Contralateral suppression of distortion product otoacoustic emissions in children with cystic fibrosis: effects of tobramycin

Abstract

The role of the medial efferent system in altering and/or regulating outer hair cell function in the mammalian cochlea has been proposed by a number of investigators. This study measured contralateral suppression of distortion product otoacoustic emissions (DPOAEs) in cystic fibrosis (CF) patients, treated for lung infections with low to moderate cumulative doses of tobramycin, to ascertain the contributions of the efferent-based mechanisms in the development of ototoxicity. The results showed significant suppression of DPOAEs in tobramycin-treated children compared to both nondrug-treated CF and normal children of similar ages. Since DPOAE amplitudes were comparable across the drug-treated and control groups of subjects, pronounced DPOAE suppression in the drug-treated group may be attributed to the instability of the cochlear amplifier induced by the tobramycin treatment. These findings also suggest that enhanced contralateral suppression may be the first sign of a developing ototoxicity.