Continuous topical drug delivery using osmotic pump in animal cochlear implant model: Continuous steroid delivery is effective for hearing preservation

Conclusions: Continuous topical drug delivery using an osmotic pump is an effective supplementary technique for hearing preservation after cochlear implantation, as demonstrated in a guinea pig model. Objective: To evaluate the effect of continuous topical steroid delivery via an osmotic pump in an animal cochlear implant model. Methods: Twenty-three guinea pigs were used for the study. The animals were divided into three groups: control group (n = 8), simple topical dexamethasone delivery group (sDEXA group, n = 7) and continuous topical dexamethasone delivery group (cDEXA, n = 8). The hearing thresholds of all animals were measured by pre-operative auditory brain stem responses (ABRs) at 2, 8, 16, 24, and 32 kHz. ABRs were re-evaluated after cochlear implantation, and the animals were sacrificed for hematoxylin and eosin staining. Results: The ABR threshold at 1 week post-operatively was significantly lower in the cDEXA group than in the control and sDEXA groups at most frequencies. Threshold shifts from baseline were statistically smaller in the cDEXA group than in the control and sDEXA groups at all frequencies. Histological analysis revealed decreased numbers of multi-nucleated giant cells and thinner histiocyte layers.