Hearing Loss in Meningitis

Why It Happens and How to Treat or Prevent It

A baby getting his ears checked by a doctor
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In This Article

One of the lesser-known consequences of meningitis is hearing loss. It is a condition that may affect as many as 50% of people diagnosed with bacterial meningitis, albeit to varying degrees. The risk of hearing loss is greatest in children under two, in part because they are more likely to experience neurological damage compared to older children or adults.

Hearing loss can occur within four weeks of a bout of bacterial meningitis in some people and up to eight months in others. Once hearing loss occurs, it tends to improve little over time.

By diagnosing and treating meningitis quickly, ideally within a day or two of the first appearance of symptoms, the risk of hearing loss may be greatly reduced. If permanent impairment occurs, treatment may involve hearing aids, cochlear implants, and ongoing support from hearing specialists and therapists.

Causes and Risk Factors

Meningitis is the inflammation of the protective membranes of the brain and spinal cord called the meninges. It is most commonly caused by a bacteria or virus but is sometimes be the result of a fungal or parasitic infection or a non-infectious cause like brain surgery or lupus.

There are certain factors that can increase the risk of meningitis-associated hearing loss:

  • Bacterial Meningitis: Hearing loss is almost always associated with bacterial meningitis. According to a 2010 review in Pediatrics, hearing loss can affect anywhere from 30% to 50% of people with pneumococcal meningitis, 10% to 30% of those with Haemophilus influenzae type B meningitis, and 5% to 25% of those with meningococcal meningitis.
  • Younger Age: The same study reported that young age and the severity of symptoms were the only true predictors hearing loss in people with meningitis. From the age of two months, each month in a child's age at the time of diagnosis decreases the risk of hearing loss by 2% to 6%. Hearing loss is uncommon in older children, teens, and adults.
  • 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 presented with 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 likely to experience hearing loss than those who were treated within less than two days.
  • Certain Antibiotics: Antibiotics are vital to the treatment of bacterial meningitis, but aminoglycoside antibiotics like Gentak (gentamicin) and Nebcin (tobramycin) can actually cause hearing loss, especially in infants. They do so because by causing bacterial lysis, a process by which bacteria burst open and release inflammatory toxins harmful to the inner ear and auditory nerve.
  • 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.

Hearing loss is considered rare with viral meningitis, with a number of studies suggesting little to no risk. Fungal and parasitic meningitis are even less likely causes.

Why Hearing Loss Occurs

With meningitis, bacteria, cytokines (inflammatory compounds produced by the immune system), and bacteria toxins (triggered by the use of certain antibiotics) can infiltrate the inner ear and cause damage to not only nerve fibers but specialized cells in the cochlea known as hair cells.

There are both inner and outer hair cells. Outer hair cells are responsible for amplifying low-level sounds that enter the cochlea. Inner hair cells transform sound vibrations into electrical signals that are relayed to the brain via the auditory nerve. 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"), the condition of which 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 invariably permanent. Babies are at greater risk because the organs of their ears are still developing.

If a child experiences hearing loss after a bout of meningitis, there is a risk of cochlear ossification in the weeks and months that follow. Cochlear ossification is a complication of meningitis in which fluid in the cochlea is replaced by bone due to the extreme inflammation. This can make hearing loss worse and the treatment more difficult.

With that said, not all hearing loss is permanent. Children who have had meningitis can often develop a condition called glue ear in which the middle ear fills with a viscous fluid, causing the dulling of sounds.

In most cases, glue ear will resolve without treatment, although some children may require the insertion of ventilation tubes to help drain the ear if the condition persists.

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

Diagnosis

Hearing loss caused by meningitis is not usually detected until the damage has already been done. However, you shouldn't assume that the hearing loss is permanent until a proper medical evaluation has been performed.

If the hearing is impaired during or immediately following a bout of meningitis, the doctor will examine the ear with a lighted scope (called an otoscope) to see if there is any evidence of fluid in one or both ears. With glue ear, there should not be any pain but only the dulling of sounds (as if the cotton has been stuffed in the ear).

If the symptoms are severe, persistent, or worsening, an appointment with a hearing specialist, called an audiologist, would be scheduled. The audiologist can perform a battery of tests, including behavioral or auditory function tests, to characterize the extent of the hearing loss.

