Electrical Determinants of Tinnitus Extinction in a Cochlear Implant Patient

Hypothesis Electrical tinnitus suppression by cochlear implants requires stimulation of a subset of neural elements in the cochlea. Background Tinnitus is the phantom perception of sound in the ears and is a known correlate of hearing loss. Cochlear implants restore hearing and are known to lessen or extinguish tinnitus. The amount of electrical charge required and the number and location of electrodes required to extinguish tinnitus with a cochlear implant are factors that remain poorly understood. Methods In a subject with single-sided deafness, with tinnitus in the deaf ear, we enabled single electrodes and groups of electrodes along the cochlea and increased the current until tinnitus was diminished or extinguished. We recorded the subject's perception of these changes using loudness scaling of both the electrical stimuli and the tinnitus. Results Tinnitus could be extinguished with individual electrodes and more effectively extinguished by activating a greater number of electrodes. Tinnitus suppression and loudness growth of the electrical stimuli were imperfectly correlated. Conclusion Tinnitus suppression in this cochlear implant patient was achieved by electrically stimulating multiple distinct portions of the cochlea, and the cochlear neural substrate for tinnitus suppression may be distinct from that for auditory perception.