SCINSEVs (Stimulation-Current-Induced Non-Stimulating Electrode Voltage recordings) are measurements of the electrical voltage spread at the level of the cochlear-implant electrodes when stimulating at individual electrodes. They are referred to as Trans-Impedance Matrices (TIMs) in Cochlear devices, Electrical Field Imaging (EFIs) in Advanced Bionics Devices, and Voltage Matrices (VMs) in MEDEL devices. Although sometimes confused with direct impedance values, they are voltage measurements recorded at all non-stimulating electrodes in response to stimulation at each stimulating electrode in a cochlear implant, scaled by the input current at the stimulating electrode. As the input current and measured voltage are measured at different locations, the values represent scaled voltages.
A number of scientists and clinicians (especially within Cambridge, UK) use these measures both for research purposes and in clinic to identify cases of extracochlear electrodes or electrode extrusion. Approaches range from automatic detection from simple visual inspection of the SCINSEV plots for identification of extra-cochlear electrodes. As these are quick measurements that can be done intra-operatively, they can be used to identify cases of partial insertion during surgery, during a critical window when it is possible to correct. They can also be used after cochlear-implant surgery to identify cases of extrusion, and to take this into consideration during clinical appointments for programming individual patients’ cochlear-implant settings. I have been involved in some of this development research, the details of which can be found below.
References
de Rijk, S. R., Boys, A. J., Roberts, I. V., Jiang, C., Garcia, C., Owens, R. M., & Bance, M. (2023). Tissue-Engineered Cochlear Fibrosis Model Links Complex Impedance to Fibrosis Formation for Cochlear Implant Patients. Advanced Healthcare Materials, 12(24), 2300732. https://doi.org/10.1002/adhm.202300732
de Rijk, S. R., Hammond-Kenny, A., Tam, Y. C., Eitutis, S. T., Garcia, C., Carlyon, R. P., & Bance, M. (2022). Detection of Extracochlear Electrodes Using Stimulation-Current- Induced Non-Stimulating Electrode Voltage Recordings With Different Electrode Designs. Otology & Neurotology, 43(5), e548. https://doi.org/10.1097/MAO.0000000000003512
Manuscripts under Review:
*Borsetto, D., *Garcia, C., Salorio-Corbetto, M., Eitutis, S., Carlyon, R.P., Tysome, J., Donnelly, N., Axon, P., Smith, M., Swords, C., Tam, Y.C., McKenny, S., Deeks, J., Bysouth-Young, D., and Bance, M. (submitted, under review). Intraoperative Application of Stimulation Current Induced Non-Stimulating Electrode Voltages for Visual Identification of Extra-cochlear Electrodes in Cochlear implantation. (*joint 1st authors)
Charlotte Garcia 