Pneumococcal meningitis post-cochlear implantation: potential routes of infection and pathophysiology.

OBJECTIVE This review describes the current concept of pneumococcal meningitis in cochlear implant recipients based on recent laboratory studies. It examines possible routes of Streptococcus pneumoniae infection to the meninges in cochlear implant recipients. It also provides insights into fundamental questions concerning the pathophysiology of pneumococcal meningitis in implant recipients. DATA SOURCES Medline/PubMed database; English articles after 1960. Search terms: cochlear implants, meningitis, pneumococcus, streptococcus pneumonia. REVIEW METHODS Narrative review. All articles relating to post-implant meningitis without any restriction in study designs were assessed and information extracted. RESULTS The incidence of pneumococcal meningitis in cochlear implant recipients is greater than that of an age-matched cohort in the general population. Based on the current clinical literature, it is difficult to determine whether cochlear implantation per se increases the risk of meningitis in subjects with no existing risk factors for acquiring the disease. As this question cannot be answered in humans, the study of implant-related infection must involve the use of laboratory animals in order for the research findings to be applicable to a clinical situation. The laboratory research demonstrated the routes of infection and the effects of the cochlear implant in lowering the threshold for pneumococcal meningitis. CONCLUSION The laboratory data complement the existing clinical data on the risk of pneumococcal meningitis post-cochlear implantation.