Effect of artificial endolymph injection into the cochlear duct on perilymph potassium

Objective: To investigate the relationship between endolymphatic hydrops and perilymphatic potassium. Methods: 20 pigmented guinea pigs were used: 10 for scala vestibuli study and 10 for scala tympani study. Acute endolymphatic hydrops was produced by microinjection of an artificial endolymph into the scala media. Injections were performed in the second turn at rates up to 500 nl/min for a period of 10 min. The injection volume was up to 5 μl. Endocochlear potential (EP) was monitored during injections. Simultaneous with the injections, the potassium concentrations in scala vestibuli (K_SV) or tympani (K_ST) perilymph were measured with ion-sensitive double-barreled microelectrodes sealed into in the scalae in the 3rd turn with cyanoacrylate glue. Results: For endolymphatic injections of ≤3 μl, perilymphatic K_SV and K_ST changes were generally small. With larger volume injections, substantial increases in both K_ST and K_SV were observed, with larger increases observed in K_SV compared to K_ST. Conclusion: An increase of perilymph potassium ion concentration is associated with endolymphatic hydrops and the perilymphatic increase could contribute to the inner ear dysfunction of patients with Ménière's disease. Although mild hydrops may not cause perilymphatic changes, extended hydrops may increase perilymphatic K which could contribute to vertigo and/or hearing loss during the attack.