its association with pain. This research was supported in part by Career Development Awards 1IK1RX002113-01A2, 1IK2RX003227-01 (Anna Woodbury), and 1IK2RX002934 (Venkatagiri Krishnamurthy); by Senior Research Career Scientist Award Grant B6364L (Bruce Crosson) and Center Grant 5I50RX002358 from the US Department of Veterans Affairs Rehabilitation Research and Development Service; and by the National Institute of Mental Health of the National Institutes of Health under Award No. R01MH105561 and R01MH118771 (Ying Guo).