The ear is our organ of hearing. At around 20 years of age, our hearing starts a gradual decline. Higher frequencies are usually the first to go. This age-related hearing loss is normal and doesn’t lead to total loss of hearing. Deafness can range from mild to profound and is caused by many different events including injury, disease and genetic defects.
There are various ways to categorise deafness. The two main types of deafness are conductive deafness and nerve deafness. Deafness at birth is known as congenital deafness, while deafness that occurs after birth is called adventitious deafness. The most common cause of adventitious deafness is noise, which accounts for over one quarter of people affected by hearing loss.
The ear is made up of three different parts, including:
- Outer ear - is the part you can see. Its shape helps to collect sound waves. A tube leads inward to the eardrum.
- Middle ear – is separated from the outer ear by the eardrum. The middle ear contains three tiny bones called the malleus (hammer bone), the incus (anvil bone) and the stapes (stirrup bone). These bones amplify the movement of the eardrum produced by sound waves. The Eustachian tube attaches the middle ear to the back of the throat and helps to equalise air pressure.
- Inner ear - sound waves are picked up by a little spiral-shaped organ called the cochlear. Hairs on the cochlear sense the vibration and pass the message - interpreted into electrical impulses - on to the brain via the cochlear nerve.
Conductive deafness is caused by the failure of the three tiny bones inside the middle ear to pass along sound waves to the inner ear. Another common cause of conductive deafness is the failure of the eardrum to vibrate in response to sound waves. A build-up of fluid in the ear canal, for example, could dampen the movement of the eardrum. In many cases, treatment is available for conductive deafness and normal hearing will return.
Nerve deafness is caused by disease, trauma or some other disruptive event targeting the cochlear nerve. The rest of the ear - including the tiny bones and eardrum - may be working, but the electrical impulses aren’t able to reach the brain. In other cases, the problem is in the brain itself, which can’t ‘translate’ the messages from the cochlear nerve. Most cases of nerve deafness don’t respond to treatment.
Causes of temporary deafness
Some of the causes of temporary deafness include:
- Wax - the ear canal secretes cerumen, a waxy substance that helps to protect and lubricate the tissues. A build-up of wax can block the ear canal, leading to short-term conductive deafness.
- Foreign object - similarly to ear wax, a foreign object stuck inside the ear canal (such as the tip of a cotton bud) can temporarily cause hearing loss.
- Excess mucus - the common cold, a bout of flu, hay fever or other allergies can cause an excess of mucus that may block the Eustachian tubes of the ear.
- Ear infections - including otitis externa (infection of the outer ear) and otitis media (infection of the middle ear). Fluid and pus don’t allow the full conduction of sound.
- Drugs - certain drugs, including aminoglycosides and chloroquine, can cause temporary deafness in susceptible people.
Causes of hearing loss
Some of the many causes of deafness include:
- Hereditary disorders - some types of deafness are hereditary, which means parents pass on flawed genes to their children. In most cases, hereditary deafness is caused by malformations of the inner ear.
- Genetic disorders - genetic mutations may happen: for example, at the moment of conception when the father’s sperm joins with the mother’s egg. Some of the many genetic disorders that can cause deafness include osteogenesis imperfecta, Trisomy 13 S and multiple lentigines syndrome.
- Prenatal exposure to disease - a baby will be born deaf or with hearing problems if they are exposed to certain diseases in utero, including rubella (German measles), influenza and mumps. Other factors that are thought to cause congenital deafness include exposure to methyl mercury and drugs such as quinine.
- Noise - loud noises (such as gun shots, firecrackers, explosions and rock concerts), particularly prolonged exposure either in the workplace or recreationally, can damage the delicate mechanisms inside the ear. If you are standing next to someone, yet have to shout to be heard, you can be sure that the noise is loud enough to be damaging your ears. You can protect your hearing by reducing your exposure to loud noise or wearing suitable protection such as ear muffs or ear plugs.
- Trauma - such as perforation of the eardrum, fractured skull or changes in air pressure (barotrauma).
- Disease - certain diseases can cause deafness, including meningitis, mumps, cytomegalovirus and chicken pox. A severe case of jaundice is also known to cause deafness.
- Other causes - other causes of deafness include Meniere’s disease and exposure to certain chemicals.
Age-related hearing loss
Our hearing gradually becomes less acute as we age. This is normal, and rarely leads to deafness. Age-related hearing loss (presbycusis) typically begins with the loss of higher frequencies, so that certain speech sounds - such as ‘s’, ‘f’ and ‘t’ - end up sounding very similar. This means the older person can hear, but not always understand. For example, the words ‘see’ and ‘tea’ might sound the same.
Tinnitus is often associated with deafness
Tinnitus means a sensation of ringing in the ears. Some of the causes of tinnitus include middle ear infections and damage to the ear from loud noises. Tinnitus may occur on its own, or in conjunction with hearing loss.
Where to get help
Things to remember
- Deafness can range from mild to profound and is caused by many different events including injury, disease and genetic defects.
- Deafness at birth is known as congenital deafness, while deafness that occurs after birth is called adventitious deafness.
- The most common cause of adventitious deafness is noise, which accounts for over one quarter of people affected by hearing loss.
- You can protect your hearing by reducing your exposure to loud noise or wearing suitable protection such as ear muffs or ear plugs.
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