Percutaneous electric nerve field stimulation alters cortical thickness in a pilot study of veterans with fibromyalgia

[Display omitted] •Fibromyalgia pain improved following treatment with standard therapy or PENFS.•Right insular increases in cortical thickness correlated with improved pain scores.•Posterior dorsal cingulate cortical thickness decreased with improved pain scores.•Cortical thickness decreased in the left middle posterior cingulate following PENFS.•Cortical thickness decreased in the left cuneus following PENFS. To evaluate changes in cortical thickness and right posterior insula (r-pIns) gamma-aminobutyric acid (GABA) concentrations in veterans with fibromyalgia treated with auricular percutaneous electric nerve field stimulation (PENFS). This was a randomized, controlled, open label investigation conducted in a government hospital. Twenty-oneveterans with fibromyalgia wererandomized to receive either standard therapy (ST; i.e., 4 weekly visits with a pain practitioner) or ST withauricular PENFS (ST + PENFS). Neuroimaging data was collected at baseline (i.e. before the first treatment session) and again within 2 weeks post-treatment.​ Clinical pain and physical function were also assessed atthese timepoints. Single-voxel magnetic resonance spectroscopy was carried out in r-pIns to assess changes in r-pIns GABA concentrations and high-resolution T1-weighted images were collected to assess changes in regional gray matter volume using cortical thickness. Both the ST + PENFS and ST groups reported a decrease in pain with treatment. Volumetric: Cortical thickness significantly decreased in the left middle posterior cingulate (p = 0.018) and increased in the left cuneus (p = 0.014) following ST + PENFS treatment. These findings were significant following FDR correction for multiple comparisons. ST group right hemisphere insula cortical thickness increased post-treatment and was significantly (p = 0.02) inversely correlated with pain scores. ST + PENFS group right hemisphere posterior dorsal cingulate size significantly (p = 0.044) positively correlated with pain scores. GABA: There were no significant correlations with GABA, though a trend was noted towards increased GABA following treatment in both groups (p = 0.083) using a linear mixed effects model. Results suggest a novel effect of PENFS reflected by differential volumetric changes compared to ST. The changes in GABA that occur in both groups are more likely related to ST. Insular GABA and cortical thickness in key regions of interest may be developed as potential biomarkers for evaluating chronic pain path