Paradoxical and labile medial olivocochlear functioning as a potential marker of auditory processing disorder in a...

The medial olivocochlear system (MOCS) is composed of fibres projecting directly onto outer hair cells and plays a role in improving the signal-to-noise ratio. The MOCS can be evaluated by measuring suppression of the otoacoustic emissions evoked by contralateral acoustic stimulation. Dyslexic children present an increased probability of auditory processing disorder (APD). These children may present paradoxical MOCS dysfunction.

We report the case of a dyslexic child with APD, who was severely disabled in a noisy environment. Audiometric tests were normal, and the central auditory assessment showed labile MOCS functioning that was not only ineffective, but also potentially deleterious, possibly accounting for this child's hearing impairment in a noisy environment.

This case illustrates the importance of audiological assessment and objective investigation of MOCS function in children with a learning disability, especially with hearing difficulties in the presence of noise, in whom auditory training can be beneficial.