There is evidence that the sensor function of the utricle in patients with bilateral labyrinthine dysfunction (bilateral vestibulopathy) may improve balance under the influence of high frequency basal stimulation of the cochlea.

The aim of the study is to measure the possible co-stimulation of the utricle (which is determined by the SVV) by tonotopic (frequency-specific) cochlear stimulation and thus to objectify whether the stimulation of the auditory nerve in CI patients also leads to an unavoidable co-stimulation of the vestibular system.

The cochlea is tonotopically structured, i.e. certain frequencies are mapped on a specific part of the cochlea from basal to apical. It is not yet known whether tonotopically differentiated stimulation of the cochlea has an unavoidable side effect on other body systems, such as the vestibular organ. If the labyrinthine dysfunction occurs as a consequence of a CI implantation, this could in the future lead to the possibility of reducing vestibular complications after CI surgery by switching certain electrodes on or off.

In a first investigation phase, a conventional and already implanted CE-certified cochlear implant will be used. The aim of this project is to test certain tonotopic stimulus patterns that stimulate the cochlea by varying the volume within predefined settings. Thus, there is no misuse of the device and no change in performance attributes. Within the framework of the clinical project planned here, the testing of vestibular co-stimulation during normal cochlear stimulation via the basal, medial and apical electrodes of the CI electrode is planned. Under the influence of defined stimulation patterns, the assessment of the subjective visual vertical (SVV) in project participants will be investigated.

The influence of tonotopic stimulation on the SVV result will have a high priority.

Inclusion Criteria:

• uni- or bilaterally deafened and deaf patients with cochlear implants (one- or two- sided) from Advanced Bionics (AB), model HiRes 90K and newer
• majority
• given informed consent
• legally competent and mentally able to follow the instructions of the personnel

Exclusion Criteria:

• unsuccessful CI implantation (device or electrode defects, incomplete electrode array insertion, missing neuronal stimulus responses)
• pregnant and/or breastfeeding women
• severe pre- or concomitant disease or reduced general ground condition, so that an outpatient presentation in the ENT polyclinic is not possible
• life expectancy of less than six months
• the patient has received a study medication within the last 30 days within the framework of another study
• simultaneous participation in another clinical intervention study
• anticipated lack of compliance
• alcohol or drug abuse
• the patient is placed in an institution by order of the authorities or court
• patients who are in a dependent or employed relationship with the sponsor, investigator, or their deputy