title: Molecular and cellular mechanisms of loss of residual hearing after cochlear implantation.
abstract: OBJECTIVE
  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 inflammation with development of fibrotic tissue. The mechanisms that lead to fibrosis are poorly understood, and standard antiinflammatory drugs are insufficient for preventing its development.
  
  
  CONCLUSIONS
  Cochlear implantation is followed by an inflammatory response involving several pathways that lead to either short-term or long-term sensory hair cell degeneration. Future studies should focus on revealing the precise molecular mechanisms induced by cochlear implantation to allow the discovery of new targets for the effective prevention and treatment of loss of residual hearing.
authors.affiliation: INSERM, Institute for Neurosciences of Montpellier, University Montpellier I, Montpellier, France.
authors.forename: Huan
authors.initials: H
authors.lastname: Jia
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.forename: Florence
authors.initials: F
authors.lastname: François
authors.forename: Alain
authors.initials: A
authors.lastname: Uziel
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Puel
authors.forename: Frédéric
authors.initials: F
authors.lastname: Venail
mesh_terms: D017209:Apoptosis; D001301:Audiometry, Pure-Tone; D001309:Auditory Threshold / Q000502:physiology; D003054:Cochlear Implants; D006309:Hearing; D034381:Hearing Loss / Q000378:metabolism / Q000473:pathology / Q000601:surgery; D006801:Humans