Evaluation of the current distribution of the hybrid common ground stimulation in cochlear implants
Résumé
Background
In cochlear implants, the hybrid common ground is a combination of a classic monopolar
stimulation with a standard common ground. This new stimulation montage allows the current to
return from both the non-stimulating electrodes on the electrode array and the reference electrode
placed between the skull and scalp. In theory, this lead to reach a compromise between the current
focality and the efficiency of the stimulation. Even if this stimulation type has already been adopted
by some implant manufacturers, the 3D geometry of its current pathways remains to be studied.
Methods
The study is two-fold. First, an in-vitro experiment aimed to measure the electrical field produced
by the hybrid common ground stimulation. An electrode array of an XP implant (Oticon Medical,
Neurelec) was placed in saline solution and the electrical field was recorded by a probe that moves
along the programmed grid. During the stimulation, the current waveforms on all the grounding
electrodes were also recorded. Second, an in-situ measurement was conducted. Another XP device
was implanted into a human specimen. The same procedure as in the in-vitro measurement was
performed to record, this time, the current waveforms only.
Results
The recorded two groups of current data were compared with each other to investigate how the
current path is modified by the geometry of a human cochlea. The potential distribution measured
during the in-vitro experiment was also compared with other stimulation types such as monopolar.
The energy consumption of the stimulation was also computed from the collected data.
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