1992 Volume 35 Issue 3 Pages 283-289
Evoked otoacoustic emission (e-OAE) and promontory stimulation test (PST) were investigated in 15 cases of surgically proven unilateral acoustic neuroma (AN) which showed the profound deafness with more than 80dB in pure tone audiometry.
The e-OAE was elicited by tone-bursts with frequencies at 1kHz and 2kHz and more than 10dB of interaural difference of pseudothreshold was defined as the significant impairment of cochlear function. The PST was conducted with the stimulation of bursts mode at 6 stimulus frequencies by the Nucleus promontory stimulator. When the auditory sensation was obtained at either 6 stimulus frequencies, it was defined as the PST positive. Also, when the auditory sensation was obtained at all 6 stimulus frequencies, it was defined as the PST score 6, and when the auditory sensation could not be acquired at any 6 stimulus frequencies, it was defined as the PST score 0.
The results obtained were as follows;
1) The mean interaural difference of e-OAE pseudothreshold was 16.0dB at 1kHz and 8.0dB at 2kHz.
2) The positive PST was found in only 40.0% of the subjects and the mean PST score was 0.93.
3) When the pathophysiology of hearing impairment was speculated from the results of e-OAE and PST, it was found that pure cochlear impairment was in 33.3%, pure retrocochlear impairment in 13.3% and cochlear-retrocochlear impairment in 46.7%.
4) It was concluded that the analysis of both e-OAE and PST could clarify the pathophysiology of hearing impairments in AN with profound deafness.
