A Study Of Visual Reinforcement Audiometry In Normal Infants Of 6-24 Months

Objective The aim of this study was to obtain the minimal response levels (MRLS) for visual reinforcement audiometry (VRA) in normal hearing infants of 6-24months; to discuss the skill of VRA in clinical work.Methods The subjects were 96 normally developing infants aged between 6 and 24 months who did physical examination in our hospital. Asked birth history and family history etc, examined infants'ears with an electric auriscope, did distortion-product otoacoustic emissions (OAE) and Tympanometry of 1000Hz when infants came to our department. Only all results of these tests were nomal, the infant could be included in our study. VRA was carried out using loud speakers or insert earphones with pure tone frequency modulation (warble) stimuli, generated from a Tinitest audiometer. The reinforcer which we used in the study were computer animation. If we could't got all MRLs of a infant within the first test session, we did the second session after a period of time. And sometimes had to did the third session.The frequencies assessed were 500Hz, 1000Hz,2000Hz,4000Hz.Results VRA with stimuli presented by loud speakers:Mean MRLs of 500Hz, 1000Hz,2000Hz,4000Hz were 31.23 dB,32 dB,30.75 dB,30.88 dB. There were no statistical difference between the mean MRLs of left and right ears. And we didn't found statistical difference between different sexs. Mean MRL of 500Hz of 6-12 months infants was 32.92 dB. It was 28.44 dB of 12-24months infants.There were statistical difference between them when we analyzed them with One-Way ANOVA of SPSS. VRA with stimuli presented by insert phones:Mean MRLs of 500Hz,1000Hz,2000Hz,4000Hz were 10.23 dB,9.65 dB,8.80 dB,8.12 dB Infants from the group of 6-12months presented higher MRL for the frequency modulated pure tone than the other age groups when VRA was presented through insert earphones. No difference was found between the mean MRLs of boys and girls.Conclusion Mean MRLs of VRA with stimuli presented by loud speaker are higher than these with stimuli presented by insert phones. And mean MRLs descend with age increasing. Gender do insignificant effect on mean MRLs.