76 FM patients were randomized to receive 8 weeks (2 treatments/week) of electroacupuncture (EA, with somatosensory afference) or mock laser acupuncture (ML, with no somatosensory afference). Brief Pain Inventory (BPI) Severity, resting state functional MRI (rs-fMRI), and proton magnetic resonance spectroscopy ( H-MRS) in the right anterior insula (aINS) were collected at pre- and post-treatment.
FM patients receiving EA experienced a greater reduction in pain severity compared to ML (mean difference, EA=-1.14, ML=-0.46, Group x Time interaction, p=0.036). Participants receiving EA, as compared to ML, also displayed increased resting functional connectivity between the primary somatosensory cortical representation of the leg (S1 ; i.e. S1 subregion activated by EA) and aINS. Increase in S1 -aINS connectivity was associated with reductions in BPI severity (r=-0.44, p=0.01) and increases in aINS gamma-aminobutyric acid (GABA+) (r=-0.48, p=0.046) following EA. Moreover, increases in aINS GABA+ was associated with reductions in BPI severity (r=-0.59, p=0.01). Finally, post-EA changes in aINS GABA+ mediated the relationship between changes in S1 -aINS and BPI severity, bootstrapped CI=[-0.533, -0.037].
The somatosensory component of acupuncture modulates primary somatosensory functional connectivity in association with insular neurochemistry to reduce pain severity in FM.
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