Auditory steady-state response and auditory brainstem response thresholds in children.

The inclusion of the auditory steady-state response (ASSR) into test-batteries for objective audiometry has allowed for clinical comparisons with the most widely used procedure, the auditory brainstem response (ABR). The current study describes ASSR and ABR thresholds for a group of infants and young children with various types and degrees of hearing loss. A sample of 48 subjects (23 female) with a mean age of 2.8+/-1.9 years SD were assessed with a comprehensive test-battery and classified according to type and degree of hearing loss. Thresholds were determined with a broadband click-evoked ABR and single frequency ASSR evoked with continuous tones (0.25-4 kHz) amplitude modulated (67-95 Hz). Mean difference scores (+/-SD) between the ABR and high frequency ASSR thresholds were 9.8 (+/-11), 3.6 (+/-12) and 10.5 (+/-12) dB at 1, 2 and 4 kHz, respectively. An ASSR mean threshold for 2-4 and 1-4 kHz compared to the ABR threshold revealed an average difference of 7 (+/-9) and 7.9 (+/-8) dB, respectively. The overall correlation between the ABR and ASSR thresholds was highest for the mean ASSR thresholds of 2-4 and 1-4 kHz (r=0.92 for both conditions). Correlations between the ABR and individual ASSR frequencies were slightly less (0.82-0.86). The average of the 2-4 kHz ASSR thresholds correlated best with the click-evoked ABR for all categories of hearing loss except for the sensorineural hearing loss category for which the 1-4 kHz ASSR average was better correlated to ABR thresholds. Findings demonstrate the reliability of verifying high frequency ASSR thresholds with a click-evoked ABR as an important cross-check in infants for whom behavioural audiometry may not be possible.