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Abstract
The objective of this study was to investigate electrode impedance in cochlear implant recipients in relation to electrically evoked stapedius reflex measurements during surgery, and to electrode design, stimulation mode, and T and C levels over a nine month period after surgery. Seventy-five implant recipients, implanted with a Nucleus straight electrode array or a Contour array, were included. The results show that: (1) during surgery electrode impedance decreases markedly after electrically evoked stapedius reflex measurements, (2) after surgery, during the period without stimulation until speech processor switch-on, impedance increases, (3) after processor switch-on impedance decreases. The lower impedance values after a period of stimulation are found at the higher T and C levels. Impedances of the straight array electrodes are lower than those of the Contour array. The difference corresponds mainly to their respective surface areas. In addition, the straight array shows a larger increase of impedance in the apical direction than the Contour array, probably because of the larger fluid environment around the basal electrodes of the straight array.
Sumario
El objetivo de este estudio fue investigar la impedancia de los electrodos en implantados cocleares en relación con medidas de reflejo estapedial evocado eléctricamente durante la cirugía, con el diseño del electrodo, el modo de estimulación, y los niveles T y C durante los 9 meses siguientes a la cirugía. Se incluyeron setenta y cinco sujetos implantados con un electrodo Nucleus recto o con uno Contour. Los resultados muestran que, 1) la impedancia de los electrodos disminuye marcadamente después de las mediciones del reflejo estapedial evocado eléctricamente, durante la cirugía, 2) la impedancia aumenta después de la cirugía, durante el período sin estimulación y hasta la activación de procesador de lenguaje, 3) después de la activación del procesador la impedancia disminuye. Se encontró que los menores valores de impedancia después de un periodo de estimulación se encuentran en los niveles T y C más altos. Las impedancias de los electrodos rectos son más bajas que aquellas del Contour. La diferencia corresponde a sus respectivas áreas de superficie. Además, los electrodos rectos muestran un incremento mayor de la impendacia en la dirección apical que los electrodos Contour, probablemente debida al ambiente con más líquido alrededor de los electrodos basales de los electrodos rectos.
| Acronyms | ||
| T level | = | Threshold hearing level |
| C level | = | Maximum comfortable loudness level |
| CG | = | Common ground stimulation mode |
| MP1 | = | Monopolar stimulation mode against submuscularly placed reference electrode |
| SPEAK | = | Spectral peak speech coding strategy |
| ACE | = | Advanced combination encoder speech coding strategy |
| ESR | = | Electrically evoked stapedius reflex |
| ECAP | = | Electrically evoked compound action potential |
| Acronyms | ||
| T level | = | Threshold hearing level |
| C level | = | Maximum comfortable loudness level |
| CG | = | Common ground stimulation mode |
| MP1 | = | Monopolar stimulation mode against submuscularly placed reference electrode |
| SPEAK | = | Spectral peak speech coding strategy |
| ACE | = | Advanced combination encoder speech coding strategy |
| ESR | = | Electrically evoked stapedius reflex |
| ECAP | = | Electrically evoked compound action potential |