1990 Volume 33 Issue 2 Pages 118-130
Evoked otoacoustic emission (e-OAE) was investigated in 24 cases of surgically proven unilateral acoustic nenroma and 24 normal hearing subjects. The e-OAE was elicited by the stimulation of tone bursts with the duration of 3ms at 1kHz and 2kHz. The responses were averaged 512 times with the analysis time of 20ms.
The results obtained were as follows;
1) The e-OAE pseudothreshold was within the normal range in a few tumor-bearing ears, but elevated beyond that of normal hearing ears in the other tumor-bearing ears.
2) The interaural difference of e-OAE pseudothreshold was within 5dB in about 70% of the recordings of normal hearing subjects but it was within 5dB in only 30% of the recordings of acoustic neuromas.
3) The e-OAE pseudothreshold in tumor-bearing ears was significantly higher than that in normal hearing ears (p<0.05).
4) The correlation coefficient between the e-OAE pseudothreshold at 1kHz and that at 2kHz was estimated. There was a high positive correlation between them in normal hearing ears and unimpaired ears of acoustic neuroma cases, but the correlation coefficient deteriorated in tumor-bearing ears.
5) In tumor-bearing ears, there was a slight positive correlation between the e-OAE pseudothreshold at 1kHz and the pure tone hearing level at 1kHz. However, no clear correlation was found between the e-OAE pseudothreshold at 2kHz and the pure tone hearing level at 2kHz.
6) There was no clear correlation between the e-OAE pseudothreshold and the maximum speech discrimination score in tumor-bearing ears.
7) There was no clear correlation between the tumor size and the pure tone hearing level in tumor-bearing ears.
8) There was a slight positive correlation between the tumor size and the e-OAE pseudothreshold at 2kHz in tumor-bearing ears. while no clear correlation was found between the tumor size and the e-OAE pseudothreshold at 1kHz.
9) Based upon these results, it was suggested that the pathophysiology of hearing impairment could be so intricated in acoustic neuromas.
10) The e-OAE recording could be one of the supplemental diagnostic tools to detect acoustic neuromas, especially in cases with profound hearing loss in which the ABR conld not be applicable, because the e-OAE could be obtained in some of these cases in spite of the profound hearing loss.
