Significant hearing loss affects around two out of 10 adults in Australia. Most of these people are over 60 and have lost their hearing gradually as part of the natural ageing process. However, hearing loss can also happen at a younger age.
Sound and the ear
Your ear consists of three parts: the outer ear, middle ear and inner ear.
The outer ear is the visible part of your ear. It collects sound waves, which travel down your ear canal to your eardrum. The sound waves cause your eardrum to vibrate. This vibration is passed on to your middle ear, which consists of three small bones called ossicles. The ossicles amplify and conduct the vibrations to your inner ear.
Your inner ear contains the cochlea and the auditory nerve. The cochlea is full of fluid and contains tiny hair cells. Vibrations cause the hair cells in your cochlea to move. Movement of these hair cells produces electrical signals that travel along the auditory nerve to your brain. There they are converted into meaningful information, such as language or music.
Types of hearing
There are two main types of hearing loss.
Conductive hearing loss – this is caused when sound can’t move freely from your outer ear to your inner ear.
Sensorineural hearing loss – this happens when there is damage to the pathway between your inner ear and your brain.
You may have a combination of conductive and sensorineural hearing loss – this is known as mixed hearing loss.
You may have hearing loss in one ear only (unilateral) or both ears (bilateral).
Symptoms of hearing loss
In adults, hearing loss may be very gradual, for example in age-related hearing loss. You may start to notice you find it difficult to hear and understand people when you're in a noisy place. Hearing loss can also be very sudden; for example, if it’s caused by a viral infection of the inner ear. Some people find that their hearing loss is associated with a continual ringing in their ears (tinnitus).
Depending on what is causing your hearing loss, you may also have some other symptoms, such as earache. If you have an infection, you may have discharge from your ears.
If you, or your friends and family, think that your hearing is getting gradually worse, you should see your GP. If you have sudden hearing loss in one or both ears, you should seek immediate advice, as treatment may need to be started very quickly.
Hearing loss can affect speech and language development in children.
Causes of hearing loss
Conductive hearing loss
The following are possible causes of conductive hearing loss.
Middle ear infection – this is particularly common in children.
Glue ear (a build-up of fluid in your middle ear) – this is also common in children.
Blockage of your outer ear – usually caused by a build-up of wax.
Otosclerosis – bone growth in the middle ear, which makes the ossicles of your middle ear harden and become less able to vibrate. This is a hereditary condition.
Perforated (pierced) eardrum – this can be caused by an untreated ear infection, a head injury or from poking something in your ear.
The causes of conductive hearing loss can often be treated, so it’s usually only temporary.
Sensorineural hearing loss
Most hearing loss is thought to be sensorineural. It happens when the hair cells within your cochlea are damaged. The following are some possible causes.
Age-related hearing loss (presbycusis) – a natural decline in your hearing as a result of damage that occurs to your cochlea as a part of the ageing process.
Congenital-related hearing loss – about 2 in a 1000 children born in Australia have a sensorineural hearing problem. Causes include inherited hearing loss, premature birth or other birth trauma, a viral infection such as measles affecting the unborn baby, and jaundice.
Regular exposure to loud noises – for example, if you work in a noisy place or listen to a lot of loud music.
Some infections – such as rubella, measles or meningitis.
Meniere's disease – a condition that affects your inner ear, causing dizziness and tinnitus, as well as leading to hearing loss.
Certain medicines – such as some strong antibiotics.
Certain cancer treatments – such as chemotherapy and radiotherapy.
Acoustic neuroma – a benign (non-cancerous) tumour that affects your auditory nerve.
Cholesteatoma – benign skin growth behind your eardrum.
An injury to your head.
Sensorineural hearing loss is usually permanent as once the hair cells in your cochlea are damaged, they can’t be repaired.
Diagnosis of hearing loss
Your GP will ask you about your symptoms and examine you. He or she may also ask you about your medical history.
Your GP may do a hearing test, or he or she may refer you to a specialist. This could be either an ear, nose and throat (ENT) doctor (who specialises in ENT disorders) or an audiologist (a specialist in hearing).
You may have the following tests.
Pure tone audiometry. You will be asked to wear a set of headphones attached to a machine called an audiometer. The audiometer produces sounds of different volumes and frequencies, and you will be asked to indicate when you hear the sounds in the headphones. The level at which you can’t hear the sound of a certain frequency is known as your hearing threshold. This tests both your outer and inner ear hearing pathways. A small vibrator may also be placed on the mastoid bone behind the ear to specifically test the sensitivity of your cochlea. This tests your inner ear hearing pathway only. The results of these two tests are shown as a graph called an audiogram. Together they can help your doctor locate where in the hearing pathway the problem might be occurring in addition to the degree of hearing loss you may be experiencing.
Speech discrimination test. This tests how clearly you hear speech rather than how loud it has to be for you to hear it. It requires that you repeat words that are said to you. The words may be said at different sound levels. In age-related hearing loss, the ‘p’, ‘f’ and ‘t’ sounds often sound similar due to hearing loss in the higher frequency ranges.
If your hearing loss has a sensorineural cause, a number of other tests can be done to pinpoint where the problem lies.
Otoacoustic emissions. This test measures your cochlear function by recording signals produced by the hair cells.
Electrocochleography. This test measures the electrical activity of the cochlea when a sound is heard.
Auditory brainstem response. This test measures the electrical activity of your brain when a sound is heard.
Tympanometry. This tests how well the middle ear system is functioning and how well the eardrum moves rather than testing hearing. However it can help establish if the hearing loss is due to a blockage and whether medical treatment can help clear it.
If your hearing loss is due to an abnormal growth in the ear, an MRI scan of your head may be required.
Treatment for hearing loss
You may find it easier to hear and understand people if you:
make sure there is light on the face of the person you’re talking to, so you can see their lips moving
sit close to the person you’re talking to
sit with your better ear closer to the person you’re talking to.
If you have a bacterial infection of your middle ear, it can sometimes be treated with antibiotics. Always ask your GP for advice and read the patient information leaflet that comes with your medicine.
If your outer or middle ears are blocked by ear wax or fluid, a nurse will be able to remove the blockage. Often they will use a syringe to clear it after the wax has been softened.
If there is no cure for your hearing loss, a hearing aid for one or both of your ears may help. Hearing aids can work for both conductive and sensorineural hearing loss. Many different are available and your audiologist will advise you on which type best suits your needs.
If you have a large perforation of your ear, you may need to have surgery to repair it.
An acoustic neuroma can be removed with surgery or treated with radiotherapy. Ossicles affected by otosclerosis can sometimes be treated with surgery.
If a hearing aid doesn’t help (for example, in profound deafness), your doctor may suggest you have a cochlear implant. This is a device that turns sounds into electrical signals, which directly stimulate your auditory nerve allowing you to hear.
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Last updated: 31 May 2013
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