What is the initial information regarding cochlear implants and meningitis?

Recently, the Food and Drug Administration's Center for Devices and Radiological Health reported that they were now aware of 52 cases of meningitis in patients that had undergone cochlear implants. These cases were recorded over a 14 year period (worldwide) and included both adult as well as pediatric patients (ages ranging from 21 months to 72 years). The cases of meningitis also developed at varying times following cochlear implant surgery (ranging from less than 24 hours after surgery to more than 5 years after surgery).

It is important to remember early on in this discussion that worldwide, more than 60,000 patients have undergone cochlear implantation. And although meningitis is a very significant health risk, 52 cases out of more than 60,000 implants projects far less than a 1% risk of contracting meningitis. It still remains to be determined if this risk is any higher than the risk for the general population for contracting meningitis (the risk of otherwise healthy persons -who do not have a cochlear implant - contracting meningitis is also far less than 1%).

What is Meningitis?

Meningitis is a very serious and potentially life-threatening infection of the lining and fluid cerebrospinal fluid that surrounds the brain and spinal cord. Infections of this nature can be bacterial or viral. Among the cases of meningitis following cochlear implantation, cultures of this cerebrospinal fluid were available in 14 cases. Amongst these 14 cases, the most common bacteria cultured was Streptococcus pneumoniae (also commonly referred to as pneumococcus). Rare bacteria also identified by these cultures included Haemophilus influenza, Escherichia coli, Streptococcus viridans and enterococcus. In cases of acute bacterial meningitis, prompt identification of the infection and early aggressive treatment with intravenous (iv) antibiotics are necessary to give the patient the best chances for full recovery.

Early signs of meningitis can include fever, lethargy, irritability or change in mental status (sluggishly responsive, loss of consciousness, etc). Patients can also show signs of photophobia (sensitivity to light), a stiff neck, nausea and vomiting. Immediate consultation with a physician followed by evaluation in an emergency department is often an efficient method of action if you suspect early meningitis. After an initial evaluation and stabilization of the patient, further workup may typically include bloodwork, possibly a CT scan of the brain and a lumbar puncture ("spinal tap") to obtain a sample of cerebrospinal fluid for analysis and culture.

As is the case in any life-threatening, severe medical problem, the safer course of action is to contact your physician as soon as you suspect a problem.

Why would a cochlear implant cause someone to develop meningitis?

None of the initial or follow up reports have shown a specific mechanism by which a cochlear implant could either cause a patient to develop meningitis or even cause a patient to be at higher risk for meningitis simply because they have a cochlear implant. However, several concepts have been proposed as possible factors. These unproven theories are presented here so that you are at least aware of the ideas being considered.

Abnormal inner ear anatomy

One of the more common abnormalities found in patients that are severely to profoundly hearing impaired (i.e. those patients that are candidates for cochlear implants) is an abnormal anatomy of the inner ear.
Specifically, the inner ear and cochlear cavities are frequently dilated or poorly developed. In these instances, it would not be unusual for a patient to have a dilated channel or communication of the inner ear compartment with the cerebrospinal fluid space (the fluid infected in cases of meningitis). In such cases, it has been speculated that this abnormality allows bacteria to enter through the cochlea and then pass through an abnormal communication or channel into the spinal fluid space where meningitis can develop.

In such a theory, it may not be the cochlear implant itself that is causing a higher risk of meningitis, but the anatomical abnormality of the inner ear that places the patient at risk for meningitis. If this were the case, then it would be reasonable to expect that those patients who have severe to profound hearing losses but did not opt for a cochlear implant, would have the same risk of meningitis as those patients who did choose to undergo cochlear implantation. However, data on this population of patients is not available or easily obtainable. Research efforts are underway to try and collect this type of data which would help shed light on this aspect of meningitis.

A prior history of meningitis

The medical literature is fairly clear in showing that patients (especially children) that have a history of losing their hearing because of meningitis have a greater chance of developing more episodes of meningitis compared to the general population.
As a result, a certain population of patients that are cochlear implant candidates because they lost their hearing from meningitis, are already at higher risk for recurrent meningitis regardless of whether they underwent cochlear implantation or not.

The cochlear implant as a foreign body in infections

In a wide variety of medical and surgical experiences, foreign materials implanted into the human body have been shown to slightly increase the risk of infection and complications. To a large extent, many of these problems have been overcome by the development of more biocompatible materials. However, it is still feasible to consider that a cochlear implant (being a foreign body) might become colonized with bacteria and serve as a seed for infection problems. The overwhelming experience with implants being well-tolerated by the body and not showing signs of "rejection" or wound infections makes this factor less likely to be critical.

