[Impedance of cochlear implant electrode array in scalae tympani].

OBJECTIVE: To study the relationship between the impedance of paired cochlear implant electrodes and their position in scalae tympani as well as the relationship between the impedance and the current frequency. METHODS: REZ-1 electrodes were implanted in 6 fresh human adult temporal bone specimens. Alternating electrical source was used. A 1 Kohm resistance was in series with the paired electrodes. The voltages of the resistance and the sum voltages of both the paired electrodes and the resistance were recorded. Thus, the impedances of paired electrodes could be calculated. The impedances of neighboring paired electrodes and paired electrodes separated by one electrode were calculated. The frequencies of signals were 2 Hz, 10 Hz, 100 Hz, 1 KHz, and 10 KHz respectively. RESULTS: The impedances of neighboring electrodes increased, as the electrodes were closer to the apical turn of the cochlea (liner regression, F = 198.97, P < 0.001). The impedances of paired electrodes separated by one electrode increased, as the electrodes were closer to the apical turn of the cochlea (liner regression, F = 126.35, P < 0.001). The impedance decreased when the frequency increased. CONCLUSIONS: The impedances of neighboring electrodes increase, as the electrodes are closer to the apical turn of the cochlea. The impedances of neighboring paired electrodes increase, as they are closer to the apical turn in the scalae tympani. The impedances of paired electrodes that are separated by one electrode increase, as they are closer to the apical turn in the scalae tympani. The impedance decreases when the frequency increases.