Otitis media with effusion in children. Binaural hearing before and after corrective surgery.

The masking-level difference (MLD) was investigated in a group of children having no known history of ear disease, and a group of children having a history of otitis media with effusion and hearing loss. The MLD is a psychoacoustic measure of the sensitivity of the auditory system to subtle interaural difference cues of time and amplitude and relates to the ability of the listener to detect and to recognize signals in noisy backgrounds. In the otitis media with effusion group, MLDs were measured both before and 1 and 3 months after the placement of pressure equalization tubes. The MLDs were often abnormally small in the otitis media with effusion group before surgery, when hearing loss was present. Significantly, MLDs sometimes remained abnormally small after surgery (after normal hearing had returned). The postsurgery MLD was particularly likely to be abnormally reduced in subjects who had experienced asymmetric losses of hearing.