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The U.S. Food and Drug Administration (FDA) is warning that children with an early version of a cochlear implant face an increased risk of bacterial meningitis beyond the first two years following implantation of the hearing devices.
The increased risk means young implant patients should be monitored as long as the electronic devices are in place for signs of the sometimes fatal infection of the fluid surrounding the brain and spinal cord.
Children who are deaf who have the cochlear implant electrode design which includes a silastic wedge positioner contract bacterial meningitis more often than either children with the implants that don't have the wedge or those without implants at all, the FDA said in separate letters to patients and doctors.
Originally, doctors used the silastic wedge to help position the electrode close to the auditory nerve. Advanced Bionics Corp. was the only manufacturer to sell implants with the positioner. None has been implanted since July 2002.
An original study found 26 of 4,264 children with the implants developed meningitis during the first two years following surgery. Children with the positioner were at greater risk. A new study that followed the same children for an additional two years found another six - all with positioners - developed meningitis. The results appear in this month's issue of the journal Pediatrics.
The study highlights that there is a small, but lingering risk with all implantable technologies, said John Niparko, an otolaryngologist and director of the cochlear implant center at Johns Hopkins Medical Institution in Baltimore, MD. Certain features of this particular electrode design may have heightened this risk.
"Any procedure that is in proximity to the lining of the brain, especially one that introduces a prosthetic device that will sit near the brain, heightens the risk of an infection that can be 'translocated' into the brain cavity," he said. "The mechanism is based on the formation of new blood vessels around the device. Such nascent blood vessels are leaky, and can act as a conduit in transporting bacteria across the lining of the brain, with resultant meningitis."
Elderly adults too may be at slightly elevated risk, although reports of this have not appeared, Niparko said. Older adults are able to report upper respiratory infections and receive treatment, and this may protect them from developing meningitis. More importantly, the anatomy of the fully formed skull is such that older adults do not carry the same level of risk of the potential problems that children face, he said.
The FDA does not have enough information to recommend surgically removing the devices, given the risk of postoperative infection. Beyond monitoring cochlear implant patients for signs of meningitis, which include high fever and a stiff neck, the FDA recommends that children receive the proper vaccinations.
The ASHA Leader has previously reported about the link between meningitis and cochlear implants. Visit the ASHA Web site at www.asha.org and type "meningitis and cochlear implants" in the search bar at the top of the page.
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