EFFECT OF TRANSCUTANEOUS ELECTRONEURO-STIMULATION OF THE VAGUS NERVE ON JOINT PAIN SEQUELAE OF CHIKUNGUNYA FEVER IN THE LOWER LIMBS

This study aims to evaluate the efficacy of transcutaneous electrical nerve stimulation (taVNS) in reducing chronic lower limb joint pain in individuals with sequelae of Chikungunya fever. Post-Chikungunya chronic pain is a prevalent and disabling condition associated with persistent inflammation, neuroimmune alterations, and central sensitization mechanisms, which negatively impact functionality and quality of life. Given the lack of specific treatments with established efficacy, vagal neuromodulation emerges as a promising approach. This is a randomized, controlled, parallel, three-arm clinical trial involving adults with chronic joint pain lasting at least three months after Chikungunya infection. Participants will be randomly assigned (1:1:1) to one of three groups: taVNS, peripheral TENS (active control), or sham stimulation (placebo). The study will use a double-blind design for both participants and evaluators. The interventions will take place twice a week for three weeks, totaling six 30-minute sessions. taVNS will be applied to the superior concha of the left ear using standardized parameters, with intensity adjusted to a comfortable sensory threshold. The active control group will receive TENS on the painful joint, while the sham group will receive auricular stimulation without effective vagal activation. The primary outcome will be the change in pain intensity, assessed using the Visual Analogue Scale. Secondary outcomes will include quality of life (SF-36), pressure pain threshold, joint temperature, and functional performance (Timed Up and Go). The analysis will follow the linear mixed-effects using repeated measures models. The results are expected to strengthen the evidence for taVNS as a non-pharmacological intervention for managing chronic post-Chikungunya pain.