Towards unblinding the surgeons: Complex electrical impedance for electrode array insertion guidance in cochlear implantation

  • Nauman Hafeez Institute of Environment, Health and Societies, Brunel University, London, UK
  • Xinli Du Institute of Environment, Health and Societies, Brunel University, London, UK
  • Nikolaos Boulgouris Institute of Environment, Health and Societies, Brunel University, London, UK
  • Philip Begg University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK
  • Richard Irving University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK
  • Chris Coulsan University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK
  • Guillaume Tourrels Oticon Medical Neurelec Inc., Vallauris, France

Abstract

The complications during electrode array insertion in scala tympani for cochlear implantation may cause trauma, residual hearing loss and affect speech outcomes. The inner ear is like a black box for surgeons during the insertion process with no real-time feedback and must rely on radiation- based extraoperative imaging. Impedance measurement of electrodes during insertion is a simple yet effective method to assess array position. For this, an impedance meter has been designed which can measure magnitude (|Z|), phase (θ), real (R) and imaginary (Xc) parts of impedance. A switching circuit can sequentially scan all electrode pairs at regular intervals during insertion. An Evo straight electrode array is inserted in a transparent 2:1 scaled up 2D cochlear model (11 trials) filled with 0.9% saline using a 3-degrees-of- freedom actuation system. Bipolar impedance measurements of 8 pairs (40 samples each) are taken at regular intervals during 25 mm insertion at speed of 0.05mm/sec. A notable increase in |Z| and R is observed in the apical 3 electrode pairs when they first get in to contact with the lateral wall. At the same time, the phase gets less negative (more resistive impedance) and Xc increases (less capacitance). These results show that impedance can be used for electrode array localization in cochlea and impedance change due to electrode proximity to different materials can have application in other electrode implants.

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Published
2020-04-20
How to Cite
Hafeez, N., Du, X., Boulgouris, N., Begg, P., Irving, R., Coulsan, C., & Tourrels, G. (2020). Towards unblinding the surgeons: Complex electrical impedance for electrode array insertion guidance in cochlear implantation. Proceedings of the International Symposium on Auditory and Audiological Research, 7, 29-36. Retrieved from https://proceedings.isaar.eu/index.php/isaarproc/article/view/2019-04
Section
2019/1. Auditory precision medicine