Abstract
Auditory processing disorder (APD) affects about 2–5% of children. However, the nature of this disorder is poorly understood. Children with APD typically have difficulties in complex listening situations. One mechanism thought to aid in listening-in-noise is the medial olivocochlear (MOC) inhibition. The purpose of this review was to critically analyze the published data on MOC inhibition in children with APD to determine whether the MOC efferents are involved in these individuals. The otoacoustic emission (OAE) methods used to assay MOC reflex were examined in the context of the current understanding of OAE generation mechanisms. Relevant literature suggests critical differences in the study population and OAE methods. Variables currently known to influence MOC reflex measurements, for example, middle-ear muscle reflexes or OAE signal-to-noise ratio, were not controlled in most studies. The use of potentially weaker OAE methods and the remarkable heterogeneity across studies does not allow for a definite conclusion whether or not the MOC reflex is altered in children with APD. Further carefully designed studies are needed to confirm the involvement of MOC efferents in APD. Knowledge of efferent functioning in children with APD would be mechanistically and clinically beneficial.
Highlights
As many as 5% of all children with clinically normal audiograms and no obvious auditory pathology experience listening difficulty in background noise (Chermak and Musiek, 1997; Hind et al, 2011)
One mechanism thought to aid in listening-in-noise is the medial olivocochlear (MOC) inhibition.The purpose of this review was to critically analyze the published data on MOC inhibition in children with auditory processing disorder (APD) to determine whether the MOC efferents are involved in these individuals.The otoacoustic emission (OAE) methods used to assay MOC reflex were examined in the context of the current understanding of OAE generation mechanisms
The number of participants in the experimental groups ranged from 8 to 38, and their auditory processing skills were typically characterized by tests recommended by the ASHA (American Speech-Lanuage-Hearing Association, 2005) or their minor variations
Summary
As many as 5% of all children with clinically normal audiograms and no obvious auditory pathology experience listening difficulty in background noise (Chermak and Musiek, 1997; Hind et al, 2011). Other researchers have reported a higher prevalence (20%) of listening problems in children based on data from a large pediatric audiology clinic (Moore and Hunter, 2013). This condition of listening deficits despite a normal audiogram has often received a clinical label called auditory processing disorder (APD). Children with APD typically have difficulties in complex listening situations, such as understanding speech in background noise or understanding rapid or degraded speech.
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