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Modelling encapsulation tissue around cochlear implant electrodes
1Department of Electrical, Electronic & Computer Engineering, University of Pretoria, Pretoria, South Africa. tania.hanekom@eng.up.ac.za
Medical & Biological Engineering & Computing
|March 4, 2005
Summary
Electrode encapsulation by scar tissue alters electrical potentials, affecting auditory nerve excitation and threshold currents. These changes depend on factors like tissue thickness and electrode position.
Area of Science:
- Biomedical Engineering
- Neuroscience
- Medical Imaging
Background:
- Fibrous scar tissue encapsulation around implanted electrodes is a common issue in neural prosthetics.
- This encapsulation can impede device efficacy by altering electrical properties.
Purpose of the Study:
- To investigate the impact of fibrous encapsulation on electrical potential distributions.
- To predict changes in auditory nerve fiber excitation patterns and threshold currents due to encapsulation.
Main Methods:
- Utilized a finite element model coupled with an auditory nerve fiber model.
- Simulated the effects of varying encapsulation thickness, perilymph layer, nerve survival, electrode geometry, and array location.
Main Results:
- Encapsulation altered electrical potentials at nerve fibers and electrode contacts, modifying threshold currents and excitation spread.
- Medially located arrays showed higher sensitivity to threshold changes (-0.26 to 2.41 dB) compared to laterally located arrays (-0.64 to 1.5 dB).
- Encapsulation influenced the spread of excitation along the basilar membrane, with variations depending on array location.
Conclusions:
- Electrode encapsulation significantly impacts neural stimulation efficacy.
- Array location and surrounding tissue characteristics are critical factors influencing the effects of encapsulation.