Feasibility and Safety of High-Definition Infraslow Pink Noise Stimulation for Treating Chronic Tinnitus-A Randomized Placebo-Controlled Trial

Introduction: Tinnitus has been linked to activity and connectivity changes in the auditory cortex (AC), parahippocampus (PHC), and posterior cingulate cortex (PCC). Although previous studies have targeted these areas individually, no study has yet modulated them simultaneously. Furthermore, novel stimulation designs may be superior to traditional alternating or direct current stimulation. This pilot study investigated the feasibility and safety of a novel brain stimulation technique (high-definition transcranial infraslow pink noise stimulation [HD-tIPNS]) for treating chronic tinnitus targeting the AC, PHC, and PCC.

Materials and methods: A pilot, double-blind, randomized two-arm placebo-controlled parallel trial was conducted, with clinical outcomes collected at baseline, three days, and ten days after treatment. Participants with chronic tinnitus (n = 20) received 12 sessions (three per week for four weeks) of either HD-tIPNS or acti-sham stimulation. Primary outcomes included feasibility, safety, and resting-state electroencephalography (rsEEG) measures, and secondary outcomes included tinnitus and quality of life questionnaires. Feasibility, safety, and secondary measures were assessed using descriptive statistics. rsEEG was analyzed using standard low-resolution electromagnetic brain tomography.

Results: No long-term adverse events were reported. Mild side effects included headache and dizziness, indicating the safety of this stimulation. Participants were rapidly recruited and adhered to the study protocol with minimal difficulty. Drop-out rate was 13%, and the treatment approach was acceptable to participants, supporting the feasibility of the protocol. Tinnitus measures were similar between HD-tIPNS and acti-sham stimulation. rsEEG analyses revealed decreased beta-1 activity in PCC ten days after treatment for acti-sham. The HD-tIPNS group showed decreased beta-1 activity in inferior parietal lobule three days after treatment. Increased functional connectivity in the beta-1 frequency between left and right PHC was found in the HD-tIPNS group compared with the acti-sham group, three days after treatment.

Conclusions: In conclusion, the novel approach is safe and feasible and revealed EEG changes unsupported by clinical benefit. Further research is essential to evaluate the potential of this multifocal network stimulation approach.

Clinical trial registration: This study was registered with the Australia New Zealand Clinical Trial Registry (Registry number: ACTRN12621000151831; Universal Trial Number: U1111-1261-6945).