Detection of Extracochlear Electrodes Using Stimulation-Current- Induced Non-Stimulating Electrode Voltage Recordings With Different Electrode Designs

Abstract

Hypothesis: Stimulation-Current-Induced Non-Stimulating Electrode Voltage Recordings (SCINSEVs) can help detect extracochlear electrodes for a variety of Cochlear Implant (CI) devices. Background: Extracochlear electrodes (EEs) occur in 9 to 13% of cochlear implantations and commonly go unnoticed without imaging. Electrodes on the electrode array located extracochlearly are associated with non-auditory stimulation and a decrease in speech outcomes. We have previously shown that SCINSEVs, with hardware and software from one manufacturer, could detect EEs. Here, we test the generalizability to other manufacturers. Methods: Fresh-frozen human cadaveric heads were implanted with Cochlear Ltd. CI522 (CI-A) and MED-EL's FLEX24 (CI-B) electrodes. Contact impedances and SCIN-SEVs were measured, with Cochlear Ltd. research Custom Sound software (Transimpedance Matrix) and MED-EL's clinical MAESTRO (Impedance Field Telemetry), for full insertion and EEs in air, saline and soft tissue. An automated detection tool was optimized and tested for these implants.Intra-operative SCINSEVs with EEs were collected for clinical purposes for six patients. Results: The pattern of SCINSEVs changed in the transition zone from intracochlear to extracochlear electrodes, even with low contact impedances on EEs. Automated detection in the cadaveric specimens, with two or more EEs in saline or soft tissue, showed a mean 91% sensitivity and specificity for CI-A and 100% sensitivity and specificity for CI-B. Quantification of EEs showed significant correlations of r ¼ 0.69 between estimated and actual EEs for CI-A and r ¼ 0.76 for CI-B. Conclusion:The applicability of SCINSEVs to detect extracochlear electrodes could be expanded to other cochlear implant companies despite differences in electrode array design and measurement software.

A scoping review on the clinical effectiveness of Trans-Impedance Matrix (TIM) measurements in detecting extracochlear electrodes and tip fold overs in Cochlear Ltd devices

“…Studies were conducted in North America-the United States [ 33 ], Europe- including the United Kingdom [ 32 ], Netherlands [ 24 , 28 ], Germany [ 26 ], Finland [ 25 ], Italy [ 30 ], Spain [ 27 ], Belgium [ 31 ], Asia Pacific-Australia [ 34 ]. One study was an international multicentre collaboration (Australia, Germany, and Spain) [ 29 ].…”

“…Only three studies were prospective longitudinal [ 27 , 29 , 31 ], by measuring TIM intraoperative and at postoperatively (01,03,06 and 12 months) to predict CI outcome as a function of electrode array position. Six studies were retrospective in nature [ 25 , 26 , 28 , 32 , 33 , 34 ]. One [ 24 ] was a proof-of-concept study examining the potential use of TIMs in intraoperative measurements [ 30 ], and one study [ 29 ] was a prospective multicentre study designed for the detection of TFO.…”

A Multicenter Comparison of 1-yr Functional Outcomes and Programming Differences Between the Advanced Bionics Mid-Scala and SlimJ Electrode Arrays

“…In addition, electrode migration after initial imaging cannot be ruled out as repeat x-rays are typically only requested after trauma or large unexplained changes in performance. To accurately detect migration and extracochlear electrodes, routine monitoring of x-rays, computed tomographies or more practically, electrical field imaging (EFI) (66,67) is required to compare with intraoperative results. As electrode movement has implications for sound quality, the ability to monitor electrode position may help detect changes in placement that may require programming modifications.…”

Transimpedance Matrix Can Be Used to Estimate Electrode Positions Intraoperatively and to Monitor Their Positional Changes Postoperatively in Cochlear Implant Patients

“…Hoppe et al (5) used TIM in a multicenter study to detect tip fold-over by extracting the phase from the gradients of TIM and evaluating the histogram of the phases with high sensitivity and specificity. Furthermore, De Rijk et al showed that TIM can be used to detect electrode migration (11,15).…”