Background: Current theories of tinnitus assume that the phantom sound is generated either through increased spontaneous activity of neurons in the auditory brain, or through pathological temporal firing patterns of the spontaneous neuronal discharge, or a combination of both factors. With this in mind, Tass and colleagues recently tested a number of temporally patterned acoustic stimulation strategies in a proof of concept study. Potential therapeutic sound regimes were derived according to a paradigm assumed to disrupt hypersynchronous neuronal activity, and promote plasticity mechanisms that stabilize a state of asynchronous spontaneous activity. This would correspond to a permanent reduction of tinnitus. The proof of concept study, conducted in Germany, confirmed the safety of the acoustic stimuli for use in tinnitus, and exploratory results indicated modulation of tinnitus-related pathological synchronous activity with potential therapeutic benefit. The most effective stimulation paradigm is now in clinical use as a sound therapy device, the acoustic coordinated reset (CR®) neuromodulation (Adaptive Neuromodulation GmbH (ANM), Köln, Germany).
Methods/design: To measure the efficacy of CR® neuromodulation, we devised a powered, two-center, randomized controlled trial (RCT) compliant with the reporting standards defined in the Consolidated Standards of Reporting Trials (CONSORT) Statement. The RCT design also addresses the recent call for international standards within the tinnitus community for high-quality clinical trials. The design uses a between-subjects comparison with minimized allocation of participants to treatment and placebo groups. A minimization approach was selected to ensure that the two groups are balanced with respect to age, gender, hearing, and baseline tinnitus severity. The protocol ensures double blinding, with crossover of the placebo group to receive the proprietary intervention after 12 weeks. The primary endpoints are the pre- and post-treatment measures that provide the primary measures of efficacy, namely a validated and sensitive questionnaire measure of the functional impact of tinnitus. The trial is also designed to capture secondary changes in tinnitus handicap, quality (pitch, loudness, bandwidth), and changes in tinnitus-related pathological synchronous brain activity using electroencephalography (EEG).
Discussion: This RCT was designed to provide a confident high-level estimate of the efficacy of sound therapy using CR® neuromodulation compared to a well-matched placebo intervention, and uniquely in terms of sound therapy, examine the physiological effects of the intervention against its putative mechanism of action.
Trial registration: ClinicalTrials.gov, NCT01541969.