# A comparison of ABR and ASSR using narrow-band-chirp-stimuli in children with single-sided deafness of various etiology

## TL;DR

This study compares two hearing tests in children with one deaf ear and finds that results differ more when there are inner ear or nerve abnormalities.

## Contribution

The study provides empirical evidence that ABR and ASSR hearing threshold estimates differ significantly in children with cochlear nerve malformations.

## Key findings

- ABR and ASSR showed strong correlation in ears without malformations but weak correlation in cochlear nerve anomalies.
- Ears with cochlear nerve malformation had an average discrepancy of 23.40 dB between ABR and ASSR.
- Large discrepancies between ABR and ASSR thresholds may indicate cochlear nerve anomalies.

## Abstract

Auditory steady-state responses (ASSR) are available for frequency-dependent hearing threshold estimation in addition to the technique of conventional auditory brainstem responses (ABR). Although ABR and ASSR principally show strong correlations in hearing threshold estimation, there is preliminary evidence that temporal bone malformations might be associated with significantly greater differences between ABR- and ASSR-results. Therefore, the present study aimed to compare hearing threshold estimation derived from ABR and ASSR in a larger cohort of single-sided deafness (SSD) of various etiology, including temporal bone anomalies.

The diagnostic consistency between ABR and ASSR using narrow-band-chirp-stimuli at 1000, 2000, and 4000 Hz was analyzed in 47 children with single-sided deafness with varying MRI-morphologic findings: cochlear nerve malformation (CNM, n = 24), cochlear malformation (CM, n = 7) vs. combined malformation (CM + CNM, n = 8) vs. absent temporal bone and inner ear pathology (n = 8). Children with additional health issues other than SSD were excluded.

ABR and ASSR showed a strong correlation in deaf ears without malformation (r = 0.728, p < 0.0001), a moderate correlation in isolated cochlear malformation (r = 0.574, p = 0.01), and a weak correlation in case of cochlear nerve anomaly (r = 0.189, p = 0.112 in CNM and r = 0.235, p = 0.268 in CM + CNM). Ears with isolated CNM showed an average discrepancy of 23.40 ± 15.19 dB, p < 0.00001 between ABR and ASSR (vs. 17.08 ± 15.81 dB, p = 0.0008 in CNM + CM, vs. 7.63 ± 8.56 dB, p = 0.008 in CM, vs. 4.38 ± 4.96 dB, p = 0.036 in ears without malformation and vs. 0.36 ± 4.75 dB, p = 0.748 in healthy control ears). In ears with highly discrepant ASSR and ABR values, enlarged ABR wave I and otoacoustic emissions were frequently present.

In cochlear nerve malformation, ASSR and ABR frequently provide significantly discrepant hearing threshold estimations, probably derived from a cochlear origin. ASSR should only be used in conjunction with conventional ABR in the diagnostic management of suspected severe-profound hearing loss or deafness in children. A large difference between ASSR and ABR thresholds may indicate a cochlear nerve anomaly.