An investigation into the clinical utility of ipsilateral/contralateral asymmetries in bone-conduction auditory steady-state responses.

Objective: To determine whether ipsilateral/contralateral asymmetries in the bone-conduction (BC) ASSR are robust enough in infants to be used clinically to isolate the test ear.

Methods: Retrospective investigation of three two-channel BC ASSR datasets. Methods: Forty-eight adults (mean age 26.7 years), 49 infants (mean age 29.6 weeks). Methods: BC ASSR stimuli were presented as amplitude/frequency modulated sinusoidal tones with carrier frequencies of 500, 1000, 2000, and 4000 Hz (-10 to 45 dB HL).

Results: Infants showed greater differences in ipsilateral/contralateral mean amplitudes and phase delays for all experimental conditions compared to adults. Ninety percent of infants had ipsilateral/contralateral asymmetries at 500 and 4000 Hz (20-35 dB HL) using an "amplitude or phase delay" criterion, and at 4000 Hz (20-25 dB HL) using an "amplitude and phase delay" criterion.

Conclusions: As ipsilateral/contralateral asymmetries are not consistently present for 1000- and 2000-Hz BC ASSRs in infants, clinical masking would be needed at these frequencies to isolate the test ear. For 500- and 4000-Hz BC ASSRs, the accuracy of using these asymmetries requires clinical confirmation in a group of infants with hearing loss.