Histopathology of the Temporal Bone Associated with Cochlear Implants

Abstract

We reviewed the histopathologic changes of the temporal bone associated with cochlear implants, based on our own clinical experience and the results of animal and human temporal bone studies conducted to date.
Cochlear implants in animals, especially in guinea pigs were associated with a high degree of trauma and the subsequent foreign body reaction caused largely by the insertion of the electrodes caused unavoidable trauma in the vicinity of the round window and damage to the spiral ligament was especially common. The basilar membrane was also occasionally damaged. Such damage may lead to degeneration and hearing loss by secondary invasion of the spiral ganglion, and should therefore be avoided at all costs.
In the majority of deaf patients the hair cells of the organ of Corti have already disappeared. The afferent nerve components, consisting primarily of the remaining spiral ganglion cells, therefore play an important role. Fortunately, these components were more resistant to the trauma and foreign body reaction than anticipated.