Design of a novel multi-modal stimulation device for the treatment of tinnitus

Abstract

Approximately 15-20% of theworld population is aected by tinnitus, a hearing condition associated with phantomsound perception. A large number of suerers experience a severe level of tinnitus and they are not ableto conduct a normal life because they develop insomnia, depression, and distress.Extensive research has been made to study its pathophysiology and to nd a therapy. However, currently thereare no treatments that have demonstrated to be eective in modulating tinnitus or suppressing its related annoyancefrom a long-term perspective. What is known is that the patients exhibit abnormal electrical activityin multiple areas of the auditory and the central nervous systems. This is the reason why the focus of thescientists has shifted to multi-modal stimulation: multiple stimulations of equal or dierent nature (e.g. doubleelectrical stimulation or acoustic-electrical stimulation) are applied at the same time in the attempt to induceneuroplasticity and restore the normal electrical activity in the targeted areas. Multi-modal stimulation hasbrought signicant improvements both in terms of tinnitus intensity and distress, but the studies conductedare too little to derive conclusions. Stimulation sites, parameters, and patterns are some of the many issues thathave to be properly investigated.The challenge of this work is to design a portable multi-modal stimulator that is able to provide bilateral acousticand electrical stimulation simultaneously. The device works at the same time as an audio player and atranscutaneous electrical nerve stimulator, with the purpose of contemporaneously stimulating the auditorycortex and the autonomic nervous system or the dorsal cochlear nucleus through the vagal nerve or the C2nerve, respectively.Bi-modal stimulation is based on the random presentation of pure tones matched to the tinnitus frequency pitchcombined with two possible electrical stimulation waveforms: a novel one characterized by the superposition ofa low-frequency noise on a DC component ("noise + DC" stimulation) and the second one is burst stimulation.Both the electrical stimulations are current-driven and largely customizable due to the wide programmabilityof the stimulation parameters. The analog design is realized in such a way that two identical output currentsare delivered to the tissue, allowing for bilateral stimulation.The low power consumption and the small dimensions and weight of the device will permit the tinnitus patientto use it for several hours per day while performing his daily life without impairments.