An Exploratory Study on the Use of Event-Related Potentials as an Objective Measure of Auditory Processing and Therapy Effect in Patients with Tinnitus: A Transcranial Direct Current Stimulation Study

Abstract

Objective: Treatment effect in tinnitus research is commonly evaluated by use of self-report questionnaires. As this is a solely subjective assessment method, the need for an objective measurement is paramount to genuinely evaluate the effects of therapeutic interventions. The current study explores the value of event-related potentials (ERPs) in the evaluation of high-definition transcranial direct current stimulation (HD-tDCS) for tinnitus treatment.Study Design: Prospective exploratory study.Setting: Tertiary referral center.Patients: Twenty-two chronic tinnitus patients.Intervention: HD-tDCS.Main Outcome Measures: ERPs.Results: The results show a significant shortening of the N1, P2, N2, and P3 latencies after HD-tDCS treatment. Moreover, the increased amplitude of the P2 and N2 peaks result in more salient and clear peaks, with the amplitude of N2 being significant larger after HD-tDCS. However, the ERP changes are not significantly correlated with the change in tinnitus functional index (TFI) total score.Conclusions: The current study was the first to explore ERPs as objective measure in a study with IID-tDCS in tinnitus patients. Adding ERPs to the outcome measures in tinnitus research may lead to a better understanding of the therapeutic effect in the future. The results showed a shortening of ERP latencies and an increased N2 amplitude, possibly reflecting more effective sound processing with higher recruitment of synchronized neurons in the auditory cortex. Future studies should elaborate on these results, by collecting control data and adding a sham group, to provide a better insight in the underlying mechanism of the ERP changes after tinnitus treatment.