An Instrumented Cochlea Model for the Evaluation of Cochlear Implant Electrical Stimulus Spread

Abstract

Cochlear implants use electrical stimulation of the auditory nerve to restore the sensation of hearing to deaf people. Unfortunately, the stimulation current spreads extensively within the cochlea, resulting in "blurring" of the signal, and hearing that is far from normal. Current spread can be indirectly measured using the implant electrodes for both stimulating and sensing, but this provides incomplete information near the stimulating electrode due to electrode-electrolyte interface effects. Here, we present a 3D-printed "unwrapped" physical cochlea model with integrated sensing wires. We integrate resistors into the walls of the model to simulate current spread through the cochlear bony wall, and "tune" these resistances by calibration with an in-vivo electrical measurement from a cochlear implant patient. We then use this model to compare electrical current spread under different stimulation modes including monopolar, bipolar and tripolar configurations. Importantly, a trade-off is observed between stimulation amplitude and current focusing among different stimulation modes. By combining different stimulation modes and changing intracochlear current sinking configurations in the model, we explore this trade-off between stimulation amplitude and focusing further. These results will inform clinical strategies for use in delivering speech signals to cochlear implant patients.

Management of Severe Facial Nerve Cross Stimulation by Cochlear Implant Replacement to Change Pulse Shape and Grounding Configuration: A Case-series

“…FNS can also be influenced by the current path from stimulating to ground electrode. Most devices use monopolar stimulation, resulting in wide electric fields (21,22). In contrast, intra-cochlear current return paths, such as bipolar or tripolar stimulation, have smaller spatial electric fields but at the expense of less stimulation at the AN (22).…”

Detecting and managing partial shorts in Cochlear implants: A validation of scalp surface potential testing

“…The near‐field voltage (μV) to each electrode contact was measured within a 3D printed linear cochlea model set‐up as developed by Jiang et al 13 The explanted CI was placed within a 3D printed linear cochlea with 14 copper wires connected in parallel to ground via 47 kΩ resistors (Figure 1B ). Sequentially, each electrode was aligned against one measurement wire to record the near‐field peak‐to‐peak voltage when stimulated at 412 cu with 70 μs pulse width stimulus levels (3.5 times higher than the levels used for scalp measures to overcome the electrical noise from the artificial cochlea) using a Picoscope 2203 2‐channel oscilloscope controlled by Picoscope 6.14 software.…”

3D printed biomimetic cochleae and machine learning co-modelling provides clinical informatics for cochlear implant patients

“…All EFI (or transimpedance matrix) measurements of the 3D printed models were obtained using either an Advanced received, but this does not affect the measurements of other electrodes and the general shape of the EFI profile. For all the data presentations, the on-stimulation EFI data (contact impedance) were not compared, due to the fact that on-stimulation EFI data is dominated by the electrode interface resistance 7,46 and do not inherently reflect the electroanatomical characteristics of human cochleae (or the 3D printed biomimetic cochleae); and onstimulation EFI data varies over time 47 and among different CIs.…”