Effects of transcutaneous auricular nerve stimulation on thalamic relay: A randomized brain imaging study in chronic...

Transcutaneous auricular vagus nerve stimulation (taVNS) has emerged as a potential therapeutic option for chronic pain. This study investigates the modulatory effects of taVNS and transcutaneous greater auricular nerve stimulation (tGANS) on thalamocortical circuits. Seventy individuals with chronic low back pain (cLBP) were randomized to receive four weeks of taVNS or tGANS. Structural and resting-state functional MRI data were acquired at baseline and post-treatment. Seed-based functional connectivity analysis was performed using the ventral posterolateral (VPL) and mediodorsal (MD) thalamic nuclei as seeds. Additionally, gray matter (GM) analysis and diffusion tensor imaging (DTI) fiber tracking were conducted to assess structural changes. 51 patients (taVNS: n = 25, tGANS: n = 26) completed the study. Both groups showed significant reductions in pain intensity, bothersomeness, and interference scores, with no significant between-group differences. Both interventions modulated static and dynamic functional connectivity (sFC/dFC) within thalamocortical, limbic, and sensorimotor networks. In the taVNS group, there were significant decreases in both the sFC and fiber integrity between the MD and the left postcentral gyrus, and the gray matter volume of the left postcentral gyrus after taVNS treatment. Additionally, taVNS reduced the dFC between the VPL and the postcentral gyrus, which correlated with decreased pain intensity. Our findings suggest that both taVNS and tGANS mitigate cLBP and modulate thalamocortical connectivity. Elucidating their distinct mechanisms may advance the development of new strategies for chronic pain management.