Feasibility and Safety of a Single-Session of Transcutaneous Cervical Magnetic Stimulation, taVNS, and iTBS on Heart Rate Variability, Safety, and Pain Modulation.

The autonomic nervous system (ANS) plays a crucial role in maintaining homeostasis, and its dysfunction is linked to numerous clinical conditions, including chronic pain. Neuromodulatory interventions such as transcutaneous auricular vagus nerve stimulation (taVNS), transcutaneous cervical magnetic stimulation (tCMS), and intermittent theta burst stimulation (iTBS) have been investigated for their potential to modulate autonomic responses and pain perception. However, the efficacy and safety of these techniques remain unclear. This study aimed to evaluate the feasibility and safety of a single session of neuromodulatory stimulation in modulating autonomic function and pain processing in healthy individuals. A double-blind, randomized, crossover clinical trial was conducted with 22 healthy participants, each undergoing four intervention sessions (taVNS, tCMS, iTBS, and Sham-taVNS) in randomized order, with a washout period of at least 36 h between sessions. Heart rate variability (HRV) and conditioned pain modulation (CPM) were assessed pre- and post-intervention using a Polar H10 cardiac sensor and a digital pressure algometer. Adverse effects were recorded immediately after each session. No statistically significant differences were observed in HRV or CPM outcomes across active stimulation conditions when compared to Sham. Among the techniques evaluated, tCMS presented the most favorable safety profile, with fewer reported adverse effects relative to iTBS and taVNS. The absence of significant modulation effects suggests that a single session may be insufficient to induce detectable changes in autonomic or pain processing. However, the tolerability and safety of tCMS indicate its potential for future research involving repeated sessions and clinical populations.