Audiologist Procedures

Behavioral tests are intended for babies and younger children but can also be used on older children with significant hearing loss. These include:

  • Behavioral Observation Audiometry (BOA): The doctor will observe how a baby (age 0 to 5 months) responds to sounds.
  • Visual Reinforcement Audiometry (VRA): The doctor will observe how a child (6 months to 2 years) physically moves or turns in response to sounds.
  • Conditioned Play Audiometry (CPA): A child (2 to 4 years) is asked to locate a sound or wait until they hear a sound before performing a play task (like 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 are those that involve devices that measure hearing sensitivity and how well organs of the ears are functioning. These include:

  • Pure-Tone Testing: You respond to sound transmitted to the ear via earphones
  • Bone Conduction Testing: You 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: A probe in your ear can measure how much your middle ear tightens in response to a loud sound.
  • Auditory Brainstem Response (ABR): Probes are placed on your head to measure brain wave activity in response to sound.

Auditory function tests can be used on adults and children, although sedation may be needed for children under six months to keep them still during certain tests, like the ABR.

The choice of tests depends largely on the patient's age. Tests like the OAE and ABR are especially useful in infants and toddlers who are too young to answer questions. Behavioral testing, an essential tool for young children, can also be valuable in older children and adolescents who have experienced significant hearing loss.

Different auditory tests have different purposes. Some, like bone conduction testing and OAE, can determine whether the impairment is in the middle or outer ear, while an ABR can identify if auditory nerve damage is the cause of the hearing loss.

Imaging tests, like magnetic resonance imaging (MRI) or computed tomography (CT), may also be ordered if cochlear ossification is suspected.

Based on the findings, the audiologist can better characterize the type of hearing loss and recommend the appropriate treatment.

Testing Recommendations

To ensure that hearing loss is not missed, infants and children with meningitis should be offered a hearing test as soon as they are well enough to do so (ideally within four weeks of the first appearance of bacterial meningitis symptoms).

Even though teens and adults are more likely to recognize a hearing loss if it occurs, testing may still be advised since some cases only manifest with symptoms months after the infection.

If hearing loss is detected, follow-up testing is recommended after 1, 2, 6, and 12 months after the initial tests to see if there is any improvement or deterioration. Imaging tests are only ordered if needed.

Although hearing loss can be confirmed in the initial round of testing, doctors cannot usually tell if the loss is permanent without routine follow-ups.

Treatment

While the main focus of treatment of bacterial meningitis is to resolve the underlying infection, efforts should also be made to reduce the risk of hearing loss. The key to this is the proper roll-out of medications, especially in babies and younger children.

Medications

Because all antibiotics have the potential for bacterial lysis and the production of bacterial toxins (some greater than others), corticosteroid drugs are often prescribed before antibiotics to reduce inflammation and the risk of inner-ear or auditory nerve injury.

Dexamethasone is the most commonly used corticosteroid, although hydrocortisone and prednisone are also sometimes used. The drugs may be delivered intravenously (into a vein) or by intratympanic injection (into the ear canal), typically 20 minutes before antibiotics are administered.

According to the 2015 Cochrane review of studies, corticosteroids reduce the rate of severe hearing loss from 9.3% to 6% and the rate of hearing impairment from 19% to 13.8%.

Among babies and children, studies have shown that only 3% of those treated with dexamethasone experienced hearing loss compared to 18% of those who were not.

Hearing Devices

Most hearing loss can be managed with hearing aids. These 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 a person's quality of life or ability to function normally, a cochlear implant may be considered. Not everyone is a candidate.

A cochlear implant is generally indicated for use in children who have sensorineural hearing loss in both ears (and only after trying a hearing aid for six months). The implants are indicated for adults who have sensorineural hearing loss in both ears and only hear 50% of words with a hearing aid.

in addition to hearing aids and cochlear implants, other supportive options include speech and language therapy and auditory-verbal therapy (in which deaf persons are taught to speak and listen with the hearing they have, often with the aid of hearing devices).

When to See a Doctor

Hearing loss may not be immediately obvious after meningitis. Because of this, you need to be on the lookout for signs of impairment, especially in smaller children and babies. Among some of the key signs:

  • 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 favor one ear when spoken to or turn 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 two. If they do not reach these milestones, hearing loss may be the cause.

As a general rule, anyone who has had bacterial meningitis should have a hearing test as soon as possible. All hearing losses are different and generally require repeat tests to get a qualified evaluation of one's hearing.

A Word From Verywell

One of the best ways to prevent hearing loss due to meningitis is to avoid meningitis in the first place. Today, there are vaccines that can help prevent two of the three most common types of bacterial meningitis.

According to the Centers for Disease Control and Prevention, all 11 to 12-year-olds should get a single dose of the meningococcal conjugate (MenACWY) vaccine along with a booster shot at age 16. Teens and young adults 16 through 23 may also get the serogroup B meningococcal (MenB) vaccine. If used as directed, the vaccines are between 85% and 100% effective.

If your child does get meningitis, ask your doctor for a referral to an audiologist who can conduct the necessary hearing tests, ideally within four weeks of the first appearance of symptoms.

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