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What is Deafness
Hearing loss may result from damage or disruption to any part of the hearing system from simple wax blocking the ear canals, through to age-related changes to the sensory cells of the cochlea, to damage to the brain.
Hearing loss can be mild, moderate, severe, or profound. People with mild hearing loss may find it hard to follow speech, particularly in noisy situations. Those with moderate deafness have difficulty following speech without a hearing aid. The severely deaf rely primarily on lip-reading, even with a hearing aid. Profoundly deaf people may communicate by lip-reading, and Sign Language may be their first or preferred language.
Hearing loss occurs primarily when the inner ear or auditory nerve is damaged or when sound waves cannot reach the inner ear. Untreated, hearing problems can get worse. Possible treatments include hearing aids, cochlear implants, special training, certain medicines, and surgery. According to the World Health Organization, half of all cases of deafness and hearing impairment are avoidable through prevention, early diagnoses, and management.
Three types of hearing loss
There are three different types of hearing loss:
1) Conductive hearing loss
This means that the vibrations are not passing through from the outer ear to the inner ear, specifically the cochlea. It can be due to an excessive build-up of earwax, glue ear, an ear infection with inflammation and fluid buildup, a perforated eardrum, or a malfunction of the ossicles (bones in the middle ear). Also, the eardrum may be defective.
Ear infections can leave scar tissue which damages the functioning of the ear drum.
The ossicles may be impaired due to infection, trauma, or their fusing together (ankylosis).
2) Sensorineural hearing loss
Hearing loss is caused by dysfunction of the inner ear, the cochlea, auditory nerve, or brain damage. Usually, this kind of hearing loss is due to damage of the hair cells in the cochlea. As humans get older, the hair cells lose some of their function, and our hearing gets worse. In Western Europe and North America it is estimated that over half of all people over 70 years of age have hearing impairment caused by degenerated hair cells in the cochlea.
Long-term exposure to loud noises, especially high frequency sounds, is another common reason for hair cell damage. Damaged hair cells cannot be replaced. Currently, research is looking into using stem cells to grow new ones.
Sensorineural total deafness may be due to birth defects, inner ear infections, or head trauma. If the ear drum and middle ear are functioning properly, patients may benefit from a cochlear implant – a thin electrode is inserted in the cochlea, it stimulates electricity through a tiny microprocessor which is placed under behind the ear, under the skin.
3) Mixed hearing loss
This is a combination of conductive and sensorineural hearing loss. Long-term ear infections can damage both the ear drum as well as the ossicles. Sometimes, surgical intervention may restore hearing, but it does not always work.
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.
What are the symptoms of hearing loss?
Symptoms of hearing loss include mild loss of high frequency hearing, hearing loss associated with ringing or noises (tinnitus), and complete deafness. Symptoms may develop gradually over time with many causes of hearing loss.
People who are experiencing hearing loss may refrain from taking part in conversations, may turn the volume up high on the radio or TV, and may frequently ask others to repeat what they have said.
Who is at Risk?
The Hearing Loss Association of America estimates one in three people older than 60 and half of those older than 85 have hearing loss.
According to the NIDCD, two to thee children out of every 1,000 in the United States are born deaf or hard-of-hearing; nine out of every 10 children born deaf are born to parents who can hear, and approximately 15 percent of Americans (26 million) between the ages of 20 and 69 have high frequency hearing loss due to exposure to loud sounds or noise at work or in leisure activities.
Hearing impairment in babies
The following signs may indicate a hearing problem (but not always):
- Before the age of four months, the baby does not turn his/her head towards a noise
- By the age of 12 months, the baby still does not utter a single word
- The baby does not appear to be startled by a loud noise
- The baby responds to you when he/she can see you, but much less so (or not at all) when you are out of sight and call out their name
- The baby seems to be aware of some sounds only
What is the treatment for hearing loss?
The treatment of hearing loss depends on its cause. For example:
- Ear wax can be removed
- Ear infection can be treated with medications
- Diseases that cause inflammation of the ear can be treated with medication
- Medications that are toxic to the ear can be avoided
- Occasionally surgical procedures are necessary