Abstract
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.
Highlights
Cochlear implants are devices, which are implanted into the cochlea to aid hearing via stimulation of the cochlear nerve
Previous studies have discussed the possible effects of tissue fibrosis, micro-environmental changes and electrical stimulation on impedance changes, none have investigated Advanced Bionics cochlear implants with initial switch-on within 24 hours of their implantation or made comparisons with other implant devices
The current study identified a significant rise in impedance at 24 hours after surgery, in patients who received Advanced Bionics HiFocus1J cochlear implants
Summary
Cochlear implants are devices, which are implanted into the cochlea to aid hearing via stimulation of the cochlear nerve. The incidence of cochlear implantation has increased throughout the world over the past few decades, and it is considered one of the best medical interventions for patients with severe to profound sensorineural hearing loss. In a previous study by the authors, a significant drop in impedance was found during initial mapping within 24 hours of the cochlear implantation [1]. This finding may have been associated with the spontaneous recovery of the microenvironment inside the cochlea and a divergence effect of electrical stimulation after the device was switched on
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