Long-term electrode impedance changes and failure prevalence in cochlear implants.

OBJECTIVE

This study assessed the prevalence of electrode failures and electrode impedance measures in Nucleus cochlear implants around initial activation (an average of 16 days after surgery) and after 8 to 12 years of device use.

DESIGN

Retrospective data from the Melbourne Cochlear Implant Clinic was collated and analysed.

STUDY SAMPLE

Included in this study were 232 adults, all of whom were implanted at the clinic between March 1998 and August 2005.

RESULTS

Overall 0.5% of electrodes failed over the entire test period, with 5.6% of devices showing one or more electrode failure. The majority of these failures were recorded by initial activation. The numbers of electrode failures have decreased over time with array type, such that no failures were recorded with the currently available Contour Advance array. Array type was shown to affect electrode impedance at both time points, with the Contour and Contour Advance arrays having significantly higher absolute values than the Banded array. However, the Banded array had significantly higher area-normalized impedances at initial and final measures than the Contour and Contour Advance array.

CONCLUSIONS

A relatively low incidence of electrode failures were recorded for the Nucleus devices of these recipients. Electrode impedance dropped for all array types after 8 to 12 years of device use.