Changes in input/output function of distortion product otoacoustic emissions during the glycerol test in Ménière's disease.

OBJECTIVE

To investigate the manner of change in the input/output (I/O) function of distortion product otoacoustic emissions (DPOAEs) during the glycerol test in patients with Ménière's disease.

MATERIAL AND

METHODS

The DPOAE I/O functions at three F2 frequencies of 1001, 1501, and 2002 Hz were measured before and after the glycerol test following pure-tone audiometry for 16 ears of 16 patients with unilateral Ménière's disease. Changes in DPOAE I/O function during the glycerol test were analyzed using maximum level of DPOAEs (max. DP level) and the detection threshold of DPOAEs (DP threshold) in the I/O function as parameters.

RESULTS

Significant changes in I/O function during the glycerol test were observed for at least one of three F2 frequencies in all 8 ears and 6 of 8 ears with and without positive test results, respectively, regardless of change in pure-tone thresholds at 1000 and 2000 Hz. A total of 12 ears exhibited two findings of significant change in parameters indicating improvement of cochlear function, increase in max. DP level and lowering of DP threshold, and 2 ears exhibited decrease in max. DP level, a finding indicative of deterioration of cochlear function. Neither of the two parameters exhibited significant change simultaneously, except in one I/O function. Moreover, there appeared to be no clear relationship between the parameter exhibiting significant change and F2 frequencies or changes in pure-tone threshold.

CONCLUSION

Subtle changes in cochlear function during the glycerol test can be detected with higher sensitivity by measurement of the DPOAE I/O function than by conventional audiometry. However, multiple parameters should be used in analysis of change in the I/O function since it is difficult to predict how the I/O function will change prior to the glycerol test. Furthermore, the high sensitivity of DPOAEs in detecting change in cochlear function may provide useful information on inner ear status in Ménière's disease.