Galvanic disruption of vestibulospinal postural control by cochlear implant devices.

All subjects with implanted cochlear stimulators demonstrated evidence of abnormal postural stability without their stimulators activated. Instability increased when they were tested with cochlear stimulation units turned on, and additional instability was demonstrated in four of these subjects when tested in noise. These findings suggest that the electrical stimulation delivered by the cochlear prosthesis is not limited to the auditory system. The precise characteristics of electrical stimulation devices designed for stimulations limited to the cochlea and their spurious effects upon motor performance should be investigated. The design of future intralabyrinthine auditory electrical prostheses must include hardware designs and stimulus paradigms that avoid undesirable vestibular system stimulation.