Abstract
Objective. To explore the impact of different electrical stimulation profiles in human recipients of the Geneva-Maastricht vestibular implant prototypes. Approach. Four implanted patients were recruited for this study. We investigated the relative efficacy of systematic variations of the electrical stimulus profile (phase duration, pulse rate, baseline level, modulation depth) in evoking vestibulo-ocular (eVOR) and perceptual responses. Main results. Shorter phase durations and, to a lesser extent, slower pulse rates allowed maximizing the electrical dynamic range available for eliciting a wider range of intensities of vestibular percepts. When either the phase duration or the pulse rate was held constant, current modulation depth was the factor that had the most significant impact on peak velocity of the eVOR. Significance. Our results identified important parametric variations that influence the measured responses. Furthermore, we observed that not all vestibular pathways seem equally sensitive to the electrical stimulus when the electrodes are placed in the semicircular canals and monopolar stimulation is used. This opens the door to evaluating new stimulation strategies for a vestibular implant, and suggests the possibility of selectively activating one vestibular pathway or the other in order to optimize rehabilitation outcomes.
Highlights
IntroductionBilateral vestibulopathy is a heterogeneous disorder resulting in many disabling symptoms, including imbalance, oscillopsia (visual illusion of motion of the environment), reduced mobility, and increased risk of falling
Bilateral vestibulopathy is a heterogeneous disorder resulting in many disabling symptoms, including imbalance, oscillopsia, reduced mobility, and increased risk of falling
We observed that not all vestibular pathways seem sensitive to the electrical stimulus when the electrodes are placed in the semicircular canals and monopolar stimulation is used
Summary
Bilateral vestibulopathy is a heterogeneous disorder resulting in many disabling symptoms, including imbalance, oscillopsia (visual illusion of motion of the environment), reduced mobility, and increased risk of falling. It has even been associated with cognitive impairments [1,2,3]. Vestibular implants are implantable devices that attempt to partially restore vestibular function to patients with severe bilateral vestibulopathy of peripheral origin, using electrical currents [7, 8]. A motion sensor (gyroscope) is used to capture head rotations This motion information is used to modulate electrical currents which are directly delivered to vestibular afferents via implanted electrodes, in an attempt to replace semicircular canal function. The concept is being meticulously investigated in animal models [28] and one team has even begun experimental trials in human subjects [29]
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