Effects of intraoperatively applied glucocorticoid hydrogels on residual hearing and foreign body reaction in a guinea pig model of cochlear implantation

Abstract

Conclusion: The intraoperative application of glucocorticoid-loaded hydrogels seems to cause a reduction in neutrophil infiltration. No beneficial effect on hearing thresholds was detected. Objectives: To evaluate the application of dexamethasone- and triamcinolone acetonide-loaded hydrogels for effects on hearing preservation and foreign body reaction in a guinea pig model for cochlear implantation (CI). Methods: A total of 48 guinea pigs (n = 12 per group) were implanted with a single channel electrode and intraoperatively treated with 50 μl of a 20% w/v poloxamer 407 hydrogel loaded with 6% dexamethasone or 30% triamcinolone acetonide, a control hydrogel, or physiological saline. Click- and tone burst-evoked compound action potential thresholds were determined preoperatively and directly postoperatively as well as on days 3, 7, 14, 21, and 28. At the end of the experiment, temporal bones were prepared for histological evaluation by a grinding/polishing technique with the electrode in situ. Three ears per treatment group were serially sectioned and evaluated for histological alterations. Results: The intratympanic application of glucocorticoid-loaded hydrogels did not improve the preservation of residual hearing in this cochlear implant model. The foreign body reaction to the electrode appeared reduced in the glucocorticoid-treated animals. No correlation was found between the histologically described trauma to the inner ear and the resulting hearing threshold shifts.

Keywords:

• Cochlear implant
• glucocorticoid
• hearing preservation

Acknowledgements

The authors want to thank Sandra Peiritsch for the keeping of the animals and Astrid Haase for excellent technical assistance. The financial support by the Federal Ministry of Economy, Family and Youth and the National Foundation for Research, Technology and Development is gratefully acknowledged. This study was supported by the Austrian Science Fund (FWF grant P 24260-B19) and MedEl Austria.

Declaration of interest: Christoph Arnoldner is currently receiving a grant from the Austrian Science Fund (FWF: Project no. P 24260-B19) and funding from MED-EL Corporation, Innsbruck, Austria. Clemens Honeder and Elisabeth Engleder are financed by these grants. The remaining authors have no interests to declare.