Electrical stimulation of the cochlea for treatment of chronic disabling tinnitus: an open-label trial towards the development of an implantable device.

Background: Chronic tinnitus affects millions of people globally and constitutes the most commonly compensated disability among military service members in the United States. Existing treatment options largely surround helping patients cope with their disease as opposed to directly suppressing tinnitus perception. The current study investigated the efficacy of electrical stimulation of the cochlea on chronic disabling tinnitus.

Methods: In this single-arm, open-label clinical trial, 22 adult subjects with severe-range asymmetric or unilateral non-pulsatile tinnitus underwent electrical stimulation of the cochlea through use of an extra-cochlear electrode positioned on the cochlear promontory. Each subject underwent 3 stimulation treatments over 3 weeks at 7-day intervals. Tinnitus severity was determined by Tinnitus Handicap Inventory (THI), Tinnitus Functional Index (TFI), and Tinnitus Visual Analog Scale (VAS). Inclusion criteria required subjects have no worse than moderate sensorineural hearing loss determined by pre-enrollment audiometric testing. The primary outcome was nadir post-treatment THI scores, obtained at seven timepoints following electrical stimulation, with clinically significant improvement defined as a decrease of  ≥ 7.

Results: All 22 (100%) subjects experienced clinically significant improvement in the THI during the study period with a mean decrease in scores of - 31 (95% CI - 38 to - 25) from a baseline of 48. Twenty (91%) experienced clinically significant improvement detectable on at least two of the three tinnitus survey instruments and 17 (77%) experienced clinically significant improvement detectable on all three survey instruments (i.e., THI, TFI, and VAS). Eight (36%) subjects reported either complete (THI of 0; n  = 3) or near-complete (THI 1-4; n  = 5) suppression of their tinnitus following a stimulation session. Thirteen (59%) subjects reported a nadir following stimulation at or below the threshold for "no or slight handicap" on the THI (≤ 16). No adverse events were observed.

Conclusions: These findings establish the foundation for the development of an extra-cochlear implantable device that delivers electrical stimulation to the cochlea for the treatment of disabling tinnitus. For patients considering device implantation, trans-tympanic cochlear promontory stimulation can facilitate patient selection. Trial Registration ClinicalTrials.gov Identifier: NCT03759834. URL: https://clinicaltrials.gov/ct2/show/NCT03759834.