Morphologic changes in round window membrane after topical hydrocortisone and dexamethasone treatment.

Hypothesis: Are all glucocorticoids supposed to have the same effect on the round window membrane?
Background: Interest in glucocorticoids for topical treatment of inner ear diseases is increasing. The safety of such treatment should therefore be an important consideration before clinical use.
Methods: In this study the authors investigated the morphology of the round window membrane after topical instillation of dexamethasone or hydrocortisone into the middle ear. Twenty Sprague-Dawley rats were used. Five rats received 5 doses, and five rats 10 doses, of 1 microg (20 microl) dexamethasone in the right ear, and five others were given 5 doses, and five rats 10 doses, of 2% (20 microl) hydrocortisone solution, also in the right ear. Membrane morphology was studied in both light microscopy and transmission electron microscopy. The thickness of exposed membranes was measured and compared with that of control membranes.
Results: Thickening and microscopically signs of inflammation were observed in hydrocortisone-exposed membranes but not in dexamethasone-exposed membranes, which did not differ morphologically from those in control ears.
Conclusion: Although hydrocortisone has anti-inflammatory properties, it seems to provoke inflammation in the round window membrane after topical instillation. Dexamethasone had no such effects, however.