Meningitis and Hearing Loss
Meningitis is an infection of the protective membranes (Meninges) that surround and protect brain and spinal cord. It is usually caused by bacterial or viral infection. This infection causes inflammation in meninges (protective membranes), which sometime results in damage of the nerves and brain.
Meningitis can affect anyone, of any age, at any time. However babies, toddlers and children under five year are the group most risk for meningitis, with young people aged 15-19 year the next most likely to suffer.
The ear, Hearing and Meningitis
Approximately one in ten children who survive meningitis develops some kind of hearing loss as a result of the illness. Tinnitus (ringing, hissing, buzzing or other noises in the ears and head) and other hearing problems is the most common after-effect of meningitis.
Sensorineural Hearing Loss
Sensorineural (on nerve) hearing loss is the most common kind of hearing loss which affects survivors of meningitis. Sensori-eural hearing loss is caused due to following:
1. Fault in hair cells
Sometime bacteria or bacterial toxins (meningococcal septicaemia) from infection may get into our inner ear where they can cause damage to the hair cells in cochlea (nerve fibres). Due to this damage, hair cells in cochlea stop working properly causing fault in the inner ear.
2. Fault in Auditory (hearing) nerve
Auditory (hearing) nerve, which carries sound signals to brain, stops working due to inflammation of the auditory nerve or if there is interruption of the blood supply to the cochlea or nerve cells.
Hearing loss due to above causes can range from mild through to profound and can affect one or both ears.
Conductive Hearing Loss
Conductive hearing loss happens when there is difficulty passing sound waves through outer ear, eardrums (tympanic membrane) or Middle ear (Ossicles). The most common reason for conductive deafness in children is build-up of fluid in the middle ear (known as glue ear) which makes it difficult for sound to pass through to the inner ear. Glue ear is usually temporary and often clears up on its own without needing any treatment. However, for some children glue ear may persist for longer term.
Meningitis can sometimes cause glue ear, but it is so common during childhood it is possible that a child may have a bout of it at some point and it may even be present when their hearing is first tested following the illness.
Ossification is the growth of excess bone in cochlea. There is a risk of ossification (even after weeks or months of recovery) if a child has hearing loss after meningitis. Ossification can make any existing hearing loss worse and treatment of the hearing loss more difficult or less successful. In children who need cochlear implants, ossification can make it more difficult to surgically insert the electrodes into the cochlea. This is one reason why it is so important for children to have their hearing tested, and problems treated as soon as possible after recovering from illness.
Hearing Loss Prevention
Many children have a reversible loss of hearing during the first two days of the illness. Early diagnosis and prompt treatment may be associated with a lower incidence of hearing loss. All children should have their hearing tested as soon as possible after bacterial meningitis.