Abstract
Ase et al. reported qualitative difference between wave I produced by ipsilateral stimulation and wave I delivered by contralateral stimulation using bone conducted ABR. In this study an attempt has been made to determine whether or not such a difference could be elicited from the examination of compound action potential that has been generated from bone conducted electrocochleography (ECochG), based on subjects with normal hearing.
The results show a definite difference of the threshold, the latency-intensity function and the input-output function between the ipsilateral stimulation and the contralateral one. Increased threshold, prolonged latency and decreased amplitude of AP were among the characteristics found in the ECochG which was obtained from the contralateral stimulation. These differences between the two stimulations might have been explained not only by the interaural attenuation factor of less than 10dB, but also by the conduction time from the contralateral mastoid to the inner ear examined. Furthermore, radiated aerial sounds emitted from a bone conduction vibrator may not be ignored as one of the factors responsible for this difference.
Appliciation of this study for ears with conductive hearing loss requires further assessment that includes the distortion of signals, the difference of sound energy emitted to the right and the left ear canal. the phase difference, the masking effect on air conduction as well as those factors noted in this report.
