Molecular and Cellular Mechanisms of Loss of Residual Hearing after Cochlear Implantation

Objectives:We describe the various molecular and cellular pathways that lead to early and delayed loss of residual hearing after cochlear implantation.Methods:We performed a systematic review using the Medline database with the key words cochlear implant, residual hearing, inflammation, apoptosis, and necrosis.Results:The mechanisms underlying the loss of residual hearing after cochlear implantation are multiple. Early hearing loss may be provoked by the surgical access to the inner ear spaces and by trauma caused by insertion of the electrode array. After the initial trauma, an acute inflammatory response promotes elevated levels of cytokines and reactive oxygen species, which in turn promote sensory cell loss by apoptosis, necrosis, and necrosis-like programmed cell death. Treatments that counteract such an inflammatory reaction, production of reactive oxygen species, and apoptosis are effective at preventing hair cell degeneration. However, delayed hearing loss appears to be a consequence of chronic in...