Figure 1

Illustrations of cochlear implant surgeries with/without trauma to the lateral wall and how the presence of blood cells effects impedance. (A–C) Illustration of a cochlear implant where lateral wall trauma did not occur. (A) Illustration of how four-point impedance is inferred using a cochlear implant. The current is supplied to the outer electrodes in the quartet and the voltage is measured between the two inner electrodes. This is repeated along the whole array, resulting in 19 quartets. (B) Insertion completed with the cochlea filled with perilymph. C) The current paths of the stimulus for a four-point impedance measurement through perilymph. The current has little resistance and therefore the voltage is low. (D–F) Illustration of a cochlear implant where lateral trauma occurred, resulting in the infiltration of blood. (D) Insertion of the cochlear implant where the electrode array comes into contact with the lateral wall and causes damage. (E) Cochlear implant completely inserted with blood pushed into the cochlea along the electrode array. (F) The current paths for the stimulus when blood is present in between the two inner electrodes. The current has more resistance since it does not pass through the cells and the reduction in available ions, resulting in a higher voltage.