Evolution of impedance field telemetry after one day of activation in cochlear implant recipients

Hu, Hao-Chun; Chen, Joshua Kuang‐Chao; Tsai, Chia-Mi; Chen, Hsing‐Yi; Tung, Tao‐Hsin; Li, Lieber Po‐Hung

doi:10.1371/journal.pone.0173367

Cited by 28 publications

(47 citation statements)

References 31 publications

(69 reference statements)

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“…These measurements were started in PBS, with three consecutive measurements performed; only afterwards were impedance levels measured in the MSC medium, again three times. Electrode impedance decreases after activation in an animal model (Wilk et al, 2016) and in humans (Hu et al, 2017). Therefore, the impedances were expected to be lower in the MSC medium than in PBS.…”

Section: Discussionmentioning

confidence: 99%

Stem Cell Based Drug Delivery for Protection of Auditory Neurons in a Guinea Pig Model of Cochlear Implantation

Scheper

Hoffmann

Gepp

et al. 2019

Front. Cell. Neurosci.

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Background: The success of a cochlear implant (CI), which is the standard therapy for patients suffering from severe to profound sensorineural hearing loss, depends on the number and excitability of spiral ganglion neurons (SGNs). Brain-derived neurotrophic factor (BDNF) has a protective effect on SGNs but should be applied chronically to guarantee their lifelong survival. Long-term administration of BDNF could be achieved using genetically modified mesenchymal stem cells (MSCs), but these cells should be protected – by ultra-high viscous (UHV-) alginate (‘alginate-MSCs’) – from the recipient immune system and from uncontrolled migration. Methods: Brain-derived neurotrophic factor-producing MSCs were encapsulated in UHV-alginate. Four experimental groups were investigated using guinea pigs as an animal model. Three of them were systemically deafened and (unilaterally) received one of the following: (I) a CI; (II) an alginate-MSC-coated CI; (III) an injection of alginate-embedded MSCs into the scala tympani followed by CI insertion and alginate polymerization. Group IV was normal hearing, with CI insertion in both ears and a unilateral injection of alginate-MSCs. Using acoustically evoked auditory brainstem response measurements, hearing thresholds were determined before implantation and before sacrificing the animals. Electrode impedance was measured weekly. Four weeks after implantation, the animals were sacrificed and the SGN density and degree of fibrosis were evaluated. Results: The MSCs survived being implanted for 4 weeks in vivo . Neither the alginate-MSC injection nor the coating affected electrode impedance or fibrosis. CI insertion with and without previous alginate injection in normal-hearing animals resulted in increased hearing thresholds within the high-frequency range. Low-frequency hearing loss was additionally observed in the alginate-injected and implanted cochleae, but not in those treated only with a CI. In deafened animals, the alginate-MSC coating of the CI significantly prevented SGN from degeneration, but the injection of alginate-MSCs did not. Conclusion: Brain-derived neurotrophic factor-producing MSCs encapsulated in UHV-alginate prevent SGNs from degeneration in the form of coating on the CI surface, but not in the form of an injection. No increase in fibrosis or impedance was detected. Further research and development aimed at verifying long-term mechanical and biological properties of coated electrodes in vitro and in vivo , in combination with chronic electrical stimulation, is needed before the current concept can be tested in clinical trials.

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Section: Discussionmentioning

confidence: 99%

Stem Cell Based Drug Delivery for Protection of Auditory Neurons in a Guinea Pig Model of Cochlear Implantation

Scheper

Hoffmann

Gepp

et al. 2019

Front. Cell. Neurosci.

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“…This phenomenon was thought to be related to the restoration of neuronal sensitivity to electrical stimulation and/or the interaction between the matrix enveloping the electrodes and the electrical stimulation of the initial switch‐on. During the operation, tiny air bubbles generated by electrode insertion, specifically because of surface tension between endolymph and electrode‐coating material, may have led to higher intraoperative impedance values, which then resolved quickly after implantation . Within several hours after the electrode insertion, a cell cover composed of inflammatory cells, protein adsorption, macrophages and fibroblasts will form around the electrodes, which will lead to increased impedance.…”

Section: Discussionmentioning

confidence: 99%

“…During the operation, tiny air bubbles generated by electrode insertion, specifically because of surface tension between endolymph and electrodecoating material, may have led to higher intraoperative impedance values, which then resolved quickly after implantation. 11 Within several hours after the electrode insertion, a cell cover composed of inflammatory cells, protein adsorption, macrophages and fibroblasts will form around the electrodes, which will lead to increased impedance. When early activation occurs 24 hours after surgery, electrical stimulation causes the formation of a hydride layer, which increases the array surface and triggers cell escape from the surface of the contacts, 12 thereby dramatically decreasing the impedance.…”

