Pathological changes of temporal bone after cochlear implantation and the countermeasures

Abstract

Cochlear implant (CI) is an artificial electronic device which can provide a sense of sound to a patient with severe or profound hearing loss. Pathological changes have been observed after CI surgery, which might influence the effectiveness of the CI procedure. In this review, we divided the postoperative pathological changes of the temporal bone into two categories according to different stages: immediate trauma and delayed side effects. Immediate trauma might arise from traumatic insertion of the electrode during CI surgery, which included trauma at cochleostomy site, lateral wall trauma, basilar membrane injury, osseous lamina fracture and modiolar injury. Delayed side effects arised from the host response against the inserted electrode, which involved a tissue reaction consisting of fibrotic and osseous changes in the cochlea, intracochlear inflammatory response to the electrode, changes in spiral ganglion cells number, pathological changes outside the cochlea and pathological changes after reimplantation. Published data suggested that the effectiveness of the surgery would be affected in many ways by postoperative pathological changes, and individuals with these changes would have an increased risk of the surgical failure. Therefore, subsequent countermeasures need to be taken to reduce the damages.