Link between cochlear implant and meningitis exceeds 24 months

March 2006

Children with cochlear implant models with a positioner are at risk of developing bacterial meningitis up to 48 months post-implantation, according to a study by the CDC and FDA.

Krista R. Biernath, MD, of the National Center on Birth Defects and Developmental Disabilities at the CDC, and colleagues studied a cohort of 4,265 children younger than 6 years who received a cochlear implant between Jan. 1, 1997, and Aug. 6, 2002, in the United States to determine if they were at an extended risk of bacterial meningitis post-implantation.

The study examined the same cohort studied in 2002 by Jennita Reefhuis, PhD, et al, which found that children with implants had a higher risk for pneumococcal meningitis at the rate of 138.2 cases per 100,000 person-years up to 24 months post-implantation. Reefhuis and colleagues published their data in 2003 in The New England Journal of Medicine.

More than 11,000 children with hearing loss have a cochlear implant, according to Reefhuis. The internal position of the device is surgically implanted in the cochlea. Some models have a positioner, a small, Silastic wedge that is inserted next to the implanted electrode. Implants with a positioner were available from 1999 to July 2002; the manufacturer, Advanced Bionics in Sylmar, Calif., withdrew these implants from the market voluntarily in July 2002.

“It is still unknown whether the risk of meningitis in patients whose implants have a positioner might be reduced if the implant were removed or replaced by a model that does not have the positioner,” the FDA said in a letter to health care providers last month.

The CDC’s recommendation that children with implants – with or without a positioner, and all potential implant recipients – receive the Haemophilus influenzae type b vaccine and the pneumococcal conjugate (PCV7; Prevnar, Wyeth) vaccine still stands, the FDA said.

A greater risk uncovered

Biernath and colleagues followed the children for two more years. In addition to the original cohort of 4,264 children, they identified one more child who developed meningitis and fit the study criteria, bringing the cohort to 4,265. Of those children, 829 had implants with positioners.

The researchers used cases identified from the FDA Adverse Event Reporting System between Sept. 16, 2002, and Dec. 1, 2004. Information they procured on new cases came from hospital medical records.

Researchers identified 12 new bacterial meningitis episodes for 12 children, of which 11 had implants with positioners. Of the 12, six cases of meningitis occurred 24 months or more post-implantation.

They defined 10 of the 12 cases as definite cases of meningitis, one was probable and one was possible. Streptococcus pneumoniae accounted for nine of the 10 definite cases. Group A streptococcus caused the one case that S. pneumoniae did not cause. Four of the nine children with meningitis caused by S. pneumoniae had a partial record of pneumococcal immunization.

“When cases from the 2002 and 2004 investigation were combined, there was a total of 41 episodes of post-implantation bacterial meningitis among 38 children,” the researchers wrote. “Twenty-seven (71%) of those 38 children had implants with positioners.”

The updated incidence for the 41 cases of bacterial meningitis post-implantation rose to 189 cases per 100,000 person-years, according to the study.

The period between implantation and meningitis was 24 months or greater in eight of the 41 meningitis cases from 1997 to 2004. Seven cases occurred in children who had implants with positioners, according to the study. For children implanted between 1999 and 2002, the incidence rate for children who had implants with positioners was 450 per 100,000 person-years compared with no cases among children without the positioners.

“Although the overall incidence rates of meningitis were similar to those reported in the earlier cohort study, we found that the rate of meningitis decreased as the time after implantation increased,” the researchers wrote. “This decrease may reflect the decreased rate of bacterial meningitis seen in the general U.S. population as children grow older.”

The rate, however, is still higher for children with cochlear implants with positioners than the general pediatric population.

The risk remained higher up to 48 months post implantation for children with the implants with positioners. However, researchers diagnosed no bacterial meningitis cases among the 214 children who received their implants with positioners more than four years prior to Dec. 1, 2004.

“Since our initial cohort study in 2002, many children have received cochlear implants, although none has received the implant model with the positioner,” the researchers wrote. “Our updated findings support continued vigilance for symptoms of meningitis, as well as acute otitis media, by health care providers and parents of all children with cochlear implants.”

What you can do

“These findings underscore the importance of continued monitoring and prompt treatment of bacterial infections in children with cochlear implants beyond two years post-implantation, particularly among children whose implants have a positioner,” the FDA said.

The CDC’s 2003 recommendation to decrease the risk of meningitis in cochlear implant recipients did not change, the FDA said. The agency advises physicians to vaccinate children with cochlear implants and all potential implant recipients., and to try to recognize the early signs of meningitis.

The FDA also recommends prophylactic antibiotics perioperatively in children receiving implants and prompt diagnosis and treatment of middle ear infections.

A portion of a cochlear implant which stimulates auditory nerve fibers to allow the transmission of sound signals to the brain is implanted in the inner ear via a surgical opening or cochleostomy. In some cases, it is postulated that the seal around the implant may not close completely, allowing bacteria to enter the inner ear, near the meninges. However, the exact mechanism by which implants may lead to meningitis is unknown.

For more information:

• Health care providers should report cases of meningitis among cochlear implant recipients. Physicians can call 1-800-FDA-1088 or fax reports to 1-800-FDA-0178. Reports can be mailed to MedWatch, FDA, 5600 Fishers Lane, Rockville, MD 20850-9787. Physicians can also submit reports online at www.fda.gov/medwatch/report.htm.
• Biernath KR, Reefhuis J, Whitney CG, et al. Bacterial meningitis among children with cochlear implants beyond 24 months after implantation. Pediatrics. 2006;117:284-289.
• Whitney CG. Cochlear implants and meningitis in children. Infect Dis J. 2004; 23:767-7678.
• CDC. Pneumococcal vaccination for cochlear implant candidates and recipients: updated recommendations of the Advisory Committee on Immunization Practices. MMWR. 2003;52:739-740.
• Reefhuis J, Honein MA, Whitney CG, et al. Risk of bacterial meningitis in children with cochlear implants. N Engl J Med. 2003;349:435-445.
• Information for health care providers can be found at www.fda.gov/cdrh/cochlear/