Misplaced cochlear implants raise meningitis risk

From: Scientific American - Apr 4, 2007

By Martha Kerr

NEW YORK (Reuters Health) - Findings from a study conducted in rats suggest that cochlear implants, which are used to treat severe hearing loss, can cause meningitis -- inflammation of the membrane surrounding the brain -- if they are not placed properly during surgery.

The improper insertion of a cochlear implant causes inner ear trauma that increases the risk of meningitis in rats for at least one month after the procedure, Australian researchers report. However, avoiding inner ear damage during insertion can virtually eliminate the risk of infection.

Dr. Benjamin P. C. Wei and colleagues at the Bionic Ear Institute of the Royal Victorian Eye and Ear Hospital at the University of Melbourne, examined the risk of meningitis in rats that experienced inner ear trauma during placement of a cochlear implant and rats that did not sustain inner ear trauma.

After cochlear implant placement, the animals were injected with Streptococcus pneumoniae, bacteria that can cause meningitis, to see if an infection would develop.
Wei and colleagues report in the Archives of Otolaryngology, Head and Neck Surgery that inner ear trauma during implant placement significantly increased the risk of meningitis. The investigators observed that the risk remained high for at least four weeks following surgery.

By contrast, cochlear implant insertion without inner ear trauma did not raise the risk of meningitis.

"Surgical insertion technique is very important to prevent inner ear trauma" during cochlear implant insertion, Wei told Reuters Health. He added that antibiotics should be given to patients before they undergo cochlear implantation to prevent meningitis and related infections. This is especially important in children who are prone to middle ear infection.

SOURCE: Archives of Otolaryngology, Head and Neck Surgery, March 2007.

© 2007 Scientific American, Inc.