Transcranial Electrical and Acoustic Stimulation for Tinnitus

Overview

Transcranial electrical stimulation (tES) is an umbrella term for non-invasive brain stimulation using weak currents. It comprises transcranial direct current stimulation (tDCS), which is the most established and used method applying constant direct current, transcranial alternating current stimulation (tACS) with sinusoidal current in a fixed frequency, and finally transcranial random noise stimulation (tRNS), which is a subform of tACS generating a random range of low and high frequency alternating currents. A pilot study conducted by Shekhawat and colleagues in 2015 tested the effects of simultaneous electrical and acoustic stimulation. Using tDCS and bilateral broadband noise simultaneously, they found that more tinnitus patients report an improvement in tinnitus perception in comparison to conditions only using tDCS or sham. Further similar approaches very published in recent years, namely a pilot study conducted by Teissmann et al in 2014; study protocols of Rabau et al. in 2015 and Shekhawat et al. in 2015; and an experimental study by Lee et al. in 2017. Results were indicative of a superior efficacy of combined electrical and acoustic approaches, while large-scale controlled studies have not been performed. The need for extension and replication of these approaches is therefore timely. The aim behind our proposed approach, similar to the bimodal approaches above, is to couple the effects of tRNS and acoustic stimulation (AS) for better temporary tinnitus suppression and possible reversal of maladaptive neuroplasticity related to tinnitus. We aim at targeting the (bilateral) auditory cortex with tRNS as in former studies and combine it with white noise (WN) stimulation. This specific combination is novel in its nature and is building on cortical excitability following tRNS.