Impedance Change as an Indicator of Cochlear Implant Failure

Investigating mechanical deformation's role in cochlear implant durability

Platinum and platinum-based alloys are used as the electrode material in cochlear implants because of the biocompatibility and the favorable electrochemical properties. Still, these implants can fail over time. The present study was conducted to shed light on the effects of microstructure on the electrochemical degradation of platinum. After three days of stimulation with a square wave signal, corrosive attack appeared on the platinum surface. The influence of mechanical deformation, in particular rolling, on the corrosion resistance of platinum was also prominent. The cyclic voltammetry showed a clear dependence on the electrolyte used, which was interpreted as an influence of the buffer in the artificial perilymph used. In addition, the polarization curves showed a shift with grain size that was not expected. This could be attributed to the defects present on the surface. These findings are crucial for the manufacture of cochlear implants to ensure their long-term functionality.

Cochlear Implant Device Failures Falling Under the 2020 FDA Voluntary Field Corrective Action: A Systematic Review and Meta-analysis

OBJECTIVE

To compare the rate of device failure for those cochlear implants (CIs) involved in the 2020 Food and Drug Administration (FDA) voluntary field corrective action (VFCA).

DATABASES REVIEWED

Medline, Embase, and Scopus.

METHODS

A systematic review was performed according to the PRISMA guidelines. Publications reporting institutional experiences with implants affected by the VFCA were included. Outcomes assessed included etiology of, rate of, and time to failure and pre-/post-device failure speech perception testing. All outcomes reported in at least two independent studies were included in a meta-analysis.

RESULTS

Six studies met criteria for analysis. The overall pooled failure rate was 23.7% (95% CI, 11.6-38.4%). The pooled device, inconclusive, and medical failure rates were 21.5%, 0.2%, and 0.7%, respectively. Pediatric failure rates were higher than those of adults (46.9% [95% CI, 11.2-84.5%] versus 32.6% [95% CI, 8.2-63.7%]). WRS declined with primary implant failure (55.1% [95% CI, 48.0-62.1%] to 34.1% [95% CI, 30.2-38.0%]) but improved after reimplantation (34.1% [95% CI, 30.2-38.0%] to 50.1% [95% CI, 45.2-55.1%]).

CONCLUSIONS

The rate of pooled reported failure for CIs falling under the 2020 VFCA in the literature thus far is 23.7%. The overwhelming majority of these failures were device related, the rates of which were higher in children. Speech perception improved significantly after reimplantation.

Osteoneogenesis at the Round Window: A Possible Cause of Cochlear Implant Failure?

Surgery for cochlear implant is a traumatic procedure, with inflammatory responses leading to immediate and delayed intracochlear changes, resulting in newly formed fibrous and bony tissue. This newly formed tissue is thought to affect speech perception with cochlear implants and can also play a role in causing device malfunctioning and soft failures. We present a case of left cochlear implant explantation and reimplantation in a 15-year-old girl, who experienced deterioration of speech perception and device failure associated with osteoneogenesis of the round window, which could represent a cause of cochlear implant failure. To avoid surgical trauma of the cochlear lateral wall, enlarged round window insertion rather than a cochleostomy, soft surgical techniques, and the application of steroids are all important issues to prevent new tissue formation, although special attention should also be given to the trauma of round window borders.