OPTIMAL ELECTRODE POSITIONS FOR ABR-REORD ING IN PEDAUDIOLOGY

Background: Estimation of hearing threshold in children is based on re liable identification of a response to a stimulus in the near-threshol d range. It is well known that only wave V can be detected in brainste m potentials evoked by near-threshold stimuli. So the question arises as to whether or not a noncephalic reference electrode compared to the common lateral position of the reference electrode on the ipsilateral mastoid produces a more stable wave V of increased amplitude. Method: Thirty-three normal hearing children in three age groups (<6 years, 6 -10 years, >10 years) were investigated. For a near-threshold stimulat ion with 100-mu s-clicks (10,20,30 dB nHL), bioactivity was simultaneo usly recorded with the reference electrode in four different locations (ipsilateral mastoid, contralateral mastoid, ipsilateral earlobe, and noncephalic electrode). Results: The noncephalic reference produced t he highest absolute and scaled amplitudes. This finding was statistica lly significant. For all investigated intensities, recording with the noncephalic reference electrode yielded the highest number of reliable detectable potentials. Evaluation of the residual noise in the four r ecording locations revealed a significantly increased noise level for the noncephalic electrode at the nape of the neck. Conclusions: Even i f the residual noise is increased, the use of noncephalic reference re sults in a more reliable detection of wave V compared to the conventio nal locations of the reference electrode.