Using concha electrodes to measure cochlear microphonic waveforms and auditory brainstem responses.

Abstract

During electrocochleography, that is, ECochG or ECoG, a recording electrode can be placed in the ear canal lateral to the tympanic membrane. We designed a concha electrode to record both sinusoidal waveforms of cochlear microphonics (CMs) and auditory brainstem responses (ABRs). The amplitudes of CM waveforms and Wave I or compound action potentials (CAPs) recorded at the concha were greater than those recorded at the mastoid but slightly lower than those recorded at the ear canal. Wave V amplitudes recorded at the concha were greater than those recorded at the ear canal but lower than those recorded at the mastoid. There was not a significant difference between the amplitudes recorded at the concha and at the ear canal. For CM and Wave I or CAP, the latency recorded at the concha was longer than at the canal but shorter than at the mastoid; for Wave V, the reverse was true. However, these differences were not statistically significant and may be due to the distance to response generators. Aside from the advantages that the regular ECoG has over otoacoustic emission (OAE) testing, the concha electrode was also easier and safer to place and may be suitable for children, newborn screening, participants with canal conditions, and remote clinics which could have concerns with the availability and cost of a canal electrode. Using concha electrodes, we also experienced fewer postauricular artifacts than when using a mastoid electrode.