Contralateral Acoustic Effect of Transient Evoked Otoacoustic Emissions in Neonates.

Contralateral acoustic stimulation (CAS) has the effect of reducing the amplitude of transient evoked otoacoustic emissions (TEOAE) of the opposite cochlea. This phenomenon is considered to be mediated via the efferent pathway, from the superior olivary complex through the medial olivocochlear system to the contralateral cochlea. The assessment of this suppressive effect provides an objective and noninvasive technique for exploring the function of the efferent auditory system in humans. Two previous studies investigated the suppression effect of TEOAE in newborns and revealed a significant effect in 18 full-term neonates. In this study, the effect of contralateral acoustic stimulation on TEOAE was investigated in 13 full-term neonates (gestational age, 40-42 weeks). The TEOAE were recorded alternately with and without simultaneous, contralateral white noise. The CAS effect of TEOAE was present in all subjects; a mean of 2.21 dB +/- 1.7 (21% +/- 9.3%) was found. Our study demonstrated additional support for the functional maturity of the medial olivocochlear efferent system from birth.