Recording techniques for transtympanic electrocochleography in clinical practice

Enhancement of the signal-to-noise ratio is a central issue in electrically evoked response techniques. Transtympanic electrocochleography requires careful methodological considerations as responses from the cochlea may easily be affected by various sources of electromagnetic noise. The final electrophysiological waveforms are acquired by advanced signal processing which influences the content of the recordings. A standard method of transtympanic electrocohleography is presented here to increase the feasibility of the measurements in daily clinical use and to facilitate uniform interpretation of the recordings. The electrocochleographic recordings were carried out in 61 patients with a clinical diagnosis of Meniere's disease and in 15 ears of normal hearing subjects. The electrophysiological data are presented and set in relation to the results reported by other laboratories under equivalent recording conditions. Methodological factors of consequence for the quality of the recordings, such as testing environment, properties of the equipment, mode to produce and deliver stimuli and properties of the electrodes, are analysed.