Electrocochleography in an experimental animal model of acute endolymphatic hydrops.

A reliable animal model of acute type of endolymphatic hydrops was made with injection of artificial endolymph into the cochlear duct. In 12 animals without Reissner's membrane rupture, the endolymphatic potentials (EP) were kept normal after injection of artificial endolymph, but their electrocochleography (ECoG) showed as: a rise of summating potentials (SP) amplitude, a decrease of action potentials (AP) amplitude, an increase of SP/AP ratio, as well as a delay of N1 latency. In 7 animals with membrane rupture, the EP significantly decreased. ECoG showed as: a decrease of hearing function in all test frequencies, a distortion of SP-AP wave and even a loss of AP. Based on the results of our experiment it can be assumed that the dominant -SP may be seen in the acute stage of endolymphatic hydrops without a rupture of Reissner's membrane. Therefore, the dominant -SP may only be of value in the clinical diagnosis during episodic vertigo and fluctuating hearing loss of Meniere's disease.