![]() ![]() In order for a combined vestibular and cochlear prosthesis to function optimally, it must be possible to stimulate each sensory modality independently. However, one important conceptual and practical feature of the stimulation was not fully evaluated in these studies. The results of the initial safety and functionality studies have been published elsewhere. Following the same strategy, the redesigned device in reduced form was implanted in rhesus monkeys, and then the full device was implanted in 3 human subjects with combined vestibular and severe-to-profound sensorineural hearing loss. As a result of these initial experiments, a second device, with both cochlear and semicircular canal arrays, was constructed. įurthermore, such stimulation, at pulse frequencies and current levels sufficient to produce vestibular stimulation, did not produce sound sensation, pain, or visually observed or subjectively reported stimulation of the facial nerve. This device was studied longitudinally and was shown to produce vestibulo-ocular responses, electrically elicited compound action potentials, postural sway and motion percepts largely consistent with the responses predicted from activation primarily of the afferents of a single implanted semicircular canal. We have recently developed and tested a vestibular implant in rhesus monkeys and ultimately in 4 human subjects. Since both systems utilize common technologies and stimulation strategies, it should be possible to develop a single device that stimulates both the vestibular and cochlear afferents in response to both sound and motion, driving each system with its appropriate sensory input, and restoring function to both sensory systems. These devices use electrical stimulation of vestibular afferents, primarily the semicircular canal afferents, in response to motion stimulation, bypassing the hair cells of the ampullae of the semicircular canals. Similar devices have been developed to restore vestibular function. Such cochlear implants bypass the natural transduction elements in the inner ear which, when lost or injured, are often the cause of hearing loss. For many years, sensorineural hearing loss has been successfully treated with prosthetic devices designed to stimulate cochlear afferents electrically in response to sound stimulation. As a result, both systems are often impacted by the same pathologies producing a combined loss of function. The afferent fibers from these end organs are adjacent to each other in the internal auditory canal. They share common sensory transduction elements called hair cells and are in similar fluid compartments. The end organs of the auditory and vestibular systems within the inner ear are nearest neighbors. ![]() Auditory and vestibular loss often occur together. ![]()
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