[Immediate acoustic effect of the cochlear fistula in a guinen pig]

To Evaluate objectively the effect that cochleostomy has in the cochlea as well as the exposition of the estria vascularis, through acoustic otoemissions immediatly after surgery.

Submandibular approach to the guinea pig's middle ear and cochlea. Triming of the timpanic and vestibular first turns and wide exposition of the estria vascularis in the first and second turns. Study of cochlear function through acoustic otoemissions of distortion products.

Guinea Pig is a perfect experimentation animal for surgical work when monitoring functional state of the cochlea. Its acoustic response is similar to the one found in other mammals thoug its response is lower than that reported in other papers. The lack of intracochlear manipulation ensures the lower decrease hearing loss deterioration regarding the findings in the different methods of studying the acousting distortion.

There is a decrease of amplitud in the audiograms of distortion for specific frequencies (4 and 6 KHz), located tonotopically near the cochleostomies carried out in the first turn (at the level of scala vestigularis and timpanic). Approadring the cochlea without intracochlear manipulation does not modify greathy the results of audiograms of distortion neither the growth slopes of the response. A lateral approach of the estric vascularis minimising the aggression to labrynth did not cause a significant acoustic deterioration.