Section: Oscillations Of Impedancementioning

confidence: 99%

Feasibility of early activation after cochlear implantation

Sun

Chang

Hsu

et al. 2019

Clinical Otolaryngology

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Objectives The purpose of the study is to investigate feasibility of early activation after cochlear implantation by evaluating long‐term impedance change and speech perception. Design Case‐control study Setting Between July 2015 and December 2016, we prospectively enrolled 20 subjects for early activation (within 24 hours after cochlear implantation). On the other hand, from November 2013 to July 2015, 20 age‐ and sex‐matched control subjects from the database of cochlear implantees treated with conventional activation schedule (4 weeks after surgery) were retrospectively enrolled. Participant Forty patients who underwent cochlear implantation surgeries. Main outcome measures The series impedance and speech perception score of both groups were compared. Results No statistical difference in long‐term follow‐up between the two groups was found using GEEs and multivariate analysis. In the early activation group, impedance reached a steady level by the 2nd postoperative week, and the hearing perception ability significantly improved by the 4th postoperative week. Conclusion This comparative study illustrated sequential impedance data during early activation (24 hours) and conventional activation (4 weeks) after CI surgery. There were no major complications in either group, and the safety of early activation with respect to impedance changes, postoperative residual hearing preservation and speech perception scores were non‐inferior to that of the conventional group. Therefore, in this study, we established the feasibility of early activation 24 hours after cochlear implantation.

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“…They included 2.5–3 cm post-auricular incision wounds, drilling of a bone housing for the receiver-stimulator, harvesting of a cortex bone chip from the mastoid using a minimal mastoidectomy, a posterior tympanostomy, hyaluronic acid gel coverage of the cochleostomy prior to array insertion, utilization of the soft insertion technique and sheltering of any defects of the mastoid cavity with the harvested bone chip after insertion. Full insertion of the electrode array was confirmed in each patient by a postoperative X-ray [1–3]. All speech processors were switched on within 24 hours of the operation.…”

Section: Methodsmentioning

confidence: 99%

Differences in the impedance of cochlear implant devices within 24 hours of their implantation

et al. 2019

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Cochlear implantation is a surgical procedure, which is performed on severely hearing-impaired patients. Impedance field telemetry is commonly used to determine the integrity of the cochlear implant device during and after surgery. At the Department of Otolaryngology, Cheng Hsin General Hospital (Taipei, Taiwan), the cochlear implant devices are switched on within 24 hours of their implantation. In the present study, the impedance changes of Advanced Bionics™ cochlear implant devices were compared with previous studies and other devices. The aim was to confirm previous hypotheses and to explore other potential associated factors that could influence impedance following cochlear implantation. The current study included 12 patients who underwent cochlear implantation at Cheng Hsin General Hospital with Advanced Bionics cochlear implant devices. The cochlear devices were all switched on within 24 hours of their implantation. The impedance was measured and compared across all contact channels of the electrode, both intra-operatively and post-operatively. The intra-operative impedance was compared with the switch-on impedance (within 24 hours of the cochlear implantation); the impedance was notably increased for all contact channels at switch-on. Of the 16 channels examined, 4 channels had a significant increase in impedance between the intra-operative measurement and the switch-on measurement. To the best of our knowledge, the impedance of a cochlear implant device can be affected by the diameter of the electrode, the position of the electrode arrays in the scala tympani, sheath formation and fibrosis surrounding the electrode after implantation and electrical stimulation during or after surgery. When the results of the current study were compared with previous studies, it was found that the impedance changes were opposite to that of Cochlear™ implant devices. This may be explained by the position of the electrode arrays, sheath formation, the blow-out effect and differences in electrical stimulation.

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Evolution of impedance field telemetry after one day of activation in cochlear implant recipients

Cited by 28 publications

References 31 publications

Stem Cell Based Drug Delivery for Protection of Auditory Neurons in a Guinea Pig Model of Cochlear Implantation

Stem Cell Based Drug Delivery for Protection of Auditory Neurons in a Guinea Pig Model of Cochlear Implantation

Feasibility of early activation after cochlear implantation

Differences in the impedance of cochlear implant devices within 24 hours of their implantation

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