The Application Of Auditory Brain Stem Responses(ABR) To Air-and Bone-conducted Clicks In Children With Congenital Atresia Of Theexternal Auditory Canal

Objective To study the characteristic of auditory brain stem assessment of the external auditory canal. To evaluate the usefulness of BC-ABR in hearing assessment of children with congenital malformations of the external ear. Methods Two groups were investigated: group 1, 16 children aged 1-13years, with congenital malformations of the external ear; group 2, 15 normal-hearing children aged 1-13 years. For AC-ABR recording, the reference electrode was placed on the mastoid process ipsilateral to the stimulated side, and the live and ground electrodes were placed on the forehead. Ari-conduction stimuli were presented using TDH–49 headphones. For BC-ABR recording we used a Radioear B-71 bone vibrator deployed on the postero-superior ear portion. The lead should be placed on the earlobe. If there is no earlobe, keeping it in the posterosuperior ear region and the vibrator should be placed as much away as possible from it. Comparison between ABR by AC and BC for two groups is discussed. Date were analyzed by SPSS. Results The latency of the air and bone conducted ABR wave V for normal-hearing children were 7.72±0.54ms and 6.88±0.43ms, respectively, there were significant differences between them. The mean ABR thresholds to air and bone conducted clicks for group 1 were 73.81±7.4dBnHL and 6.19±4.98 dBnHL, respectively, and for group 2, 23.20±4.76 dBnHL and 5.60±5.07 dBnHL. The air-bone gap of ABR thresholds between two groups had statistically significant differences. As to AC wave V latency time, at 80 dBnHL, for group 1 and group 2 were 7.24±0.35 ms; and 5.72±0.23 ms, there were notable differences between them. As to BC wave V latency time, at 30 dBnHL, for group 1 and group 2 were 6.94±0.29 ms and 6.88±0.43 ms, there were no statistically significant differences in them. Conclusion BC-ABR is essentially to assess cochlear reserve. The air-bone gap of ABR could differentiate sensorineural from conductive hearing impairments. These provide most important inforation to clinician for early intervention of subjects with congenital atresia of the external auditory canal.