Auditory outcomes following implantation and electrical stimulation of the semicircular canals

• Published in: Hearing research 2012-05, Vol.287 (1-2), p.51-56
• Main Authors: Bierer, Steven M., Ling, Leo, Nie, Kaibao, Fuchs, Albert F., Kaneko, Chris R.S., Oxford, Trey, Nowack, Amy L., Shepherd, Sarah J., Rubinstein, Jay T., Phillips, James O.
• Format: Article
• Language: English
• Subjects: Acoustic Stimulation; Animals; Auditory Threshold; Cochlear Implantation - adverse effects; Cochlear Implantation - instrumentation; Cochlear Implants; Electric Stimulation; Electroencephalography; Evoked Potentials, Auditory, Brain Stem; Eye Movements; Hearing Loss - etiology; Hearing Loss - physiopathology; Macaca mulatta; Male; Prosthesis Design; Reaction Time; Risk Assessment; Semicircular Canals - innervation; Time Factors; Vestibule, Labyrinth - innervation
• ISSN: 0378-5955; 1878-5891
• DOI: 10.1016/j.heares.2012.03.012

We measured auditory brainstem responses (ABRs) in eight Rhesus monkeys after implantation of electrodes in the semicircular canals of one ear, using a multi-channel vestibular prosthesis based on cochlear implant technology. In five animals, click-evoked ABR thresholds in the implanted ear were within 10 dB of thresholds in the non-implanted control ear. Threshold differences in the remaining three animals varied from 18 to 69 dB, indicating mild to severe hearing losses. Click- and tone-evoked ABRs measured in a subset of animals before and after implantation revealed a comparable pattern of threshold changes. Thresholds obtained five months or more after implantation – a period in which the prosthesis regularly delivered electrical stimulation to achieve functional activation of the vestibular system – improved in three animals with no or mild initial hearing loss and increased in a fourth with a moderate hearing loss. These results suggest that, although there is a risk of hearing loss with unilateral vestibular implantation to treat balance disorders, the surgery can be performed in a manner that preserves hearing over an extended period of functional stimulation. ► Semicircular canals of Rhesus monkeys were implanted with stimulating electrodes. ► In most animals, ABR thresholds were close to controls in the implanted ear. ► Thresholds could remain stable over several months of frequent stimulation. ► Results indicate that hearing can be preserved following vestibular implantation.