Section: New Results

Modeling electrical stimulation

Cochlear implants

Participants : Kai Dang, Maureen Clerc, Pierre Stahl [Oticon Medical] , Dan Gnansia [Oticon Medical] , Clair Vandersteen [Nice University Hospital] , Nicolas Guevara [Nice University Hospital] .

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. 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. 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.

This work has been published in [58]. We thank the GRAPHDECO project-team for lending us THE 3D printer which was used in the in-vitro experiment.