Non-invasive wet electrocochleography

To detect electrocochleographic (ECochG) potentials generated by the cochlea in response to auditory stimuli, either transtympanic or tympanic/extratympanic electrodes are currently used. The first are invasive, while the second are arranged in contact or very close to the tympanic membrane (TM). To avoid the discomfort and the risks inherent to the application of such conventional electrodes, this Letter presents an alternative technique. A conducting liquid is inserted into the ear canal to act as a distributed electrical interface between the TM and an external electrode. Thus, ECochG potentials are detected without any direct contact between the solid electrode and the sensitive TM. This technique was tested on ten volunteers with single-click auditory stimuli. Results showed its efficacy to non-invasively detect useful ECochG responses, with accurate morphology and significant amplitude. The technique is comfortable, sedation/anesthesia-free, inherently safe and easy to perform. It also favors improvements of contact stability, reductions of contact impedance, and relative tolerance to misplacements. As a contraindication, the liquid prevents use on subjects affected by tympanic perforation. All these features encourage further investigations on this technique as a possible additional tool for the ECochG practice.