Ear infections in an ear with a cochlear implant

In the pediatric population (less than 5 years of age), ear infections are a very common occurrence. Middle ear infections or otitis media remain one of the most common illnesses suffered by children in the United States with close to 2/3rds of all children developing at least one episode of otitis media before they reach the age of 2 years. Children with a cochlear implant are just as susceptible to "routine" ear infections as other children in the general population.
Concerns arose early on in the use of cochlear implants in children because the cochlear implant is inserted through the middle ear space and a portion of the device rests in the middle ear and mastoid compartment. These spaces are where ear infections occur.
Early concerns were focused on whether an episode of otitis media in an ear with an implant would then allow bacteria to enter the cochlea and then possibly result in meningitis. The worldwide experience in children seems to dispute this theory. Current trends are to treat middle ear infections in children with a cochlear implant as aggressively as you would treat ear infections in children without a cochlear implant. Antibiotics for occasional acute otitis media episodes are largely managed by pediatricians and family practitioners with oral antibiotics +/- antibiotic ear drops. If the episodes become frequent or chronic, then inserting pressure equalizing tube(s) in the eardrum(s) can routinely be performed whether the ear has a cochlear implant or not.

Surgical technique during cochlear implant surgery

Since the surgical procedure of cochlear implantation is still a relatively invasive procedure, it is necessary for surgeons to consider if the surgical technique itself is a factor in developing meningitis.
One of the specific techniques that has become standard for most cochlear implant surgeons is to carefully seal the opening made in the cochlea that allows insertion of the electrode array. In most instances, surgeons use small pieces of the patients' own tissue (muscle or fascia from the incision edges) to pack around and seal off the 1-2 mm cochleostomy (opening created in the cochlear wall). Failure to do this would potentially allow fluid to leak out of the cochlea as well as allow contamination of the inner ear compartment with bacteria from the middle ear space.
Another specific technical aspect is drilling of the bed for the implant's internal processor. Especially in young children, the bone of the skull is often removed down to the dura (the protective covering of the brain and spinal cord which contains the spinal fluid). Removing this bone allows the implant to be recessed so that it is not so prominent under the skin of child's scalp. Care is taken not to violate the dura during this step so that the spinal fluid space is not exposed and placed at higher risk for infection.
Surgeons have developed their own methodologies and techniques for each aspect of cochlear implant surgery and discussion with your surgeon of specific risks and techniques is necessary to better understand these issues.

Other factors predisposing a person to meningitis

In general, patients that develop meningitis may do so for a variety of reasons. It is necessary to consider and rule out the possibility that a patient may have an underlying immunodeficiency - weakness or defect of their immune system to fight off routine infections.

Should my child get vaccinated for meningitis?

We feel that vaccinating children with cochlear implants against Streptococcus pneumoniae and Haemophilus influenzae infections is worthwhile. Even though the risks of meningitis in implanted patients remains extremely low, and it remains to be seen whether or not the implants themselves are causing any of these reported cases of meningitis, the consequences of developing meningitis are particularly severe. It is also noteworthy that the vaccines against pneumococcus and H.influenzae have proven to be very safe with a low incidence of any significant side effects. Taken together, our risk-benefit analysis favors recommending that our patients receive the vaccines for pneumoccocus and H. influenzae.

We should also note that both of these vaccines are already recommended by the Advisory Committeee on Immunization Practices (ACIP) for the pediatric population in general (whether or not a child has a cochlear implant). Specifically,

1. Haemophilus influenza vaccines are recommended by the ACIP for all children up to age 5 years.
2. Heptavalent pneumococcal vaccines (Prevnar) is indicated for use in infants and toddlers, and is recommended by the ACIP for all children less than age 2 years, and for children up to age 5 years who are at high risk of invasive pneumococcal infections.
3. The 23-valent pneumococcal polysaccharide vaccines (Pnu-Imune 23 and Pneumovax 23) are recommended for children over age 2 years, adolescents, and adults who are at high risk of invasive pneumococcal disease.
4. For children age 2 years to 5 years of age who are at high risk of invasive pneumococcal infections, ACIP recommends use of pneumococcal conjugate vaccine followed at least 2 months later by 23-valent pneumococcal polysaccharide vaccine in order to provide protection against a broader range of serotypes.

Additional information regarding immunizations can be obtained at the National Vaccine Program Office of the Centers for Disease Control and Prevention .

What should you do at this point?

If your child is a cochlear implant user and has not been vaccinated or if you are uncertain whether your child has received any of the recommended vaccinations, we strongly encourage you to contact your primary care physician (pediatrician, family practitioner, etc) to discuss the risks and benefits of obtaining the vaccination(s) in your particular case. For our patients that have been implanted at the Center for Hearing and Deafness Research here at Cincinnati Childrens', we have mailed information both to the patients and families, as well as their primary care physicians regarding this topic.

We are also available to our patients to discuss further questions that may arise regarding cochlear implants and the risks of meningitis.
If for whatever reason you are unable to see your primary care physician, we would be more than willing to help coordinate care and vaccinations. Please refer to the contact link for information on contacting

Other sites that may provide you with implant-specific information

Cochlear Corporation
Clarion / Advanced Bionics
Medel Corporation

If you would like a copy the FDA article "Cochlear Implant Recipients may be at Greater Risk for Meningitis" please click here. [requires acrobat reader ] .

©2005 Center for Hearing and Deafness Research