Postural responses to electrical stimulation of the vestibular end organs in human subjects.

A multichannel vestibular prosthesis that delivers electrical stimulation to the perilymph of individual semicircular canals is a potential new treatment modality for patients with vestibular deficiencies. Most research in this field has evaluated the efficacy of this approach by its ability to reproduce eye movements in response to head rotations. Our group has developed such a device and implanted it in four human subjects with intractable unilateral Meniere's disease. This allows us to evaluate individual semicircular canal contribution to the control of balance and posture in human subjects. In this report, we demonstrate that electrical stimulation trains delivered to the perilymph of individual semicircular canals elicit postural responses specific to the particular canal stimulated, with some current spread to adjacent end organs. Modulation of stimulation current modulates the amplitude of the postural response. However, eye movements elicited by the same electrical stimuli were not consistent with postural responses in magnitude or direction in all subjects. Taken together, these findings support the feasibility of a vestibular prosthesis for the control of balance and illustrate new challenges for the development of this technology.