Hearing Loss in Meningitis

Hearing loss is one of the most common complications of bacterial meningitis. Hearing loss can be temporary or permanent.

Diagnosing and treating meningitis quickly, ideally within a day or two of the appearance of symptoms, can greatly lower the risk of hearing loss. In the event hearing loss is severe or permanent, it can be managed with hearing aids, cochlear implants, and ongoing support from hearing specialists and therapists.

Causes and Risk Factors

Meningitis is inflammation of the protective membranes of the brain and spinal cord called the meninges. It usually results from an infection, but in rare cases is associated with a non-infectious cause such as brain surgery or lupus.

Hearing loss is almost always associated with bacterial meningitis. Streptococcus pneumoniae and Neisseria meningitidis are common causes of bacterial meningitis, Other bacteria, such as Haemophilus inflenzae, have also been studied in their association with menigitis-related hearing loss.

In children in high-income countries, hearing loss is seen in 14 to 32% of cases of pneumococcal meningitis and 4% of cases of meningococcal meningitis.

Other factors that increase the risk of hearing loss caused by meningitis include:

• Young age: Children under 12 months at at the greatest risk for hearing loss.
• Severity of symptoms: A 2018 study in the Pakistan Journal of Medical Science reported that the vast majority of children with meningitis-associated hearing loss had severe symptoms, including high fever, vomiting, and seizures. The bulging of the fontanelle ("soft spot") in infants is also a red flag.
• Delayed treatment: The same study found that children who received treatment two to five days after the appearance of symptoms were more than three times as likely to experience hearing loss as those who were treated within less than two days.
• Certain substances in cerebrospinal fluid: Examination of cerebrospinal fluid (CSF) extracted during a lumbar puncture can help predict the likelihood of meningitis-associated hearing loss. Low glucose levels and high protein levels in CSF are linked to an increased risk of hearing loss. Blood tests are less useful.

Pathology

With meningitis, bacteria, cytokines (inflammatory compounds produced by the immune system), and bacteria toxins triggered by antibiotics can infiltrate the inner ear, damaging nerve fibers and specialized cells in the cochlea known as hair cells.

There are both inner and outer hair cells. Outer hair cells amplify low-level sounds. Inner hair cells transform sound vibrations into electrical signals that are relayed to the brain. Damage to these cells decreases hearing sensitivity, and, because the inner ear hair cells cannot regenerate, the damage is usually permanent.

Bacterial meningitis can also cause septicemia ("blood poisoning"), a condition that can trigger apoptosis (cell death) in the inner ear and/or auditory nerve. Hearing loss involving these organs is known as sensorineural hearing loss and is almost always permanent. Babies are especially at risk, because the organs of their ears are still developing.

In the weeks and months after hearing loss occurs as a result of meningitis, there is also a risk of cochlear ossification, a complication in which extreme inflammation causes fluid in the cochlea to be replaced by bone. This can make hearing loss worse and treatment more difficult.

Not all hearing impairment is permanent. Some children experience a dulling of sound—as if the ears are stuffed with cotton—caused by a condition called glue ear, in which the middle ear fills with a viscous fluid. It usually resolves without treatment, although in some cases ventilation tubes are necessary to help drain the ear.

Older children or adults may develop a persistent ringing in the ear called tinnitus thought to be caused by damage to the auditory nerve, resulting in ongoing and abnormal electrical signals to the brain.

Diagnosis

If hearing is impaired during or immediately following a bout of meningitis, a healthcare provider can use a lighted scope (called an otoscope) to check for fluid that would indicate glue ear in one or both ears.

If glue ear is not the diagnosis and hearing loss is severe, persistent, or worsens, a hearing specialist, called an audiologist, can perform a battery of tests to determine the extent of hearing loss.

Audiologist Procedures

Behavioral tests are intended for babies and younger children, but they can also be used for older children with significant hearing loss.

