Perceptual response characterization in acute vestibular implant stimulation

The vestibular implant is a promising treatment option for patients with bilateral vestibulopathy. However, perceptual responses to acute electrical vestibular stimulation remain poorly understood. These perceptual responses are of specific interest as the vestibular system plays a central role in self-motion perception and spatial navigation. This study is the first to systematically examine perceptual responses to acute electrical vestibular stimulation.

Nine subjects with bilateral vestibulopathy and severe sensorineural hearing loss in the ear to be implanted were included in this study and received an investigational multichannel vestibulocochlear implant. Perceptual responses were assessed for each vestibular electrode across the semicircular canals, over multiple sessions within one year post-implantation. Electrical stimuli were delivered with gradually increasing intensity using a stepwise approach. Following each stimulus, subjects were interviewed about their perceived experiences using an open, semi-structured approach. Responses were categorized by perception type, and thresholds were analyzed relative to stimulation intensity and the targeted ampullary nerve.

Three main types of perceptual responses were identified: motion, auditory, and vibration. Motion perception roughly aligned with the axis of the stimulated canal. Auditory perceptions increased in pitch with increasing stimulation amplitude. Vibration was consistently reported across all subjects and vestibular electrodes. Perceived intensity increased linearly with stimulation amplitude, from low threshold to upper comfortable level.

This study structurally characterized perceptual responses to electrical vestibular stimulation in subjects with a vestibulocochlear implant for the first time. The identification of distinct response types and their relationship to stimulus parameters provides a foundation for improving implant fitting and optimizing stimulation paradigms. Future studies should refine fitting strategies based on these perceptual findings.