Waveforms of cochlear implant-evoked auditory brain stem responses in anesthetized young children, recorded with a...

An ultra-low-noise preamplifier has been specifically designed for the conditions in lightly anesthetized young children, to record cochlear implant--evoked auditory brain stem responses (impEABRs). The preamplifier linearly filters out the signal from the radio-frequency implant-driver. The preamplifier provides simultaneous accurate records of the stimulus-current artifact and impEABR, both ipsilaterally and contralaterally. It is convenient to label electrically evoked vertex-positive peaks, eg, eII, on probable analogy with acoustically evoked potentials. In order to label all the commonly observed peaks with latency less than 5 milliseconds, it is necessary at times to use labels eIIa, eIIb, eIIIa, eIIIb, eIVa, eIVb, eVa, and eVb. The records also show two distinct nadirs, with latencies about 2.5 milliseconds and about 6 milliseconds. The details of the waveforms are preserved as the stimulus strength descends towards threshold.