The effect of electrode position in electrocochleography

This study assessed the effect of needle electrode position on the human cochlear summating potential (SP) obtained by transtympanic electrocochleography (ECochG). Electrocochleography was performed on 10 subjects with large central tympanic membrane perforations with good cochlear function, and in whom a needle electrode could be accurately placed in a series of five pre-determined positions in the middle ear. A comparison of the electrocochleograms revealed a wide scatter of results between different positions in the same patient and between similar positions in different patients. Only when the needle was repositioned at an almost identical recording site in the same subject, was good reproducibility achieved. Such a wide and unpredictable variation in results would suggest great caution is needed when comparing traces obtained using a transtympanic technique which precludes a view of the electrode tip.