• Behavioral observation audiometry (BOA): The healthcare provider will observe how a baby (0 to 5 months of age) responds to sounds.
• Visual reinforcement audiometry (VRA): The healthcare provider will observe how a child (6 months to 2 years of age) physically moves or turns in response to sounds.
• Conditioned play audiometry (CPA): A child (2 to 4 years of age) is asked to locate a sound or wait until they hear a sound before performing a play task, such as honking a horn.
• Conventional audiometry: Children 5 years and over are asked to respond to sounds by nodding, pointing, or responding verbally.

Auditory function tests involve devices that measure hearing sensitivity and how well organs of the ears are functioning.

• Pure-tone testing: The person being tested is asked to respond to sound transmitted to the ear via earphones.
• Bone conduction testing: The person being tested must respond to sounds transmitted to the ear via a vibrating device placed behind the ear.
• Tympanometry: A probe measures movements of the eardrum when exposed to bursts of air pressure.
• Otoacoustic emissions (OAE): Sounds are transmitted into the ear via a small earphone to see how much is reflected back.
• Acoustic reflex measures: An ear probe measures how much the middle ear tightens in response to a loud sound.
• Auditory brainstem response (ABR): Probes positioned on the head measure brain wave activity in response to sound.

Imaging tests such as magnetic resonance imaging or computed tomography may also be performed if cochlear ossification is suspected.

Testing Recommendations

Infants and children with meningitis should have a hearing test at the time of discharge from the hospital or shortly thereafter.

Even though teens and adults are more likely to notice a diminishment in the ability to hear, testing soon after developing meningitis is advised to detect damage to the ear. Follow-up testing may be recommended to see if there is any improvement or deterioration.

Treatment

Most hearing loss can be managed with some type of hearing aid. Options include traditional in-the-ear or behind-the-ear devices as well as frequency-modulated hearing systems (comprised of a transmitter and wireless receiver in a set of headphones or earphones).

If sensorineural hearing loss is severe enough to undermine quality of life or the ability to function normally, a cochlear implant may be considered. Not everyone is a candidate.

A cochlear implant is generally indicated for children who have sensorineural hearing loss in both ears who have not been helped enough by wearing a hearing aid for six months. Implants are indicated for adults who have sensorineural hearing loss in both ears and are able to hear only hear 50% of words with a hearing aid.

Other supportive options include speech and language therapy and auditory-verbal therapy, in which deaf persons learn to speak and listen with the hearing they have, often with the aid of hearing devices.

Prevention

Vaccines are available to prevent some of the most common causes of bacterial meningitis.

Hib (Haemophilus influenzae type B) vaccine should be given to all children younger than 5 years old.

Pneumococal vaccine should be given to children under 5, people aged 5 to 64 with certain risk factors, and people over 65 who haven't received the vaccine previously.

All 11- to 12-year-olds should get a single dose of the meningococcal conjugate (MenACWY) vaccine along with a booster shot at 16. Teens and young adults 16 through 23 may also get the serogroup B meningococcal (MenB) vaccine. These vaccines are between 85% and 100% effective.

A third meningococcal vaccine (MenABCWY), which contains components of a MenACWY vaccine and a MenB vaccine, is also available. It is only recommended as an option for anyone who would otherwise be receiving both the MenACWY and MenB vaccines during the same visit.

When to See a Healthcare Provider

Hearing loss may not be immediately obvious after meningitis, so it's important to be on the lookout for signs of impairment, especially in smaller children and babies. Signs of hearing impairment include the following:

• The baby may not be startled by sudden loud noises.
• Older infants, who should respond to familiar voices, show no reaction when spoken to.
• A young child may appear to favor one ear when spoken to, turning the "good" ear toward a sound they want to hear.
• Children should be using single words by 15 months and simple two-word sentences by 2 years. If they do not reach these milestones, hearing loss may be the cause.

Meningitis Healthcare Provider Discussion Guide

Get our printable guide for your next healthcare provider's appointment to help you ask the right questions.

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