[Effect of binaural conductive hearing loss on maturation of acoustically evoked potentials (auditory brain stem response, middle latency response) in guinea pigs].

During the early development of the acoustic system a conductive hearing loss may alter the maturation of acoustically evoked potentials and affect the development of hearing. The present experiments were carried out in newborn guinea pigs with binaural conductive hearing loss. The external ear canals were plugged over a period of one month from the first day postpartum. During and after deprivation click-evoked Auditory Brainstem Responses (ABR) and Middle Latency Responses (MLR) were collected to analyze changes in the maturation of these potentials in comparison to untreated animals. This type of deprivation is characterized by threshold elevations of about 40 dB over a wide frequency range. In young deprived animals, ABR Latencies (PIII, PV) and interpeak latencies exhibited a significant delay with a maximum between day 13 and 19, which disappeared within 10 days after the end of the treatment. MLR latencies were also significantly affected after three to four weeks of the deprivation phase. In contrast to the ABR, the recovery of the latencies was completed within four to six weeks. These results therefore indicate that a conductive hearing loss may alter the maturation of the acoustically evoked responses in the sensitive phase after birth. This type of partial deprivation may affect the development of hearing and speech perception in children with chronically occurring otitis media.