Objective: This study aimed to determine the clinical value of air-and bone-conduction auditory brainstem responses (ABRs) in children with congenital external auditory canal atresia (EACA).Methods: Air-and bone-conduction click-evoked ABRs in 38 children having congenital EACA were compared with 34 children having normal hearing.Results: ABR threshold for air and bone conduction were 66.53 ± 7.12 and 12.55 ± 6.96 dBnHL, respectively, in children with congenital EACA, as well as 25.32 ± 2.66 and 10.71 ± 4.51 dBnHL, respectively, in children with normal hearing. The two groups showed statistical difference in air-conduction ABR thresholds. Meanwhile, air-bone ABR threshold gap was greater in children with EACA than in children with normal hearing, and bone-conduction ABR wave latencies did not statistically differ between the two groups.
Conclusion:Bone-conduction ABR is valuable in assessing the function of cochlea, auditory nerve, and brainstem in individuals with congenital EACA. The study has important clinical value in the objective differential diagnosis of conductive deafness with combined application of air-and boneconduction ABRs.
Subjects and Methods
SubjectsData from 38 infants (50 ears) aged 1-12 months (mean age = 4.6 months) diagnosed with EACA were collected from Children's Hospital of Fudan University between August 2014 to March 2015. The subjects were 28 boys, of which 12 cases were bilateral. Furthermore, the control group consisting of 34 normal infants (68 ears) aged 1-9 months (mean age = 4.1 months) were subjected to otoscopy, tympanometry, otoacoustic emission, and ABR; No hearing losses were reported among the children. For 38 ECAA infants, CT scan and ABR were used to diagnosis and assessment. This work was approved by the Ethics Committee of Children's Hospital of Fudan University and conducted in accordance with the ICH guidelines for Good Clinical Practice and the Declaration of Helsinki. All of the subjects in the study signed an informed consent form.
Air-and bone-conduction ABR measurementAir-and bone-conduction ABRs were performed in a soundproof room. All test subjects orally received 0.5 ml/kg dose of 10% chloral hydrate to induce a 'deep' sleep. Air-and bone-conduction ABRs were measured with a GSI Audera Brainstem Analyzer using Model TDH-39P headphone and AD229 earphone, respectively. Silver disc electrodes were placed on the forehead (active), nasion (ground), and earlobe (reference) for air-conduction ABR. When bone-conduction was performed, the AD299 earphone was placed on the mastoid bone without moving the reference electrode. The band pass filter settings were 100 and 2500 Hz (bone ABR, 50-1500 Hz) with a 10 Ms window