The intraoperative relationship between intracochlear electrical field and excitability of the auditory nerve

Söderqvist, Samuel; Sinkkonen, Saku T.; Sivonen, Ville

doi:10.1016/j.heliyon.2022.e11970

Cited by 2 publications

(3 citation statements)

References 59 publications

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“…Regarding differences between stimulation electrodes, our results showed an asymmetric profile with broader voltage decays towards the base than towards the apex in MP. These results agree with previous works (Berenstein et al 2010, Tang et al 2011, Lei et al 2021, Kopsch et al 2022, Söderqvist et al 2022, which propose the tapering trend of the cochlea, with reduced volume around apical electrodes and therefore less longitudinal current spread, as an explanation for the asymmetrical profile seen along the cochlea. In this sense, differences in the variability of voltage slopes were also observed in our study, in agreement with Lei et al (2021), showing faster decays towards the base independently of stimulated electrode, and generally slower decays towards the apex, especially for the most apical contacts (figure 5).…”

Section: Ef Spreadsupporting

confidence: 93%

“…In our model, we have seen a more pronounced voltage decay towards the base than in other studies (Bai et al 2019, Joly et al 2021 which may be explained by the cochlear anatomical characteristics of our dataset, parameterized in supplementary table S2. Previous studies have reported that larger cochleae are associated with more focused TIM (Söderqvist et al 2022). The voltage drop has also been reported to be broader in cochleae with larger basal lumen diameter and less tapered cochlear lumen (Lei et al 2021).…”

Section: Model Validation Limitations and Future Workmentioning

confidence: 88%

“…However, the inter-subject variability observed in clinical practice remains unsolved, making the prognosis of individual CI outcomes and the optimal fitting of stimulation parameters challenging (Pisoni et al 2017, Tamati et al 2022. Besides factors related to electrode array insertion and cochlear anatomy (Lei et al 2021, Margeta et al 2022, Schurzig et al 2023, the duration of deafness, the residual neural population (Smulders et al 2018), or the individual neurocognitive capabilities to make effective use of the sound-coded information (Beckers et al 2023), the electric current flow and electric field (EF) patterns induced by CI stimulation may also be an important factor accounting for part of the variability observed (Jiang et al 2020, 2021, Garcia et al 2021, Joly et al 2021, Swaddiwudhipong et al 2021, Kopsch et al 2022, Söderqvist et al 2022, Rader et al 2023. Moreover, the different CI stimulation strategies available to deliver the electric current to specific active and return electrodes have an impact on CI outcomes as well as on reported CI-derived side effects such as facial nerve stimulation (FNS) (Luo et al 2021, Stahl et al 2022.…”

Section: Introductionmentioning

confidence: 99%

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A full-head model to investigate intra and extracochlear electric fields in cochlear implant stimulation

Callejón-Leblic,

Lazo-Maestre,

Fratter

et al. 2024

Phys. Med. Biol.

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Objective: Despite the widespread use and technical improvement of cochlear implant (CI) devices over past decades, further research into the bioelectric bases of CI stimulation is still needed. Various stimulation modes implemented by different CI manufacturers coexist, but their true clinical benefit remains unclear, probably due to the high inter-subject variability reported, which makes the prediction of CI outcomes and the optimal fitting of stimulation parameters challenging. A highly detailed full head model that includes a cochlea and an electrode array is developed in this study to emulate intracochlear voltages and extracochlear current pathways through the head in CI stimulation. Approach: Simulations based on the finite element method were conducted under monopolar, bipolar, tripolar, and partial tripolar modes, as well as for apical, medial, and basal electrodes. Variables simulated included: intracochlear voltages, electric field (EF) decay, electric potentials at the scalp and extracochlear currents through the head. To better understand CI side effects such as facial nerve stimulation, caused by spurious current leakage out from the cochlea, special emphasis is given to the analysis of the EF over the facial nerve. Main results: The model reasonably predicts EF magnitudes and trends previously reported in CI users. New relevant extracochlear current pathways through the head and brain tissues have been identified. Simulated results also show differences in the magnitude and distribution of the EF through different segments of the facial nerve upon different stimulation modes and electrodes, dependent on nerve and bone tissue conductivities. Significance: Full head models prove useful tools to model intra and extracochlear EFs in CI stimulation. Our findings could prove useful in the design of future experimental studies to contrast FNS mechanisms upon stimulation of different electrodes and CI modes. The full-head model developed is freely available for the CI community for further research and use.

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