الفهرس 
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Abstract
The objectives of the study are:
First: to limit the effect to the affected ear.
Second: to save hearing.
Conclusion and summary:
Period can expect to overcome dosage uncertainties.
This experiment showed that an osmotic infusion pump can be implanted and used to deliver a drug to the middle ear cavity of the guinea pig. It also showed head tilt sign might be helpful in predicting the vestibular damage secondary to local middle ear application of gentamicin. To evaluate the histpopathologic changes, light microscopy is still a valid method. However, it seems that vestibular hair cells damage is more difficult to identify in comparison with cochlear hair cells.
Experience with this experiment indicates that more satisfactory results could be expected if middle ear inflammation was avoided by making infuscate less irritating.
The current study showed that otitis media produced a break down in the bony cochlear capsule and the round window in some cases. Breakdown was not related to the dose of locally applied gentamycin.
Since the main possible route to entry for a drug from the middle to the inner ear is through the round window, it could be possible to preserve the cochlear structures by protecting the round window and diverting the drug to the oval window. However, the limited number of cases done with round window protection in this study showed that it did not work.
Locally applied gentamycin into the middle ear can get access to the systemic circulation. Nevertheless, the level of gentamycin did not exceed therapeutic levels in the experiment.
There was no detectable effect on the contra lateral ear.
Despite of the presence of the breakdown in some cases it shown that the degree of neuroepithelial damage was dose dependant. However, no differential effect could be detected.