Impaired binaural hearing in children produced by a threshold level of middle ear disease.

Otitis media with effusion (OME), a form of middle ear disease, is the most common reason for young children both to visit their family doctor and to have surgery. Almost all children have at least a single episode of OME before their first birthday and annual incidence rates exceed 50% in each of the first five years. For most children, OME occurs infrequently, but about 10-15% of children have OME during more than half of their first six years. Middle ear effusions attenuate and delay sound, causing conductive sound distortion during the crucial years for language acquisition. The many studies of OME effects on language and other indices of development have produced mixed results. However, a consensus is emerging of mild language impairment in the preschool years, with subsequent performance, emotional, and behavioral difficulties. In addition to the peripheral hearing loss produced directly by the disease, binaural and other central auditory deficits can outlive the OME. It has been unclear which children are at risk of central impairment following OME, since the children studied have generally been recruited from otolaryngology clinics. Consequently, a detailed prospective history of the middle ear status of participants has not been available. By studying six-year-old children with a lifetime known history of OME, we show in this study that only those children with a cumulative OME experience of more than about half the time during the first five years consistently have residual impaired binaural hearing.

Effects of otitis media with effusion (OME) on central auditory function.

Conductive hearing loss attenuates and delays sound passing through the middle ear. This impairs binaural hearing and other central auditory functions dependent on high fidelity sound transmission. Persistent conductive loss leads to central impairments that persist after the peripheral loss has resolved. For example, children who have had multiple episodes of otitis media with effusion (OME) in the first few years of life may have poor detection of sounds in noisy environments, evidenced by reduced binaural unmasking (BU). Recent research shows that a 'threshold' level of OME is required to produce impaired BU. Children who had OME in one or both ears for more than about 50% of the first 5 years had reduced BU. Animal research, using long-term ear plugging, suggests that total OME duration, rather than age at the time of having the disease, determines its effect on BU. Animals reared with bilateral (but not unilateral) ear plugs also have poor auditory temporal resolution, and reduced sensitivity to short tones in the presence of background noise, after plug removal. However, given time (6-24 months) and training, all animals regained normal temporal resolution.