Feasibility of Auricular Field Stimulation in Fibromyalgia: Evaluation by Functional Magnetic Resonance Imaging, Randomized Trial

Abstract

Objective: To evaluate the feasibility of recruitment, preliminary efficacy, and acceptability of auricular percutaneous electrical nerve field stimulation (PENFS) for the treatment of fibromyalgia in veterans, using neuroimaging as an outcome measure and a biomarker of treatment response.

Design: Randomized, controlled, single-blind.

Setting: Government hospital.

Subjects: Twenty-one veterans with fibromyalgia were randomized to standard therapy (ST) control or ST with auricular PENFS treatment.

Methods: Participants received weekly visits with a pain practitioner over 4 weeks. The PENFS group received reapplication of PENFS at each weekly visit. Resting-state functional connectivity magnetic resonance imaging (rs-fcMRI) data were collected within 2 weeks prior to initiating treatment and 2 weeks following the final treatment. Analysis of rs-fcMRI used a right posterior insula seed. Pain and function were assessed at baseline and at 2, 6, and 12 weeks post-treatment.

Results: At 12 weeks post-treatment, there was a nonsignificant trend toward improved pain scores and significant improvements in pain interference with sleep among the PENFS treatment group as compared with the ST controls. Neuroimaging data displayed increased connectivity to areas of the cerebellum and executive control networks in the PENFS group as compared with the ST control group following treatment.

Conclusions: There was a trend toward improved pain and function among veterans with fibromyalgia in the ST + PENFS group as compared with the ST control group. Pain and functional outcomes correlated with altered rs-fcMRI network connectivity. Neuroimaging results differed between groups, suggesting an alternative underlying mechanism for PENFS analgesia.

Trial registration: ClinicalTrials.gov NCT03008837.

Keywords: Alternative Therapies; Chronic Pain; Fibromyalgia; Magnetic Resonance Imaging (MRI); Percutaneous Electrical Nerve Stimulation (PENS); Rehabilitation Medicine.

Figure 1.

Depiction of the auricle showing nerve distributions and sample NSS placement. Electrode placement is shown using gray dots. The gray donut depicts one electrode array placed on the posterior pinna. Wire harnesses are not depicted. The battery pack is depicted with its usual placement posterior to the auricle.

Figure 2.

Pain scores over time in PENFS treatment and standard therapy control groups. Participants were assessed at baseline, and at 2, 6, and 12 weeks following the 4-week intervention (PENFS treatment + standard therapy vs. standard therapy control). Individual subjects are represented by dots, some of which overlap. The confidence intervals are shown in shading around each mean, which is represented by a solid line. All pain measures were obtained using the Defense and Veterans Pain Rating Scale (DVPRS). There was a trend towards improved pain scores in the PENFS treatment group as compared to the standard therapy control group at 12 weeks post-treatment.

Figure 3.

Changes in Connectivity for PENFS Treatment Group Relative to Standard Therapy Control Group: Right Posterior Insula Seed. Seed-based analysis was performed using a right posterior insula seed, and changes in the standard therapy group (post-pre) were subtracted from changes in the PENFS group (post-pre). These changes were then analyzed using a 3 dimensional T-test. The PENFS group exhibited changes in connectivity (P=0.05) between the right posterior insula seed and areas depicted. Increased connectivity was found to bilateral cerebellar areas (left cerebellum lobule VIIB/Crus II and right cerebellum lobule VIIB/Crus I-II) post-treatment compared to the standard therapy control group. Other areas displaying increased connectivity included the left inferior frontal gyrus, right superior frontal sulcus, middle temporal gyrus, left putamen, left anterior cingulate cortex, and left brainstem. Decreased connectivity was found to the right inferior parietal lobule. These changes in connectivity reflect a comparison of between (intra-) group changes following treatment.

Figure 3.

Changes in Connectivity for PENFS Treatment Group Relative to Standard Therapy Control Group: Right Posterior Insula Seed. Seed-based analysis was performed using a right posterior insula seed, and changes in the standard therapy group (post-pre) were subtracted from changes in the PENFS group (post-pre). These changes were then analyzed using a 3 dimensional T-test. The PENFS group exhibited changes in connectivity (P=0.05) between the right posterior insula seed and areas depicted. Increased connectivity was found to bilateral cerebellar areas (left cerebellum lobule VIIB/Crus II and right cerebellum lobule VIIB/Crus I-II) post-treatment compared to the standard therapy control group. Other areas displaying increased connectivity included the left inferior frontal gyrus, right superior frontal sulcus, middle temporal gyrus, left putamen, left anterior cingulate cortex, and left brainstem. Decreased connectivity was found to the right inferior parietal lobule. These changes in connectivity reflect a comparison of between (intra-) group changes following treatment.