Cochlear Implantation With A Dexamethasone Eluting Electrode Array: Functional And Anatomical Changes In Non-Human Primates

Objectives: The aim of this study was to determine whether the dexamethasone-eluting electrode (DEXEL) has a protective anti-inflammatory effect in a normal hearing implanted cochlea, as well as its performance and safety.Design: Ten healthy and normal hearing cynomolgus macaques (Mf) were divided into two cohorts: DEXEL group (DG) (CONCERTO CI device containing a DEXEL) and conventional CI group (CG) (unmodified CONCERTO CI device). The electrode was inserted into the scala tympani via the round window with an angle of insertion of 270 degrees. Auditory, impedance, electrically evoked compound action potential (eCAP), and recovery of function measurements were recorded monthly until sacrifice at 6 months post-implantation. A histologic analysis was also performed.Results: At 6 months, measurement of auditory brainstem responses revealed a mean threshold shift, as well as a mean impedance value, lower in the DEXEL group. The minimum eCAP for the remaining active contacts in the DEXEL group was 68% of that in the conventional CI group. Also at 6 months, the eCAP amplitude produced by a stimulating current of 800 cu (eCAP800) was almost 2.5-fold higher in the DEXEL group than in the conventional CI group (1338.86 +/- 637.87 mu V versus 545.00 +/- 137.37 mu V; p = 0.049). Tissue reactions, in particular fibrosis and ossification, were more common in the conventional CI group.Conclusions: The CI electrode array equipped with a dexamethasone-eluting component tested in macaques evidence that delivery of dexamethasone to the inner ear may produce rapid and long-lasting improvement of hearing with fewer neural tissue reactions.