Electroacupuncture (EA) modulates primary somatosensory functional connectivity in association with insular neurochemistry to reduce pain severity in individuals with fibromyalgia (FM), according to the results of a study published in Arthritis Rheumatology.
Though studies have demonstrated EA to be effective at reducing pain in patients with FM, the underlying central nervous system (CNS) mechanism of action has not yet been determined.
To evaluate the contribution of the somatosensory afference of acupuncture to the reduction of clinical pain in patients with FM, data from 76 individuals were analyzed. Included individuals were randomly assigned to receive 2 treatments of 25 minutes of 2 Hz electroacupuncture or mock laser acupuncture (ML) for 4 weeks.
ML included no somatosensory afference. Brief Pain Inventory (BPI) severity scores, resting state functional magnetic resonance imaging (rs-fMRI) scans, and proton magnetic resonance spectroscopy (1H-MRS) spectra in the anterior insula (aINS) were collected before and after the treatment period.
Individuals in the EA group experienced a greater reduction in BPI severity compared with the ML group (P <.001). Increased whole-brain connectivity to the S1leg region was observed in the EA group but not the ML group.
The change in BPI severity was significantly associated with the change in S1leg connectivity to the aINS (P =.01) as well as to the posterior insula (pINS; P =.01) for individuals who had undergone EA but not ML. Greater increases in the S1leg-aINS connectivity were associated with a greater increase in aINS GABA+ posttherapy in the EA group (P =.046).
Greater increases in aINS GABA were associated with greater reductions in BPI severity (P =.01). A mediation analysis showed that a greater increase in aINS GABA+ indirectly mediated the impact of greater S1leg-aINS connectivity on reduced BPI severity.
This study showed that somatosensory afferent acupuncture was significantly more effective at reducing FM pain and at increasing neural connectivity than nonsomatosensory acupuncture. The association of greater posttherapy increases in S1leg aINS connectivity with greater increases in aINS GABA+ may indicate that S1leg signaling increases GABAergic inhibition in the aINS, resulting in a decrease in pain, possibly illuminating the role of somatic sensation in acupuncture therapy.
Limitations to this study include the relatively short treatment period, which may have been responsible for the absence of a main effect of posttherapy GABA+ increase.
Future research with longer treatment times as well as studies investigating the clinical translation of these findings is warranted.
Mawla I, Ichesco E, Zöllner HJ, et al. Greater somatosensory afference with acupuncture increases primary somatosensory connectivity and alleviates fibromyalgia pain via insular GABA: a randomized neuroimaging trial. Published online December 13, 2020. Arthritis Rheumatol. doi:10.1002/art.41620