Hidden Electrode Failure in a Cochlear Implant User

Abstract

When the impedance of an electrode contact is highly increased in a cochlear implant, a failure of the appropriate electrode seems obvious. We present a case where impedances of some electrodes were at the lower edge of the normal range and not regarded as suspicious neither by the clinical fitting software nor by in-vivo tests conducted by the implant manufacturer. However, speech comprehension was substantially degraded and sound perception distorted. Also, on the affected electrodes, loudness perception was compromised and responses of the electrically evoked compound action potential were no longer measureable. After re-implantation, the subjective sound percept was clear again and speech comprehension scored much better than before. Later, inspection of the explant revealed shorts on the device and the implant was classified as device failure. Our case shows the importance of collecting longitudinal data of cochlear implant patients, i.e. device related technical measurements and hearing performance data, and the consideration of all these data in cases of patient complaints or suspected implant failures.

Cochlear reimplantation from mid‐scala to lateral wall electrode array: Surgical and hearing outcome

“…The HSM test score in noise had dropped to 31% correct and the German Freiburg monosyllabic word score in quiet to 45% correct. An implant check showed the typical constellation of electrophysiological measurements including low electrode impedances in combination with lack of increase in loudness growth perception, suggesting technical device failure as already published in a similar case with this implant series 5 . Detailed unbiased counseling about all technical options and surgical risks has been carried out.…”

“…An implant check showed the typical constellation of electrophysiological measurements including low electrode impedances in combination with lack of increase in loudness growth perception, suggesting technical device failure as already published in a similar case with this implant series. 5 Detailed unbiased counseling about all technical options and surgical risks has been carried out. The patient was concerned that the problem with the hermetic seal may not have been successfully resolved with the new implant series and therefore chose to change the device manufacturer and hereby the electrode array type (Synchrony 2 implant coupled with FLEX 28 electrode, MED‐EL).…”

Cochlea-Implantation: Konzept, Therapieergebnisse und Lebensqualität

“…These registries require the cooperation of possibly all cochlearimplanting institutions in order to obtain complete datasets. At the same time, standardized criteria for definition, classification, and reporting must be applied [72]. Different international standards have been established for a multitude of active implant systems that are generally applied also for cochlear implant systems.…”

“…Dieses Implantat verfügt über einen grundsätzlich anderen Stimulationsmodus mit sogenannter pseudo-monopolarer Stimulation und einer kombinierten Common-Ground-Elektrode. Beides führt zu einer deutlichen Reduktion der Feldausbreitung innerhalb der Cochlea und insbesondere zu einer kleineren Amplitude der für die Facialisreizung verantwortlichen kathodischen Phase des biphasischen elektrischen Reizes(73).…”

Advanced Bionics HiRes Ultra and Ultra 3D Series Cochlear Implant Recall: Time Course of Anomalies

“…At our clinic, anomalies in the affected CI series were first noticed during a follow‐up in April 2019 in a HiRes Ultra Mid‐Scala implant. On individual electrodes, the impedance dropped, the current level to elicit a comfortable loudness perception (so‐called M‐level) increased, the amplitude of the electrically evoked compound action potential (ECAP) decreased, and speech recognition was degraded 3 . This is a new pattern specific to this type of failure.…”