Normal Multiple Auditory Steady-State Response Thresholds to Air-Conducted Stimuli in Infants

Background and Purpose: Multiple auditory steady-state responses (ASSRs) to stimuli modulated at similar to 80 Hz are a promising technique for threshold estimation in infants, but additional data are required. Research Design: We obtained multiple ASSRs to air-conducted (AC) stimuli. Study Sample: There were 54 children in two age groups: >six months (N = 32) and <= six months (N = 22). All infants had normal hearing by tone-evoked auditory brain stem response. Results: ASSR thresholds, estimated from 50 percent using cumulative percent present distributions, were 36, 30, 24, and 15 dB HL at 500, 1000, 2000, and 4000 Hz, respectively. Most (>= 90%) of the infants showed present ASSRs at 49, 45, 36, and 32 dB HL at 500, 1000, 2000, and 4000 Hz, respectively, with no differences in the results of younger versus older infants. When responses were present for all stimuli for both ears, most infants showed all eight responses within five minutes. Compared to ipsilateral responses, ASSRs in the contralateral EEG (electroencephalogram) channel were smaller and often absent. Conclusions: Based upon these data and the literature, normal AC ASSR "screening" levels would be 50, 45, 40, and 40 dB HL at 500, 1000, 2000, and 4000 Hz, respectively. Using the multiple-stimulus ASSR, infants with normal hearing referred for diagnostic electrophysiological threshold assessment can now be quickly confirmed as having normal thresholds for four frequencies in both ears.