Effect of transtympanic injection of steroids on cochlear blood flow, auditory sensitivity, and histology in the guinea pig.

HYPOTHESIS

Transtympanic application of steroids is not harmful to the inner ear.

BACKGROUND

Steroids are routinely used to treat inner ear pathologies, such as sudden sensorineural hearing loss and autoimmune inner ear disease. The transtympanic route has received increased attention as it can lead to higher levels in tissue and nearly eliminate systemic effects. There has been concern over the safety of applying these drugs directly to the inner ear.

METHODS

This study investigates the effects of transtympanic Dexamethasone injection on cochlear blood flow using laser Doppler flowmetry, auditory sensitivity using auditory brain stem responses, and histology in the guinea pig.

RESULTS

Results show a significant increase in cochlear blood flow within 30 s to a mean of 29.26% without significant change in auditory sensitivity. The increase in cochlear blood flow was sustained and did not return to baseline for at least 1 hour after drug application. No histologic changes were observed.

CONCLUSIONS

These results suggest that transtympanic steroid application is not likely to be detrimental to the inner ear. Additionally, the increase in blood flow may indicate a possible mechanism accounting for the pharmacologic effects of steroids in the inner ear.