Influence of tonotopic cochlear stimulation on subjective visual vertical - a pilot study

This pilot study aimed at evaluating the effect of tonotopic (basal) stimulation on the Subjective Visual Vertical (SVV) in patients unilaterally treated with a Cochlear Implant (CI).

Ten adult subjects with severe to profound sensorineural hearing loss, who were implanted with a CI from Advanced Bionics (AB, Stäfa, Switzerland), model HiRes 90KTM or newer, were included in this prospective pilot study between September and December 2020. A specific CI processor (Naída CI Q90) was used to generate five different stimulation modes: simulation of either basal, medial, or apical electrodes, all electrodes on and all electrodes off. The examination of the verticality was carried out by means of SVV goggles both in the upright body position (head position 0 degrees) and with the head tilted sideways (-30°, -15°, +15°, +30°).

In each stimulation mode, there was a significant difference (p < 0.05) in SVV between the straight head orientation and the tilted head position. There were, however, no significant differences between the five CI settings in any given head position (p > 0.05). No significant differences could be found regarding the direction of SVV deviation relative to the operated ear (p > 0.05).

SVV could not be influenced by tonotopic CI stimulation. Different stimulation settings, patterns and intensity other than the auditory strategy may have to be developed to provide an adequate stimulus to the otolith organs.