Objective/Methods: The origin and clinical implications of spontaneous otoa
coustic emissions (SOAEs) have not been well revealed. To investigate the r
elationship between the ear with endolymphatic hydrops and SOAE, SOAEs were
measured in 31 patients with unilateral endolymphatic hydrops and 10 volun
teers with normal hearing levels that had less than 25 dB hearing level (HL
) on average for five frequencies (0.25, 0.5, 1, 2, and 4 kHz). Results: SO
AEs were detected in 18 (58%) of the 31 ears with hydrops, In 15 hydropic e
ars in which the hearing levels were less than 25 dB HL on average, SOAEs w
ere observed in 11 (73%). The results of examining the relationship between
changes in hearing level after administering the glycerol test and SOAE fr
equency showed that four (50%) of eight hydropic ears had SOAEs that were d
etectable between the frequency in which hearing level improved more than 5
dB and the frequency with no hearing level change in the audiogram, In 28
contralateral ears, except for three cases of delayed endolymphatic hydrops
, SOAEs were detected in 17 (61%). In 14 contralateral ears in which the he
aring levels were less than 25 dB HL on average for the five frequencies no
ted above, SOAEs were observed in nine ears (64%). In 20 normal ears, SOAEs
were detected in eight (40%). Prevalence of SOAEs in hydropic ears and con
tralateral ears of the patients with unilateral hydrops tended to be greate
r than that in normal ears; however, there was no significant statistical d
ifference between them. Conclusion: The present results suggest that it is
not possible to mention the characteristics of SOAE in the hydropic ear onl
y in terms of the prevalence of SOAEs. SOAEs may occur in a specific portio
n of the basilar membrane corresponding to the frequency in which hearing l
evels improve after the glycerol test, in some cases with endolymphatic hyd
rops.