Auricular Ultrasonic Vagus Nerve Stimulation: Effectiveness of Blinding and the Occurrence of Adverse Effects in People with Tinnitus

Background/Objectives: Vagus Nerve Stimulation (VNS) has been suggested as a treatment for tinnitus, but its effect on the condition remains unclear. Ultrasonic Vagus Nerve Stimulation (U-VNS) involves non-invasive stimulation of the auricular branch of the vagus nerve, potentially providing an alternative to traditional VNS. To pre-emptively address some of the methodological challenges of future trials investigating U-VNS, a highly blindable sham device is needed. This study aimed to (1) investigate the effectiveness of blinding of a U-VNS device and (2) record any adverse effects, including any negative effects on tinnitus loudness, alongside their onset and duration. Methods: In this single-blind randomized controlled study, 20 volunteers with chronic tinnitus received two 29 min sessions of true U-VNS followed by sham U-VNS, or vice versa. Sessions were a week apart, and in a randomized order. The effectiveness of blinding and adverse effects, including changes in tinnitus loudness, were measured using self-report questionnaires. Results: James’ Blinding Index revealed that blinding was highly effective in both the real U-VNS condition, BI = 0.79, 95% CI (0.61–0.92), and the sham condition, BI = 0.76, 95% CI (0.60–0.89). Adverse effects were uncommon and mild, primarily consisting of sensations on the skin beneath the transducer. For most participants, tinnitus loudness either decreased or stayed the same in both conditions. Conclusions: A high level of blinding was achieved, suggesting that the ZenBud sham device may be suitable as an effective placebo control in future trials. Adverse effects were uncommon and mild. These findings will help inform the design of future clinical trials to evaluate the safety and efficacy of U-VNS.