Protection of Inner Ear Function after Cochlear Implantation: Compound Action Potential Measurements after Local Application of Glucocorticoids in the Guinea Pig Cochlea

Abstract

Background: Cochlear implant users with residual hearing often benefit greatly from simultaneous electric and acoustic stimulation. However, implantation can cause trauma to the inner ear, resulting in poorer hearing postoperatively. We investigated whether a single local injection of glucocorticoids can reduce hearing loss in long-term implanted guinea pigs. Methods: Three groups of animals underwent bilateral surgery. One ear was implanted with an electrode, and the contralateral ear received a cochleostomy only. A single dose of the glucocorticoids triamcinolone or dexamethasone, or of artificial perilymph was infused into cochleae via cochleostomy. Compound action potentials were measured before and after application and for 3 months postoperatively. Tissue growth was measured as the percentage of the total area of the scala tympani that was obliterated. Results: Ears subjected to cochleostomy only and treated with glucocorticoids demonstrated a mild hearing loss. In the implanted ears, both glucocorticoids preserved hearing at least temporarily. The volume of tissue growth within the scala tympani was not reduced, and there was no relation between the amount of tissue and hearing loss. Conclusions: Both glucocorticoids show a potential benefit for hearing preservation in implanted ears. Glucocorticoid therapy may be useful to protect residual hearing during cochlear implantation.

Pneumococcal meningitis post cochlear implantation: Development of an animal model in the guinea pig

“…This allows the development of a sufficiently dense fibrous tissue seal at the insertion site and contributes to the avoidance of an enhancement of infection rates in the different experimental groups. Consistent with other studies, a fibrous seal was present around the electrode dummy (Braun et al, 2011). The results of histological investigations of the cochlea suggest that bacteria reached the CNS via the inner ear.…”

Evaluation of Sustained-Release Steroid Hydrogels in a Guinea Pig Model for Noise-Induced Hearing Loss

“…Our data indicate that the 6% Dex hydrogel results in faster hearing recovery with significantly smaller threshold shifts at 16 kHz 7 days after noise exposure and protects SGCs as indicated by a higher SGC density in the first turn of the cochlea 28 days after noise trauma. An otoprotective effect of intratympanic Dex application has been well described in previously published studies [Barriat et al, 2012;Han et al, 2015;Honeder et al, 2016], and there is literature supporting otoprotective effects of topically applied TAAC [Braun et al, 2011;Kiefer et al, 2007;Ye et al, 2007]. Another line of research showed that the intratympanic application of POX407 hydrogels results in sustained glucocorticoid release, which is by now also evaluated in clinical studies Lambert et al, 2012;Wang et al, 2009].…”

“…Another glucocorticoid, which has been successfully applied in different studies -most of them addressing surgical trauma to the inner ear -is triamcinolone acetonide (TAAC) [Braun et al, 2011;Ye et al, 2007]. The systemic application of glucocorticoids causes side effects such as hyperglycemia and osteoporosis [Cope and Bova, 2008;Trune and Canlon, 2012].…”

Effects of a dexamethasone-releasing implant on cochleae: A functional, morphological and pharmacokinetic study

“…The longest study to date is a 1-year postoperative study reported by Douchement et al (2014), wherein gerbil cochleae were implanted with dexamethasone-incorporated rods. Some studies in guinea pigs had a duration of approximately 3 months (Braun et al, 2011;Lee et al, 2013;Stathopoulos et al, 2014), but most studies were limited to 4e5 weeks postoperatively (Eshraghi et al, 2007;Huang et al, 2007). Therefore, the present study investigated the effects of a dexamethasone-incorporated silicone rod in guinea pig cochleae for 6 months postoperatively to achieve more experimental data for a novel drug-embedded CI electrode.…”

“…Locally and systematically administered glucocorticoids minimize or prevent the trauma caused by electrode insertion (Connolly et al, 2011;James et al, 2008;Lee et al, 2013). Intra-or postoperatively applied triamcinolone and dexamethasone protect cochlear function after CI (Braun et al, 2011;Eshraghi et al, 2007;Kiefer et al, 2004).…”