Prediction of frequency-specific hearing threshold using chirp auditory brainstem response in infants with hearing losses.

OBJECTIVES: To investigate the clinical usefulness of the LS-chirp auditory brainstem response for estimation of behavioral thresholds in young children with mild to severe hearing losses. METHODS: 68 infants (136 ears) aged 6-12 months (mean age=9.2 months) with bilateral mild to severe hearing losses were studied at Children's Hospital of Fudan University. In all cases, the children were referred for LS-chirp ABR and visual reinforcement audiometric (VRA) measurements. The low-frequency band chirp (LF-chirp) thresholds (frequency band=0.1-0.85kHz) were compared to the average VRA thresholds (frequency band=0.25-0.5kHz), whereas the high-frequency band chirp (HF-chirp) thresholds (frequency band=1-10kHz) were compared to the average VRA thresholds (frequency band=1-4kHz) using statistical correlation coefficient values. RESULTS: The LS-chirp ABR thresholds are very close to behavioral hearing levels. The mean differences between chirp-ABR and VRA thresholds were within 5dBHL for all measurements. The smallest mean threshold difference (<3dBHL) was obtained for the severe hearing loss group. The correlation coefficient values (r) were 0.97 at low-frequency and high-frequency bands. For each carrier frequency, the best correlations between chirp-ABR thresholds and VRA thresholds were obtained at VRA frequency of 0.25kHz/LF-chirp (r=0.98) and VRA frequency of 1kHz/HF-chirp (r=0.98). CONCLUSIONS: This study demonstrates the effectiveness using chirp-ABR predicted frequency-specific thresholds, especially of low and middle frequencies. LS-chirp ABR thresholds determined behavioral thresholds in patients with severe hearing losses were better than for mild hearing losses. The use of a chirp-ABR testing ensures higher sensitivity and accuracy than that of auditory stead-state evoked response (ASSR) for measuring frequency-specific thresholds in young children.