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Efferent suppression test – sensitivity and specifi city

100%

Lisowska G. , Namysłowski G. , Misiołek M. , Wojciech Ś. , Orecka B. , Czecior E. , Dziendziel A.

Otolaryngologia Polska

2008

tom 62(6)

747-754

Introduction. The amplitude of click evoked otoacoustic emissions can be suppressed (reduced) with contralateral acoustic stimulation (CAS). This is thought to be due to the inhibitory control that the medial efferent auditory nerve exerts on outer hair cell function. One commonly used test of medial olivocochlear (MOC) function in humans involves measuring the degree of suppression of ipsilateral otoacoustic emissions (OAEs) by CAS. This effect is called contralateral suppression, efferent effect or olivocochlear refl ex. Aim of the study. The objective of this study was to measure cut-off level of contralateral suppression, sensitivity and specifi city of the efferent test. Material and methods. To evaluate the function of MOC system click evoked otoacoustic emissions (CEOAEs) with and without continuous contralateral broadband noise (BBN) stimulation were recorded in 14 patients with multiple sclerosis, 16 patients with unilateral cerebello-pontine angle tumor and control group matched for age and gender. BBN was presented at 50 dB SL and otoacoustic emissions were recorded in response to nonlinear clicks at 70 +/- 3 dB SPL. Results. The cut-off level was established at -1.4 dB. For 1.4 dB cut-off level of contralateral suppression the sensitivity of the efferent test was 90% and specifi city was 70%. Conclusions. To conclude, assessment of efferent suppression may be a useful addition to the battery test employed in the investigation of multiple sclerosis and cerebello-pontine angle tumors. The MOC suppression test may provide a tool for an early diagnosis of the brainstem pathology.

Changes in Distortion Product Otoacoustic Emission Caused by Contralateral Broadband Noise

100%

Ozimek E. , Wicher A.

Changes in Distortion Product Otoacoustic Emission Caused by Contralateral Broadband Noise

88%

Ozimek E. , Wicher A.

2014

tom Vol. 39, No. 1

125--138

The main purpose of this investigation was to measure the effect of contralateral acoustic stimulation (CAS) on distortion product otoacoustic emission (DPOAE) in twenty human ears, for a ratio of primary tones f2/f1 = 1.22 and a wide frequency range of f2 (1.4–9 kHz), for two intensity levels of primary tones (L1 = 60 dB SPL; L2 = 50 dB SPL and L1 = 70 dB SPL; L2 = 60 dB SPL) and two intensity levels of CAS (50 and 60 dB SPL). It was found that in the presence of CAS, in the majority of cases the DPOAE level decreased (suppression), but it might also increase (enhancement) or remain unchanged depending on the frequency. The mean suppression level of the component of the frequency fDP = 2f1 − f2 might be approximated by a linearly decreasing function of the f2 frequency of primary tones. The slope of this function was negative and increased with an increase of the contralateral stimulation level. The higher was the contralateral noise level the greater was the suppression. For the fDP level below about 15 dB SPL, suppression was observed in a substantial number of measurement cases (in about 85% of all measured cases on average). When the fDP level was higher than 15 dB SPL, only suppression (not enhancement) was observed.