[Electrical tinnitus suppression--a comparative study of clinical trials and animal experiments]

Electrical tinnitus suppressor was newly developed and clinical study of electrical tinnitus suppression was discussed. Tinnitus was treated with this prototype suppressor in 38 ears out of 34 outpatients. Tinnitus was suppressed during electrical stimulation in all patients. After cessation of electrical stimulation, in 5 ears out of them tinnitus has disappeared at least for more than six months. In 12 ears it made tinnitus more than 10 dBHL softer for the following period, about six months. Hearing was unchanged in all patients. To know the mechanism how electrical stimulation of the cochlea suppressed tinnitus, animal experiments using a single fiber recording technique were made. A positive direct current on the cochlea suppressed the spontaneous activity of the cochlear nerve fiber, while a negative direct current increased the spontaneous activity. An alternative current on the cochlea increased the spontaneous activity of the cochlear nerve fiber. These electrical effects on the spontaneous activity were temporary. Therefore, after cessation of electrical stimulation on the cochlea, changed spontaneous activity restored to the level of prestimulation. Comparing temporary electrical effects on the spontaneous activity of cochlear nerve fiber with a longer suppression on tinnitus, tinnitus suppression following electrical stimulation of the cochlea was not thought to occur at the level of cochlea, but at auditory central nervous system.