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://clinicaltrials.gov/ct2/show/NCT03759834

Cochlear promontory anatomy relevant to development of subendosteal and transpromontory electrodes using 192‐section ultra‐high resolution temporal bone CT imaging

“…A similar rationale can be applied to emerging data regarding transpromontory electrical stimulation of the cochlea for chronic disabling nonpulsatile tinnitus. 5 Reporting normative data from nearly 100 adult temporal bones, this work demonstrates that cochlear promontory thickness exhibits a wide range across subjects, from 0.55 to 1.85 mm. Cochlear promontory thickness was statistically significantly greater among men and with increasing body mass index, paralleling existing literature surrounding bone mineral density in adults.…”

“…Successful implementation of subendosteal electrode placement requires understanding of normal anatomic ranges of cochlear promontory thickness as differing electrode designs and extent of surgical drilling may be required. A similar rationale can be applied to emerging data regarding transpromontory electrical stimulation of the cochlea for chronic disabling nonpulsatile tinnitus 5 …”

“…These implantation strategies may be particularly useful in scenarios where significant cochlear ossification precludes conventional intracochlear electrode placement; as a strategy to access apical regions of the cochlea with a separate electrode; or, as a means to atraumatically stimulate the cochlea without intracochlear electrode placement in patients with substantial residual hearing 2 . Similarly, investigation towards subendosteal electrode placement for the treatment of chronic tinnitus has received attention 5 . In light of the mounting interest in developing subendosteal and transpromontory electrode placement techniques to rehabilitate various neurotologic disorders, the current study was conceived with the primary intention of characterizing cochlear promontory thickness in adults using a 192‐slice CT scanner with ultrahigh‐resolution (UHR) scanning capability.…”

“… 2 Similarly, investigation towards subendosteal electrode placement for the treatment of chronic tinnitus has received attention. 5 In light of the mounting interest in developing subendosteal and transpromontory electrode placement techniques to rehabilitate various neurotologic disorders, the current study was conceived with the primary intention of characterizing cochlear promontory thickness in adults using a 192‐slice CT scanner with ultrahigh‐resolution (UHR) scanning capability.…”

The effect of lidocaine iontophoresis for the treatment of tinnitus: a systematic review

“…This view is also confirmed by recent studies. Thus, it has been shown that intra-and extracochlear electrical stimulation can contribute to the suppression of non-pulsatile tinnitus [35][36][37]. Therefore, the effect of lidocaine does not seem to provide the only possible explanation.…”