Introduction As a part of the efferent auditory pathway, the medial olivocochlear reflex is activated
by contralateral noise and causes a hyperpolarisation of the outer hair cells. This
higher auditory process is described as contralateral suppression and contributes
to better speech perception in noise. To date, this effect was often visualized using
otoacoustic emissions but scarcely via decreased amplitudes of ABR wave profiles.
Probands and Methods 22 probands with normal hearing threshold were included (m:f 12:10; median-age 29.5).
To evaluate potential amplitude effects, the waves I, II, III and V from 20 probands
were investigated. Clicks with intensities of 70 dB, 60 dB and 50 dB were applied.
Measurements with and without contralateral suppression signal were performed. Additionally,
hearing thresholds of 10 probands were compared.
Results A decrease of amplitude on wave V as a result of suppression signal could be measured
on the left side for sound intensity of 70 dB click (p=0.003). There were no significant
differences of wave I, II and III. Sound intensity of 60 dB showed no significant
differences. A suppression effect could be described on wave I for 50 dB (P=0.021).
On the right side no relevant differences of any amplitudes could be determined.
No effect on hearing thresholds could be observed (p=0.250).
Discussion The effect of contralateral suppression could be detected by brainstem auditory evoked
potentials. However, a side difference was observed. Usually the measurement of auditory
brainstem response was begun on the left side, so the measurement time could be a
possible reason for missing evidence on the right side.
Poster-PDF
A-1183.pdf
