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

Abstract

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://ichgcp.net/clinical-trials-registry/NCT03759834.

Keywords: Clinical trial; Cochlear implant; Electrical stimulation; Implantable device; Promontory stimulation; Tinnitus; Treatment.

Conflict of interest statement

M.L.C. reports holding pending patents 62/346,306, PCT/US2017/035617, and WO2017213978A1 on devices and methods for treating tinnitus with the use of electrical stimulation. No other authors have relevant conflicts of interest to disclose. The views expressed herein are those of the authors and do not reflect the official policy or position of Mayo Clinic, Brooke Army Medical Center, the U.S. Army Medical Department, the U.S. Army Office of the Surgeon General, the Department of the Army, the Department of the Air Force, or the Department of Defense or the U.S. Government.

© 2022. The Author(s).

Figures

Fig. 1

Trans-tympanic electrical stimulation of the cochlea. A Equipment used for promontory stimulation, including the Cochlear Nucleus Promontory Stimulator Z10012® (Cochlear Corporation, Melbourne, Australia). B Otomicroscopic view of the left tympanic membrane. C, D Surgeon placing the trans-tympanic monopolar needle electrode on the promontory. E Stabilized electrode in left ear. F Typical location of the needle electrode on the promontory of the cochlea is shown (white arrowhead) through a facial-recess approach commonly used for cochlear implantation[22]. G, H oscilloscope recording of promontory stimulation output demonstrating charge-balanced square biphasic pulse waveforms