Vestibular implant tested in patients with peripheral vestibular damage: effects on spatial orientation, navigation, and neuropsychologic function

This project will test the capability of a vestibular implant (VI) to improve cognitive dysfunction in patients with severe vestibular damage. We will measure how higher-level behaviors, including spatial orientation, navigation, and neuropsychologic function, are affected by long-term stimulation provided by the vestibular implant, and in parallel will study these behaviors in non-implanted patients with different degrees of vestibular impairment. Our goal is to determine if the cognitive dysfunction experienced by patients with severe vestibular damage can be improved with prosthetic stimulation, findings which would expand the clinical utility of the vestibular implant while concomitantly improving understanding of the role of vestibular information in cognition. Damage to the vestibular periphery is typically permanent and untreatable (aside from physical therapy), and when it is bilateral, can result in severe degradation of vestibular-dependent behaviors. The VI was developed as a vestibular analogue to the widely employed cochlear implant, senses the head’s angular velocity in three-dimensions, and provides this information to the brain by stimulating semicircular canal afferents using implanted electrodes. While VI research has progressed from animal models to human patients with vestibular damage, it has focused almost exclusively on eye movements and to a lesser extent balance and gait (although recent human studies also queried subjective measures of dizziness and quality of life). Cognitive processes have been ignored in prior VI studies, even though cognitive symptoms (often referred to as “brain fog”) can be prominent and disabling in vestibular-deficient patients. More generally, vestibular contributions to cognition remain controversial and poorly characterized. In this proposal, we will investigate the effects of VI stimulation on spatial orientation (aim 1), navigation (aim 2), and neuropsychologic function (aim 3) by characterizing these behaviors in patients with bilateral vestibular loss (BVL) who have unilateral VIs, with and without chronic vestibular stimulation. To define the effects of vestibular loss on cognitive behavior, we will also study non-implanted BVL and unilateral vestibular loss (UVL) patients and normal subjects. Subjective assessments of cognitive function, dizziness and perceived disability will be also be measured using patient reported outcome measures (PROMs) and we will also assess more general quality-of-life metrics. We predict that the VI will improve spatial orientation, navigation, and visuo-spatial neuropsychologic function in BVL patients and that these measures will correlate with the PROMs that characterize symptom severity and quality-of-life metrics. In sum, the proposed work will be the first to examine the capability of chronic VI stimulation to improve the cognitive deficits caused by severe vestibular damage, and will also examine the association between cognitive deficits and the metrics that quantify subjective disability. This work will advance scientific knowledge while promoting the development of the VI as a therapy that has the potential to improve the clinical status and quality-of-life for vestibular-deficient patients.