Hearing loss is when your hearing worsens, as opposed to deafness, which is when hearing loss becomes total. Hearing loss can occur very gradually, as in age-related hearing loss, or it can be very sudden, as in some viral infections of the inner ear, or trauma.
The ear receives sounds from the environment and transmits them to the brain. It consists of three parts:
Two types of hearing loss occur, conductive and sensorineural, depending on which part of the ear is affected. Conductive hearing loss is caused by anything that blocks the conduction of sound from the outer through to the inner ear. As well as those mentioned below, causes include:
Sensorineural hearing loss refers to damage to the pathway for sound impulses from the hair cells of the inner ear to the auditory nerve and the brain. As well as those mentioned below, causes include:
If a pregnant woman has rubella, the fetus is at risk of being born deaf. For this reason, girls are vaccinated against rubella before child-bearing age. Some children are born deaf because of different problems with their development.
Hearing loss and deafness are symptoms of the disorders that cause them. Depending on the cause, they may be associated with other symptoms. For instance, disorders that involve the inner ear and auditory nerve often also cause dizziness and tinnitus (ringing or whistling sounds in the ear).
Many tests can be carried out to find the cause of hearing loss. A doctor or audiologist will first listen to the symptoms and perform a thorough examination of the nerves and ears. Tuning forks and a special electronic device with headphones (an audiometer) are used to test the degree of hearing loss and whether it is conductive or sensorineural. Other more complex tests may be carried out to check the function of the eardrum and ossicles.
If a sensorineural cause is suspected, the person may have tests called 'electrocochleography' and 'auditory brainstem responses', which measure the activity of the cochlea, auditory nerve and brain when a sound is heard. None of these tests are uncomfortable. If the cause of the hearing loss seems to be within the brain, the person may have a magnetic resonance imaging (MRI) scan of the brain.
The treatment of hearing loss depends on the cause. Infections are treated with antibiotics; blockages of the outer and middle ears can be manually cleared; damaged eardrums can be repaired surgically and otosclerosis can be treated effectively by replacement of the affected ossicles with tiny artificial bones. Some causes of sensorineural hearing loss can also be cured. For example, an acoustic neuroma (a benign tumour of the auditory nerve) can be removed surgically.
If there is no cure for the hearing loss (as with age-related hearing loss), a hearing aid usually helps most people, whether the hearing loss is conductive or sensorineural. Many different types of hearing aid are available and a doctor / audiologist will advise as to which type is best. Most people manage very well with a hearing aid and lead perfectly normal lives.
For profound deafness, a cochlear implant may help. This device transmits sound directly into the auditory nerve via an electrical wire implanted into the cochlea. Although the sounds heard are rather 'buzzing' or 'electronic', it can be very useful when used in combination with lip reading. It also lets a person hear the loudness of their own speech and so makes conversation easier. This is most important in deaf young children, as it helps them to develop good speech.
The outcome depends on the cause. It may be temporary as with glue ears in children, curable as with otosclerosis or incurable but manageable as with age-related hearing loss. Only very rarely is hearing loss caused by a more serious condition that affects the brain, such as a tumor.
Multiple sclerosis that affects auditory nerve pathways in the brain can cause sensorineural hearing loss.
Encephalitis can cause sensorineural hearing loss.
Meniere's disease can cause sensorineural hearing loss.
Rarely, rheumatoid arthritis affects the joints between the ossicles and can cause conductive hearing loss.
Deafness is unusual but has been reported.
According to one study, smoking or exposure to cigarette smoke can be linked to an increased risk of hearing loss. The study also suggests that non-smokers who live with smokers are almost twice as likely to have hearing loss as those not exposed to smoke at home.
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