Impedance changes in chronically implanted and stimulated cochlear implant electrodes. (July 2014)

• Record Type: Journal Article
• Authors: Newbold, Carrie; Mergen, Silvana; Richardson, Rachael; Seligman, Peter; Millard, Rodney; Cowan, Robert; Shepherd, Robert
• Is Part Of: Cochlear implants international. Volume 15:Number 4(2014)
• Page Start: 191
• Page End: 199
• Publication Date: 2014-07
• Subjects: Cochlear implants -- Periodicals; 617.882
• DOI: 10.1179/1754762813Y.0000000050
• Languages: English
• ISSNs: 1467-0100

Abstract

<abstract> <title> <x content-type="archive" xml:space="preserve">Abstract</x> </title> <sec> <title>Objectives</title> <p>Electrode impedance increases following implantation and undergoes transitory reduction with onset of electrical stimulation. The studies in this paper measured the changes in access resistance and polarization impedance <italic>in vivo</italic> before and following electrical stimulation, and recorded the time course of these changes.</p> </sec> <sec> <title>Design</title> <p>Impedance measures recorded in (a) four cats following 6 months of cochlear implant use, and (b) three cochlear implant recipients with 1.5–5 years cochlear implant experience.</p> </sec> <sec> <title>Results</title> <p>Both the experimental and clinical data exhibited a reduction in electrode impedance, 20 and 5% respectively, within 15–30 minutes of stimulation onset. The majority of these changes occurred through reduction in polarization impedance. Cessation of stimulation was followed by an equivalent rise in impedance measures within 6–12 hours.</p> </sec> <sec> <title>Conclusions</title> <p>Stimulus-induced reductions in impedance exhibit a rapid onset and are evident in both chronic <italic>in vivo</italic> models tested, even several years after implantation. Given the impedance changes were dominated by the polarization component, these findings suggest that the electrical stimulation altered the electrode surface rather than the bulk tissue and fluid in the cochlea.</p> </sec> </abstract>