Distortion-product Otoacoustic Emissions in Experimentally Induced Hydropic Ears

Abstract

The postoperative changes of distortion-product otoacoustic emissions (DPOAEs) and cochlear potentials were examined using 15 albino guinea pigs in which endolymphatic hydrops was induced by obliterating the endolymphatic sac. DPOAEs (geometric mean: 4,6 and 8 kHz) were measured once before and every week after surgery. At the 2nd (n = 5), 4th (n = 5) and 12th (n = 5) postoperative weeks, endocochlear potential (EP) and compound action potential (CAP) were measured. Although the reduction in DPOAEs at 8 kHz was first detected at the 12th week, the amplitude of DPOAEs at 4 and 6 kHz was already reduced at the first week and decreased gradually thereafter. In contrast to these results, the CAP threshold was not elevated at the 2nd week and a slight increase was first detected at the 4th week. The results obtained in the present study suggest that DPOAEs are more sensitive than CAP in detecting the presense of hydrops.

Key Words:

• active process
• Meniere's disease
• compound action potential
• endocochlear potential