Brain sensory network activity underlies reduced nociceptive initiated and nociplastic pain via acupuncture in fibromyalgia.

BACKGROUND: Chronic pain may involve both nociceptive pain driven by peripheral tissue damage and nociplastic pain reflecting central nervous system dysregulation, as in fibromyalgia. Electroacupuncture has been shown to modulate these pathways, but the underlying brain mechanisms remain unclear. This study investigated how electroacupuncture influences nociceptive-initiated and centrally maintained pain via changes in brain activation and functional connectivity. METHODS: In this randomized controlled trial (NCT02064296), female adults with fibromyalgia received either electroacupuncture (n = 19) or sham treatment with inactive laser stimulation (n = 25) over four weeks. Changes in brain activation and connectivity during evoked pressure-pain stimulation were assessed using functional magnetic resonance imaging before and after treatment. Here, we present a secondary analysis of data from the trial. Clinical outcomes assessed include pressure-pain tolerance and widespread pain, and analyses tested whether brain measures mediated treatment-related effects. RESULTS: Here we show that in the electroacupuncture group, reductions in widespread pain are associated with increases in pressure-pain tolerance. This relationship is mediated by greater activation of the primary somatosensory cortex and stronger connectivity between somatosensory and insular regions, consistent with a bottom-up mechanism linking peripheral nociceptive-initiated input to central nociplastic pain modulation. In contrast, the sham group shows reductions in widespread pain linked to decreased precuneus activity and precuneus-insula connectivity, consistent with a top-down process. CONCLUSIONS: Electroacupuncture and sham treatments engage distinct neural pathways to influence pain perception. These findings highlight that electroacupuncture modulates nociceptive-initiated and nociplastic pain through a bottom-up sensory pathway, whereas sham treatment engages top-down control. This mechanistic dissociation may inform patient selection and optimization of acupuncture-based therapies for chronic pain.