Dexamethasone eluting cochlear implant: Histological study in animal model

Abstract

Objective: New cochlear implant (CI) designs and developments in implantation techniques have revolutionized the management of hearing loss. However, cochlear implantation still has some disadvantages, such as its potential to initiate an inflammatory response that may lead to further hair cell damage. Recent topics of investigation have been the effect of glucocorticoids on inflammatory tissue response reduction, glucocorticoid dosage levels, and drug-delivery methods. In the present study, dexamethasone delivery via a drug-eluting CI was evaluated histologically through assessing inflammatory cell infiltration.

Methods and materials: Thirty healthy, adult male guinea pigs were included and randomly assigned to one of three surgical groups that underwent cochleostomy of the basal turn. The experimental group (Group 1) of 12 animals were implanted with a dexamethasone-loaded silicone elastomer shaped like a CI electrode. The primary control group (Group 2) of 12 animals were implanted with a simple CI (non-eluting). A second control group (Group 3) of six animals underwent cochleostomy only. Inflammatory responses were compared between groups by evaluating inflammatory cell infiltration in inner-ear specimens at days 3 and 13.

Results: The Mann‐Whitney test revealed reduction in most of the inflammatory indices in Group 1 compared with Group 2. This was significant for fibrocyte, macrophage, and giant cell infiltration at day 3 as well as lymphocyte, macrophage infiltration, and capillary formation at day 13.

Conclusion: This study showed some attenuation in inflammatory response following insertion of a dexamethasone-eluting CI, suggesting that it could be a route for local drug delivery into the cochlea.