Meningitis is a serious condition that causes inflammation and swelling to important membranes surrounding the spinal cord and brain. Bacterial meningitis is among the most prevalent forms of this illness.
The symptoms of meningitis can vary in scope and degree; however, hearing loss is one of the more surprising sequelae symptoms of meningitis.
It is one of the leading causes of acquired deafness among children who’ve survived bacterial meningitis. In this article, we explore the connections between meningitis and hearing loss a bit closer.
What Is Meningitis?
Meningitis, or meningococcal disease, is a serious condition affecting meninges.
The meninges are protective membranes that cover the brain and spinal cord.
This devastating disease has a high fatality rate worldwide and has long-term complications.
According to the World Health Organization, one in 10 people who get bacterial meningitis die, whereas one in five is left with serious complications.
Thanks to the vaccination prevalence, the numbers are much lower in the United States.
There are only around 2,600 sporadic cases of bacterial meningitis reported each year. Of those cases, roughly 70 percent occur in children under five. Children under the age of two are at the highest risk.
There are different types of meningitis, including viral meningitis, fungal meningitis, parasitic meningitis, amebic meningitis, and non-infectious meningitis.
However, regarding hearing impairment and meningitis, our focus will be on the most serious form: bacterial meningitis.
What Causes Bacterial Meningitis?
Bacterial meningitis is among the most serious of all the different forms of meningitis.
It has a high mortality rate and can leave survivors permanently disabled. Some of these permanent disabilities include learning disabilities, neurological issues, and hearing loss.
Several different bacteria can cause meningitis. According to the Centers for Disease Control and Prevention (CDC), some of the most common bacteria that cause meningitis in the United States include:
- Streptococcus pneumoniae
- Haemophilus influenzae type B
- Neisseria meningitidis
- Group B Streptococcus
- Escherichia coli (E. coli)
- Listeria monocytogenes
- Mycobacterium tuberculosis (least common)
Age is one of the biggest risk factors for contracting bacterial meningitis. Due to their lack of immunity, infants are at the highest risk for developing bacterial meningitis.
But, this illness can affect anyone at any age. However, certain age groups are more susceptible to certain bacterial strains.
- Newborn infants – Infants are more susceptible to bacterial meningitis from Group B Streptococcus, S. pneumoniae, L. monocytogenes, and E. coli.
- Babies and young children – Young children are more susceptible to bacterial meningitis from Group B Streptococcus, S. pneumoniae, N. meningitidis, H. influenzae, and M. tuberculosis.
- Teenagers and young adults – Teens are more susceptible to bacterial meningitis from S. pneumoniae and N. meningitidis.
- Older adults – Adults are more susceptible to bacterial meningitis from Group B Streptococcus, L. monocytogenes, S. pneumoniae, N. meningitidis, and H. influenzae.
Aside from age, other risk factors and predictors of bacterial meningitis include travel, working around meningococcal pathogens, large group settings (college campuses), and surgical procedures.
High protein levels in the cerebrospinal fluid (CSF) and low glucose can also raise the risk of meningitis.
Bacterial meningitis can spread through contaminated food, but the most common way to spread the disease is from person to person.
What Are the Symptoms of Bacterial Meningitis?
The incubation period for bacterial meningitis can range from two to 10 days. Some common signs and symptoms of bacterial meningitis include:
- A stiff or painful neck
- Drowsiness or confusion
- Severe headaches
- Joint pain
- High fever
Meningitis and Hearing Loss: The Research
Hearing loss is a common after-effect strongly linked to childhood bacterial meningitis (pneumococcal meningitis).
According to one JAMA Otolaryngology Head & Neck Surgery study, of 432 children with meningitis, 59 of them (13.7 percent) developed hearing loss.
Of those children, 78 percent displayed postmeningitic sensorineural hearing loss.
A 2010 meta-analysis review in Pediatrics stated that hearing loss affects roughly 30 to 50 percent of people with pneumococcal meningitis, around 10 to 30 percent of those with Haemophilus influenzae type B meningitis and about five to 25 percent of those with meningococcal meningitis.
