Vestibular implantation and longitudinal electrical stimulation of the semicircular canal afferents in human subjects

Abstract

Animal experiments and limited data in humans suggest that electrical stimulation of the vestibular end organs could be used to treat loss of vestibular function. In this paper we demonstrate that canal-specific two-dimensionally (2D) measured eye velocities are elicited from intermittent brief 2 s biphasic pulse electrical stimulation in four human subjects implanted with a vestibular prosthesis. The 2D measured direction of the slow phase eye movements changed with the canal stimulated. Increasing pulse current over a 0-400 μA range typically produced a monotonic increase in slow phase eye velocity. The responses decremented or in some cases fluctuated over time in most implanted canals but could be partially restored by changing the return path of the stimulation current. Implantation of the device in Meniere's patients produced hearing and vestibular loss in the implanted ear. Electrical stimulation was well tolerated, producing no sensation of pain, nausea, or auditory percept with stimulation that elicited robust eye movements. There were changes in slow phase eye velocity with current and over time, and changes in electrically evoked compound action potentials produced by stimulation and recorded with the implanted device. Perceived rotation in subjects was consistent with the slow phase eye movements in direction and scaled with stimulation current in magnitude. These results suggest that electrical stimulation of the vestibular end organ in human subjects provided controlled vestibular inputs over time, but in Meniere's patients this apparently came at the cost of hearing and vestibular function in the implanted ear.

Characterization of pulse amplitude and pulse rate modulation for a human vestibular implant during acute electrical stimulation

“…In other studies, increasing pulse amplitude by 100% or more led to markedly larger peak eye velocities (Davidovics et al 2012, Nie et al 2013, Phillips et al 2015. Our patients, however, had limited dynamic ranges and thus only modest increases between medium and high PAM levels.…”

“…Identifying the more effective modulation paradigm has become increasingly relevant, as the concept of using modified cochlear implants has shown promise (Guyot et al 2011a(Guyot et al , 2011b and is being adopted also by other groups (Valentin et al 2013, Golub et al 2014, Phillips et al 2015. Cochlear implants use PAM per default for speech encoding.…”

“…They then recorded eye movement responses to different pulse amplitudes and pulse rates at regular intervals over the course of a year or longer. They reported changes of eye velocity over time and noted a lower effectiveness of PRM to modulate eye movement than PAM (Phillips et al 2015).…”

Galvanic Vestibular Stimulation: Cellular Substrates and Response Patterns of Neurons in the Vestibulo-Ocular Network

“…Moreover, knowledge of the activated cellular substrates allows a more faithful categorization of vestibular disorders (Curthoys, 2010) or further improvement of vestibular prostheses (Fridman and Della Santina, 2013). In animals (Gong and Merfeld, 2000;Dai et al, 2011;Mitchell et al, 2013) and human patients (Phillips et al, 2015), vestibular prostheses provide controlled inputs that trigger vestibular reflexes Lewis, 2015). Whereas prosthetic rate stimulation activates ampullary nerve fibers directly, modulated DC currents might also recruit hair cells, if intact.…”

Vestibular Response to Electrical Stimulation of the Otolith Organs. Implications in the Development of A Vestibular Implant for the Improvement of the Sensation of Gravitoinertial Accelerations

“…Animal experiments and data in humans suggest that electrical stimulation of the vestibular end organs could be used to treat loss of vestibular function [28] .…”