Effects of intratympanic administration of glucocorticoids on the guinea pig inner ear.

OBJECTIVE

This study investigates the effects of intratympanic glucocorticoid administration on the inner ear.

METHODS

Fifteen Hartley guinea pigs were used and divided into five groups: dexamethasone-treated (n = 5), contralateral dexamethasone-treated (n = 5), hydrocortisone-treated (n = 5), contralateral hydrocortisone-treated (n = 5), and control (n = 5). In the control group, 1 ml of saline was injected into the right tympanic cavity via a ventral approach. In the dexamethasone-treated group, 1 ml of dexamethasone at a concentration of 3.3 mg/ml was injected into the right tympanic cavity using the same method, while the left ear of the dexamethasone-treated group remained intact. In the hydrocortisone-treated group, 1 ml of hydrocortisone at a concentration of 50 mg/ml was injected into the right tympanic cavity using the same technique, with the left ear of the hydrocortisone-treated group also remaining intact. To assess the effects of glucocorticoids on the inner ear, we measured a cross-sectional area analysis of the scala media at three hours post-corticosteroids treatment using optical coherence tomography (OCT). The degree of a cross-sectional area change was quantitatively measured using a video digitizer.

RESULTS

Ears treated with either dexamethasone or hydrocortisone showed extension of Reissner's membrane and endolymphatic hydrops. Statistical analysis indicated that a cross-sectional area of the scala media increased significantly compared to the contralateral hydrocortisone-treated and control groups.

CONCLUSIONS

This is the first report to investigate the effects of intratympanic administration of glucocorticoids on the guinea pig cochlea. Dilated endolymphatic space was observed in the steroid-treated ears. Although the underlying mechanism of these histological changes remains unclear, great care must be taken when administering steroids to patients with endolymphatic hydrops-related diseases, such as Meniere's disease.