A ten-year review by the British Journal of Audiology concluded with similar findings. According to the review, acute bacterial meningitis is a critical cause of acquired sensorineural hearing loss in children.
Diagnosing, Treating, and Preventing Meningitis
A doctor can diagnose meningitis through blood or cerebrospinal fluid (CSF) samples.
Treatment typically includes antibiotics. Vaccinations are the most effective way to prevent bacterial meningitis.
How Does Meningitis Cause Hearing Loss?
Hearing loss can have several causes, ranging from trauma to aging. In the case of meningitis, hearing loss occurs as a result of damage to the auditory system. The auditory system includes the outer, middle, inner ear, and auditory nerve.
- The outer ear – The visible part of the ear (pinna) helps gather sound waves and directs them to the ear canal and the eardrum.
- The middle ear – Housing the eardrum and ossicles (three small bones; malleus, incus, and stapes), the middle ear helps send sound vibrations to the inner ear.
- The inner ear – Composed of various fluid-filled semicircular canals, the inner ear receives sound vibrations and transmits them through the auditory nerve to be interpreted by the brain.
The inner ear also houses an important snail-shaped organ called the cochlea and tons of tiny sensory cells, known as hair cells. These two components play a vital role in hearing health.
Meningitis and the inner ear
In some cases, bacterial meningitis causes septicemia, which can trigger cell death (apoptosis) in the specialized cells in the inner ear and disrupt normal hearing.
In short, the bacterial toxins from meningitis and the inflammatory compounds that help ward off the illness cause labyrinthitis, and damage nerve fibers, the cochlea, and hair cells.
This can lead to tinnitus (ringing in the ears) and hearing loss.
Hearing loss from meningitis can vary in degree, from moderate hearing loss to profound hearing loss. In some cases, permanent hearing loss and deafness is possible. Also, hearing loss can be unilateral (in one ear) or bilateral.
Some hearing loss is temporary. For example, many children experience glue ear, a temporary dulling of sound. It is caused by fluid filling the middle ear.
Other effects of meningitis on hearing and balance
Meningitis also puts children at an increased risk for ossification, excess bone growth in the cochlea.
This can contribute to greater hearing loss and make interventions like cochlear implants much harder.
Also, since the auditory and vestibular systems are closely related, damage to the auditory system can affect balance.
How Is Hearing Loss Diagnosed?
Hearing loss is determined by a hearing care professional, like an audiologist or an ENT (ear, nose, throat) physician.
These professionals are trained to perform several hearing tests to determine the extent of hearing loss.
In addition to audiometry pure-tone tests to examine hearing sensitivity, other tests include auditory function tests and behavioral tests. These tests could include:
- Auditory brainstem response (ABR) – In this test, probes on the head measure how brain wave activity responds to sound.
- Otoacoustic emissions (OAE) – In this test, sounds are transmitted into the ear through small earphones, measuring how much reflects back.
- Acoustic reflex measures – This test measures how much the middle ear tightens in response to loud sounds.
- Behavioral observation audiometry (BOA) – This behavioral test is used to see how well infants respond to sound.
How Is Hearing Loss Treated?
During a meningitis infection, interventions like corticosteroids (like dexamethasone) are common to help mitigate inflammation and damage to the inner ear.
In most cases, sensorineural hearing loss caused by meningitis is treated with amplification devices like hearing aids.
More intense interventions like cochlear implants may restore some hearing function if hearing loss is severe.
In addition to these interventions, there are several support options for children to help manage hearing loss. These may include speech-language therapy, auditory-verbal therapy for deaf children, and more.
The Bottom Line
Meningitis can be a devastating condition that leaves individuals with permanent disabilities, such as hearing loss.
Prevention is the best first line of defense; this is where vaccinations come into play.
However, if you suspect meningitis, early treatment is key. If hearing loss is associated with meningitis, your healthcare provider will most likely provide you with a referral to visit an audiologist trained to diagnose hearing loss and can follow up with a treatment plan.
Check out the USA Rx Hearing Loss Blog for more information on hearing loss and treatment options.