Comparison between electrocochleography (ECochG) and auditory brainstem response (ABR) recordings in hearing threshold assessment in children.

In the assessment of hearing threshold in children, ABR reliability is greatly reduced in the presence of altered synchrony or brainstem generator dysfunction, while electrocochleography (ECochG) still provides a reliable threshold evaluation. This study is drawn from a retrospective analysis performed in 459 children submitted to ECochG and ABR recordings with the aim of comparing the reliability of the two procedures in hearing threshold estimation. Transtympanic ECochG and ABR were recorded under general anesthesia in response to 0.1 ms clicks at decreasing intensities from 90 dB nHL. In 98% of the ears threshold estimates for ECochG compared to ABR recordings were lower (50%) or equal (47%). In 77 % of the ears these differences were found within 20 dB. In this group the percentage occurrence of ears in subjects affected by CNS pathology or bearing a neonatal risk factor for hearing loss was 40%; in the remaining 20% of the ears, where threshold differences were higher than 20 dB, the percentage was 17%. It can be concluded that, when dealing with children presenting a CNS dysfunction, electrocochleography is the only reliable diagnostic tool in hearing threshold estimation because of low ABR reliability, possibly related to an altered synchrony in brainstem generator.