Deafness: Types, Symptoms, Causes & Treatments

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.