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Title: Shepherd, R. K., P. Carter, Y. L. Enke, A. Thompson, B. Flynn, E. Trang, A. Dalrymple, and J. B. Fallon. 2020. Chronic intracochlear electrical stimulation at high charge densities: Reducing platinum dissolution
Authors: Shepherd, Robert
Carter, Paul
Enke, Ya Lang
Thompson, Alex
Flynn, Brianna
Trang, Ella
Dalrymple, Ashley
Fallon, James
Keywords: Electrical stimulation
Neural prosthesis
Platinum electrode
Stimulation safety
Corrosion
Tissue response
Issue Date: Sep-2020
Publisher: IOP Publishing
Citation: Shepherd, R. K., P. Carter, Y. L. Enke, A. Thompson, B. Flynn, E. Trang, A. Dalrymple, and J. B. Fallon. 2020. Chronic intracochlear electrical stimulation at high charge densities: Reducing platinum dissolution. Journal of Neural Engineering. 17: 056009.
Abstract: OBJECTIVE: Cochleae of long-term cochlear implant users have shown evidence of particulate platinum (Pt) corroded from the surface of Pt electrodes. The pathophysiological effect of Pt within the cochlea has not been extensively investigated. We previously evaluated the effects of Pt corrosion at high charge densities and reported negligible pathophysiological impact. The present study extends this work by examining techniques that may reduce Pt corrosion. APPROACH: Deafened guinea pigs were continuously stimulated for 28 days using biphasic current pulses at extreme charge densities using: (i) electrode shorting; (ii) electrode shorting with capacitive coupling (CC); or (iii) electrode shorting with alternating leading phase (AP). On completion of stimulation, cochleae were examined for corrosion product, tissue response, auditory nerve (AN) survival and trace levels of Pt; and electrodes examined for surface corrosion. MAIN RESULTS: Pt corrosion was evident at > 200 μC/cm2/phase; the amount dependent on charge density (p < 0.01) and charge recovery technique (p < 0.01); reduced corrosion was apparent using CC. Tissue response increased with charge density (p < 0.007); cochleae stimulated at > 200 μC/cm2/phase exhibited a vigorous response including a focal region of necrosis and macrophages. Notably, tissue response was not dependent on the charge recovery technique (p = 0.56). Despite stimulation at high charge densities resulting in significant levels of Pt corrosion, there was no stimulus induced loss of ANs. SIGNIFICANCE: Significant increases in tissue response and Pt corrosion were observed following stimulation at high charge densities. Charge recovery using CC, and to a lesser extent AP, reduced the amount of Pt corrosion but not the tissue response. Stimulation at change densities an order of magnitude higher than those used when programming cochlear implant recipients in the clinic, produced a vigorous tissue response and corrosion products without evidence of neural loss.
URI: http://repository.bionicsinstitute.org:8080/handle/123456789/410
ISSN: 1741-2552
Appears in Collections:Bionic Hearing Research Publications

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