[Extratympanic electrocochleography during the glycerol dehydration test in control subjects with normal hearing]

Extratympanic electrocochleography with click stimulation at 80 dBnHL was performed in 15 subjects with normal hearing (28 ears) during the glycerol dehydration test. Testing was performed before oral administration of glycerol (1.2 ml/Kg) as well as after 1, 2, and 3 hours. The mean electrocochleography response from 12 recordings was determined to obtain stable values. Although some ear action potential (AP) amplitudes increased at 1 hour after administration, the AP amplitudes gradually decreased during the test. There were significant differences between before and at 2 and 3 hours after administration. Summating potential (SP) amplitudes increased slightly, but there were no significant differences between before and each time after glycerol administration. Negative SP/AP ratios gradually increased during the test, and there were significant differences between before and each time after glycerol administration. Laterality of the glycerol-induced changes in 13 subjects having both ears tested was positive at 1 and 2 hours after glycerol administration, but the laterality had diminished by 3 hours after administration. It was thus reasonable to compare both ears at 3 hours after glycerol administration.